• 한국해양공학회지
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• 제17권6호
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• pp.38-46
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• 2003

Aim of this article is to propose Micro-Genetic Simulated Annealing (${\mu}GSA$) as a hybrid metaheuristics approach to find the global optimum of nonlinear optimisation problems. This approach combines the features of modern metaheuristics such as micro-genetic algorithm (${\mu}GAs$) and simulated annealing (SA) with the general robustness of parallel exploration and asymptotic convergence, respectively. Therefore, ${\mu}GSA$ approach can help in avoiding the premature convergence and can search for better global solution, because of its wide spread applicability, global perspective and inherent parallelism. For the superior performance of the ${\mu}GSA$, the five well-know benchmark test functions that were tested and compared with the two global optimisation approaches: scatter search (SS) and hybrid scatter genetic tabu (HSGT) approach. A practical application to structural sandwich panel is also examined by optimism the weight function. From the simulation results, it has been concluded that the proposed ${\mu}GSA$ approach is an effective optimisation tool for soloing continuous nonlinear global optimisation problems in suitable computational time frame.

• International Journal of Aeronautical and Space Sciences
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• 제13권1호
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• pp.43-57
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• 2012

In a modern aircraft, there are many variations in its mass, stiffness, and aerodynamic characteristics. Recently, an analytical approach was proposed, and this approach uses the idea of uncertainty to find out the most critical flight flutter boundary due to the variations in such aerodynamic characteristics. An analytical method that has been suggested to predict robust stability is the mu method. We previously analyzed the robust flutter boundary by using the mu method, and in that study, aerodynamic variations in the Mach number, atmospheric density, and flight speed were taken into consideration. The authors' previous attempt and the results are currently quoted as varying Mach number mu analysis. In the author's previous method, when the initial flight conditions were located far from the nominal flutter boundary, conservative predictions were obtained. However, relationships among those aerodynamic parameters were not applied. Thus, the varying Mach number mu analysis results required validation. Using an optimization approach, the varying Mach number mu analysis was found out to be capable of capturing a reasonable robust flutter boundary, i.e., with a low percentage difference from boundaries that were obtained by optimization. Regarding the optimization approach, a discrete nominal flutter boundary is to be obtained in advance, and based on that boundary, an interpolated function was established. Thus, the optimization approach required more computational effort for a larger number of uncertainty variables. And, this produced results similar to those from the mu method which had lower computational complexity. Thus, during the estimation of robust aeroelastic stability, the mu method was regarded as more efficient than the optimization method was. The mu method predicts reasonable results when an initial condition is located near the nominal flutter boundary, but it does not consider the relationships that are among the aerodynamic parameters, and its predictions are not very accurate when the initial condition is located far from the nominal flutter boundary. In order to provide predictions that are more accurate, the relationships among the uncertainties should also be included in the mu method.

• 제어로봇시스템학회논문지
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• 제6권2호
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• pp.217-227
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• 2000

Although inverter-driven hydraulic elevators(HEL's) have advantages over traditional valve-controlled HEL's energy efficiency and performance they need robustness in performance and stability to accomodate nonlinearities big parametric variations and resonances in mechanical-hydraulic inner system. In this paper a robust controller based on DGKF/$\mu$ mixed approach is applied to a HEL system with carring capacity of 24 persons for Incheon International Airport. The results of a test tower(T/T) has shown good ro-bustness in performance and stability of the proposed controller thereby proving a feasibility of this robust controller-based approach for other HEL problems.

• 한국결정성장학회지
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• 제13권6호
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• pp.304-308
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• 2003

분리기 내 압력 조절을 통하여 압력 변화가 세라믹 입자 $Al_2O_3$, $Fe_2O_3$ 분급에 미치는 영향을 수치 해석적으로 분석하였다. 입자 분급 해석을 위해 3차원 Lagrangian approach를 이용하였으며, 이를 통해 입자의 분리기 내 거동 경로를 추적하여 각 압력에 따른 분리 가능한 최소 입자 크기(cut-diameter)와 분리율(separation rate)를 계산하였다. 압력 감소는 입자를 운반하는 아르곤 가스의 밀도를 감소시키면서, 분리기 내부 압력 손실을 줄이는 원인이 되었다. 이로 인해 상압에서 분리기 압력이 저압 상태로 변함에 따라, 더 미세한(수 $\mu\textrm{m}$) 입자가 분리 가능함이 예측되었다. 특히 50 torr의 저압 하에서 계산된 세라믹 입자의 분급 양상을 분석하면,$Al_2O_3$ 입자는 4 $\mu\textrm{m}$, $Fe_2O_3$경우는 3$\mu\textrm{m}$ 크기의 입자 분리가 가능하였다.

• 제어로봇시스템학회논문지
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• 제2권1호
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• pp.35-44
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• 1996

A design method for a teleoperator robot system is presented in this paper. The control system consists of two phases; approach phase and contact one. The end-effector position of the estimated slave robot and the contact force between the end-effector and wall are displayed on the monitors at control site, using which the operator controls the teleoperator system. The approach phase controller is designed using Smith's principle and the contact one designed based upon the structured singular value ${\mu}$ in order to increase the robustness of the system. The uncertainatices such as communication time delay and the variations of system parameters are considered as a muliplicative pertubation. Computer simulations are conducted in order to evaluate the performance of the proposed design method. It is found that desirable control performance, especially in the contact phase, is obtained if the control mode is switched into contact phase when the estimated position of the slave robot end-effector is in front of the wall.

• 제어로봇시스템학회논문지
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• 제5권6호
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• pp.667-675
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• 1999

In this paper, we propose a robust controller design of RTP(Rapid Thermal Processing) system using structured uncertainty approach. Using the weighted mixed sensitivity function, we solve the robust stability problem against disturbance and temperature variation, and design a $\mu$ controller using curve fitting method against structured uncertainty. Also the reduction method should be requried because of the difficulty of implementaion with the obtained high order controller. We dal with robust stability and performance of RTP system by the design of $\mu$ controller for original model and Schur balanced reduced model. Finally the simulation results are proposed to show the validity of the proposed method.

• Journal of the korean society of oceanography
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• 제34권1호
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• pp.36-42
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• 1999

To assess present status of polychlorinated biphenyls (PCBs) contamination in Kyeonggi Bay, Namyang Bay, and Lake Shihwa, 63 sediment samples were analyzed and applied to equilibrium partitioning approach. Sediment quality criteria (SQC) for exposure to Kanechlor mixture (KC-mix) was calculated as a value of 16 ${\mu}$g/g-organic carbon (OC). Two sites (Sites Kl8 and Kl9) within Incheon North Harbor (INH) with total PCBs concentrations 48 and 38 ${\mu}$g/g-OC, respectively, exceeded SQC, indicating a potential of adverse biological effects. The advantage and disadvantage of equilibrium partitioning approach has been discussed.

• Journal of applied mathematics & informatics
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• 제25권1_2호
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• pp.1-15
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• 2007

Consider a Rayleigh distribution with $$pdf\;p(x/{\theta})\;=\;2x{\theta}^{-1}\;{\exp}\;({-x^2}/{\theta})$$ and mean lifetime ${\mu}\;=\;\sqrt{\pi\theta}/2$. We study the two-action problem of testing the hypotheses $H_{0}\;:\;{\mu}{\leq}{\mu}_{0}$ against $H_{1}\;:\;{\mu}\;>\;{\mu}_{0}$ using a linear error loss of ${\mid}{\mu}\;-\;{\mu}_{0}{\mid}$ via the empirical Bayes approach. We construct a monotone empirical Bayes test ${\delta}^{*}_{n}$ and study its associated asymptotic optimality. It is shown that the regret of ${\delta}^{*}_{n}$ converges to zero at a rate $\frac{{\ln}^{2}n}{n}$, where n is the number of past data available when the present testing problem is considered.

• 한국식품과학회지
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• 제42권6호
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• pp.762-767
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• 2010

식품 중 사용빈도가 높은 BHT, BHA, TBHQ에 대한 식이 안전성을 평가하고자, 식이를 통한 섭취량 추정 방법과 공급량 자료를 통한 섭취량 추정 방법을 적용하여 한국인의 BHT, BHA, TBHQ 일일추정 섭취량을 평가하였다. 식이를 통한 섭취량 추정을 위해 산화방지제 별로 BHT 131품목(빵 및 떡류, 과자류, 츄잉껌, 식용유지, 식사대용 곡류가공품, 견과류가공품), BHA 134품목(빵 및 떡류, 과자류, 츄잉껌, 견과류가공품, 마가린), TBHQ 104 품목(빵 및 떡류, 과자류, 츄잉껌, 어패류가공품)을 HPLCUVD 시스템을 이용하여 분석한 후 국민건강·영양조사의 식이섭취량자료를 이용하여 BHT, BHA, TBHQ의 일일추정 섭취량을 산출하였다. 공급량 자료를 이용한 섭취량 추정을 위해 식품 공급량과 첨가물 최대 허용량을 근거로 BHT, BHA, TBHQ의 일일추정 섭취량을 산출하였다. 이 결과를 JECFA의 ADI와 비교하여 안전성을 평가하였다. 식이를 통한 섭취량 추정 결과 BHT의 평균 일일추정 섭취량은 0.8 ${\mu}g$/kg body weight/day, BHA의 평균 일일추정 섭취량은 0.5 ${\mu}g$/kg body weight/day, TBHQ의 평균 일일추정 섭취량은 0.3 ${\mu}g$/kg body weight/day로 나타났고, 이는 각각 ADI 대비 0.2, 0.1, 0.04% 이었다. 상위섭취자($90^{th}$ percentile)의 BHT 평균 섭취량은 2.2 ${\mu}g$/kg body weight/day, BHA의 평균 일일추정 섭취량은 1.6 ${\mu}g$/kg body weight/day, TBHQ의 평균 일일추정 섭취량은 0.6 ${\mu}g$/kg body weight/day로 나타났고, 이는 각각 ADI 대비 0.7, 0.3, 0.1% 로 나타나, 한국인의 BHT, BHA, TBHQ 섭취량은 평균섭취자와 상위섭취자 모두에게서 안전한 수준임을 알 수 있었다. 또한 공급량 자료를 이용한 섭취량 추정 결과 BHT, BHA, TBHQ 섭취량은 각각 0.3 mg/kg body weight/day(ADI 대비 97%), 0.3 mg/kg body weight/day(ADI 대비 60%), 0.3 mg/kg body weight/day(ADI 대비 40%)로 나타나, 역시 안전한 수준인 것을 알 수 있었다. 그러나 식이를 통한 섭취량 추정결과와 공급량 자료를 이용한 섭취량 추정 결과 간에 200-480배의 섭취량 차이를 보여, 식품첨가물 섭취량은 그 추정 방법에 따라 많은 차이가 있다는 것을 알 수 있었다.

• 대한전자공학회논문지
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• 제24권3호
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• pp.472-477
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• 1987

In order to prevent the short-channel effects due to threshold voltage adjustment implantation in conventional n+ doped silicon gate process, a new approach involving automatic doping of polycide by boron during source and drain implantation is introduced. P-MOSFET devece fabricated by theis approach shows improved short channel characteristics than conventional device with n+ doped gate. Some concerns of adopting this approach in CMOS technology are addressed togetheer with some suggestions.