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박경근,유형근,신형식 원광대학교 치의학연구소 1996 圓光齒醫學 Vol.6 No.3
The change in vascular adhesion molecule expression and number of infiltrating leukocytes were investigated immunohistochemically in clinically healthy and inflammed gingiva. Monoclonal antibodies to ICAM-1, VCAM-1 and E-cadherin were used to identify positive vessels and leukocyte within gingival biopsies. 10 healthy gingiva and 30 inflammed gingiva was resected by clinical crown lengthening and modified Widman flap operation, respectively. Leukocyte entry into tissues at sites of inflammation is controlled by the interaction between adhesion molecule and endothelium. Because of rapid and severe destructive periodontal disease that is remarkable leukocyte adhesion deficiency, it is very important to understand the mechanism of host defence against periodontal disease. The purpose of this investigation was the characterization of the presence and distri bution of the adhesion molecule( ICAM-1, VCAM-1 and E-cadherin ) in inflammatory gingival tissues compared to clinically healthy gingiva. The results were as followed; 1. ICAM-1 was distributed on basal layer, endothelium and mononuclear cells in healthy gingiva but inflammed gingiva was observed stronger stain than healthy gingiva. 2. Rare expression was observed in both group but few positive VCAM-l cells were investigated in inflammatory gingival tissues 3. E-cadherin was expressed in only epithelium and reduced expression was obse rved in inflammatory gingival tissues. ICAM-1, VCAM-l showed more expression in inflammatory tissues compared to healthy gingiva. Conversely, E-cadherin revealed a opposite result. These finding demonstrate a characteristic distribution and degree of adhesion molecule in healthy and inflammatory gingival tissues. But it is suggested that more detail study be progressive associated with leukocyte adhesion molecule to determine characterization of periodontal disease.
작동 불가능한 사이클에 대한 거짓 명제를 이용한 Clausius 부등식의 입증
박경근 대한기계학회 2022 大韓機械學會論文集B Vol.46 No.7
A cycle impossible to operate, as in the Kelvin–Planck statement, is analyzed to derive a Clausius inequality for a system that comprises a cycle and a heat-transmitting medium. By denying the validity of the inequality or wrong proposition and applying the concept of a reversible process, a first Clausius inequality for a possible cycle is obtained. Next, by defining the system as the medium and finally as the cycle, similar analysis yields second and third Clausius inequalities. In the Clausius inequalities, there are terms whose denominator represents a temperature of the reservoir or a temperature at the boundary across which heat flows. The temperature and infinitesimal heat transfer specified in the terms are to be defined together at the same location. Kelvin-Planck 서술에서 언급하는 불가능한 사이클을 해석하여, 사이클과 중간물질로 이루어진 시스템에 대한 Clausius 부등식을 유도하였다. 이 부등식, 즉 거짓 명제의 타당성을 부정하고 가역과정의 개념을 적용하여 가능한 사이클에 대한 첫 번째 Clausius 부등식을 얻었다. 중간물질과 사이클을 차례로 시스템으로 정의하고 유사하게 해석하여 두 번째와 세 번째 Clausius 부등식을 얻었다. Clausius 부등식에 들어있는 항의 분모는 열이 전달되는 경계에서의 온도 또는 열저장조의 온도 중 하나가 될 수 있다. 각 항의 온도와 미소 열은 모두 같은 위치에서 정의해야 한다.
박경근,Park, K.,Sonntag, R.E. 대한설비공학회 1995 설비공학 논문집 Vol.7 No.1
The objective of this work is to investigate the form of equations of state for specific refrigerants. In particular, equations of the extended van der Waals form have been studied. As a result, a new equation of state has been developed and tested over ranges of pressure and density up to 5 and 1.5 times critical, respectively. The equation of state separates the compressibility factor into two parts. One is the repulsive compressibility factor and the other is attractive. The former is in the same form of Carnahan-Starling's repulsive term with constant hard-sphere volume. The latter is based on a combination of two different functions linear to density. The equation of state developed here has 12 adjustable parameters and correlates PVT data successfully. All properties are in reduced forms.
순수물질 냉매에 대한 새로운 2변수 증기압 상관식의 개발
박경근 대한기계학회 2022 大韓機械學會論文集B Vol.46 No.8
A new two-parameter correlation equation is developed to calculate the refrigerant vapor pressure. Its performance is compared with that of the existing vapor pressure equations using data for 75 pure substances from the NIST Chemistry WebBook. The new equation yields an average absolute deviation of 0.304% that is compared with those of two-parameter Mejbri-Bellagi (0.478%), two-parameter Riedel (0.496%), RPME (0.669%), Antoine (1.43%), and Kirchhoff (2.94%). The new equation also correlates experimental data for 10 environment-friendly HFO/HCFO refrigerants with the average absolute deviation ranging from 0.063% to 0.371% depending on the accuracy of measurement, span of temperature measured, and degree of consistency among different data sets in the literature. 냉매의 포화 증기압을 계산하기 위한 새로운 2변수 상관식을 개발하였다. NIST Chemistry WebBook에서 취득한 75개 물질의 증기압 데이터를 이용하여 기존의 상관식과 성능을 비교하였다. 평균 절대편차를 기준으로, 새로운 상관식(0.304%)은 2변수 Mejbri-Bellagi(0.478%), 2변수 Riedel(0.496%), RPME(0.669%), Antoine(1.43%), Kirchhoff(2.94%) 등의 상관식보다 성능이 우수하다. 또한, 새로운 상관식을 이용하여 10개의 환경친화적 HFO/HCFO 계열 냉매의 실제 증기압 데이터를 곡선적합하였다. 평균절대편차는 0.063%에서 0.371%로 나타났으며, 이 값은 측정 정확도, 측정 온도 범위, 데이터 집합 간의 상호 일관성 정도 등에 의해 결정된다.
박경근 대한설비공학회 1998 설비공학 논문집 Vol.10 No.4
A header' is the device that makes uniform flow distribution in all branches from header of heat exchangers, pipe burner or chemical equipments. In this study, experimental tests have been performed in order to investigate the flow distribution characteristics in a straight header and tapered header which have 6 and 11 glass pipe branches. The experimental equipment consists of a water circulation system where the fluid velocity in each glass pipe is measured by Ar-ion LDV system. From the experiments and the theoretical equation, it could be recommended that tapered header should be determined so that its internal velocities inside the header become uniform according to taper of the header and number of attached branches for uniform flow distribution in energy systems.
순수물질 냉매에 대한 증발 엔탈피 상관식의 성능비교 연구
박경근 대한설비공학회 2003 설비공학 논문집 Vol.15 No.8
A few commonly used correlation equations of the enthalpy of vaporization are reviewed and a new three-parameter correlation equation is proposed. Performance of the proposed equation is examined using the data listed in the ASHRAE table for 22 pure substance refrigerants. The new equation yields an average absolute deviation of 0.14% for 22 refrigerants, which is better than those of other equations, such as Xiang (0.18%), Major-Svoboda-Pick (0.18%), and Somayajulu equation (0.23%).