• 한국정보통신학회논문지
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• 제10권1호
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• pp.42-48
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• 2006

본 논문에서는 차세대 복합 시분할 부호분할 다중접속 이동통신 시스템에서 타 셀 사용자 간섭 제거를 위한 결합검출 방안을 제안한다. 결합검출 기술은 차세대 복합 시분할 부호분할 다중접속 이동통신 시스템 TD-CDMA 시스템에서의 가장 큰 특징이라 할 수 있는 기술로서 셀 내의 서로 다른 사용자의 신호 간섭을 제거하여 동시에 사용자 데이터를 복원할 수 있다. 종래의 연구에서는 2단계 결합 검출 방식을 이용하여 목적 셀의 사용자 간섭 뿐 아니라 타 셀 간섭을 제거해 줄 수 있는 방안이 제안되었으나 이 방안에서는 타 셀 간섭 제거를 위한 구체적인 사용자 인식에 대한 방안이 없다. 따라서 주변 타 셀 내의 사용자의 간섭의 크기에 상관없이 모든 사용자에 대하여 결합검출을 수행해야 하며 2단계 결합검출의 복잡도가 매우 높다. 본 논문에서는 타 셀 사용자의 간섭의 크기에 따라서 선택적으로 2단계 결합 검출을 수행하는 방안을 제안한다. 제안된 방식은 모의실험을 통하여 성능을 조사하였으며 종래의 결합검출 방식에 비하여 성능의 열화가 없는 동시에 2 단계 결합검출의 복잡도를 크게 줄일 수 있다.

• 한국군사과학기술학회지
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• 제17권5호
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• pp.694-702
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• 2014

One of the most important devices in an underwater vessel is a propulsion system. It should be a quiet and efficient system for stealthy operations in the large mission area. Hence lead-acid battery system has been used to supply the energy to electric motor. Recent technological developments and improvements, such as polymer electrolyte membrane(PEM) fuel cell and lithium polymer battery and have created the potential to improve overall power and propulsion performance. An underwater vessel always starts their mission with a limited energy and is not easy to refuel. Therefore design of energy elements, such as fuel cell and battery, and their load distribution are important to increase the maximum operating time of underwater vessel. In this paper, the lead-acid battery/PEM fuel cell and lithium polymer battery/PEM fuel cell were suggested as propulsion system and their performances were analyzed by modeling and simulation using Matlab/Simulink. Each model concentrated on representing the characteristics of energy element depending on demand current. As a result the effect of load distribution between battery and fuel cell was evaluated and the operation time of each propulsion system was able to be estimated exactly.

• 한국태양에너지학회 논문집
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• 제33권2호
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• pp.35-41
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• 2013

Dye-sensitized solar cell (DSC) allows light transmission and the application of various colors that make it especially suitable for building-integrated PV (BIPV) application. In order to apply DSC module into windows, it has to be panelized: DSC module should be protected with reinforced glass to the entire surface. Up to date, it seems to be common to make double glazing with DSC modules with air gaps between the glasses and the DSC modules. Few research has been conducted on the characteristics of various glazing types with DSC modules. This study aims to analyze the electrical performance of DSC modules according to panelizing method for glazing unit with DSC modules. The prototype of the DSC glazing that applied silicone filler between DSC modules and glasses was developed. The electrical performances of this type of DSC glazing with the filler and rather conventional double glazing with DSC modules were compared. Their performances were measured using a solar simulator that is suitable for DSC performance testing. The results indicated that the electrical performance of the filler type DSC glazing improved by 7% compared to that of the conventional DSC double glazing type.

• 전기전자학회논문지
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• 제23권3호
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• pp.904-909
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• 2019

$100^{\circ}C$에 소성한 인듐 아연 산화막 (IZO)을 이온빔 처리하여, 균일할 수평 액정 배향을 구현하였다. 유리 기판 위에 코팅된 IZO 박막을 $100^{\circ}C$에 소성하고 액정 배향 기술로 이온빔을 사용하였다. 이것을 이용하여 얻어진 액정 배향의 특성을 분석하기 위해서, 편광 현미경과 결정 회전법을 사용하였다. 또한 이온빔 처리된 IZO 박막을 이용하여 만든 액정 셀이 높은 품질의 액정 소자에 충분한 열적 안정성을 가진다는 것을 확인할 수 있었다. 그리고 전계방출 주사 전자 현미경을 이용하여 이온빔의 IZO 박막의 표면에 미치는 영향을 분석하였다. 이것을 통하여 이온빔이 IZO 박막 표면의 거칠기를 변화시키고, 액정 배향에 영향을 준다는 것을 확인할 수 있었다. 마지막으로 IZO 박막으로 제작한 액정 셀의 전기-광학 특성을 측정하였다. 그리고 이것이 기존에 사용되는 러빙법 처리된 폴리이미드 박막으로 제작한 액정 셀보다 뛰어난 특성을 가진다는 것을 확인하였다. 또한 액정 고정 에너지를 측정하여 이것이 균일한 액정 배향을 구현하기 위한 적합한 특성을 가진다는 것을 확인하였다.

• 한국정보통신학회논문지
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• 제10권1호
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• pp.88-95
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• 2006

PID 제어기는 구조가 간단하고 적용이 용이하다는 장점으로 인하여 널리 사용되고 있는 제어방식이다. 이러한 선형 PID 제어기는 시스템의 파라메터가 변화가 있거나 부하 특성이 비 선형적으로 변화할 때에 적절한 이득과 성능을 얻기 어려워 고성능 제어 특성을 기대하기 어렵다. 본 연구에서는 세포성 면역 반응과 경사감소학습에 기초하여 비선형 PID 제어기를 설계하고, 설계된 제어기의이득과 비선형 함수의 파라메터들을 실시간 적응적으로 학습할 수 있는 학습 알고리즘을 개발하고, 이를 제어시스템에 적용하였다. 제안된 비선형 PID 제어기는 비선형 직류 모터 시스템의 파라메터들이 변화하거나 주파수가 다른 추종 명령에 대하여, 적응적으로 이득을 변화 시키며 추종함을 보였다.

• Industrial Engineering and Management Systems
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• 제7권2호
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• pp.160-170
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• 2008

This paper proposes a mathematical model for converting conveyor assembly line to cellular manufacturing in complex production environments. Complex production environments refer to the situations with multi-products, variant demand, different batch sizes and the worker abilities varying with work stations and products respectively. The model proposed in this paper aims to determine (1) how many cells should be formatted; (2) how many workers should be assigned in each cell; (3) and how many workers should be rested in shortened conveyor line when a conveyor assembly line should be converted, in order to optimize system performances which are defined as the total throughput time and total labor power. We refer the model to a new production system. Such model can be used as an evaluation tool in the cases of (i) when a company wants to change its production system (usually a belt conveyor line) to a new one (including cell manufacturing); (ii) when a company wants to evaluate the performance of its converted system. Simulation experiments based on the data collected from the previous documents are used to estimate the marginal impact that each factor change has had on the estimated performance improvement resulting from the conversion.

• Journal of Information Display
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• 제12권3호
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• pp.115-119
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• 2011

Optically isotropic liquid crystal (LC) mixture such as blue-phase LC and nanostructured LC composites exhibit the advantages of fast response time, high contrast ratio and wide-viewing angle due to the induced birefringence along the horizontal electric field. Utilizing this mixture, a novel single cell gap in-plane switching-type polymer-stabilized blue-phase transflective liquid crystal display by embedding the nanowire grid polarizer as a polarization-dependent reflective polarizer in the R region is proposed. This device can be used as a normal black mode without any quarter-wave plate or patterned in-cell phase retarder. Moreover, the transmittance is identical to the reflectance so that it will be suitable for single gamma driving. Detailed electro-optic performances, such as voltage-dependent light efficiency and viewing angle of the proposed device configuration, are investigated.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.95.2-95.2
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• 2011

In order to achieve high performance and low cost for commercial applications, the development of membrane electrode assemblies (MEA), in which the electrochemical reactions actually occur, must be optimized. Expensive platinum is currently used as an electrochemical catalyst due to its high activity. Although various platinum alloys and non-platinum catalysts are under development, their stabilities and catalytic activities, especially in terms of the oxygen reduction (ORR), render them currently unsuitable for practical use. Therefore, it is important to decrease platinum loading by optimizing the catalysts and electrode microstructure. In this study, we prepared several different MEAs (non-uniform Nafion$^{(R)}$ ionomer loading electrode) which have dual catalyst layers to find the optimal Nafion$^{(R)}$ ionomer distribution in the electrodes. We changed Nafion$^{(R)}$ ionomer content in the layers to find the ideal composition of the binder and Pt/C in the electrode. For MEAs with various ionomer contents in the anodes and cathodes, the electrochemical activity (activation overpotential) and the mass transport properties (concentration overpotential) were analyzed and correlated with the single cell performance. The dual catalyst layers MEA showed higher cell performance than uniformly fabricated MEA, especially at the high current density region.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.153-156
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• 2007

This paper presents the design, development and performance of a power conditioning system (PCS) for application to a 250kW Molten Carbonate Fuel Cell (MCFC) generation system. A DSP controller was used to control the dc-dc and dc-ac converter operation for grid connection and power injection to the grid. The controller must also supervise the total PCS operation while communicating with the fuel cell system controller. A control method for parallel operation of dc-dc converters was proposed and verified. A 250kW prototype was successfully built and tested. Experimental performances are compared to minimum target requirements of the PCS for MCFC.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.413-416
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• 2006

PtRu catalyst is most widely used as anode catalyst for a direct methanol fuel cell(DMFC). To promote the efficiency of the catalysts, it Is important to increase the triple phase boundary. In this study, we have tried to increase the triple phase boundaries in preparing electrocatalysts of the fuel cells, based on the process of grafting a proton-conducting agent onto the catalyst This grafted proton-conducting agent can act as an ionomer like Nafion, currently widely used ionomer. First, we have prepared the 80wt% PtRu/Ketjen Black electrocatalyst by an improved colloidal method. And, we have grafted methylsulfonate groups $(-CH_2SO_3H)$ into the catalyst as proton-conducting agents. As results of cyclic voltammety and single cell test of the membrane electrode assembly (MEA), we can conclude that the activity of the grafted electrocatalysts is superior to that of conventional ones, in performance of DMFCs. For our further study, we will investigate the optimum ratio of catalyst/grafted proton conduct Ing agent with maximum performance of a DMFC.