• Journal of the Korea Institute of Building Construction
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• v.21 no.4
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• pp.347-359
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• 2021

Recently, construction projects have emerged in the form of program management, which is complicated by the large-scale of construction, and requires astronomical construction costs. In particular, projects that absolutely require management at the program level, such as large-scale construction projects, require overall control of the planned schedule and cost as a set of various projects, including infrastructure. But in Korea, there is no specific management standard for delays in construction. In order to avoid the risk of cost increase and project delay in the program-level construction project, it is necessary to apply more systematic management standards to prevent delay and to take a more preemptive response in the construction process. Therefore, in this study, a delay management index (DMI) was developed to successfully carry out large-scale construction projects at the program level and prevent delays in advance. In addition, case studies were conducted for large-scale construction projects, and a delay prevention system was established for program-level construction projects.

• Structural Engineering and Mechanics
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• v.59 no.1
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• pp.187-207
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• 2016

Practical ambient excitations of engineering structures usually do not comply with the stationary-white-noise assumption in traditional operational modal analysis methods due to heavy traffic, wind guests, and other disturbances. In order to eliminate spurious modes induced by non-white noise inputs, the improved stochastic subspace identification based on a delay index is proposed in this paper for a representative kind of stationary non-white noise ambient excitations, which have nonzero autocorrelation values near the vertical axis. It relaxes the stationary-white-noise assumption of inputs by avoiding corresponding unqualified elements in the Hankel matrix. Details of the improved stochastic subspace identification algorithms and determination of the delay index are discussed. Numerical simulations on a four-story frame and laboratory vibration experiments on a simply supported beam have demonstrated the accuracy and reliability of the proposed method in eliminating spurious modes under non-white noise ambient excitations.

• Nuclear Engineering and Technology
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• v.47 no.3
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• pp.362-379
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• 2015

In this study, Nuclear Power Plant (NPP) construction schedule delay risk assessment methodology is developed and the construction delay risk is assessed for turnkey international NPP projects. Three levels of delay factors were selected through literature review and discussions with nuclear industry experts. A questionnaire survey was conducted on the basis of an analytic hierarchy process (AHP) and Relative Importance Index (RII) methods and the schedule delay risk is assessed qualitatively and quantitatively by severity and frequency of occurrence of delay factors. This study assigns four main delay factors to the first level: main contractor, utility, regulatory authority, and financial and country factor. The second and the third levels are designed with 12 sub-factors and 32 sub-sub-factors, respectively. This study finds the top five most important sub-sub-factors, which are as follows: policy changes, political instability and public intervention; uncompromising regulatory criteria and licensing documents conflicting with existing regulations; robust design document review procedures; redesign due to errors in design and design changes; and worldwide shortage of qualified and experienced nuclear specific equipment manufacturers. The proposed combined AHP-RII methodology is capable of assessing delay risk effectively and efficiently. Decision makers can apply risk informed decision making to avoid unexpected construction delays of NPPs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.8
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• pp.1257-1264
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• 2017

In video content watching service, when a user requests video content, the content server has to transmit the entire video to the client for watching. This transmission delay increases as the size of video content increases. In order to solve the transmission delay problem, a prefetching technique can be used in which a video content to be watched by a user is predicted and transmitted to a client before the user requests it. In this paper, we propose a prefetching system considering multiple indices for video content. In the proposed method, video content to be prefetched is selected by comprehensively analyzing the order relation index indicating the order of viewing the videos of the users, the similarity index between the video contents, and the popularity index reflecting the viewing frequency of the video content. Experimental results show that the maximum accuracy is achieved when prefetching uses only the order relation index for movie contents.

• International Journal of Highway Engineering
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• v.16 no.5
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• pp.109-119
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• 2014

PURPOSES : The control delay in seconds per vehicle is the most important traffic operational index to evaluate the level of service of signalized intersections. Thus, it is very critical to calculate accurate control delay because it is used as a basic quantitative evidence for decision makings regarding to investments on traffic facilities. The control delay consists of time-in-queue delay, acceleration delay, and deceleration delay so that it is technically difficult to directly measure it from fields. Thus, diverse analysis tools, including CORSIM, SYNCHRO, T7F, VISTRO, etc. have been utilized so far. However, each analysis tool may use a unique methodology in calculating control delays. Therefore, the estimated values of control delays may be different by the selection of an analysis tool, which has provided difficulties to traffic engineers in making solid judgments. METHODS : This study was initiated to verify the feasibility of diverse analysis tools, including HCM methodology, CORSIM, SYNCHRO, T7F, VISTRO, in calculating control delays by comparing estimated control delays with that measured from a field. RESULTS : As a result, the selected tools produced quite different values of control delay. In addition, the control delay value estimated using a calibrated CORSIM model was closest to that measured from the field. CONCLUSIONS : First, through the in-depth experiment, it was explicitly verified that the estimated values of control delay may depend on the selection of an analysis tool. Second, among the diverse tools, the value of control delay estimated using the calibrated microscopic traffic simulation model was most close to that measured from the field. Conclusively, analysts should take into account the variability of control delay values according to the selection of a tool in the case of signalized intersection analysis.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.217-221
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• 2003

This study proposes a new classification system and analysis methodology for time delay risk of apartment projects. And this study proposes the classification of major trades and risk level and risk index by performing expert-oriented interview and survey report on a national scale. The purpose of this study is to present basic data for time delay risk management system through the analysis of risk level, risk index and rank of major 5 trades(earth work, structure work, masonry work, window and door/glass work, and interior finish work) in apartment projects.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.82-86
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• 2015

Construction delay is a common problem worldwide, which is considered as one of the main reasons for project failure. Bangladesh construction industry is no exception. This study investigated the main causes of delay in large building construction projects in Bangladesh. A questionnaire survey was conducted to determine the causes of delay from owners, consultants, and contractors of large building construction projects. About 70 respondents participated in the survey. Using the importance index analysis, the study identified 10 most important causes of delay from a list of 30 different causes. Ten most important causes were: (1) lack of experienced construction manager, (2) lowest bidder selection, (3) funding shortage by owner, (4) lack of proper management, (5) improper planning and scheduling, (6) lack of skilled workers, (7) site constraints, (8) contractors' cash flow problems during construction, (9) escalation of resources price, and (10) contractors' excessive workload. Furthermore, Kruskal-Wallis test indicates that there is no significant variation exists among the three group of respondents, ie owners, consultants and contractors.

• Journal of KIISE:Databases
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• v.30 no.1
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• pp.80-94
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• 2003

In this paper. we propose an enhanced concurrency control algorithm that minimizes the query delay efficiently. The factors that delay search operations and deteriorate the concurrency of index structures are node splits and MBR updates in multi dimensional index structures. In our algorithm, to reduce the query delay by split operations, we optimize exclusive latching time on a split node. It holds exclusive latches not during whole split time but only during physical node split time that occupies small part of whole split time. Also to avoid the query delay by MBR updates we introduce partial lock coupling(PLC) technique. The PLC technique increases concurrency by using lock coupling only in case of MBR shrinking operations that are less frequent than MBR expansion operations. For performance evaluation, we implement the proposed algorithm and one of the existing link technique-based algorithms on MIDAS-III that is a storage system of a BADA-III DBMS. We show through various experiments that our proposed algorithm outperforms the existing algorithm In terms of throughput and response time.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.313-314
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• 2008

• The Journal of Information Systems
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• v.8 no.1
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• pp.93-108
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• 1999

The switching system is designed and developed to satisfy the performance design objectives recommended by ITU for call processing capacity and quality of service(QOS), etc. When the results by actual measurement at the system testing phase do not satisfy the performance design objectives, however, an effort is required to improve the performance. This paper presents a method for improving QOS by modifying the application programs for the switching system. In the proposed method, the sequence chart related to a delay time for call connection is modelled using PERT(Program Evaluation and Review Technique) network. Then, the criticality index of a message is calculated using Monte Carlo simulation to evaluate which message's processing time to decrease in order to decrease the delay time and thus to improve QOS. The criticality index of a block is also calculated to identify those software blocks that significantly contribute to the delay time.