• 산업경영시스템학회지
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• 제30권2호
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• pp.44-50
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• 2007

This paper deals with the problem of scheduling jobs and rate-modifying activities on parallel machines. A rate-modifying activity is an activity that changes the production rate of equipment such as maintenance and readjustment. If a job is scheduled after the rate-modifying activity, then the processing time varies depending on the modifying rate of the activity. In this study, we extend the single machine problem to parallel machines problem and propose algorithms is to schedule the rate-modifying activities and jobs to minimize the makespan on parallel machines which is NP-hard. We propose a branch and bound algorithm with three lower bounds to solve medium size problems optimally. Also we develop three heuristics, Modified Longest Processing Time, Modified MULTIFIT and Modified COMBINE algorithms to solve large size problems. The test results show that branch and bound algorithm finds the optimal solution in a reasonable time for medium size problems (up to 15 jobs and 5 machines). For large size problem, Modified COMBINE and Modified MULTIFIT algorithms outperform Modified LPT algorithm in terms of solution quality.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 추계학술대회 논문집
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• pp.46-53
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• 1999

As of July 1999, i,185 lomocotives(excluding metropolitan area electric locomotives) are in Korean National Railroad(KNR). With this limited number of resources assigning locomotives to each trains of timetable is very important in the entire railway management point of view because schedule can be regarded as goods in transportation industry. On a simple rail network, it is rather easier to assign proper locomotives to trains with the experience of operating experts and get optimal assignment solution. However, as the network is getting bigger and complicated, the number of trains and corresponding locomotives will be dramatically increased to rover all the demands required to service all of the trains in timetable. There will be also numerous operational constraints to be considered. Assigning proper locomotives to trains and building optimal cyclic rotations of locomotive routings will result in increasing efficiency of schedule and giving a guarantee of more profit. The purpose of this study is two fold: (1) we consider a planning-level locomotive scheduling problem with the objective of minimizing the wasting cost under various practical constraints and (2) development of implementation prototype program of its assigning result. Not like other countries, i.e. Canada, Sweden, Korean railroad operates on n daily schedule basis. The objective is to find optimal assignment of locomotives of different types to each trains, which minimize the wasting cost. This problem is defined on a planning stage and therefore, does not consider operational constraints such as maintenance and emergency cases. Due to the large scale of the problem size and complexity, we approach with heuristic methods and column generation to find optimal solution. The locomotive scheduling prototype consists of several modules including database, optimization engine and diagram generator. The optimization engine solves MIP model and provides an optimal locomotive schedule using specified optimization algorithms. A cyclic locomotive route diagram can be generated using this optimal schedule through the diagram generator.

• 한국농공학회지
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• 제35권1호
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• pp.67-75
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• 1993

This study is to analyze both root growth and soil moisture extraction pattern during the growing period of upland crops with respect to soybean, redpepper, sesame. Field and lysimeter tests were conducted under 12 treatments of soil moisture level by the San Cristobal experimental design(1981) and 3 soil type(sand, sandy loam, silty loam) for 4 years('87-'90) at the experimental plot of Rural Development Administration located in Suwon. The results of this study are summarized as follows : 1.For soybean, redpepper and sesame, root growth in dry soil was better than that in wet soil and it could be expressed as a sin function in terms of time. Maximum root depth was about 55cm, 44cm, 40cm respectively. 2.The average soil moisture extraction pattern for soybean, redpepper and sesame were 61.4%, 62.8%, 79.5% for zone l(0-l5cm). 25.5%, 27.1%, 18.3%, for zone 2(15-30cm).11.4%, 9.8%, 2.3% for zone 3(30-45cm), 1.7%, 0.3%, 0.04% for zone 4(45-60cm) respectively. This means that Zone 1 would be the dominant zone in irrigation scheduling. 3.With respect to soybean, the soil moisture extraction pattern(SMEP) was varied somewhat according to the erent maintenance of soil moisture level. The average SMEP for high maintenance of soil moisture was 46%, 29%, 17%, 8%, for middle maintenance of soil moisture was 43%, 29%, 17%, 11 % and for low maintenance of soil moisture was 40%, 28%, 20%, 12%, respectively. 4.With respect to soybean, the soil moisture in the upper layer was distinctly consumed more than that in the lower layer for clay loam soil and the soil moisture of all layers was consumed evenly for sand soil. The SMEP for sandy loam soil showed a middle result compared with the above 2 soil types.

• 전자공학회논문지
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• 제54권5호
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• pp.48-61
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• 2017

클라우드 컴퓨팅의 IaaS 서비스는 유지비용 없이 원하는 만큼의 고성능 가상 머신을 사용할 수 있다는 장점 덕분에 대용량 병렬 프로그램을 실행하기 위한 고성능 컴퓨팅 환경으로 주목받고 있다. 이러한 고성능 컴퓨팅 환경에서 병렬 프로그램의 실행에 소요되는 시간은 태스크 스케줄링 알고리즘에 좌우된다. 클라우드 컴퓨팅 환경을 기반으로 하는 태스크 스케줄링 알고리즘에 관한 연구는 사용자 부담 비용을 최소화하는 알고리즘이 주류를 이루었으며, 병렬 프로그램의 실행을 최대한 빨리 끝내기 위한 알고리즘에 관한 연구는 거의 이루어지지 않았다. 본 논문에서는 사용자 부담 비용 등의 제약 없이 병렬 프로그램을 최대한 빨리 끝내기 위한 알고리즘인 HAGD 알고리즘과, HAGD 알고리즘이 사용하는 새로운 성능 향상 기법인 묶음 태스크 복제 기법을 제안한다. 묶음 태스크 복제 기법은 기존 태스크 복제 기법을 단순화하였으며, HAGD 알고리즘은 고성능 컴퓨팅 환경과 병렬 프로그램의 특성에 맞추어 태스크 삽입 기법 혹은 묶음 태스크 복제 기법을 사용한다. 성능 평가 결과, 제안하는 알고리즘이 환경 특성과 관계없이 우수한 표준화한 전체 실행 시간을 제공하는 것을 확인하였다.

• Journal of Information Processing Systems
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• 제6권4호
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• pp.553-562
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• 2010

The core services in cloud computing environment are SaaS (Software as a Service), Paas (Platform as a Service) and IaaS (Infrastructure as a Service). Among these three core services server virtualization belongs to IaaS and is a service technology to reduce the server maintenance expenses. Normally, the primary purpose of sever virtualization is building and maintaining a new well functioning server rather than using several existing servers, and in improving the various system performances. Often times this presents an issue in that there might be a need to increase expenses in order to build a new server. This study intends to use grid service architecture for a form of server virtualization which utilizes the existing servers rather than introducing a new server. More specifically, the proposed system is to enhance system performance and to reduce the corresponding expenses, by adopting a scheduling algorithm among the distributed servers and the constituents for grid computing thereby supporting the server virtualization service. Furthermore, the proposed server virtualization system will minimize power management by adopting the sleep severs, the subsidized servers and the grid infrastructure. The power maintenance expenses for the sleep servers will be lowered by utilizing the ACPI (Advanced Configuration & Power Interface) standards with the purpose of overcoming the limits of server performance.

• Journal of Information Processing Systems
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• 제17권3호
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• pp.473-488
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• 2021

The enterprise resource planning (ERP) system is a standardized and advanced business process that many companies are implementing now-a-days through customization. However, it affects the efficiency of operations as these customizations are based on uniqueness. In this study, we analyzed the impact of customized modules and processing time on customer service request (CSR), by utilizing the stacked CSR data during the construction and operation of ERP, focusing on small and medium-sized enterprises (SMEs). As a result, a positive correlation was found between unit companies and the length of ERP implementation; ERP modules and the length of ERP implementation; ERP modules and unit companies; and the type of ERP implementation and ERP module. In terms of CSR, a comparison of CSR processing time of CBO (customized business object) module and STD (standard) module revealed that while the five modules did not display statistically significant differences, one module demonstrated a statistically very significant difference. In sum, the analysis indicates that the CBO-type CSR and its processing cost are higher than those of STD-type CSR. These results indicate that companies planning to implement an ERP system should consider the ERP module and their customization ratio and level. It not only gives the theoretical validity that should be considered as an indicator for decision making when ERP is constructed, but also its implications on the impact of processing time suggesting that the maintenance costs and project scheduling of ERP software must also be considered. This study is the first to present the degree of impact on the operation and maintenance of customized modules based on actual data and can provide a theoretical basis for applying SW change ratio in the cost estimation of ERP system maintenance.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3236-3240
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• 2007

This paper describes the results of steam turbine performance tests. The objectives of performance test is to exactly evaluate the degradation(decrease in performance) of the coal-fired steam turbine generator in order to provide plant information to help performance engineers identify problems, improve performance, and make economic decisions about scheduling maintenance and optimizing operation. To achieve these goals, the periodic thermal performance tests have been carried out since the initial operation period, 1997. We made the calculation program and guidelines for the tests and developed the performance index of the turbine cycle on the basis of the ASME PTC. By comparing the performance changes throughout the whole operation period, we confirmed the performance reliabilities of the turbine and its conditions.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1205-1210
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• 2004

The 4-20mA analog signal used in the various industrial fields to interface sensor in distributed process control has been replaced with relatively simple digital networks, called "fieldbus, and recently by Ethernet. Significant advances in Internet and computer technology have made it possible to develop an Internet based control, monitoring, and operation scheduling system for heating, ventilation and air-conditioning (HVAC) systems. The seamless integration of data networks with control networks allows access to any control point from anywhere. Field compatible field devices become so-called "smart" devices, capable of executing simple control, diagnostic and maintenance functions and providing bidirectional serial communication to higher level controller. The most important HVAC of BAS has received nationwide attention because of higher portion of more than 40% in building sector energy use and limited resources. This paper presents the Internet-based monitoring and control architecture and development of LonWorks control modules for AHU (air handling units) of HVAC in viewpoint of configuring BAS network. This article addresses issues in architecture section, electronics, embedded processors and software, and internet technologies.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.333-336
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• 1991

In this paper, Hopfield & Tank model-like artificial neural network structure is proposed, which can be used for the optimal path planning problems such as the unit commitment problems or the maintenance scheduling problems which have been solved by the dynamic programming method or the branch and bound method. To construct the structure of the neural network, an energy function is defined, of which the global minimum means the optimal path of the problem. To avoid falling into one of the local minima during the optimization process, the simulated annealing method is applied via making the slope of the sigmoid transfer functions steeper gradually while the process progresses. As a result, computer(IBM 386-AT 34MHz) simulations can finish the optimal unit commitment problem with 10 power units and 24 hour periods (1 hour factor) in 5 minites. Furthermore, if the full parallel neural network hardware is contructed, the optimization time will be reduced remarkably.

• 기술사
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• 제16권1호
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• pp.48-54
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• 1983

Building management cost increases enormously as modern buildings become complicated. Lost of building eveners or managers feel the need to cut down the cost not sacrifying Comfort building environment and building safety, The ways to achieve such goal are maintaing with a few person, proper HVAC scheduling to save energy BAS's i.e the building automation system or building maintenance system, are designed to meet the goal. In korea, imported BAS's have been installed past several years. Difficulties arised in several aspects. One is extra high cost in installing BAS's because of marginal coat. Another is long settling time because it is originated from abroad. GSC/85/30 is the first trial as a korean BAS to minimize such difficulties. Even though it is a primitive system, it is a mileston of korean BAS the technics gained from developing GSCI/85/30 can be utilized to develop higher version and is now. As modern buildings become more complicated and hugy, managers owner of buildings seek for the system to manage building properly. BAS(Building Automation System or Building management system) is designed to meet the need.