Generalized Centrifugal Force Model for Pedestrian Dynamics

A spatially continuous force-based model for simulating pedestrian dynamics is introduced which includes an elliptical volume exclusion of pedestrians. We discuss the phenomena of oscillations and overlapping which occur for certain choices of the forces. The main intention of this work is the quantitative description of pedestrian movement in several geometries. Measurements of the fundamental diagram in narrow and wide corridors are performed. The results of the proposed model show good agreement with empirical data obtained in controlled experiments.Comment: 10 pages, 14 figures, accepted for publication as a Regular Article in Physical Review E. This version contains minor change

Kan Strategisch Human resource Management (veel) Beter? Een spagaat tussen theorie en praktijk

Nederlandse werknemers behoren tot de meest tevreden werknemers van Europa, als we afgaan op de onderzoeken naar werktevredenheid van bijvoorbeeld Effectory of European Motivation Index. Scores voor ons land van rond de 70% worden al jaren opgetekend (2007: 68%, 2008: 69%, 2009: 68%) in brede arbeidssatisfactie surveys. Alleen Zweden lijkt het substantieel (2009: 75%) beter te doen dan ons land. Veenhoven toonde reeds eerder aan dat de levenstevredenheid in ons land eveneens op een hoog niveau ligt (gemiddeld 7.51 op een tienpunt schaal), waarbij ons land alleen Zweden (7.52) en Zwitserland (7.95) voor moet laten gaan (Veenhoven, 2002; World Database on Happiness, 2002; data voor Nederland, 1990) . Ons land kent een hoge arbeidsproductiviteit als we het bruto binnenlands product per gewerkt uur vergelijken met andere landen. Alleen Frankrijk, België en Ierland leken het in het afgelopen decennium beter te doen (CBS, 2006). Wordt gekeken naar het BBP per hoofd van de bevolking, dan legt ons land het af tegen flink wat andere landen, omdat het aantal gewerkte uren per werknemer (1354 uur) bij ons lager is dan in de twintig andere landen waarmee vergeleken wordt. Dit is onder meer het gevolg van een hoogontwikkelde deeltijdfactor, waarmee ons land zich onderscheidt van andere landen

Increasing weaning age of piglets from 4 to 7 weeks reduces stress, increases post-weaning feed intake but does not improve intestinal functionality

This study tested the hypothesis that late weaning and the availability of creep feed during the suckling period compared with early weaning, improves feed intake, decreases stress and improves the integrity of the intestinal tract. In this study with 160 piglets of 16 litters, late weaning at 7 weeks of age was compared with early weaning at 4 weeks, with or without creep feeding during the suckling period, on post-weaning feed intake, plasma cortisol (as an indicator of stress) and plasma intestinal fatty acid binding protein (I-FABP; a marker for mild intestinal injury) concentrations, intestinal morphology, intestinal (macro)molecular permeability and intestinal fluid absorption as indicators of small intestinal integrity. Post-weaning feed intake was similar in piglets weaned at 4 weeks and offered creep feed or not, but higher (P <0.001) in piglets weaned at 7 weeks with a higher (P <0.05) intake for piglets offered creep feed compared with piglets from whom creep feed was witheld. Plasma cortisol response at the day of weaning was lower in piglets weaned at 7 weeks compared with piglets weaned at 4 weeks, and creep feed did not affect cortisol concentration. Plasma I-FABP concentration was not affected by the age of weaning and creep feeding. Intestinal (macro)molecular permeability was not affected by the age of weaning and creep feeding. Both in uninfected and enterotoxigenic Escherichia coli-infected small intestinal segments net fluid absorption was not affected by the age of weaning or creep feeding. Creep feeding, but not the age of weaning, resulted in higher villi and increased crypt depth. In conclusion, weaning at 7 weeks of age in combination with creep feeding improves post-weaning feed intake and reduces weaning stress but does not improve functional characteristics of the small intestinal mucos

Medication Management in Pediatric Chronic Illness: Should Patient Anxiety be Considered?

Introduction: There is growing support that psychological symptoms can impact various aspects of disease, well-being, and medical treatment for those with a chronic illness like Crohn’s disease (CD). Yet, almost no studies have examined whether psychological symptoms can influence management or efficacy of patient medication regimens. The aims of this project were to examine whether anxiety predicted pediatric patients’ level of medication management, medication prescription changes, and corticosteroid prescription and duration. Method: A total of 105 pediatric patients ages 8-18 (M=14.5, SD=2.3) completed a validated anxiety questionnaire during a GI office visit (baseline). Prescribed IBD medications were recorded for the subsequent year, including changes (i.e., additions, discontinuations, switches) and corticosteroid prescription duration. Disease activity scores were generated at baseline and 12 months. Logistic and Poisson regressions were used to ascertain the predictive value of anxiety for medication treatment level and frequency of prescription changes. A Pearson correlation was conducted to examine the relationship between anxiety and prospective duration of systemic corticosteroid prescription. Results: Anxiety symptoms did not predict a higher level of medication treatment, but did show a trend in predicting a greater frequency of total medication changes over the 12-month study period (p=.07). More specifically, patient-reported anxiety symptoms were significantly predictive of medication switches within the same drug class (pp Discussion: This study is among the first to explore whether psychological symptoms predict multiple aspects of medication management for a chronic illness sample. Findings suggest that physicians should assess for psychological distress, be aware of overlapping physical symptoms associated with CD and anxiety, and treat symptoms holistically. Further empirical investigations are warranted to examine the interplay between emotional symptoms and medication management

Modeling Decentralized Organizational Change in Honeybee Societies

Multi-agent organizations in dynamic environments, need to have the ability to adapt to environmental changes to ensure a continuation of proper functioning. Such adaptations can be made through a centralized decision process or come from the individuals within the organization. In the domain of social insects, such as honeybees and wasps, organizations are known to adapt in a decentralized fashion to environmental changes. An organizational model for decentralized organizational change is presented that can aid in analyzing and designing such organizations. The model is specified by dynamic properties at different aggregation levels. At the lowest level such properties characterize the behavior of individual roles, which can be related to higher level properties that express important elements such as survival of an organization. A honeybee colony is used as a case study

Constant net-time headway as key mechanism behind pedestrian flow dynamics

We show that keeping a constant lower limit on the net-time headway is the key mechanism behind the dynamics of pedestrian streams. There is a large variety in flow and speed as functions of density for empirical data of pedestrian streams, obtained from studies in different countries. The net-time headway however, stays approximately constant over all these different data sets. By using this fact, we demonstrate how the underlying dynamics of pedestrian crowds, naturally follows from local interactions. This means that there is no need to come up with an arbitrary fit function (with arbitrary fit parameters) as has traditionally been done. Further, by using not only the average density values, but the variance as well, we show how the recently reported stop-and-go waves [Helbing et al., Physical Review E, 75, 046109] emerge when local density variations take values exceeding a certain maximum global (average) density, which makes pedestrians stop.Comment: 7 pages, 7 figure

Pedestrian flows in bounded domains with obstacles

In this paper we systematically apply the mathematical structures by time-evolving measures developed in a previous work to the macroscopic modeling of pedestrian flows. We propose a discrete-time Eulerian model, in which the space occupancy by pedestrians is described via a sequence of Radon positive measures generated by a push-forward recursive relation. We assume that two fundamental aspects of pedestrian behavior rule the dynamics of the system: On the one hand, the will to reach specific targets, which determines the main direction of motion of the walkers; on the other hand, the tendency to avoid crowding, which introduces interactions among the individuals. The resulting model is able to reproduce several experimental evidences of pedestrian flows pointed out in the specialized literature, being at the same time much easier to handle, from both the analytical and the numerical point of view, than other models relying on nonlinear hyperbolic conservation laws. This makes it suitable to address two-dimensional applications of practical interest, chiefly the motion of pedestrians in complex domains scattered with obstacles.Comment: 25 pages, 9 figure