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유한 체적법을 이용한 난류 확산 화염에서의 복사 열전달 계산
김승현(S.H. Kim),허강열(K.Y. Huh) 한국전산유체공학회 1997 한국전산유체공학회 학술대회논문집 Vol.1997 No.-
The effects of radiative heat transfer are investigated in a turbulent combustion flow field with highly non-adiabatic flames.Turbulent combustion is modeled by the k-ε-g model and a one step irreversible reaction scheme for the combustion chemistry. The radiative trasport equation is solved by the finite volume method considering the radiative transfer from CO₂, H₂O and soot only. Gray gas is assumed to calculate the radiative properties of CO₂ and H₂O. A two-equation soot formation model is applied to predict soot volume fraction distribution. All equations are solved in a coupled manner and the numerical results are compared with available experimental data.
오토인코더 기반 이상 행동 탐지 시스템에서 3D CNN과 초해상화 기법의 적용 및 성능 분석
전영훈,임현석,곽정환 한국차세대컴퓨팅학회 2022 한국차세대컴퓨팅학회 논문지 Vol.18 No.2
Anomaly detection in video is recognizing an abnormal behavior or situation in frames, and it can be developed as a technology to prevent or respond to accidents. In this paper, we propose a system for detecting anomalies in video using a 3D CNN that learns spatio-temporal features of normal frames and an autoencoder that automatically compresses and restores features. Also, by applying the Image Super Resolution (ISR) technique, which converts a low-resolution image into a high-resolution image, we examined how the performance of the model changes according to the data preprocessing process. The performance of the proposed model was measured using the UCSD dataset and the experimental results show that the 3D CNN-based autoencoder using high-resolution images is superior to other techniques. 비디오에서 이상 탐지(Anomaly detection)란 영상 프레임에서 보이는 비정상(Abnormal)적인 행위 또는 상황을 인식하는 것을 의미하며, 사고를 예방하거나 대응하는 기술로 발전이 가능하다. 본 논문에서는 연속되는 프레임의 시공간적인 특징을 동시에 학습하는 3D CNN과 자동으로 특징을 압축하고 복원하는 오토인코더(Autoencoder)를 활용하여 비디오에서 이상 상황을 탐지하는 시스템을 제안한다. 또한 저해상도(Low Resolution) 이미지를 고해상도 이미지(High Resolution) 이미지로 변환시키는 영상 초해상화(Image Super Resolution, ISR) 기법을 적용하여 모델의 성능이 데이터 전처리의 과정에 따라 어떻게 변화하는지를 살펴보았다. 본 논문은 UCSD 데이터셋을 사용하여 시각적 이상 탐지 성능 비교 실험을 수행하였으며 실험 결과는 고해
김승현,장호명,강병하,Kim, S.H.,Chang, H.M.,Kang, B.H. 대한설비공학회 1997 설비공학 논문집 Vol.9 No.3
A thermodynamic cycle analysis is performed for refrigerator-precooled Linde-Hampson hydrogen liquefiers, including catalysts for the ortho-to-para(o-p) conversion. three different configurations of the liquefying system, depending upon the method of the o-p conversion, are selected for the analysis. After some simple and justifiable models are introduced, a general analysis program to predict the liquid yield and the figure of merit(FOM) is developed with incorporating the commercial computer code for the hydrogen properties. The discussion is focused on the effect of the two primary design parameters-the precooling temperature and the high pressrure of hydrogen. When the precooling temperature is in the range between 45 and 60 K, the optimal high pressure for the maximal liquid yield is found to be in the range between 100 to 140 bar, regardless of the o-p conversion. However, the FOM can be maximized at slightly smaller values of high pressures. It is remarkable to observe that the lower precooling temperatures are favorable since both the liquid yield and the FOM can be obtained without compressing hygrogen to extremely high pressures.
김승현,이성훈,진승헌,Kim, S.H.,Lee, S.H.,Jin, S.H. 한국전자통신연구원 2013 전자통신동향분석 Vol.28 No.3
인터넷을 기반으로 하는 서비스가 활성화됨에 따라, 불순한 목적으로 악용하는 사례 또한 증가하고 있다. 특히 피싱 공격은 사회적인 문제로까지 확대되고 있으며, 대응방안 또한 대국민 교육 차원에서 전달되고 있다. 하지만, 새롭게 등장하는 액티브 피싱 공격은 기존의 대응방안으로는 해결할 수 없으며, 여러 보안 기술을 사용하더라도 해결할 수 없다는 점에서 심각하다. 본고는 액티브 피싱에 대한 소개와 함께, 기존의 대응방안과 여러 보안 기술들의 한계점을 제시한다. 그리고 액티브 피싱을 해결하기 위해 필요한 기술의 요구사항을 고찰한다.
High Dielectric PLZT Thin Films for Embedded Capacitors
김승현,C. Y. Koo,J.-H. Cheon,J. Ha,J.-W. Lee,I.-H. Lee,W. S. Kim,Brian L. Wardle 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.2
For realization of next-generation embedded capacitors in high-density printed circuit boards, a high capacitance density and a low loss of capacitor films are needed. To make reliable capaci- tors, we performed a systematic investigation of the dielectric and the ferroelectric properties of (Pb,La)(Zr,Ti)O3 (PLZT) lms with a LaNiO3 (LNO) buffer layer deposited by a chemical solu- tion deposition method for the rhombohedral (La/Zr/Ti = 7/62/38) composition. The films with a LNO buffer layer on Ni-plated Cu foils showed a very dense and uniform microstructure. The PLZT films were found to a reduced hysteretic behavior, unlike general ferroelectric PZT films. The addition of a high concentration of a La dopant, such as 7 mol%, led to almost no or negligible hysteresis and a low coercive voltage, implying that PLZT with a high concentration of La dopant is a good candidate material for embedded capacitor applications. The capacitance values measured in this experiment were approximately 8 times higher than those of undoped PZT on conventional Ni-plated Cu foils. The capacitance density of the films was approximately 2.4 uF/cm2 and the loss tangent was below 1 %. The results show that PLZT films with an appropriate buffer layer, such as LNO, are strong candidates for high-performance embedded capacitors, providing a possibility of realizing next-generation embedded capacitors with ultra-high capacitance in printed circuit boards. For realization of next-generation embedded capacitors in high-density printed circuit boards, a high capacitance density and a low loss of capacitor films are needed. To make reliable capaci- tors, we performed a systematic investigation of the dielectric and the ferroelectric properties of (Pb,La)(Zr,Ti)O3 (PLZT) lms with a LaNiO3 (LNO) buffer layer deposited by a chemical solu- tion deposition method for the rhombohedral (La/Zr/Ti = 7/62/38) composition. The films with a LNO buffer layer on Ni-plated Cu foils showed a very dense and uniform microstructure. The PLZT films were found to a reduced hysteretic behavior, unlike general ferroelectric PZT films. The addition of a high concentration of a La dopant, such as 7 mol%, led to almost no or negligible hysteresis and a low coercive voltage, implying that PLZT with a high concentration of La dopant is a good candidate material for embedded capacitor applications. The capacitance values measured in this experiment were approximately 8 times higher than those of undoped PZT on conventional Ni-plated Cu foils. The capacitance density of the films was approximately 2.4 uF/cm2 and the loss tangent was below 1 %. The results show that PLZT films with an appropriate buffer layer, such as LNO, are strong candidates for high-performance embedded capacitors, providing a possibility of realizing next-generation embedded capacitors with ultra-high capacitance in printed circuit boards.
김승현(S. H. Kim),심현보(H. B. Shim) 한국소성·가공학회 2012 소성가공 : 한국소성가공학회지 Vol.21 No.8
As the shape of stamped part is complicated and as the trend toward light weight continues, the higher level of difficulty is required in making stamping die because of inevitably poor formability. The poor formability can be improved if the material flow during the stamping is carefully controlled. Application of drawbead became commonsense used to retard metal flow of blank into the die cavity at the region where wrinkle is expected. In the study, the concept of beadless stamping process is proposed and the method how to realize the beadless stamping process is presented. The validity of the proposed method is confirmed by the application of the real auto part.