• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2137-2143
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• 2008

This paper investigates the plate loop heat pipe system with an evaporator mounted with fin-wick structure to dissipate effectively the heat generated by the electronic components. The heat transfer formulation is modeled and predicted through thermal resistance analysis of the fin-wick structure in the evaporator. The experimental approach measures the thermal resistances and the operating characteristics. These results gathered in this investigation have been used to the objective of the information to improve the LHP system design so as to apply as the future cooling devices of the electronic components.

• Journal of Electrochemical Science and Technology
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• 제11권1호
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• pp.1-13
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• 2020

As research on secondary batteries becomes important, interest in analytical methods to examine the condition of secondary batteries is also increasing. Among these methods, the electrochemical impedance spectroscopy (EIS) method is one of the most attractive diagnostic techniques due to its convenience, quickness, accuracy, and low cost. However, since the obtained spectra are complicated signals representing several impedance elements, it is necessary to understand the whole electrochemical environment for a meaningful analysis. Based on the understanding of the whole system, the circuit elements constituting the cell can be obtained through construction of a physically sound circuit model. Therefore, this mini-review will explain how to construct a physically sound circuit model according to the characteristics of the battery cell system and then introduce the relationship between the obtained resistances of the bulk (R_b), charge transfer reaction (R_ct), interface layer (R_SEI), diffusion process (W) and battery characteristics, such as the state of charge (SOC), temperature, and state of health (SOH).

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.91-91
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• 2009

In the past decade, Pd based thin films have been studied far hydrogen gas sensors due to their high possibility for energy industry and environmental applications. In this work, we report a navel method to fabricate highly sensitive hydrogen gas sensors based on PdO thin films. The films were deposited on Si substrates in Ar and $O_2$ ambient using reactive sputtering system. A semiconductor process has been utilized to fabricate PdO films with t=40nm. We observed the resistance changes of the PdO films with various $H_2$ concentrations. It was found that the electrical properties of the thin films depend on the composition of oxygen. The sensitivity is defined as $S\;=\;(R_0-R)/R{\times}100%$, where R and $R_0$ are the resistances in the presence of exposing the hydrogen gas and air, respectively. The sensitivity of the thin films was found to be as high as about 95%. After exposing to hydrogen gas, we discovered that the nano-sized cracks formed on the surface of the PdO thin films. The nano-cracks formed in deoxidized PdO thin films were known by playing a key role to reduce more than 4 times the response time of absorption. Our results illustrate that the deoxidized PdO thin films can be used as hydrogen sensors.

• 상하수도학회지
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• 제31권4호
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• pp.321-328
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• 2017

Recently EC-MBR (Elctrocoagulation - Membrane Bio Reactor) has been suggested as one of alternative processes to overcome membrane fouling problems. Most important operational parameters in the EC-MBR are known to current density and contact time. Their effect on membrane filtration performances has been reported well, however, quantitative interrelationship between both parameters not been investigated yet. The purpose of this study is to give a kinetic model suggesting the current density and the contact time required to reduce the membrane fouling. The 4 different set of current densities (2.5, 6, 12 and $24A/m^2$) and contact times (0, 2, 6 and 12 hr) were selected as operational parameters. After each electro-coagulation under the 16 different conditions, a series of membrane filtration was carried out. The membrane fouling decreased as the current density and contact time increased, Total fouling resistances under different conditions, $R_t(=R_c+R_f)$ were calculated and compared to those of the controls ($R_0$), which were calculated from the data of experiments without electro-coagulation. A kinetic approach for the fouling reduction rate ($R_t/R_0$) was carried out and the equation ${\rho}^{0.46}_it=7.0$ was obtained, which means that the product of current density and the contact time needed to reduce the fouling in certain amounts (in this study, 10% of fouling reduction) is always constant.

• 공업화학
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• 제4권1호
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• pp.153-161
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• 1993

$700-900^{\circ}C$의 온도범위와 여러 산소분압 조건에서 고체전해질 연료전지의 양극인 $La_{0.9}Sr_{0.1}MnO_3$에서 산소의 환원반응특성을 조사하였다. AC 임피던스법과 전류중단법에 의해 산소환원반응의 전하전달저항을 측정하였는데 두 방법으로 구한 간이 서로 잘 일치하였다. 전기화학적 산소환원반응의 활성화에너지는 대기압 조건에서 174kJ/mol의 값을 보였고, 산소분압에 따른 전하전달저항의 측정결과로 부터 이 전극에서 전기화학적 산소환원반응의 율속단계는 전하전달과정임을 알 수 있었다.

• 멤브레인
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• 제25권3호
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• pp.268-275
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• 2015

침지식 분리막 모듈에서 공기강도에 따른 분리막 위치에 대한 오염을 조사하였다. 분리막의 충진밀도가 낮은 곳에서 높은 유체 유속을 나타내었으며, 유체 속도는 기-액 주입률에 비례하였다. 전단응력은 기-액 주입률 및 유체 유속에 비례하였다. 비가역오염($R_{ir}$)은 흡입 압력이 가까운 부분에서 가장 높게 나타났다(position 1). 비가역오염에 대한 저항과 분리막 고유 저항의 비($R_{ir}/R_m$) 및 비가역오염에 대한 저항과 가역오염의 저항의 비($R_{ir}/R_r$)도 position 1에서 가장 높게 조사되었다. 비가역오염($R_{ir}$)은 흡입 압력이 높은 곳인 position 1에 오염물질이 축적되어진 결과이다. 분리막 위치에 따른 오염현상은 모듈 디자인 최적화에 중요한 인자임을 알았다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 정기총회 및 추계학술대회 논문집 학회본부
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• pp.59-62
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• 1993

The evaluation of the temperature of the motor in operation is necessary for smaller and lighter design of motors and for the determination of insulation class. And the evaluation of the temperature in thermal transient state is necessary for the determination of the intermittent rating and the protection from the thermal overload. The temperature can be calculated exactly by considering the loss distribution, the thermal resistances and the thermal capacities dependent on temperature. Using the detailed thermal equivalent circuit, the temperature of any local part of the motor can be evaluated. The comparison between the calculated results and the experiments is performed to verify the validity of the analysis.

• 한국해양공학회지
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• 제7권1호
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• pp.56-61
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• 1993

Standard values in graphic porms are presented for the ratio of added wave resistance to the sun of added wave and wind resistances in head sea for three ship types, tanker, container ship and passenger ship. The effect of ship length on the ratio defined above is investigated for the three ship types. Obique sea added resistance is determined using wave direction reduction factor. The factor is obtained from model test results and cubic spline interpolation technique.

• 콘크리트학회논문집
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• 제19권6호
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• pp.785-793
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• 2007

본 연구는 정전류 펄스법을 이용하여 콘크리트 내 보강철근의 부식률을 정량적으로 평가한 실험 결과를 나타낸 것이다. 콘크리트와 보강철근의 부식 경계면에서 미소전류의 인가에 의해 변화되는 부식전위 $({\Delta}E)$를 분석함으로써 보강철근의 분극저항 $R_{ct}$는 저항/커패시턴스 (resistance/capacitance)모델에 기초하여 개별 성분으로 분리되었다. 분리된 각 성분에는 부식 과정과 관련된 저항뿐 아니라 콘크리트 내 이온의 확산저항 등과 같은 부식에 관계없는 저항 성분들도 포함되어 있었다. 참조 전극과 보강철근의 측면 이격 거리에 따른 일련의 실험 결과는 부식 과정에 관계없는 저항 성분들로부터 부식에 관련된 저항 성분을 명확히 구별할 수 있음을 잘 보여주고 있다. 만일 보강철근의 부식률이 부식에 관계없는 저항 성분들까지 포함된 분극저항에 의해 평가된다면, 보강철근의 부식률은 실제의 부식 상태보다 최대 2.3배까지 과소평가될 수 있는 것으로 조사되었다. 측정 시간이 부식률 평가에 미치는 영향은 부식 철근의 경우 크지 않았지만, 측정 시간이 길어짐에 따라 부식에 관계없는 저항성분이 포함될 수 있음을 보였고, 비교적 늦은 시상수 (time constant)를 갖는 부동태 철근의 경우 측정 시간에 큰 영향을 받는 것으로 조사되었다.

• 한국농공학회지
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• 제26권1호
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• pp.29-37
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• 1984

This study was made to find several significant relations among various physical and mechanical properties including cone penetration resistance. The alluvial clay samples were taken at the Daebul Reclaimed Tideland in Samhomyeon, Yeongamgun, Jeonranamdo. The results of the study are summarized as follows; 1.Most samples belong to medium or high plastic, inorganic, silty clay(clay contents;32-64%, silt contents; 36-68%, sand contents; 0-3%). The specific gravities range from 2.70 to 2.73, the unit weights from 1.45 to 1. 75g/cm$^3$, the natural moisture contents from 45 to 77%, the liquid limits from 32 to 56%. It is certain that the foundation is weak because the natural moisture contents are much higher than the liquid limits. 2.It is known from the shear tests that the unconfined compression strenghs vary from 0.09 to 0. 38kg/cm2, the cohesions from 0.05 to 0. 21kg/cm2, the internal friction angles from 0 to 3˚. 3.The consolidation tests show that the initial void ratios range from 1.25 to 2.28, the compression indeices from 0.43 to 0.84, the preconsolidation loads from 0.21 to 0.74kg/cm$^2$. 4.Cone penetration resistances are usually less than 5kg/cm$^2$ from ground surface to the depth of about 8m, and from S to l0kg/cm$^2$ in the layer below about 8m to hard layer. 5.The cohesion and cone penetration resistance are in proportion to the depth of soil layer. 6.The correlations between various physical and mechanical properties including cone penetration resistance for the alluvial clay samples are as follows; a) Wn=0.944C+ l2.733 (r=0.829) b) LL=0. 728Cy+6. 991 (r=0. 873) c) PI=0.659Cy-8.168 (r=0.860) d) rt=0. 0077(272-Wn) =2.092-0. 0077Wn (r=0. 859) e) 60=0. 035wn-0 447 (r=0. 893) f) C=0.380qw+0.031 (r=0.816) g) qu=0.0707qc+0.029 (r=0.810) h) C=0.018Z+0.055 (r=O.802) I) qc=0. 415Z+1, 438 (r=0. 943)