• Proceedings of the Korea Inteligent Information System Society Conference
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• 2007.05a
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• pp.239-245
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• 2007

차세대 유비쿼터스 환경에서 중요한 기술적, 산업적 위치를 차지하는 RFID 네트워크에는 다수의 RFID 리더(Reader)와 수많은 RFID 태그(Tag)들이 통신을 하면서 존재하게 된다. 이러한 RFID 네트워크에서 리더와 태그간의 원활한 통신을 위해서는 주파수 충돌이 발생하지 않아야 한다. 주파수 충돌 현상은 리더와 다수의 태그들 간의 태그 충돌(Tag Collision)과 리더간 주파수 간섭으로 인한 리더간 충돌(Reader Collision)로 나뉘어 질 수 있다. 따라서 리더간 충돌 현상을 피하기 위해서는 근접한 리더들 간에 서로 다른 타임슬롯(Timeslot)을 사용하여 태그와 통신을 시도하여야 한다. 본 연구에서는 RFID 네트워크에서 다수의 리더간 충돌을 최소화하며 안전한 태그 인식을 할 수 있도록 타임 슬롯 할당 문제를 CSP(Constraint Satisfaction Problem)로 접근한다. 그리고 CSP를 풀기 위해 리더간 충돌 문제가 가지고 있는 제약조건을 찾아내고 해를 찾기 위한 목적함수를 모델링 한다.

• Journal of Mechanical Science and Technology
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• v.14 no.6
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• pp.655-665
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• 2000

We propose an efficient algorithm for the purpose of satisfying a wide range of design constraints represented with equality and inequality equations as well as production rules. The algorithm employs simulated-annealing and a production rule inference engine and works on design constraints represented with networks. The algorithm fulfills equality constraints through constraint satisfaction processes like variable elimination while taking into account inequality constraints and inferring production rules. It can also reduce the load of the optimization procedure if necessary. We demonstrate the implementation of the algorithm with the result on machine tool design.

• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.2
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• pp.125-129
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• 2004

There are several kinds of fuzzy set extensions in the fuzzy set theory. Among them, this paper is concerned with interval-valued fuzzy sets, intuitionistic fuzzy sets, and bipolar-valued fuzzy sets. In interval-valued fuzzy sets, membership degrees are represented by an interval value that reflects the uncertainty in assigning membership degrees. In intuitionistic fuzzy sets, membership degrees are described with a pair of a membership degree and a nonmembership degree. In bipolar-valued fuzzy sets, membership degrees are specified by the satisfaction degrees to a constraint and its counter-constraint. This paper investigates the similarities and differences among these fuzzy set representations.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04b
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• pp.283-285
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• 2002

강의시간표 문제(Lecture timetabling Problem)는 일주일을 기본으로 하는 특정 시간대 별로 학생(Course-class), 교수, 그리고 강의실과 같은 자원에 대한 스케줄링 문제로서 각각의 자원에 대하여 적절한 조합으로 제약조건들 사이의 충돌을 최소화하여 자원을 배치하는 할당문제이다. 강의시간표 문제는 수천 명 학생들에 대하여 개개인의 시간표를 작성해야 하므로 기하급수적으로 증가하는 탐색공간에 대하여 최악의 경우 탐색 시간이 지수적으로 증가하는 NP-complete Problem이다. 이러한 거대하고 복잡한 강의시간표 문제는 계층적으로 분할하여 기능별로 처리하면서 제약조건을 협상하도록 하는 각 모듈 단위의 에이전트를 구성하므로 좀 더 작고 단순한 문제로 변환될 수 있다. 본 논문에서는 방대한 탐색 공간과 과잉-제약조건(Over-constraint)문제의 하나인 강의시간표 작성 문제를 분산제약조건 만족 문제 특성을 이용하고 다중 에이전트 구조를 사용하여 해결하는 강의시간표 자동화 시스템 설계를 제안한다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2001.05a
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• pp.12-15
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• 2001

There are several kinds of fuzzy set extensions in the fuzzy set theory. Among them, this paper is concerned with interval-valued fuzzy sets, intuitionistic fuzzy sets, and bipolar-valued fuzzy sets. In interval-valued fuzzy sets, membership degrees are represented by an interval value that reflects the uncertainty in assigning membership degrees. In intuitionistic sets, membership degrees are described with a pair of a membership degree and a nonmembership degree. In bipolar-valued fuzzy sets, membership degrees are specified by the satisfaction degrees to a constraint and its counter-constraint. This paper investigates the similarities and differences among these fuzzy set representations.

• Journal of Korean Institute of Industrial Engineers
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• v.17 no.2
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• pp.51-61
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• 1991

This paper presents a heuristic method for the Assembly Line Balancing(ALB) of the large-sized product. In the ALB problem of the large-sized product such as bus and truck, the assignments of the Related Task Groups(RTG), the same side tasks, and team tasks should be considered. In this paper, a new concept of the RTG and two kinds of assignment rules are proposed to resolve the above considerations. The first assignment rule allots the RTG with the constraint of the same side tasks to the station while the second allots the RTG to the station, relaxing the above constraint to increase the applicability of the method. An assignment rule for team tasks is also presented. The benefits of the method are to improve work methods, to give more job satisfaction to workers, and to allow greater flexibility in the design of assembly lines.

• Journal of Korean Institute of Industrial Engineers
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• v.21 no.2
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• pp.207-216
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• 1995

Constructing a distributed management system has its own advantages in addressing the issue of implementing a quick responsive management system in dynamically changing environment of enterprise. We suggest a basic scheduling methodology applicable to a distributed production management system. A new concept of "flexible schedule" is introduced as a tool to accommodate dynamically changing situations of job shops. Then a search technique (referred to as CSP-CBA search) is presented to obtain such a schedule for the job shop scheduling problem, which is converted into a constraint satisfaction problem(CSP), by using the constraint based analysis(CBA). This approach is tested on more than 100 test problems. The results show that the suggested approach required shorter CPU time and solved more problems in given time than another fixed schedule method.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.1-1
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• 2009

In this presentation, I talk about various fluid simulation methods that have been developed for computer graphics special effects since 1996. They are all based on CFD but sacrifice physical reality for visual plausability and time. But as the speed of computer increases rapidly and the capability of GPU (graphics processing unit) improves, methods for more physical realism have been tried. In this talk, I will focus on four aspects of fluid simulation methods for computer graphics: (1) particle level-set methods, (2) particle-based simulation, (3) methods for exact satisfaction of incompressibility constraint, and (4) GPU-based simulation. (1) Particle level-set methods evolve the surface of fluid by means of the zero-level set and a band of massless marker particles on both sides of it. The evolution of the zero-level set captures the surface in an approximate manner and the evolution of marker particles captures the fine details of the surface, and the zero-level set is modified based on the particle positions in each step of evolution. (2) Recently the particle-based Lagrangian approach to fluid simulation gains some popularity, because it automatically respects mass conservation and the difficulty of tracking the surface geometry has been somewhat addressed. (3) Until recently fluid simulation algorithm was dominated by approximate fractional step methods. They split the Navier-Stoke equation into two, so that the first one solves the equation without considering the incompressibility constraint and the second finds the pressure which satisfies the constraint. In this approach, the first step introduces error inevitably, producing numerical diffusion in solution. But recently exact fractional step methods without error have been developed by fluid mechanics scholars), and another method was introduced which satisfies the incompressibility constraint by formulating fluid in terms of vorticity field rather than velocity field (by computer graphics scholars). (4) Finally, I want to mention GPU implementation of fluid simulation, which takes advantage of the fact that discrete fluid equations can be solved in parallel.

• Culinary science and hospitality research
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• v.15 no.4
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• pp.187-199
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• 2009

The objective of the research is to investigate the causal relationships among functional value, emotional value, social value, perceived sacrifice, satisfaction, loyalty and behavioral intention. All in all, 296 respondents completed a questionnaire themselves in the presence of an interviewer who could be consulted about the response scales and other technical matters. Behavioral intention models were estimated by structural equation modelling using 7 latent constructs. The results demonstrated that the confirmatory factor analysis model provided a good model fit. The unconstrained model yielded a significantly better fit to the data than the constraint model. The effects of functional value and social value on satisfaction and behavioral intention were statistically significant. The effects of perceived sacrifice, satisfaction and loyalty on behavioral intention were statistically significant. As expected, satisfaction had a significant effect on loyalty. Functional value had an indirect effect on behavioral intention through satisfaction and loyalty. Moreover, social value had an indirect effect on behavioral intention through satisfaction and loyalty. Replicating and extending this study in other regions and other samples would test the generalizability of the present findings and provide a basis for an external validation of the framework developed in this paper.

• IE interfaces
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• v.7 no.1
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• pp.59-66
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• 1994

In scheduling open-field type FMS, process planning of decision making between alternate machines is taken into consideration. This idea is validated via implementing two experimental systems; One is a knowledge-based system and the other is to solve a Constraint Satisfaction Problem. The former generates some promising schedules in view of improving machine utilization, makespan and meanflow time, and the latter does in view of meeting due date.