• Journal of Environmental Science International
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• v.8 no.3
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• pp.393-397
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• 1999

Among various reactions which metal sulfides can undergo in the reducing environment, the lattice exchange reaction was examined in a attempt to selectively remove heavy metal ions contained in the Fe-Coagulants acid solution. We have examined Zeta potential along with pHs to investigate surface characteristics of ${FeS}_{(s)}$. As a result of this experiment, zero point charge(ZPC) of FeS is pH 7 and zeta potential which resulted from solid solution reaction between Pb(II) and ${FeS}_{(s)}$ is similar to that of ${PbS}_{(s)}$. Solubility characteristics of ${FeS}_{(s)}$ is appeared to that dissolved Fe(II) concentration increased in less than pH 4, and also increased with increasing heavy metal concentration. Various heavy metal ions(Pb(II), Cu(II), Zn(II)) contained in Fe-coagulants acid solution were removed selectively more than ninety-five percent in the rang of pH 2.5~10 by ${FeS}_{(s)}$. From the above experiments, therefore, We could know that the products of reaction between heavy metal ions and $FeS_{(S)}$ are mental sulfide such as $PbS_{(S)}$, $CuS_{(S)}$ and $ZnS_{(S)}$.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.1
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• pp.113-119
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• 2009

The feasibility of using cork oak bark for phosphorus removal from wastewater was evaluated in this study. Recently, development of more cost-effective media while maintaining high efficiency in pollutants removal has received concern. Barks have a negative surface charge and, hence, tend to show a high affinity to bind cations, and they need to undergo chemical modification to increase their adsorption capacity of anions. Bark was hydrolyzed by HCl solution and it received modification using an aqueous solution of high molecular weight polyethylenimine(PEI). Surface modification with HCl and PEI resulted in a decrease of specific surface area of the bark from $1.932 m^2/g$ to $1.094 m^2/g$. The adsorption experiments were carried out in batch tests and the data were fitted to the Langmuir isotherm and Freundlich isotherm equations. Phosphate removal rate was higher at the lower solution pH possibly due to the form of phosphate ion in solution. For the initial phosphate concentration of 10 mg/L, maximum adsorption was 20.88 mg P/g at pH 3 and 12.02 mg P/g at pH 5. Mechanism of phosphorus sorption onto the HCl-PEI bark was examined through FT-IR spectrometer. Ion exchange between $NH^+$ and $H_2PO_4{^-}$ appeared to be a key mechanism of phosphate adsorption onto the HCl-PEI bark surface.

• The Journal of Information Systems
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• v.14 no.2
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• pp.25-53
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• 2005

To overcome rapidly changing business environment, companies are focusing on their core business areas. Outsourcing in general has become a standard to sustain competitive advantage. ASP(Application Service Provider) service, another form of IT outsourcing, is business model for providing a contractual service offering to deploy, host, manage and rent access to an application from a centrally managed facility. The main purpose of this study is to investigate on the factors contributing to the success of ASP services by conducting an empirical research to enterprises using ASP service. For this purpose, we developed a research model based on the literature reviews of ASP services, IT outsourcing, and relational exchange. A total of 106 usable survey responses has been used in the analysis. The unit of analysis was relationship and respondents were person in charge of ASP service of each corporation. The findings indicates that (1) service tangibles, customization, partnership, IS maturity and monitoring of the vendor had an positive influence upon non-economic benefits, (2) service tangibles, IS maturity and monitoring of the vendor had an positive influence upon economic benefits, and (3) service tangibles, reliability, partnership and monitoring of the vendor had positive influence upon satisfaction about outcomes of relationships.

• Korean Journal of Computational Design and Engineering
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• v.13 no.6
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• pp.459-468
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• 2008

A web-based Computer-Aided Engineering (CAE) supporting system is connected with a Product Data Management (PDM) system for Small and Medium Enterprises (SMEs) suffering from the lack of building hardware, software and related experts. An analysis of current business models and worksite requirements provides an improved process model and data to be shared between the PDM system and the CAE supporting system. Since all engineering tasks such as geometric modeling, mesh generation, static stress and modal analysis, and fatigue durability analysis are automated in the CAE supporting system, the user in charge of the CAE have only to configure the concerned values of design variables and result data through the web page. The existing Change Management module of the PDM system is modified for seamless data exchange, i.e. sending the Engineering Change Order (ECO) data to the CAE supporting system and receiving the CAE result data bark. The hi-directional data transfers between the PDM system and the CAE supporting system is made possible by adaptors bused on the Simple Object Access Protocol (SOAP). The current approach will be very helpful for SMEs that only have the PDM system and have no adequate infrastructure for CAE.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.150-151
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• 2003

In the past years, a giant magnetoresistance (GMR) effect found in perovskite-like structured materials has attracted considerable attention among scientists and manufacturers, since, a practical point of view, the capacity of producing magnetic and sensing sensors. In a stream of this interest, further efforts to understand the underlying mechanism that leads to the GMR effect relative to the correlation between transport and magnetic properties, have been extensively devoted. In these cases, spin-glass-like behaviors are ascribed to the frustration of random competing exchange interactions, namely the ferromagnetic double-exchange interaction between Co$\^$3+/ (or Mn$\^$3+/) and Co$\^$4+/(or Mn$\^$4+/) and the antiferromagnetic one like spins. Noticeably, the distinction of spin-glass region from cluster-glass one, involved in the remarkable changes in transport and magnetic properties at a critical value of doping concentration, was observed. Magnetic anomalies in zero-field-cooled (ZFC) magnetization as well as ac magnetic susceptibility below Curie temperature T$\sub$c/ and the charge/orbital fluctuation were also realized. In this work, we present a study of magnetic properties of a deficient manganese perovskites system of La$\sub$0.6/Sr$\sub$x/MnTi$\sub$y/O$_3$, and particularly provide its new magnetic phase diagram.

• Journal of the Korean Society for Railway
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• v.9 no.1 s.32
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• pp.36-42
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• 2006

Studied was a strategic plan for the Korean High-Speed Train system to penetrate the Chinese railway market in exchange of the technology of KHST. Firstly, taken was a glance at Chinese Government plans to extend total length of his railway lines and to construct the Beijing~Shanghai high-speed railway line. Then, disparity of railway technology in Korea and China was reviewed. From the review, SWOT Analysis were carried out to penetrate the foreign markets. Countermeasures to cope with SWOT were also considered. Strategical governmental supports and the establishment of the special organization to be in charge of penetration of KHST into foreign markets were proposed. Finally, also proposed was the transfer of KHST technology to Chinese counterparts in exchange of tangible benefits for Korean side. The benefits may include (1) adoption of KHST as the type of rolling stock for the Beijing~Shanghai line, (2) guarantee of participation in the project and royalty for the KHST technology used for the future high-speed railway line construction, (3) prior written approval and partnership when making its way to third country, and (4) participation of Korean construction companies in Chinese railway construction project, etc. Adoption of KHST in China indeed gives chance to integrate the high-speed railway network after reunification of Korean peninsular, and enhance the economic ties between two countries.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.907-914
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• 2005

Studied was a strategic plan for the Korean High-Speed Train system to penetrate the Chinese railway market in exchange of the technology of KHST. Firstly, taken was a glance at Chinese Government plans to extend total length of his railway lines and to construct the $Beijing\~Shanghai$ high-speed railway line. Then, disparity of railway technology in Korea and China was reviewed. From the review, SWOT Analysis were carried out to penetrate the foreign markets. Countermeasures to cope with SWOT were also considered. Strategical governmental supports and the establishment of the special organization to be charge of penetration of KHST into foreign markets were proposed. Finally, also proposed was the transfer of KHST technology to Chinese counterparts in exchange of tangible benefits for Korean side, The benefits may include (1) adoption of KHST as the type of rolling stock for the $Beijing\~Shanghai$ line, (2) guarantee of participation in the project and royalty for the KHST technology used for the future high-speed railway line construction. (3) prior written approval and partnership when making its way to third country, and (4) participation of Korean construction companies in Chinese railway construction project. etc. Adoption of KHST in China indeed gives chance to integrate the high-speed railway network after reunification of Korean peninsular, and enhance the economic ties between two countries.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.2
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• pp.133-140
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• 2006

The performance of proton exchange membrane fuel cell was decreased by reverse voltage using fuel starvation. Performance decrease in local area could be affected by duration and extent of reverse voltage. Hydrogen and air stoichiometic ratio was used to find the experimental condition of abrupt voltage decrease. LabVIEW was used to make control logic of automatic load off system in preset voltage. Reverse voltage experiment was done down to -1.2 V at constant current condition. When fuel cell voltage was reached to preset voltage, electronic load was disconnected to make open circuit voltage for 1 minute. Fuel cell performance was checked every 5 cycle and the degree of performance decrease and/or recovery was estimated. Ohmic resistance and charge transfer resistance were increased and platinum surface area was reduced 41% after reverse voltage experiment.

• Journal of the Korean Applied Science and Technology
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• v.27 no.3
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• pp.310-317
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• 2010

The electrochemical properties of electric double layer capacitor(EDLC) was studied by controlling pore size distribution and specific surface area of the activated carbon fiber(ACF). The mesoporous ACF, which was prepared by the iron exchange method, showed the tendency of increasing average pore size and decreasing total surface area. The mesoporous ACF (surface area = 2225 $m^2$/g, pore size=1.93 nm) showed increased mesopore(pore size=1~3nm) volume from 0.055 cc/g to 0.408 cc/g compared to its raw ACF. The charging capacity of the EDLC which uses the prepared mesoporous ACF also increased from 0.39 F/$cm^2$ to 0.55 F/$cm^2$. From these results, it can be known that the electrochemical properties of EDLC are mainly dependent on the specific surface area, but above the surface area 2200 $m^2$/g, it is the mesopore volume that affects the performance of the capacitor considerably. Because the increased mesopore volume results in a decreased ion mobility resistance, the charge capacitance is enhanced.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.723-729
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• 2016

This study compared fin-tube and parallel-flow heat pipes for their sensible heat exchange rate, heat recovery amount, and air-side pressure drop. Tests were done with different refrigerant charging rates of 40-60% vol. and air flow rates of 300-1,400. The sensible heat exchange rate was highest for both types of heat pipes at a working fluid charge of 40% vol. and low flow rate. For the parallel-flow heat pipe, the 60% vol. charge is too high and results in a low sensible heat exchange rate. The reason is that the thicker liquid film of the tube wall deteriorates the heat transfer effect. Hence, the optimal charging rate is 40 to 50% vol. The evaporator heat pipe has a larger air-side pressure drop than the condenser section heat pipe. The reason is considered to be condensation water arising from the evaporator surface. Compared to the fin-tube heat pipe, the parallel-flow heat pipe showed better performance with a working fluid charging rate of 48%, volume of 41%, and an air-side pressure drop about 37%.