• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.956-959
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• 2004

Recently the monitoring system of tool setting in high speed precision machining center is required for manufacturing products that have highly complex and small shape, high precision and high function. It is very important to reduce time to setup tool in order to improve the machining precision and the productivity and to protect the breakage of cutting tool as the shape of product is smaller and more complex. Generally, the combination of errors that geometrical clamping error of fixing tool at the spindle of machining tool and the asynchronized error of driving mechanism causes that the run-out of tool reaches to 3$^{\sim}$20 times of the thickness of cutting chip. And also the run-out is occurred by the misalignment between axis of tool shank and axis of spindle and spindle bearing in high speed rotation. Generally, high speed machining is considered when the rotating speed is more than 8,000 rpm. At that time, the life time of tool is reduced to about 50% and the roughness of machining surface is worse as the run-out is increased to 10 micron. The life time of tool could be increased by making monitoring of tool-setup easy, quick and precise in high speed machining tool. This means the consumption of tool is much more reduced. And also it reduces the manufacturing cost and increases the productivity by reducing the tool-setup time of operator. In this study, in order to establish the concept of tool-setup monitoring the measuring method of the geometrical error of tool system is studied when the spindle is stopped. And also the measuring method of run-out, dynamic error of tool system, is studied when the spindle is rotated in 8,000${\sim}$60,000 rpm. The dynamic phenomena of tool-setup are analyzed by implementing the monitoring system of rotating tool system and the non-contact measuring system of micro displacement in high speed.

• 한국통계학회:학술대회논문집
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• 한국통계학회 2004년도 학술발표논문집
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• pp.301-306
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• 2004

We consider the $P_\lambda\;^M$ service policy for an M/G/1 queue in which the service rate is increased from 1 to M at the exponential setup time after the level of workload exceeds $\lambda$. The stationary distribution of the workload is explicitly obtained through the level crossing argument.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2003년도 춘계학술대회논문집
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• pp.129-134
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• 2003

In this paper, we determine optimal reduction in the lead time and setup cost for some stochastic inventory models. And we propose more general model that allow the backorder rate as a control variable. We first assume that the lead time demand follows a normal distribution. And we assume that the backorder rate is dependent on the length of lead time through the amount of shortages. The stochastic models analyzed in this paper are the classical continuous and periodic review policy models with a mixture of backorders and lost sales. For each of these models, we provide a sufficient conditions for the uniqueness of the optimal operating policy. We also develop algorithms for solving these models and provide illustrative numerical examples.

• 한국컴퓨터정보학회논문지
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• 제22권10호
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• pp.101-107
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• 2017

In this paper, we study the problem of parallel machine scheduling considering the moving time of multiple servers. The parallel machine scheduling is to assign jobs to parallel machines so that the total completion time(makespan) is minimized. Each job has a setup phase, a processing phase and a removal phase. A processing phase is performed by a parallel machine alone while a setup phase and a removal phase are performed by both a server and a parallel machine simultaneously. A server is needed to move to a parallel machine for a setup phase and a removal phase. But previous researches have been done under the assumption that the server moving time is zero. In this study we have proposed an efficient algorithm for the problem of parallel machine scheduling considering multiple server moving time. We also have investigated experimentally how the number of servers and the server moving time affect the total completion time.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권1호
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• pp.11-22
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• 2016

Clock skew scheduling is one of the essential steps to be carefully performed during the design process. This work addresses the clock skew optimization problem integrated with the consideration of the inter-dependent relation between the setup and hold times, and clock to-Q delay of flip-flops, so that the time margin is more accurately and reliably set aside over that of the previous methods, which have never taken the integrated problem into account. Precisely, based on an accurate flexible model of setup time, hold time, and clock-to-Q delay, we propose a stepwise clock skew scheduling technique in which at each iteration, the worst slack of setup and hold times is systematically and incrementally relaxed to maximally extend the time margin. The effectiveness of the proposed method is shown through experiments with benchmark circuits, demonstrating that our method relaxes the worst slack of circuits, so that the clock period ($T_{clk}$) is shortened by 4.2% on average, namely the clock speed is improved from 369 MHz~2.23 GHz to 385 MHz~2.33 GHz with no time violation. In addition, it reduces the total numbers of setup and hold time violations by 27.7%, 9.5%, and 6.7% when the clock periods are set to 95%, 90%, and 85% of the value of Tclk, respectively.

• 한국전자통신학회논문지
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• 제10권8호
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• pp.883-890
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• 2015

반도체 공정 기술의 발전으로 하나의 칩에 많은 코어가 포함되고 있으며, 전력이나 클럭 스큐 문제들을 해결하기 위한 방안으로 다른 주파수나 위상차를 가지고 있는 여러 개의 클럭을 사용하는 GALS 기법이 사용되고 있다. GALS에서는 송수신부 사이에서 동기화 문제를 해결하기 위하여 동기회로가 사용된다. 본 논문에서는 180nm CMOS 공정 파라미터를 사용하여 온도, 전원전압, 트랜지스터의 크기에 따라 동기회로 설계에 필요한 DFF의 준비시간(setup time)과 유지시간(hold time)를 측정하였다. HSPICE의 이분법을 이용한 모의실험 결과에서 준비시간과 유지시간의 크기는 전원 전압의 크기에 반비례하고, 온도에 비례하였다. 그리고 유지시간은 음의 값으로 측정되었다.

• 대한전자공학회논문지TC
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• 제43권11호
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• pp.192-199
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• 2006

최근 인터넷 트래픽의 급격한 증가로 다양한 트래픽 처리를 위한 대역폭 확보 및 효율적인 트래픽 처리 기술이 요구되고 있다. 이러한 요구에 백본네트워크에서 발생하는 트래픽 처리를 위한 다양한 경로설정 알고리즘이 소개되고 있지만 획일적인 노드 운용으로 부분적인 링크에서의 경로 설정 실패 확률을 증가시키고 있다. 즉, 미리 결정된 최대 채널 설정 허용 시간은 한정적인 설정 성공률을 가지며 이후 발생되는 트래픽의 손실 확률을 증가시킬 수 있다. 이러한 문제점을 해결하기 위해 가변적인 연결 설정 시간을 적용하여 허용 시간을 초과한 채널 요구 트래픽의 경우도 채널 설정을 제공함으로써 추가적인 트래픽 서비스를 제공할 수 있다. 따라서 본 논문에서는 네트워크 상황 변화에 따른 가변적인 연결 설정 지연시간 파라미터를 사용하는 GLSP (Generalized Label Switch Path) 경로 설정 알고리즘을 제안하였다. 알고리즘은 획일화된 백본 네트워크의 설정 확률 값을 향상시킬 수 있는 장점을 가지고 있다.

• 한국경영과학회지
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• 제27권2호
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• pp.111-121
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• 2002

In this paper, we analyze an M$^{x}$ /G/1 with three types of vacation periods including setup time. Three types of vacations are : N-policy, single vacation, and multiple vacation. We consider compound poisson arrival process and general service time, where the server starts his service when a setup is completed. We find the PGF of the number of customers in system and LST of waiting time, with welch we obtain their means. A decomposition property for the system sloe and waiting time is described also.

• 한국멀티미디어학회논문지
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• 제1권2호
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• pp.249-255
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• 1998

본 논문은 차세대 지능망(AIN Advanced Intelligent Network) 플랫폼 기반의 종합개인통신(UPT:Universal Personal Telecommunications)의 성능에 미치는 CST (Call Setup Time)의 효과를 분석하며 CST 는 파라미터로 사용된다- 차세대 지능망올 기반으로 하는 UPT구현에 있어, VLR(Visitor Location Register) 의 위치가 망의 성능에 많은 영향을 준다. VLR의 최적의 위치를 제시하기 위해, VLR이 위치할 수 있는 3가지 툴리적 구조 : SSP(Service Switching Point)에 근접해 있는 경우, CSC(Cell Site Controller)에 근접해 있는 경우 그리 고 SCP(Service Control Point)에 위 치 하는 경우를 고려 하고 UPT망에서 의 각 구간별 시 간지 연 모델을 제안하고 비교한다. 네트워크의 성능은 No.7 신호망에서 STP수와 SSP, STP(Signaling, Transfer P Point), SCP, VLR의 가용율 $\rho$ 올 변화 시키면서 망 성능을 분석하여 VLR의 최적위치를 제안한다.

• 산업공학
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• 제13권2호
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• pp.195-203
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• 2000

This paper considers the problem of sequencing printed circuit boards(PCBs) on an automatic surface mount device(SMD) placement machine in order to minimize total setup time. Since the total set of component feeders needed by all boards cannot be loaded simultaneously on the magazine, the setup must be made between two successive boards in the sequence. It is assumed that the setup time depends on the number of component feeders to be replaced in the magazine. An important characteristic is that each feeder occupies a different number of slots in the magazine. This problem is equivalent to travelling salesman problem(TSP) except that the distances between two cities, that is, the setup times between two boards, are not known in advance. So, TSP-based heuristics with new distance functions are presented and their performances are compared through various test problems. Computational results indicate that our heuristics outperform existing methods.