• Elastomers and Composites
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• v.7 no.1
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• pp.53-58
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• 1972

Sublimatographic study on the method of test for sulfur in the petroleum and rubber products was as following results: (1) The relation between the heating temperature$(t_h)$ and the vacuum condensing point(V.C.P.) of sulfur at different degree of vacuum appeared as Fig.4. The results were in good agreement with those expected from the $t_h-V.C.P$ curves of sublimatographic separation of sulfur. (2) The relation between the degree of vacuum and the V.C.P. at different heating temperature of sulfur appeared as follows; $$tv.c.p.=\alpha+{\beta}logP_{va}$$ (3) The V.C.P of sulfur could be physical property comparing with melting point and boiling point. (4) The relation between the V.C.P. and the quantity of sublimation of sulfur becomes quantitative as Fig.7.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.963-966
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• 2009

A Construction of pipe line foundation and railroad, buildings in a permafrost area requires engineering technology of ground stabilization. In the permafrost area, thermal siphons have been used to stabilize foundation by eliminating the heat of ground to the air. the thermal siphon is a passive heat transfer device that operates by convection through vaporization and condensation. The heat transfer from ground to the air is driven by a temperature difference across the unit. A buried part in ground working as vaporizing function and upper part work as condensing. In this study, buried thermal siphon around the pipe lines laid in the Vladivostok site and measuring temperature variation. It is found that the thermal siphons freezing ground faster and decrease temperature variation in winter season.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1458-1463
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• 2004

By using unique experimental techniques and careful construction of the experimental apparatus, the characteristics of the local heat transfer were investigated using the condensing R134a two-phase flow, in horizontal single mini-channels. The circular channels ($D_h=0.493$, 0.691, and 1.067 mm) and rectangular channels ($D_h=0.494$, 0.658, and 0.972 mm) were tested and compared. Tests were performed for a mass flux of 100, 200, 400, and 600 $kg/m^2s$, a heat flux of 5 to 20 $kW/m^2$, and a saturation temperature of $40^{\circ}C$. In this study, effect of heat flux, mass flux, vapor qualities, hydraulic diameter, and channel geometry on flow condensation were investigated and the experimental local condensation heat transfer coefficients are shown. The experimental data of condensation Nusselt number are compared with existing correlations.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.7
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• pp.362-368
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• 2015

This paper presents a numerical study on the performance of a vapor compression cycle equipped with an ejector as an expansion device to improve the COP by reducing the expansion loss and compressor work. The simulation is carried out using a model based on the conservation of mass, energy and momentum in the ejector. From the results of the simulation, the vapor compression cycle equipped with an ejector showed a maximum COP improvement of 14.0% when using R134a refrigerant and 16.8% when using R1234yf. In addition, the performance of the system with an ejector represents the increased performance as the temperature difference between condensing and evaporating increased.

• International Journal of Air-Conditioning and Refrigeration
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• v.13 no.3
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• pp.119-127
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• 2005

Liquid pressure amplifiers have been proposed as an energy saving technology for vapor compression refrigeration systems configured with direct-expansion evaporators. The technology utilizes a refrigerant pump in the high pressure liquid line as a means of maintaining a suitable pressure differential across the expansion valve while lowering condensing pressure to achieve the reduction of compressor energy consumption. Applications have been proposed on systems ranging from small unitary air-conditioning to large supermarket and commercial refrigeration systems. This paper clarifies the role of such a device in a vapor compression refrigeration system. Limitations are presented and discussed. Finally, results of detailed analyses are presented to quantify the energy consumption both with and without a liquid pressure amplifier in a unitary air conditioning system. The estimated energy savings associated with the installation of a liquid pressure amplifier are minimal.

• Bulletin of the Korean Chemical Society
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• v.30 no.1
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• pp.83-91
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• 2009

To develop new anticancer agents, 3-allylthio-6-aminopyridazine derivatives were synthesized from maleic anhydrides or phthalic anhydrides by formation of a pyridazine nucleus, dichlorination, allylthiolation and amination. The pyridazine nuclei were obtained by condensing a hydrazine monohydrate with maleic anhydride. An allylthio group as a pharmacologically active group was introduced into one side of a pyridazine ring. Arylalkylamines with benzene or pyridine moieties or heterocycloalkylamines with heterocycle moieties such as morpholine, piperidine, or pyrrolidine were also introduced into the para-position of allylthio pyridazine. These new compounds showed antiproliferative activities against SK-Hep-1 human liver cancer cells in MTT assays. These compounds are thus promising candidates for chemotherapy of hepatocellular carcinomas. Two compounds, 20c and 22a, showed higher potencies for inhibiting growth of hepatocellular carcinoma cells than did K6 ($ID_50$=1.08 mM). This suggests the potential anticancer activity of these two compounds.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.1
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• pp.57-66
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• 1999

국부진동에 의하여 영향을 받는 일부 부재를 분석하기 위하여 구조물 전체의 대하여 동적해석을 수행하는 것은 비경제적일 수 있다. 본 논문에서는 국부진동의 효율적인 해석을 위하여 부분구조법을 사용하였다. 선택된 부재의 해석에 사용할 경계조건을 구하기 위하여 자유도를 응축하는 행렬응축기법을 사용하였다. 해석의 정당성을 검토하기 위하여 경계조건을 고정지지와 단순지지한 경우와 비교하였다. 본 연구에서 제시한 부분구조기법을 이용하면 가진층에 대해서는 효율적으로 매우 정확한 거동을 예측할 수 있지만, 가진층에서 멀리 떨어진 곳에 대한 거동 예측 시에는 다소 오차가 발생한다.

• Proceeding of KASS Symposium
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• 2006.05a
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• pp.175-181
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• 2006

This paper presents an efficient reanalysis algorithm, named PRAS (Partial Reanalysis algorithm using Adaptable Substructuring), for the partially changed structures. The algorithm recalculates directly any displacement or member force under consideration in real time without a full reanalysis in spite of local changes in member stiffness or connectivity. The key procedures consists of 1) partitioning the whole structure into the changed part and the unchanged part, 2) condensing the internal degrees of freedom and forming the unchanged part substructure, 3) assembling and solving the new stiffness matrix from the unchanged part substructure and the changed members.

• Journal of the Optical Society of Korea
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• v.14 no.3
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• pp.266-276
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• 2010

In the present study, an optical system is proposed for maskless lithography using a digital micromirror device (DMD). The system consists of an illumination optical system, a DMD, and a projection lens system. The illumination optical system, developed for 95% uniformity, is composed of fly's eye lens plates, a 405 nm narrow band pass filter (NBPF), condensing lenses, a field lens and a 250W halogen lamp. The projection lens system, composed of 8 optical elements, is developed for 4 ${\mu}m$ resolution. The proposed system plays a role of an optical engine for PCB and/or FPD maskless lithography. Furthermore, many problems arising from the presence of masks in a conventional lithography system, such as expense and time in fabricating the masks, contamination by masks, disposal of masks, and the alignment of masks, may be solved by the proposed system. The proposed system is verified by lithography experiments which produce a line pattern with the resolution of 4 ${\mu}m$ line width.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.1
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• pp.28-35
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• 2007

In this study the seasonal performance of a residential air conditioning system having either a fin-and-tube condenser or a microchannel condenser is experimentally investigated. A commercially available 7 kW capacity residential air conditioning system having a fin-and-tube condenser served as the base system. The test results show that the system with a microchannel heat exchanger has a reduced refrigerant charge amount of 10%, the coefficient of performance is increased by 6% to 10%, and the SEER is increased by 7% as compared with those of the base system. Moreover, the condensing pressure of the system is decreased by 100 kPa and the pressure drop across the condenser is decreased by 84%. The microchannel heat exchanger enhances the SEER of the residential air conditioning system by providing better heat transfers at reduced pressure drops.