• Journal of the Korean Electrochemical Society
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• v.18 no.2
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• pp.68-74
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• 2015

To compare the microstructure and electrochemical properties between two binary alloys (Cr-Si, Ni-Si), two composition of binary alloys with the same capacity were selected using phase-diagram and prepared by matrix-stabilization method to suppress the volume expansion of Si by inactive-matrix. Master alloys were made by Arc-melting followed by fine structured ribbon sample preparation by Rapid Solidification Process (RSP, Melt-spinning method) under the same conditions. Also powder samples were produced by wet grinding for X-Ray Diffraction (XRD) and electrochemical measurements. As predicted from the phase diagram, only active-Si and inactive-matrix ($CrSi_2$, $NiSi_2$) were detected. The results of Scanning Electron Microscope (SEM) and Transmission Electron Microscopy - Energy Dispersive X-ray Spectroscopy (TEM-EDS) show that Cr-Si alloy has finer microstructure than Ni-Si alloy, which was also predictable through phase diagram. The electrochemical properties related to microstructure were evaluated by coin type full- and half-cells. Separately, self-designed test-cells were used to measure the volume expansion of Si during reaction. Volume expansion of Cr-Si alloy electrode with finer microstructure was suppressed significantly and improved in cycle capability, in comparison Ni-Si alloy with coarse microstructure. From these, we could infer the correlation of microstructure, volume expansion and electrochemical degradation and these properties might be predicted by phase diagram.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.11
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• pp.897-903
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• 2015

In this paper, the contrast therapy of skin was numerically investigated by solving the conjugate heat transfer problem. A finite volume method based on the SIMPLE algorithm was adopted to solve the axisymmetric incompressible Navier-Stokes equations, coupled with an energy equation. These equations are strongly coupled with the Pennes bio-heat equation in order to consider the effect of blood perfusion rate. We investigated the thermal response of skin at some selected depths for various input temperature profiles of a stimulator for contrast therapy. From the numerical simulations, the regions with cold/hot threshold temperatures were found for five input temperature profiles. It was shown that the temperature varies mildly for different input profiles as the depth increases, owing to the Pennes effect. The input temperatures for effective hot/cold stimulation of dermis layer were found to be $47^{\circ}C$ and $7^{\circ}C$, respectively. The present numerical results will be used for finding an optimal temperature profile of a stimulator for contrast therapy.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.1
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• pp.53-60
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• 2011

In this study, an organic Rankine-cycle system using HFC-134a, which is a power cycle corresponding to a low-temperature heat source, such as that for geothermal power generation, was investigated from the view point of power optimization. In contrast to conventional approaches, the heat transfer and pressure drop characteristics of the working fluid within the heat exchangers were taken into account by using a discretized heat exchanger model. The inlet flow rates and temperatures of both the heat source and the heat sink were fixed. The total heat transfer area was fixed, whereas the heat-exchanger areas of the evaporator and the condenser were allocated to maximize the power output. The power was optimized on the basis of three design parameters. The optimal combination of parameters that can maximize power output was determined on the basis of the results of the study. The results also indicate that the evaporation process has to be optimized to increase the power output.

• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.234-238
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• 2015

The separation of nitrogen heterocyclic compound (NHC) contained in a model coal tar fraction was compared by the methanol and formamide extraction. The model coal tar fraction comprising four kinds of NHC (NHCs : quinoline, iso-quinoline, indole, quinaldine) and three kinds of bicyclic aromatic compound (BACs : 1-methylnaphthalene, 2-methylnaphthalene, dimethylnaphthalene), biphenyl and phenyl ether was used as a raw material. The aqueous solution of methanol and formamide were used as solvents. A batch-stirred tank was used as the raw material - a solvent contact unit of this work. Independent of the solvent used, the distribution coefficient of NHCs sharply increased by decreasing the initial volume ratio of water to the solvent and increasing the equilibrium operation temperature, whereas, the selectivity of NHCs in reference to BACs decreased. Decreasing the initial volume ratio of solvent to feed resulted in deteriorating distribution coefficients, but the selectivity of NHCs in reference to BAC was almost the constant. The distribution coefficient of NHCs by the methanol extraction was 3~5 times higher than that of NHCs by the formamide extraction, inversely, the selectivity of NHCs based on BACs by the formamide extraction was 3~7 times higher than that of NHCs by the methanol extraction. Furthermore, two different solvent extraction methods by adding the extraction processing speed to the balance between solvency and selectivity of NHCs were compared.

• Tunnel and Underground Space
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• v.18 no.1
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• pp.44-57
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• 2008

In this study, a 2D finite-element analysis, using the SEEP/W program, was carried out to estimate the amount of groundwater flawing into a tunnel, as well as the groundwater tables around wetland areas during and after a tunnel excavation through rock mass. Four sites along the Wonhyo-tunnel in Cheonseong Mountain (Gyeongnam, Korea) were analysed, where the model damain of the tunnel included both wetland and fault zone. The anisotropy of the hydraulic conductivities of the rock mass was calculated using the DFN model, and then used as an input parameter for the cantinuum model. Parametric study on the influencing factors was perofrmed to minimize uncertainties in the hydraulic properties. Moreover, the volumetric water content and hydraulic conductivity functions were applied ta the model to reflect the ability of a medium ta store and transport water under both saturated and unsaturated conditions. The conductivity of fault zone was assumed ta be $10^{-5}m/sec\;or\;10^{-6}m/sec$ and the conductivity of grouting zone was assumed as 1/10, 1/50 or 1/100 of the conductivity of rock mass. Totally $6{\sim}8$ cases of transient flow simulation were peformed at each site. The hydraulic conductivities of fault zone showed a significant influence on groundwater inflow when the fault zone crossed the tunnel. Also, groundwater table around wetland maintained in case that the hydraulic conductivity of grouting zone was reduced ta be less than 1/50 of the hydraulic conductivity of rock mass.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.5
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• pp.473-480
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• 2011

The proton exchange membrane (PEM) fuel cell system is critically dependent on the humidity, which should be properly maintained over the entire operating range. A membrane humidifier is used for the water management in the PEMFC because of the membrane humidifier's reliable performance and zero parasitic power loss. In the PEMFC system, the membrane humidifier is required to provide appropriate humidity for the design point of the fuel cell. Although the performance of the fuel cell depends on the performance of the humidifier, few studies have provided a systematic analysis of the humidifier. We carry out an experimental analysis of the membrane humidifier using a vapor condensation bottle. The dry air pressure, water flow temperature, and air flow rate were chosen as the operating parameters. The results show that the time constant for the dynamic response of the membrane humidifier is relatively short, but additional analysis should be carried out.

• Journal of Korean Medical classics
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• v.18 no.4 s.31
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• pp.155-165
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• 2005

진당시기대상한론치법적연구유(晋唐時期對傷寒論治法的硏究有): 왕숙화운용당시성행적(王叔和運用當時盛行的)‘한(汗), 토(吐), 하(下), 온(溫), 구(灸), 자(刺), 수(水), 화(火)’등팔법(等八法), 귀납료상한론적증치경험(歸納了傷寒論的證治經驗); 손사막근거자기적임상경험(孫思邈根據自己的臨床經驗), 파상한론적태양병편진행료(把傷寒論的太陽病篇進行了)‘이방명법(以方名法), 안법류증(按法類證)’, 저시해시기대상한론육경병치법적대표성적연구(這是該時期對傷寒論六經病治法的代表性的硏究), 저종연구유원시화력사적국한성(這種硏究有原始和歷史的局限性), 종중국의학대상한론육경병치법적연구력사고려(從中國醫學對傷寒論六經病治法的硏究歷史考慮), 저성위료후세적치법연구적선구자(這成爲了後世的治法硏究的先驅者), 구유비상대적영향(具有非常大的影響). 재송대대상한론치법적연구상(在宋代對傷寒論治法的硏究上), 기관건작용적의가유방안시화주굉(起關鍵作用的醫家有龐安時和朱肱). 타문대상한론치료원칙적천발(他們對傷寒論治療原則的闡發), 대륙경병적분석귀납(對六經病的分析歸納), 이급제시구체적치법상(以及提示具體的治法上), 도주출료공헌(都做出了貢獻). 방안시주장료응안인(龐安時主張了應按人), 지(地), 시제정치료적사상(時制定治療的思想); 주굉이(朱肱以)‘병유표본(病有標本), 치유선후(治有先後)’위치료원칙(爲治療原則), 여상한론상결합진행치료(與傷寒論相結合進行治療), 대후세의가산생료영향(對後世醫家産生了影響). 도료금원대성무기(到了金元代成無己), 류완소(劉完素), 왕호고등(王好古等), 대내경내용각자이사상관점(對內經內容各自以思想觀点), 분별안변증론치총결료육경병적치료규율(分別按辨證論治總結了六經病的治療規律), 동시대증후화방약진행료분석(同時對證候和方藥進行了分析), 천명료구체적육경병치법적병리전귀(闡明了具體的六經病治法的病理轉歸), 도유기독창성(都有其獨創性). 성무기용내경해석료상한론(成無己用內經解釋了傷寒論), 총결해기(總結解肌) 발한(發汗) 중제발한(重劑發汗) 해표행수(解表行水) 화해(和解) 공비 지열(止熱) 삼설등치법, 위후세대상한론치법적연구개벽료도로, 인이갱가명확화해적개념(因而更加明確和解的槪念), 병응용지금(幷應用至今). 류완소제창료주화론(劉完素提倡了主火論), 중시료상한론한(重視了傷寒論汗), 토(吐), 하삼법적연구(下三法的硏究), 창립료신량해표법(創立了辛凉解表法), 대후세온병치료적발전대래료흔대영향. 왕호고작위이수학파(王好古作爲易水學派), 운용장부적한열허실이론결합약미효능(運用臟腑的寒熱虛實理論結合藥味效能), 탐색료상한론육경병적치료규율(探索了傷寒論六經病的治療規律), 강조료양명병적익진액적치료원칙(强調了陽明病的益津液的治療原則), 대후세연구상한론치법급여료흔대적계발. 이상대상한론치법연구(以上對傷寒論治法硏究), 불근성위당시임상의학적선도(不僅成爲當時臨床醫學的先導), 이차성위료후세연구상한론치법적기초(而且成爲了後世硏究傷寒論治法的基礎).

• Journal of the Korean Society for Marine Environment & Energy
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• v.8 no.1
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• pp.39-45
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• 2005

In the situation which Russia's ratification of the Kyoto protocol at February,2004, ANNEX I nations must reduce GHG(Green House Gas) discharge rate from 2008 by 2012 to the reduction level at 1990. We introduce the CO₂ ocean sequestration that is one of promising method for getting the stable CO₂ concentration in the atmosphere. There are four categories : ocean transportation technique, ocean initial dissolution technique, ocean deep current evaluation technique, and ocean biological evaluation technique. In this paper, we carried out the fundamental numerical study on the ocean initial dissolution technique, when the Liquidized CO₂ is emitted at the deep ocean, It is very important to the dissolution rate of movable CO₂ interface because it Is directly impact to the ocean organism. In order to investigate the relation of the interface movement and rate of the dissolution, we develope CR(Computational Fluid Dynamics) code that was constructed by the finite volume method based on the unstructured mesh, and a droplet's boundary surface can move and one direction dissolution from disperse phase into continuous phase adopted as its physics be. This study clarifies hydrodynamic relation between solubility and movement of the droplet through the verification of the Cm code.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6447-6454
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• 2013

Seawater intake systems have significant problems due to seawater pollution, suspended solids, unstable intake and maintenance etc. An underground type seawater intake system was newly developed to overcome the existing weaknesses and was facilitated in Gyukpo port. In this study, to check the performance of the new system, the samples for water quality and the 3-D numerical modeling test were conducted. The five times test included the COD, total nitrogen, total phosphorus, pH, and suspended solid for the intake system. The analyses show that the COD, total nitrogen, total phosphorus, PH showedminor changes before and after. On the other hand, the change in suspended solids was significant and water was purified below 5 mg/l, first level fisheries water, after. The numerical model adopted the RNG $k-{\epsilon}$ algorithm and the CFX model based on the finite volume method. The porosity algorithm was used to reproduce filtered-sand, outer diameter, and thickness. The numerical results showed that the double pipe is advantageous in that it provides a uniform pressure between the inner and outer pipe for the flow to be stable. In addition, the use of multiple intake pipes did not interfere with the discharge reduction of 0.98 at the both intake pipes compared with the central intake pipe.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.122-126
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• 2017

The aim of this study was to develop a device for solving the heating problem of living space using heated air, utilizing a simple air heater type collector for solar energy. At the present time, this study assessed the possibility of a development system through theoretical calculations for the amount of available energy according to the size change of the air-heated solar energy collector. To produce and supply hot water using the heat energy of the sun, hot water at $100^{\circ}C$ or less was produced using a flat or vacuum tube type collector. The purpose of this study was to research the air heating type solar collector that utilizes heating energy with heating air above $75^{\circ}C$, by designing and manufacturing an air piping type solar collector that is a simpler type than a conventional solar collector system. The analysis results were obtained for the generated air temperature ($^{\circ}C$) and the production of air (kg/h) to determine the performance of air heating by an air-heated solar collector according to the heat transfer characteristics in the collector of the model when a specified amount of heat flux was dropped into a solar collector of a certain size using PHOENICS, which is a heat flow analysis program applying the Finite Volume Method. From the analysis result, the temperature of the air obtained was approximately $40.5^{\circ}C$, which could be heated using an air heating tube with an inner diameter of 0.1m made of aluminum in a collector with a size of $1.2m{\times}1.1m{\times}0.19m$. The production of air was approximately 161 m3/h. This device can be applied to maintain a suitable environment for human activity using the heat energy of the sun.