Soon Heung Chang

Boiling heat transfer characteristics of nano-fluids with nano-particles suspended in water are studied using different volume concentrations of alumina nano-particles. Pool boiling heat transfer coefficients and phenomena of nano-fluids are compared with those of pure water, which are acquired on a smooth horizontal flat surface (roughness of a few tens nano-meters). The experimental results show that these nano-fluids have poor heat transfer performance compared to pure water in natural convection and nucleate boiling. On the other hand, CHF has been enhanced in not only horizontal but also vertical pool boiling. This is related to a change of surface characteristics by the deposition of nano-particles. In addition, comparisons between the heat transfer data and the Rhosenow correlation show that the correlation can potentially predict the performance with an appropriate modified liquid-surface combination factor and changed physical properties of the base liquid.

The wettability of the heated surface under pool boiling of surfactant solutions and nano-fluids has been investigated. Tri-sodium phosphate (TSP, Na3PO4) solutions (0.01, 0.05, 0.1, 0.3, 0.5, 0.8 wt.%) and Aluminum oxide (Al2O3) nano-fluids (NF) (0.5, 1, 2, 4 vol.%) were prepared for experiments. Stainless steel (SUS 304) strips (30 × 30 × 3 mm) were heated by an alcohol lamp and quenched in the prepared solutions. Before complete quenching, when the surface temperature was 150 ± 10 °C (nucleate boiling region), the strip was taken out and excessive liquid on the surface was removed. Contact angles of pure water and the solutions on the quenched surface and fresh surface were measured. Contact angles of pure water on the quenched surfaces (5°–25°) were much smaller than those on the fresh surface (65°–70°). The solutions (TSP, NF) on the quenched surface shows the smallest contact angle (5°–15°). Surfaces deposited TSP and nano-particle could affect surface energy of the strips and enhance hydrophilicity of the surfaces. Several implications of the experimental results on the pool boiling CHF model and CHF enhancement using TSP and NF were discussed.

Convolutional Neural Networks (CNNs) have dominated computer vision for years, due to its ability in capturing locality and translation invariance. Recently, many vision transformer architectures have been proposed and they show promising performance. A key component in vision transformers is the fully-connected self-attention which is more powerful than CNNs in modelling long range dependencies. However, since the current dense self-attention uses all image patches (tokens) to compute attention matrix, it may neglect locality of images patches and involve noisy tokens (e.g., clutter background and occlusion), leading to a slow training process and potential degradation of performance. To address these problems, we propose the k-NN attention for boosting vision transformers. Specifically, instead of involving all the tokens for attention matrix calculation, we only select the top-k similar tokens from the keys for each query to compute the attention map. The proposed k-NN attention naturally inherits the local bias of CNNs without introducing convolutional operations, as nearby tokens tend to be more similar than others. In addition, the k-NN attention allows for the exploration of long range correlation and at the same time filters out irrelevant tokens by choosing the most similar tokens from the entire image. Despite its simplicity, we verify, both theoretically and empirically, that k-NN attention is powerful in speeding up training and distilling noise from input tokens. Extensive experiments are conducted by using 11 different vision transformer architectures to verify that the proposed k-NN attention can work with any existing transformer architectures to improve its prediction performance. The codes are available at https://github.com/damo-cv/KVT .

Global concerns for the security of energy have steadily been on the increase and are expected to become a major issue over the next few decades. Urgent policy response is thus essential. However, little attempt has been made at defining both energy security and energy metrics. In this study, we provide such metrics and apply them to four major energy sources in the Korean electricity market: coal, oil, liquefied natural gas, and nuclear. In our approach, we measure the cost of energy security in terms of supply disruption and price volatility, and we consider the degree of concentration in energy supply and demand using the Hirschman–Herfindahl index (HHI). Due to its balanced fuel supply and demand, relatively stable price, and high abundance, we find nuclear energy to be the most competitive energy source in terms of energy security in the Korean electricity market. LNG, on the other hand, was found to have the highest cost in term of energy security due to its high concentration in supply and demand, and its high price volatility. In addition, in terms of cost, we find that economic security dominates supply security, and as such, it is the main factor in the total security cost. Within the confines of concern for global energy security, our study both broadens our understanding of energy security and enables a strategic approach in the portfolio management of energy consumption.

The effect of micro/nanoporous inside surface coated vertical tubes on CHF was determined during water flow boiling at atmospheric pressure. CHF was measured for smooth and three different coated tubes, at mass fluxes (100–300 kg/m2 s) and two inlet subcooling temperatures (50 °C and 75 °C). Greater CHF enhancement was found with microporous coatings than with nanoporous coatings. Al2O3 microporous coatings with particle size <10 μm and coatings thickness of 50 μm showed the best CHF enhancement. Maximum increase in CHF was about 25% for microporous Al2O3. A wettability test was performed to study an increase of CHF with microporous coated surfaces.

The critical heat flux (CHF) is one of the most important thermal hydraulic parameters in heat transfer system design and safety analyses. CHF enhancement allows higher limits of operation conditions such that heat transfer equipment can be operated safely with greater margins and better economy. The application of nano-fluids is thought to have strong potential for enhancing the CHF. In this study, zeta potentials of Al2O3 nano-fluids were measured and flow boiling CHF enhancement experiments using Al2O3 nano-fluids were conducted under atmospheric pressure. The CHFs of Al2O3 nano-fluids were enhanced up to ∼70% in flow boiling for all experimental conditions. Maximum CHF enhancement (70.24%) was shown at 0.01 vol% concentration, 50 °C inlet subcooling, and a mass flux of 100 kg/m2 s. Inner surfaces of the test section tube were observed by FE–SEM and the zeta potentials of Al2O3 nano-fluids were measured before and after the CHF experiments.

SiC nanofluid was used for critical heat flux (CHF) enhancement in the case of water pool boiling. Many kinds of nanofluid have been highlighted as a simple way to gain high thermal performance of fluids, and SiC is received attention these days as a promising material because of its relatively high thermal properties. In this study, SiC nanofluid was investigated to measure its thermal performance in water pool boiling experiment especially for CHF. The volume concentration of SiC nanofluid were 0.0001%, 0.001%, 0.01%. Several characteristic of SiC nanofluid, such as zeta potential, and contact angle which could be affect on thermal performance of the fluids had been measured. The experiments were conducted under atmospheric pressure. Two kinds of test sections with different dimensions were used for verifying CHF enhancement trends for SiC nanofluid. The CHF has been enhanced up to 105% for volume concentration 0.01%. CHF enhancement ratios of SiC nanoparticle deposited surfaces were well corresponded with the results of SiC nanofluid. CHF enhancement trend was interesting because it did not linearly dependent on nanoparticle concentration. The wettability change of SiC nanoparticle deposited surface was discussed as main reason of CHF enhancement variation.

We consider weakly-supervised video anomaly detection in this work. This task aims to learn to localize video frames containing anomaly events with only binary video-level annotation, <i>i.e.</i>, anomaly vs. normal. Traditional approaches usually formulate it as a multiple instance learning problem, which ignore the intrinsic data imbalance issue that positive samples are very scarce compared to negative ones. In this paper, we focus on addressing this issue to boost detection performance further. We develop a new light-weight anomaly detection model that fully utilizes enough normal videos to train a classifier with a good discriminative ability for normal videos, and we employ it to improve the selectivity for anomalous segments and filter out normal segments. Specifically, in addition to boosting anomalous prediction, a novel contrastive attention module additionally produces a converted normal feature from anomalous video to refined anomalous predictions by maximizing the classifier making a mistake. Moreover, to remove the stubborn normal segments selected by the attention module, we also design an attention consistency loss to employ the classifier with high confidence for normal features to guide the attention module. Extensive experiments on two large-scale datasets, UCF-Crime, ShanghaiTech and XD-Violence, clearly demonstrate that our model largely improves frame-level AUC over the state-of-the-art. Code is released at <uri>https://github.com/changsn/Contrastive-Attention-for-Video-Anomaly-Detection</uri>.

Alternative splicing of the P/Q-type channel (Ca(V)2.1) promises customization of the computational repertoire of neurons. Here we report that concerted splicing of its main alpha1A subunit, at both an EF-hand-like domain and the channel C terminus, controls the form of Ca2+-dependent facilitation (CDF), an activity-dependent enhancement of channel opening that is triggered by calmodulin. In recombinant channels, such alternative splicing switches CDF among three modes: (1) completely "ON" and driven by local Ca2+ influx through individual channels, (2) completely "OFF," and (3) partially OFF but inducible by elevated global Ca2+ influx. Conversion from modes 1 to 3 represents an unprecedented dimension of control. The physiological function of these variants is likely important, because we find that the distribution of EF-hand splice variants is strikingly heterogeneous in the human brain, varying both across regions and during development.

As one of the promising energy sources for the next few decades, nuclear energy receives more attention than before as environmental issues become more important and the supply of fossil fuels becomes unstable. One of the reasons for this attention is based on the rapid innovation of nuclear technology which solves many of its technological constraints and safety issues. However, regardless of these rapid innovations, social acceptance for nuclear energy has been relatively low and unchanged. Consequently, the social perception has often been an obstacle to the development and execution of nuclear policy requiring enormous subsidies which are not based on the social value of nuclear energy. Therefore, in this study, we estimate the social value of nuclear energy-consumers’ willingness-to-pay for nuclear energy—using the Contingent Valuation Method (CVM) and suggest that the social value of nuclear energy increases approximately 68.5% with the provision of adequate information about nuclear energy to the public. Consequently, we suggest that the social acceptance management in nuclear policy development is important along with nuclear technology innovation.

This study describes flow boiling critical heat flux (CHF) experiments using Al2O3 nanofluid and Al2O3 nanoparticle deposited tubes. The flow boiling CHF of Al2O3 nanofluid with a plain tube (NFPT) and de-ionized water with an Al2O3 nanoparticle deposited tube (DWNT) were enhanced up to about 80% for all experimental conditions. There was no big difference in the CHF results between NFPT and DWNT; these results indicate that the CHF enhancement of Al2O3 nanofluid is surely caused by deposition of nanoparticles on the test section tube inner surface. After the flow boiling CHF experiments, the inner surfaces of the test section tube were explored by FE-SEM, which revealed the deposition of Al2O3 nanoparticles on the heated surfaces.

Amphiphilic poly(ethylene glycol)-imino-poly(benzyl-l-aspartate) (PIPA) and poly(ethylene glycol)-poly(benzyl-l-aspartate) (PPA) block copolymers were synthesized as pH-responsive and pH-nonresponsive copolymers, respectively. Polymer micelles were fabricated by the film dispersion method, and hydroxycamptothecin (HCPT) was physically encapsulated into the micelles. The average diameter of the HCPT-loaded PIPA micelles (PIPAH micelles) was approximately 230 nm, which was slightly smaller than that of the HCPT-loaded PPA micelles (PPAH micelles, approximately 260 nm). The drug-loading content and encapsulation efficiency of the PIPAH micelles (3.33% and 68.89%, respectively) were slightly higher than those of the PPAH micelles (2.90% and 59.68%, respectively). The PIPAH micelles exhibited better colloid stability, storage stability, and plasma stability than the PPAH micelles. Drug release from the PIPAH micelles with imino groups was pH dependent, and more than 75% or 65% of the loaded HCPT was released within 24 h in weakly acidic media (pH 5.0 or 6.0, respectively). An in vitro cell assay demonstrated that the pH-sensitive micelles exhibited potent suppression of cancer cell proliferation and little cytotoxicity on normal cells. Additionally, these micelles could be efficiently internalized by the tumor cells through macropinocytosis- and caveolin-mediated endocytotic pathways. HCPT-loaded micelles had longer circulation time than the HCPT solution in a pharmacokinetic study. In vivo antitumor experiments indicate that the PIPAH micelles had better antitumor efficacy than the pH-insensitive PPAH micelles and the HCPT solution. Therefore, the pH-responsive PIPAH micelles have great potential for high-efficiency delivery of HCPT. In this study, a new type of pH-responsive amphiphilic copolymer, poly(ethylene glycol)-imino-poly(benzyl-l-aspartate) (PIPA) block copolymer, was synthesized. This copolymer had then self-assembled to form nanomicelles for tumor intracellular delivery of hydroxycamptothecin (HCPT) for the first time. In in vitro test, the PIPAH micelles exhibited adequate stability and pH-dependent drug release. To one's excitement, the PIPAH micelles exhibited better antitumor efficacy and biosafety than the pH-insensitive micelles (PPAH) and the HCPT solution in in vitro and in vivo antitumor experiments. Therefore, the pH-responsive micelles in this study have significant potential to be used for high-performance delivery of HCPT and potentially for the targeted delivery of other cancer therapeutic agents. The polymer designed in this study can be used as a carrier of poorly soluble drugs or other active ingredients.

Temporal action proposal generation (TAPG) is a fundamental and challenging task in media interpretation and video understanding, especially in temporal action detection. Most previous works focus on capturing the local temporal context and can well locate simple action instances with clean frames and clear boundaries. However, they generally fail in complicated scenarios where interested actions involve irrelevant frames and background clutters, and the local temporal context becomes less effective. To deal with these problems, we present an augmented transformer with adaptive graph network (ATAG) to exploit both long-range and local temporal contexts for TAPG. Specifically, we enhance the vanilla transformer by equipping a snippet actionness loss and a front block, dubbed augmented transformer, and it improves the abilities of capturing long-range dependencies and learning robust feature for noisy action instances. Moreover, an adaptive graph convolutional network (GCN) is proposed to build local temporal context by mining the position information and difference between adjacent features. The features from the two modules carry rich semantic information of the video, and are fused for effective sequential proposal generation. Extensive experiments are conducted on two challenging datasets, THUMOS14 and ActivityNet1.3, and the results demonstrate that our method outperforms state-of-the-art TAPG methods. Our code will be released soon.

In pressurized water reactors, the fuel reloading problem has significant meaning in terms of both safety and economics. The local power peaking factor must be kept lower than a predetermined value during a cycle, and the effective multiplication factor must be maximized to extract the maximum energy. If these core parameters could be obtained in a very short time, the optimal fuel reloading patterns would be found more effectively and quickly. A very fast core parameter prediction system is developed using the backpropagation neural network. This system predicts the core parameters several hundred times as fast as the reference numerical code, within an error of a few percent. The effects of the variation of the training rate coefficients, the momentum, and the hidden layer units are also discussed.

This study investigated the pool boiling critical heat flux (CHF) of water-based nano-fluids under atmospheric pressure for Invessel Retention (IR)–External Vessel Cooling (EVC). The heated surface was a stainless steel foil inclined at different orientation angle from 0° (horizontal downward facing position) to 90° (vertical position). Three working nano-fluids with high suspension stability were selected by the zeta potential method to investigate the effect of each nano-fluid on CHF at the heated surface, which were 0.05% Alumine (Al2O3), 0.05% carbon nanotubes (CNT) + 10% boric acid and 0.05% Al2O3 + 0.05% CNT. It was observed that these nano-fluids enhanced CHF significantly (up to 220%) compared to deionized (DI) water. Furthermore, for all test fluids, CHF increased when the orientation angle increased. The surface characterization after boiling tests shows that the CHF enhancement with nano-fluids can be related to the increase of both surface roughness and wettability caused by nanoparticle deposition during the boiling processes.

Two-phase flow excursion instability especially for a downward flow in a narrow rectangular channel heated on both sides was experimentally investigated. Three test channels with different gap sizes (2.5, 3.3 and 4.1 mm) for the same channel width (40 mm), the heated width (30 mm) and the length (350 mm) were adopted for the experiment. For several imposed heat flux values (ranging 0–1000 kW m−2) and inlet subcooling temperature (43–75 K), subcooled flow boiling was investigated while reducing the fluid mass flux starting from a sufficient high-mass-flux condition up to the flow excursion point when vigorous boiling occurs. The minimum mass flux conditions in which a stable flow is sustainable were identified via 47 flow instability data points and were compared with relevant correlations. The results implied flow excursion points that were close to the onset of a significant void. The visualization of the flow excursion using a high-speed camera was achieved, clearly demonstrating that the flow excursion is triggered by the coalescence of facing bubbles (for Pe < 14000) or wavy vapors (for Pe > 14000) on opposing heated surfaces. Deviation from a prediction of earlier correlations with the present data was revealed, and new empirical correlations that reflect the gap size effect which predicts our data with fairly good accuracy are suggested.

The design concept of integrated passive safety system (IPSS) which can perform various passive safety functions is proposed in this paper. It has the various functions of passive decay heat removal system, passive safety injection system, passive containment cooling system, passive in-vessel retention and cavity flooding system, and filtered venting system with containment pressure control. The objectives of this paper are to propose the conceptual design of an IPSS and to estimate the design characters of the IPSS with accident simulations using MARS code. Some functions of the IPSS are newly proposed and the other functions are reviewed with the integration of the functions. Consequently, all of the functions are modified and integrated for simplicity of the design in preparation for beyond design based accidents (BDBAs) focused on a station black out (SBO). The simulation results with the IPSS show that the decay heat can be sufficiently removed in accidents that occur with a SBO. Also, the molten core can be retained in a vessel via the passive in-vessel retention strategy of the IPSS. The actual application potential of the IPSS is high, as numerous strong design characters are evaluated. The installation of the IPSS into the original design of a nuclear power plant requires minimal design change using the current penetrations of the containment. The functions are integrated in one or two large tanks outside the containment. Furthermore, the operation time of the IPSS can be increased by refilling coolant from the containment outside into integrated passive safety tanks (IPSTs). The coolant in the IPSTs is used for various functions in accident scenarios. Also, potential problems for the realistic installation of the IPSS are proposed and the solutions to these problems are schematically described. IPSS is the design for the passive safety enhancement in preparation for a loss of AC power. Consequently, it is designed for the supplementation and enhancement of current nuclear power plants, not as a replacement. The specific optimization design for each current or future reactor will be studied as further works.

Genetic programming (GP) involves finding both the functional form and the numeric coefficients for the model. So it does not require the assumption of any functional relationship between dependent and independent variables. The use of GP for solving long-term forecasting of the electric power demand problem is discussed; several cases which have different combinations of terminal sets and functional sets were investigated. The results of annual forecasting of electric power demand are presented for various cases using the GP model. The GP model is compared with the regression model.

The nuclear power plant has to be operated with sufficient margin from the specified DNBR limit for assuring its safety. The digital core protection system calculates on-line real-time DNBR by using a complex subchannel analysis program, and triggers a reliable reactor shutdown if the calculated DNBR approaches the specified limit. However, it takes a relatively long calculation time even for a steady state condition, which may have an adverse effect on the operation flexibility. To overcome the drawback, a new method using a radial basis function network is presented in this paper. Nonparametric training approach is utilized, which shows dramatic reduction of the training time, no tedious heuristic process for optimizing parameters, and no local minima problem during the training. The test results show that the predicted DNBR is within about ±2% deviation from the target DNBR for the fixed axial flux shape case. For the variable axial flux case including severely skewed shapes that appeared during accidents, the deviation is within about ±10%. The suggested method could be the alternative that can calculate DNBR very quickly while guaranteeing the plant safety.

The Optimal Fuel Shuffling System (OFSS) was developed for the optimal design of pressurized water reactor (PWR) fuel loading patterns. An optimal loading pattern is defined in which the local power peaking factor is lower than a predetermined value during one cycle and the effective multiplication factor is maximized to extract the maximum energy. The OFSS is a hybrid system in which a rule-based system, fuzzy logic, and an artificial neural network (ANN) are connected with each other. The rule-based system classifies loading patterns into two types by using several heuristic rules and a fuzzy rule. The fuzzy rule is introduced to achieve a more effective and faster search. Its membership function is automatically updated in accordance with the prediction results. The ANN predicts core parameters for the patterns generated from the rule-based system. A backpropagation network is used for fast prediction of the core parameters. The ANN and fuzzy logic can be used to improve the capabilities of existing algorithms. The OFSS was demonstrated and validated for cycle 1 of the Kori-1 PWR.

P-type (Ca V 2.1) Ca 2+ channels are a central conduit of neuronal Ca 2+ entry, so their Ca 2+ feedback regulation promises widespread neurobiological impact. Heterologous expression of recombinant Ca V 2.1 channels demonstrates that the Ca 2+ sensor calmodulin can trigger Ca 2+ -dependent facilitation (CDF) of channel opening. This facilitation occurs when local Ca 2+ influx through individual channels selectively activates the C-terminal lobe of calmodulin. In neurons, however, such calmodulin-mediated processes have yet to be detected, and CDF of native P-type current has thus far appeared different, arguably triggered by other Ca 2+ sensing molecules. Here, in cerebellar Purkinje somata abundant with prototypic P-type channels, we find that the C-terminal lobe of calmodulin does produce CDF, and such facilitation augments Ca 2+ entry during stimulation by repetitive action-potential and complex-spike waveforms. Beyond recapitulating key features of recombinant channels, these neurons exhibit an additional modulatory dimension: developmental upregulation of CDF during postnatal week 2. This phenomenon reflects increasing somatic expression of Ca V 2.1 splice variants that manifest CDF and progressive dendritic targeting of variants lacking CDF. Calmodulin-triggered facilitation is thus fundamental to native Ca V 2.1 and rapidly enhanced during early development.

A digital photographic study of subcooled flow boiling with R-134a was performed in a vertical rectangular channel heated from one side to observe near-wall structures. Primary attention was given to bubble formation and bubble coalescence in the bubble layer. The visualization made possible a detailed observation of the characteristic near-wall region, consisting of vapor remnants, an interleaved liquid layer, and coalesced adjacent bubbles. In particular, the visualization provided clearer insights about bubble coalescence behaviors during flow nucleate boiling. In addition, it is shown that the near-wall bubble layer of nucleate boiling beneath vapor clots is extinguished and, afterwards, the heated surface is locally covered by large vapor films, at CHF.

The critical heat flux (CHF) on the reactor vessel outer wall was measured using the two-dimensional slice test section. The radius and the channel area of the test section were 2.5 m and 10 cm × 15 cm, respectively. The flow channel area and the heater width were smaller than those of the ULPU experiments, but the radius was greater than that of the ULPU. The CHF data under the inlet subcooling of 2 to 25°C and the mass flux 0 to 300 kg/m2·s had been acquired. The measured CHF value was generally slightly lower than that of the ULPU. The difference possibly comes from the difference of the test section material and the thickness. However, the general trend of CHF according to the mass flux was similar with that of the ULPU. The experimental CHF data were compared with the predicted values by SULTAN correlation. The SULTAN correlation predicted well this study’s data only for the mass flux higher than 200 kg/m2·s, and for the exit quality lower than 0.05. The local condition-based correlation was developed, and it showed good prediction capability for broad quality (-0.01 to 0.5) and mass flux (<300 kg/m2·s) conditions with a root-mean-square error of 2.4%. There were increases in the CHF with trisodium phosphate-added water.

In this study, the CHF enhancement using various mixing vanes is evaluated and the flow characteristics are investigated through the CHF experiments and CFD analysis. CHF tests were performed using 2 × 2 and 2 × 3 rod bundles and with R-134a as the working fluid. The test section geometry was identical to that of commercial PWR fuel assembly not including the heated length (1.125 m) and number of fuel rods. From the CHF tests, it was found that the CHF enhancement using mixing vanes under higher mass flux (1400 kg/m2 s) and lower pressure (15 bar) conditions is larger than the CHF enhancements under other conditions. Among the mixing vanes used in this study, the swirl vane showed the best performance under relatively low pressure (15 bar) and mass flux (300–1000 kg/m2 s) conditions and the hybrid vane performed best near the PWR operating conditions. The detailed flow characteristics were also investigated by CFD analysis using the same conditions as the CHF tests. To calculate the subcooled boiling flow, the wall partitioning model was applied to the wall boundary and various two-phase parameters were also considered. The reliability of the CFD analysis in the boiling analysis was confirmed by comparing the average void fractions of the analysis and the experiments: the results agreed well. From the CFD analysis, the void fraction flattening as a result of the lateral velocity induced by the mixing vane was observed. By the lateral motion of the liquid, the void fraction in the near wall was decreased and that of the core region was increased resulting in the void fraction flattening. The decrease of the void fraction in the near wall region promoted liquid supply to the wall and consequently the CHF increased. For the quantification of the void flatness, an index was developed and the applicability of the index in the CHF assessment was confirmed.

In this study, pool boiling CHF experiments under atmospheric pressure with SA508 test heater was performed. SA508 is the material of the reactor pressure vessel in a nuclear power plant. Therefore, the CHF behavior of SA508 material is important for the reactor pressure vessel integrity at accident, but there are few studies about that. SA508 material showed very different CHF behavior from other cases (stainless steel). It showed very higher CHF value and the test heater surface was changed significantly. This test heater surface change is due to corrosion of SA508, and the rate of corrosion increases with boiling time. The corrosion product is analyzed as magnetite (Fe3O4), and magnetite has been used as one of nanofluid for CHF enhancement. The size of magnetite produced on the test heater surface is 20–140 nm, that is, it is nanoscale. Therefore, the CHF enhancement mechanism of SA508 material is similar to the case using other test heater (like stainless steel) with magnetite nanofluid. Additives like TSP, Al2O3 and CNT nanoparticles are also tested, but they did not show the CHF enhancement effect. In case of TSP, it showed CHF decrease effect due to preventing effect on SA508 corrosion.

The concept and assessment approach of nuclear safety in nuclear power plants (NPPs) have been evolved with the technological progress and the lessons learned from the major events. Recently, studies on the integrated approach of deterministic and probabilistic method have been done. In this study, a combined deterministic and probabilistic procedure (CDPP) is proposed for safety assessment of the beyond design basis accidents (BDBAs). In the CDPP, the conditional exceedance probability obtained by the best estimate plus uncertainty method acts as go-between deterministic and probabilistic safety assessments, resulting in more reliable values of core damage frequency and conditional core damage probability. To verify applicability of the methodology, performance of the APR-1400 emergency core cooling system is assessed against large break loss of coolant accident (LOCA), under the premise that LOCAs for any breaks larger than transition break size would be regarded as BDBA. In addition, discussions are made for analysis results for allowable NPP changes of emergency diesel generator start time extension and power uprating. It is concluded that the proposed CDPP is applicable to safety assessment of BDBAs in NPPs without significant erosion of the safety margin.

Since the variation pattern of load during holidays is different than that of non-holidays, forecasting holiday load is a challenging task. With a focus on this problem, we propose a learning framework based on weighted knowledge transfer for daily peak load forecasting during holidays. First, we select source cities which can provide extra hidden knowledge to improve the forecast accuracy of the load of the target city. Then, all the instances which are from source cities and the target city will be weighted and trained by the improved weighted transfer learning algorithm which is based on the TrAdaBoost algorithm and can decrease negative transfer. We evaluate our method with the classical support vector machine method and a method based on knowledge transfer on a real data set, which includes eleven cities from Guangdong province to illustrate the performance of the method. To solve the problem of limited historical holiday load data, we transfer the data from nearby cities based on the fact that nearby cities in Guangdong province have a similar economic development level and similar load variation pattern. The results of comparative experiments show that the forecasting framework proposed by this paper outperforms these methods in terms of mean absolute percent error and mean absolute scaled error.

The toxicity and side effects of traditional chemotherapeutic drugs are the main causes of chemotherapy failure. To improve the specificity and selectivity of chemotherapeutic drugs for tumor cells, a novel redox-sensitive polymer prodrug, polyethylene glycol-poly (β-benzyl-L-aspartate) (PEG-PBLA)-SS-paclitaxel (PPSP), was designed and synthesized in this study. PPSP was synthesized successfully and PPSP micelle was manufactured via high-speed dispersion stirring and dialysis. The inhibitory effect of PPSP on HepG2、MCF-7 and HL-7702 cell proliferation was investigated with MTT assays. The particle size and zeta potential of this prodrug micelle were 63.77±0.91 nm and -25.8±3.24 mV, respectively. The micelles were uniformly distributed and presented a spherical morphology under a transmission electron microscope. In the tumor physiological environment, the particle size of the PPSP micelles and the release rate of paclitaxel (PTX) were significantly increased compared with those of mPEG-PBLA-CC-PTX (PPCP) micelles, reflecting the excellent redox-sensitive activity of the PPSP micelles. In vitro cell assay demonstrated that PPSP is superior to PTX with respect to the inhibition of two tumor cells and has low toxicity against non-cancerous HL 7702 cells. Moreover, the blank micelle from mPEG-PBLA showed no obvious toxicity to the two tumor cells at different experimental concentrations. In summary, the redox-sensitive PPSP micelle significantly would improve the tumor targeting and anti-tumor activity of PTX and be thus a potential substitute for paclitaxel injection.

A new correction method is developed for the effect of the length-to-diameter (L/D) ratio on critical heat flux (CHF) by applying artificial neural networks and conventional regression techniques to the KAIST CHF data base for water flow in uniformly-heated, vertical round tubes. It consists of two parts: (a) a threshold L/D over which the length effect becomes negligible; and (b) a L/D correction factor for channels with L/D less than the threshold L/D. The proposed correction method is validated with the experimental data in the original database and a new data set obtained from the KAIST intermediate pressure loop. The proposed method will be useful in the following applications: (a) to predict the CHF for short tubes using CHF models which are based on the data for sufficiently long channels; (b) to define the experimental data which can be used for development of local-condition type CHF correlations; and (c) to convert the CHF data from short channels into CHF data for standard long channels for utilization in correlation development.

Parametric trends of the critical heat flux (CHF) are analyzed by applying artificial neural networks (ANNs) to a CHF data base for upward flow of water in uniformly heated vertical round tubes. The analyses are performed from three viewpoints, i.e., for fixed inlet conditions, for fixed exit conditions, and based on local conditions hypothesis. Katto's and Groeneveld et al. dimensionless parameters are used to train the ANNs with the experimental CHF data. The trained ANNs predict the CHF better than any other conventional correlations, showing RMS errors of 8.9%, 13.1% and 19.3% for fixed inlet conditions, for fixed exit conditions, and for local conditions hypothesis, respectively. The parametric trends of the CHF obtained from those trained ANNs show a general agreement with previous understanding. In addition, this study provides more comprehensive information and indicates interesting points for the effects of the tube diameter, the heated length, and the mass flux. It is expected that better understanding of the parametric trends is feasible with an extended data base.

An experimental study on critical heat flux (CHF) has been performed for water flow in vertical round tubes under low pressure and low flow (LPLF) conditions to provide a systematic data base and to investigate parametric trends. Totally 513 experimental data have been obtained with Inconel-625 tube test sections in the following conditions: diameter of 6, 8, 10 and 12 mm; heated length of 0.3∼1.77 m; pressure of 106∼951 kPa; mass flux of 20∼277 kg m−2 s−1; and inlet subcooling of 50∼654 kJ kg−1, thermodynamic equilibrium critical quality of 0.323∼1.251 and CHF of 108∼1598 kW m−2. Flow regime analysis based on Mishima & Ishii's flow regime map indicates that most of the CHF occurred due to liquid film dryout in annular-mist and annular flow regimes. Parametric trends are examined from two different points of view: fixed inlet conditions and fixed exit conditions. The parametric trends are generally consistent with previous understandings except for the complex effects of system pressure and tube diameter. Finally, several prediction models are assessed with the measured data; the typical mechanistic liquid film dryout model and empirical correlations of (Shah, M.M., 1987. Heat Fluid Flow 8 (4), 326–335; Baek, W.P., Kim, H.G., Chang, S.H., 1997. KAIST critical heat flux correlation for water flow in vertical round tubes, NUTHOS-5, Paper No. AA5) show good predictions. The measured CHF data are listed in Appendix B for future reference.

Expert systems that have neural networks for their knowledge bases are called connectionist expert systems. Several powerful advantages of connectionist expert systems over conventional rule-based ...

A series of experiments have been performed to understand the pool-boiling critical heat flux (CHF) behavior on small plates, varying the inclination angle and size of the heated surface under near atmospheric pressure: the first-phase experiment to clarify the CHF behavior at near the horizontal downward-facing position and the second-phase experiment to find out the general CHF behavior for overall inclination angles. The first- and second-phase experiment were performed for the inclination angles from −90° (horizontally downward position) to −40° using two plate-type test sections (20×200 mm and 25×200 mm) submerged in a pool of saturated water and for overall inclination angles from −90° to 90° using two plate-type test sections (30×150 mm and 40×150 mm) submerged in a slightly subcooled water pool, respectively. The CHF generally decreases as its inclination approaches to −90°, but there is a transition angle, at which the rate of decrease in the CHF suddenly changes. The measured CHF is lower for the wider test section due to the increased difficulty of bubble escape and this size effect increases as the inclination angle approaches to −90°.

In the present paper, critical heat flux (CHF) experiments for flow boiling of R-134a were performed to investigate the CHF characteristics of four-head and six-head rifled tubes in comparison with a smooth tube. Both of rifled tubes having different head geometry have the maximum inner diameter of 17.04 mm while the smooth tube has the average inner diameter of 17.04 mm. The experiments were conducted for the vertical orientation under outlet pressures of 13, 16.5, and 23.9 bar, mass fluxes of 285–1300 kg/m2s and inlet subcooling temperatures of 5–40 °C in the R-134a CHF test loop. The parametric trends of CHF for the tubes show a good agreement with previous understanding. In particular, CHF data of the smooth tube for R-134a were compared with well-known CHF correlations such as Bowring and Katto correlations. The CHF in the rifled tube was enhanced to 40–60% for the CHF in the smooth tube with depending on the rifled geometry and flow parameters such as pressure and mass flux. In relation to the enhancement mechanism, the relative vapor velocity is used to explain the characteristics of the CHF performance in the rifled tube.

Surfactant effect on CHF (critical heat flux) was determined during water flow boiling at atmospheric pressure in closed loop filled with solution of tri-sodium phosphate (TSP, Na3PO4 · 12H2O). TSP was added to the containment sump water to adjust pH level during accident in nuclear power plants. CHF was measured for four different water surfactant solutions in vertical tubes, at different mass fluxes (100–500 kg/m2 s) and two inlet subcooling temperatures (50 °C and 75 °C). Surfactant solutions (0.05–0.2%) at low mass flux (∼100 kg/m2 s) showed the best CHF enhancement. CHF was decreased at high mass flux (500 kg/m2 s) compared to the reference plain water data. Maximum increase in CHF was about 48% as compared to the reference data. Surfactant caused a decrease in contact angle associated with an increase of CHF from surfactant addition.

A study of post-dryout heat transfer was performed with a directed heated smooth tube and rifled tubes using vertical R-134a up-flow to investigate the heat transfer characteristics in the post-dryout region. Three types of rifled tube having different rib height and width were used to examine the effects of rib geometry and compare with the smooth tube, using a mass flux of 70–800 kg/m2 s and a pressure of 13–24 bar (corresponding to an approximate water pressure of 80–140 bar). Wall temperature distribution in all tubes was strongly dependent on pressure and mass flux. Wall temperatures of the rifled tubes in the post-dryout region were much lower than for the smooth tube at same conditions. This was attributed to swirl flow caused by the rib. Thus, the thermal non-equilibrium, which is usually present in the post-dryout region, was lowered. The empirical correlation of heat transfer in the smooth tube of the post-dryout region was obtained. The heat transfer correlation for rifled tubes was also obtained as a function of rib height and width with the modification of the smooth tube correlation.

In this study, the effects of tri-sodium phosphate (TSP) and boric acid on CHF enhancement were studied. Both TSP and boric acid are used to control pH in nuclear power plants. TSP is a kind of surfactant, and several surfactants, include TSP, have been reported to have an effect on enhancement of heat transfer. Nothing has yet been reported for the case of boric acid. CHF experiments were performed with mass flux ranging from 100-500 kg/m2 s and inlet subcooling temperature of 50 °C under atmospheric pressure. The test section was a vertical circular SS316 tube having an inner diameter of 10.98 mm. Its heated length was 224 mm, and it was heated by a heat flux control system using DC electricity. Fluids in the test loop were plain water, TSP solutions, and boric acid solutions. TSP solutions had three concentrations (0.2, 0.4, 0.6%), and boric acid solutions had four concentrations (0.2, 0.4, 0.6, 0.8%). In the case of TSP, 21.4% enhancement of CHF was observed at the inlet subcooling temperature of 50 °C and extremely low mass flux (100 kg/m2 s). In the case of boric acid, 12.4% enhancement of CHF was observed at inlet subcooling temperature of 50 °C and extremely low mass flux 100 kg/m2 s.

Although the harsh space environment imposes many severe challenges to space pioneers, space exploration is a realistic and profitable goal for long-term humanity survival. One of the viable and promising options to overcome the harsh environment of space is nuclear propulsion. Particularly, the Nuclear Thermal Rocket (NTR) is a leading candidate for near-term human missions to Mars and beyond due to its relatively high thrust and efficiency. Traditional NTR designs use typically high power reactors with fast or epithermal neutron spectrums to simplify core design and to maximize thrust. In parallel there are a series of new NTR designs with lower thrust and higher efficiency, designed to enhance mission versatility and safety through the use of redundant engines (when used in a clustered engine arrangement) for future commercialization. This paper proposes a new NTR design of the second design philosophy, Korea Advanced NUclear Thermal Engine Rocket (KANUTER), for future space applications. The KANUTER consists of an Extremely High Temperature Gas cooled Reactor (EHTGR) utilizing hydrogen propellant, a propulsion system, and an optional electricity generation system to provide propulsion as well as electricity generation. The innovatively small engine has the characteristics of high efficiency, being compact and lightweight, and bimodal capability. The notable characteristics result from the moderated EHTGR design, uniquely utilizing the integrated fuel element with an ultra heat-resistant carbide fuel, an efficient metal hydride moderator, protectively cooling channels and an individual pressure tube in an all-in-one package. The EHTGR can be bimodally operated in a propulsion mode of 100 MWth and an electricity generation mode of 100 kWth, equipped with a dynamic energy conversion system. To investigate the design features of the new reactor and to estimate referential engine performance, a preliminary design study in terms of neutronics and thermohydraulics was carried out. The result indicates that the innovative design has great potential for high propellant efficiency and thrust-to-weight of engine ratio, compared with the existing NTR designs. However, the build-up of fission products in fuel has a significant impact on the bimodal operation of the moderated reactor such as xenon-induced dead time. This issue can be overcome by building in excess reactivity and control margin for the reactor design.

We described the discovery and optimization of a novel series of pyrimidopyrimidine derivatives as G-protein coupled receptor 119 (GPR119) agonists against type 2 diabetes. Most designed compounds displayed significant GPR119 agonistic activities. Optimized analogues 15a and 21e exhibited highly potent agonistic activities with single digit EC50 values (2.2 nM and 8.1 nM, respectively). Therefore, 15a and 21e were evaluated for their oral glucose tolerance test (oGTT) in C57BL/6N mice. Compound 15a reduced the blood glucose area of under curve from 0 to 2 h (AUC0–2h) to 13.5% at the dose of 15 mg/kg comparing with Metformin reduced 18% of AUC0–2h at the dose of 300 mg/kg.

Huangqi Guizhi Wuwu Decoction (HGWWD), consisting of Radix Astragali, Cinnamomi Ramulus, Paeoniae Radix Alba, Zingiberis Rhizoma Recens and Jujubae Fructus, is a widely used Traditional Chinese Medicine (TCM) formula for the treatment of human blood impediment in China for nearly 2000 years. In order to make good and rational use of this formula in the future, a rapid, sensitive and robust ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed for simultaneous determination of calycosin-7-O-β-D-glucoside, cinnamic acid, paeoniflorin and albiflorin, the main active constituents of HGWWD, in rat plasma using geniposide as internal standard (IS). The plasma samples were extracted by protein precipitation with acetonitrile and separated on a Shim-pack XR-ODS C18 column (75 mm × 3.0 mm, 2.2 μm) using gradient elution with a mobile phase consisting of water (containing 0.1% formic acid) and acetonitrile at a flow rate of 0.4 mL/min. Mass spectrometric detection was performed on 3200 QTRAP mass spectrometry equipped with electrospray ionization source in negative ionization mode. Quantification was performed using multiple reaction monitoring (MRM) by monitoring the fragmentation of m/z 491.1→282.9 for calycosin-7-O-β-D-glucoside, m/z147.0→103.1 for cinnamic acid, m/z 525.0→120.9 for paeoniflorin, m/z 525.2→121.0 for albiflorin and m/z 433.1→225.1 for IS, respectively. The method was well validated in terms of linearity, precision, accuracy, recovery, matrix effect and stability. All calibration curves had good linearity (r>0.9977) over the concentration range from 0.1–50 ng/mL for calycosin-7-O-β-D-glycoside, 50–25000 ng/mL for cinnamic acid, 5–2500 ng/mL for paeoniflorin and albiflorin. The intra-day and inter-day precisions (relative standard deviation) were within 11.8%, the accuracy (relative error) ranged from −9.4% to 9.1%, and the lower limit of quantification (LLOQ) were 0.1, 50, 5, 5 ng/mL for calycosin-7-O-β-D-glucoside, cinnamic acid, paeoniflorin and albiflorin, respectively. Extraction recovery, matrix effect and stability were satisfactory in rat plasma. The validated method was successfully applied to a pharmacokinetic study of calycosin-7-O-β-D-glucoside, cinnamic acid, paeoniflorin and albiflorin after oral administration of HGWWD to rats.

The behavior of near-wall bubbles in subcooled flow boiling has been investigated photographically for water flow in vertical, one-side heated, rectangular channels at mass fluxes of 500, 1500, 2000 kg·m−2·s−1 under atmospheric pressure. Primary attention was given to the bubble coalescence phenomenon and the structure of the near-wall bubble layer. The number of near-wall bubbles increased with the increase in the heat flux. At sufficiently high heat fluxes (>60–70% CHF), three characteristic layers were observed in the heated channel: a superheated liquid layer with small bubbles attached on the heated wall, a flowing bubble layer consisting of large coalesced bubbles over the superheated liquid layer, and the liquid core over the flowing bubble layer. In addition, the existence of a liquid sublayer under coalesced bubbles was identified photographically. According to visualization, the CHF mechanism for the present experimental condition could be related to the formation of large vapor clots resulting from coalescences of bubbles and the evaporation of the superheated liquid layer beneath those clots.

The critical heat flux (CHF) phenomenon has been investigated for a stable flow of water in vertical tubes at low pressure and velocity conditions. Experiments have been performed with round tubes with diameters of 0.006 m and 0.0088 m for mass fluxes below 220 kg/m2s under atmospheric pressure. Experimental results are discussed with special reference to the physical mechanism leading to the CHF at very low flow conditions. Finally a new design correlation is proposed based on the combination of the present data and other CHF data available in the literature. Assessments show reasonable agreement of predictions with experiments.

Existing techniques to mine periodic patterns in time series data are focused on discovering full-cycle periodic patterns from an entire time series. However, many useful partial periodic patterns are hidden in long and complex time series data. In this paper, we aim to discover the partial periodicity in local segments of the time series data. We introduce the notion of character density to partition the time series into variable-length fragments and to determine the lower bound of each character’s period. We propose a novel algorithm, called DPMiner, to find the dense periodic patterns in time series data. Experimental results on both synthetic and real-life datasets demonstrate that the proposed algorithm is effective and efficient to reveal interesting dense periodic patterns.

A specific and reliable HPLC–MS/MS method was developed and validated for the simultaneous determination of six alkaloids in rat plasma, jatrorrhizine, berberine, tetrahydropalmatine, protopine, bicuculline and palmatine. The analytes were separated on a C18 column (50 mm × 2.1 mm, 1.8 μm) and a triple-quadrupole mass spectrometry equipped with an electrospray ionization (ESI) source was used for detection. The plasma sample was prepared by the simple protein precipitation and the recovery for the six analytes was over 80%. The calibration curves were linear over a concentration range of 0.38–1900.0 ng/mL for jatrorrhizine, 0.57–2850.0 ng/mL for berberine, 0.32–1600.0 ng/mL for tetrahydropalmatine, 0.21–1050.0 ng/mL for protopine, 0.34–1700.0 ng/mL for bicuculline and 0.22–1100 ng/mL for palmatine. The intra-day and inter-day precision was less than 15% and the relative error (RE) was all within ±15%. The validated method was successfully applied to a pharmacokinetics study in rats after oral administration of the extracts of Rhizoma Corydalis Decumbentis (a famous Chinese herb).

A novel, simple, and efficient protocol <italic>via</italic> Pd(<sc>ii</sc>)-catalyzed denitrogenative coupling of arylhydrazines with aryl halides under ambient and mild conditions.

The carbonylative Suzuki–Miyaura reaction between aryl tosylates/triflates with arylboronic acid is herein reported, using base-free conditions and a balloon pressure of carbon monoxide.

Bubble nucleation itself is less important safety issue for nuclear reactor, but it can easily lead to critical thermal-hydraulic events such as OFI (Onset of Fluid Instability) or CHF (Critical Heat Flux) when a research reactor operates under atmospheric conditions. Thus, the ONB (Onset of Nucleate Boiling) margin for normal operation in research reactor is recommended. In the IAEA-TECDOC-233 report (IAEA, 1980), the ONB margin for a research reactor is recommended as well. Although the ONB margin in a research reactor is emphasized for such reasons, only a few experiments have been performed for downward flow direction in a narrow, rectangular channel. In addition, several existing ONB prediction correlations are arguably applicable to the flow boiling condition in the narrow rectangular channel because most of them are developed based on Hsu’s model, which was developed in the pool boiling cases. In the study, ONB experiments for various inlet temperature conditions and mass flux conditions were performed with increasing heat flux step by step. Based on experimental data, the effect of inlet temperature and mass flux on the wall superheat and heat flux at ONB was investigated. In addition, existing ONB prediction correlations were evaluated for predicting wall superheat and heat flux at ONB based on the experimental data. A new ONB prediction correlation was then developed for better-evaluation and was compared with other correlations.

A new method to predict the critical heat flux (CHF) is proposed, based on the fuzzy clustering and artificial neural network. The fuzzy clustering classifies the experimental CHF data into a few data clusters (data groups) according to the data characteristics. After classification of the experimental data, the characteristics of the resulting clusters are discussed with emphasis on the distribution of the experimental conditions and physical mechanism. The CHF data in each group are trained in an artificial neural network to predict the CHF. The artificial neural network adjusts the weight so as to minimize the prediction error within the corresponding cluster. Application of the proposed method to the KAIST CHF data bank shows good prediction capability of the CHF, better than other existing methods.

AbstractAbstractThe best-estimate thermal-hydraulic codes RE-LAP5/MOD3 and COBRA-TF were adopted to the Apollo DN 10000 workstation and subsequently merged. This was done to combine the excellent features of the two codes and thus produce a code with much enhanced capability. The resulting code was named COBRA/RELAPS. This code has features in common with COBRA/TRAC or TRAC-PF1: three-dimensional reactor vessel and one-dimensional loop modeling capability. The merging of the two codes is focused on the hydrodynamic model and numerical solution schemes. In COBRA/RELAP5, the system pressure matrices of the two codes are merged and solved simultaneously. The merged COBRA/RELAP5 calculations are done in process-level parallel mode on the Apollo DN10000 computer with two central processing units. Through various test simulations, the merging scheme and its implementation were proven to be valid. Thus, the code predictability is presumed eventually to depend on the generic capabilities of COBRA-TF and RELAP5/MOD3. However, to evaluate the overall code capability of COBRA/RELAP5, a systematic assessment should be done, including multidimensional effect tests.

In order to gain an understanding of the relationship between critical heat flux (CHF) and flow-induced vibration (FIV), an experimental investigation was carried out with vertical round tube at the atmosphere. In the both condition of departure from nucleate boiling (DNB) and the liquid film dryout (LFD), CHF increases up to 12.6% with vibration intensity, represented by vibrational Reynolds number (Rev). CHF enhancement by tube vibration seems to come from the reinforced flow turbulent mixing and the increment of deposition of droplet into the liquid film. Based on the experimental results, an empirical correlation is proposed for the prediction of CHF enhancement ratio. The correlation predicts the CHF enhancement ratio (En) with reasonable accuracy, with an average error rate of 4.5 and 26.5% for RMS. Vibration is an effective method for heat transfer enhancement as well as CHF. Nonetheless, the risk of system failure by FIV has made it very difficult to take advantage of vibration in heat transfer facilities. Therefore, it is necessary to find out optimal fuel design enhancing the CHF but preventing FIV damage in an acceptable vibration range.

Serious mechanical damages such as cracks and plastic deformations due to excessive thermal stress caused by thermal stratification have been experienced in several nuclear power plants. In particular, the thermal stratification in the pressurizer surge line has been addressed as one of the significant safety and technical issues. In this study, a detailed unsteady computational fluid dynamics (CFD) analysis involving conjugate heat transfer analysis is performed to obtain the transient temperature distributions in the wall of the pressurizer surge line subjected to stratified internal flows either during out-surge or in-surge operation. The thermal loads from CFD calculations are transferred to the structural analysis code which is employed for the thermal stress analysis to investigate the response characteristics, and the fatigue analysis is ultimately performed. In addition, the thermal stress and fatigue analysis results obtained by applying the realistic temperature distributions from CFD calculations are compared with those by assuming the simplified temperature distributions to identify some requirements for a realistic and conservative thermal stress analysis from a safety point of view.

This study describes critical heat flux (CHF) experiments using a 2-D curved test section with trisodium phosphate (TSP: Na3PO4) and boric acid (BA: H3BO5). The CHF values of TSP solution, BA solution, and TSP + BA solution were enhanced by as much as 50% for all experimental conditions except the condition of 150 mm radius with BA solution. The enhancement can be explained by decreased contact angle (enhancement of wettability). This CHF enhancement could provide additional thermal margin for the IVR-ERVC strategy.

Trajectory classification has many useful applications. Existing works on trajectory classification do not consider the duration information of trajectory. In this paper, we extract duration-aware features from trajectories to build a classifier. Our method utilizes information theory to obtain regions where the trajectories have similar speeds and directions. Further, trajectories are summarized into a network based on the MDL principle that takes into account the duration difference among trajectories of different classes. A graph traversal is performed on this trajectory network to obtain the top-k covering path rules for each trajectory. Based on the discovered regions and top-k path rules, we build a classifier to predict the class labels of new trajectories. Experiment results on real-world datasets show that the proposed duration-aware classifier can obtain higher classification accuracy than the state-of-the-art trajectory classifier.

An efficient protocol has been developed for the carbonylative Hiyama coupling of aryl halides using the cesium fluoride as a promoter by palladium-catalyzed in NMP. This protocol was applied to a wide variety of functionalized and hindered aryl iodides and bromides with arylsilanes, to afford the desired biaryl ketones in good to excellent yields.

Research reactors are recommended to be designed with sufficient safety margin for critical heat flux (CHF) in both normal and transient operation, which requires the development of predictive CHF models for both subcooled and saturated flow boiling conditions. While models exist for saturated flow boiling conditions, to date, no mechanistic CHF approach has been developed for subcooled flow boiling in a rectangular channel. In this paper, a new mechanistic model is derived to predict the subcooled flow boiling CHF in a rectangular channel for turbulent upward flow under low pressure. The proposed model is characterized by its consideration of coalesced vapor clot growth due to bubble coalescence not only in the flow direction, but also in the radial direction. In addition, existing liquid sublayer thickness calculation methods were compared to account for the thinning of the liquid sublayer due to the vapor clot growth. The proposed model was verified with a dataset consisting of 126 data points covering the following operational ranges: pressure 1.01–1.13 bar, mass flux 853–15,120 kg/m2s, exit quality –0.125 to –0.006, inlet subcooling 8–80 K, channel width 4–22 mm, channel gap 1–6.35 mm, heated length 50–305 mm, and turbulent upward flow. The developed model showed good prediction performance with a 32.47% RMS error, which is the lowest error compared to existing liquid sublayer dryout models developed for circular channels.

The gearbox of bogie is the core transmission component of the high-speed train. Once its parts have problems, this will cause hidden danger to the running of the train. Therefore, the safety of the gearbox parts must be paid special attention. The failed samples studied in this paper were the polycarbonate (PC) plates used in the gearbox oil level gauge and seven PC plates were found failure during routine maintenance for a certain type of high-speed train. Among them, five plates had cracks parallel to the oil level and close to the middle area, while other two plates had cracks near the circular arc area and lay at an angle of 45° with the level line. In order to find out the root cause of their failure, a variety of material analysis methods were used to examine the properties of the materials, and the fracture morphologies were studied in detail by means of macro and micro observations. The analysis results show that the causes of the failed PC plates could be divided into two types, one was caused by environmental stress cracking and thermal fatigue and the other was caused by forced installation when the length of the PC plate was a little larger. According to the correct determination of the failure causes, the pertinent countermeasures like length reduction of the PC plate and spraying special transparent coating on the PC plate have been put forward, which have been proven very effective after execution.

The plastic components are always more prone to property degradation than the conventional metallic components, so their safety reliability is paid more attention for the routine maintenance. The gas relay containing two plastic balls is an important safety protection device of the high-voltage transformer. The two plastic hollow floating balls inside the relay buoy in the insulating oil level, and float up and down with exhausting and generation of the gas and oil. Once the oil level increases or decreases beyond the safety limits, the protection switches are immediately actuated by the floating ball. In this paper, one plastic floating ball inside the relay in high-voltage transformer was found leaked during one refueling cycle of a nuclear power plant because quite a bit insulating oil was penetrated inside the ball. Although no serious consequence had been aroused, it will bring the potential safety hazards for the normal operation of the transformer. For this reason, the failure analysis was systematically performed to analyze and identify the causes of abnormal leakage of the plastic ball. The comprehensive testing and analysis results indicated that the unqualified fusion process of two plastic hemispheres was the root cause, thus the pertinent countermeasures were proposed.

Localizing people and recognizing their actions from videos is a challenging task towards high-level video understanding. Existing methods are mostly two-stage based, with one stage for person bounding box generation and the other stage for action recognition. However, such two-stage methods are generally with low efficiency. We observe that directly unifying detection and action recognition normally suffers from (i) inferior learning due to different desired properties of context representation for detection and action recognition; (ii) optimization difficulty with insufficient training data. In this work, we present a decoupled onestage network dubbed DOAD, to mitigate above issues and improve the efficiency for spatio-temporal action detection. To achieve it, we decouple detection and action recognition into two branches. Specifically, one branch focuses on detection representation for actor detection, and the other one for action recognition. For the action branch, we design a transformer-based module (TransPC) to model pairwise relationships between people and context. Different from commonly used vector-based dot product in self-attention, it is built upon a novel matrix-based key and value for Hadamard attention to model person-context information. It not only exploits relationships between person pairs but also takes into account context and relative position information. The results on AVA and UCF101-24 datasets show that our method is competitive with two-stage state-of-theart methods with significant efficiency improvement.

The circulating-turbulent fluidized bed (CTFB) is an important fluidization regime that can maintain a high solid concentration and high reaction intensity as in turbulent fluidized bed, and suppress solids back-mixing as in circulating fluidized bed. Computational fluid dynamics (CFD) studies on it are however very sparse. In this study, extensive three-dimensional CFD simulations of CTFB are carried out using the mesoscience-based structural model (Liu et al., 2023), where the gas-rich dilute phase and the particle-rich dense phase are defined as the two interpenetrating continua, instead of treating the gas and particles as the two interpenetrating continua as in classical two-fluid models. It is shown that the model is able to faithfully predict the hydrodynamics of CTFB, in terms of axial and radial solid concentration profiles and radial solid velocity profiles. This study not only provides a systematical CFD study on the hydrodynamics of gas–solid flow in CTFB but also offers validations of the mesoscience-based structural model via simulating the hydrodynamics of new fluidization regime (CTFB).

The aim of this study was to develop cholic-acid-stabilized itraconazole nanosuspensions (ITZ-Nanos) with the objective of enhancing drug dissolution and oral absorption. A laboratory-scale microprecipitation-high-pressure homogenization method was employed for the preparation of the ITZ-Nanos, while dynamic light scattering, transmission electron microscope analysis, X-ray diffraction, differential scanning calorimetry, and high-performance liquid chromatography analysis were utilized to evaluate their physicochemical properties. The absorption and bioavailability of the ITZ-Nanos were assessed using Caco-2 cells and rats, with Sporanox® pellets as a comparison. Prior to lyophilization, the particle size of the ITZ-Nanos measured approximately 225.7 nm. Both X-ray diffraction and differential scanning calorimetry confirmed that the ITZ remained crystalline within the nanocrystals. Compared to the pellets, the ITZ-Nanos exhibited significantly higher levels of supersaturation dissolution and demonstrated enhanced drug uptake by the Caco-2 cells. The AUC(0-t) value for the ITZ-Nanos in rats was 1.33-fold higher than that observed for the pellets. These findings suggest that cholic acid holds promise as a stabilizer for ITZ nanocrystals, as well as potentially other nanocrystals.

While lithium resources are scarce for high energy‐dense lithium‐ion batteries (LIBs), sodium‐ion batteries (SIBs), serving as an alternative, inherently suffer from low capacity and the high‐cost use of non‐graphite anodes. Combining Li‐ and Na‐ions within a single battery system is expected to mitigate the shortcomings of both systems while leveraging their respective advantages. In this study, we developed and assembled a nanodiamonds (NDs)‐assisted co‐Li/Na‐ion battery (ND–LSIB). This innovative battery system comprised a commercial graphite anode, an ND‐modified polypropylene (DPP) separator, a hybrid lithium/sodium‐based electrolyte, and a cathode. It is theoretically and experimentally demonstrated that the ND/Li co‐insertion can serve as an ion‐drill opening graphite layers and reconstructing graphite anodes into few‐layered graphene with expanding interlayer space, achieving highly efficient Li/Na storage and the theoretical maximum of LiC 6 for Li storage in graphite. In addition, ND is helpful for creating a LiF‐/NaF‐rich hybrid solid electrolyte interface with improved ionic mobility, mechanical strength, and reversibility. Consequently, ND–LSIBs have higher specific capacities ~1.4 times the theoretical value of LIBs and show long‐term cycling stability. This study proposes and realizes the concept of Li/Na co‐storage in one ion battery with compatible high‐performance, cost‐effectiveness, and industrial prospects.

An on-line fuzzy expert system, called alarm filtering and diagnostic system (AFDS), was developed to provide the operator with clean alarm pictures and system-wide failure information during abnormal states through alarm filtering and diagnosis. In addition, it carries out alarm prognosis to warn the operator of process abnormalities. Clean alarm pictures that have no information overlapping are generated from multiple activated alarms at the alarm filtering stage. The meta rules for dynamic filtering were established on the basis of the alarm relationship network. In the case of alarm diagnosis, the relations between alarms and abnormal states are represented by means of fuzzy relations, and the compositional inference rule of fuzzy logic is utilized to infer abnormal states from the fuzzy relations. The AFDS offers the operator related operating procedures as well as diagnostic results. At the stage of alarm prognosis, the future values of some important critical safety parameters are predicted by means of Levinson algorithm selected from the comparative experiments, and the global trends of these parameters are estimated using data smoothing and fuzzy membership. This information enables early failure detection and is also used to supplement diagnostic symptoms. The AFDS has been validated and demonstrated using the full-scope simulator for Yonggwang Units 1, 2. From the validation results, it can be concluded that the AFDS is able to aid the operator to terminate early and mitigate plant abnormalities.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A new experimental work was made to discover a principle mechanism of the burnout in pool boiling. Here, we directly observed a liquid layer structure under a massive vapor clot and the liquid layer-related burnout phenomenon. Based on the present observations, we have made a visual model for the formation and dryout of a liquid film under its vapor environment. At the formation process, liquid is trapped in interleaved space between growing bubbles and surface and the liquid trapping continues between coalesced bubbles and surface. In the dryout process, we especially observed vapor “holes” made by spontaneous breakup of discrete nucleating bubbles inside a vapor clot. The burnout can be triggered by the evaporation of the liquid film region expanded from rims of the holes.

Advances in web technology have given rise to new information retrieval applications. In this paper, we present a model for geographical region search and call this class of query similar region query. Given a spatial map and a query region, a similar region search aims to find the top-k most similar regions to the query region on the spatial map. We design a quadtree based algorithm to access the spatial map at different resolution levels. The proposed search technique utilizes a filter-and-refine manner to prune regions that are not likely to be part of the top-k results, and refine the remaining regions. Experimental study based on a real world dataset verifies the effectiveness of the proposed region similarity measure and the efficiency of the algorithm.

Station blackout (SBO) is a typical beyond design basis accident (BDBA) and significant contributor to overall plant risk. The risk analysis of SBO could be important basis of rulemaking, accident mitigation strategy, etc. Recently, studies on the integrated approach of deterministic and probabilistic method for nuclear safety in nuclear power plants have been done, and among them, the combined deterministic and probabilistic procedure (CDPP) was proposed for safety assessment of the BDBAs. In the CDPP, the conditional exceedance probability obtained by the best estimate plus uncertainty method acts as go-between deterministic and probabilistic safety assessments, resulting in more reliable values of core damage frequency and conditional core damage probability. In this study, the safety assessment of OPR-1000 nuclear power plant for SBO accident was performed by applying the CDPP. It was confirmed that the SBO risk should be reevaluated by eliminating excessive conservatism in existing probabilistic safety assessment to meet the targeted core damage frequency and conditional core damage probability. By estimating the offsite power restoration time appropriately, the SBO risk was reevaluated, and it was finally confirmed that current OPR-1000 system lies in the acceptable risk against the SBO. In addition, it is concluded that the CDPP is applicable to safety assessment of BDBAs in nuclear power plants without significant erosion of the safety margin.

Purification and characterization of a novel bacteriocin produced by strain Enterococcus faecium D081821.Enterococcus faecium D081821, isolated from the traditional Taiwanese fermented food dochi (fermented black beans), was previously found to produce a bacteriocin against Listeria monocytogenes and some Gram-positive bacteria. This bacteriocin, termed enterocin TW21, was purified from culture supernatant by ammonium sulfate precipitation, Sep-Pak C18 cartridge, ion-exchange and gel filtration chromatography. Mass spectrometry analysis showed the mass of the peptide to be approximately 5300·6 Da. The N-terminal amino acid sequencing yielded a partial sequence NH2 -ATYYGNGVYxNTQK by Edman degradation, and it contains the consensus class IIa bacteriocin motif YGNGV in the N-terminal region. The open reading frame (ORF) encoding the bacteriocin was identified from the draft genome sequence of Enterococcus faecium D081821, and sequence analysis of this peptide indicated that enterocin TW21 is a novel bacteriocin.Enterococcus faecium D081821 produced a bacteriocin named enterocin TW21, the molecular weight and amino acid sequence both revealed it to be a novel bacteriocin.A new member of class IIa bacteriocin was identified. This bacteriocin shows great inhibitory ability against L. monocytogenes and could be applied as a natural food preservative.

Abstract Zhi‐Zi‐Hou‐Po Decoction, consisting of Gardenia jasminoides Ellis, Magnolia officinalis Rehd. et Wils., and Citrus aurantium L, is a classical Traditional Chinese Medicine formula for the treatment of depression. In order to make good and rational use of this formula in the future, a sensitive, selective, and reliable ultra high performance liquid chromatography with tandem mass spectrometry method was developed for simultaneous determination of two iridoid glycosides (geniposide and genipin gentiobioside), two lignans (honokiol and magnolol), four flavonoid glycosides (isonaringin, naringin, hesperidin, and neohesperidin), the major bioactive constituents of Zhi‐Zi‐Hou‐Po Decoction, in rat plasma using paeoniflorin as internal standard. Plasma samples were pretreated by a simple protein precipitation with acetonitrile. Chromatographic separation was performed on a shim‐pack XR‐ODS C 18 column (75 × 3.0 mm, 2.2 µm) using gradient elution with mobile phase consisting of 0.1% formic acid aqueous solution and acetonitrile at a flow rate of 0.5 mL/min. Mass spectrometric detection was conducted on a 3200 QTRAP mass spectrometry equipped with electrospray ionization source in negative ionization mode. Quantification was performed using multiple reactions monitoring mode. Calibration curves exhibited good linearity ( r &gt; 0.9947) over a wide concentration range for all analytes, and the lower limits of quantification were 10, 5, 1, 5, 1, 5, 1, and 5 ng/mL for geniposide, genipin gentiobioside, honokiol, magnolol, isonaringin, naringin, hesperidin, and neohesperidin, respectively. The intraday and interday precisions at three quality control levels were less than 12.3% and the accuracies ranged from −11.2 to 10.7%. Extraction recovery, matrix effect, and stability were satisfactory in rat plasma. The validated method was successfully applied to a pharmacokinetic study of the eight analytes after oral administration of Zhi‐Zi‐Hou‐Po decoction to rats.

Video-based human pose estimation in crowed scenes is a challenging problem due to occlusion, motion blur, scale variation and viewpoint change, etc. Prior approaches always fail to deal with this problem because of (1) lacking of usage of temporal information; (2) lacking of training data in crowded scenes. In this paper, we focus on improving human pose estimation in videos of crowded scenes from the perspectives of exploiting temporal context and collecting new data. In particular, we first follow the top-down strategy to detect persons and perform single-person pose estimation for each frame. Then, we refine the frame-based pose estimation with temporal contexts deriving from the optical-flow. Specifically, for one frame, we forward the historical poses from the previous frames and backward the future poses from the subsequent frames to current frame, leading to stable and accurate human pose estimation in videos. In addition, we mine new data of similar scenes to HIE dataset from the Internet for improving the diversity of training set. In this way, our model achieves best performance on 7 out of 13 videos and 56.33 average wAP on test dataset of HIE challenge.

Dynamic response of a GaAs/AlGaAs microdisk laser has been experimentally investigated using femtosecond optical pumping. Below the lasing threshold, the delay time of the emission pulse from the microdisk hardly changes with the pump power. Above the lasing threshold, the delay time is shortened dramatically, and it decreases with increasing the pump power. The theoretical simulation based on the rate equations reproduces the experimental observation after the effect of carrier diffusion is taken into account. The simulation result illustrates that the speed of a microdisk laser is limited mainly by the carrier diffusion in the disk plane.

An advanced human–machine interface (HMI) has been developed to enhance the safety and availability of a nuclear power plant (NPP) by improving operational reliability. The key elements of the proposed HMI are the large display panels which present synopsis of plant status and the compact, computer-based work stations for monitoring, control and protection functions. The work station consists of four consoles such as a dynamic alarm console (DAC), a system information console (SIC), a computerized operating-procedure console (COC), and a safety system information console (SSIC). The DAC provides clean alarm pictures, in which information overlapping is excluded and alarm impacts are discriminated, for quick situation awareness. The SIC supports a normal operation by offering all necessary system information and control functions over non-safety systems. In addition, it is closely linked to the other consoles in order to automatically display related system information according to situations of the DAC and the COC. The COC aids operators with proper operating procedures during normal plant startup and shutdown or after a plant trip, and it also reduces their physical/mental burden through soft automation. The SSIC continuously displays safety system status and enables operators to control safety systems. The proposed HMI has been evaluated using the checklists that are extracted from various human factors guidelines. From the evaluation results, it can be concluded that the HMI is so designed as to address the human factors issues reasonably. After sufficient validation, the concept and the design features of the proposed HMI will be reflected in the design of the main control room of the Korean Next Generation Reactor (KNGR).

Existing graph mining algorithms typically assume that databases are relatively static and can fit into the main memory. Mining of subgraphs in a dynamic environment is currently beyond the scope of these algorithms. To bridge this gap, we first introduce a partition-based approach called PartMiner for mining graphs. The PartMiner algorithm finds the frequent subgraphs by dividing the database into smaller and more manageable units, mining frequent subgraphs on these smaller units and finally combining the results of these units to losslessly recover the complete set of subgraphs in the database. Next, we extend PartMiner to handle updates in the dynamic environment. Experimental results indicate that PartMiner is effective and scalable in finding frequent subgraphs, and outperforms existing algorithms in the presence of updates.

The effects of mechanical vibrations on critical heat flux (CHF) are examined in this study at atmospheric pressure in vertical annulus tube under electrically heated condition. Vibration of heating rod was increased as flow regime changed from subcooled region to bubbly region. CHF was increased by mechanical vibration up to 16.4%. Vibration amplitude was one of the effective parameters on CHF enhancement. It seems to come from turbulence increasing and increment of deposition of droplet from the liquid film by vibration. Vibration is an effective method for heat transfer enhancement as well as CHF enhancement.

A series of novel 2-phenylaminopyrimidine (PAP) derivatives structurally related to STI-571 were designed and synthesized. The abilities of these compounds to inhibit proliferation were tested in human chronic myeloid leukemia K562 cells. (E)-3-(2-bromophenyl)-N-[4-methyl-3-(4-pyridin-3-yl-pyrimidin-2-ylamino)phenyl]acrylamide(12d) was the most effective cell growth inhibitor and was 3-fold more potent than STI-571.

Information of flow-induced vibration (FIV) in two-phase flow with wire coil inserts at atmospheric pressure, is presented in this study. FIV was measured in an upward vertical tube for four different wire coil inserts using an air–water mixture as process fluid. Vibration increased along with mass flux and quality. The narrower wire coils produced more vibration. The FIV prediction correlation for two-phase flow with wire coil inserts was experimentally developed with coefficient correlation value of 0.956.

Traditional Chinese medicine Celastrus orbiculatus Thunb (C. orbiculatus) with peel and seeds is mainly composed of flavonoids, sesquiterpenes and tripenes. According to the Traditional Chinese medicine standard of Liaoning province (2009), it has been long used to invigorate blood circulation. To identify the antithrombus fraction and components of C. orbiculatus, and to investigate the underlying mechanisms. The antithrombus effects of C. orbiculatus fractions were evaluated in vitro by plasma recalcification time (PRT). The antithrombus effect of NST-50, the most effective fraction, was further investigated in acute pulmonary embolism (APE) mice and FeCl3-induced carotid arterial thrombus rats. Bleeding assessment was also carried out to assess the side effects of NST-50. In addition, the content of total flavonoids and active components of NST-50 was also quantified. Nine flavonoids were detected in NST-50 as main components with the content of 44.70%. Next, NST-50 was found with significant anticoagulation activity by prolonging the plasma recalcification time (PRT), activated partial thromboplastin time (APTT), thrombin time (TT) and prothrombin time (PT) and decreasing the content of fibrinogen (FIB). Furthermore, NST-50 administration markedly suppressed the level of TXB2 and PAI-1, while significantly up-regulated the level of 6-keto-PGF1a and t-PA (p < 0.05). The results demonstrated that NST-50 could be valuable in clinical application against acute coronary syndrome, venous thromboembolisms and cerebrovascular thrombosis. It was possible that the anticoagulation action of NST-50 could be related to the regulation of TXA2 - PGI2 and t-PA - PAI-1 pairs.

The development strategies of a prototype expert system, called ESAPD, for multiple alarm processing and diagnosis in nuclear power plants are described. The main objectives of the system are to assist operators in identifying a primary causal alarm among multiple fired alarms and to diagnose the plant malfunction quickly. The overall plant-wide diagnosis is performed at the alarm processing stage which can identify a primary causal alarm and can diagnose possible failure modes and failed systems and automatic interlock actions. The knowledge base for the alarm processing is represented as object-oriented concepts. The specific root cause diagnosis for the primary causal alarm can be performed at the alarm diagnosis stage. The system can provide operators with the possible causes of the primary causal alarm, emergency actions, and follow-up treatments. The diagnostic method adopted in this system is a hypothesize-and-test paradigm.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Abstract This paper deals with the results of experimental investigations on the effects of tube vibration on critical heat flux (CHF) in order to gain an understanding of the relationship between CHF and flow-induced vibration (FIV). The experiment was carried out in the following range of parameters: diameter (D)=0.008 m; heated length (L)=0.2, 0.4 m; pressure (P)=101 kPa; mass flux (G)=403–2,551 kg/m2.s; quality (x)=-0.045–0.289; amplitude (a)=0.0001–0.001 m; frequency (f)=0–70Hz. The CHF generally increases with vibration intensity, which is represented by vibrational Reynolds number (Re v ); the CHF enhancement is more dependent on amplitude than on frequency. CHF enhancement seems to come from the reinforced flow turbulent mixing effect by vibration in the vicinity of heat transfer surface. Based on the experimental results, an empirical correlation is proposed for the prediction of CHF enhancement by tube vibration. The correlation predicts the CHF enhancement ratio (En) with reasonable accuracy, with an average error rate of -2.18% and 27.75% for RMS. KEYWORDS: critical heat fluxflow-induced vibrationflow boilingCHF enhancementheat transfer enhancementvibration controltube vibrationvibration Reynolds numbernuclear fuel

A thermal-hydraulic analysis code which is capable of modeling both internally and externally cooled annular fuel pins was developed. The coolant flow distribution in the annular fuel-based assemblies is adjusted by a pressure drop model allowing for conditions such as non-equal velocity and non-saturated phases. The heat transfer fraction is determined by the ratio of cross-sectional areas distinguished by the radius at which the first derivative of the temperature within the annular fuel equals zero. The code predictions have been compared with calculations from Korea Atomic Energy Research Institute (KAERI) and MIT. The heat transfer fraction difference between the code and RELAP was about 3.9%, and the Departure from Nucleate Boiling Ratio (DNBR) prediction of the code agreed well with the MIT’s result in the region below 3 m. For the application of the code, thermal-hydraulics of thorium-based fuel assemblies loaded with annular seed pins were compared with those of the existing thorium-based assemblies. The pressure drop in the assembly generally increased in the case of annular fuel due to the larger wetted perimeter. In the inner subchannels of the seed pins, mass fluxes were high due to the grid form losses in the outer subchannels. About 43% of the heat generated from the seed pin flowed into the inner subchannel and the rest into the outer subchannel. The minimum DNBRs (MDNBRs) of the annular fuel-based assemblies were higher than those of the existing ones. Because interchannel mixing cannot occur in the inner subchannels, temperatures and enthalpies were higher in the inner subchannels.

An analysis on the two-phase flow in a helical wire inserted tube using commercial CFD code, CFX11.0, was performed in bubbly flow and annular flow regions. The analysis method was validated with the experimental results of Takeshima. Bubbly and annular flows in a 10 mm inner diameter tube with varying pitch lengths and inserted wire diameters were simulated using the same analysis methods after validation. The geometry range of p/D was 1–4 and e/D was 0.08–0.12. The results show that the inserted wire with a larger diameter increased swirl flow generation. An increasing swirl flow was seen as the pitch length increased. Regarding pressure loss, smaller pitch lengths and inserted wires with larger diameters resulted in larger pressure loss. The average liquid film thickness increased as the pitch length and the diameter of the inserted wire increased in the annular flow region. Both in the bubbly flow and annular flow regions, the effect of pitch length on swirl flow generation and pressure loss was more significant than that of the inserted wire diameters. Pitch length is a more dominant factor than inserted wire diameter for the design of the swirl flow generator in small diameter tubes.

Maintenance technologies have been progressed from a time-based to a condition-based manner. The fundamental idea of condition-based maintenance (CBM) is built on the real-time diagnosis of impending failures and/or the prognosis of residual lifetime of equipment by monitoring health conditions using various sensors. The success of CBM, therefore, hinges on the capability to develop accurate diagnosis/prognosis models. Even though there may be an unlimited number of methods to implement models, the models can normally be classified into two categories in terms of their origins: using physical principles or historical observations. We have focused on the latter method (sometimes referred as the empirical model based on statistical learning) because of some practical benefits such as context-free applicability, configuration flexibility, and customization adaptability. While several pilot-scale systems using empirical models have been applied to work sites in Korea, it should be noted that these do not seem to be generally competitive against conventional physical models. As a result of investigating the bottlenecks of previous attempts, we have recognized the need for a novel strategy for grouping correlated variables such that an empirical model can accept not only statistical correlation but also some extent of physical knowledge of a system. Detailed examples of problems are as follows: (1) missing of important signals in a group caused by the lack of observations, (2) problems of signals with the time delay, and (3) problems of optimal kernel bandwidth. This paper presents an improved statistical learning framework including the proposed strategy and case studies illustrating the performance of the method.

Abstract Tianshu Capsule, consisting of Ligusticum chuanxiong Hort and Gastrodia elata Blume, is a widely used Traditional Chinese Medicine preparation for the treatment of migraine. Ferulic acid and gastrodin are main active constituents in Ligusticum chuanxiong Hort and Gastrodia elata Blume, and have been used as marker components for quality control of Tianshu Capsule. In this study, a selective, sensitive, and reliable ultra‐fast liquid chromatography with tandem mass spectrometry method was developed for simultaneous determination of ferulic acid and gastrodin in rat plasma using geniposide as internal standard. The plasma samples were extracted by protein precipitation with methanol after acidification and separated on a Shim‐Pack XR‐ODS C 18 column (75 × 3.0 mm, 2.2 μm) using gradient elution with a mobile phase consisting of water (containing 0.1% formic acid) and acetonitrile at a flow rate of 0.6 mL/min. Detection was performed on 3200 QTRAP mass spectrometry equipped with turbo ion spray source in negative ionization mode. Validation parameters were within acceptable ranges. The validated method was applied to compare the pharmacokinetic profiles of ferulic acid and gastrodin in normal and migraine rats. Our results showed that there were remarkable differences in the pharmacokinetic properties of the analytes between the normal and migraine groups.

Nuclear Thermal Rocket (NTR) propulsion is a viable and meritorious option for human exploration into deep-space because of its high thrust, improved specific impulse, well established technology, bimodal capability, and enhanced mission safety and reliability. The NTR technology has already been investigated and tested by the United States of America and Russia and the former Soviet Union. The representative Nuclear Engine for Rocket Vehicle Applications (NERVA) type reactors traditionally used Highly Enriched Uranium (HEU) fuels, shaped in hexagonal fuel element geometries because of the importance of making a high power reactor with a minimum size. Although the HEU-NTR designs are the best choice in terms of rocket performance and technical maturity, they inevitably provoke nuclear proliferation obstacles not only for all research and development activities by civilians and non-nuclear weapon states but also for potential commercialization. To overcome the security issues due to HEU, the non-proliferative, small-size NTR engine with low thrust levels of 41 kN–53 kN (9.2 klbf ∼ 11.9 klbf), Korea Advanced NUclear Thermal Engine Rocket utilizing a Low-Enriched Uranium fuel (KANUTER-LEU), is being designed for future generations. Its design goals are to make use of an LEU fuel for its fairly compact core, but to minimize the rocket performance sacrifice relative to the traditional HEU-NTRs. To achieve these goals, a new space propulsion reactor is conceptually designed with the key concepts of a high uranium density fuel with resistance against high heating and H2 corrosion, a thermal neutron spectrum core, and a compact and integrated fuel element core design with protective cooling capability. In addition, a preliminary design study of neutronics and thermal-hydraulics was performed to explore the design space of the new LEU-NTR reactor concept. The result indicates that the innovative reactor concept has great potential, both to implement the use of an LEU fuel and to create comparable rocket performance, compared to the existing HEU-NTR designs.

Ambinine, the major alkaloid of the tuber of Corydalis ambigua var. amurensis, has protective effects on H9C2 myocardial cells. In the present paper, we observed that ambinine demonstrates activities of both anticoagulation and thrombolysis in vitro by significantly degrading the blood clot and delaying the plasma recalcification time (PRT) in a dose-dependent manner (0.5–2 mg/mL). We further studied its safety profile of acute and subacute toxicity by repeated-dose intravenous injection. The median lethal dosage (LD50) of mice given by oral and intravenous administration of ambinine were approximate 800, 41.60 mg/kg, respectively. The acute toxicity research results suggested that compared with an intravenous administration, the oral route is safer to administer ambinine as the promising lead compound for thrombosis. In subacute toxicity research, when mice were given ambinine at doses of 1.40 and 2.10 mg/kg for 7 days by injection, significant alteration of the relative kidney weight, the relative liver weight and serum biochemistry parameters and marked histopathological changes of them were found.

The decarboxylative alkynylation of alkynyl carboxylic acids and arylsulfonyl hydrazides by desulfinative coupling could provide aryl alkynes in satisfactory yields by either judiciously selecting palladium catalysts or modulating phosphine ligands under mild conditions.

Considering the large quantity of passengers in a running rail vehicle, its safety must be paid special attention to, which relies on the reliability of every critical component. Spherical universal joint is widely used in the suspension device of the gearbox in the transmission of railway vehicles for its functions of damping and cushioning. Since it's commonly made of rubbers rather than the familiar metallic materials, its degradation behaviors and failure mechanisms have not been systematically investigated. In this study, multiple rubber spherical universal joints used in the urban rail transit train were found cracked and sticky during maintenance. Its design lifetime was 5 years, but this kind of failure occurred in <2 years, which posed a threat to the safe operation of the train. In order to identify the root causes of the failure, the physical, chemical, mechanical properties and the surface morphologies of the failed joints were characterized by a series of methods. The results showed that the corrosive solvents introduced during installation was the root cause of the failure, which was further aggravated by the oversizing and segregation of the filler particles in the rubber and the high crosslinking density of the rubber. Based on these failure causes, countermeasures were proposed to prevent the occurrence of similar failure again.

In this work, the effect of flow oscillations on critical heat flux (CHF) is investigated for water flow in vertical round tubes at low-pressure, low-flow (LPLF) conditions. An experimental study has been conducted to investigate the difference in CHF between forced and natural circulations, and between stable and oscillating flow conditions with three vertical round tube test sections (5.0 mm ID×0.6 m in length, 6.6 mm ID×0.5 m in length, and 9.8 mm ID×0.6 m in length) for mass fluxes below 400 kg m−2 s−1 under near atmospheric pressure. It is found that flow oscillations can drastically reduce the CHF, in particular for natural-circulation conditions. In addition to the experiments, CHF correction factors for flow oscillation effects are developed for forced and natural circulations, respectively, based on the experimental data of the present work and others.

An experimental study on critical heat flux (CHF) and two-phase flow visualization has been performed for water flow in internally-heated, vertical, concentric annuli under near atmospheric pressure. Tests have been done under stable forced-circulation, upward and downward flow conditions with three test sections of relatively large gap widths (heated length = 0.6 m, inner diameter = 19 mm, outer diameter = 29, 35 and 51 mm). The outer wall of the test section was made up of the transparent Pyrex tube to allow the observation of flow patterns near the CHF occurrence. The CHF mechanism was changed in the order of flooding, churn-to-annular flow transition and local dryout under a large bubble in churn flow as the flow rate was increased from zero to higher values. Observed parametric trends are consistent with the previous understanding except that the CHF for downward flow is considerably lower than that for the upward flow. In addition to the experiment, selected CHF correlations for annuli are assessed based on 1156 experimental data from various sources. The Doerffer et al. (1994); Barnett (1966); Jannsen and Kervinen (1963); Levitan and Lantsman (1977) correlations show reasonable predictions for wide parameter ranges, among which the Doerffer et al. (1994) correlation shows the widest parameter ranges and a possibility of further improvement. However, there is no correlation predicting the low-pressure, low-flow CHF satisfactorily.

A mechanistic model to predict a critical heat flux (CHF) over a wide operating range in the subcooled and low quality flow boiling has been proposed based on a concept of the bubble coalescence in the wall bubbly layer. The conservation equations of mass, energy and momentum, together with appropriate constitutive relations, are solved analytically to derive the CHF formula. The model is characterized by an introduction of the drag force due to wall-attached bubbles roughness in the momentum balance, which determines the limiting transverse interchange of mass flux crossing the interface of the wall bubbly layer and core. Comparison between the predictions by the proposed model and the experimental CHF data shows good agreement over a wide range of parameters for both light water and fusion reactors operating conditions. The model correctly accounts for the effects of flow variables such as pressure, mass flux and inlet subcooling as well as geometry parameters.

A feasibility study of multiple alarm processing and diagnosis using neural networks is presented. The backpropagation network (BPN) algorithm is applied to the training of multiple alarm patterns for the identification of faults in a reactor coolant pump (RCP) system. The general mapping capability of the neural network makes it possible to identify a fault easily. A number of case studies are performed, with emphasis on the applicability of the neural network to the pattern recognition of multiple alarms. Based on the case studies, the neural network can identify the cause of multiple alarms well, although untrained, incomplete/sensor-failed or time-varying alarm symptoms are given. Also, multiple faults are easily identified with a given alarm pattern.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A mechanistic modeling of critical heat flux (CHF) in upflow boiling at low qualities is performed. The developed model is based on a physical criterion of CHF occurrence and a mechanism limiting the thermal transport between a stagnant bubbly layer and bulk stream. The mechanism can be mathematically formulated by coupling the equation of limiting mixing mass flux, which is derived from momentum balance equations in two regions, with local mass and energy balance equations on the bubbly layer. The resulting form of the model is represented by a general and straightforward CHF formula involving two empirical constants related to the void fraction and the thickness of the bubbly layer. The predictions agree well with the extensive CHF data of water in uniformly heated tubes.

In this paper, the CHF experiment on the effect of angles and position of mixing vanes was performed in a 2 × 2 rod bundle. The test section had rectangular geometry in which four rod, each with a diameter of 9.5 mm, were inserted. The rod-to-rod gap was 3.15 mm, and the rod-to-wall gap was 1.575 mm. It was vertically installed in the test loop and was uniformly heated by electricity. The heating length was 1.125 m. The working fluid was R-134a. The mass flux ranged from 1000 to 1800 kg/m2. The test pressure ranged from 14.67 to 25.67 bar. CHF data in the 2 × 2 rod bundle without a mixing vane were compared to the Bowring correlation and a CHF look-up table at equivalent hydraulic diameter. For this comparison, Katto's fluid-to-fluid model is applied. The results had a good agreement with error rates of 16 and 20%. In the CHF experiment with the mixing vanes with various angles, the angles of the mixing vanes were 20–40°. The CHF enhancement ratio (CER) was largest at 30°. CHF was enhanced up to 19%. A CHF experiment on the position of the mixing vane was also performed. In the experiment on the position of mixing vane, CER was reduced with increasing distance between grid and CHF location because swirl flow decayed. We also performed the CHF experiment on mixing vane developed by KAIST.

The Monte-Carlo method has been widely used for the analysis of an uncertainty propagation in fault tree analysis. The conventional Monte-Carlo method is time-consuming because of the sorting process. In this study, the Monte-Carlo method without sorting is developed by using the segmentation between the sufficient upper bound and the sufficient lower bound of the evaluated top event frequencies into meshes and interpolation within the mesh. It is shown that the results obtained from the new method are almost equivalent to those from the conventional method, and that the new method reduces greatly the computational running time.

Abstract An experimental study of the critical heat flux (CHF) using R-134a in uniformly heated vertical tube was performed and 182 CHF data points were obtained from the present work to investigate the CHF characteristics of R-134a. The investigated flow parameters in R-134a were: (1) outlet pressures of 13, 16.5, 23.9 bar, (2) mass fluxes of 285–1300 kg/m 2  s, (3) subcooling temperatures of 5–40 °C. The CHF tests were performed in a 17.04 mm I.D. test section with heated length of 3 m. The parametric trends of CHF show a general agreement with previous understanding in the water. To assess the suitability of the CHF test using R-134a for modeling the CHF in water, Bowring correlation and Katto correlation were used in the present investigation. It was found that the present test results coincided well with the data predicted with both correlations. It demonstrates that the R-134a can be used as the CHF modeling fluid of water for the investigated flow conditions and geometric condition.

In the present paper, critical heat flux (CHF) experiments of forced convection boiling were performed to investigate the CHF characteristics of a vertical annular channel with one heated rod and four spacer grids for new refrigerant R-134a. The experiments were conducted under outlet pressure of 11.6, 13, 16 and 20 bar, mass fluxes of 100–600 kg/m2 s, and inlet temperatures of 25–40 °C. The parametric trend of the CHF data was well consistent with previous understanding in water. The comparison between the present results with effect of the flow obstacle enhancing CHF and water data in similar geometry shows R-134a can be a modeling fluid for simulating water CHF in high pressure and high temperature condition even for annular geometry. The direct observation of flowing bubble behaviors contributes to enhancing our understanding on the effect of flow obstacles for flow boiling heat transfer.

Flow instability and critical heat flux (CHF) especially for downward flow of water in a vertical narrow rectangular channel heated from both sides were experimentally investigated. The gap, width, heated width, and heated length of the channel were 2.35, 40, 30, and 350 mm, respectively. The flow boiling was developed as the wall heat flux was increased for the imposed mass flux of 500 and 1000 kg m−2 s−1 for high inlet subcooling (52–74 K) conditions under atmospheric pressure. In this paper, the unstable boiling flow was investigated by monitoring the channel pressure drop and high speed visualization for side view of boiling (HSV-SVB) with the back-lighting method. The results showed that an irremovable pressure drop fluctuation was involved in the flow boiling after the distinct initiating point called as the onset of pressure drop fluctuation (OPDF). We determined that coalescence of bubble (or vapor) layers on opposing heated surfaces triggered the OPDF, since an abrupt increase of pressure drop was occurred as the expansion of the liquid–vapor interface became bounded by the other layer on the opposite side. The fluctuation was amplified as the exit quality was increased and the flow regime passed through the unstable slug or churn flow. For a low inlet throttling condition, premature CHF was induced at the maximum fluctuation during those flow regimes. On the other hand, stable CHF was obtained in the re-stabilized flow regime as the annular flow was developed only for large inlet throttling conditions with an additional pressure drop across the valve of more than 0.4 bar for our experimental configuration.

A series of cinchona alkaloid-ester derivatives was synthesized and applied to catalyze the enantioselective oxaziridination of aryl aldimines with m-CPBA. The (R,R)-oxaziridines were obtained in good yields with high enantiomeric excess (ee) values (up to 98%).

Abstract A rapid, selective, and sensitive ultra‐high performance liquid chromatography‐tandem mass spectrometry method was developed for simultaneous determination of ferulic acid, paeoniflorin, and albiflorin, the major active constituents of Danggui‐Shaoyao‐San, in rat plasma using geniposide as the internal standard. The plasma samples were processed by protein precipitation with acetonitrile, and then separated on a Shim‐Pack XR‐ODS C 18 column (75 mm × 3.0 mm, 2.2 μm) using gradient elution program with a mobile phase consisting of 0.1% aqueous formic acid and acetonitrile at a flow rate of 0.4 mL/min. The detection was achieved on a 3200 QTRAP mass spectrometer equipped with electrospray ionization source in negative ionization mode. Quantification was performed using multiple reaction monitoring mode by monitoring the fragmentation of m / z 192.9→134.0 for ferulic acid, m / z 525.0→120.9 for paeoniflorin, m / z 525.2→121.0 for albiflorin, and m / z 433.1→225.1 for the internal standard, respectively. The calibration curve was linear in the range of 5–2500 ng/mL for all the three analytes ( r ≥ 0.9972) with the lower limit of quantitation of 5 ng/mL. The intraday and interday precisions were below 12.1% for all the analytes in terms of relative standard deviation, and the accuracy was within ±11.5% in terms of relative error. The extraction recovery, matrix effect and stability were satisfactory in rat plasma. The validated method was successfully applied to a pharmacokinetic study of ferulic acid, paeoniflorin, and albiflorin after oral administration of Danggui‐Shaoyao‐San to rats.

The track circuit reader (TCR) is an important part of train control systems. This paper reports a failure of the TCR antenna baffle, which is used to prevent the TCR antenna from being struck by foreign objects. The designed service life of the baffle is 4.8 million kilometers, but serious cracking was found during routine maintenance after only 0.67 million kilometers of operation. In order to avoid the hidden danger brought by the incident to the safe operation of the train, it is necessary to conduct a complete failure analysis of the failed TCR antenna baffle. Therefore, a comprehensive investigation of the base material, cleaning agents, crack morphologies, etc., was carried out, and the failure environment of the antenna baffle was verified by experiment. The final results show that the environmental stress cracking is the root cause of the failed antenna baffle, and the multiple bubbles produced by the formed process of the antenna baffle are another important cause. According to the conclusions, the solutions to prevent the reoccurrence of such failures are proposed. After these solutions are adopted, the number of failed antenna baffles is greatly reduced, which fully proves the correctness of this analysis.