• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.808-811
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• 1996

A mathematical model was developed for the simulation of a Pressure Swing Adsorption process with dehydrogenation reaction. The minimum number of beds and optimum operating sequence were determined using MINLP under the given operating conditions. Based on these results, we estimated the minimum annual cost.

• 대한산업공학회지
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• 제15권2호
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• pp.1-10
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• 1989

This paper deals with a single-facility multiproduction model concerning the basic cyclic scheduling. The aim is to obtain the production order of each product in a cycle and the cycle frequency for minimizing the setup costs and inventory carrying costs of all products. The problem is formulated by LP and it shows that the optimal solution derived dominates the solution of non-cyclic scheduling model on some conditions.

• 한국시뮬레이션학회논문지
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• 제11권4호
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• pp.57-68
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• 2002

The analysis of the cyclic scheduling problem in FMS using the transitive matrix has been proposed. Since the transitive matrix may explain all the relations between the places and transitions, we propose an algorithm to get good solution after slicing off some subnets from the original net based on machines operations. For analyzing the schedule problem, we considered two time functions such as produce time and waiting time using the P-invariant. In addition, we are shown the effectiveness of proposed algorithm after comparing with unfolding algorithms.

• 한국통신학회논문지
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• 제33권3A호
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• pp.248-255
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• 2008

OFDMA 시스템에서 주파수축에서의 다중사용자 스케줄링의 성능은 채널의 주파수 선택적 특성과 상관이 있다. 채널이 주파수축에서 평탄하면 다중사용자 스케줄링의 이득이 줄어들 수 있으며 반대로 주파수 선택적 특성이 너무 커서 할당 대역폭 내에서 채널의 변화가 심하게 일어난다면 충분한 스케줄링 이득을 얻기 어려워진다. 다중 사용자 스케줄링 이득을 최대화하기 위해서는 순환지연 다이버시티를 적용하여 채널의 주파수 선택적 특성을 조절할 수 있다. 이 논문에서는 할당 대역폭과 채널 특성을 고려하여 순환지연 다이버시티를 적용할 때의 최적의 지연값을 결정하는 방법을 제안한다.

• 한국통신학회논문지
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• 제38A권4호
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• pp.325-336
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• 2013

대표적인 D2D (Device-to-Device) 통신 시스템 중 하나인 Qualcomm사의 FlashLinQ 시스템에서는 링크 스케줄링 과정을 낮은 복잡도로 실현할 수 있도록 하기 위해 단일-톤 (single-tone) 신호를 이용한 우선순위 및 SIR (Signal-to-Interference power Ratio) 기반의 링크 스케줄링 기법을 수행한다. 하지만 다중 경로 채널 환경에서는 주파수 선택적 페이딩의 영향으로 단일-톤 위치에서와 실제 데이터가 전송되는 전체 대역에서의 수신 전력 간 오차가 발생할 수 있으며, 이는 공평성 측면에서 문제가 될 뿐만 아니라 셀 전체 전송률 상의 손실을 일으킬 수 있다. 따라서, 본 논문에서는 이러한 문제를 해결하기 위해 CAZAC (Constant Amplitude Zero Auto-Correlation) 시퀀스의 상관 특성을 이용해 전체 대역에 대한 SIR 에 가까운 값을 획득할 수 있는 링크 스케줄링 기법을 제안한다. 제안 기법은 전체 대역을 다수의 sub-block 으로 구분하고 각 sub-block 마다 링크의 우선순위에 해당하는 순환 오프셋 (cyclic offset) 을 적용한 CAZAC 시퀀스를 전 대역에 걸쳐 전송하여, 수신 신호와 참조 신호간의 순환 상호 상관 연산 (cyclic cross-correlation)을 통해 전체 대역에 대한 SIR 에 근접한 값을 획득할 수 있다.

• 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.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2000년도 추계학술대회 및 정기총회
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• pp.161-164
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• 2000

A cyclic shop is a production system that repeatedly produces identical sets of jobs, called minimal part sets, in the same loading and processing sequence. We consider a version of cyclic shop where the operations are processed and unloaded within time limits, so called a time window. We model the shop using an event graph model, a class of Petri nets. To represent the time window constraint, we introduce places with negative time delays. From the shop modeling graph, we develop a linear system model based on the max- plus algebra and characterize the conditions on the existence of a stable schedule.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.1250-1255
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• 1990

This paper discusses an optimal cyclic scheduling problem for a FMC (Flexible Manufacturing Cell) modeled by a two-machine flowshop with two machining centers with APC's (Automated Pallet Changers), an AGV (Automated Guided Vehicle) and loading and unloading stations. Cyclic production in which similar patterns of production is repeated can significantly reduce the production lead-time and WIP (Work-In-Process) in such flexible, automated system. Thus we want to find an optimal cyclic schedule that minimizes the cycle time in each cycle. However, the existence of APC's as buffer storage for WIP makes the problem intractable (i.e., NP-complete). We propose an practical approximation algorithm that minimizes, instead of each cycle time, its upper bound. Performances of this algorithm are validated by the way of computer simulations.

• 한국산업정보학회논문지
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• 제1권1호
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• pp.29-62
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• 1996

In this paper, the problem of determining cyclic schedules for a material handling hoist in the printed-circuit-board(PCB) electroplating line is considered. The objective of this research is to determine an optimal simple-cycle schedule of the hoist which in turn maximizes the line throughput rate. Previous approaches to the cyclic hoist scheduling problem are all mathematical programming-based approaches to develop cyclic schedules(Mixed Integer Programming, Linear Programming based Branch and Bound, Branch and Bound Search Method and so on). In this paper, a genetic algorithm-based approach for a single hoist scheduling in the PCB electroplating line is described. Through some experiments for the well known example data and randomly generated data, the proposed algorithm is shown to be more efficient than the previous mathematical programming-based algorithm.

• 제어로봇시스템학회논문지
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• 제7권4호
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• pp.344-350
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• 2001

In this paper, we are focused on the analysis of acyclic schedule for the determination of the opti-mal cycle time and minimization of work in process. Especially, this paper deals with the product ratio-driven cyclic scheduling problem in FMS with different products and ratio using the TPN(Time Petri Nets)un-folding.