• 제어로봇시스템학회논문지
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• 제8권6호
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• pp.439-444
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• 2002

In this paper, a new model reduction method is proposed to obtain a reduced order model in the frequency domain. The method is developed based on the second-order plus dead time modeling technique. The initial value of the reduced model parameters can be obtained using this method coinciding four point(0, -$\pi$/2, -$\pi$, -3$\pi$/2) on the Nyquist curve. The optimal parameters of the reduced model is obtained through calculation procedure with three steps. It is shown that Nyquist curves and unit step responses of the reduced models of numerical examples closely agree with those of original models.

• Smart Structures and Systems
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• 제18권1호
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• pp.1-16
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• 2016

Model Order Reduction (MOR) denotes the theory by which one tries to catch a model of order lower than that of the real model. This is conveniently pursued in view of the design of an efficient structural control scheme, just passive within this paper. When the nonlinear response of the reference structural system affects the nature of the reduced model, making it dependent on the visited subset of the input-output space, standard MOR techniques do not apply. The mathematical theory offers some specific alternatives, which however involve a degree of sophistication unjustified in the presence of a few localized nonlinearities. This paper suggests applying standard MOR to the linear parts of the structural system, the interface remaining the original unreduced nonlinear components. A case study focused on the effects of a helicopter land crash is used to exemplify the proposal.

• 제어로봇시스템학회논문지
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• 제10권12호
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• pp.1148-1154
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• 2004

The goal of this paper is to verity that the gradual reduction of drug dose (GRDD), which has already been shown by authors to be effective for a simplified HIV infection model, still works for a more realistic model. While the simplified HIV infection model does not take into account an helper-independent CTL, the five state nonlinear model proposed by Wodarz describes the dynamics of both helper-dependent and helper-independent CTL in HIV infection. In this paper, it is shown that, by applying GRDD to Wodarz's five state HIV infection model, the state of HIV infected patient converges to that of non-progressor whose immune response is excited so that his symptom would not be developed into AIDS. Roughly speaking, GRDD is 'slow reduction of dose after the maximum dose for a certain period.' It turns out that an equilibrium representing non-progressor is locally asymptotically stable for the most values of drug dosage, which is required to hold in order to apply GRDD. Simulation results establish that GRDD is still considerably effective both for an AIDS patient and a patient who has been on HAART for a long time.

• Wind and Structures
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• 제22권1호
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• pp.17-41
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• 2016

To address the uncertainty of the flight trajectories caused by the turbulence and gustiness of the wind field over the roof and in the wake of a building, a 3-D probabilistic trajectory model of flat-type wind-borne debris is developed in this study. The core of this methodology is a 6 degree-of-freedom deterministic model, derived from the governing equations of motion of the debris, and a Monte Carlo simulation engine used to account for the uncertainty resulting from vertical and lateral gust wind velocity components. The influence of several parameters, including initial wind speed, time step, gust sampling frequency, number of Monte Carlo simulations, and the extreme gust factor, on the accuracy of the proposed model is examined. For the purpose of validation and calibration, the simulated results from the 3-D probabilistic trajectory model are compared against the available wind tunnel test data. Results show that the maximum relative error between the simulated and wind tunnel test results of the average longitudinal position is about 20%, implying that the probabilistic model provides a reliable and effective means to predict the 3-D flight of the plate-type wind-borne debris.

• 농업과학연구
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• 제48권4호
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• pp.911-926
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• 2021

We devised a grape variety model to estimate the impact of lowering the Shine Muscat quality level on the grape market. Shine Muscat has become a popular grape variety in Korea. Accordingly, the area devoted to the harvesting of Shine Muscat has increased dramatically since 2016. Our study examines how a reduction in the quality of Shine Muscat affects other grapes such as Campbell Early, giant peak, and Muscat Bailey A (MBA). The Armington model was used to impose consumer preferences and product differentiation assumptions. We found that a decrease in the consumer preference for Shine Muscat realized by lowering the quality of Shine Muscat largely reduces the price of this variety. Also, the prices of other grape varieties fell via a substitute effect. Moreover, if grape varieties were more differentiated, the reduction in the price of Shine Muscat would be greater, while the decreases in the prices of other grape varieties would be smaller. These results imply that farmers of Shine Muscat must continue with quality management efforts to avoid the negative effect of changing consumer behavior with regard to Shine Muscat against a reduction in its quality. Our model introduces a product differentiation model for the fruit market and helps policymakers and farmers understand the impact of changing market conditions in the fruit market.

• 한국전자거래학회지
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• 제15권3호
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• pp.163-181
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• 2010

최근 온난화 현상에 따른 범세계적 위기가 초래됨에 따라 선진국을 중심으로 교토의정서가 체결되었으며, 이를 계기로 온실가스 규제가 본격화되기 시작하였다. 또한 교토의정서의 교토유연성체계라는 시장메커니즘이 도입되어 온실가스 배출에 대한 소유권이 설정되고, 수급에 따라 배출권 가격이 형성되는 등 새로운 무형의 자원을 거래하는 탄소시장이 등장하게 되었다. 학계에서는 탄소배출효과를 측정하는 방법론과 이를 탄소배출권의 경제적 비용으로 전환하고자 하는 연구들이 태동하기 시작하였다. 본 연구에서는 전자정부 정보화사업 중 하나인 G2B 시스템을 통해 전통적인 조달업무 프로세스가 온라인화 됨에 따라 저감되는 탄소 배출저감효과 즉, e-transformation화에 따른 탄소저감효과를 측정하는 ECRE(Evaluation of $CO_2$ Reduction in E-transformation)모델과 절차를 제시하고자 한다. ECRE 모델은 세계 기후협의체(IPCC)의 방법론을 근간으로 하여 크게 '이동 수단에 따른 탄소저감효과', '종이 문서 절감에 따른 탄소저감효과' 2가지의 탄소배출량을 측정하고 이를 탄소배출권의 경제적 비용으로 환산한다. 또한 본 연구에서는 탄소저감효과를 효과적으로 측정하기 위하여 5단계와 10개의 세부절차로 구성된 절차를 제시하였다. 본 연구에서 제시한 ECRE 모델과 절차를 이용하여 정부기관은 물론 온실가스 규제를 받게 되는 에너지 환경기업 등에서 정보화사업을 통한 탄소감축 실적의 추정 및 추가적인 정보화사업 추진으로 기대되는 탄소저감효과를 사전에 시뮬레이션해 볼 수 있는 도구로서 활용이 기대된다.

• Nutrition Research and Practice
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• 제5권4호
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• pp.337-348
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• 2011

Weight reduction behavior is common among adolescent girls. The present study examined the status of weight reduction behavior and factors affecting the behavioral intention of weight reduction using the Health Belief Model (HBM) for female middle school students by weight category. Survey data was collected from three girl's middle schools in Gyeongju, Korea. A total of 299 female middle school students participated in this study. The questionnaire had questions about general characteristics, weight reduction behavior, and variables of HBM (perceived threat, perceived benefits, perceived barriers, cues to action, self-efficacy in dietary life and exercise, and behavioral intention of weight reduction). Descriptive statistics, Chi-square tests, ANOVA, and multiple regression analysis were applied to analyze the variables. A higher percentage of students in the overweight group attempted weight reduction than those in the underweight and the normal weight groups (P < 0.001). Among students who had attempted weight reduction, 73% tried diet therapy, while 78% tried exercise. Students in the normal and overweight groups showed significantly higher threat (P < 0.01) and cues to action (P < 0.001) than those in the underweight group. As for perceived benefits, barriers, and self-efficacy in dietary life and exercise, there were no significant differences among weight groups. Students in the overweight group showed the strongest intention of weight reduction and there were significant differences among the three weight groups (P < 0.001). Perceive threat (P < 0.01), cues to action (P < 0.001), and perceived self-efficacy (P < 0.01) were significantly associated to behavioral intention of weight reduction for all respondents. For the underweight group, perceived threat (P < 0.05) and perceived self-efficacy (P < 0.01) were the significant variables. For the overweight group, cue to action was the significant variable (P < 0.05).

• 대한산업공학회지
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• 제36권1호
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• pp.69-77
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• 2010

The failure rate model of External Environment Maintenance(EEM) for a system under severe environment is investigated. EEM, which is recently introduced concept, is a maintenance activity controlling external environment factors that potentially cause system failure such as cleaning equipment, controlling temperature (humidity) and removing dust inside of electronic appliances. EEM can not have any influence on the inherent failure rate of a system but reduce the severity of the external environment causing failure since it deals with only external environment factors. Therefore, we propose two failure rate models to express the improvement effect of EEM: The intensity reduction model and age reduction model. The intensity and age reduction models of EEM are developed assuming the quality of improvement effect is proportioned to an extra intensity or age respectively. The validation of proposed failure rate models is performed in order of data generation, parameter estimation and test for goodness-of-fit.

• Wind and Structures
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• 제4권6호
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• pp.505-518
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• 2001

Shantou Bay Bridge is the first long-span suspension bridge in China. Because of its location near the Shantou Seaport and its exposure to high typhoon winds, wind-resistant studies are necessary to be made. In this paper, critical flutter wind speeds and buffeting responses of this bridge at its operation and main construction stages are investigated. The Buffeting Response Spectrum method is first briefly presented. Then the sectional model test is carried out to directly obtain the critical flutter wind speed and to identify the flutter derivatives, which are adopted for the later analysis of the buffeting responses using the Buffeting Response Spectrum method. Finally the aeroelastic full bridge model is tested to further investigate the dynamic effects of the bridge. The results from the tests and the computations indicate that the flutter and buffeting behaviors of the Shantou Bay Bridge are satisfied.

• 한국위성정보통신학회논문지
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• 제6권2호
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• pp.46-50
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• 2011

인공위성에 대한 구조해석을 수행하기 위해서는 인공위성의 모든 기계적 특성이 반영된 유한요소모델을 필요로 한다. 인공위성의 개발특성상 여러 부품들은 서로 다른 회사에서 제작이 되며, 해당 유한요소모델의 제공이 불가능한 경우가 종종 발생하게 된다. 이러한 경우에 초요소 기법을 이용하면 쉽게 해결할 수 있다. 현재 개발중인 위성의 경우, 안테나 업체에서 안테나 기동시 발생하는 미소진동의 양을 계산하고자 인공위성 전체의 유한요소모델을 필요로 하였다. 이 때, 초요소 기법을 이용하여 축약된 모델을 제공할 수 있었다. 초요소기법은 Craig-Bampton 방법을 이용하여 유한요소모델을 동적축약하는 기법이며 본 논문에서는 인공위성 유한요소모델에 이를 적용하였다. 동적축약이 잘 이루어졌는지를 확인하기 위하여 전체 유한요소모델과, 축약모델의 모드해석 결과와 주파수 응답해석 결과를 비교하였으며, 두 결과가 매우 잘 맞는다는 것을 확인할 수 있었다. 이로부터 본 해석 방법의 유용성을 확인할 수 있었다.