• 한국전산유체공학회지
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• 제14권2호
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• pp.59-67
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• 2009

An accurate prediction of the bypass flow is of great importance in the VHTR core design concerning the fuel thermal margin. Nevertheless, there has not been much effort in evaluating the amount and the distribution of the core bypass flow. In order to evaluate the behavior and the distribution of the coolant flow, a unit-cell experiment was carried out. Unit-cell is the regular triangular section which is formed by connecting the centers of three hexagonal blocks. Various conditions such as the inlet mass flow rate, block combinations and the size of bypass gap were examined in the experiment. CFD analysis was carried out to analyze detailed characteristics of the flow distribution. Commercial CFD code FLUENT 6.3 was validated by comparing with the experimental results. In addition, SST model and standard k-$\varepsilon$ model were validated. The results of CFD simulation show good agreements with the experimental results. SST model shows better agreement than standard k-$\varepsilon$ model. Results showed that block combinations and the size of the bypass gap have an influence on the bypass flow ratio but the inlet mass flow rate does not.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2008년도 추계학술대회 초록집
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• pp.15-16
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• 2008

In case manufacturing COF, through hole should be made to be used for a pathway connecting the conductive layers of its both faces. In case Cu-plating inside of through hole with electroless plating way, contact between Cu and PI film gets bad to be fell apart from PI by the impact of applying to the electric devices. Therefore, after sputtering is applying on inner through hole, then a method to perform electroplating process. In this study, after changing sputtering condition to manufacture FCCL, we looked the changeability of the upper PI and inner hole Cu layers. Making use of RF Magnetron sputtering equipment, we coated Cu thin film and Cu-plated on it through electroplating. After cold-mounting the completed FCCL, we examined hole section through an optical microscope. From the result of test, with parameters deposition pressure and deposition time, both the thickness of the hole plated layer and PI plated upper layer increased at regular rate, increasing the thickness of Cu sputter layer. However, from the result of test in increasing RF-power, we could know the increment rate of hole plated layer is considerably greater than that of PI plated upper layer. Therefore, we finally acquired good result; if you want only to increase the plated layer of inner hole, it's much better to increase RF-power.

• 한국재료학회지
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• 제32권11호
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• pp.474-480
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• 2022

Lithium-ion batteries (LIBs) are powerful energy storage devices with several advantages, including high energy density, large voltage window, high cycling stability, and eco-friendliness. However, demand for ultrafast charge/discharge performance is increasing, and many improvements are needed in the electrode which contains the carbon-based active material. Among LIB electrode components, the conductive additive plays an important role, connecting the active materials and enhancing charge transfer within the electrode. This impacts electrical and ionic conductivity, electrical resistance, and the density of the electrode. Therefore, to increase ultrafast cycling performance by enhancing the electrical conductivity and density of the electrode, we complexed Ketjen black and graphene and applied conductive agents. This electrode, with the composite conductive additives, exhibited high electrical conductivity (12.11 S/cm), excellent high-rate performance (28.6 mAh/g at current density of 3,000 mA/g), and great long-term cycling stability at high current density (88.7 % after 500 cycles at current density of 3,000 mA/g). This excellent high-rate performance with cycling stability is attributed to the increased electrical conductivity, due to the increased amount of graphene, which has high intrinsic electrical conductivity, and the high density of the electrode.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.7-13
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• 2011

RAMS is the procedure to maximize the reliability and availability of systems with managing operation rate, the frequency of failure in the system and repair method. Recently, all system life-cycle focusing on RAMS process has been rapidly developing in the field of railway vehicles, for example, applying th reliability management techniques for procurement and disposal of EMU. In particular, global economic recession require to reasonable measures for the EMU maintenance costs under the circumstances therefore, an alternative solution based on RCM(Reliability Centered Maintenance) which is the optimal maintenance method is interested. In this study, the state of being critical of each component and a primary factors was analyzed to improve VVVF inverter of the line 7 EMU by applying FMECA process. Furthermore, this paper showed the impact of connecting between the main and sub system. Based on these data, critical components according to malfunction ratings were classified by screening measures and improvements for each components was summarized.

• 소성∙가공
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• 제10권4호
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• pp.302-310
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• 2001

The twisting and extrusion process of the product with involute helical fin from the round billet is developed by the upper bound analysis. The twisting of extruded product is caused by the twisted inclined die surface connecting the die enterance section and the die exit section linearly. In the analysis, the internal shear surface is defined as the curved twisted plane from the twisting of die surface and the shear work is calculated by the consumption of shear energy. The increase rate of angular velocity is determined by the minimization of plastic work. The angular velocity of die exit can be controlled by the land length and the length of inclined die. The alular velocity assums to be increased linearly by the axial distance from the die enterance to the die exit. The results of the analysis show that the angular velocity of the extruded product increases with the die twisting angle, the reduction of area, and decreases with the die length, the friction constant.

• 한국초전도ㆍ저온공학회논문지
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• 제5권1호
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• pp.92-96
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• 2003

This paper deals with the characteristics of persistent current switch (rCS) system fer applied HTS magnet system. To apply the high-Tc superconductor in superconducting machine such as motror, generator, MAGLEV, MRI, and NMR, the study on high-Tc superconducting persistent current mode must be performed. In this experiment, the PCS system consists otd superconducting magnet, PCS and magnet power supply. The superconducting magnet was fabricated by connecting four double pancake coils (DPCs) in series. The PCS was inductive double pancake coil type and heated up by the SUS 303L tape heater. The optimal length of PCS was calculated and thermal quench state of PCS was simulated by using finite element method(FEM) and compared with experimental results. The optimal energy to normalize the PCS was calculated and introduced. Finally, the persistent current was observed with respect to various ramping up rate and magnitude of charging current.

• 센서학회지
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• 제27권2호
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• pp.137-141
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• 2018

Detecting the ego-lane of a vehicle (the lane on which the vehicle is currently running) is one of the basic techniques for a smart car. Vision sensing is a widely-used method for the ego-lane detection. Existing studies usually find road lane lines by detecting edge pixels in the image from a vehicle camera, and then connecting the edge pixels using Hough Transform. However, this approach takes rather long processing time, and too many straight lines are often detected resulting in false detections in various road conditions. In this paper, we find the lane lines by scanning only a limited number of horizontal lines within a small image region of interest. The horizontal image line scan replaces the edge detection process of existing methods. Automatic thresholding and spatiotemporal filtering procedures are also proposed in order to make our method reliable. In the experiments using real road images of different conditions, the proposed method resulted in high success rate.

• 한국안전학회지
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• 제25권3호
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• pp.131-136
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• 2010

This study deals with the accident models of arterial link sections by vehicle type. The objectives are to analyze the characteristics of accidents, and to develop the models by type. In pursuing the above, this study uses the data of 414 accidents occurred on 24 major arterial links in 2007. The main results analyzed are as follows. First, the number of accidents is analyzed to account for about 47% in passenger car, 15% in SUV and 10% in trucks. Second, 3 Poisson regression models which are all statistically significant are developed using passenger car, SUV and truck as dependant variables. Finally, AADT and the number of traffic islands as common variables, and the number of pedestrian crossings, lanes, connecting roads, intersections(4-Leg), rate of medians and the number of bus stops as specific variables of the models are selected.

• 한국통신학회논문지
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• 제22권11호
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• pp.2381-2387
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• 1997

The Communication Processing Systems(CPS) is a gateway that supports 01410 hitel service by connecting the public switched telephone network(PSTN) with the public switched data network(PSDN). The CPS is made the meausred rate accounting method for the biling after extracting the originating numbers from the nearest local PSTN. In this paper, a numerical simulation is carried out on the offered traffic per user on the telephone access part of the CPS according to change of call loss probability and also propose the proper number of channels based on the simulation results.

• 한국반도체및디스플레이장비학회:학술대회논문집
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• 한국반도체및디스플레이장비학회 2007년도 춘계학술대회
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• pp.244-249
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• 2007

In this paper, in order to get the characteristics of the lithium secondary cell, such as cycle life, charge and discharge characteristic, temperature characteristic, self-discharge characteristic and the capacity recovery rate etc, we build a mathematical model of battery. In this one-dimensional model, Seven governing equations are made to solve seven variables $c,\;c_s,\;{\Phi}_1,\;{\Phi}_2,\;i_2,\;j\;and\;T$. The mathematical model parameters used in this model have been adjusted according to the experimental data measured in our lab. The connecting research of this study is to get an accurate estimate of the capacity of battery through comparison of results from simulation and fuzzy logic system. So the result data from this study is reorganized to fit the fuzzy logic algorithm.