• Journal of Soil and Groundwater Environment
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• v.13 no.5
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• pp.47-56
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• 2008

Temporal changes of metal solubility have been repeatedly observed in soils equilibrated with metal salt solutions. This phenomenon is known as aging, yet factors that affect the degree of metal aging remain largely unexamined. In this study, we compared the extent of aging on metal partitioning depending on soil, metal, and metal loading. Five soils spiked with four levels of Cd (2.5-20 mg ${kg}^{-1}$), Cu, and Zn (50-400 mg ${kg}^{-1}$) salt solutions were aged in the laboratory up to 1 year. The partitioning coefficient ($K_d$) of each metal was calculated from the ratio of total to dissolved metal concentration in samples collected at times ranging from 1 day to 1 year. The highest $K_d$ values for Cd, Cu and Zn were recorded in a Histosol, Andisol, and fine-textured Alfisol, respectively, whereas the lowest $K_d$ was recorded for an Oxisol and coarsetextured Alfisol. For all soils, a pattern of increasing Kd with aging was evident for Cd and Zn, but not Cu. Rapid Cu sorption was limited when dissolved organic matter was high in soils. In highly-retentive soils, $K_d$ values seemed to be insensitive to metal loading, although a longer period was required for the higher metal loadings to reach the same degree of metal aging as the lower loadings. In soils with low sorption capacity, the $K_d$ values were determined more by metal loading than by aging. Therefore, marked differences can be expected in the degree of metal aging in spiked soils by the soil type, metal and amount of metal added.

• Journal of Korea Soil Environment Society
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• v.4 no.2
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• pp.77-86
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• 1999

Partitioning of two hydrophobic organic compounds (HOCs), phenanthrene and naphthalene, to kaolinite and sorbed surfactants was studied to evaluate the feasibility of surfactant-enhanced remediation (SER) of contaminated subsurface systems. Sorbed surfactant partition coefficients. $K_ss$, showed a strong dependence on the surfactant sorption isotherms at low sorbed surfactant levels $K_ss$ values were at their highest and then decreased with increasing surfactant sorption densities. $K_ss$ values for SDS were always larger than corresponding $K_mic$values. For Tween 80, however. $K_ss$ values $K_mic$ were higher than $K_mic$ values only at the lower sorbed surfactant densities. HOC distribution between immobile and mobile phases varied with surfactant dose distribution coefficients increased initially with increasing surfactant concentrations and then decreased at higher doses. This observation shows directly the competition between sorbed and micellar surfactants for HOC partitioning. Overall results of this study demonstrate that surfactant sorption to the solid phase can lead to increases in HOC retardation in some SER applications. Therefore, before an SER process is selected, appropriate consideration of surfactant sorption and HOC partitioning to immobile versus mobile phases pertinent to a specific subsurface system must be contemplated.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.87-87
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• 1999

본 연구에서는 Pulsed Laser Deposition(이하 PDL)방법을 이용하여 Si기판에 (Ba,Sr)TiO3(이하 BST)박막을 MFS-FET(Metal-Ferroelectric-Semiconductor Field-effect Transistor)구조로 제조하였으며 BST박막의 강유전성이 BST 박막에 유도되는 응력에 어떤 영향을 받는지 살펴보았다. 본 연구에서는 완충막을 사용함으로써 BST박막과 완충막간의 격자부정합을 이용하여 BST박막에 강유전성을 유도하려고 하였다. 또한 MFS-FET구조의 BST박막에 유도되는 응력조절을 위하여 BST박막과 완충막의 두께를 변화하였으며 XRD를 통한 구조 분석 및 C-V test를 통한 전기적 특성을 관찰을 하였다. PLD법을 통해서 epitaxial 성장된 BST 박막에서는 Si에 epitaxial 성장된 완충막과의 격자부정합에 의한 BST박막내의 자발분극의 발생이 예상된다. 따라서, 본 연구는 강유전체의 자발분극에 의하여 발생되는 C-V 이력현상이 BST박막과 완충막과의 격자부정합에 의한 응력에 의해 발생될 것으로 예상하여, BST 박막에 유도되는 응력과 C-V 이력현상의 관계를 통하여 상온에서 상유전성을 갖는 BST가 응력에 의하여 어느 정도의 강유전성을 나타내는지를 밝히기 위해 진행되었다. 본 연구에서 사용된 완충막은 YSZ(Yttria Stabilized Zirconia)박막으로 0.4mTorrO2 분위기 하에서 600~80$0^{\circ}C$의 온도에서 증착하여 상형성을 살펴보았고 $700^{\circ}C$에서 epitaxial 성장을 확인하였으며 두께는 30~$\AA$으로 변화하였다. 또한 BST박막은 완충막과의 전압분배를 고려해 300~2000$\AA$으로 두께를 변화를 시키며 증착하였다. MFS 구조에서 Al 전극을 사용하여 완충막과 BST박막간의 두께 변화에 따른 Capacitance - Voltage(C-V) 측정을 하였으며 이를 통하여 강유전상의 특성인 C-V 이력현상을 관찰하였다. 그 결과 YSZ 박막에서는 C-V 이력현상이 나타나지 않았으며 BST 박막에서는 약 1.2V의 C-V이력현상이 보였다.

• Korean Journal of Social Welfare
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• v.57 no.3
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• pp.389-413
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• 2005

The OCB(organizational citizenship behavior), spontaneous extra-role behavior of social workers, plays very important role in the provision of qualitative service for the clients and the organizational performance of social welfare agencies. Starting from the importance of OCB for the effective organizational management, this study focuses on the effects of antecedents such as organizational justice(procedural and distributional) and trust in supervisor on the OCB. This study collected data from 360 social workers and 59 their supervisors working in the community welfare centers, paired the self-reported data and the supervisor-rated data, and analyzed the data through the SEM (Structural Equation Modeling) method. The findings of the study show that organizational justice(procedural and distributional) has no direct effect on the OCB, but indirect effect on the OCB through the mediator of trust in supervisor, and that procedural justice has more effect than distributional justice. This study suggests that the management of spontaneous behavior of social workers is not a separated fragmentary phenomenon but should be understood and managed comprehensively in the continuation of the perception of organizational members for the organizational management, the resulting affectivity toward their supervisor, and their behavior in the organizational life.

• Journal of the Korea Convergence Society
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• v.12 no.3
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• pp.197-204
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• 2021

This study relates to a device that increases efficiency by reducing air bubbles in a hydraulic system used in hydraulic machinery. The reverse design and product production of the bubble reduction device, which is a commercial product overseas, was carried out. Overseas commercial products were set as the base model, a rotary rotor and an inclined rotor were added to increase the surface area of the fluid, and an annular equal distribution part with a slot in the lower part was additionally applied to distribute the fluid evenly. In addition, internal flow trends were analyzed and a system that evenly distributes the linear flow of fluid was selected as the first improvement model. Based on the first improvement model, a case where the angle of the inclined rotor is 45° was selected as the second improvement model. Based on this, as a result of setting the exit width of the annular equally distributed part as a variable, the bubble reduction efficiency was highest when the lower slot diameter of the annular part was 10mm. Finally, the system in which the average cross-sectional flow velocity decreased by 147% compared to the Base Model was derived as the final improved model.

• Journal of the Korean Electrochemical Society
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• v.12 no.4
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• pp.329-334
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• 2009

This study is to develop a fuel cell system applicable to an in situ NMR (Nuclear magnetic resonance) diagnosis. The in situ NMR can be used in real time monitoring of various reactions occurring in the fuel cell, such as oxidation of fuel, reduction of oxygen, transport phenomena, and component degradation. The fuel cell for this purpose is, however, to be operated in a specifically designed tubular shape toroid cavity detector (TCD), which constrains the fuel cell to have a tubular shape. This may cause difficulties in effective mass transport of reactants/products and uniform distribution of assembly pressure. Therefore, a new flow field designed in a particular way is necessary to enhance the mass transport in the tubular fuel cell. In this study, a tubular-shaped close-type flow field made of non-magnetic material is developed. With this flow field, oxygen is effectively delivered to the cathode surface and the produced water is readily removed from the membrane-electrode assembly to prevent flooding. The resulting DMFC (direct methanol fuel cell) outperforms the open-type flow field and exhibits $36\;mW/cm^2$ even at room temperature.

• The KIPS Transactions:PartA
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• v.11A no.5
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• pp.355-364
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• 2004

These days, various clustering technologies have been adopted to construct web sites. High performance hardware switches have good performance, but have disadvantage of high cost for constructing small and middle-sized web sites. Now a days, many sites have been constructed with the LVS (Linux Virtual Server), which is free of charge and has good performance. Having a centralized load balancing with one front-end, the LVS causes a bottleneck when it receives all at once. In the paper, we suggest a way to remove the LVS bottleneck by providing multiple front-ends. In this architecture, all of cluster nodes act as both a front-end and a back-end. When the load of a node receiving requests is not large enough, the node responds to the client directly. When the load of a node is large enough, the node send the request to a node which is selected by a scheduling algorithm. The scheduling algorithm is discussed to balance loads between servers. While single front-end cluster raises the throughput curvedly, the multiple front-end cluster raises the throughput linearly.

• The Journal of Information Technology
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• v.1 no.2
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• pp.119-141
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• 1998

The main contents of WTO agricultural product agreement are composed of $\circled1$ market access $\circled2$ domestic subsidy and reduction of export subsidy $\circled3$ preferences for developing countries. But there still remains the possibility of laying a protection barrier within WTO regulations. That is to say, with the application of quota system, tariff rate quota system, or different quotas on different countries, and with the practices of government control trade and mark up. This paper is for studying the application of these protection barriers to minimize the impact of agricultural market opening.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.320-321
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• 2000

전기장 발광현상(Electroluminescence, 이하 EL)은 1936년 Destriau$^{[1]}$ 가 ZnS:Cu 분말에서 처음 전기장 발광현상을 발견한 이래 TFEL(Thin Film EL)소자의 구동전압을 감소시키는 문제는 ACTFEL(Alternating Current Thin Film EL)소자의 개발이후 계속적인 관심의 대상이 되어왔다. TFEL 소자는 전기적으로 용량소자이므로 전기장 인가시 각 층의 정전용량의 역수에 비례하는 전압이 분배되므로 동일한 조건의 형광막 사용시 소자의 구동전압을 낮추기 위해서는 절연박막의 두께를 줄이는 방법과 유전율이 높은 물질을 사용하는 방법이 있으나, 전자의 경우에는 박막의 결함이 생기기 쉬워 한계가 있기 때문에 고유전율 특성을 갖는 새로운 물질을 개발하는 것이 바람직하다. Ta$_2$O$_{5}$ 박막의 경우 작은 누설전류 특성과 고유전율 특성으로 인해 고집적을 요하는 반도체 분야에서 많은 연구가 진행되어 왔다. 또한 EL소자 응용시 효율면에서 우수한 특성이 기대되며, 특히 수분에 강한 특성을 가지고 있어 EL소자의 안정성이 예견되는 바이다. 본 연구에서는 Ta$_2$O$_{5}$ 박막의 산소 결핍에 따른 전기적 특성에 대해 연구하였고 Ta$_2$O$_{5}$ 박막을 이용한 저전압에서 구동가능한 전기장 발광소자를 제작하여 전기광학적 특성에 대해 연구하였다. (중략

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.223-227
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• 2011

유역 특히 상습침수지구의 통합관리는 유역이라는 한정된 범위 내에서 물에 영향을 미치거나 물에 의하여 영향을 받는 모든 인간 활동과 자연현상을 통합적으로 고려하는 것이다. 이러한 관점에서 유역관리는 유역 차원에서 물을 경제적이고 공평하게 관리하고 분배하여 수자원에 대한 장기적이고 지속가능한 해결방안을 마련하는 것이다. 여기에는 정부, 시민사회 및 기업 행위자가 사회경제적 개발목표와 정책형성, 집행계획을 수립하는 것으로부터 시작된다. 유역관리를 위한 의사결정들은 행위자들과의 영향으로 수정되며, 이런 과정에서 토지와 수자원에서 분쟁이 발생하며, 수자원 관리자는 자연현상, 물 사용, 재정적, 인적자원 및 외부적인 요인으로 인해 목적을 달성하는데 부합하지 않을 수도 있다. 효과적인 유역관리를 위해서는 제약조건하에서 수자원 관리자가 의사결정에 정보를 주고 주요 행위자들과 협력을 통해서 이루어 질 수 있다. 본 논문에서는 유역관리를 위한 의사결정을 행위자기반모형(Agent based Model, ABM)으로 이해하고자 하며, ABM은 유역관리의 이해당사자간의 정책과정을 도출하고 다양한 유역관리 대안을 평가하고 유역관리의 영향을 설명하는 모델이다. 본 모형은 관측자료를 통해 상향식 접근법으로 가능한 많은 세부사항을 모의할 수 있다. 분석과정은 자료의 수집, 모델 확립, 모델의 개발, 통계자료 수집 및 모델의 결과와 실제 시스템의 보충된 관측자료를 비교하는 검증 순으로 진행되며, 본 모델에서의 행위자는 과거의 행동으로부터 주위 환경의 반응하는 패턴을 확인하고 개발하며, 이러한 패턴은 정책들을 구별하기 위해서 이용되며, 이러한 과정에서 강화학습이 이루어진다. 이를 통해 행위자의 익숙한 방식의 합리적인 행동과 정책들의 상관관계를 평가할 수 있으며, 강화학습을 통해 실제적인 통계적인 모델이 가능하다.