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정재동(Jae Dong Chung) 대한설비공학회 2010 설비공학 논문집 Vol.22 No.7
paper deals with approximate integral solutions to the one-dimensional model describing the charging process of stratified thermal storage tanks. Temperature is assumed to be the form of Fermi-Dirac distribution function, which can be separated to two sets of cubic polynomials for each hot and cold side of thermal boundary layers. Proposed approximate integral solutions are compared to the previous works of the approximate analytic solutions and show reasonable agreement. The approach, however, has benefits in mathematical difficulties, complicated solution form and unstable convergence of series solution founded in the previous analytic solutions. Solutions for a semi-infinite region, which have simple closed form solutions, give close agreement to those for a finite region. Thermocline thickness is obtained in closed form and shows proportional behavior to the square root of time and inverse proportional behavior to the square root of flow rate.
정재동(Jae Dong Chung) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Molecular Dynamic Simulation has been conducted for the melting process of Ar and the effect of defect on the melting temperature was examined. Drastic change of volume and energy is expected to be involved with phase change. In pure crystal, hysteresis is found due to the superheating and supercooling, but a defect decreases the superheating. Asymptotic behavior is found as the strength of defects increases the temperature where the volume changes drastically approaches to the experimental value of melting temperature. Thus the melting point can be expected by observing the change of drastic volume change.
정재동(Jae Dong Chung) 대한설비공학회 2007 설비공학 논문집 Vol.19 No.12
As a starting point of investigating what molecular dynamic simulations can reveal about the nature of atomic level of heating and cooling process, argon described by the LJ potential is considered. Stepwise heating and cooling of constant rates are simulated in the NPT (constant number, pressure and temperature) ensemble. Hysteresis is found due to the superheating and supercooling. Drastic change of volume and energy is involved with phase change, but the melting point can not be obtained by simply observing the changes of these quantities. Since liquid and solid phases can co-exist at the same temperature, Gibbs free energy should be calculated to find the temperature where the Gibbs free energy of liquid is equal to that of the solid since the equilibrium state is the state of minimum Gibbs free energy. The obtained melting temperature, T = 0.685, is close to that of the experiment with only 2% error.
바닥공조시스템에서 복사온도가 열적 쾌적성에 미치는 영향
정재동(Jae Dong Chung),홍희기(Hiki Hong),유호선(Hoseon Yoo) 대한설비공학회 2008 설비공학 논문집 Vol.20 No.11
Despite the fact that UFAD(Under Floor Air Distribution) systems have many benefits and are being applied in the field in increasing numbers, there is a strong need for an improved fundamental understanding of several key performance features of these systems. This study numerically investigates the effect of supplied air temperature and supplied flow rate on the performance of UFAD, especially focused on thermal comfort. Also this study has compared UFAD with conventional overhead air distribution system. In contrast to the well-mixed room air conditions of the conventional overheat system, UFAD system produces an overall floor-to-ceiling airflow pattern that takes advantage of the natural buoyancy produced by heat sources in the occupied zone and more efficiently removes heat loads and contaminants from the space. Thermal comfort parameters were evaluated by CFD approach and then PMV was computed to detect the occupants' thermal sensation. Results show that radiative mean temperature plays crucial role on the evaluating PMV. Until now, the radiative temperature has been the missing link between CFD and thermal comfort, but the present study paves the way for overcoming this weakness.
전립선 배아기상호유도작용 재활성의 원인 1: 만성 염증
정재동(Jae Dong Chung),최세영(Se Young Choi),이상협(Sang Hyup Lee),명순철(Soon Chul Myung) 대한비뇨기종양학회 2012 대한비뇨기종양학회지 Vol.10 No.1
Traditionally, androgens and ageing have been considered confirmative main factors of prostate enlargement. McNeal noted that the proliferation closely resembled developmental differentiation and posited that epithelial hyperplasia may be the result of reactivation of embryonic pathways. He postulated that the combined stromal and ductal hyperplasia in aging men resulted from a re-awakening of these mesenchymal-epithelial inductive interactions. Latest years, acute and chronic inflammation of the prostate and decreasing testosterone levels may important in the aging related re-awakening. So aim of this article is to provide a review of the role of chronic inflammation in benign prostate hyperplasia.