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Author

Ralf Elbert

Other affiliations: Technical University of Berlin
Bio: Ralf Elbert is an academic researcher from Technische Universität Darmstadt. The author has contributed to research in topics: Order picking & Supply chain. The author has an hindex of 10, co-authored 109 publications receiving 506 citations. Previous affiliations of Ralf Elbert include Technical University of Berlin.


Papers
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Journal ArticleDOI
TL;DR: An exploratory case study is used to highlight how order pickers perceive order picking routes, and an agent-based simulation model is developed to quantify the effects of deviations from pre-specified routes.

43 citations

Posted Content
TL;DR: In this article, the authors present a detailed evaluation of the relative efficiency of order picker routing policies when order pickers deviate from pre-specified routes, and conclude that the optimal routing policy should be the preferred option in most real-world scenarios.
Abstract: An exploratory case study is used to highlight how order pickers perceive order picking routes.A simulation model is developed to quantify the effects of route deviations on routing policies.Optimal routing policy keeps its performance advantage even when routing deviations occur. Retrieving items from storage locations in warehouses, commonly referred to as order picking, is often performed by human workers. The high amount of human work involved in order picking turns this activity into a time- and cost-intensive process step in warehouse operations. Due to the cost impact of manual order picking, researchers have developed various planning methods that support practitioners in realizing an efficient order picking process. Among these planning approaches, methods that support the routing of order pickers through the warehouse have been a very popular research topic in recent years, with the focus being both on the development of optimal and heuristic routing policies. Surprisingly, problems that may arise when implementing picker routes for human workers in practice have not been investigated so far. There is, however, empirical evidence that order pickers tend to deviate from optimal routes, putting the efficiency of these routing approaches at stake.This paper presents a detailed evaluation of the relative efficiency of order picker routing policies when order pickers deviate from pre-specified routes. First, different behavioral factors that may result in deviations from pre-specified routes are identified in a state-of-the-art literature review and using the results of an exploratory case study. Subsequently, an agent-based simulation model is developed to quantify the effects of deviations from pre-specified routes. The simulation model is then used to compare different routing policies in an extensive simulation experiment. The results of this paper indicate that even in case order pickers deviate from given routes, implementing the optimal routing policy should be the preferred option in most real-world scenarios.

40 citations

Journal ArticleDOI
TL;DR: In this article, an agent-based simulation model (ABS) was developed for order picking in a rectangular warehouse, and the simulation model determined shortest mean throughput times when the same routing policy is assigned to all order pickers.
Abstract: Order picking is one of the most costly logistics processes in warehouses. As a result, the optimization of order picking processes has received an increased attention in recent years. One potential source for improving order picking is the reduction of picker blocking. The purpose of this paper is to investigate picker blocking under different storage assignment and order picker-route combinations and evaluate its effects on the performance of manual order picking processes.,This study develops an agent-based simulation model (ABS) for order picking in a rectangular warehouse. By employing an ABS, we are able to study the behaviour of individual order pickers and their interactions with the environment.,The simulation model determines shortest mean throughput times when the same routing policy is assigned to all order pickers. In addition, it evaluates the efficiency of alternative routing policies–storage assignment combinations.,The paper implies that ABS is well-suited for further investigations in the field of picker blocking, for example, with respect to the individual behaviour of agents.,Based on the results of this paper, warehouse managers can choose an appropriate routing policy that best matches their storage assignment policy and the number of order pickers employed.,This paper is the first to comprehensively study the effects of different combinations of order picker routing and storage assignment policies on the occurrence of picker blocking.

36 citations

Journal ArticleDOI
TL;DR: In this paper, the authors define the concept of maverick picking and study its causes, its forms of appearance, and its potential impact on order picking performance in order picking, the process of retrieving items from their storage locations to fulfil customer orders.
Abstract: Order picking, the process of retrieving items from their storage locations to fulfil customer orders, ranks among the most labour- and time-intensive processes in warehousing. Prior research in this area had a strong focus on the development of operating policies that increase the efficiency of manual order picking, for example by calculating optimal routes for the order pickers or by assigning products to storage locations. One aspect that poses a major challenge to many warehouse managers in practice has, curiously enough, remained largely unexplored by academic research: modifications in workflows (i.e. workplace deviance in a positive or negative sense) in order picking, which we define as ‘maverick picking’. The purpose of this paper is to characterise maverick picking and to study its causes, its forms of appearance and its potential impact on order picking performance. To gain insights into maverick picking, we first survey the literature to illustrate the state-of-knowledge of maverick picking. S...

36 citations

Journal ArticleDOI
TL;DR: In this paper, the authors explored the modal split between road freight transport and combined transport that is enabled by horizontal transshipment technologies, given a dependence on the changing transport mode characteristics that are caused by direct intervention through transport policies as well as by changing environmental factors such as increasing freight volume or diesel prices.
Abstract: The technological solutions for the horizontal transshipment of non-liftable semi-trailers allow the decision makers in the transport market to consider an additional transport alternative to road transportation in the mode choice decision: combined transport. This study explores the modal split between road freight transport and combined transport that is enabled by horizontal transshipment technologies, given a dependence on the changing transport mode characteristics that are caused by direct intervention through transport policies as well as by changing environmental factors such as increasing freight volume or diesel prices. In addition, the impact of the heterogeneous forwarders’ business models is considered. To estimate the modal split between the road and the combined transport, we combine a Bass model with a discrete choice model. Based on the data derived from an online questionnaire distributed to German forwarders, the model estimates a maximum 42% market penetration ratio for the combined transport. This ratio is captured with the help of the direct subsidization of rail line hauling, which is consequently the strongest lever for the modal shift. This lever is followed by the introduction of long trains, bringing a maximum market penetration of approximately 35%. We reveal that the policies that directly promote combined transport have a stronger effect on the modal shift than the policies that discriminate against road transport. Furthermore, we find that the leverage of the transport policies for the medium range distances is significantly higher than for the long distances. These results can be used as a decision support by government officials for the configuration of their specific transport policies as well as by logistics service providers to adjust their technology investment decisions based on the anticipated user demand in different situations.

22 citations


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Posted Content
01 Jan 1994
TL;DR: In this paper, a natural resource-based view of the firm is proposed, which is composed of three interconnected strategies: pollution prevention, product stewardship, and sustainable development, and each of these strategies are advanced for each of them regarding key resource requirements and their contributions to sustained competitive advantage.
Abstract: Historically, management theory has ignored the constraints imposed by the biophysical (natural) environment. Building upon resource-based theory, this article attempts to fill this void by proposing a natural-resource-based view of the firm—a theory of competitive advantage based upon the firm's relationship to the natural environment. It is composed of three interconnected strategies: pollution prevention, product stewardship, and sustainable development. Propositions are advanced for each of these strategies regarding key resource requirements and their contributions to sustained competitive advantage.

902 citations

Journal ArticleDOI
TL;DR: In this article, the authors identify the underlying factors of supply chain integration in European firms with particular emphasis on the role of information sharing and interorganizational collaboration, and find that European firms are starting to be aware of the strategic importance of integration across the boundaries of the supply chain.
Abstract: Purpose – The major goal of this study was to identify the underlying factors of supply chain integration in European firms with particular emphasis on the role of information sharing and interorganizational collaboration.Design/methodology/approach – In order to get an overall view of the state of supply chain integration in European firms, a mail survey was done to investigate the extent and nature of supply chain integration in 149 companies. Using statistical analysis, the study attempts to comprehend if increasing levels of the intensity of supply chain integration show concomitant rise of operational performance.Findings – European firms are starting to be aware of the strategic importance of integration across the boundaries of the supply chain. Both correlation analyses and multiple regression analyses have clearly shown that supply chain integration affects operational performance and the degree of integration also influences cost and efficiency. An interesting and surprising finding from our sur...

434 citations

Journal ArticleDOI
TL;DR: It is apparent that an explicit examination and optimisation of the cost of capital has been missing so far in research regarding financial flows in supply chains, so a conceptual framework and a mathematical model of “Supply Chain Finance" is proposed.
Abstract: Issues related to flows of goods and information are frequently discussed in the logistics and Supply Chain Management literature. But, only few contributions are exploring the financial flows associated with supply chains. This article reviews the state-of-the-art of research regarding financial flows in supply chains. In doing so, it becomes apparent that an explicit examination and optimisation of the cost of capital has been missing so far. In order to close this gap, a conceptual framework and a mathematical model of “Supply Chain Finance” is proposed.

326 citations

Posted Content
TL;DR: In this paper, the authors verify the technical and economic feasibility of regular container transport along the Northern Sea Route (NSR) by adopting a model schedule between Shanghai and Hamburg, and analyze the relative costs of various axes in the Asia-Europe transport network.
Abstract: Since the beginning of the 20th century, the principal commercial maritime routes have changed very little. With global warming, the Northern Sea Route (NSR) has opened up as a possible avenue of trade in containerized products between Asia and Europe. This paper verifies the technical and economic feasibility of regular container transport along the NSR. By adopting a model schedule between Shanghai and Hamburg, we are able to analyze the relative costs of various axes in the Asia–Europe transport network, including the NSR. While shipping through the Suez Canal is still by far the least expensive option, the NSR and Trans-Siberian Railway appear to be roughly equivalent second-tier alternatives.

188 citations