Performance Approximation and Design of Pick-and-Pass Order Picking Systems

In this paper, we discuss an approximation method based on G/G/m queuing network modeling using Whitt’s (1983) queuing network analyzer to analyze pick-and-pass order picking systems. The objective of this approximation method is to provide an instrument for obtaining rapid performance estimates (such as order lead time and station utilization) of the order picking system. The pick-and-pass system is decomposed into conveyor pieces and pick stations. Conveyor pieces have a constant processing time, whereas the service times at a pick station depend on the number of order lines in the order to be picked at the station, the storage policy at the station, and the working methods. Our approximation method appears to be sufficiently accurate for practical purposes. It can be used to rapidly evaluate the effects of the storage methods in pick stations, the number of order pickers at stations, the size of pick stations, the arrival process of customer orders, and the impact of batching and splitting orders on system performance.simulation;warehousing;order picking;queuing network;pick-and-pass

Stedelijke criminaliteit en rechtshandhaving in het verleden. Een greep uit recent historisch onderzoek

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De verhouding politie-bevolking in historisch perspectief: wederzijdse afhankelijkheid en stilzwijgende contracten

This article explores police-citizens relations in the 19th- and early-20th-centuries and attempts to demonstrate that these were not as unequivocal as is commonly assumed. While historians approach the modern police as an instrument of coercive state control imposed 'from above' onto a passive population, current policy debates tend to assume that police-citizen relations were friendly and that cops learned from citizens, leading to well-informed and neighbourhood-sensitive policing. I argue that police-citizen relations were not friendly, but all about the negotation of 'tacit contracts' between both parties, that allowed the police to carry out their duties within the boundaries of public tolerance, and the public to take all sorts of small conflicts and demands for aid and assistance to the police. This explains why police intervention was never merely repressive: in order to preserve these precious 'contracts', the police operated selectively, acting only against certain groups and offences, and watching particular city areas

How to Organise Return Handling

Already for a long time retailers take back products. In this paper we explore the factors contributing to the decision of combining vs. separating inbound and outbound flows during the return handling process. We do so through a comparative analysis of the operations in nine retailer warehouses, which can be divided in three groups: food retailers, department stores and mail order companies. We identify both aggravating factors and facilitating actions for return handling. Furthermore, we bring about recommendations for practice. At the end we put forward propositions that are useful in feeding studies on return handling efficiency. In particular, we conjecture over the impact that return volume and product diversity have on the decision for combining vs. separating the reverse and forward flows.product returns;case studies;Retailing;inbound and outbound flows;return handling

Worrying and rumination are both associated with reduced cognitive control

Persistent negative thought is a hallmark feature of both major depressive disorder and generalized anxiety disorder. Despite its clinical significance, little is known about the underlying mechanisms of persistent negative thought. Recent studies suggest that reduced cognitive control might be an explanatory factor. We investigated the association between persistent negative thought and switching between internal representations in working memory, using the internal shift task (IST). The IST was administered to a group of undergraduates, classified as high-ruminators versus low-ruminators, or high-worriers versus low-worriers. Results showed that high-ruminators and high-worriers have more difficulties to switch between internal representations in working memory as opposed to low-ruminators and low-worriers. Importantly, results were only significant when the negative stimuli used in the IST reflected personally relevant worry themes for the participants. The results of this study indicate that rumination and worrying are both associated with reduced cognitive control for verbal information that is personally relevant

Supply-Chain Culture Clashes in Europe. Pitfalls in Japanese Service Operations

Japanese companies value service and quality highly and they put much effort in realising this. However, survey research carried out in 2001 among senior managers of Japanese logistics companies in the Netherlands, indicated that these efforts do not result in significant performance differences compared to western companies. In this exploratory paper, we report of company visits and interviews with managers of Japanese logistics companies in Western Europe. They described a clash of cultures underlying their operations, prohibiting them from achieving performance excellence. The causes focus around two key factors: the unique concept of Japanese service, based on future rewards which are absent in Western Europe; different employment circumstances in Western Europe, which make Japanese human resource management ineffective, and the Japanese career development system which makes that Japanese managers do not always have the right focus in their job abroad. We conclude that Japanese subsidiaries in Western Europe should keep on nourishing their uneq

Predicted band structures of III-V semiconductors in wurtzite phase

While non-nitride III-V semiconductors typically have a zincblende structure, they may also form wurtzite crystals under pressure or when grown as nanowhiskers. This makes electronic structure calculation difficult since the band structures of wurtzite III-V semiconductors are poorly characterized. We have calculated the electronic band structure for nine III-V semiconductors in the wurtzite phase using transferable empirical pseudopotentials including spin-orbit coupling. We find that all the materials have direct gaps. Our results differ significantly from earlier {\it ab initio} calculations, and where experimental results are available (InP, InAs and GaAs) our calculated band gaps are in good agreement. We tabulate energies, effective masses, and linear and cubic Dresselhaus zero-field spin-splitting coefficients for the zone-center states. The large zero-field spin-splitting coefficients we find may lead to new functionalities for designing devices that manipulate spin degrees of freedom

Attentional avoidance of high-fat food in unsuccessful dieters

Using the exogenous cueing task, this study examined whether restrained and disinhibited eaters differ in their orientation of attention towards and their difficulty to disengage from high versus low-fat food pictures in a relatively short (500 ms) and a long presentation format (1500 ms). Overall, participants in the 500 ms condition showed a tendency to direct attention away from high-fat food pictures compared to neutral pictures. No differential pattern was evident for the 1500 ms condition. Correlational analysis revealed that reduced engagement with high-fat food was particularly pronounced for disinhibited eaters. Although in the short term this seems an adaptive strategy, it may eventually become counterproductive, as it could hinder habituation and learning to cope with seductive characteristics of high-fat food. (C) 2010 Elsevier Ltd. All rights reserved

Performance Approximation and Design of Pick-and-Pass Order Picking Systems

In this paper, we discuss an approximation method based on G/G/m queuing network modeling using Whitt’s (1983) queuing network analyzer to analyze pick-and-pass order picking systems. The objective of this approximation method is to provide an instrument for obt