자동차용 부품 제조회사의 생산관리용 전산시스템 개발

주운기,윤철호 선문대학교 중소기업기술지원연구소 2001 선문공대 연구/기술 논문집 Vol.6 No.1

자동차용 부품을 생산하는 중소기업체에서 회사내 업무 전산화를 위해 활용할 수 있는 전산시스템을 개발하였다. 자동차용 부품 생산은 주로 이산(discrete) 생산이고 주문(order) 생산품이 많으므로, 제품 및 부품에 대한 관리를 수작업으로 하기는 어렵다. 따라서, 전산시스템을 이용한 관리가 필요한데, 본 연구개발에서는 현재의 업무 처리 방식, 생산 환경, 전산망의 상황 등을 고려하여 기존 시스템의 문제점들을 해결하고 개선한 전산시스템을 개발하였다. The objective of the study is in development of a software for a small and medium company. Our software will be utilized to improve the planning and control process in discrete and order production environment. Most of companies have at least one software for the production planning and control. By the way, there exist few companies having a software of good fitness of the company. This study develops a new software to have good fitness for the company I by modifying and improving the existing one of the company.

A CAPACITY EXPANSION STRATEGY ON PROJECT PLANNING

Joo, Un-Gi Electronics and Telecommunications Research Instit 1994 ETRI Journal Vol.15 No.3

A capacity expansion planning problem with buy-or-lease decisions is considered. Demands for capacity are deterministic and are given period-dependently at each period. Capacity additions occur by buying or leasing a capacity, and leased capacity at any period is reconverted to original source after a fixed length of periods, say, lease period. All cost functions (buying, leasing and idle costs) are assumed to be concave. And shortages of capacity and disposals are not considered. The properties of an optimal solution are characterized. This is then used in a tree search algorithm for the optimal solution and other two algorithms for a near-optimal solution are added. And these algorithms are illustrated with numerical examples.

Channel Reallocation Methodologles for Restorable Transmission Networks

Un Gi Joo 한국경영과학회 2003 Management Science and Financial Engineering Vol.9 No.1

This paper develops channel reallocation methodologies for survival transmission networks. Any failure on a high-speed telecommunication network needs to restored rapidly and a channel real-location methodology has an important role for the fast restoration. This paper considers the channel reallocation problems under a line restoration with distributed control, where the line restoration restores the failed channels by rerouting the channels along the two alternative routes. The objective is to determine the optimal number of rerouting channels on the alternative rerouting paths of a given transmission network, where the optimality criteria are the first the last and the mean restoration times. For each criterion, the problem is formulated as a mixed integer programming and the optimal channel relocation algorithm is suggested based upon the characterization of the optimal solution.

Batching Decisions to Minimize Weighted Mean Flow Time on a Single Facility with Batch Size Restrictions

Joo, Un-Gi 선문대학교 중소기업기술지원연구소 2001 선문공대 연구/기술 논문집 Vol.6 No.1

단일설비를 이용하여 여러 개의 작업을 처리하는 경우, 한 번에 작업을 하는 작업(배치) 크기에 제한이 있는 경우가 많다. 더구나, 이러한 하나의 배치를 구성하는 작업의 개수는 정수(integer) 개로 구성이 되는 경우가 많은데, 본 논문에서는 단일 설비를 이용하여 정수개의 작업으로 한 배치를 구성하는 경우에 있어서의 총 흐름시간을 최소화하는 배칭 및 일정계획 수립문제를 다룬다. 먼저, 상하한 값의 배치 크기 관계에 따라 실행 가능해가 존재하기 위한 조건을 규명하고, 이 조건이 만족되는 경우에 대한 분석을 수행하였다. 이 분석 결과를 이용하여 최선의 일정계획을 수립하는데 이용할 수 있는 배칭 절차와 일정계획 수립 방안을 제시한다. This paper considers a batching decision on a single facility for a set of multi-type jobs where the batch size of each type is restricted on its lower and upper bound and to be integral value. The batching for the required total jobs implies that the job set is splitted into several lots where the major and minor setup times are involved for processing each lot. The objective is to find the optimal batching and sequencing of the batches so as to minimize weighted mean flow time. The flow time of each job is measured in "item-flow" concept under a derived feasibility condition. The optimal batching is characterized for the problem, upon which a simple sequencing algorithm is exploited for the resulted batches.

Scheduling Algorithms for the Maximal Total Revenue on a Single Processor with Starting Time Penalty

Un Gi Joo 한국경영과학회 2012 Management Science and Financial Engineering Vol.18 No.1

This paper considers a revenue maximization problem on a single processor. Each job is identified as its processing time, initial reward, reward decreasing rate, and preferred start time. If the processor starts a job at time zero, revenue of the job is its initial reward. However, the revenue decreases linearly with the reward decreasing rate according to its processing start time till its preferred start time and finally its revenue is zero if it is started the processing after the preferred time. Our objective is to find the optimal sequence which maximizes the total revenue. For the problem, we characterize the optimal solution properties and prove the NP-hardness. Based upon the characterization, we develop a branch-and-bound algorithm for the optimal sequence and suggest five heuristic algorithms for efficient solutions. The numerical tests show that the characterized properties are useful for effective and efficient algorithms.

Bandwidth Allocation and Scheduling Algorithms for Ethernet Passive Optical Networks

Un Gi Joo 한국경영과학회 2010 Management Science and Financial Engineering Vol.16 No.1

This paper considers bandwidth allocation and scheduling problems on Ethernet Passive Optical Networks (EPON). EPON is one of the good candidates for the optical access network. This paper formulates the bandwidth allocation problem as a nonlinear mathematical one and characterizes the optimal bandwidth allocation which maximizes weighted sum of throughput and fairness. Based upon the characterization, two heuristic algorithms are suggested with various numerical tests. The test results show that our algorithms can be used for efficient bandwidth allocation on the EPON. This paper also shows that the WSPT (Weighted Shortest Processing Time) role is optimal for minimization the total delay time in transmitting the traffic of the given allocated bandwidth.

A Constrained Single Machine Scheduling Model with Earliness/Tardiness and Flow Time Measures

Joo, Un Gi,Sung, Chang Sup 한국경영과학회 1995 韓國經營科學會誌 Vol.20 No.1

This paper considers a single machine nonpreemptive scheduling problem with a given common due date. In the problem, the optimal job sequence is sought to minimize the sum of earliness / tardiness and flow time measures in the situation where all jobs are available at time zero, and weights per unit length of earliness / tardiness and flow time are V and W, respectively. Some dominant solution properties are characterized to derive both an optimal starting time for an arbitrary sequence and sequence improvement rules. The optimal schedule is found for the case W≥V. By the way, it is difficult to find the optimal schedule for the case W<V. Therefore, the derived properties are put on together to construct a heuristic solution algorithm for the case W<V, and its effectiveness is rated at the mean relative error of about 3% on randomly generated numerical problems.

A Packet Scheduling for Input-Queued Router with Deadline Constraints

Un Gi Joo,Heyung Sub Lee,Hyeong Ho Lee,Whan Wo Kim 대한전자공학회 2002 ITC-CSCC :International Technical Conference on Ci Vol.2002 No.7

총 준비시간과 처리시간에 따른 학습효과를 고려한 단일설비 일정계획

주운기(Un Gi Joo) 한국경영과학회 2021 한국경영과학회지 Vol.46 No.4

This paper considers the single machine scheduling problems with learning effect on either the setup or processing times, where the setup or processing times decrease according to increasing both the total amount of setups and processing already. Our objective is to find the optimal schedules which minimize makespan, mean flow time, or total absolute differences in completion times (TADC) of the jobs. We characterize the optimal schedules for each scheduling measure and show the optimal scheduling rules to solve the problems with 0(n log n) time. Furthermore, we show that the problems for minimization a weighted sum of makespan and mean flow time are also solved in polynomial-time complexity. The optimal schedules for the bi-criteria are useful for the various environments by fitting the weight of each criterion, makespan and mean flow time, on the aim of the scheduling in the environments.

기대 평균흐름시간 최소화를 위한 단일설비 일정계획의 성능변동 분석

주운기(Un Gi Joo) 한국경영과학회 2016 韓國經營科學會誌 Vol.41 No.1

A single machine scheduling problem for jobs with stochastic processing time is considered in this study. Shortest processing time (SPT) sequencing according to the expected processing times of jobs is optimal for schedules with minimal expected mean flow time when all the jobs arrive to be scheduled and their expected processing times are known. However, SPT sequencing according to the expected processing time may not be optimal for the minimization of the mean flow time when the actual processing times of jobs are known. This study evaluates the complexity of SPT sequencing through a comparison of the mean flow times of schedules based on the expected processing times and actual processing times of randomly generated jobs. Evaluation results show that SPT sequencing according to the expected flow time exhibits chaotic variation to the optimal mean flow time. The relative deviation from the optimal mean flow time increases as the number of jobs, processing time, or coefficient of variation increases.