• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권9호
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• pp.4301-4319
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• 2017

Adopting mobile chargers (MC) in rechargeable wireless sensors network (R-WSN) to recharge sensors can increase network efficiency (e.g., reduce MC travel distance per tour, reduce MC effort, and prolong WSN lifetime). In this study, we propose a mechanism to split the sensing field into partitions that may be equally spaced but differ in distance to the base station. Moreover, we focus on minimizing the MC effort by providing a new charging mechanism called the sector-based charging schedule (SBCS), which works to dispatch the MC in charging trips to the sector that sends many charging requests and suggesting an efficient sensor-charging algorithm. Specifically, we first utilize the high ability of the BS to divide the R-WSN field into sectors then it select the cluster head for each sector to reduce the intra-node communication. Second, we formulate the charging productivity as NP-hard problem and then conduct experimental simulations to evaluate the performance of the proposed mechanism. An extensive comparison is performed with other mechanisms. Experimental results demonstrate that the SBCS mechanism can prolong the lifetime of R-WSNs by increasing the charging productivity about 20% and reducing the MC effort by about 30%.

• 한국통신학회논문지
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• 제16권11호
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• pp.1167-1178
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• 1991

전투지역 환경의 특징을 조사하고 요구되는 네트워크 성질을 고려하여 그 성질에 적합한 네트워크 제어구조를 설계한다. 또한 네트워크의 제어구조를 구성하며 제어구조에서 형성된 근간 네트워크에서의 전송계획을 작성하기 위한 분산 제어 알고리즘을 설계한다. 전투지역에서 변화하는 네트워크의 연결성 유사와 노드의 파괴로 인한 네트워크의 즉각적인 재구성을 신뢰성 있게 하기 위한 분산 알고리즘과 또한 공통 채널을 이용하는 네트워크에서 노드간에 전송충돌이 없는 전송 계획은 작성하기 위한 분산 알고리즘을 제안한다. 특히 중요한 노드가 파괴 및 사라질 때 되도록 적은 지연을 통해 네트워크가 동작할 수 있는 방법을 제안한다. 그리고 제안된 분신 알고리즘을 시뮬레이션을 통해 검증하고 네트워크 동작에 관해 설명한다.

• Journal of Communications and Networks
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• 제12권3호
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• pp.266-274
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• 2010

The efficient network resource management is one of the important topics in a real-time system. In this paper, we present a practical network resource management framework, control-theoretic packet scheduler (CPS) system. Using our framework, an operating system can schedule both input and output streams accurately and efficiently. Our framework adopts very portable feedback control theory for efficiency and accuracy. The CPS system is able to operate independent of the internal network protocol state, and it is designed to schedule packet streams in fine-grained time intervals to meet the resource requirement. This approach simplifies the design of the CPS system, and leads us to obtain the intended output bandwidth. We implemented our prototype system in Linux, and measured the performance of the network resource management system under various network QoS constraints. The distinctive features of our principles are as follows: It is robust and accurate, and its operation is independent of internal network protocols.

• 산업경영시스템학회지
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• 제39권1호
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• pp.9-16
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• 2016

The project schedule risk in the engineering and facility construction industry is increasingly considered as important management factor because the risks in terms of schedule or deadline may significantly affect the project cost. Especially, the project-based operating companies attempt to find the best estimate of the project completion time for use at their proposals, and therefore, usually have much interest in accurate estimation of the duration of the projects. In general, the management of projects schedule risk is achieved by modeling project schedule with PERT/CPM techniques, and then performing risk assessment with simulation such as Monte-Carlo simulation method. However, since these approaches require the accumulated executional data, which are not usually available in project-based operating company, and, further, they cannot reflect various schedule constraints, which usually are met during the project execution, the project managers have difficulty in preparing for the project risks in advance of their occurrence in the project execution. As these constraints may affect time and cost which role as the crucial evaluation factors to the quality of the project result, they must be identified and described in advance of their occurrence in the project management. This paper proposes a Bayesian Net based methodology for estimating project schedule risk by identifying and enforcing the project risks and its response plan which may occur in storage tank engineering and construction project environment. First, we translated the schedule network with the project risks and its response plan into Bayesian Net. Second, we analyzed the integrated Bayesian Net and suggested an estimate of project schedule risk with simulation approach. Finally, we applied our approach to a storage tank construction project to validate its feasibility.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1996년도 춘계공동학술대회논문집; 공군사관학교, 청주; 26-27 Apr. 1996
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• pp.213-216
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• 1996

R'||'&'||'D project management is a process of decisions concerned with the achievement of goals of objectives. Especially, defense R'||'&'||'D project planning is the key in the successfull management of defense development. The defense project managers are constantly having to perform "what if\ulcorner" exercise, such as what if the project is extended out for an additional cost\ulcorner In this reserch, we developed a schedule-cost analysis model based upon Critical Path Method(CPM) and Venture Evaluation and Review Technique(VERT) for schedule-cost trade off analysis defense R'||'&'||'D projects. In the first step, a deterministic model is developed as a heuristic which deterministic model is developed as a heuristic which determines the schedule extension and reduction cost as a function desired schedule. In the second step, a stochastic network simulation model is developed to analyse the project risk (sucess and failure). The expected time and cost can be determined for desired schedule under the assumptions of stochastic arc data (time and cost) with a various precedence relationships. This model provides the defense R'||'&'||'D managers with an estimated and expected cost for curtailing or extending a project a given amount of time. The effectiveness and efficiency of the proposed methods, a heuristic and stochastic networks simulations, have been demonstrated through examples.

• 예술인문사회 융합 멀티미디어 논문지
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• 제6권3호
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• pp.413-422
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• 2016

공사관리자는 가용자원을 최대한 합리적으로 사용하고 주어진 공사기간과 예산 범위 내에서 건설 프로젝트를 완료하기 위해 노력하며, 공사기간 내에 프로젝트를 끝내기 위해 바차트나 CPM과 같은 공정표를 활용한다. 제주지역의 소규모 건설회사나 현장에서는 건설공사를 수행하기 위한 도구로 공정관리 전문 소프트웨어보다는 엑셀을 많이 사용하는 것으로 조사되었다. 이는 엑셀이 원가와 연계하여 사용하기 편리하고 공정관리 소프트웨어를 활용할 전문가도 부족하기 때문이다. 대학은 지역의 중소규모 건설회사가 요구하는 공정관리 능력을 가진 인재를 배출하고 있지만 교육의 질적 및 양적 측면에서 다소 부족하다. 지방 국립대 건축공학의 교육과정 조사에 의하면 대부분의 학과는 공정관리과목이나 유사한 과목을 편성하고 있다. 주요 교육내용은 네트웍 공정관리기법에 대한 이해와 공정표 작성으로 이루어져 있다. 공정관리 소프트웨어에 대한 교육과 실습은 일부 대학에서만 이루어지고 있으므로 중소규모 건설현장의 공정관리 전문가를 양성하기 위해서는 바차트 활용과 전문 공정관리 소프트웨어 교육도 필요하다.

• Journal of Construction Engineering and Project Management
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• 제3권2호
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• pp.21-34
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• 2013

Various risk factors affect construction projects. Due to the uncertainties created by risk factors, actual activity durations frequently deviate from the estimated durations in either favorable or adverse direction. For this reason, evaluation of schedule uncertainty is required to make decisions accurately when managing construction projects. In this regard, this paper presents a new computer simulation model - the Repetitive Schedule Risk Analysis Model (RSRAM) - to evaluate unit-based repetitive building project schedules under uncertainty when activity durations and risk factors are correlated. The proposed model utilizes Monte Carlo Simulation and a Critical Path Method based repetitive scheduling procedure. This new procedure concurrently provides the utilization of resources without interruption and the maintenance of network logic through successive units. Furthermore, it enables assigning variable production rates to the activities from one unit to another and any kind of relationship type with or without lag time. Details of the model are described and an example application is presented. The findings show that the model produces realistic results regarding the extent of uncertainty inherent in the schedule.

• 한국건설관리학회논문집
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• 제12권1호
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• pp.23-32
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• 2011

국내 일부 건설사는 초고층 건축공사와 같이 반복 공종이 많은 건축물에 일종의 선형 공정계획인 택트 공정계획을 수립하고 수행하고 있다. 선형 공정계획 모델(Linear Scheduling Model: LSM)은 작업 공간과 시간의 정보를 제공하는 시각적 도구로써 연구가 되어왔다. CPM 네트워크 공정표의 구속조건(종료 후 종료, 시작 후 종료, 종료 후 시작, 시작 후 시작)과 마찬가지로 선형계획모델 또한 작업간의 관계간의 구속조건이 발생한다. 특히, 네트워크 공정표를 호환하기 위하여 작업간의 중요 속성간의 관계성의 경계 조건을 정의하는 것이 필요하다. 따라서 본 연구는 선형 공정계획을 수립 시 발생하는 액티비티간의 공간상의 경계조건을 분석한다. 또한 선형 공정계획의 액티비티 간의 관계성을 고려하여 현재 일부 건설회사를 중심으로 사용하고 있는 택트 공정계획에 제안한 경계조건을 반영하여 택트 공정계획 수립과 관리를 위해 고려해야 하는 주요 사항을 제시하는 것이 본 연구의 목적이다.

• 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.

• 한국산학기술학회논문지
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• 제9권3호
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• pp.757-764
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• 2008

효율적인 공정이행관리를 통해서 건설공사 일정의 불필요한 공기지연을 사전에 예방하고, 나아가 품질확보를 위하여 각 공정의 내용을 정확하게 숙지하고 관리하는 일이 중요하다. 더욱 중요한 것은 공사계획에 따른 공정이 원활하게 진행될 수 있도록 각각의 공정에 필요한 선행작업들을 체계화하여 관리하는 것이다. 이를 위하여 본 연구에서는 아파트공사를 대상으로 이정표 중심, 작업공종 중심, 활동 중심, 작업 담당자 중심으로 구분하여 선행작업관리 시안을 제시하였다.