Alexander Fröhlich

Additive manufacturing is becoming increasingly widespread and has developed very dynamically in recent years. For the processing of metals, powder or wire is usually used as the feedstock. The energy source used in wire-based processes is usually electric arcs or lasers. In this contribution, a technological approach for additive manufacturing of metal structures by induction melting with pulsed generator power is used. Therefore, the principle of oscillating Lorentz forces is utilized in this approach and analytically investigated with the aid of a FE simulation model. In the experiments, a continuously fed steel wire is inductively melted and deposited dropwise onto a substrate heated to different preheating temperatures without the use of a nozzle or crucible.

Both in the reaction K-p→pK−π+π− and in the reaction K−p→pKoπ−πo induced by 10 GeV/c negative kaons on hydrogen, an enhancement is observed in the (Kππ)− effective mass distribution, at mass M = 1789 ± 10 MeV and with full width at half height Γ = 80 + 20−40 MeV. Evidence is presented which is consistent with the interpretation of this enhancement as a resonant state of isospin I = 12, with possible decay modes into Kπ, K∗π and Kω. It is proposed to name this resonance the L-meson.

A study of differential cross sections for 8 GeV/c π+p and 10 GeV/c K−p reactions, treated as two-body processes, has indicated that as the mass M of one of the “bodies” varies, the small angle differential cross section is described by dσ/dt′ = K exp (−At′) for all values of M, whether corresponding to a resonance or to a “background” region. In general, similar values of A are obtained for a resonance region and for its neighbouring mass bands. In most channels, as M increases, the angular distribution becomes broader, namely, A ∝ M−α, with 0 < α < 2.

Results are presented on elastic scattering of 10.1 GeV/c K− mesons on protons, based on a sample of 16 261 kinematically-fitted bubble-chamber events. The differential cross section is given over the |t|- range of 0.06 to 2.5 GeV2 and is fitted with the expressions a ebt, A eBt+Ct2 and (P eQt+ReSt) over various intervals of t. The results are compared with those of other experiments at nearby energies. Upper limits of |α| < 0.28 and σB < 0.4 μb (both at a 90% confidence level) are given for the ratio of real to imaginary part of the forward-scattering amplitude and the backward-elastic-scattering cross section, respectively.

Abstract To date, no AM technology for large-volume metallic components has been established on an industrial scale like Laser Powder Bed Fusion (LPBF). This contribution presents a new process approach to fabricate larger metallic structures from steel by inductive melting of a continuously fed wire. The presented method is characterized by the comparatively low energy input in contrast to comparable processes for AM, such as arc, laser, or electron beam. Previously published work is based on the principle of a melt reservoir of low-melting alloys and droplet delivery using gas pressure or vibration. In contrast, the approach described here is to transfer the material directly from the end of the wire to the substrate by continuous drop deposition. However, to avoid a stochastic material transition, a suitable process strategy has to be chosen. This challenge is met by a pulsed coil current and the resulting periodically varying Lorentz forces in order to achieve regular and forced droplet detachment. Tests confirm the principle of controlled droplet detachment and reveal the great potential of this technological approach.

K∗ and K∗ (1420) resonances are observed in 10 GeV/c K− p interactions. Masses, widths and cross sections are determined. Decay angular distributions and differential cross sections of K∗ (890) production are compared with the absorption model and Regge pole model. While at lower energies the absorption model predictions are in reasonable agreement with experiment, serious disagreement is observed at 10 GeV/c. Regge pole calculations including exchange of P, P′. π. ϱ. ω and A2 trajectories can fit the data but do not explain why π exchange dominates K∗0(890) production while ω exchange dominates K∗−(890) production.

Two (Kππ) enhancements called K∗(1320) and the L-meson are observed in 10 GeV/c K−p interactions, with masses of (1325±6) and (1785±12) MeV and widths of (186±15) and (127±43) MeV, respectively. A peak near 1790 MeV is also observed in the (Kπππ)− mass distribution. Evidence for a (Kω) decay mode of the L-meson is presented. It is shown that the K∗(1320) peak is not a kinematic effect of the Deck-type. A maximum likelihood analysis of the (Kππ)− channels indicates that the favoured spin-parity assignment for K∗(1320) is JP = 1+ (with 2− less probable) and for the L-meson JP = 1+, 2−, 3+3.. Decay branching ratios into (Kππ), Kϱ, K∗(890)π and K∗(1420)π are also obtained for both resonances, as well as their production cross sections. Arguments are given to prove that the isospin of both resonances is I = 12. All the results are consistent with the interpretation that these resonances are produced by Pomeron exchange. A quark-model speculation leads to a classification of the L-meson as belonging to a nonet with C = −1, probably 3D2 or 1F3 in spectroscopic notation.

The contribution to the reaction K−p→pK−π+π− due to pomeron exchange is studied, assuming that the system (pomeron + mesons) is described by a dual five-point Veneziano-type amplitude. The calculations are compared with the experimental results at 10 GeV/c and good agreement is obtained for the Kππ mass distribution, the t-dependence of the differential cross section and the Dalitz plots for the Kππ systems in the mass regions of the Q- and L-mesons.

Abstract The five-point function Veneziano model has been applied to the reaction K − p → p K 0 π − in the energy range from ≈ 3 to 10 GeV/c. The predictions of the model are shown to be sensitive to the choices made for the assumptions and the parameters involved in the expression of the amplitude. Several choices can be made that give a satisfactory general description of this reaction. However, the mass spectra are not described in detail and the differential cross sections do not have the correct t-dependence, especially at the lower energies. These difficulties derive mostly from the fact that the simple model used does not consider the possibility that more than one trajectory is exchanged between a pair of particles.

A hybrid technology of inductive contact joining (ICJ) was developed to join fibre-reinforced thermoplastics (FRP) with metals by using a tool with single-sided heating. In comparison to conventional methods with separate heating, pressing and cooling, the unique new hybrid ICJ process is characterized by combining all three steps into one hybrid process. The maximum temperature is shifted toward the joining zone due to the direct cooling effect of the surface. FE simulations showed the temperature distributions within the joint. The performed experiments provided data for the temperature profile of the process and the resulting strength of the joint, type of damage and microstructural characteristics. Proven advantages include very short cycle time, competitive joint strength and limited influence on the mechanical properties of the metallic component.

The reaction K−p→Q−p→p(K−K−π+π−) at 8.25 GeV/c favours t-channel helicity conservation over s-channel helicity conservation. This is shown by comparing the Q density matrix elements with the predictions of the above two hypothesis as functions of the crossing angle.

Innovative packaging techniques are essential for the development of new microsystems. To integrate different materials into one package, the thermal stress on the devices has to be minimized. This paper presents a method for selective and energy-efficient induction heating of Cu-Sn layers to support and enhance the bonding process at wafer-level. Technological challenges include the inductor design for homogeneous heating, the use of high-frequency electromagnetic fields up to frequencies of f = 2.0 MHz, and the integration of the induction equipment into an industrial wafer bonder. Infrared thermography imaging was used to characterize the selective heat generation with very fast heating rates of ΔT > 150 K/s. Consequently, the wafer bonding process could be performed in t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bond</sub> = 120.0 s by applying a low pressure of p = 2.2 MPa.

A 4.1 event/nb sample of 11 GeV/c K−p interactions in the LASS spectrometer at SLAC has been used in an analysis of the exclusive Ks0Ks0Λ final state. The Ks0Ks0 mass distribution exhibits a small cluster of events near threshold, but the mass spectrum is dominated by the f2′(1525), which an amplitude analysis shows to be produced by both natural and unnatural parity exchange. This analysis also provides evidence for an S-wave state in the f2′(1525) region, while production of the f2(1720) is not observed. However, there is structure at ∼ 2.2 GeV/c2 which is similar in shape to that observed in the region of the X(2220) in radiative J/ψ decay; an analysis of the angular distribution indicates a spin of at least 2 in this region. This, together with results from other analyses, indicates that the X(2220) may be the 2++ or 4++, mainly ss, state expected near this mass in the conventional quark model.

Sustainable manufacturing technologies as well as lightweight and multi-material design in production have become key factors for success in industrial sectors such as transportation, automotive production or aerospace. Therefore, an automatable hybrid joining technology is required with a high industrial output. Mechanical, chemical and thermal technologies can be applied to join fiber-reinforced thermoplastics (FRP) with metals. The advantage of induction heating as a thermal joining process is the immediate generation of heat inside the electrically conductive material at the joining surface. Due to the direct conversion of electricity into heat the joining process can be emission-free if the energy is produced by regenerative sources. However, the distance between coil and joining partners, the transport of the workpiece to the pressing tool and the subsequent separate cooling in conventional inductive joining methods reported in the literature result in power losses and extended process times. The unique new hybrid inductive contact joining (ICJ) process is characterized by the integration of heating, pressing and cooling into one hybrid process step which is performed by one tool. The conducted experiments and finite element simulations provide data for the main process parameters during joining, joint strength as well as the impact of surface preparations and demonstrate the advantages of the ICJ process in comparison with conventional thermal joining processes.

Production of Ξ−, Ω− and antibaryons has been studied in 10 GeV/c K−p interactions. The Ξ∗(1530) is produced in about 15% of the reactions with Ξ− production. Four unambiguous examples of Ω− production with decay into (ΛK) have been observed: this gives a lower limit for the Ω− production cross section of 2.5 μb. One example of anti-Xi has been found. Distributions and average values of transverse and c.m. longitudinal momenta are presented.

This paper presents the development and successful application of an inductive preheating system running simultaneously with the manual laser cladding process in order to enable the repair of high-alloy tool steels having a highly limited weldability. In this study, the design and optimization of a suitable inductor as well as the analysis of the welding process were carried out by means of FE-simulation in order to generate material deposition without imperfections. Parameter variation studies were conducted while parallel modifying the generator power resulting in different preheating temperatures. These examinations showed that by using appropriate process parameters and an inductive preheating temperature of 200 °C, crack- and pore-free deposition layers could be produced on the commercial high-alloyed PM steel Elmax. This result can be explained by FE-simulation demonstrating that the cooling rate was halved in the weld and in the heat-affected zone. In conclusion, this study shows the high potential of the developed technical innovation for the manual laser cladding of high-performance tools.

It has been suggested that the (Kππ) enhancement observed near 1780 MeV, the L-meson, can be explained as a threshold enhancement in the K∗ (1420)π system. Here quantitative evidence is presented from 10 GeV/c K−p interactions to show that this is not so and that the L-enhancement must have decay modes other than K∗ (1420)π.

The measurement of small direct currents in presence of high AC currents on high voltage potential is a challenging task. Inductive current transducers (CT) are not able to measure DC and other non-conventional CTs are also not designed for DC. Therefore, DC measurements are done in transformer neutral points on ground potential. In this work, the state of the art on DC measurements in the high-voltage transmission grid is given, including the measurement in the transformer neutral point, the indirect measurement with the differential magnetometer method, and the indirect method of measuring a compensating current. In addition an optical current measurement system under development is presented.

Antinucleon-nucleus annihilations into two-body final states containing only one or no meson are unusual annihilations (Pontecorvo reactions), practically unexplored experimentally, with the exception of the channel p d → π− p, for which only two low-statistics measurements exist. Their physical interest lies in the possibility of exploring small-distance nuclear dynamics, in which an important role can be played by non-nucleonic degrees of freedom. A new measurement of the p d → π− p reaction rate at rest, performed with the OBELIX spectrometer at LEAR, with the best statistics up to now and a careful evaluation of systematic effects is reported, together with a critical analysis of the existing theoretical models. The measured branching ratio, which confirms the previous results, can represent a reference point for the studies in the field.

The generalized Veneziano model is applied to the reaction K−p→nK−π+ at 10 GeV/c. This reaction requires facing two of the major difficulties of the model, namely (i) pomeron exchange, (ii) dominant contribution of pion exchange, with possibility of some vector-meson contribution. The analysis is made first without pomeron exchange on a subset of the events, then on all events, with pomeron exchange included. It is found that though pion exchange is the dominant process, satisfactory descriptions of differential cross sections and longitudinal momentum distributions are obtained only when a contribution of about 15% from vector-meson exchange is included. Pomeron exchange, when considered, contributes about 25% of the cross sections. Most of the experimental distributions at 10 GeV/c are satisfactorily described, but the predicted variation of the cross section with incident momentum is different from experiment, indicating that the model, as employed, still has some difficulties.

Bulletin of the London Mathematical SocietyVolume 9, Issue 2 p. 219-232 ObituaryFree Access Hans Arnold Heilbronn J. W. S. Cassels, J. W. S. CasselsSearch for more papers by this authorA. Fröhlich, A. FröhlichSearch for more papers by this author J. W. S. Cassels, J. W. S. CasselsSearch for more papers by this authorA. Fröhlich, A. FröhlichSearch for more papers by this author First published: July 1977 https://doi.org/10.1112/blms/9.2.219Citations: 2 This obituary has previously appeared in the Biographical Notices of the Royal Society. It was prepared by Professor J. W. S. Cassels and Professor A. Fröhlich, and we are grateful for permission to reproduce it. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume9, Issue2July 1977Pages 219-232 RelatedInformation

The construction of a cosmic-ray spark-chamber spectrometer for use in the study of the charge ratio and interactions of muons at energies up to 3 000 GeV is proposed. The apparatus will consist of a stack of interleaved spark chambers and magnetized iron plates, placed at a depth of 250 m.w.e. underground in order to remove the low-energy component of the cosmic-ray muon flux. This report gives an appraisal of the design of the apparatus and summarizes its expected performance.

An important question in education nowadays is how to convey some concepts of Modern Physics to students in high school, secondary education or the sixth form. This article presents an approach to atomic collisions suitable for intermediate level students. We describe an alternative way of measuring the area of a coin using a macroscopic analogy of the scattering of radiation by an atom or molecule - the collision cross section. We hope this article will help educators to illustrate such an important procedure and related concepts of Modern Physics.

We propose a new color filter array for hexagonal sampling grids and a corresponding demosaicking algorithm. By exploiting properties of the human visual system in their design, we show that our proposed color filter array and its demosaicking algorithm are able to outperform the widely used Bayer pattern with state-of-the-art demosaicking algorithms in terms of both, objective and subjective image quality.

Methods of analysing the data from magnetic spectrometers are examined. The effects of Coulomb scatter counter efficiencies and assumed spectrum exponent on the observed spectra are considered, and how they might be incorporated into the analytic methods used for correcting the measured muon flux and charge ratio.

Discrepancies have been found in the signal to noise ratio of pulse height spectra of muons in scintillation counter that were measured by different methods. These arosc from the different shapes of pulses from the photomultiplier's intrinsic noise and from the actual scintillation pulses.

Die Arbeit beschaeftigt sich mit dem oeffentlichen und privaten Verkehr im staedtischen Bereich und seinen Kostenauswirkungen auf die Umwelt und die Gesellschaft. Es besteht kein sofort abrufbares Wissen ueber Hoehe und Zugehoerigkeit von Kosten, welche bei der Verkehrsnutzung im staedtischen Raum auftreten. Das Ziel der Arbeit ist es, darzustellen welche Kosten aufgrund der Verkehrsmittelwahl im staedtischen Bereich fuer Umwelt und Gesellschaft anfallen. Damit sind jene Kosten der oeffentlichen Hand, in Verkehr und Umwelt sowie Kosten fuer Private Haushalte gemeint. Wichtige Fragen sind: Welche Kosten entstehen durch welches Verkehrsmittel? Welche anderen negativen Auswirkungen fuer Gesellschaft und Umwelt entstehen durch welches Verkehrsmittel? Zuerst erfolgen eine Erfassung der derzeitigen Lage mithilfe von Internetrecherche und Anfragen bei Verkehrsbetrieben sowie eine Darstellung der derzeitigen Auswirkungen. Danach werden die direkten sowie indirekten Kosten fuer Umwelt und Gesellschaft aufgrund derzeitiger Preise von Material, Herstellung und Betrieb ermittelt und aufgegliedert. Die Kostenermittlung beruht auf Informationsabfrage bei fuer diese Kosten zustaendigen oder ueber die Kosten informierten Stellen. Die Aufgliederung der Kosten erfolgt geordnet nach Art der Kosten und nach Verkehrsmittel. Dann werden Verbesserungsmoeglichkeiten, die Kosten betreffend, aus den Ergebnissen abgeleitet. Aus der Arbeit wird ersichtlich, dass oeffentliche Verkehrsmittel und die Benutzung des Fahrrads aehnlich hohe Kosten verursachen und die guenstigsten Verkehrsmittel sind. Der motorisierte Individualverkehr (MIV) ist um das vier- bis siebenfache teurer als andere Verkehrsmittel. So fallen fuer einen Kilometer zurueckgelegte Strecke je Person mit dem Bus Kosten von 0,09 Euro, mit der Bahn 0,16 Euro, mit MIV 0,47 Euro und mit dem Fahrrad 0,1 Euro an. Die Schlussfolgerung lautet, dass der MIV in jeder betrachteten Kategorie das fuer Gesellschaft und Umwelt nachteiligste Verkehrsmittel ist und nach Moeglichkeit eine Alternative genutzt werden sollte. (A) (Reihe Gesellschaftswissenschaften.)

Durch den Einsatz Interaktiver Bildschirmexperimente (IBE) verfolgen wir das Ziel, reale Experimente sinnvoll zu erganzen. Eine Moglichkeit dazu besteht in der Dokumentation von Experimenten, die aus praktischen Grunden nicht zur Verfugung stehen. Anhand des Beispiels des Virtuellen Forschungslabor Femtochemie wird gezeigt, wie sich die komplexe Realitat eines Forschungslabors didaktisch aufbereiten und mit Realexperimenten verknupfen lasst.

Considering the demand for low temperature bonding processes in packaging of micro-electro-mechanical systems (MEMS), such as accelerometers or micro mirrors, in this paper a method for selective and energy-efficient heating of metallic intermediate bonding layers by applying high-frequency electro magnetic fields with frequencies in the range of 1. 0 < f < 2.0 MHz is presented. Therefore, the induction heating process was modeled and analyzed by means of numerical simulation. Additionally, heating experiments were carried out by using IR thermography in order to verify the simulation results. The developed inductor shape allows almost homogeneous heating of all metallic layers with heating rates of more than ΔT∕Δt = 150 K∕s.

In this paper, the new process of inductive contact (ICJ) for the production of hybrid material composites is introduced and the results of investigations using glass and carbon fiber reinforced polyamide matrix composites are presented. Finite element simulations as well as joining experiments were conducted.

High resolution optical power spectra of Cygnus X-1 were measured in 1973 October. No evidence for any coherent oscillations was found. The attainable sensitivity closely approached the theoretical predictions for the optical conversion of the known X-ray shot noise.