• Earthquakes and Structures
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• 제10권6호
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• pp.1253-1272
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• 2016

For a nonlinear control system, there are many uncertainties, such as the structural model, controlled parameters and external loads. Although the significant progress has been achieved on the robust control of nonlinear systems through some researches on this issue, there are still some limitations, for instance, the complicated solving process, weak conservatism of system, involuted structures and high order of controllers. In this study, the computational structural mechanics and optimal control theory are adopted to address above problems. The induced norm is the eigenvalue problem in structural mechanics, i.e., the elastic stable Euler critical force or eigenfrequency of structural system. The segment mixed energy is introduced with a precise integration and an extended Wittrick-Williams (W-W) induced norm calculation method. This is then incorporated in the market-based control (MBC) theory and combined with the force analogy method (FAM) to solve the MBC robust strategy (R-MBC) of nonlinear systems. Finally, a single-degree-of-freedom (SDOF) system and a 9-stories steel frame structure are analyzed. The results are compared with those calculated by the $H{\infty}$-robust (R-$H{\infty}$) algorithm, and show the induced norm leads to the infinite control output as soon as it reaches the critical value. The R-MBC strategy has a better control effect than the R-$H{\infty}$ algorithm and has the advantage of strong strain capacity and short online computation time. Thus, it can be applied to large complex structures.

• 한국경영과학회지
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• 제23권2호
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• pp.29-46
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• 1998

In this paper, we develop detailed algorithms for implementing the so-called Limited Column Generation procedure for Local Access Telecommunication Network(LATN) design problem. We formulate the problem into a tree-partitioning problem with an exponential number of variables. Its linear programming relaxation has all integral vertices, and can be solved by the Limited Column Generation procedure in just n pivots, where n is the number of nodes in the network. Prior to each pivot. an entering variable is selected by detecting the Locally Most Violated(LMV) reduced cost, which can be obtained by solving a subproblem in pseudo-polynomial time. A critical step in the Limited Column Generation is to find all the LMV reduced costs. As dual variables are updated at each pivot, the reduced costs have to be computed in an on-line fashion. An efficient implementation is developed to execute such a task so that the LATN design problem can be solved in O(n$^2$H), where H is the maximum concentrator capacity. Our computational experiments indicate that our algorithm delivers an outstanding performance. For instance, the LATN design problem with n＝150 and H＝1000 can be solved in approximately 67 seconds on a SUN SPARC 1000 workstation.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1995년도 춘계공동학술대회논문집; 전남대학교; 28-29 Apr. 1995
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• pp.54-68
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• 1995

In this paper, we develop detailed algorithms for implementing the so-called Limited Column Generation procedure for Local Access Telecommunication Network (LATN) Design problem. We formulate the problem into a tree-partitioning problem with an exponential number of variables. Its linear programming relaxation has all integral vertices, and can be solved by the Limited Column. Generation procedure in just n pivots, where n is the number of nodes in the network. Prior to each pivot, an entering variable is selected by detecting the Locally Most Violated (LMV) reduced cost, which can be obtained by solving a subproblem in pseudo-polynomial time. A critical step in the Limited Column Generation is to find all the LMV reduced costs. As dual variables are updated at each pivot, the reduced costs have to be computed in an on-line fashion. An efficient implementation is developed to execute such a task so that the LATN Design problem can be solved in O(n$^{2}$H), where H is the maximum concentrator capacity. Our computational experiments indicate that our algorithm delivers an outstanding performance. For instance, the LATN Design problem with n = 150 and H = 1000 can be solved in approximately 67 seconds on a SUN SPARC 1000 workstation.

• 유통과학연구
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• 제15권12호
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• pp.21-30
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• 2017

Purpose - This research approaches to the new niche market of medical tourism to investigate how factors of cultural similarity influence the international distribution management. This study also estimates the interaction effects of distribution channel on the relationships of facility attributes and customers' destination choice behavior. Research design, data, and methodology - We collected the sample of 881 potential customers from the more economically developed regions in China. Regression analysis is used to confirm the relationships in the research model. Results - The result shows that cultural similarity plays an important moderating role in the relationships of facility attributes and destination choice intention. For instance, power distance and masculinity interact with the distribution facility characteristics of medical quality and reputation to influence customers' selection of the destination country. Individualism, powder distance, and masculinity play moderating roles when social environment affects destination choice intention. Especially, all the elements of cultural similarity moderate the relationships between travel cost and destination choice intention. This research also proves that depending on distribution channel, determinants of distribution facility are the critical predictors of intention to select the medical service outside of China. Conclusions - The study enables managers to develop the more effective strategies reflecting the interaction effects of cultural similarity and distribution channel on customers' decision-making process.

• 전자공학회지
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• 제25권5호
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• pp.31-41
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• 1998

With the advent of portable electronic systems, power consumption has recently become a major issue in circuit and system design. Furthermore, the sophisticated fabrication technology makes it possible to embed more functions and features in a VLSI chip, consequently calling for both higher performance and lower power to deal with the ever growing complexity of system algorithms than in the past. VLSI designers should cope with two conflicting constraints, high performance and low power, offering an optimum trade off of these constraints to meet requirements of system. Historically, VLSI designers have focused on performance improvement, and power dissipation was not a design criteria but an afterthought. This design paradigm should be changed, as power is emerging as the most critical design constraint. In VLSI design, low power design can be accomplished through many ways, for instance, process, circuit/logic design, architectural design, and etc.. In this paper, a few low power design examples, which have been used in 8 bit micro-controller core, and can be used also in 4/16/32 bit micro-controller cores, are presented in the areas of circuit, logic and architectural design. We first propose a low power guidelines for micro-controller design in SAMSUNG, and more detailed design examples are followed applying 4 specific design guidelines. The 1st example shows the power reduction through reduction of number of state clocks per instruction. The 2nd example realized the power reduction by applying RISC(Reduced Instruction Set Computer) concept. The 3rd example is to optimize the algorithm for ALU(Arithmetic Logic Unit) to lower the power consumption, Lastly, circuit cells designed for low power are described.

• 한국자동차공학회논문집
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• 제13권1호
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• pp.194-203
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• 2005

The process of guaranteeing that a distributed real-time control system will meet its timing constraints, is referred to as schedulability analysis. However, schedulability analysis algorithm cannot be simply used to analyze the system because of complex calculations of algorithm. It is difficult for control engineer to understand the algorithm because it was developed in a software engineer's position. In this paper we introduce a Response-time Analysis Tool(RAT) which provides easy way far system designer to analyze the system by encapsulating calculation complexity. Based on the RAT, control engineer can verify whether all real-time tasks and messages in a system will be completed by their deadline in the system design phase.

• 한국IT서비스학회지
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• 제16권3호
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• pp.103-111
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• 2017

The real time scheduling is a key research area in high performance computing and has been a source of challenging problems. A periodic task is an infinite sequence of task instance where each job of a task comes in a regular period. The RMS (Rate Monotonic Scheduling) algorithm has the advantage of a strong theoretical foundation and holds out the promise of reducing the need for exhaustive testing of the scheduling. Many real-time systems built in the past based their scheduling on the Cyclic Executive Model because it produces predictable schedules which facilitate exhaustive testing. In this work we propose hybrid scheduling method which combines features of both of these scheduling algorithms. The original rate monotonic scheduling algorithm didn't consider the uniform sampling tasks in the real time systems. We have enumerated some issues when the RMS is applied to our hybrid scheduling method. We found the scheduling bound for the hard real-time systems which include the uniform sampling tasks. The suggested hybrid scheduling algorithm turns out to have some advantages from the point of view of the real time system designer, and is particularly useful in the context of large critical systems. Our algorithm can be useful for real time system designer who must guarantee the hard real time tasks.

• Journal of Communications and Networks
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• 제16권2호
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• pp.121-129
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• 2014

The trend of an increasing demand for a high-quality user experience, coupled with a shortage of radio resources, has necessitated more advanced wireless techniques to cooperatively achieve the required quality-of-experience enhancement. In this study, we investigate the critical problem of rate splitting in heterogeneous cellular networks, where concurrent transmission, for instance, the coordinated multipoint transmission and reception of LTE-A systems, shows promise for improvement of network-wide capacity and the user experience. Unlike most current studies, which only deal with spectral efficiency enhancement, we implement an optimal rate splitting strategy to improve both spectral efficiency and energy efficiency by exploring and exploiting cooperation diversity. First, we introduce the motivation for our proposed algorithm, and then employ the typical cooperative bargaining game to formulate the problem. Next, we derive the best response function by analyzing the dual problem of the defined primal problem. The existence and uniqueness of the proposed cooperative bargaining equilibrium are proved, and more importantly, a distributed algorithm is designed to approach the optimal unique solution under mild conditions. Finally, numerical results show a performance improvement for our proposed distributed cooperative rate splitting algorithm.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.251-261
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• 2006

FMEA(Failure Mode and Effects)분석 기법이란 제품의 신뢰성을 높이기 위해, 잠재적 고장 모드를 선별하고 이의 고장 원인과 영향을 분석하여 고장이 제품에 미치는 영향을 최소화하기 위한 분석기법이다. 최근 FMEA기법이 많은 산업 분야에서 널리 쓰이고 있으며, 각 분야별로 그에 알맞게 특화된 FMEA기법이 제안되어 있다. 대표적으로 방산 분야의 MIL-1629a, 자동차 분야의 SAE-J1739 등을 들 수 있으며, 그 외의 많은 산업분야에서도 특화된 FMEA규격을 사용하고 있다. 하지만 높은 신뢰성이 요구되는 철도 산업의 경우에는 아직까지 특화된 FMEA규격은 제시되어 있지 못한 실정이다. 본 논문에서는 SAE-J1739,MIL-1629a, IEC-60812의 규격을 비교 분석함으로써 철도 시스템에 특화된 FMEA규격을 제안하였다.

• 한국기계가공학회지
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• 제19권11호
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• pp.87-93
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• 2020

A key component of aviation safety is to eliminate the errors in commercial aircraft air data systems to ensure stable aviation operation. Although the technical aspects such as the maintenance and inspection play a pertinent role, human errors are expected to have a similar or even larger influence on the aviation safety. Aviation maintenance and inspection tasks are often performed by a complex organization, in which individuals perform a variety of tasks in an environment involving time pressure, sparse feedback, and complex conditions. These situational characteristics, combined with the general tendency of human error, may lead to various types of errors, which may have critical consequences such as accidents and loss of life. For instance, if an amber message "IAS DISAGREE" is displayed on the primary flight display while the aircraft is rolling on the runway to takeoff, the crew immediately performs a rejected takeoff operation and troubleshoots the air data system. This paper proposes alternative approaches to address the occurrence of defects due to the human factors involved in the practical processes of the air data system of commercial aircraft.