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Article

Christopher Rose and Jenny Coenen

The purpose of this paper is to present a method for generating a set of feasible, optimized production schedules for the erection process of compact shipyards building…

Abstract

Purpose

The purpose of this paper is to present a method for generating a set of feasible, optimized production schedules for the erection process of compact shipyards building complex ship types.

Design/methodology/approach

A bi-objective mathematical model is developed based on the process constraints. A Pareto front of possible erection schedules is created using a the Non-dominated Sorting Genetic Algorithm II with a custom heuristic fitness function and constraint violation.

Findings

It was possible to consistently generate a wide variety of production schedules with superior performance to those manually created by shipyard planner in negligible computational time.

Practical implications

The set of optimized production schedules generated by the developed methodology can be used as a starting point by existing shipyard planners when drafting the initial erection planning for a new project. This allows the planners to consider wider variety of options in less time.

Originality/value

No other published approach for the automatic generation of optimized production schedules of the erection process is specifically tailored to the construction of complex ships.

Details

Journal of Manufacturing Technology Management, vol. 27 no. 4
Type: Research Article
ISSN: 1741-038X

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Article

Alexandros Kallantzis and Sergios Lambropoulos

A scheduling method for determining the critical path in linear projects is presented, that takes into account maximum time and distance constraints in addition to the…

Abstract

A scheduling method for determining the critical path in linear projects is presented, that takes into account maximum time and distance constraints in addition to the commonly used minimum time and distance constraints. The maximum constraints, though often present in the specifications of a project, are not considered during the planning procedure, since no method existed to enable scheduling with them. The proposed method builds on the concept of the maximum constraints and expands on the necessary background for their implementation into the schedule. The introduced critical path algorithm allows for grouping linear activities into four categories regarding their critical status and their ability to influence project duration. The method is applied to a low‐pressure pipeline construction project and the results are presented.

Details

Engineering, Construction and Architectural Management, vol. 11 no. 3
Type: Research Article
ISSN: 0969-9988

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Article

Rok Cajzek and Uroš Klanšek

The purpose of this paper is cost optimization of project schedules under constrained resources and alternative production processes (APPs).

Abstract

Purpose

The purpose of this paper is cost optimization of project schedules under constrained resources and alternative production processes (APPs).

Design/methodology/approach

The model contains a cost objective function, generalized precedence relationship constraints, activity duration and start time constraints, lag/lead time constraints, execution mode (EM) constraints, project duration constraints, working time unit assignment constraints and resource constraints. The mixed-integer nonlinear programming (MINLP) superstructure of discrete solutions covers time–cost–resource options related to various EMs for project activities as well as variants for production process implementation.

Findings

The proposed model provides the exact optimal output data for project management, such as network diagrams, Gantt charts, histograms and S-curves. In contrast to classic scheduling approaches, here the optimal project structure is obtained as a model-endogenous decision. The project planner is thus enabled to achieve optimization of the production process simultaneously with resource-constrained scheduling of activities in discrete time units and at a minimum total cost.

Practical implications

A set of application examples are addressed on an actual construction project to display the advantages of proposed model.

Originality/value

The unique value this paper contributes to the body of knowledge reflects through the proposed MINLP model, which is capable of performing the exact cost optimization of production process (where presence and number of activities including their mutual relations are dealt as feasible alternatives, meaning not as fixed parameters) simultaneously with the associated resource-constrained project scheduling, whereby that is achieved within a uniform procedure.

Details

Engineering, Construction and Architectural Management, vol. 26 no. 10
Type: Research Article
ISSN: 0969-9988

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Article

Muhaned Gilani and Durmuş Sinan Körpe

This paper aims to minimize aircraft fuel consumption during the cruise phase when the flight is subjected to a specific time of arrival for different weights and distances.

Abstract

Purpose

This paper aims to minimize aircraft fuel consumption during the cruise phase when the flight is subjected to a specific time of arrival for different weights and distances.

Design/methodology/approach

The approach adopted herein uses sequential quadratic programming algorithm from MATLAB optimization toolbox, which includes a mathematical model of a jet airliner based on the Base of Aircraft Data as a function evaluator, to find out the impact of meet-time of arrival constraints on fuel consumption. The cruising speeds at predefined segments and the altitude are defined as the design variables.

Findings

The algorithm determines the optimum cruise altitudes and speeds for minimum fuel consumption in the case of no time constraints, also, for different time constraints where the flight time shall be reduced by increasing speed and lowering the altitude in most of the investigated cases.

Practical implications

The algorithm computes the optimum speed and the altitude according to different flight scenarios with the meet-time of arrival constraints for minimum fuel consumption which affects the direct operating cost of the flight. The algorithm might greatly help in decision-making for the meet-time of arrival operations.

Originality/value

Developing an algorithm to optimize the speed and the altitude of an aircraft based on weight and range for minimization of fuel consumption. It is a pioneer study in the literature that deals with the effect of meet-time constraints on fuel consumption.

Details

Aircraft Engineering and Aerospace Technology, vol. 92 no. 7
Type: Research Article
ISSN: 1748-8842

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Article

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

Binghai Zhou and Shi Zong

The cross-docking strategy has a significant influence on supply chain and logistics efficiency. This paper aims to investigate the most suitable and efficient way to…

Abstract

Purpose

The cross-docking strategy has a significant influence on supply chain and logistics efficiency. This paper aims to investigate the most suitable and efficient way to schedule the transfer of logistics activities and present a meta-heuristic method of the truck scheduling problem in cross-docking logistics. A truck scheduling problem with products time window is investigated with objectives of minimizing the total product transshipment time and earliness and tardiness cost of outbound trucks.

Design/methodology/approach

This research proposed a meta-heuristic method for the truck scheduling problem with products time window. To solve the problem, a lower bound of the problem is built through a novel two-stage Lagrangian relaxation problem and on account of the NP-hard nature of the truck scheduling problem, the novel red deer algorithm with the mechanism of the heuristic oscillating local search algorithm, as well as adaptive memory programming was proposed to overcome the inferior capability of the original red deer algorithm in the aspect of local search and run time.

Findings

Theory analysis and simulation experiments on an industrial case of a cross-docking center with a product’s time window are conducted in this paper. Satisfactory results show that the performance of the red deer algorithm is enhanced due to the mechanism of heuristic oscillating local search algorithm and adaptive memory programming and the proposed method efficiently solves the real-world size case of truck scheduling problems in cross-docking with product time window.

Research limitations/implications

The consideration of products time window has very realistic significance in different logistics applications such as cold-chain logistics and pharmaceutical supply chain. Furthermore, the novel adaptive memory red deer algorithm could be modified and applied to other complex optimization scheduling problems such as scheduling problems considering energy-efficiency or other logistics strategies.

Originality/value

For the first time in the truck scheduling problem with the cross-docking strategy, the product’s time window is considered. Furthermore, a mathematical model with objectives of minimizing the total product transshipment time and earliness and tardiness cost of outbound trucks is developed. To solve the proposed problem, a novel adaptive memory red deer algorithm with the mechanism of heuristic oscillating local search algorithm was proposed to overcome the inferior capability of genetic algorithm in the aspect of local search and run time.

Details

Engineering Computations, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0264-4401

Keywords

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Abstract

Details

The Economics of Time Use
Type: Book
ISBN: 978-1-84950-838-4

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Article

Carl Kronlid and Enrico Baraldi

This paper aims to focus on time-constrained interactions involving industry and public actors, mainly universities, conducting research. This kind of interaction has…

Abstract

Purpose

This paper aims to focus on time-constrained interactions involving industry and public actors, mainly universities, conducting research. This kind of interaction has become increasingly important to develop new pharmaceuticals, especially antibiotics. The proposed theoretical frame relies on industrial marketing and purchasing’s interactive perspective on inter-organizational relationships and especially the activities, resource, actors model, combined with key concepts on temporary organizing and project management. This study identifies the temporality and time constraints imposed by this project on public–private interactions, specific coordination tools used to create such temporality and time constraints and their consequences, including positive and negative effects for the interacting parties.

Design/methodology/approach

The study builds on a single in-depth qualitative case study of a major antibiotics R&D collaboration project called ENABLE.

Findings

For negative consequences, this model includes the need for constantly rebuilding trust due to fast turnover of actors, difficulties in combining resources as efficiently as possible, resource constraints, bottlenecks and neglect of some activities, such as publishing, which are normally pivotal for universities. Despite these problematic consequences of temporality, resources are rapidly made available and new competencies learned quickly. Another positive effect is the possibility to achieve complex adaptations of resources and activities even in short time frames. Importantly, projects can act as a springboard for the parties to continue collaboration and in the long term develop a continuous business relationship.

Originality/value

Based on the findings the authors develop a model of time-constrained inter-organizational interaction between public and private organizations.

Details

Journal of Business & Industrial Marketing, vol. 35 no. 6
Type: Research Article
ISSN: 0885-8624

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Article

Jian Hu, Naigang Cui, Yuliang Bai and Yunhai Geng

The purpose of this paper is to present a novel guidance law that is able to control the impact time while the seeker’s field of view (FOV) is constrained.

Abstract

Purpose

The purpose of this paper is to present a novel guidance law that is able to control the impact time while the seeker’s field of view (FOV) is constrained.

Design/methodology/approach

The new guidance law is derived from the framework of Lyapunov stability theory to ensure interception at the desired impact time. A time-varying guidance gain scheme is proposed based on the analysis of the convergence time of impact time error, where finite-time stability theory is used. The circular trajectory assumption is adopted for the derivation of accurate analytical estimation of time-to-go. The seeker’s FOV constraint, along with missile acceleration constraint, is considered during guidance law design, and a switching strategy to satisfy it is designed.

Findings

The proposed guidance law can drive missile to intercept stationary target at the desired impact time, as well as satisfies seeker’s FOV and missile acceleration constraints during engagement. Simulation results show that the proposed guidance law could provide robustness against different engagement scenarios and autopilot lag.

Practical implications

The presented guidance law lays a foundation for using cooperative strategies, such as simultaneous attack.

Originality/value

This paper presents further study on the impact time control problem considering the seeker’s FOV constraint, which conforms better to reality.

Details

Aircraft Engineering and Aerospace Technology, vol. 91 no. 1
Type: Research Article
ISSN: 1748-8842

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Article

Marwa Khalfalli, Fouad Ben Abdelaziz and Hichem Kamoun

The purpose of this paper is to generate a daily operating theater schedule aiming to minimize completion time and maximum overtime while integrating real-life surgeon…

Abstract

Purpose

The purpose of this paper is to generate a daily operating theater schedule aiming to minimize completion time and maximum overtime while integrating real-life surgeon constraints, such as their role, specialty, qualification and availability.

Design/methodology/approach

The paper deals with complete surgery process using multi-objective surgery scheduling approach. Furthermore, the combinatorial nature of the studied problem does not allow to solve it to optimality. Therefore, the authors developed two approaches embedded in a tabu search metaheuristic, namely, weighted sum and e-constraint, to minimize completion time and maximum overtime.

Findings

The integration of the upstream and downstream services of an intervention and the consideration of the specific constraints related to surgeons are very essential to obtaining more closed schedules to the realty.

Practical implications

The paper includes implications for the development of efficient schedules for a significant number of operations coming from different specialties throughout its complete surgery process under multi-resource constraints.

Social implications

The paper can help hospital managers and decision makers to well manage the budget by minimizing the overtime cost and by offering efficient daily operating theater schedule.

Originality/value

The results of the paper will help hospital managers and decision makers to well manage the budget by minimizing the overtime cost and offering efficient daily operating theater schedule.

Details

Management Decision, vol. 57 no. 2
Type: Research Article
ISSN: 0025-1747

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