• 제어로봇시스템학회논문지
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• 제5권3호
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• pp.363-369
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• 1999

In this paper, we design the robust $H_{\infty}$ controller for water level control of steam generator using a mixed $H_{\infty}$ optimization with model-matching method. Firstly we choose the desired model which has good disturbance rejection performance. Secondly we design a stabilizing controller to keep the model-matching error small and also provide sufficiently large stability margin against additive perturbations of the nominal plant. Simulation results show that proposed robust $H_{\infty}$ controller at specific power operation has satisfactory performances against the variations of load power, steam flow rate, primary circuit coolant temperature, and feedwater temperature. It can be also observed that the proposed robust $H_{\infty}$ controller exhibits better robust stability than conventional PI controller.

• 대한산업공학회지
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• 제25권3호
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• pp.351-359
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• 1999

We present a new approach to the analysis of mobile cellular communication systems under the environment of mixed platforms adopting a guard channel scheme. We assume general cell residence time distributions according to platform-types. Our system model is based on a heterogeneous M/G/c loss system with customer-dependent guard channels, where heterogeneous customers with different service time distributions have different numbers of their own guard channels. We develop the general formula of steady state probabilities for the heterogeneous M/G/c loss system with customer-dependent guard channels. The mean channel occupancy times of new and handoff calls are rigorously derived under a general setting. Finally, our numerical results show that the blocking probability and the forced termination probability are sensitive to the cell residence time distributions.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2001년도 추계학술대회 논문집
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• pp.72-75
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• 2001

This paper presents a sophisticated mixed-integer linear programming model that may help regional decision-maker to develop long term plan of solid waste management The model revises Ni-Bin Chang(1996)'s integrated waste management models to fit Korean solid waste management system We apply this model to evaluate impact of facility sharing and coordinated operation among three self-governing districts in Seoul city Our study results indicate that facility sharing and coordinated operation among districts eliminate unnecessary landfilling and facility expansion.

• 대한전기학회논문지
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• 제36권9호
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• pp.660-669
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• 1987

Routh approximation method is the most computationally attractive. But this method may cause time-response error because this method does not match the time-response directly. In this paper a new mixed method for obtaining stable reduced-order models for high-order continuous-time systems is proposed. It makes use of the advantages of the Routh approximation method and the Minimization of Integral Squared Error(MISE) criterion approach. In this mixed method the characteristic polynomial of the reduced-order model is first obtained from that of original system by using the Auxiliary Denominator Polynomial(ADP). The numerator polynomial is then determined so as to minimize the intergral squared-error of unit step responses. The advantages of the propsed method are that the reduced models are always stable if the original system are stable and the frequency domain and time domain characteristic of the original system will be preserved in the reduced models.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제16권4호
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• pp.462-466
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• 2010

본 논문은 하드디스크와 NAND 플래시메모리를 동시에 사용하는 저장 시스템 환경에서 전력 소모를 최소화하는 버퍼 캐쉬 관리 기법을 제안한다. 저장장치별 전력 소모율과 입출력 연산 종류(읽기 또는 쓰기) 및 블록의 재참조 가능성(최근성 및 빈도)을 통합적으로 고려하는 버퍼 캐쉬 관리 기법의 설계로 저장 시스템의 전력 소모량을 평균 18.0%, 최대 58.9%까지 줄일 수 있음을 보인다.

• 한국수소및신에너지학회논문집
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• 제19권1호
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• pp.26-34
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• 2008

This study presents an aerodynamic design and an experimental performance test of a turbo air compressor consisted of mixed-flow impeller and curved diffuser for the PEM fuel cell vehicle application. Many studies compare the efficiency, cost or noise level of high-pressure and low-pressure operation of PEM fuel cell systems. Pressure ratio 2.2:1 is considered as design target The goal of compressor design is to enlarge the flow margin of compressor from surge to choke mass flow rate to cover the operational envelope of FCV. Large-scale rig test is performed to evaluate the compressor performance and to compare the effects of compressor exit pipe volume to stall or surge characteristics. The results show that the mixed-flow compressor designed has large flow margin, and the flow margin of compressor configuration with small exit volume is larger than that with large exit volume.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.368-375
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• 2010

To alleviate NOx emission, a variety of approaches has been applied. In marine diesels, the application of SCR systems has been considered an effective exhaust aftertreatment method for NOx emission control. Most current SCR systems use a various catalyst for the reaction of ammonia with NOx to form nitrogen and water. In theory, it is possible to achieve 100% NOx if the NH3-to-NOx ratio is 1:1. However, the reaction has a limited non-uniformity of the exhaust gas flow and ammonia concentration distribution. Therefore it is necessary to investigate the optimum flow conditions. In order to achieve uniform flow at monolith front face, we are equipped with a various mixed device. In this paper, it is presented that the mixed devices play an important role improvement of flow patterns and particle distributions of NH3 by numerical simulation.

• 한국전산유체공학회지
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• 제15권4호
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• pp.9-16
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• 2010

To alleviate NOx emission, a variety of approaches has been applied. In marine diesels, the application of SCR systems has been considered an effective exhaust aftertreatment method for NOx emission control. Most current SCR systems use a various catalyst for the reaction of ammonia with NOx to form nitrogen and water. In theory, it is possible to achieve 100% NOx if the $NH_3$-to-NOx ratio is 1:1. However, the reaction has a limited non-uniformity of the exhaust gas flow and ammonia concentration distribution. Therefore, it is necessary to investigate the optimum flow conditions. In order to achieve uniform flow at monolith front face, we are equipped with a various mixed devices. In this paper, it is presented that the mixed devices play an important role improvement of flow patterns and particle distributions of $NH_3$ by numerical simulation.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.575-580
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• 1992

Mixed H$_{2}$/H$_{\infty}$ robust control synthesis is considered for finite dimensional linear time-invariant systems under the presence of diagonal structured uncertainties. Such uncertainties arise for instance when there is real perturbation in the nominal model of the state space system or when modeling multiple (unstructured) uncertainty at different locations in the feedback loop. This synthesis problem is reduced to convex optimization problem over a bounded subset of matrices as well as diagonal matrix having certain structure. For computational purpose, this convex optimization problem is further reduced into Generalized Eigenvalue Minimization Problem where a powerful algorithm based on interior point method has been recently developed..

• 제어로봇시스템학회논문지
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• 제4권4호
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• pp.458-463
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• 1998

This paper presents an autopilot design method for STT missiles using the intelligent control technique and multiple controllers. The mixed $H_2/H_{\infty}$ control technique is applied for each controller design and the control gains are implemented by using the genetic searching algorithm. To facilitate automatic switching of multiple controllers under different operating conditions, an error based switching scheme is also combined with the multiple controllers at a higher level, which constitutes a hierarchical intelligent control system. It is shown via computer simulation that the proposed autopilot outperforms the conventional one.