• Journal of the Korean Statistical Society
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• 제21권1호
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• pp.1-13
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• 1992

This article deals with variable selection problem under a newly formed predictive heteroscedastic discriminant rule that accounts for mulitple homogeneous covariance matrices across the K multivariate normal populations. A general version of predictive discriminant rule, a variable selection criterion, and a criterion for stopping with further selection are suggested. In a simulation study the practical utilities of those considered are demonstrated.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.936-941
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• 2004

An Optimal Feedforward Integral Variable Structure or FIVSC approach for an electrohydraulic position servo control system is presented in this paper. The FIVSC algorithm combines feedforward strategy and integral in the conventional Variable Structure Control (VSC) and calculating the control function to guarantee the existence of a sliding mode. Furthermore, the chattering in the control signal is suppressed by replacing the sign function in the control function with a smoothing function. The simulation results illustrate that the purposed approach gives a significant improvement on the tracking performances when compared with some existing control methods, like the IVSC and MIVSC strategies. Simulation results illustrate that the purposed approach can achieve a zero steady state error for ramp input and has an optimal motion with respect to a quadratic performance index. Moreover, Its can achieve accurate servo tracking in the presence of plant parameter variation and external load disturbances.

• 전자공학회논문지B
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• 제30B권12호
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• pp.73-86
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• 1993

This paper proposes an automatic variable block truncation coding (BTC) method. It selects the block size automatically based on the mode of the discontinutiy measure of blocks. The combination of an automatic block-size determination scheme and the conventional BTC results in the proposed automatic variable BTC techniques. For color images, subsampling in I and Q chrominance components is adopted along with the variable BTC. To show the effectiveness of the proposed algorithm, its simulation results are compared to those of the several conventional BTC algorithms for monochrome and color test images. Computer simulation shows that the proposed algorithm gives better performance than the conventional ones based on the subjective and objective performance evaluation.

• 한국정밀공학회지
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• 제20권9호
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• pp.100-108
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• 2003

This paper proposes a flywheel hybrid vehicle to solve the energy crisis problem by the exhaustion of a fossil fuel and air pollution for the conservation of environment. The proposed flywheel hybrid vehicle is composed of an accumulator and a flywheel as the energy generation and storage component and three variable displacement hydraulic pump/motors as the energy transfer devices. Flywheel has the characteristics of high energy density and easy energy absorption and consumption. The effectiveness of the energy-saving of the proposed flywheel hybrid vehicle is verified by simulation using Matlab/simulink. First of ail, analytical modeling for the flywheel hybrid vehicle is presented and simulations are performed based on the experimental efficiency data of a variable displacement pump/motor. The results of the simulation show that the effect of energy savings is realized by the proposed hybrid vehicle in 3 different city driving patterns.

• 산업경영시스템학회지
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• 제17권32호
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• pp.155-162
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• 1994

The Japanese "Just-In-Time" technique reduces inventory and unnecessary factors. This technique makes the success of Japanese firms, therefore many Korean firms try to apply it to their situation. But the technique doesn't bare the same success in Korean firms. This paper, therefore, considers the different situations between Korean rim and Japanese firm, then simulates the Pull system and Push system for a multiline, multistage production system. This paper drives the different results of simulation according to variable processing times, variable demand, set-up time and shortages in Pull system and Push system using GPSS. The results show that the performance of Pull system is lower than Push system's in variable master production scheduling and variable processing times.ing times.

• 전기학회논문지
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• 제62권12호
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• pp.1750-1754
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• 2013

A variable bit rate speech coder is presented. The coder is based on the observation that a speech signal can be viewed as a combination of piecewise linear signals in a short time period. The encoder detects the sample points where the slope of the signal changes, which are called the inflection points in this paper. The coder transmits the location and value for the detected inflection sample, but only the location information for the noninflection samples. In the decoder, the noninflection samples are estimated with interpolation of the received information. Several factors affecting the performance of the coder have been tested through simulation. Simulation results show that the linear interpolation produces 1 ~ 5 dB improvement over the cubic spline interpolation. And the -law companding does not provide any benefit when it is applied before the inflection detection. With low threshold values in the inflection point detection, the coder shows better MOS and more than 16 dB improvement in SNR compared to the continuously variable slope delta modulation (CVSDM).

• Communications for Statistical Applications and Methods
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• 제24권6호
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• pp.651-662
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• 2017

We propose an alternative procedure to select penalty parameter in $L_1$ penalized robust regression. This procedure is based on marginalization of prior distribution over the penalty parameter. Thus, resulting objective function does not include the penalty parameter due to marginalizing it out. In addition, its estimating algorithm automatically chooses a penalty parameter using the previous estimate of regression coefficients. The proposed approach bypasses cross validation as well as saves computing time. Variable-wise penalization also performs best in prediction and variable selection perspectives. Numerical studies using simulation data demonstrate the performance of our proposals. The proposed methods are applied to Boston housing data. Through simulation study and real data application we demonstrate that our proposals are competitive to or much better than cross-validation in prediction, variable selection, and computing time perspectives.

• 제어로봇시스템학회논문지
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• 제21권11호
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• pp.1027-1033
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• 2015

For the attitude control of spacecraft, two variable-speed control moment gyros are proposed as main actuators in the article. Since a variable-speed control moment gyro (VSCMG) makes two control torques (gyroscopic torque and reaction torque), two VSCMGs are sufficient for controlling 3-axes attitude. Additionally, there are no singular conditions for two non-parallel VSCMGs. Since gyroscopic torque is usually much greater than reaction torque, the control performances of approximately 3 axes may not be the same. However, several missions can be accomplished by controlling two axes. For such missions, a selective axes control method is proposed. The method selects two axes for a certain task and controls the attitude of the selected axes. For the remaining axis, angular speed is controlled for stabilization. A hardware-in-the-loop simulation has been used to test VSCMG modules and to verify the proposed method. Two VSCMGs can be alternative actuators for small satellites.

• 디지털융복합연구
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• 제11권2호
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• pp.175-182
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• 2013

본 연구에서는 주택 수요와 공급의 상호영향관계 메커니즘을 이용하여 가격 시뮬레이션 모형을 개발하였다. 가격 시뮬레이션 모형의 핵심 알고리즘은 피드백 제어 이론을 이용한 시스템 다이나믹스 기반의 스톡 플로우 변수이며, 이러한 원리를 이용하여 서울지역 아파트 가격변화 행태를 모델링하였다. 가격 행태를 결정하는 피드백 메커니즘은 중장기 경기변동 시나리오 하에 대출 이자율을 정책변수로 아파트 매매 수요자와 공급자 규모를 스톡 변수로 설정하고, 이들 간의 상호 영향관계를 검증하였다. 본 논문을 통하여 향후 아파트 가격 추이는 아파트 매매 수요자와 공급자 규모의 행태 변화와 수요자와 공급자가 갖는 가격에 대한 반응 매개변수간의 영향관계로 구성된다. 또한 향후 경기 전망 및 대출이자율 등 거시경제의 상황에 따라 아파트 매매가격은 변화함을 알 수 있었다. 제시된 아파트 매매 가격 시뮬레이션 계량모델은 양도세 및 취득세 감면 등 비 금융 관련 부동산정책변수와 대출이자 조정 등 금융 관련 정책변수의 보다 정확하고 충분한 데이터를 적용하면 실무 적용과 정부 주택정책입안에 활용 할 수 있을 것으로 판단된다.

• 한국시뮬레이션학회논문지
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• 제26권4호
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• pp.1-9
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• 2017

유전 알고리즘은 생물 유전학에 기본 이론을 두는 전역 탐색 알고리즘으로, 산업, 뉴럴 네트워크, 웹, 그리고 국방 등의 분야에서 활발히 사용되고 있다. 하지만 기존의 유전 알고리즘은 염색체의 개수가 고정되어 있는 형태여서 시뮬레이션 도중 초기에 주어진 상황보다 더 복잡한 상황이 주어질 수 있는 경우에는 적용이 힘들다는 한계점이 존재한다. 본 연구에서는 이를 극복하기 위해서 염색체 비분리를 적용한 가변 염색체 유전 알고리즘을 제안하였다. 그리고 염색체 수의 변화가 시뮬레이션 결과에 영향을 미치는 것을 확인하기 위하여 대 잠수함 HVU 호위 임무 시뮬레이션에 염색체 비분리를 적용한 가변 염색체 유전 알고리즘을 적용하였다. 시뮬레이션 결과 기존의 유전 알고리즘과는 달리 가변 염색체 유전 알고리즘에서는 더 복잡한 전술이 더 일찍 등장하였으며, 그에 따라 염색체 수가 증가하는 방향으로 진화가 일어나는 것을 확인할 수 있었다.