• 산업경영시스템학회지
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• 제26권4호
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• pp.42-49
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• 2003

The branch and bound techniques based on cut tree and eigenvector have been Introduced in the literature [1, 2, 3, 6, 9, 12]. These techniques are used as a basis to allocate departments to floors and then to fit departments with unchangeable dimensions into floors. Grouping algorithms to allocate departments to each floor are developed and branch and bound forms the basis of optimizing using the criteria of rectilinear distance. The proposed branch and bound technique, in theory, will provide the optimal solution on two dimensional layout. If the runs are time and/or node limited, the proposed method is a strong heuristic The technique is made further practical by the fact that the solution is constrained such that the rectangular shape dimensions length and width are fixed and a perfect fit is generated if a fit is possible. Computational results obtained by cut tree-based algorithm and eigenvector-based algorithm are shown when the number of floors are two or three and there is an elevator.

• 전자공학회논문지C
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• 제34C권2호
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• pp.38-49
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• 1997

In this paper, w describe partitioning large circuits into multiple chips on the programmable FPCB for rapid prototyping. FPCBs consists of areas for FPGAs for logic and interconnect components, and the routing topology among them are predetermined. In the partition problem for FPCBs, the number of wires ofr routing among chips is fixed, which is an additonal constraints to the conventional partition problem. In order to deal with such aconstraint properly we first define a new partition problem, so called the topologybased partition problem, and then propose a heuristic method. The heuristic method is based on the simulated annealing and clustering technique. The multi-level tree clustering technique is used to obtain faster and better prtition results. In the experimental results for several test circuits, the restrictions for FPCB were all satisfied and the needed execution time was about twice the modified K-way partition method for large circuits.

• 한국통신학회논문지
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• 제31권7B호
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• pp.595-601
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• 2006

이 연구는 유비쿼터스 컴퓨팅 환경에서 절대 위치 좌표를 제공할 수 있는 초음파 위치인식 시스템에 관한 것이다. 무선(RF: Radio Frequency) 신호에 의해 동기화된 다수의 고정된 발신기가 순차적으로 초음파를 발신하며, 초음파 신호들을 수신한 수신기에서 TOF를 파악하여 이를 거리로 환산한 다음 위치정보를 계산한다. 초음파의 전파시간(TOF: Time of Flight)은 주기인식 방법을 통해 파악한다. 또한 유비쿼터스 컴퓨팅을 위한 인식 영역의 확장을 위해 셀 매칭 기법과 부호화된 초음파 기법을 제안한다. 초음파 위치인식 시스템인 U-SAT을 사용하여 주기인식 기법의 유용성을 입증하기 위하여 다양한 거리에서 실험을 수행하였다. 또한 셀 매칭 기법에 의한 영역 확장에서도 위치 측정의 정확도를 검증하였으며 부호화된 초음파 기법의 분석으로 그 유용성도 입증하였다. 그 결과로 인해 저가격, 높은 갱신율, 그리고 상대적으로 뛰어난 정밀도의 입장에서 GPS가 적용될 수 없는 환경에서의 유비쿼터스 컴퓨팅의 위치인식 시스템으로서의 가능성을 입증하였다.

• 한국자동차공학회논문집
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• 제14권3호
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• pp.186-195
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• 2006

In real-time control systems, the traditional timing analysis based on worst-case response-time(WCRT) is too conservative for the firm and soft real-time control systems, which permit the maximum utilization factor greater than one. We suggested a probabilistic analysis method possible to apply the firm and soft real-time control systems under considering dependency relationship between tasks. The proposed technique determines the deadline miss probability(DMP) of each task from computing the average response-time distribution under a fixed-priority scheduling policy. The method improves the predictable ability forthe average performance and the temporal behavior of real-time control systems.

• Nuclear Engineering and Technology
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• 제53권2호
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• pp.399-413
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• 2021

The solution of the time-dependent neutron diffusion equation can be approximated using quasi-static methods that factorise the neutronic flux as the product of a time dependent function times a shape function that depends both on space and time. A generalization of this technique is the updated modal method. This strategy assumes that the neutron flux can be decomposed into a sum of amplitudes multiplied by some shape functions. These functions, known as modes, come from the solution of the eigenvalue problems associated with the static neutron diffusion equation that are being updated along the transient. In previous works, the time step used to update the modes is set to a fixed value and this implies the need of using small time-steps to obtain accurate results and, consequently, a high computational cost. In this work, we propose the use of an adaptive control time-step that reduces automatically the time-step when the algorithm detects large errors and increases this value when it is not necessary to use small steps. Several strategies to compute the modes updating time step are proposed and their performance is tested for different transients in benchmark reactors with rectangular and hexagonal geometry.

• 대한치과보철학회지
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• 제40권6호
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• pp.590-596
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• 2002

The resin : metal interface is at the basis of most bonding failures in resin-bonded prosthesis. Although debonding has been a problem with adhesive fixed partial dentures, various dentists classify them as long-term restorations. The advantages of resin-bonded fixed partial dentures include minimal tooth reduction and the possibility of rebonding. if resin-bonded protheses can be easily rebounded, it is of clinical importance to know if the lutingagents rebond as well the second time as they did originally. Several retentive systems for resin-to-metal bonding have recommended. Treatments such as electrolytic etching and silicone coating, despite the good result of bond strength, have proved to be time-consuming and technique-sensitive. Therefore a simple and more reliable method is desirable. This study evaluated the effect of metal surface treatments on the rebond strength of panavia 21 cement to a nickel-chromium(Ni-Cr) alloy. The samples were received the following surface treatments : Group No.1 (control or served as the control) treatment with sandblasting with 50um aluminum oxide and ultrasonically cleaned for 10minutes in double-deionized water, Group No.2 were no surface treatments. Group No.3 were treated with metal primer. Group No.4 were treated with sandblasting as previously described, and then metal priming. From the analysis of the results, the following conclusions were drawn. 1. Sandblasting and metal priming appears to be an effective method for treatment of metal after accidental debonding. 2. Group without surface treatment had significantly lower bond strengths compared with other groups. 3. The combination of sandblasting and metal priming may not develop superior bonding strengths compared with other techniques that used the Ni-Cr alloys. 4. Combination of cohesive and adhesive failures were the most common type observed. The results support the use of sandblasting as a viable procedure when rebonding accidentally lost adhesive partial denture. We concluded that sandblasting and metal priming of metal surface before bonding could provide the adequate bond strength during rebonding of resin-bonded fixed partial denture.

• 한국멀티미디어학회논문지
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• 제3권2호
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• pp.101-111
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• 2000

VBR로 압축된 멀티미디어 데이터는 비트 변화율이 매우 큰 편차로 변하기 때문에 자원 예약 관리가 매우 힘들다. 따라서 VOD 서버는 MPEG데이터의 참조 패턴을 오프라인으로 분석한 메타 테이블을 근거로 과부하구간에서 미리 선반입하여 시스템 활용율을 높이는 선반입 기법을 사용한다. 이러한 선반입 기법을 과부하구간에서도 상영실패는 발생하지 않으나, 선반입 임계슬롯이 증가함으로써 버퍼 점유량이 증가하여 버퍼의 최소 적재시간과 적재비용을 유지할 수 없다. 따라서 본 논문에서는 선반입 구간을 고정적으로 사용하여, 과부하 구간에서도 적재비용과 적재시간을 일정한 범위 이하로 유지하면서 시스템 자원의 활용율을 높이는 방법을 제안한다. 그리고 선반입 구간을 고정시킴으로써 발생하는 상영 실패는 Drop 모듈을 사용하여 GOP내의 B프레임에 한정하며, 미디어의 질 저하를 전체 사용자에게 고르게 분산시키는 방법을 제안한다.

• 한국정밀공학회지
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• 제12권5호
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• pp.57-68
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• 1995

A general procedure for the numerical solution of coupled, nonlinear, differential two-point boundary-value problems, solutions of which are crucial to the controller design, has been developed and demonstrated. A fixed-end-points, free-terminal-time, optimal-control problem, which is derived from Pontryagin's Maximum Principle, is solved by an extension of Davidenko's method, a differential form of Newton's method, for algebraic root finding. By a discretization process like finite differences, the differential equations are converted to a nonlinear algebraic system. Davidenko's method reconverts this into a pseudo-time-dependent set of implicitly coupled ODEs suitable for solution by modern, high-performance solvers. Another important advantage of Davidenko's method related to the time-optimal problem is that the terminal time can be computed by treating this unkown as an additional variable and sup- plying the Hamiltonian at the terminal time as an additional equation. Davidenko's method uas used to produce optimal trajectories of a single-degree-of-freedom problem. This numerical method provides switching times for open-loop control, minimized terminal time and optimal input torque sequences. This numerical technique could easily be adapted to the multi-point boundary-value problems.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2001년도 Proceeding of KIN-CIN Joint Symposium 2001 on Satellite Navigation/AIS, lntelligence , Computer Based Marine Simulation System and VDR
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• pp.19-25
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• 2001

At present the identification of vessels is still depending on the OOW (Officer Of Wateh) in VTS (Vessel Traffic Service), which is completed by radar, and also by the combination of VHF radio and VHF direction finder. However, with the development of port transportation and economic, this conventional way of identification can't satisfy more and more request for the information that the VTS needs from the vessels. In such a case, the AIS(Automatic Identification System) precept which is based on STDMA (Self-organized Time Division Multiple Access) technique is put forward by IMO (International Maritime Organization). AIS can automatically provide the information, including own ship's identification, type, position, course, speed, and other information to the appropriately equipped coast station and other ships. At the same time it can also automatically monitor and track the nearby ships similarly fitted with AIS. On the basis of describing the whole comprising and the format of transmission information of AIS, this paper mainly studies the key communication techniques in AIS, such as STDMA protocol, net synchronization and GMSK(Gaussian Minimum Shift Keying)technique, and so on. At last this paper briefly introduces the recommendation decided by IMO on forcing the sea-going ships to fixed with AIS equipments, and it continuos with the unexploited potential of AIS if it applies in VTS.

• 정보처리학회논문지C
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• 제13C권5호
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• pp.559-566
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• 2006

연결요청(connection request) 패킷의 전송비율을 일정 비율 이하로 제한함으로써 월 발생을 탐지하는 바이러스 쓰로틀링(virus throttling)은 대표적인 웜 조기 탐지 기술 중의 하나이다. 기존 바이러스 쓰로틀링은 비율 제한기의 주기를 고정시키고 지연 큐 길이를 감시하여 웜 발생 여부를 판단한다. 본 논문에서는 가중치 평균 지연 큐 길이를 적용하여 비율 제한기의 주기를 자율적으로 조절하는 알고리즘을 제안하고, 가중치 평균 지연 큐 길이에 따른 다양한 주기결정 기법을 제시한다. 실험결과 제안 알고리즘은 웜 탐지시간에는 크게 영향을 미치지 않으면서도 연결설정 지연시간을 단축하여 사용자가 느끼는 불편함을 줄여 줄 수 있음을 확인하였다.