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Article
Publication date: 15 July 2019

Shakib Zohrehvandi and Mohammad Khalilzadeh

The purpose of this paper is to present an efficient model for project buffer sizing by taking failure mode and effects analysis (FMEA) into account to reach a more…

Abstract

Purpose

The purpose of this paper is to present an efficient model for project buffer sizing by taking failure mode and effects analysis (FMEA) into account to reach a more realistic schedule.

Design/methodology/approach

In the first phase of the project, several turbines were installed according to the primary schedule with an average duration of 142 days. Then, some of critical chain project management algorithms were separately applied in the implementation and installation of the other wind turbines. The adaptive procedure with resource tightness (APRT) method turned out to be the best method in terms of obtaining a more realistic schedule in this case study. Finally, FMEA was simultaneously applied with APRT.

Findings

Applying the hybrid method to the scheduling of the wind turbines, yielded the more realistic schedule than traditional.

Research limitations/implications

The proposed hybrid APRT-FMEA algorithm was implemented on a real wind farm construction project which was completed with 37 percent shorter duration than the initial estimation; in spite of the initial estimation of 142 days, the project completed in 103 days.

Practical implications

Introducing and implementing a new algorithm which is a combination of buffer sizing algorithms and one of the well-known and mostly used risk assessment methods in order to provide the more realistic project schedule in the construction of wind turbines.

Originality/value

Introducing and implementing a novel algorithm which is a combination of conventional buffer sizing method and one of the efficient risk assessment methods in order to make the schedule more realistic.

Details

Engineering, Construction and Architectural Management, vol. 26 no. 6
Type: Research Article
ISSN: 0969-9988

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Article
Publication date: 21 April 2020

Shakib Zohrehvandi, Mario Vanhoucke and Mohammad Khalilzadeh

This study aims to introduce an efficient project buffer and resource management (PBRM) model for project resource leveling and project buffer sizing and controlling of…

Abstract

Purpose

This study aims to introduce an efficient project buffer and resource management (PBRM) model for project resource leveling and project buffer sizing and controlling of project buffer consumption of a wind power plant project to achieve a more realistic project duration.

Design/methodology/approach

The methodology of this research consists of three main phases. In the first phase of the research methodology, resource leveling is done in the project and resource conflicts of activities are identified. In the second phase, the project critical chain is determined, and the appropriate size of the project buffer is specified. In the third phase of the methodology, buffer consumption is controlled and monitored during the project implementation. After using the PBRM method, the results of this project were compared with those of the previous projects.

Findings

According to the obtained results, it can be concluded that using PBRM model in this wind turbine project construction, the project duration became 25 per cent shorter than the scheduled duration and also 29 per cent shorter than average duration of previous similar projects.

Research limitations/implications

One of the major problems with projects is that they are not completed according to schedule, and this creates time delays and losses in the implementation of projects. Today, as projects in the energy sector, especially renewable projects, are on the increase and also we are facing resource constraint in the implementation of projects, using scheduling techniques to minimize delays and obtain more realistic project duration is necessary.

Practical implications

This research was carried out in a wind farm project. In spite of the initial plan duration of 142 days and average duration of previous similar projects of 146 days, the project was completed in 113 days.

Originality/value

This paper introduces a practical project buffer and resource management model for project resource leveling, project buffer sizing and buffer consumption monitoring to reach a more realistic schedule in energy sector. This study adds to the literature by proposing the PBRM model in renewable energy sector.

Details

International Journal of Energy Sector Management, vol. 14 no. 6
Type: Research Article
ISSN: 1750-6220

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Article
Publication date: 21 November 2016

Ibrahim Bakry, Osama Moselhi and Tarek Zayed

Construction projects are complex projects taking place in dynamic environments, which necessitates accounting for different uncertainties during the planning stage. There…

Abstract

Purpose

Construction projects are complex projects taking place in dynamic environments, which necessitates accounting for different uncertainties during the planning stage. There is a significant lack of management tools for repetitive projects accounting for uncertainties in the construction environment. The purpose of this paper is to present an algorithm for the optimized scheduling of repetitive construction projects under uncertainty.

Design/methodology/approach

Fuzzy set theory is utilized to model uncertainties associated with various input parameters. The developed algorithm has two main components: optimization component and buffering component. The optimization component presents a dynamic programming approach that processes fuzzy numbers. The buffering component converts the optimized fuzzy schedule into a deterministic schedule and inserts time buffers to protect the schedule against anticipated delays. Agreement Index (AI) is used to capture the user’s desired level of confidence in the produced schedule while sizing buffers. The algorithm is capable of optimizing for cost or time objectives. An example project drawn from literature is analysed to demonstrate the capabilities of the developed algorithm and to allow comparison of results to those previously generated.

Findings

Testing the algorithm revealed several findings. Fuzzy numbers can be utilized to capture uncertainty in various inputs without the need for historical data. The modified algorithm is capable of optimizing schedules, for different objectives, under uncertainty. Finally AI can be used to capture users’ desired confidence in the final schedule.

Originality/value

Project planners can utilize this algorithm to optimize repetitive projects schedules, while modelling uncertainty in different input parameters, without the need for relevant historical data.

Details

Engineering, Construction and Architectural Management, vol. 23 no. 6
Type: Research Article
ISSN: 0969-9988

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Article
Publication date: 1 April 1991

Gustavo A. Vargas and Roger G. Dear

The effectiveness of alternative buffering strategies in complexmultilevel assembly manufacturing systems using the Material RequirementPlanning (MRP) methodology is…

Abstract

The effectiveness of alternative buffering strategies in complex multilevel assembly manufacturing systems using the Material Requirement Planning (MRP) methodology is explored and assessed. The safety stock, safety lead time, “hard” safety capacity, and forecast inflation buffering strategies are tested under uncertainties of end‐item demand, resource supply, and task control. The MRP methodology is applied for scheduling along with a complex, realistic simulation model for execution of operations. Average inventory levels for end and component items, capacity utilisation, end‐item backorders and customer undersupport are used as performance measures. Experimental results establish safety stock and “hard” safety capacity as dominant buffering strategies under all uncertainty conditions, and task control is shown as the most disruptive uncertainty source.

Details

Integrated Manufacturing Systems, vol. 2 no. 4
Type: Research Article
ISSN: 0957-6061

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Article
Publication date: 31 July 2007

Min Tang, J.F. Mao and L.L. Jiang

This paper aims to obtain the optimal wire sizing of buffered global interconnects and to investigate the impact of weight factor on the optimized system performance for…

Abstract

Purpose

This paper aims to obtain the optimal wire sizing of buffered global interconnects and to investigate the impact of weight factor on the optimized system performance for various technology nodes.

Design/methodology/approach

The width and spacing of interconnects are optimized under two scenarios, and corresponding optimum line width is determined by minimizing the value of power‐delay product which is defined as a figure of merit (FOM). Based on the results, the impact of weight factor on the optimized system performance, such as delay and power dissipation per unit length, is analyzed for various technology nodes.

Findings

The analytical expressions of the optimum width are derived under two scenarios. Better FOMs can be achieved for the S=W scenario, but the wireability of the chip degrades considerably. The optimized delay increases with the increasing of weight factor, while the optimized power dissipation decreases with it. For a given weight factor, smaller latency and less power dissipation can be achieved for the S=W case.

Originality/value

The analytical expressions of the optimum width of interconnects are given, and a comprehensive study of the impact of weight factor on the optimized results under two scenarios is presented.

Details

Microelectronics International, vol. 24 no. 3
Type: Research Article
ISSN: 1356-5362

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Article
Publication date: 7 July 2020

Nadia Bahria, Imen Harbaoui Dridi, Anis Chelbi and Hanen Bouchriha

The purpose of this study is to develop a joint production, maintenance and quality control strategy involving a periodic preventive maintenance policy.

Abstract

Purpose

The purpose of this study is to develop a joint production, maintenance and quality control strategy involving a periodic preventive maintenance policy.

Design/methodology/approach

The proposed integrated policy is defined and modeled mathematically.

Findings

The paper focuses on finding simultaneously the optimal values of the preventive maintenance period, the buffer stock size, the sample size, the sampling interval and the control chart limits, such that the expected total cost per time unit is minimized.

Practical implications

The paper attempts to integrate in a single model the three main aspects of any manufacturing system: production, maintenance and quality. The considered system consists of one machine subject to a degradation process that directly affects the quality of products. The process and product quality control is carried out using an “x-bar” control chart. In the proposed model, a preventive maintenance action is performed every α inspections of product quality in order to reduce the shift rate to the “out-of-control” state. A corrective maintenance action is undertaken once the control limits are exceeded. In order to palliate perturbations caused by the stopping of the machine to undergo maintenance actions, a buffer stock is built up to ensure the continuous supply of the subsequent machine. The main goal of this work is to develop a model that captures the underlying link between the preventive maintenance policy, the buffer stock size and the parameters of an “x-bar” control chart used to control the quality of the product. Numerical experiments and a study of the effects of the input parameters variation on the obtained results are performed.

Originality/value

The existing models that simultaneously consider maintenance, inventory and control charts consist of a condition-based maintenance (CBM) policy. Periodic preventive maintenance (PM) has not been considered in such models. The proposed integrated model is original, in that it links production through buffer stocks, quality through a control chart and maintenance through periodic preventive maintenance (different practical settings and modeling approach than when CBM is used). Hence, this paper addresses practical situations where, for economic or technical reasons, only systematic periodic preventive maintenance is possible.

Details

Journal of Quality in Maintenance Engineering, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1355-2511

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Article
Publication date: 1 October 1999

Lloyd J. Taylor

This simulation study explores and compares the potential benefits of three work‐in‐process (WIP) inventory drive systems and their associated inventory buffer

Abstract

This simulation study explores and compares the potential benefits of three work‐in‐process (WIP) inventory drive systems and their associated inventory buffer characteristics. The three inventory drives are a push, a pull and a hybrid push/pull system. While these systems have some aspects in common, their buffer management systems vary. The statistical analysis associated with the study was based on data gathered from three computer simulated flow‐shop assembly line environments. Hypotheses concerning the financial performance measurements were established. The independent variables were controlled and manipulated for each of the models. From the statistical analysis, a conclusion was drawn as to which system would afford the operation optimum results. While inventory has traditionally been considered and is currently being shown as an asset from an accounting point of view, it is obvious from the findings of this study, that excess WIP inventory, above the minimal requirements for production, will have a negative effect on the financial measurements evaluated in this study.

Details

Integrated Manufacturing Systems, vol. 10 no. 5
Type: Research Article
ISSN: 0957-6061

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Article
Publication date: 1 November 2002

Lloyd J. Taylor

Compares alternative buffer control systems used in a flow process, assembly line manufacturing system. Follows a literature analysis with the use of computer simulation…

Abstract

Compares alternative buffer control systems used in a flow process, assembly line manufacturing system. Follows a literature analysis with the use of computer simulation to assess and measure the effects of each system on overall production performance, and individual workstation utilization.

Details

Work Study, vol. 51 no. 6
Type: Research Article
ISSN: 0043-8022

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Article
Publication date: 1 October 1996

Simon F. Hurley

Buffers of work throughout a manufacturing facility enhance throughput. They protect a workstation against variations in processing times and against machine breakdowns of…

Abstract

Buffers of work throughout a manufacturing facility enhance throughput. They protect a workstation against variations in processing times and against machine breakdowns of upstream workstations. However, buffer management is still thought to be an open problem: first there is no algebraic way of representing the relationship between buffer size and throughput, and second, the combinatorial nature inherent in the buffer design problem makes it difficult to develop an exact solution. These problems still exist today, as evidenced by the number of research papers that present sophisticated mathematics to solve this complex problem. Refutes all the above points. The buffer management method detailed does not use sophisticated mathematics impenetrable by the average production manager. Presents a heuristically‐based buffer management method effective at protecting throughput. The method will have advantageous effects on the size of buffers and the length of the production lead times, while still providing protection of the throughput rate.

Details

International Journal of Operations & Production Management, vol. 16 no. 10
Type: Research Article
ISSN: 0144-3577

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Article
Publication date: 1 February 2006

H. Kabir, Gholamali C. Shoja and Eric G. Manning

Streaming audio/video contents over the Internet requires large network bandwidth and timely delivery of media data. A streaming session is generally long and also needs a…

Abstract

Streaming audio/video contents over the Internet requires large network bandwidth and timely delivery of media data. A streaming session is generally long and also needs a large I/O bandwidth at the streaming server. A streaming server, however, has limited network and I/O bandwidth. For this reason, a streaming server alone cannot scale a streaming service well. An entire audio/video media file often cannot be cached due to intellectual property right concerns of the content owners, security reasons, and also due to its large size. This makes a streaming service hard to scale using conventional proxy servers. Media file compression using variable‐bit‐rate (VBR) encoding is necessary to get constant quality video playback although it produces traffic bursts. Traffic bursts either waste network bandwidth or cause hiccups in the playback. Large network latency and jitter also cause long start‐up delay and unwanted pauses in the playback, respectively. In this paper, we propose a proxy based constant‐bit‐rate (CBR)‐transmission scheme for VBR‐encoded videos and a scalable streaming scheme that uses a CBRtransmission scheme to stream stored videos over the Internet. Our CBR‐streaming scheme allows a server to transmit a VBRencoded video at a constant bit rate, close to its mean encoding bit rate, and deals with the network latency and jitter issues efficiently in order to provide quick and hiccup free playback without caching an entire media file. Our scalable streaming scheme also allows many clients to share a server stream. We use prefix buffers at the proxy to cache the prefixes of popular videos, to minimize the start‐up delay and to enable near mean bit rate streaming from the server as well as from the proxy. We use smoothing buffers at the proxy not only to eliminate jitter and traffic burst effects but also to enable many clients to share the same server stream. We present simulation results to demonstrate the effectiveness of our streaming scheme.

Details

Interactive Technology and Smart Education, vol. 3 no. 1
Type: Research Article
ISSN: 1741-5659

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