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Article
Publication date: 5 March 2018

Hamidreza Izadbakhsh, Rassoul Noorossana and Seyed Taghi Akhavan Niaki

The purpose of this paper is to apply Poisson generalized linear model (PGLM) with log link instead of multinomial logistic regression to monitor multinomial logistic…

Abstract

Purpose

The purpose of this paper is to apply Poisson generalized linear model (PGLM) with log link instead of multinomial logistic regression to monitor multinomial logistic profiles in Phase I. Hence, estimating the coefficients becomes easier and more accurate.

Design/methodology/approach

Simulation technique is used to assess the performance of the proposed algorithm using four different control charts for monitoring.

Findings

The proposed algorithm is faster and more accurate than the previous algorithms. Simulation results also indicate that the likelihood ratio test method is able to detect out-of-control parameters more efficiently.

Originality/value

The PGLM with log link has not been used to monitor multinomial profiles in Phase I.

Details

International Journal of Quality & Reliability Management, vol. 35 no. 3
Type: Research Article
ISSN: 0265-671X

Keywords

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Article
Publication date: 12 February 2018

Seyed Hamid Reza Pasandideh, Seyed Taghi Akhavan Niaki and Pejman Ahmadi

In this paper, the joint replenishment problem is modeled for a two-level supply chain consisting of a single supplier and multiple retailers that use the vendor-managed…

Abstract

Purpose

In this paper, the joint replenishment problem is modeled for a two-level supply chain consisting of a single supplier and multiple retailers that use the vendor-managed inventory (VMI) policy for several products. This paper aims to find the optimal number of products to order in both policies, the optimal times at which each retailer orders the products in the traditional policy and the optimal times at which the supplier orders the product in the VMI policy.

Design/methodology/approach

The problem is first formulated into the framework of a constrained integer nonlinear programming model; then, the problem is solved using a teacher-learner based optimization algorithm. As there are no benchmarks available in the literature, a genetic algorithm is used as well to validate the results obtained.

Findings

The solutions obtained using both the algorithms for several numerical examples are compared to the ones of a random search procedure for further validation. A real case is solved at the end to demonstrate the applicability of the proposed methodology and to compare both the policies.

Research limitations/implications

The paper does not have any special limitations.

Practical implications

The study has significant practical implications for the sellers and for the suppliers who have to get the most profit. Also, satisfying the constraints make decision more complicated.

Originality/value

This paper has two main originalities. The authors have developed the model of the joint replenishment problem and have contributed in the problem-solving process. They have used a new meta-heuristic and then compared it to a classic one.

Details

Journal of Modelling in Management, vol. 13 no. 1
Type: Research Article
ISSN: 1746-5664

Keywords

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Article
Publication date: 3 December 2020

Maryam Shabani, Naser Shams Gharneh and Seyed Taghi Akhavan Niaki

Tackling the challenges of water scarcity requires comprehensive management according to financial, environmental and social issues. This paper aims to develop a planning…

Abstract

Purpose

Tackling the challenges of water scarcity requires comprehensive management according to financial, environmental and social issues. This paper aims to develop a planning approach for systematic decision-making and pay attention to uncertainties in water demand management and supply investment.

Design/methodology/approach

This study presents a multiobjective optimization model to manage water resources based on the balance of supply and demand. The objectives of the model include economic, social and environmental (sustainable development) factors. The model achieves an optimal urban water portfolio by using a scenario tree.

Findings

The mathematical goal programming (GP) in a multiobjective optimization model is applied and solved by the branch and bound method. The results indicate the selected supply augmentation and demand management options in each stage for 20 years according to the dry, normal and wetness year scenarios.

Practical implications

This model is based on a real-world case and has been implemented in the city of Karaj. It can be applied for water management of other cities concerning sustainable development as well.

Originality/value

This paper innovates by considering the sustainable development criteria that are defined using three objective functions, including economic, social and environmental factors. The balance of supply and demand concerning uncertainty has not been investigated in any urban water portfolios. The standardized precipitation evapotranspiration index (SPEI) is incorporated to generate different scenarios. To the best of the authors’ knowledge, this approach is used for the first time.

Details

Management of Environmental Quality: An International Journal, vol. 32 no. 2
Type: Research Article
ISSN: 1477-7835

Keywords

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Article
Publication date: 29 November 2018

Hamed Fazlollahtabar and Seyed Taghi Akhavan Niaki

The purpose of this paper is to estimate the required number of robots consisting of some non-repairable components, by employing a renewal model. Considering the…

Abstract

Purpose

The purpose of this paper is to estimate the required number of robots consisting of some non-repairable components, by employing a renewal model. Considering the importance of the availability of standby autonomous robots for reducing and preventing down-times of advanced production systems, which imposes a considerable loss, the present research tries to introduce a practical model for the determination of the required number of autonomous robots.

Design/methodology/approach

Most of the available research on the estimation of the required standby components based on the reliability characteristics of components has not considered the environmental factors influencing the reliability characteristics. Therefore, such estimations are not accurate enough. In contrast, this paper focuses on the influence of the environmental and human factors (e.g. the operators’ skill) on the robot reliability characteristics.

Findings

A model based on the Weibull renewal process combined with the cold standby strategy is developed for reliability evaluation of the system. The effectiveness of the proposed integrated reliability evaluation model is worked out in some cases.

Originality/value

Determining a required number of robots is an important issue in availability and utilization of a complex robotic production system. In an advanced production system, while the estimation process of a required number of robots can be performed through different approaches, one of the realistic estimation methods is based on the system’s reliability that takes into consideration the system operating environment. To forecast the required number of robots for an existing production system, in some cases, the assumption of a constant failure rate does not differ much from the assumption of a non-constant failure rate and can be made with an acceptable error.

Details

International Journal of Quality & Reliability Management, vol. 35 no. 10
Type: Research Article
ISSN: 0265-671X

Keywords

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Article
Publication date: 16 October 2017

Hamed Fazlollahtabar and Seyed Taghi Akhavan Niaki

This paper aims to conduct a comprehensive fault tree analysis (FTA) on the critical components of industrial robots. This analysis is integrated with the reliability…

Abstract

Purpose

This paper aims to conduct a comprehensive fault tree analysis (FTA) on the critical components of industrial robots. This analysis is integrated with the reliability block diagram (RBD) approach to investigate the robot system reliability.

Design/methodology/approach

For practical implementation, a particular autonomous guided vehicle (AGV) system was first modeled. Then, FTA was adopted to model the causes of failures, enabling the probability of success to be determined. In addition, RBD was used to simplify the complex system of the AGV for reliability evaluation purpose.

Findings

Hazard decision tree (HDT) was configured to compute the hazards of each component and the whole AGV robot system. Through this research, a promising technical approach was established, allowing decision-makers to identify the critical components of AGVs along with their crucial hazard phases at the design stage.

Originality/value

As complex systems have become global and essential in today’s society, their reliable design and determination of their availability have turned into very important tasks for managers and engineers. Industrial robots are examples of these complex systems that are being increasingly used for intelligent transportation, production and distribution of materials in warehouses and automated production lines.

Details

Industrial Robot: An International Journal, vol. 44 no. 6
Type: Research Article
ISSN: 0143-991X

Keywords

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Article
Publication date: 19 September 2019

Afshin Yaghoubi, Seyed Taghi Akhavan Niaki and Hadi Rostamzadeh

The purpose of this paper is to derive a closed-form expression for the steady-state availability of a cold standby repairable k-out-of-n system. This makes the…

Abstract

Purpose

The purpose of this paper is to derive a closed-form expression for the steady-state availability of a cold standby repairable k-out-of-n system. This makes the availability calculation much easier and accurate.

Design/methodology/approach

Assuming exponential distributions for system failure and repair, the Markov method is employed to derive the formula.

Findings

The proposed formula establishes an easier and faster venue and provides accurate steady-state availability.

Research limitations/implications

The formula is valid for the case when the probability density function of the component failure and the repair is exponential.

Originality/value

The Markov method has never been used in the literature to derive the steady-state availability of a cold standby repairable k-out-of-n: G system.

Details

International Journal of Quality & Reliability Management, vol. 37 no. 1
Type: Research Article
ISSN: 0265-671X

Keywords

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