Supply Chain Constraints Research Articles

The South African coal mining industry: A need for a more efficient and collaborative supply chain

It is estimated that about two-thirds of global coal is used for power generation and that, in the next 20 years, over 70% of the demand for coal will come from China and India. Coal accounts for approximately 41% of the world's electricity generation. Demand for thermal coal is influenced by factors that include availability, prices of competing products such as oil, gas and nuclear power, and the demand for electricity. The aim of this article is to provide an exposition of supply chain dynamics within the South African coal mining industry and to argue for a more efficient and collaborative supply chain. The authors attempt to investigate at local and global level, the current trends pertaining to the level of reserves, production and consumption of coal. The article further demonstrates the shortcomings of current logistics in meeting the demand for coal in both domestic and export markets. The article draws from secondary data sourced from academic papers, government and agency documents in the exposition of the coal mining supply chain. The paper concludes by recommending the need for a scientific study on supply chain constraints facing the coal mining industry in South Africa.

The impact on urban distribution operations of upstream supply chain constraints

PurposeThe purpose of this paper is to investigate and quantify the impact of delivery restrictions on costs and environmental performance for a distribution operation.Design/methodology/approachData were gathered from a company and several scenarios with varying delivery restrictions were investigated.FindingsThe results show significant reductions in cost and environmental impacts are achieved when restrictions are relaxed. However, the research also highlighted the importance of adopting a supply chain (SC) approach to the removal of restrictions and the need for public/private sector cooperation.Research limitations/implicationsThe case study is based on one company only. However, the company performs many trips each day to many different customers.Practical implicationsThe paper provides insight into the scope for change in the SC decision‐making processes in order to reduce environmental impacts (and identifies limitations).Originality/valueThe paper is a contribution to better understanding the importance of logistics decisions and not only transport when considering urban freight problems.

A Genetic Algorithm for Directed Graph-based Supply Network Planning in Memory Module Industry

A memory module industry's supply chain usually consists of multiple manufacturing sites and multiple distribution centers. In order to fulfill the variety of demands from downstream customers, production planners need not only to decide the order allocation among multiple manufacturing sites but also to consider memory module industrial characteristics and supply chain constraints, such as multiple material substitution relationships, capacity, and transportation lead time, fluctuation of component purchasing prices and available supply quantities of critical materials (e.g., DRAM, chip), based on human experience. In this research, a directed graph-based supply network planning (DGSNP) model is developed for memory module industry. In addition to multi-site order allocation, the DGSNP model explicitly considers production planning for each manufacturing site, and purchasing planning from each supplier. First, the research formulates the supply network's structure and constraints in a directed-graph form. Then, a proposed genetic algorithm (GA) solves the matrix form which is transformed from the directed-graph model. Finally, the final matrix, with a calculated maximum profit, can be transformed back to a directed-graph based supply network plan as a reference for planners. The results of the illustrative experiments show that the DGSNP model, compared to current memory module industry practices, determines a convincing supply network planning solution, as measured by total profit.

Economic paper blending optimization model with competing materials

PurposeDemanding customers, legislation and raw materials shortages in the modern world have forced companies to minimize the system's environmental impact. The paper seeks to analyze the economic impact of blending in sustainable paper industries in countries such as India.Design/methodology/approachA linear programming model for a paper supply chain is proposed to minimize paper manufacturing cost by optimally blending wood pulp and after‐use paper under various conventional supply chain constraints. The issues of quality, environmental concern and reusability in the paper industry have also been taken into account.FindingsImproving quality of after‐use paper by proper recovery network reduces the manufacturing cost. Increasing proportion of wood fiber in the finished paper decreases the cost, even at the cost of degradation in the environment. Thus, it is up to the manufacturer to reflect its degree of environmental concern to the government and society by assigning appropriate environmental and quality opportunity costs in the model.Research limitations/implicationsDifficulty in obtaining the estimates of the environmental and quality cost is a major limitation of the study.Practical implicationsThis research provides manufacturers with a simple mathematical model to compare the economic feasibility of blending wood pulp and after‐use paper depending on the market situation.Originality/valueThe major contribution of the model is its capability to study the economic impact of blending by considering some of the important sustainable development issues like environment, quality, shortage, and reusability under one objective function.

A CSP approach for the network of product lifecycle constraints consistency in a collaborative design context

In this paper, we are considering that the design process can be modelled in the form of a constraint satisfaction problem (CSP). CSP modelling or resolution has proved its efficiency within the framework of single-designer design. We propose to extend the functions of CSP to the context of multi-concept design of the same artefact. We define CoCSP as cooperative constraint satisfaction problem including the actors of the design problem. We are presenting the operating principles of an algorithm for the real-time management of design decisions, based on a model described in the form of a CoCSP for the integration of supply-chain constraints. This algorithm enables the number of design decisions rejected at a given moment in design to be kept to a minimum. The algorithm forms the core of a prototype for an unsupervised, generic constraint-based collaborative design system. Our aim is to produce a platform centred on the notion of constraints that will enable a product design problem to be modelled and solved by integrating supply-chain constraints as far upstream as possible.

Realities of Supply Chain Collaboration

Successful supply chain collaboration (SCC) practices are rather exceptional, yet collaboration is believed to be the single most pressing need in supply chain management. In this paper we discuss the realities of SCC, present prerequisites for the collaboration process, indicate where the process starts and where it may terminate. During the discussion we make use of the concepts of Theory of Constraints (TOC) and approach SCC as an ongoing effort dealing with the supply chain constraints. The roles of the entities in this ongoing effort are not always clear. Often SCC is proclaimed to be a joint decision-making process. However, keeping in mind the powerhouses in the chain, we believe that other structures are possible as well. We emphasize the need for: 1) having an adequate supply chain strategy and well-articulated goals, which form the basis for: 2) leading supply chain change, and: 3) governing the continual process of strategy alignment and supply chain change, which is itself a dynamic process. These three tasks are featured by many interactions and characterize the continuous improvement of a SCC process. A step-by-step approach like this enables the involved chain entities to climb the ladder of collaboration and take the supply chain performance to a higher level.

Supply Loops and Their Constraints: The Industrial Ecology of Recycling and Reuse

An increasing number of firms in Asia, Europe, and North America engage in voluntary or mandatory end-of-life product management. Since developments in product takeback are driven by a mixture of environmental concerns and economic opportunities, the most promising corporate end-of-life strategies create both economic and environmental value. This article introduces a framework that can help managers identify and assess such supply loop strategies. The usefulness of the framework is demonstrated by applying it to two specific supply loops, recycling and reuse of structural steel sections in the UK construction sector. The case study highlights the importance of supply chain constraints and also shows how lack of data can be a major obstacle to the evaluation of potential win-win supply loops.

Quantity and Due Date Quoting Available to Promise

The available to promise (ATP) function has increasingly attracted the attention of the supply chain management research community as a tool for enhancing the responsiveness of order promising and the reliability of order fulfillment. It directly links available resources, including both material and capacity, with customer orders and, thus, affects the overall performance of a supply chain. In this paper, a mixed integer programming (MIP) model for a quantity and due date quoting ATP mechanism is presented. This model can provide individual order delivery dates for a batch of customer orders that arrive within a predefined batching interval. In addition, the model allows customized configurations and takes into account a variety of realistic supply chain constraints, such as material compatibility, substitution preferences, capacity utilization, and material reserve. We conclude this paper with sensitivity analysis of performance impacts with respect to batching interval size and material reserve policy.

Use of petroleum as steam fuel in place of coal

This study was planned to offer the roadmap for lifecycle clean shipping by addressing the fundamental question of ‘what are the promising energy solutions for the shipping sector?’. This goal was attempted to be achieved by a lifecycle comparative analysis of the viability of three zero-carbon fuels, ammonia, hydrogen, and inland electricity, based on the operational practicality as well as Well-to-Wake environmental impacts. Credible business scenarios were designed with a high-level screening of 27 short-route ferries currently engaged in 26 West-Scotland coastal routes. Then a series of comparative analyses between the diesel and the proposed alternative fuel sources was conducted. While carbon-free fuels are in the early stages of development in the UK, there are various views on how these fuels can be produced, distributed, and used onboard for the clean shipping economy. To determine the optimal energy solutions, all credible scenarios for the upstream pathways for these fuels were developed, based on the current and future prospected UK energy infrastructure and grids. Those scenarios were examined for West-Scotland shipping and extended to the UK targets. Their technical aspects for maritime application were also investigated in consideration of safety, regulation, infrastructural availability, supply chain constraints, barriers, and the downstream emission pathways to their uptake onboard. Ship conceptual designs were briefly conducted to evaluate the systems, technologies, and equipment required for onboard installation to utilise zero-carbon fuels. As a result of the study, when hydrogen was used as a fuel in fuel cells and electricity was supplied as a backup from batteries that store inland power and the solar PV system, GHG emissions were 25.7% of the conventional fossil fuel-using scenario. In addition, it was confirmed that GWP was 22.2% compared to MGO when ammonia was used as fuel without reforming into hydrogen and backup power was supplied from batteries and the solar PV system. It is believed that the analysis results can distinctively demonstrate the adequacy or the inadequacy of current maritime policies for decarbonising shipping. This research finally provides potential solutions for future UK maritime environmental protection and for enhancing the competitiveness of ship owners. In addition, this research concept can serve as a sample that suggests the direction of ideal research for future energy solutions in the marine sector.