The distribution-free newsboy problem with resalable returns

We study the case of a catalogue/internet mail order retailer selling seasonal productsand receiving large numbers of commercial returns. Returned products arriving beforethe end of the selling season can be resold if there is sufficient demand. A single orderis placed before the season starts. Excess inventory at the end of the season is salvagedand all demands not met directly are lost. Since little historical information is available,it is impossible to determine the shape of the distribution of demand. Therefore, weanalyze the distribution-free newsboy problem with returns, in which only the mean andvariance of demand are assumed to be known. We derive a simple closed-form expressionfor the distribution-free order quantity, which we compare to the optimal order quantities whengross demand is assumed to be normal, lognormal or uniform. We find that the distribution-freeorder rule performs well in most realistic cases.inventory;product returns;distribution-free newsboy problem

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

Measurement of Electron-Optical Parameters for High-Resolution Electron Microscopy Image Interpretation

A method is presented to measure various electron-optical parameters needed for high-resolution electron microscopy image interpretation with high accuracy. The method is based on the measurement of a series of beam-tilt induced image displacements. The displacements are calculated via cross-correlation of the images, and subsequently fitted to a third-order polynomal in the beam tilt. From two series of images (using the x and y beam tilt coils), the spherical aberration constant of the microscope can be measured, as well as the current values of defocus, beam tilt and astigmatism. The spherical aberration constant of three Philips microscopes is measured with a precision better than 1 %, apart from calibration errors.The misalignment in the reference image (i.e. without induced beam tilt) can be measured with an absolute accuracy of 0.05 mrad, while the accuracy in the measured defocus value is 5 nm (at a magnification of 250,000). A computer is used to direct the experiments via remote control of the microscope and perform fast image processing to calculate the cross-correlations

Naar een analytische stratificatiesociologie. Over klasse, status en ongelijkheid

Een van de hoofdvragen van de sociologie richt zich op de oorzaken en gevolgen van maatschappelijke ongelijkheden. Wij betogen dat de sociologie vanwege twee samenhangende problemen tekortschiet in de beantwoording van die vraag. Ten eerste wordt het door Weber uitgewerkte verschil tussen stratificatie in het economische domein (‘klasse’) en stratificatie in het culturele domein (‘status’) veronachtzaamd. Ten tweede richt stratificatieonderzoek zich voornamelijk op het bieden van statistische in plaats van theoretische verklaringen. Daardoor maakt onderzoek niet goed duidelijk of en hoe klassenverschillen en statusverschillen leiden tot 1) ongelijkheid in het economische domein, 2) intergenerationele reproductie van stratificatie, en 3) verschillende denk- voel- en handelingsrepertoires. Om deze problemen op te lossen werken we een alternatieve analytisch-sociologische onderzoeksaanpak uit. We illustreren de waarde van deze aanpak door uitkomsten van bestaande stratificatiestudies kritisch te bespreken. Het artikel sluit af met de implicaties van de hier gepropageerde analytische stratificatiesociologie voor vervolgonderzoek

Aligning order picking methods, incentive systems, and regulatory focus to increase performance

A unique controlled field experiment investigates order picking performance (in terms of productivity and quality). We examined three manual picker-to-parts order picking methods (parallel, zone, and dynamic zone picking) under two different incentive systems (competition- based versus cooperation-based) for pickers with different regulatory foci (prevention-focus versus promotion-focus). The study was carried out in a warehouse erected especially for the purposes of order picking research. Our results show that when using a parallel picking method a competition- based incentive system increases productivity and quality compared to a cooperation-based incentive system, and that when using a zone picking method it is more productive to use a cooperation- based incentive system. This pattern of results was especially pronounced for pickers with a dominant promotion focus. Dominantly prevention focused pickers, however, were more productive with a cooperation-based incentive system, irrespective of the picking method. Additionally, a cooperation-based incentive system delivered a low quality performance in zone picking, but a high quality performance in dynamic zone picking. The analyses demonstrate that by aligning order picking methods, incentive systems and regulatory focus, warehouses can improve productivity and quality, and reduce wage costs by up to 20%

Moreel conservatisme en autoritarisme theoretisch en methodisch ontward

This article demonstrates that studies in political sociology are flawed, because they fail to distinguish between moral conservatism/progressiveness and authoritarianism/libertarianism. Such a distincti

Weerstand tegen vrijhandel: niet economisch, maar cultureel

Bezwaren tegen vrijhandelsverdragen komen niet voort uit een zwakke economische positie van laagopgeleiden, maar uit een verschil in cultureel kapitaal. Herverdeling van de economische vruchten van vrijhandel zal het enthousiasme voor een verdrag als TTIP daarom niet vergroten