• 설비공학논문집
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• 제23권8호
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• pp.562-570
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• 2011

In this research, an experimental study is performed to investigate the effects of system operating variables on the cooling and heating characteristics of heat pump system using geothermal heat source and carbon dioxide as a refrigerant. System variables analyzed include compressor frequency, electronic expansion valve opening, refrigerant charge, secondary fluid temperature and flow rate. Results show that optimum refrigerant charge and electronic expansion valve opening position exist at the maximum point of COP curve, and both cooling and heating capacity increase but COPs decrease with the increase of compressor frequency. The change of a secondary fluid temperature leads to variation of overheat area and enthalpy difference in the evaporator and gas cooler. which again results in considerable variations of cooling and heating capacity and COP. In the case of effects of secondary water fluid flow rate, both cooling capacity and COP increase with the increase of secondary flow in evaporator or gas cooler, whereas heating capacity and COP decrease with the increase of flow rate in gas cooler.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.374-374
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• 2010

Charge transfer mechanism of poly(4,4'-aminotriphenylene hexafluoroisopropylidenediphthalimide) (TP6F PI) which exhibits bistable ON and OFF switching has been studied using photoemission electron spectroscopy (PES) and near-edge x-ray absorption fine structure (NEXAFS). Here, we demonstrate novel set-up in which holes are injected by photoemission process instead of direct charge carrier injection via metal electrode. The accumulated charges on the PI surface in the OFF state abruptly flow across the PI film when the bias voltage of a back electrode reaches a specific value, indicating that the film is changed to the ON state. Core level and x-ray absorption spectra probed at charge injection region via photoemission process do not show any evidences implying structural modification of TP6F PI during the phase change. Whereas, in valence band spectra, the highest occupied molecular orbital (HOMO) is shifted toward Fermi level, responsible for improved hole-mobility of TP6F PI of ON state.

• 대한전자공학회논문지
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• 제16권1호
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• pp.26-32
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• 1979

실리콘의 dry oxidation과 wet oxidation공정의 특성을 실험적으로 조사하였다. 산화온도는1,100℃, 1.150℃, 1.200℃를 사용하였고, 산소의 유량은 0.2 liter/min으로 부터 2.8 liter/min까지 변화시켰다. 산화막의 두께를 측정하여 0.1μ ∼ 1.0μ 을 성장시키는데 필요한 온도, 시간, 산소의 유량을 도표로 나타냈다. 산화막의 특성을 조사하기 위하여 유전 상수 절연파괴 전압, fixed surface charge density (Qss/q), mobile ciarge densify (Q /q)를 측정하였다. 측정 결과로부터 산화막이 MOS transistor에도 적합한 양질이라는 결론을 얻었다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제7권3호
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• pp.85-94
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• 2002

본 연구의 목적은 토양입자에 대한 전기화학적 특성을 평가함으로써 동전기 기술을 실제 현장에서 적용시, 오염물을 효과적으로 제거하기 위한 최적 운전방법이나 인자를 도출하는 것이다. 토양입자의 제타포텐셜을 토양용액의 pH와 계면활성제의 농도에 대하여 측정하여 전기삼투압적 흐름방향 및 흐름율과의 관계를 분석하였다. 동전기 실험동안, 전기삼투압 투과율($k_e$), 전기전도도($\delta_e$) 및 전압분포에 대한 측정을 실시하였다. Kaolinite의 PZC는 4.2정도로 측정되었으며 pH가 증가할수록 제타포텐셜 감은 점점 음의 값이 증가하는 경향을 나타내었다. 주입된 계면활성제 또한 토양 표면의 전기화학적 특성에 영향을 주어 제타포텐셜 값을 변화시키는 결과를 나타내었다. 동전기 실험이 진행되는 동안, 토양시료의 대부분에 걸쳐 낮은 pH값을 나타내었으며 이로 인하여 용액과 전기적 흐름이 낮아지는 결과를 초래하였다. 또한, 전압 분포도 시간에 따라 변화하여 용액과 전기적 흐름 특성에 영향을 주었다. 결과적으로, 낮은 pH에 의한 토양의 제타포텐셜 값의 변화와 구간별로 다른 전압차분포로 인하여 용액과 전기적 흐름이 영향을 받는다는 결과를 본 연구로부터 얻었다. 효과적인 동전기 공정의 적용을 위하여 인위적인 토양 용액의 pH 조절이나 토양의 전기적 특성을 변화시키는 물질 등을 동시에 주입함으로써 오염물을 제거하는 용매의 흐름이 계속적으로 높게 유지되도록 하는 방안이 필요하다.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.1
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• pp.294.1-294.1
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• 2003

At pH 7.4 (physiological pH), skin is permselective to cations, due to the net negative charge of the current passing channels (pores) in skin. This causes the convective solvent flow (electroosmotic flow) from anode to cathodal direction. In this work, we have investigated several factors (pH. current density and ionic strength) that can affect the electroosmotic flow. (omitted)

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 추계학술대회 논문집
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• pp.15-16
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• 2014

This paper proposed a construction of BMS to adopt energy storage system using flow battery. To operate flow battery system with BMS, there are motor drive system to pump electrolyte up. And it needs sensors to check leaking and temperature. The proposed system is verified by experiment.

• 한국세라믹학회지
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• 제32권10호
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• pp.1123-1130
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• 1995

In the preparation of manganese zinc ferrite powders by alcoholic dehydration of citrate/formate solution. The effect of pH change on precipitation was investigated. The pH range for obtaining stable precipitates was studied. The glassy phase was obtained when the pH value of solution is higher than 5, and the formation mechanism of glassy phase was suggested. Below pH 5, the stable precipitates were formed, and the optimal pH was 2. Formation of glassy phase was accounted for the change of surface charge by pH change. The change of surface charge is caused by the interparticular agglomeration. The precipitate was redissolved into the water on the surface of precipitate itself and through the polymerization, it agglomerated. This mechanism is tought to be similar to that of viscous flow.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.341-346
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• 2000

This experimental study investigated the flow motion of the working fluid for various diameters of miniature thermosyphons and the performance characteristics for the various amount of the working fluid. The temperatures of condenser surface were measured and visual observations were conducted. The test results show that some fluid condensed in the tube diameters of 0.18cm and 0.22cm is not returned to the evaporator section due to capillary effect so that large temperature gradients are measured. To enhance returning the working fluid, one copper wire of 0.5mm diameter was inserted and the test results show good performance. When the liquid charge was less than 10% in volume dry-out was occurred fur the thermosyphons of the inner diameter of 1.8mm and 2.2mm.

• 한국자동차공학회논문집
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• 제5권5호
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• pp.114-122
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• 1997

Nowadays, gasoline direct injection engines are being commercialized by virtue of improvement in control technology of spray, flow, air fuel ratio. The stratified charge type has the advantage of improving lean limit. The homogeneous type has the advantage of reducing engine-out hydrocabon emissions in the first 30 seconds after a cold start, in addition, improving transient air fuel ratio control. The vaporization and mixing if injected fuel with air has to e completed in a short time and the fuel film in cylinder and on piston has to be minimized. So, the flow and injection should be well controlled. This paper surveyed the spray characteristics of gasoline direct injection by using laser equipment and the combustion characteristics of the single cylinder engine using homogeneousas-mixture type gasoline direct injection.

• Journal of Mechanical Science and Technology
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• 제17권10호
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• pp.1485-1495
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• 2003

We investigate the triboelectrostatic separation of polyvinylchloride (PVC) from mixed plastics in the laboratory scale triboelectrostatic separation system. The flow and electric fields in the precipitator are obtained from the numerical solution of finite volume method. Using these flow and electric fields, we solved the particle motion equation considering the inertia, drag, gravity and electrostatic forces acted on the particles. The particle trajectories are obtained using a Lagrangian method as a function of different important variables such as Reynolds number, Stokes number, electrostatic force, electric charge and electric field distribution, inclined angle of plane electrodes, particle rebounding, particle charge decay rate after impact on the electrode surface, etc., in order to determine the optimal design conditions. The present predicted results for the cumulative yield represent well the experimental ones.