• Journal of Electrical Engineering and Technology
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• v.7 no.2
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• pp.225-229
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• 2012

This paper proposes a reduced-scale simulator that can replace numerical analytic methods for the estimation of potential distribution caused by ground faults in various grounding systems. The simulator consists of a hemispherical electrolytic tank, a three-dimensional potential probe, a grounding electrode, and a data acquisition module. The potential distribution is measured using a potentiometer with a position-tracing function when a test current flows to the grounding electrode. Using the simulator, we could clearly analyze the potential distribution for a reduced- scale model by one-eightieth of the buried depth and length of the grounding rod and grounding grid. Once both the shape of the grounding electrode and the fault current are known, the actual potential distribution can be estimated.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.16 no.1
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• pp.103-108
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• 1987

The heat transfer processes taking place in the side wall of a thermocline enclosure have been analyzed for idealized conditions based on the assumption that, at any instant time, side wall heat transfer processses are independent of the thermocline bulk motion. However, the axial tempera-ture distribution in the thermocline core provides the means for specifying the liquid medium-side boundary condition to the enclosure side wall. A picture is drawn which reflects the side wan response to thermocline bulk motion within the frame work of a quasi-steady analytic approach. For valves of the parameters typical of systems of engineering interest, the analysis shows that a significant amount of heat transfer short - circuiting can take place along the side wall enclosure. This phenomenon is favored by high values of $H_l$ and low values of P and $H_g$ respec-tively. The location of the point of zero normal heat flux on the side wan can be expected to mark, approximately, the region of confluence of two sidewall boundary flows respectively driven by the buoyant effects.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1C
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• pp.47-55
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• 2003

This paper proposes a composition method of mosaic image from the compressed MPEG-2 video stream, in which the displacement between successive frames according to the camera operation is estimated directly from the information involved in the stream. In the proposed method. the approximated optical flow is constructed from motion vectors of macro blocks, and it is used to determine the parameters of the displacements according to the camera operation associated with pan and tilt. The extracted parameters are used to determine the geometric transform of successive video frames in order to construct a mosaic image. The construction of mosaic uses several blending techniques including the one proposed by Nichols in which an analytic weight is used to determine pixel values. Through the experiment, the blending technique based on analytic weights was superior to the others such as averaging and median-based techniques. It provided more smooth changes in background and made use of instantaneous frame information to construct a mosaic. The mosaic in the paper puts the emphasis on the reduction of computation because it is constructed from the motion vectors included in the compressed video without decoding and recalculating exact optical flows. The constructed mosaic can be used in the retrieval of the compressed video as the representative frame of a shot.

• Nuclear Engineering and Technology
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• v.49 no.1
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• pp.148-164
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• 2017

The focus on the issues surrounding spent nuclear fuel and lifetime extension of old nuclear power plants continues to grow nowadays. A transparent decision-making process to identify the best suitable nuclear fuel cycle (NFC) is considered to be the key task in the current situation. Through this study, an attempt is made to develop an equilibrium model for the NFC to calculate the material flows based on 1 TWh of electricity production, and to perform integrated multicriteria decision-making method analyses via the analytic hierarchy process technique for order of preference by similarity to ideal solution, preference ranking organization method for enrichment evaluation, and multiattribute utility theory methods. This comparative study is aimed at screening and ranking the three selected NFC options against five aspects: sustainability, environmental friendliness, economics, proliferation resistance, and technical feasibility. The selected fuel cycle options include pressurized water reactor (PWR) once-through cycle, PWR mixed oxide cycle, or pyroprocessing sodium-cooled fast reactor cycle. A sensitivity analysis was performed to prove the robustness of the results and explore the influence of criteria on the obtained ranking. As a result of the comparative analysis, the pyroprocessing sodium-cooled fast reactor cycle is determined to be the most competitive option among the NFC scenarios.

• Korean Institute of Interior Design Journal
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• v.26 no.3
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• pp.45-54
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• 2017

A social phenomenon that occurs in a physical space is said to be a complex system. However, space syntax, which is commonly employed by researchers to identify such social phenomena, has various limitations in interpreting their complexity. On the other hand, agent-based modeling considers a variety of factors including the personality of the agent, objective-oriented work flows, estimation according to time flows and better prediction of space use through diverse parameters depending the situation, as well as the characteristics of the space. The agent-based method thus has the potentials to be developed as an alternative to space syntax techniques. In particular, discrete event driven simulation(DEVS), which is part of the agent-based modeling method, embraces the concept of networks just like space syntax, which allows a possible theoretical linkage in the future. This study suggests a procedural model of agent-based DEVS reflecting two different connection methods, i.e. connections between adjacent areas and those of the entire space, and attempts to identify the relationship between the local and regional indices of space syntax. A number of spaces were selected as examples-one for a preliminary experiment and eight modified for the main experiment-and space syntax and DEVS were applied to each of them. The comparative analysis of the results led to the conclusions as follows: 1) Adjacent connections were closely related to local indices, while the whole-space approach to regional indices. Local integration shows both characteristics. 2) Observation of the time flow model indicated a faster convergence with the range of 1 to 3-fold of the total time of one lap, with the error of less than 10%. 3) The heat map analysis showed more obvious characteristics of using the space for the entire space rather than adjacent connections. 4) Space syntax shows higher eligibility than ABM.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.1
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• pp.55-64
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• 1985

This thesis, intended to establish the design criteria of core wall of a Fill Dam, has determined after a series of twenty one analytic experiments on the seepage flows in various types of core wall that the rates of rise and fall of the seepage flow changing in accordance with the variation of core wall cross section, which is to say, the transformation of slope inclination. Particularily the appropropriate design inclination was examined for the sloped core wall. Putting the resulting values into the existing approximate theoretical function has revealed the volume of theoretical seepage flows. With this result, the experiment values was compared and interestingly enough, a theoretical formula was found which is considered to be the nearest one to the resulting values of the experiment. It is also discussed in the papers that the seepage alignment and flows in the sloped core wall section that inclined to the upstream and the adoptability of the theoretical function which has been known up to present. Based on the above mentioned study it is anticipated that thesis should be available for determination of the cross section in the core wall design of a Fill Dam as large amount of references as it can be.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.2
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• pp.30-37
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• 1998

This paper investigates the linear stability of wakes with special emphasis on the effect of chemical reaction. Velocity and density profiles for laminar flows are obtained from analytic profiles as well as from simulation. Wakes have two generalized inflection points and two unstable modes-sinuous and varicose modes. For analytical laminar profiles, sinuous modes are more unstable than varicose modes irrespective of density variation, which shows wakes will be destabilized by sinuous modes. Large velocity difference and density difference lead to more unstable wakes due to large momentum difference. For simulated laminar profiles, chemical reaction with stoichiometric chemistry increases temperature and stabilizes the flow due to increase in compressible reacting wades, flow becomes stable as velocity increases due to viscous dissipation.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.710-715
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• 2004

The design problem of manufacturing system is addressed, adopting the closed queueing network model with multiple loops and re-entrant flows. The entire design problem is divided into two hierarchical sub-problems of (1) determining the station configuration and (2) optimizing the lot constitution; then they are tackled by neighbor search algorithm (NSA) and greedy mean value analysis (GMVA), respectively. Unlike the conventional MVA concerning multi-class closed queueing networks, the GMVA doesn't stick to a fixed lot proportion; rather it tries to find the optimal balance. The NSA, on the other hand, improves the object function value by altering the station configuration successively with its superior neighbor. The moderate time complexity, presented in big-${o}$ notation, enables us to apply the method even to the large-size practical cases, and the CPU time of an enlarged problem can be approximated by the same equation. The validity of our analytic approach is backed up by simulation studies with a widespread simulation package.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.191-193
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• 2006

YBCO wire has a metal substrate to improve the texture structure and highly conductive layers to increase the cryogenic stability. When AC current flows in the YBCO wire, magnetic field which is generated by the AC current magnetizes the metal substrate and induces the eddy current in the stabilizing layer. To examine the effect of the metal substrate and the conducting layer on the transport current loss of YBCO wire, this paper presents the transport current loss of YBCO wire which has metal substrate and conductive layer. YBCO wire with Ni-W substrate and copper layer were chosen as the model HTS wire for numerical calculation. Finite element method has been used to calculate the transport loss and the results of numerical calculation was compared with analytic calculation suggested by Norris.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.9
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• pp.1217-1228
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• 1998

In order to elucidate the operational characteristics of rotating heat pipes, the internal flow patterns and heat transfer performance are investigated. Flow patterns and its transition are studied with various rotational speeds by visualizing flows established inside a rotating tube. To verify those results of analysis, 2 heat pipes of the same geometries but fill charge rates of 7, 30% were manufactured and submitted to operating tests. Comparison of experimental results on heat transfer rate show a fairly good agreement with the analytical results. The analysis reveals that the optimum charge ratio is ranged in 4~7% depending on the quantity of thermal loads. but the heat pipe with 7% of fill charge ratio reached dry-out limitation at heat flux of $q^{{\prime}{\prime}}=6.2kW/m^2$ lower than that of analytic results. Transition of flow regime was well related to the correlation by Semena & Khmelev on transient centrifugal Froude Number Frc. But hysteresis phenomenon was observed in transition of flow regime, when the rotational speed was stepwisely changed in the way to undergo 1 cycle.