• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.3
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• pp.219-232
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• 2013

This paper presents a microstrip antenna which recovers its resonant frequency and impedance shifted automatically by the approach of other objects such as hands. This can be used for telemetry sensor applications in the ultrahigh frequency(UHF) industrial, scientific, and medical(ISM) band. It is the key element that an frequency-reconfigurable antenna could be electrically controlled. This antenna is miniaturized by loading the folded plates at both radiating edges, and varactor diodes are installed between the radiating edges and the ground plane to control the resonant frequency by adjusting the DC bias asymmetrically. Using this voltage-controlled antenna and the micro controller peripheral circuits of reading the returned level, the antenna is designed and fabricated which recovers its resonant frequency and impedance automatically. Designed frequency auto recovering antenna is conformed to be recovered within a few seconds when the resonant frequency and impedance are shifted by the approach of other objects such as hand, metal plate, dielectric and so on.

• Applied Chemistry for Engineering
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• v.31 no.1
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• pp.97-102
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• 2020

Recently, various degradation mechanisms of lithium secondary battery cathode materials have been revealed. As a result, many studies on overcoming the limitation of cathode materials and realizing new electrochemical properties by controlling the degradation mechanism have been reported. Li-rich layered oxide is one of the most promising cathode materials due to its high reversible capacity. However, the utilization of Li-rich layered oxide has been restricted, because it undergoes a unique atomic structure change during the cycle, in turn resulting in unwanted electrochemical degradations. To understand an atomic structure deterioration mechanism and suggest a research direction of Li-rich layered oxide, we deeply evaluated the atomic structure of 0.4Li₂MnO₃_0.6LiNi_1/3Co_1/3Mn_1/3O₂ Li-rich layered oxide during electrochemical cycles, by using an atomic-resolution analysis tool. During a charge process, Li-rich materials undergo a cation migration of transition metal ions from transition metal slab to lithium slab due to the structural instability from lithium vacancies. As a result, the partial structural degradation leads to discharge voltage drop, which is the biggest drawback of Li-rich materials.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.4
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• pp.95-100
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• 2010

LED (Light Emitting Diode) is 85% of the applied energy is converted into heat that is already well known. Lately, LED chips increasing the capacity as result delivered to increase the heat of the LED products and module that directly related to life span and degradation. Thus, in industry the high-power LED chip to control the heat generated during the course of the study and the existing aluminum, copper adhesives, and uses MLC (Metal clad laminate) structures using low-cost FR4 and copper CCL (Copper Clad Laminate) to reduce costs by changing to a study being carried out. In this study, using low-cost CCL Class, mounted 1W LED chip to analyze changes in the thermal resistance. In addition, heat dissipation in the CCL to facilitate a variety of thermal via design outside of the heat generated by the LED chip to control and facilitate the optimal structure of the heat dissipation is suggested.

• Journal of the Korea Organic Resources Recycling Association
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• v.26 no.2
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• pp.95-103
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• 2018

As a guideline for desulfurization and dehumidification pretreatment facility for optimizing utilization of biogas, the $H_2S$ concentration is set at 150 % which can be treated with iron salts, dehumidification is the optimum value for generator operation, and the relative humidity applied at the utilization of biogas in EU is set at 60 %. We have set up the generator facility guidelines to optimize utilization of biogas. The appropriate amount of biogas should be at least 90 % of the total gas generation, and the capacity of generator facility should be set at 20~30 %. In order to equalize the pressure of the incoming gas the generator, a gas equalization tank should be installed and the generator room average temperature should be kept at $45^{\circ}C$ or less. Since the gas is not produced at a certain methane concentration in the digester, the efficiency is lowered. Therefore, it is required to install an air fuel ratio control system according to the change in methane concentration. Therefore, it is necessary to compensate for the disadvantages of biogasification facilities of organic waste resources and optimize utilization of biogas and improve operation of facilities. This study was conducted to optimize biogas utilization of type of organic waste(containing sewage sludge and food waste, animal manure), investigate the facilities problem and propose design, operation guidelines such as pre-treatment facilities and generators.

• Journal of the Korean Electrochemical Society
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• v.4 no.4
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• pp.152-159
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• 2001

Electric vehicle performance is very dependent on traction batteries. For developing the electric vehicles with high performance and good reliability, the traction batteries have to be managed to get maximum performance under various operating conditions. The enhancement of the battery performance can be accomplished by implementing battery management system (BMS) that plays important roles of optimizing the control mechanism of charge and discharge of the batteries as well as monitoring battery status. In this study the battery management system has been developed for maximizing the use of Ni/MH batteries in electric vehicle. This system provides several tasks: the control of charging and discharging, overcharge and over-discharge protection, the calculation and display of state of charge, safety and thermal management. The BMS was installed in and tested using the DEV5-5 electric vehicle developed by Daewoo Motor Co. and Institute for Advanced Engineering in Korea. The 18 modules of Panasonic Ni/MH battery, 12 V-95 Ah, were used in the DEV5-5. The high accuracy within the range of $3\%$ and the good reliability were shown in the test results. The BMS can also improve the performance and cycle life of Ni/MH battery pack as well as the reliability and safety of the electric vehicles (EV).

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.5
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• pp.463-470
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• 2006

This paper deals with a new 3-phase power quality disturbance generator. The proposed generator can provide phase jump as well as voltage sag, swell, outage, unbalance, and over and under voltage. The operating principle of the generator is described in each mode of disturbance. The magnitude of the phase jump is analysed and it is found that the magnitude is the function of the turn-ratios of the transformers consisting the generator. The scheme has simple structure compared with the conventional one, and the major components of the proposed scheme are SCR thyristor and transformer, which guarantees high reliability and cost-effective implementation of the generator. Furthermore, high efficiency can be obtained because there is no PWM switching of the semiconductor devices, and it is easy to control the system. Simulations are carried out to confirm the operation in each disturbance mode, and experiments has been done with 5kVA power rating. The usefulness of the proposed scheme is verified through simulation and experimental results. It is expected that the scheme can be applied to the performance test of the custom power devices such as UPS, DVR, DSTATCOM, and SSTS with cost-effective system.

• KSBB Journal
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• v.14 no.5
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• pp.621-627
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• 1999

A food waste composting apparatus of 450 L was designed for and tested with changing conditions of inlet air flow rate, agitation and inoculation. Agitation was done twice per day for 5 min and inlet air flow rate was set as 22.7 L/min for RUN 1. For RUN 2 and RUN 3, agitation was continuous, and inlet air flow rate was changed frequently as 10 L/min, 15 L/min and 20 L/min in order to maintain temp. above 5$0^{\circ}C$, and the concentration of $O_2$over 7 mol%. The compost of RUN3 was inoculated with 10 wt% of accomplished compost, and it was compared with RUN 1 and 2 to show the effect of inoculation. The composting rates of RUN 2 and RUN 3 were faster than that of RUN 1, because agitation was continuous and temperature was controlled in RUN 2 and RUN 3. Inoculated RUN 3 was better than RUN 1 and RUN 2 in the concentrations of $CO_2$and reduction of volatile solids. while the effect of inoculation on C/N ratios, pH change and the numbers of microoragnisms was not clearly appeared.

• Journal of Energy Engineering
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• v.17 no.1
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• pp.15-22
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• 2008

This study was carried out to investigate physical and chemical characteristics of the distillates and residue of Athabasca oilsand bitumen obtained from Canada, using a vacuum distillation unit. The distillates and residue produced from the vacuum distillation were characterized through atomic analysis, SARA analysis, and measurement of boiling point distribution, molecular weight, and API gravity. The vacuum distillation equipment consisted of a 6-litter volume vessel, a glass-packed column, a condenser, a reflux device, a flask fer collecting distillates, and a temperature controller. The cutting of distillates was performed with four steps under the condition of full vacuum and maximum temperature of $320^{\circ}C$. The results showed that the sulfur amount and average molecular weight of the distillates were significantly reduced compared to those of oilsand bitumen. As the cutting temperature increased, the hydrogen amount decreased but the sulfur amount and average molecular weight increased in the distillates.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.457-461
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• 2006

비점원 농촌유역으로부터 강우시 영양물질(질소, 인)의 유출특성을 파악하기 위해 2002년부터 2005년까지 5개의 강우사상을 대상으로 $2{\sim}12$시간 간격으로 유량 및 수질을 측정하였다. 강우사상시 TN농도는 유량이 증가함에 따라 상승하여 최대농도를 보인 후, 유량감소에 따라 농도가 감소하는 경우와 초기농도보다 높은 농도로 유지되는 경우의 두 가지 경향을 보였다. TP농도는 유량의 증가에 따라 급격한 상승을 보였고, 최대 값 이후 농도가 낮아져 거의 초기농도에 도달하였다. 또한, 초기농도에 대한 최대농도값의 비는 TP가 TN보다 크게 나타났다. 농촌 소유역에서의 초기유출현상(first-flush)은 40%의 누적유출량을 나타낼 때 TP의 누적유출부하량은 $70{\sim}86%$를 기록하여, 도시유역(60%)과 광역논(50%)보다 크게 나타났는데, 이는 농촌 소유역이 경사가 크고 밭 등에서 강우로 인한 토양침식 등의 영향을 크게 받기 때문으로 사료된다. 4개의 강우사상에 대한 질소의 용존성 성분의 비(TN/TDN비)는 93.6%를 나타내 질소는 대부분 용존성 형태로 유출되는 것으로 나타났고, 인의 용존성 성분의 비(TP/TDP비)는 25.4%를 나타내 인의 대부분 입자성 형태로 유출되는 것으로 나타났다. 따라서, 비점원 농촌유역으로부터 TN부하를 저감시키기 위해서는 용존성 성분을 제공하는 비료의 시용량을 줄여야 하며, TP부하를 저감시키기 위해서는 강우시 입자성 인의 유출을 제어해야 한다. 이를 위해서는 비가 많이 오는 여름철에 나지(裸地)나 밭에 식생이나 멀칭(mulching) 등으로 토양침식을 방지하는 대책이나 하천변에 완충역(riparian buffer zone)을 설치하는 대책이 필요하다. 저수지 관리를 효과적으로 수행하기 위해서는 저수지 내부의 탁도 거동을 정확히 예측할 수 있어야 한다. 따라서 추후 동수역학 및 열역학에 기초한 3차원 수치모형 연구와 성층흐름에 정밀한 밀도류 실험연구 및 이에 대한 적용이 필요할 것으로 판단된다.함으로써 정보의 질적보장과 정보전환의 표준화방안을 제시하는 정보분석시스템이다.이용, 수자원의 지속적 확보기술의 특성에 따른 4개의 평가기준과 26개의 평가속성으로 이루어진 2단계 기술가치평가 모형을 구축하였으며 2개의 개별기술에 대한 시범적용을 실행하였다.하는 것으로 추정되었다.면으로의 월류량을 산정하고 유입된 지표유량에 대해서 배수시스템에서의 흐름해석을 수행하였다. 그리고, 침수해석을 위해서는 2차원 침수해석을 위한 DEM기반 침수해석모형을 개발하였고, 건물의 영향을 고려할 수 있도록 구성하였다. 본 연구결과 지표류 유출 해석의 물리적 특성을 잘 반영하며, 도시지역의 복잡한 배수시스템 해석모형과 지표범람 모형을 통합한 모형 개발로 인해 더욱 정교한 도시지역에서의 홍수 범람 해석을 실시할 수 있을 것으로 판단된다. 본 모형의 개발로 침수상황의 시간별 진행과정을 분석함으로써 도시홍수에 대한 침수위험 지점 파악 및 주민대피지도 구축 등에 활용될 수 있을 것으로 판단된다. 있을 것으로 판단되었다.4일간의 기상변화가 자발성 기흉 발생에 영향을 미친다고 추론할 수 있었다. 향후 본 연구에서 추론된 기상변화와 기흉 발생과의 인과관계를 확인하고 좀 더 구체화하기 위한 연구가 필요할 것이다.게 이루어질 수 있을 것으로 기대된다.는 초과수익률이 상승하지만, 이후로는 감소하므로, 반전거래전략을 활용하는 경우 주식투자기간은 24개월이하의 중단기가 적합함을 발견하였다. 이상의 행태적 측면과 투자성과측면의 실증결과를 통하여 한국주식시장에

• The Transactions of the Korea Information Processing Society
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• v.3 no.4
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• pp.947-960
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• 1996

The primary goal for developing high performance ATM switching systems is to minimized the probability of cell loss, cell delay and deterioration of throughput. ATM switching element that is the most suitable for this purpose is the shared buffer memory switch executed by common random access memory and control logic. Since it is difficult to manufacture VLIS(Very Large Scale Integrated circuit) as the number of input ports increased, the used of switching module method the realizes 32$\times$32, 150 Mb/s switch utilizing 8$\times$8, 600Mb/s os 16$\times$16, 150Mb/s unit switch is latest ATM switching technology for small and large scale. In this paper, buffer capacity satisfying total-memory-reduction effect by buffer sharing in a shared buffer memory switch are analytically evalu ated and simulated by computer with cell loss level at traffic conditions, and also features of switching network utilizing the switching module methods in small and large-capacity ATM switching system is analized. Based on this results, the structure in outline of 32$\times$32(4.9Gb/s throughput), 150Mb/s switches under research in many countries is proposed, and eventually, switching-network structure for ATM switching system of small and large and capacity satisfying with above primary goals is suggested.