• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.224-227
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• 2011

In order to determine the enthalpy profile in the high temperature transpiration cooling test facility for the air-breating engine compartments, theoretical calculation and measurement for the flow of the test section are performed. The mass averaged enthalpy value determined by the heat balance and sonic throat methods is 10 MJ/kg. The centerline enthalpy value measured using the slug type copper calorimeter is 15 MJ/kg. Typically, the ratio of centerline and mass averaged enthalpy should be varies from 1.4 to 4. This facility has lower bound of enthalpy profile. It will be effective in testing of high temperature transpiration cooling.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.201-203
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• 2007

본 논문에서는, 연료전지 시스템의 기계적 주변장치 (MBOP)와 전기적 주변장치 (EBOP)의 최적 설계를 위해서 PEMFC 스택을 전기화학반응을 기초로 모델링한다. 모델링을 위해 기본적인 PEMFC의 구조와 동작 원리를 설명한다. 연료전지의 이론적 최고 전압인 평형전위를 깁스 자유에너지와 네른스트 방정식으로 유도한다. 전류밀도에 따른 전압 손실인 활성화, 저항, 농도 분극현상을 표현하기 위해서 수식을 유도한다. 수소가 이온화되지 못하고 산소극으로 넘어가서 발생되는 연료손실 및 내부전류와 지속적인 정역반응인 교환전류도 모델링된다. 평형전압에서 각 분극을 뺀 실제 운전 전압을 시뮬레이션하고, 유량과 압력에 따른 출력 특성을 시뮬레이션 한다. 부하변동 시 출력특성을 시뮬레이터와 실험결과로 비교한다.

• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.864-869
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• 1998

In this work, the solid-liquid equilibria (SLE) of some aromatic organic mixtures including benzene, widely used as an industrial solvent, were measured by static method using our own made experimental apparatus. The accuracy and reproducibility of apparatus were tested by comparing experimental results with literature values for 1-dodecanol+cyclohxane and benzene + p-xylene systems. The SLE for new binary systems of benzene+aniline, benzene+nitrobenzene, p-xylene+cyclohexane were measured afterwards and compared with the calculated values by modified UNIFAC(Dortmund) equation.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.9
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• pp.733-739
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• 1989

Fixed boundary MHD static equilibrium for the axisymmetric toroidal plasma is analyzed numerically. The Grad-Shafranov equation is solved using finite element method. The toroidal current term is expressed by plasma pressure and toroidal field function. The numerical results are compared to the Solovev analytic equilibrium for the verification of the solution. For SNUT-79 tokamak device in Seoul National University, the flux surfaces, the toroidal current profiles, the safety factor q and average beta values are obtained when the p and g profiles are varied.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.544-549
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• 2017

This paper aims to examine the effect of rotational fluid motion about the efficiency of the gas - liquid ejector, which is a core unit in a ship equilibrium water treatment system. The ejector is a device for injecting ozone into ship equilibrium by the negative pressure generated by exchange of momentum between water and ozone. The existing ejector ejects the driving fluid with a simple form. In this paper, however, a rotation induction device is applied to the driving nozzle so that the driving fluid can be rotated and injected. To investigate the flow characteristics by the rotational movement of the driving fluid, CFD was used. The pressure and flow rate of the driving fluid, the negative pressure and suction flow rate of the suction fluid in the suction part, and the discharge pressure were predicted. On the basis of the results, the efficiency of the ejector using the rotation induction system was 22.25%, which was about 1.7% better than that of the existing ejector. Finally, to verify the feasibility of the CFD, an experiment was conducted on the ejector using the rotation induction device and the results were similar to those of the CFD.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.4328-4334
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• 2015

We determined a method to determine marine planktonic organism viability using Evan's blue, Aniline blue, and 5-choromethyfluorescein diacetate (CMFDA). The Evan's blue and Aniline blue methods produced bright blue light for dead phytoplankton and zooplankton and were the best dyes to detect dead cells. The staining efficiency of Evan's blue and Aniline blue were ${\geq}90%$ of the original field sample. However, it was difficult to test the efficiency of a ship's ballast water treatment system because detection of living cells. In contrast, the CMFDA method, which is based on measuring cell esterase activity using a fluorimetric stain, was the best dye to detect live cells of almost all phytoplankton species, and staining efficiency was 70%. The CMFDA method is similar to the fluorescein diacetate (FDA) staining method. Therefore, we estimated viability of phytoplankton species using a double-staining method by combining CMFDA and FDA to determine optimum staining efficiency. As a result, the frequency of dying cells based on the double-staining method was 95%, which was significantly higher than that of single CMDFA staining. Our results suggest that a CMDFA + FDA assay is more effective to determine survival of marine plankton and that this method was applicable to investigate the efficacy of a ship's ballast water treatment system.

• Electronics and Telecommunications Trends
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• v.5 no.3
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• pp.52-59
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• 1990

통신신호가 통신회선을 통하여 전파될 때, 선로에 불평형이 나타나는 경우 가입자 선로와 대지간에 유도전류가 발생하여 대지로 흘러가게 되며 통신망의 성능에 영향을 미치게 된다. 본고에서는 통신회선의 불평형정도를 나타내는 평행도에 관하여 그 개념을 기술하고 각국에서 제시된 기준을 비교.분석한다.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2012.06a
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• pp.202-202
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• 2012

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.9
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• pp.875-882
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• 2011

In the present study, the imbalance in the axial-thrust and variation in the volumetric efficiency that occurred during the trimming of impeller diameter were investigated. The present study was focused on low-specific-speed multistage centrifugal pumps with a balancing piston as the balancing mechanism. The effects of impeller trimming on the axial-thrust balance in multistage pumps with horizontal and vertical axes were compared. The results showed that impeller trimming resulted in an additional axial-thrust acting in direction of pump inlet. The axial-thrust imbalance due to impeller trimming was more severe in the vertical-axis pumps than in the horizontal-axis pumps. The rate of increase in the diameter of the balancing piston, which was proportional to the rate of impeller trimming, was evaluated to maintain the axial-thrust balance. Furthermore, a simultaneous increase in the piston length and piston diameter was more effective for reducing the axial-thrust imbalance along with the volumetric efficiency drop.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.481-488
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• 2000

This paper presents a new passive gravity -compensating system for articulated robot manipulators. The system, which consists of linear zero- free -length springs, achieves exact counterbalancing o f the gravitational loads throughout the entire range of the manipulator workspace, A basic concept is to design springs such that the total potential energy of the system including the manipulator and the springs should be maintained constant. A prototype has been developed for a direct-drive five-bar manipulator and its performances have been investigated. Results show that the gravity-induced motor torques have been reduced to less than 5% of those of uncompensated robots. Also, the gravity-compensating system simplifies the position control algorithm while maintaining the trajectory-tracking errors in a satisfactory level. In conclusion, the proposed system efficiently improves the manipulator performances by reducing the driving motor size and the energy consumption as well as by simplifying the control systems.