• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.4
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• pp.772-779
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• 2015

In this paper,a reconfigurable multi-band mobile antenna with switching line for LTE band 13, GSM, K-PCS, WCDMA band. The proposed antenna is planar strip line design and composed of stub shorted to the ground plane and two switching line for proposed band operation. To obtain the optimized parameters, we used the simulator, Using the obtained parameters is fabricated. The numerical and experiment results demonstrated that the proposed antenna satisfied the -6 dB impedance bandwidth requirement while simultaneously covering when the state of sw1 and sw2 on for LTE band 13, the state of sw1 off and sw2 on for GSM, K-PCS, the state of sw1 off and sw2 off for WCDMA. Respectively and characteristics of gain and radiation patterns are determined for a reconfigurable multi-band mobile terminal.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.2
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• pp.137-144
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• 2011

A Simple equivalent circuit model is developed for a wireless energy transfer system via coupled magnetic resonances and a practical design method is also provided. Node equations for the resonance system are built with the method, expanding on the equations for a transformer, and the optimum distances of coils in the system are derived analytically for optimum coupling coefficients for high transfer efficiency. In order to calculate the frequency characteristics for a lossy system, the equivalent model is established at an electric design automation tool. The model parameters of the actual system are extracted and the modeling results are compared with measurements. Through the developed model, it is seen that the system can transfer power over a mid-range of a few meters and impedance matching is important to achieve high efficiency. This developed model can be used for a design and prediction on the similar systems such as increasing the number of receiving coils and receiving modules, etc.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.294_295
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• 2009

Superconducting fault current limiter (SFCL) is an power device of a novel concept. While SFCLs generate no ohmic loss during the operation carrying normal currents, they can limit fault currents very fast making large impedance by their quench characteristics. In 2006, KEPCO has developed a distribution class hybrid type SFCL by a collaborative research project with LS industrial systems. The SFCL has merits in practical and economical points of view. In the SFCL, the superconductor just plays a role of a fault detector and the current limiting is completed by the other current limiting element made of normal metals throu호 the line commutation. As a result, the required amounts of superconductors can be reduced considerably. Consequently, the hybrid SFCL can be fabricated with small size and cost, maintaining perfect current limiting performance. Currently, KEPCO is carrying out a research project at Gochang power test center for the purpose of the verification test of the 22.9 kV/ 630 A class SFCL for the practical application in real grid. Through the project, a long term operational test and fault current test will be done. In this paper, the back ground of development and installation of the SFCL will be explained and the operation plan of the SFCL for the verification test is also introduced.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.378-378
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• 2009

The ionic liquid-based sulfonated hydrocarbon composite membranes was prepared for use in anhydrous high temperature-polymer electrolyte fuel cells (HT-PEFCs). Ionic liquid behaves like water in the composite membranes under anhydrous condition. However the composite membranes show a low conductivity and high gas permeability as the content of ionic liquid increases due to its high viscosity and content of ionic liquid, respectively. Hence, in order to enhance the proton conductivity and to reduce the gas permeability of the composite membranes with low content of ionic liquids, the acid containing a common ion of ionic liquid was added to the composite membranes. The characterization of composite membranes was carried out using small-angle X-ray scattering (SAXS), thermogravimetric analyzer (TGA) and impedance spectroscopy. As a result, the composite membranes containing acid showed higher proton conductivity than those with no acid under the un-humidified condition due to a decrease in viscosity. In addition, the proton conductivity of composite membranes increased with increasing mole concentration of acid.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1994.10a
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• pp.231-237
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• 1994

컴퓨터의 눈부신 발달에 힙입어 실험 또는 해석적 방법으로 일반 구조물이나 기계구조물의 진동특성을 손쉽고 정확하게 파악하는 것이 가능하게 되었다. 그런데 최근의 산업현장은 지금까지의 정확한 구조해석에만 그치지 않고 이를 바탕으로 강도 개선, 재료 절감을 통한 원가절감, 중량 최소화 문제등의 차원에서 동적인 특성의 변경을 요구하고 있다. 이러한 문제는 그 중요성에도 불구하고 여전히 설계자의 경험이나 시행착오에 의존하고 있는 실정이다. 본 연구에서는 구조물 결합부분에 주목하여 동특성의 변경 문제를 해석하고자 하였다. 즉 거의 모든 구조물이 결합부를 가지고 있는데 결합부 특성을 정확히 파악할 수 없기 때문에 리벳이나 보울트나 어떤 특수한 형태 결합부가 구조물의 특성에 주는 영향을 예측하기 어렵다. 이러한 결합부이 특성을 알아내고 구조물 동특성 변경 및 개선안을 제시하는 최적설계를 위해 감도해석기법은 아주 유효하게 쓰일 수 있다. 한편 구조물의 대형화, 복잡화는 구조물 동특성 해석에 더욱 많은 계산시간과 용량이 큰 전자계산기를 필요로 하게 되었으며, 분계의 결합부위가 변경되거나 결합형태가 변했을 때 전계의 동특성을 다시 해석할 필요없이 분계만의 정보로부터 전계의 동특성을 알아낼 필요가 생겼다. 이러한 의미에서 구조물의 분계로부터 전계의 동특성을 해석을 위한 부분구조합성법이 대두되게 되었다. 본 연구에서는 이러한 감도해석과 부분구조합성법의 공통된 문제를 일치화하고자 하였다. 즉 감도해석기법을 이용하여 필요한 구조물의 동특성에 부합하는 결합부의 최적한 설계변수를 규명하였고 이렇게 구해진 결합부의 설계변수와 분계의 정보를 알고리즘이 비교적 간단하고 오차가 적은 축소임피던스 합성법에 적용하여 전계의 동특성을 해석함으로써 감도해석기법과 축소임피던스 합성법의 통합적용이 최적설계와 이에 따른 동특성 해석에 효과적인 방법임을 보이고자 하였다. 대상구조물은 구조물 결합의 기본적인 형태인 T형을 선택하였다. T형 구조물은 분계 A(16개의 사각요소)와 분계 B(8개의 사각요소)로 이루어져 있으며 두개의 스프링으로 결합되어 있다. 설계변수는 강성에 국한하였으며 결합부의 결합형태는 탄성결합과 강결합으로 하였다. 감도해석과 축소임피던스 합성법에 의해 구해진 고유진동수와 FRF를 상용 유한 요소 해석 패키지인 MSC/NASTRAN을 통하여 검증하여 이 연구의 타당성을 검토하였다.

• Journal of Korean Society of Transportation
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• v.33 no.2
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• pp.204-213
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• 2015

The congestion of pedestrians impedes the utilization efficiency of a subway station. Conflicts among pedestrians due to unseparated pedestrian flows not only increase the impedance of pedestrian mobility but also negatively affect on pedestrian safety. This paper analyzes the travel characteristics of bi-directional pedestrian flow based on microscopic movements, and evaluates the operation efficiency on separating the traffic line. The subway station was simulated in a 2-D grid structure by applying Discrete Element Method, and the movement is organized in each cell of the grid. As a result, the model explicates that separating the traffic line and encouraging the 'Keep right rule' would be mostly effective for the conflicting flows. Therefore, applying the 'Walking Guidance System' would be efficient to improve the pedestrian convenience and mobility.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.352-355
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• 2006

As the stainless steel has good corrosion resistance, mechanical property and ease of manufacture, it has been studied as the candidate material of metallic bipolar plate for automotive PIMFC. But, metal is dissolved under fuel cell operating conditions Dissolved ions contaminate a membrane electrode assembly (MEA) and, decrease the fuel cell performance. In addition, metal oxide formation on the surface of stainless steel increases the contact resistance in the fuel cell. These problems have been acted as an obstacle in the application of stainless steel to bipolar plate. Therefore, many kinds of coating technologies have been examined in order to solve these problems. In this study, stainless steel was coated in order to achieve high conductivity and corrosion resistance by several methods. Contact resistance was measured by using a tensile tester and impedance analyzer Corrosion characteristics of coated stainless steel were examined by Tafel-extrapolation method from the polarization curves in a solution simulating the anodic and cathodic environment of PEMFC. Fuel cell performance was also evaluated by single cell test. We tested various coated metal bipolar plate and conventional and graphite were also tested as comparative samples. In the result, coated stainless steel bipolar plate exhibited better cell performance than graphite to bipolar plate.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.319-319
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• 2013

Even though the fabrication methods of metal oxide based thin film capacitor have been well established such as RF sputtering, Sol-gel, metal organic chemical vapor deposition (MOCVD), ion beam assisted deposition (IBAD) and pulsed laser deposition (PLD), an applicable capacitor of printed circuit board (PCB) has not realized yet by these methods. Barium Strontium Titanate (BST) and other high-k ceramic oxides are important materials used in integrated passive devices, multi-chip modules (MCM), high-density interconnect, and chip-scale packaging. Thin film multi-layer technology is strongly demanded for having high capacitance (120 nF/$mm^2$). In this study, we suggest novel multi-layer thin film capacitor design and fabrication technology utilized by plasma assisted deposition and photolithography processes. Ba0.6Sr0.4TiO3 (BST) was used for the dielectric material since it has high dielectric constant and low dielectric loss. 5-layered BST and Pt thin films with multi-layer sandwich structures were formed on Pt/Ti/$SiO_2$/Si substrate by RF-magnetron sputtering and DC-sputtering. Pt electrodes and BST layers were patterned to reveal internal electrodes by photolithography. SiO2 passivation layer was deposited by plasma-enhanced chemical vapor deposition (PE-CVD). The passivation layer plays an important role to prevent short connection between the electrodes. It was patterned to create holes for the connection between internal electrodes and external electrodes by reactive-ion etching (RIE). External contact pads were formed by Pt electrodes. The microstructure and dielectric characteristics of the capacitors were investigated by scanning electron microscopy (SEM) and impedance analyzer, respectively. In conclusion, the 0402 sized thin film multi-layer capacitors have been demonstrated, which have capacitance of 10 nF. They are expected to be used for decoupling purpose and have been fabricated with high yield.

• Korean Journal of Community Nutrition
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• v.3 no.2
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• pp.190-201
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• 1998

This study was carried out with 505(243 boys and 262 girls in the Sungnam area) high school students to investigate the effects of eating behavior and anthropometric variables of weight and height on excercise performance. General characteristics about subjects and eating behavior were surveyed by questionnaire, anthropometric data were collected using two methods. The weight and height of subjects in 1996 were measured, but the same data in 1995 were collected from health records of each student. Body fat content of subjects was measured by BIA(Body Impedance Analysis). The grades of exercise performance, which were evaluated by physical education teachers were collected from records of a physical strength test score of each subject. From these, the following result were found. Groups with different eating behaviors such as skipping meals, overeating, food preference for a specific food(milk, carbonated drink etc.) were significantly different in their weight and height and body fat contents. The growth rate of height in first and second grade boys was significantly higher than that for grade boys. The amount of weight gain from second grade to third grade was significantly more than that of other grades both for boys and girls. The mean of BMI was $21.66\pm{2.95}$ in boy, $21.50\pm{2.62}$ in girls. The percentage of body fat was $24.91\pm{6.55%}$ in boy $34.73\pm{4.88%}$ in girls. Amounts of body fat were significantly increased in third grade. The group with higher fat content and the higher BMI group had lower values of physical strength. And the ability to exercises perform decreased significantly by promotion of grade. The other variables such as degree of concern about weight control and preference of exercise, and frequencies of exercise per week were significant factors in body fat content and physical strength. As a countermeasure for these problems, nutrition and health education must be developed for adolescents and a practical, proper physical activity guidance campaign for them is necessary.

• Journal of Biosystems Engineering
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• v.20 no.3
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• pp.226-235
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• 1995

An unmanned speed sprayer was developed using a remote control and an inductive cable guidance systems to protect operators and environment from hazardous pesticides. The sprayer consists of a remote control system, an induction system, obstacle detectors, control actuators and an one-chip microcomputer. The sprayer can be operated by the induction guidance and/or remote control. The following summarize characteristics of the developed speed sprayer. 1) Both the remote control and the induction guidance operation were possible with the developed speed sprayer. 2) Sixteen functions of the forwarding, backing, halting, steering, 3-way valve for nozzles and fan operating etc. were utilized on the remote control system. 3) It was concluded that the DTMF method, having less transmitting error, performed better than the FSK method for an agricultural remote controller. A radio station may be necessary. 4) The digital inductive guidance system, consisting of five low-impedance detection coils and a window comparator circuit, performed better than the analog detecting system, guiding route using inductive voltage differential from tow detection coils.