On two-echelon inventory systems with Poisson demand and lost sales

We derive approximations for the service levels of two-echelon inventory systems with lost sales and Poisson demand. Our method is simple and accurate for a very broad range of problem instances, including cases with both high and low service levels. In contrast, existing methods only perform well for limited problem settings, or under restrictive assumptions.\u

Throbbing Between Two Lives: Resource Pooling in Service Supply Chains

Resource pooling is known to benefit performance through reduced congestion, but primarily in settings with homogenous demand. In settings where demand is heterogeneous, pooling can be counter effective. The effects of pooling of staff when demand is heterogeneous and dependent are not known. We present a simulation model based on a service supply chain that delivers Interactive TV to customers. Customers expect high performance in terms of innovativeness and reliability. Based on the results of simulation analysis, we find that when target innovativeness of the service is increased, pooling outperforms not pooling, but the delays that are involved with pooling will make the system and hence its performance unstable. Stable and high performance can be realized through unbalanced hiring. This means that a target performance increase in the upstream stage of the chain (innovation), is accompanied by hiring staff in the downstream stages of the chain (QA and operation)

Supply chain finance : a conceptual framework to advance research

Supply Chain Finance (SCF) arrangements aim to add value by taking a cooperative approach to financing in the supply chain. SCF has recently enjoyed considerable attention from industry, and providers of capital and technology are investing in platforms to facilitate new applications. A limited number of theoretical and empirical studies on the topic have been published. Current trends suggest, however, that the landscape of SCF is becoming increasingly complex and diverse. We describe some key developments and their implications for firms that (may) implement an SCF arrangement. In particular, we show that strategic and tactical considerations may impact the value of these arrangements. Failure to recognize alternatives and associated trade-offs may entail missed opportunities for firms. We present a framework that positions SCF concepts and shows the need for further research. We conclude with observations on managerial relevance

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

Tracebook : a dynamic checklist support system

It has recently been demonstrated that checklist scan enable significant improvements to patient safety. However, their clinical acceptance is significantly lower than expected. This is due to the lack of good support systems. Specifically, support systems are too static: this holds for paper-based support as well as for electronic systems that digitize paper-based support naively. Both approaches are independent from clinical process and clinical context. In this paper, we propose a process-oriented and context-aware dynamic checklist support system: Tracebook. This system supports the execution of complex clinical processes and rules involving data from Electronic Medical Record systems. Workflow activities and forms are specific to individual patients based on clinical rules and they are dispatched to the right user automatically based on a process model. Besides describing the Tracebook functionality in general, this paper demonstrates the support system specifically on an example application that we are preparing for a controlled clinical evaluation. At last we discuss the difference between Tracebook and other support systems which also rely on a checklist format

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

Condition based spare parts supply

We consider a spare parts stock point that serves an installed base of machines. Each machine contains the same critical component, whose degradation behavior is described by a Markov process. We consider condition based spare parts supply, and show that an optimal, condition based inventory policy is 20% more efficient on average than a standard, state-independent base stock policy. We further propose an efficient and effective heuristic policy

Strategies for dynamic appointment making by container terminals

We consider a container terminal that has to make appointments with barges dynamically, in real-time, and partly automatic. The challenge for the terminal is to make appointments with only limited knowledge about future arriving barges, and in the view of uncertainty and disturbances, such as uncertain arrival and handling times, as well as cancellations and no-shows. We illustrate this problem using an innovative implementation project which is currently running in the Port of Rotterdam. This project aims to align barge rotations and terminal quay schedules by means of a multi-agent system. In this\ud paper, we take the perspective of a single terminal that will participate in this planning system, and focus on the decision making capabilities of its intelligent agent. We focus on the question how the terminal operator can optimize, on an operational level, the utilization of its quay resources, while making reliable appointments with barges, i.e., with a guaranteed departure time. We explore two approaches: (i) an analytical approach based on the value of having certain intervals within the schedule and (ii) an approach based on sources of exibility that are naturally available to the terminal. We use simulation to get insight in the benefits of these approaches. We conclude that a major increase in utilization degree could be achieved only by deploying the sources of exibility, without harming the waiting time of barges too much

A unified race algorithm for offline parameter tuning

This paper proposes uRace, a unified race algorithm for efficient offline parameter tuning of deterministic algorithms. We build on the similarity between a stochastic simulation environment and offline tuning of deterministic algorithms, where the stochastic element in the latter is the unknown problem instance given to the algorithm. Inspired by techniques from the simulation optimization literature, uRace enforces fair comparisons among parameter configurations by evaluating their performance on the same training instances. It relies on rapid statistical elimination of inferior parameter configurations and an increasingly localized search of the parameter space to quickly identify good parameter settings. We empirically evaluate uRace by applying it to a parameterized algorithmic framework for loading problems at ORTEC, a global provider of software solutions for complex decision-making problems, and obtain competitive results on a set of practical problem instances from one of the world's largest multinationals in consumer packaged goods