• 한국전자파학회논문지
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• 제12권5호
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• pp.787-794
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• 2001

본 논문에서는 초고주파 회로에 사용되는 GaAs FET의 대신호 모델 추출기 개발에 관하여 다루었다. 모델링을 하기에 앞서 모델링에 필요한 대량의 측정 데이터를 얻기 위하여 컴퓨터에서 자동제어가 가능한 측정프로그램을 개발하였고 측정계에서 생기는 전압강하를 막기 위해 전압 강하 보상을 위한 알고리즘을 측정프로그램에 추가하였다. 소신호 모델은 대신호 모델의 복잡도를 고려하여 7개의 내부 파라미터를 갖는 소신호 모델을 사용하였으며 각 바이어스에서의 측정된 산란계수를 소신호 모델이 예측한 산란계수 결과와 비교하여 소신호 모델의 바이어스에 따른 정확성을 검증하였다. 대신호 모델은 다양한 비선형 시뮬레이션에 유리하도록 변형된 맞춤함수 모델을 사용하였고 대신호 모델 파라미터 추출 과정에서는 일차원적 최적화 기법을 통하여 최적화된 파라미터를 추출하였다. 이러한 연구는 비선형 히로 설계 시 필요한 대신호 모델의 추출시간과 측정시간을 단축시킬 수 있고 빠른 시뮬레이션 특성으로 인해 초고주파회로로 설계용 시뮬레이터에서의 최적화과정 수행에 적합한 모델을 얻을 수 있다.

• 한국건축시공학회지
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• 제13권4호
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• pp.360-371
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• 2013

Fast delivery of construction projects provides more value to project owners. Batch production, which is production not in single pieces, but in batches, is a common approach in repetitive construction projects such as multi-unit residential building construction projects. In batch production, the use of a small batch size allows the early start of subsequent activities, and thus can lead to early completion of projects. In addition to batch size, balance between productivities in construction activities can affect project duration. However, the impact of the balance between productivities with regard to their order on project duration has not been studied. The main goal of this study is to test a hypothesis, which is that the order of construction activities' unbalanced productivities affects the amount of time reduction that can be achieved by using a small batch size. A computer-based simulation model was developed, and five different cases were simulated to test the hypothesis. The conclusion of the simulation result is that the order of productivities does not affect the time reduction achieved by using a small batch size. It is expected that the findings of this study can help general contractors make decisions in terms of batch size.

• 한국지리정보학회지
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• 제18권2호
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• pp.120-134
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• 2015

본 연구는 범죄로부터 안전한 생활환경 조성을 위해 도로망의 형태도 범죄발생에 영향을 미칠 것이라는 가정하에 공간구문론(Space Syntax)을 활용하여 사례지역을 대상으로 실증 분석하였다. 즉 도로별로 통합도, 통제도, 연결도를 공간구문론으로 계산하고, 각 도로별 실제 범죄발생 건수와 상관성을 분석하였다. 다음으로 분석결과를 일반화할 수 있는지를 확인하기 위해 멀티에이전트모형(Multi-Agent Model)을 개발하여 컴퓨터상의 가상공간에서 시나리오를 설정하고 시뮬레이션 하였다. 그 결과 도로망의 통합도가 범죄발생과 가장 연관성이 높은 것으로 분석되었으며, 가상공간 시뮬레이션 결과에도 통합도가 가장 영향을 많이 주는 것으로 나타났다. 본 연구는 멀티에이전트 시뮬레이션에서 실험공간 규모나 에이전트 행동의 프로그래밍에 한계가 있었지만 현실 데이터와 가상공간 시뮬레이션에 의해 도로망 체계와 범죄발생간의 관계를 규명하였다는데 의의가 있다. 또한 본 연구에서 개발된 시뮬레이션 플랫폼은 다양한 실험이 가능하므로 경찰력이나 방범시설의 배치 등 보다 현실적인 문제에 대한 해결방안 모색과 스마트 안전도시를 앞당기는데 기여할 것이다.

• Journal of Power Electronics
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• 제5권2호
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• pp.129-141
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• 2005

A high-performance robust hybrid speed controller for a permanent-magnet synchronous motor (PMSM) drive with an on-line trained neural-network model-following controller (NNMFC) is proposed. The robust hybrid controller is a two-degrees-of-freedom (2DOF) integral plus proportional & rate feedback (I-PD) with neural-network model-following (NNMF) speed controller (2DOF I-PD NNMFC). The robust controller combines the merits of the 2DOF I-PD controller and the NNMF controller to regulate the speed of a PMSM drive. First, a systematic mathematical procedure is derived to calculate the parameters of the synchronous d-q axes PI current controllers and the 2DOF I-PD speed controller according to the required specifications for the PMSM drive system. Then, the resulting closed loop transfer function of the PMSM drive system including the current control loop is used as the reference model. In addition to the 200F I-PD controller, a neural-network model-following controller whose weights are trained on-line is designed to realize high dynamic performance in disturbance rejection and tracking characteristics. According to the model-following error between the outputs of the reference model and the PMSM drive system, the NNMFC generates an adaptive control signal which is added to the 2DOF I-PD speed controller output to attain robust model-following characteristics under different operating conditions regardless of parameter variations and load disturbances. A computer simulation is developed to demonstrate the effectiveness of the proposed 200F I-PD NNMF controller. The results confirm that the proposed 2DOF I-PO NNMF speed controller produces rapid, robust performance and accurate response to the reference model regardless of load disturbances or PMSM parameter variations.

• KIEAE Journal
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• 제3권2호
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• pp.45-50
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• 2003

Today, there are increasing evidences that daylight is essential for health, well-being and productivity. One of the strong contributions, which atria can make to advantages in building, is in allowing the use of daylight. This research is to develop nomographs and to evaluate the daylight performances of toplit atria with louvers. For this purpose, the evaluation models of toplit atria with well indexes of 0.5, 1.0 or 2.0 have been selected through the field surveys of atrium buildings in Seoul area. Also, weather data for solar irradiance and luminous efficacy were gathered from the recently conducted previous researches. The computer simulations were performed under clear sky conditions, using the ADELINE program, and various daylight performances were analyzed by the daylight illumination ratio. Analyzing the simulation results, solar altitude, solar azimuth, and louver angle and louver reflectance were found to be important factors affecting the daylight performance of toplit atria. Using these variables, regression equations have been formulated, and the nomographs, which may predict the daylight performances of toplit atria with louvers, were developed. The developed nomographs were validated through comparing the results of nomograph predictions to the results of scale-model experiments.

• Structural Engineering and Mechanics
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• 제22권3호
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• pp.371-399
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• 2006

The theoretical background and capabilities of the developed program, SAR-CWF, for stochastic analysis of 3D reinforced-concrete shear wall-frame structures subject to seismic excitations is presented. Incremental stiffness and strength properties of system members are modeled by extended Roufaiel-Meyer hysteretic relation for bending while shear deformations for walls by Origin-Oriented hysteretic model. For the critical height of shear-walls, division to sub-elements is performed. Different yield capacities with respect to positive and negative bending, finite extensions of plastic hinges and P-${\delta}$ effects are considered while strength deterioration is controlled by accumulated hysteretic energy. Simulated strong motions are obtained from a Gaussian white-noise filtered through Kanai-Tajimi filter. Dynamic equations of motion for the system are formed according to constitutive and compatibility relations and then inserted into equivalent It$\hat{o}$-Stratonovich stochastic differential equations. A system reduction scheme based on the series expansion of eigen-modes of the undamaged structure is implemented. Time histories of seismic response statistics are obtained by utilizing the computer programs developed for different types of structures.

• 한국전자파학회논문지
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• 제11권7호
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• pp.1240-1246
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• 2000

본 논문에서는 유한차분 시간영역 방법을 적용하여 단일 계단형 마이크로스트립 기판 불연속 구조를 해석하였으며, 이 결과를 사용하여 LC 등가회로를 구성하였다. 본 논문에서 제안된 구조는 마이크로스트립 선로의 길이 방향으로 계단형 기판 불연속을 가지며, 패치 안테나의 급전선, 회로 모듈간 연결 등에 적용될 수 있다. FDTD 해석결과는 HFSS를 이용하여 얻어진 결과와 비교하여 잘 일치함을 보였다. 개발된 등가회로는 S11과 S21 모두 2.4% 이내의 정확도를 가지며, 마이크로파 회로의 CAD 설계에 응용될 수 있다.

• 대한기계학회논문집A
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• 제21권11호
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• pp.1943-1949
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• 1997

In this paper, the analysis of the shift transient characteristics for the Ravigneaux type automatic transmission has been carried out using dynamic models of the automatic trnasmission. It is necessary to understand the overall system including multi-plate clutch, band brake, one way clutch, and planetary gears. The equations of motion are derived from the dynamic models of the automatic transmission. The GUI computer simulation program has been developed to analyze the shift transient characteristics of the vehicle equipped with the Ravigneaux type automatic transmission.

• 한국기계가공학회지
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• 제14권1호
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• pp.36-43
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• 2015

Optimizing multiple design characteristics which are usually in conflict with each other in the injection molding process is frequently becoming a critical problem for designers who work in this area. The purpose of this work is to develop an automated design methodology for optimizing two such design characteristics found in injection-molded parts. A value function based on decision-making theory is used as a means of evaluating the performance of a two-characteristic design alternative. Also, a design space reduction algorithm based on Taguchi's orthogonal arrays is utilized to discover an optimal design alternative. Verification of the developed design methodology is carried out for an actual model with two design characteristics, the weld line and the gate location, to be optimized in computer simulation experiments.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 봄 학술발표회 논문집
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• pp.173-181
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• 1996

In this study, a stochastic finite element model is proposed with a view to consider the uncertainty of physical properties of rock mass in the analysis of structural behavior on underground caverns. Here, the Latin Hypercube Sampling technique, in which can makeup weak points of the Monte Carlo Simulation, is applied for the analysis of underground cavern. The validity of the newly developed computer program has been confirmed in terms of verification examples. And, the applicability of the program to the field has been tested in terms of the analysis of the underground oil storage cavern in korea.