Non-thermal radiation from a pulsar wind interacting with an inhomogeneous stellar wind

Binaries hosting a massive star and a non-accreting pulsar are powerful non-thermal emitters due to the interaction of the pulsar and the stellar wind. The winds of massive stars are thought to be inhomogeneous, which could have an impact on the non-thermal emission. We study numerically the impact of the presence of inhomogeneities or clumps in the stellar wind on the high-energy non-thermal radiation of high-mass binaries hosting a non-accreting pulsar. We compute the trajectories and physical properties of the streamlines in the shocked pulsar wind without clumps, with a small clump, and with a large one. This information is used to compute the synchrotron and inverse Compton emission from the non-thermal populations, accounting also for the effect of gamma-ray absorption through pair creation. A specific study is done for PSR B1259-63/LS2883. When stellar wind clumps perturb the two-wind interaction region, the associated non-thermal radiation in the X-ray band,of synchrotron origin, and in the GeV-TeV band, of inverse Compton origin, is affected by several effects: (i) strong changes in the the plasma velocity direction that result in Doppler boosting factor variations, (ii) strengthening of the magnetic field that mainly enhances the synchrotron radiation, (iii) strengthening of the pulsar wind kinetic energy dissipation at the shock, potentially available for particle acceleration, and (iv) changes in the rate of adiabatic losses that affect the lower energy part of the non-thermal particle population. The radiation above 100 GeV detected, presumably, during the post-periastron crossing of the Be star disc in PSR B1259-63/LS2883, can be roughly reproduced assuming that the crossing of the disc is modeled as the encounter with a large inhomogeneity.Comment: 13 pages, 12 figures, submitted to A&

Balancing Workload and Workforce Capacity in Lean Management: Application to Multi-Model Assembly Lines

While multi-model assembly lines are used by advanced lean companies because of their flexibility (different models of a product are produced in small lots and reach the customers in a short lead time), most of the extant literature on how to staff assembly lines focuses either on single-model lines or on mixed-model lines. The literature on multi-model lines is scarce and results given by current methods may be of limited applicability. In consequence, we develop a procedure to staff multi-model assembly lines while taking into account the principles of lean manufacturing. As a first approach, we replace the concepts of operation time and desired cycle time by their reciprocal magnitudes workload and capacity, and we define the dimensionless term of unit workload (load/capacity ratio) in order to avoid magnitudes related to time such as cycle time because, in practice, they might not be known. Next, we develop the necessary equations to apply this framework to a multi-model line. Finally, a piece of software in Python is developed, taking advantage of Google’s OR-Tools solver, to achieve an optimal multi-model line with a constant workforce and with each workstation performing the same tasks across all models. Several instances are tested to ensure the performance of this method

An accounting system to support process improvements: transition to lean accounting

From the last two decades of the 20th Century on, many companies have adopted production strategies that could be termed “lean manufacturing”. Lean team leaders state that traditional costing systems fail to properly assess their operational improvements and therefore ask for new cost accounting methods. The search for a new accounting paradigm has led to important applied research and several accounting methods. In this paper we are going to show the state of the art in costing techniques used in companies that adopt lean manufacturing practices and we will be presenting an additional costing method, based on Activity-Based Costing, intended to cast light on the operational improvements achieved in companies that are just starting a maturity path towards lean manufacturing. This article examines how the approach is applied in the context of a manufacturing company.Peer Reviewe

Wallenius Naive Bayes

Traditional event models underlying naive Bayes classifiers assume probability distributions that are not appropriate for binary data generated by human behaviour. In this work, we develop a new event model, based on a somewhat forgotten distribution created by Kenneth Ted Wallenius in 1963. We show that it achieves superior performance using less data on a collection of Facebook datasets, where the task is to predict personality traits, based on likes.Faculty of Applied Economics, University of Antwerp, Belgium; Department of Information, Operations & Management Sciences, NYU Stern School of Busines

First xiphosuran traceway in the middle Muschelkalk facies (Middle Triassic) of the Catalan Basin (NE Iberian Peninsula)

In the last decade, the first ichnoassamblages from the middle Muschelkalk facies (upper Anisian-middle Ladinian) of the Catalan Basin (NE Iberian Peninsula) have been discovered. Herein, the first xiphosuran trace fossils are described from the locality of Penya Rubí, a newly discovered ichnosite from the Catalan Basin. The finding opens a window into peri-Tethys ecosystems with coastal influence. The traceway is referred to the ichnogenus Kouphichnium, a locomotion trace attributed to xiphosurans. The traceway preserves telson grooves and different imprint morphologies from the various appendages. The traceway pattern and arrangement of the different traces suggest a crawling locomotion style. The sedimentology suggests a coastal zone with areas influenced by tides (intertidal flat). The morphological variations of the ichnites are correlated to substrate rheology, the locomotion of the tracemaker and environmental conditions

Exploració computacional i psicofísica de l'origen de les categories del color

Aquest article presenta un estudi sobre l'origen de les categories del color tan perceptualment com computacionalment. A partir d'un estudi previ que s'explica de manera detallada en el cos d'aquest article, s'ha generat un model computacionalment capaç d'assignar a cada punt d'una imatge la seva pertinença a cada una de les onze categories definides per B.Berlin i P.Kay. Aquest model es basa en la creació d'un conjunt de funcions el·líptiques que defineixen les fronteres de cada color. Al final de l'article es presenten els resultats obtinguts juntament amb la discussió i justificació corresponents.Este artículo presenta un estudio sobre el origen de las categorías del color tanto perceptualmente como computacionalmente. A partir de un estudio previo que se explica de forma detallada en el cuerpo de este artículo, se ha generado un modelo computacionalmente capaz de asignar a cada punto de una imagen su pertinencia a cada una de las once categorías definidas por B.Berlin y P.Kay. Este modelo se basa en la creación de un conjunto de funciones elípticas que definen las fronteras de cada color. Al final del artículo se presentan los resultados junto con la discusión y justificación correspondientes.This paper presents a study about the origin of both perceptual and computational color categories. This paper is based on a previous study explained in detail in the body of this article. The study presented on this paper has generated a computational model capable of assigning each point of an image to the category it belongs based on eleven defined by B.Berlin and P.Kay. This model is based on the description of a set of elliptic functions that define the boundaries of each color. Results along with discussion and corresponding justification are presented at the end of the article