S. Cho

베스트셀러 도서는 독자들이 책을 선택하는 가장 보편적인 방법이며, 이러한 이유로 베스트셀러의 예측과 선정은 출판 시장에서 중요한 마케팅 전략 지표이다. 본 연구에서는 도서의 메타 데이터를 활용하여 베스트셀러 순위 200위 내 유지 여부와 판매 지수 구간을 예측하는 모델을 제안하고, 다양한 머신러닝 알고리즘의 성능을 비교평가하고자 한다. 이를 위하여 Yes24 사이트의 월간 베스트셀러 데이터를 크롤링하여 수집하고, 각 데이터 속성에 대해 적절한 전처리를 수행하였다. 순위 유지 여부 예측을 위해 다양한 분류 알고리즘을 활용하였고, 최종적으로 각 알고리즘의 예측 성능을 평가한 결과, 다중 퍼셉트론, CatBoost, 랜덤 포레스트의 순서로 정확도가 높게 나타났다. 본 연구는 베스트셀러 순위 유지 여부 예측 문제에 대해 주요 분류 알고리즘의 수행 성능을 종합적으로 비교했다는데 의미가 있다. 그러나 한계점으로 리뷰 수, 평점 등에 의존하는 예측 방법에서는 데이터가 부족한 신간 도서에서 cold start 문제를 극복하기 어려웠으며, 이에 대한 후속 보완 연구의 필요성을 제안한다.

The Biograph Vision, developed by Siemens Healthineers, is regarded as the gold standard for time-of-flight (TOF) performance in clinical positron emission tomography (PET) imaging. When comparing new multi-channel readout circuits, it is essential to account for potential disparities in material and assembly of custom detector blocks. This ensures that the sole influence of readout electronics on timing performance can be accurately assessed. In this context, we evaluate the TOFPET2 ASIC, designed by PETsys Electronics S.A., in conjunction with a Biograph Vision detector block. We examine the coincidence time resolution (CTR) and energy resolution. Furthermore we evaluated the scintillator for DOI capabailities, not available in the clinical product, using the channel-individual readout capabilities.

Previous studies showed that reactive ion beam (RIB) pretreatment of sapphire prior to GaN deposition results in the reduction of dislocation density in the GaN film. It was also found that an amorphous phase remained at the interface region after the GaN deposition at high temperature. Annealing was performed to obtain the structural change due to the recrystallization of the remaining amorphous phase, and the effect on the electrical properties of the GaN thin film on RIB treated sapphire (0001) substrate. DCXRD spectra and Hall mobility of the specimen were studied as a function of the annealing time at 1000 °C in N2 atmosphere. For the annealed specimen, FWHM of DCXRD decreased and the mobility increased. The annealed specimen was compared with a not annealed sample by TEM. A decrease of lattice strain and a reduction of the dislocation density about 56–59% was observed. The present results clearly show that the combination of RIB pretreatment and proper post annealing conditions improve the properties of GaN films grown by MOCVD.

Previous studies showed that reactive ion beam (RIB) pretreatment of sapphire prior to GaN deposition results in the reduction of dislocation density in the GaN film. It was also found that an amorphous phase remained at the interface region after the GaN deposition at high temperature. Annealing was performed to obtain the structural change due to the recrystallization of the remaining amorphous phase, and the effect on the electrical properties of the GaN thin film on RIB treated sapphire (0001) substrate. DCXRD spectra and Hall mobility of the specimen were studied as a function of the annealing time at 1000 °C in N2 atmosphere. For the annealed specimen, FWHM of DCXRD decreased and the mobility increased. The annealed specimen was compared with a not annealed sample by TEM. A decrease of lattice strain and a reduction of the dislocation density about 56–59% was observed. The present results clearly show that the combination of RIB pretreatment and proper post annealing conditions improve the properties of GaN films grown by MOCVD.