Dynamic demand fulfillment in spare parts networks with multiple customer classes

We study real-time demand fulfillment for networks consisting of multiple local warehouses, where spare parts of expensive technical systems are kept on stock for customers with di??erent service contracts. Each service contract specifies a maximum response time in case of a failure and hourly penalty costs for contract violations. Part requests can be fulfilled from multiple local warehouses via a regular delivery, or from an external source with ample capacity via an expensive emergency delivery. The objective is to minimize delivery cost and penalty cost by smartly allocating items from the available network stock to arriving part requests. We propose a dynamic allocation rule that belongs to the class of one-step lookahead policies. To approximate the optimal relative cost, we develop an iterative calculation scheme that estimates the expected total cost over an infinite time horizon, assuming that future demands are fulfilled according to a simple static allocation rule. In a series of numerical experiments, we compare our dynamic allocation rule with the optimal allocation rule, and a simple but widely used static allocation rule. We show that the dynamic allocation rule has a small optimality gap and that it achieves an average cost reduction of 7.9% compared to the static allocation rule on a large test bed containing problem instances of real-life size

Co-location synergies : specialized versus diverse logistics concentration areas

Purpose: The purpose of this paper is to contribute to the understanding of spatial concentration of logistics firms by empirically analyzing synergies through co-location and investigating whether co-location of logistics establishments in specialized logistics concentration areas results in benefits compared to co-location in diverse logistics concentration areas. Methodology: A survey among managers of 128 logistics establishments located in logistics concentration areas was used to test for differences between synergies through co-location on specialized versus diverse logistics parks. Findings: The findings show that logistics firms co-located on fresh logistics parks more often share knowledge, combine transport and storage capacity, and trade products last minute than other co-located logistics firms do. Research implications: This research shows that there are synergies through co-location of logistics activities on specialized logistics parks. Managers of logistics companies may need to take these benefits into account in location decisions, academics in facility location models, and policy makers in spatial planning. Originality/value: Although anecdotic evidence suggests that co-location of logistics activities can bring several benefits to the co-located logistics companies and hence, can be important to incorporate in the location decisions of these companies, these benefits are not (much) empirically researched before. This paper analyzes synergies through co-location of logistics establishments on specialized and diverse logistics parks

A stochastic variable size bin packing problem with time constraints

In this paper, we extend the classical Variable Size Bin Packing Problem (VS-BPP) by adding time features to both bins and items. Speciffically, the bins act as machines that process the assigned batch of items with a fixed processing time. Hence, the items are available for processing at given times and are penalized for tardiness. Within this extension we also consider a stochastic variant, where the arrival times of the items have a discrete probability distribution. To solve these models, we build a Markov Chain Monte Carlo (MCMC) heuristic. We provide numerical tests to show the different decision making processes when time constraints and stochasticity are added to VSBPP instances. The results show that these new models entail safer and higher cost solutions. We also compare the performance of the MCMC heuristic and an industrial solver to show the effciency and the effcacy of our method

Coordination and analysis of barge container hinterland networks

We analyze the import hinterland supply chain from the perspective of both the inland terminal operator and of the shippers. In the hinterland supply chain, the interests of capital-intensive terminal operators are not aligned with the interests of shippers. Therefore, we define the joint shipment quantity for container freight distribution that counts for the specific nature of barge transportation. We consider the direct and the tour coordination policies. Based on empirical data, the cost-effectiveness and the performance of these policies is evaluated in detail. Analytical results give insights into the trade-off between the variable transportation costs and the inventory holding costs

Scheduling the scheduling task : a time management perspective on scheduling

Time is the most critical resource at the disposal of schedulers. Hence, an adequate management of time from the schedulers may impact positively on the scheduler’s productivity and responsiveness to uncertain scheduling environments. This paper presents a field study of how schedulers make use of their time and makes explicit what time-management decisions and behaviors are available to a scheduler. Based on observations of the field study, we propose a framework to classify and specify key characteristics of common tasks to the scheduling job in terms of their impact on the workflow and workload of a scheduler. We then discuss how such a framework may be used to assess alternative time-management decisions of a scheduler

A condition-based maintenance policy for multi-component systems with a high maintenance setup cost

Condition-based maintenance (CBM) is becoming increasingly important due to the development of advanced sensor and ICT technology, so that the condition data can be collected remotely. We propose a new CBM policy for multi-component systems with continuous stochastic deteriorations. To reduce the high setup cost of maintenance, a joint maintenance interval is proposed. With the joint maintenance interval and control limits of components as decision variables, we develop a model for the minimization of the average long-run maintenance cost rate of the systems. Moreover, a numerical study on a case of a wind power farm consisting of a large number of non-identical components is performed, including a sensitivity analysis. At last, our policy is compared to a corrective-maintenance-only policy

Relationship between freight accessibility and logistics employment in US counties

This paper analyzes the relationship between freight accessibility and logistics employment in the US. It develops an accessibility measure relevant for logistics companies based on a gravity model. This allows to analyze accessibility of US counties focusing on four dierent modes of transportation: road, rail, air, and maritime. Using a Partial Least Squares model, these four dierent freight accessibility measures are combined into two constructs, continental and intercontinental freight accessibility, and related to logistics employment, dierentiating counties inside metropolitan areas from those outside. Results show that highly accessible non-metropolitan counties attract more logistics employment than other non-metropolitan counties. In metropolitan counties, no signicant relationship was found between freight accessibility and logistics employment. This is primarily explained by the highly signicant relations of both freight accessibility and logistics employment with county population. Keywords: Accessibility, Freight transport, Logistics employmen