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Szilard's Information Heat Engines in the Deep Quantum Regime
김강환,김상욱 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.8
We investigate Szilard's information heat engine in the deep quantum regime. If the ground state is non-degenerate, the work extracted from the engine divided by temperature, <i>S</i>, vanishes as the temperature approaches zero, where the third law of thermodynamics manifests itself in information science. The degenerate ground state induced by the symmetry or by accident gives rise to non-zero <i>S</i> at zero temperature. Based upon these two rules, namely the third law and the degenerate ground state, we can understand the low-temperature behavior of the quantum Szilard engine in various physical situations such as an engine consisting of either bosons or fermions either with or without interactions.
김강환,김원진 한국음향학회 2020 韓國音響學會誌 Vol.39 No.2
A method to reduce the Contraction and Expansion (CE) noise occurred in an air conditioner is investigated. The noise is measured during the cooling and heating phases in a temperature and humidity chamber to identify the generating phenomenon of CE noise of the air conditioner and the decomposition method is used to estimate its occurrence location. The CE noise of an air conditioner is known to be caused by a stick-slip phenomenon generated by joints of parts connected to the lower decor. Thus a friction experiment was conducted to investigate noise inducing factors. Also, this study established evaluation criteria to effectively analyze the results from friction experiments. Experimental results indicate that increasing surface roughness on both sides of joints is effective. Accordingly, the effect of increased surface roughness on joints of upper and lower decor of air conditioners is evaluated to see its feasibility in a temperature and humidity chamber. 에어컨 운전 중에 발생하는 실내기의 수축팽창 소음 현상을 분석하고 , 발생위치를 평가한다. 그리고 마찰실험 을 통하여 수축팽창 소음을 유발하는 인자를 규명하고자 한다. 먼저 항온·항습챔버에서 운전 환경 조건별로 수축팽창 소음의 발생횟수 및 특성을 분석하고, 분해법을 이용하여 냉방 및 난방 시 모두 하부 데코에서 발생하는 것을 확인하였 다. 실내기에서 발생하는 수축팽창 소음은 하부 데코와 연결되는 부품들과의 체결부에서 발생하는 스틱슬립 현상에 의한 것으로 이러한 소음을 유발하는 인자를 규명하기 위하여 마찰실험을 진행하였다. 또한 마찰실험 결과의 효과적 분석을 위하여 십점평균 산출법을 도입하고, 실험 결과에서 Acrylonitrile Butadiene Styrene(ABS) 재질 간에 접촉하 면 스틱슬립 현상을 유발하며 체결부의 양면에 표면조도를 증가하는 것이 소음저감에 효과적임을 확인하였다.
자체 개발한 하악거상 기구를 활용한 소아 REVERS WATER'S View의 유용성
김강환,손순룡,김광수,홍선숙,이관섭,Kim, Kang-Hwan,Son, Soon-Lyong,Kim, Kwang-Soo,Hong, Sun-Suk,Lee, Kwan-Sup 대한디지털의료영상학회 2013 대한디지털의료영상학회논문지 Vol.15 No.2
This study is to provide clinical data when reverse-water's-view was carried out about pediatric who did not communicate by applying self-development jaw lift tool. This study were conducted in a subject of 23 children who examined revers-water's-view from 2013 July 6 to 2013 August 5 at our hospital. Two group time which were carried out revers-water's with tool and without tool were measured. also, Image of two group were evaluated. Evaluation data obtained by measuring the average difference were analyzed by independent-t-test. After apply self-development-jaw-lift-tool, time was reduced by 35.2%(36.6sec). the results indicated significant differences(p< .05). Image evaluation was increase 43.5%(1.03point), It was statistically highly significant difference (p< .01). If apply self-development-jaw-lift-tool in pediatric revers-water's-view, operator can provide fast, convenience, high quality image to pediatric.
조화진동 난류 예혼합 화염의 운동학: DNS 기반 수소 혼소 화염
김강환(Kanghwan Kim),김용제(Yong Jea Kim),신동혁(Dong-hyuk Shin) 한국연소학회 2022 KOSCOSYMPOSIUM논문집 Vol.2022 No.5
This paper uses direct numerical simulation (DNS) to characterize the kinematics of ensemble-averaged flame position in harmonically oscillating turbulent premixed flames. The flames are stabilized on a harmonically oscillating flame holder. The fuel consists of methane and hydrogen at volume ratio 10:3, and is mixed with air at the stoichiometric ratio. The flame with 4% turbulence intensity is simulated for 20 forcing periods for ensemble averaging. Instantaneous flame positions are extracted from iso-contours of a fixed temperature of 1178 K, which represents the reaction zone. The instantaneous flame positions are then averaged over the same phase of the forcing period. The turbulent flame speed and ensemble-averaged flame position. The turbulent flame speed shows strong linear correlation with the ensemble-averaged flame curvature, if time delays are applied. The ensemble-averaged tangential velocities and normal velocities are shown to correlate with the spatial derivative of the ensemble-averaged flame position with exponential functional shapes.
저압 환경에서의 공력시험을 위한 폐쇄형 소형 풍동의 설계 파라미터 분석 및 전산 해석
김강환(Kanghwan Kim),신지철(Jichul Shin) 한국전산유체공학회 2019 한국전산유체공학회지 Vol.24 No.3
Design parameters for wind tunnel facility aimed for low pressure aerodynamic testings was investigated by two dimensional numerical simulation using a Fluent software. The number of corner vanes before the contraction part showed the most noticeable changes in the flow uniformity at the test section. With 20 corner vanes, span-wise symmetry became worse as the length ratio of the contraction part decreased, while the velocity distribution exhibited the best uniformity when the length ratio was 40%. As the diverging angle of the divergent part after the fan decreased from 3 degree to 2 degree, the flow uniformity was degraded. It turned out that a density change due to the altitude change does not affect the boundary layer profile.
학교(學校) 교실(敎室)의 실내환경(室內環境) 실태(實態) 조사(調査) 연구(硏究)
김강환(Kim, Kang-Hwan),이현영(Lee, Hyoun-Young) 한국교육시설학회 2000 敎育施設 Vol.7 No.3
The purpose of this study is to analyze the environmental characteristics of Hansung Girls' Middle & High School located on the northern slope of Mt. Naksan in Seoul but sited at different aspects. The measured temperature and illumination in March, July and December were analysed. The proportion of window size and questionaries were used also. The results of observation are as follows: (1) The temperature of the southward classrooms was higher than eastward or westward classrooms in March, but the difference of the both values in July were only in the average. (2) The temperatures in December decreased in the order of aspects: southward, westward and eastward. (3) The highest values for illumination appeared in the classroom faced to the south and the values decreased from westward to eastward. (4) Temperatures and illumination were varied not only with the aspect but also with the number of story and the proportion of the window size. However, the heating facilities and illuminators are installed evenly without considering the condition of the buildings. The heating facilities should be installed differently according to the direction and height of the story of the building. The heating facilities should be installed sparsely for the classrooms faced southward, and more densely near the hallway side to achieve satisfaction of students and to save expenses of heating. It will be better that electric power switches for window side have to be set separately from hallway side. Improvement of the condition of illumination and temperatures will help students to promote their health and learning.