Integer Linear Programming Mathematical Model Research Articles

Fuzzy optimization of a waste-to-energy network system in an eco-industrial park

The Ulsan Eco-Industrial Park (EIP) in South Korea houses as many as 1,000 companies, which generate about 524,000 t/year of organic waste. Of this total, 34 % is recycled, 8 % is incinerated with energy recovery, and the rest (58 %) is disposed of by ocean dumping (45 %), landfilling (11 %), or incineration without energy recovery (2 %). Although 42 % of the total waste generated at Ulsan EIP is recycled for material and energy recovery, additional opportunities to recover energy from improperly disposed of or incompletely utilized waste are possible through existing waste-to-energy (WTE) networks. To find an optimal WTE network in the Ulsan EIP, a fuzzy mixed integer linear programming mathematical model was developed to meet energy supply and demand (in terms of both quantity and grade) while considering the satisfaction level of potential stakeholders (e.g., the EIP initiator and tenants). The developed model was applied to two different scenarios that considered the requirements of EIP tenants for waste treatment and energy recovery. Based on the satisfaction level of the stakeholders, the WTE networks were analyzed to establish an optimal WTE network with maximum energy production and a minimal payback period.

A multi-step approach to long-term open-pit production planning

The objective of this paper is to develop, verify, and present a multi–step methodology for three interrelated key components of open–pit mine planning: controlled optimal phase–design, characterisation of selective mining–units, and long–term production scheduling optimisation. A hybrid solution methodology for open–pit phase–design using integer programming and a local search heuristic is presented. Next, a hierarchical clustering approach with size and shape control, which aggregates blocks into minable polygons constrained within the pushback boundaries, is presented; and finally, a mixed integer linear programming mathematical model, which uses the generated pushbacks and aggregates as the planning units to provide near–optimal practical life–of–mine schedules, is introduced. In addition, the model inherently solves the cut–off grade optimisation problem. Two case–studies of real–size deposits are presented to illustrate practicality of the developed methodologies, and also to compare the results against industrial conventional practices to assess validity, performance, strengths, and limitations of the developed methodologies.

A multi-period model for managing used product returns

During the last decades there has been a consistent need for companies to manufacture ‘green’ products in order to contribute to environmental protection. The utilisation of used products (literally, the extension of their useful life cycle) is an excellent, indirect way for companies to conform to this requirement and, at the same time, increase their profit. In this paper a mixed integer linear programming mathematical model is proposed, which can be used for the optimisation of procurement, remanufacturing, stocking and salvaging decisions. The model is flexible enough to incorporate multiple suppliers, several quality levels of returned products and multiple periods of time. The applicability of the model is demonstrated through the optimisation of alternative scenarios, the optimal solutions of which reveal the potential profitability of used products exploitation.

Optimising service quality translating via quantitative quality function deployment

This study aims to create a model to use internal measures for service quality evaluation. Using internal measures provides continuous (daily) service quality measurement and faster improvement efforts allocation, we find them more applicable and useful for service quality measurement. This paper demonstrates that using SERVQUAL lonely cannot be efficient, so we need some new improvements. This study proposes a model that can use internal measures for continuous and more effective evaluation. The quality function development method is used for translating customer expectation to internal measures. SERVQUAL dimensions or statements are employed as customer expectation that they are perceived by SERVQUAL questionnaire. Moreover, this paper tries to optimise this translation by a mixed integer linear programming mathematical model. This model can optimise the service quality translation to enrich the internal evaluation with customer opinions. Finally, the proposed model is employed for optimising the evaluation of the train’s internal service quality.

Optimising reverse logistics network to support policy-making in the case of Electrical and Electronic Equipment

Due to the rapid growth of Waste Electrical and Electronic Equipment (WEEE) volumes, as well as the hazardousness of obsolete electr(on)ic goods, this type of waste is now recognised as a priority stream in the developed countries. Policy-making related to the development of the necessary infrastructure and the coordination of all relevant stakeholders is crucial for the efficient management and viability of individually collected waste. This paper presents a decision support tool for policy-makers and regulators to optimise electr(on)ic products’ reverse logistics network. To that effect, a Mixed Integer Linear Programming mathematical model is formulated taking into account existing infrastructure of collection points and recycling facilities. The applicability of the developed model is demonstrated employing a real-world case study for the Region of Central Macedonia, Greece. The paper concludes with presenting relevant obtained managerial insights.