• 대한조선학회논문집
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• 제41권1호
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• pp.15-22
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• 2004

Twin-skeg type stern shapes are recently adopted for very large commercial ships. However it is difficult to apply a CFD system to a hull form having twin-skeg, since grid topology around a twin-skeg type stern is more complicated than that of a conventional single-screw ship, or of an open-shaft type twin-screw ship with center-skeg. In the present study a surface mesh generator and a multi-block field grid generation program have been developed for twin-skeg type stern. Furthermore, multi-block flow solvers are utilized for potential and viscous flow analysis around a twin-skeg type stern The present computational system is applied to a 15,000TEU container ship with twin-skeg to prove the applicability. Wave profiles and wake distribution are calculated using the developed flow analysis tools and the results are compared with towing tank measurements.

• 전기학회논문지P
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• 제64권1호
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• pp.41-44
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• 2015

In cognitive radios, exponentially distributed idle period(EIP) is considered in this paper. In the EIP case, durations of idle periods are be limited and varied by primary traffic arrivals. Accordingly, we first analyze the idle period utilization which can be achieved by the slotted ALOHA in cognitive radio communications. The idle period utilization is a newly defined performance metric to measure the transmission performance of the secondary network as effective time durations utilized for successful secondary transmissions in an idle period. Then, the idle period utilization is maximized through controlling the data transmission time. All technical processes are mathematically analyzed and expressed as closed form solutions.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.1383-1385
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• 2009

This paper suggests that testing method and equipment structure to detect potential failures of LCD cells. LCD Cell Aging Tester is the unique process to detect failures related with ASG circuits. This system consists of four components that is Aging chamber, work table, probe contact unit, and pattern generator. The key factor of the concept is temperature aging and HVS driving. Complicated combination of test parameters including voltage, temperature and frequency provided practical burn-in conditions eligible for prediction of mass production.

• International Journal of Air-Conditioning and Refrigeration
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• 제10권4호
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• pp.177-183
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• 2002

A pulsed tracer gas technique is applied to measure the distributions of local mean age and local mean residual-life-time of air in a half-scale experimental chamber, The airflow patterns in the chamber are visualized by a Helium bubble generator for three different exhaust locations. A supply slot is located at the top of a right wall, and an exhaust slot is at either bottom-left (Case 1), bottom-right (Case 2), or top-left (Case 3) location. Results show that the distributions of local mean age and local mean residual-life-time are different from each other, but both of them are closely related to the airflow pattern in the space. Included are discussions on explaining the variations of overall room ventilation effectiveness depending upon airflow rates for three different supply-exhaust configurations.

• 대한전자공학회논문지SD
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• 제38권4호
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• pp.50-50
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• 2001

IDDQ 테스트는 CMOS VLSI 회로에서 발생 가능한 여러 종류의 물리적 결함을 효율적으로 검출 할 수 있는 테스트 방식이다. 본 논문에서는 CMOS에서 발생 빈도가 가장 높은 합선고장을 효과적으로 검출할 수 있는 IDDQ 테스트 알고리즘을 이용하여 패턴 생성기를 개발하였다. 고려한 합선고장 모델은 회로의 레이아웃 정보에 의존하지 않으며, 내부노드 혹은 외부노드에 한정시킨 합선고장이 아닌 테스트 대상회로의 모든 노드에서 발생 가능한 단락이다. 구현된 테스트 패턴 생성기는 O(n2)의 복잡도를 갖는 합선고장과 전압 테스트 방식에 비해 상대적으로 느린 IDDQ 테스트를 위해서 새롭게 제안한 이웃 조사 알고리즘과 고장 collapsing 알고리즘을 이용하여, 빠른 고장 시뮬레이션 시간과 높은 고장 검출율을 유지하면서 적은 수의 테스트 패턴 생성이 가능하다. ISCAS 벤치마크 회로의 모의실험을 통하여 기존의 다른 방식보다 우수한 성능을 보였다.

• Journal of Electrical Engineering and Technology
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• 제3권2호
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• pp.263-270
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• 2008

We studied partial discharge detection by sensing electromagnetic waves emitted from the partial discharge source in an HV Rotating Machine using a UWB sensor. In this study, we design a new type of compact low frequency UWB sensor based on micro-strip technology. We also perform many experiments of offline and dismantled testing compared with the existing HFCT on stator winding of the HV generator. We mention the detailed design of a new compact UWB sensor along with the time domain PRPD pattern and frequency domain results of partial discharge in the stator winding of a 6.6kV rotating machine by offline testing performed in a laboratory.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2006년도 춘계학술대회 논문집
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• pp.407-409
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• 2006

This paper presents the methods of designing the control circuits for a Class D amplifier to have a peak performance. The proposed approach is based on the three functional components - a carrier generator, a feedback circuit and a dead-time circuit. First the analog signal is applied to the controller, which outputs the 3 level PWM waveform. The controller used for this experiment is made of the operational amplifier and the logic circuit. The experimental results show that the control circuit performs with satisfaction and its output is proportional to input audio signal, providing a satisfactory 3 level PWM pattern. From this design methodology, by implementing a proposed control circuit we can achieve the efficient Class D amplifier using the half-bridge, full-bridge or push-pull topology at the output stage.

• 전기학회논문지
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• 제60권4호
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• pp.796-800
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• 2011

As the increasing integrity of VLSI, the BIST(Built-In Self Test) is used as an effective method to test chips. Generally the pseudo-random test pattern generation is used for BIST. But it requires too many test patterns when there exist random resistant faults. Therefore we propose a mixed test scheme which applies to the circuit under test, a deterministic test sequence followed by a pseudo-random one. This scheme allows the maximum fault coverage detection to be achieved, furthermore the silicon area overhead of the mixed hardware generator can be reduced.

• 전기학회논문지
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• 제57권4호
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• pp.617-624
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• 2008

This paper proposes design and implementation of wind turbine simulators which incorporate the turbine dynamic characteristics. At first, the turbine output characteristic in steady state is modelled as a function of wind speed and then dynamic characteristics are modelled such as pitch angle control, torsional vibration, tower shadow effect, wind shear effect, and inertia effect. In addition, a wind speed simulator is developed which can generate the real wind speed pattern. The wind turbine simulator is implemented with 3[kW] M-G set(cage-type induction motor coupled with doubly-fed induction generator) at laboratory.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1789-1790
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• 2007

이 논문에서 우리는 생체모방 시스템을 구현하기 위해 일반적인 기계 시스템과 인간의 신경 진동자 모델을 결합하였다. 이러한 시스템은 외부환경의 변화에 따른 효과적인 자율 적응 운동 형태를 생성할 수 있다. 인간 및 동물의 주기적 자율 운동을 관장하는 Central Pattern Generator (CPG)는 신경 진동자 네트웍에 의해서 표현가능하고 이는 신경 진동자 모델 내부의 sensory 피드백 신호를 통해, 주기성을 같은 외란에 상호 작용하여 적절한 운동을 생성해 낸다. 따라서 이를 기계 시스템에 결합하면 이러한 시스템은 변화되는 환경이나 잘 알지 못하는 외란에 대하여 자율적으로 적응된 운동을 보일 수 있다. 이를 위해 본 논문은 이러한 신경 진동자 모델과 결합된 realtime 시스템을 구현하고 그 자율 적응 운동의 생성 가능성을 살펴본다.