• International conference on construction engineering and project management
• /
• 2009.05a
• /
• pp.642-648
• /
• 2009

Determining the total duration for a construction project is an integral part of project management in the construction industry. This is to ensure the project and all its associated activities can be carried out and completed within the time frame stipulated. There are several commonly used scheduling methods and techniques in project management, some of which involves manual calculation while others involve computer software. This paper looks into the various time determination methods, extracting out their differences and similarities. It also seeks to draw out the problems when determining time for projects, especially those encountered of case studies. Based on the results from the case studies, there were delays on certain projects even though time determination had been carried out rigorously prior to the commencement of the projects. This paper seeks to develop a time determination model, which incorporates risk management techniques into the calculations in order to improve the method for time estimation to minimize the chances of project delay.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2009.11a
• /
• pp.931-932
• /
• 2009

개인용 비디오 녹화기는 하나의 채널을 통해 수신된 스트림에 대해서만 재생 또는 하드 디스크에 저장할 수 있도록 구성되어, 다른 채널을 시청하면서 특정 채널의 방송을 저장할 수 없거나 2개의 튜너와 복조기를 탑재하여 녹화를 하면서 다른 실시간 방송을 시청할 수는 있으나 전자 프로그램 가이드를 이용하여 개인용 방송 편성을 구현하는데 어려움이 있었다. 본 논문에서는 종래 기술의 제반 단점과 문제점을 해결하기 위한 것으로, 개인용 비디오 녹화기의 기본 어플리케이션의 하나인 전자프로그램 가이드에서 현재 녹화되고 있는 채널 이외의 방송을 시청할 수 있도록 멀티 복조기를 탑재한 개인용 비디오 녹화기를 이용한 방송 편성 방법을 제안한다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2009.11a
• /
• pp.59-60
• /
• 2009

기존의 임베디드 시스템 환경에서는 대용량의 미디어 컨텐츠를 재생하고, 사용자 이벤트를 받아 실시간으로 처리하는데에 제한된 리소스로 인해 한계점이 있었다. 압축률이 좋고, 전송 및 재생에 효과적인 MPEG-4 시스템의 표준을 따르면서 제한된 리소스에서 사용자와의 인터렉션이 가능한 멀티미디어를 디스플레이할 수 있는 효율적인 기법이 요구된다. 임베디드 시스템의 MPEG-4 장면 랜더링에서 사용자 이벤트 처리를 위해 불필요한 노드 파싱을 제거하고 이벤트 처리 절차를 간략히 함으로써 효율적인 객체 교체와 객체 속성 변환 방법을 제안한다.

• International conference on construction engineering and project management
• /
• 2005.10a
• /
• pp.791-795
• /
• 2005

A simulation model is proposed to evaluate the effect of correlations between activity durations on the overall project duration. The proposed model incorporates NORTA, a recent developed statistical method, into the simulation process to allow arbitrarily specified marginal distributions for activity durations and any desired correlation structure. The generality is of practical value when systematic data is not available and planners have to rely on arbitrary experts' estimation, which may involve a mixed situation when some activity durations are continuously distributed whereas others are discrete outcomes. The proposed model is validated by showing that the correlation coefficients of the simulation results are close to the originally specified ones. The simulation results are compared to two conventional approaches: PERT and simulation without correlation. The comparisons illustrate that the proposed model can provide important management information, which would otherwise be distorted due to the neglect of the correlations between activity durations.

• ETRI Journal
• /
• v.45 no.4
• /
• pp.627-635
• /
• 2023

In vehicular edge computing (VEC) networks, the rapid expansion of intelligent transportation and the corresponding enormous numbers of tasks bring stringent requirements on timely task offloading. However, many tasks typically appear within a short period rather than arriving simultaneously, which makes it difficult to realize effective and efficient resource scheduling. In addition, some key information about tasks could be learned due to the regular data collection and uploading processes of sensors, which may contribute to developing effective offloading strategies. Thus, in this paper, we propose a model that considers the deterministic demand of multiple tasks. It is possible to generate effective resource reservations or early preparation decisions in offloading strategies if some feature information of the deterministic demand can be obtained in advance. We formulate our scenario as a 0-1 programming problem to minimize the average delay of tasks and transform it into a convex form. Finally, we proposed an efficient optimal offloading algorithm that uses the interior point method. Simulation results demonstrate that the proposed algorithm has great advantages in optimizing offloading utility.

• International conference on construction engineering and project management
• /
• 2011.02a
• /
• pp.575-581
• /
• 2011

A novel approach for analysis of criticality with respect to path and to activity in networks with fuzzy activity durations is proposed. After recalling the Yager ranking method, the relative degree of criticality of activities and paths are defined. An efficient algorithm based on path enumeration to compute the relative degree of criticality of activities and paths in networks with fuzzy durations is proposed. Examples of former researches are employed to validate the proposed approach. The proposed algorithm has been tested on real world project networks and experimental results have shown that the algorithm can calculate the relative degree of criticality of activities and paths in a reasonable time.

• International conference on construction engineering and project management
• /
• 2011.02a
• /
• pp.201-208
• /
• 2011

Today's highly competitive construction scenario forces all the major players in the field to take up multiple projects which have put an undue pressure on the resources available within the organization. Under such a situation, there are many instances where in the resource requirement exceeds its availability due to multiple activities (with same resource requirement) which are scheduled to start simultaneously and thus results in the constrained resource becoming a bottleneck of the project. As a consequence of sharing resources, this paper studies the impact on the completion date of two similar projects under two different conditions, the first one resulting in a postponed end date and the second without any postponement. The resource utilization, the possibility of substitution of a resource and its subsequent impact on the deadline of the project is analyzed under these two circumstances. The study is done on a Critical Chain Project Management (CCPM) platform instead of leaving the schedule with a traditional Critical Path Method (CPM) finish, which gives an added advantage of validating the robustness of the emerging CCPM trend in the field of resource management.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2007.11a
• /
• pp.678-681
• /
• 2007

분산형 데스크탑 그리드 시스템에서 안정적인 연산 수행을 위한 노드 구성 기법과 동적인 환경에 적응적인 스케줄링 기법은 필수 요소이다. 그러나 기존 연구에서는 자원 제공자의 휘발성에 적응적으로 대처하지 못하는 연산 수행 모델을 사용하였기 때문에 데드라인 내에 전체 작업을 완료해야하는 응용에 대처하지 못하는 문제점이 발생한다. 이에 본 논문에서는 자원제공자의 성능과 논리적인 위치기반으로 자가 조직적 연산 오버레이 네트워크(Computation Overlay Network) 구성 기법과 자원제공자의 작업 완료 확률과 신용도 값을 이용하여 응용 QoS 보장을 위한 휴리스틱기반 복제 (Heuristic based Replication) 기법을 제안한다. 성능평가에서는 기존 스케줄링 기법과 자원제공자의 작업 완료 확률과 신용도에 따른 분포를 이용한 복제기반 스케줄링 기법을 비교평가 한다.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.38 no.4
• /
• pp.159-167
• /
• 2015

We consider a wafer lot transfer/release planning problem from semiconductor wafer fabrication facilities to probing facilities with the objective of minimizing the deviation of workload and total tardiness of customers' orders. Due to the complexity of the considered problem, we propose a two-level hierarchical production planning method for the lot transfer problem between two parallel facilities to obtain an executable production plan and schedule. In the higher level, the solution for the reduced mathematical model with Lagrangian relaxation method can be regarded as a coarse good lot transfer/release plan with daily time bucket, and discrete-event simulation is performed to obtain detailed lot processing schedules at the machines with a priority-rule-based scheduling method and the lot transfer/release plan is evaluated in the lower level. To evaluate the performance of the suggested planning method, we provide computational tests on the problems obtained from a set of real data and additional test scenarios in which the several levels of variations are added in the customers' demands. Results of computational tests showed that the proposed lot transfer/planning architecture generates executable plans within acceptable computational time in the real factories and the total tardiness of orders can be reduced more effectively by using more sophisticated lot transfer methods, such as considering the due date and ready times of lots associated the same order with the mathematical formulation. The proposed method may be implemented for the problem of job assignment in back-end process such as the assignment of chips to be tested from assembly facilities to final test facilities. Also, the proposed method can be improved by considering the sequence dependent setup in the probing facilities.

• IEMEK Journal of Embedded Systems and Applications
• /
• v.9 no.5
• /
• pp.253-260
• /
• 2014

European Space Agency has recognized Integrated Modular Avionics and ARINC specification 653 as avionics computer system for space application. Integrated Modular Avionics specification reduces the space by integrating a system composed of many electronic devices into a computer. recent researches have been studying how to apply the ARINC 653 into an open source operating system, such as Linux. These studies have concentrated on partition scheduling for time separation. However, requirements to guarantee spatial separation should be further analyzed to ensure deterministic execution time. Therefore, memory management is needed to verify spatial isolation on Linux systems. This research proposes a new method to accomplish spatial isolation for the ARINC 653 specification in Linux. We have added new data structures and system calls to handle functionalities for spatial separation. They are used during the partition startup process. The proposed method was evaluated on the LEON4 processor, which is the next generation microprocessor to be used in the future space missions. All implementations confirm that spatial isolation of the ARINC 653 specification was accomplished.