Science Bound, Spring 2012, Vol. 11, no. 2

Science Bound is Iowa State University’s premier pre-college program to increase the number of ethnically diverse Iowa students who pursue ASTEM (agricultural, scientific, technical, engineering and mathematics) degrees. The program draws students with potential from middle and high schools.

Science Bound, Spring 2011, Vol. 10, no. 2

Science Bound is Iowa State University’s premier pre-college program to increase the number of ethnically diverse Iowa students who pursue ASTEM (agricultural, scientific, technical, engineering and mathematics) degrees. The program draws students with potential from middle and high schools.

Science Bound, Fall 2011, Vol. 11, no. 1

Science Bound is Iowa State University’s premier pre-college program to increase the number of ethnically diverse Iowa students who pursue ASTEM (agricultural, scientific, technical, engineering and mathematics) degrees. The program draws students with potential from middle and high schools.

Science Bound, Spring 2013, Vol. 12, no. 1

Science Bound is Iowa State University’s premier pre-college program to increase the number of ethnically diverse Iowa students who pursue ASTEM (agricultural, scientific, technical, engineering and mathematics) degrees. The program draws students with potential from middle and high schools.

Behavioural queueing : cellular automata and a laboratory experiment

Dans cette thèse, nous étudions les aspects comportementaux d'agents qui interagissent dans des systèmes de files d'attente à l'aide de modèles de simulation et de méthodologies expérimentales. Chaque période les clients doivent choisir un prestataire de servivce. L'objectif est d'analyser l'impact des décisions des clients et des prestataires sur la formation des files d'attente. Dans un premier cas nous considérons des clients ayant un certain degré d'aversion au risque. Sur la base de leur perception de l'attente moyenne et de la variabilité de cette attente, ils forment une estimation de la limite supérieure de l'attente chez chacun des prestataires. Chaque période, ils choisissent le prestataire pour lequel cette estimation est la plus basse. Nos résultats indiquent qu'il n'y a pas de relation monotone entre le degré d'aversion au risque et la performance globale. En effet, une population de clients ayant un degré d'aversion au risque intermédiaire encoure généralement une attente moyenne plus élevée qu'une population d'agents indifférents au risque ou très averses au risque. Ensuite, nous incorporons les décisions des prestataires en leur permettant d'ajuster leur capacité de service sur la base de leur perception de la fréquence moyenne d'arrivées. Les résultats montrent que le comportement des clients et les décisions des prestataires présentent une forte "dépendance au sentier". En outre, nous montrons que les décisions des prestataires font converger l'attente moyenne pondérée vers l'attente de référence du marché. Finalement, une expérience de laboratoire dans laquelle des sujets jouent le rôle de prestataire de service nous a permis de conclure que les délais d'installation et de démantèlement de capacité affectent de manière significative la performance et les décisions des sujets. En particulier, les décisions du prestataire, sont influencées par ses commandes en carnet, sa capacité de service actuellement disponible et les décisions d'ajustement de capacité qu'il a prises, mais pas encore implémentées. - Queuing is a fact of life that we witness daily. We all have had the experience of waiting in line for some reason and we also know that it is an annoying situation. As the adage says "time is money"; this is perhaps the best way of stating what queuing problems mean for customers. Human beings are not very tolerant, but they are even less so when having to wait in line for service. Banks, roads, post offices and restaurants are just some examples where people must wait for service. Studies of queuing phenomena have typically addressed the optimisation of performance measures (e.g. average waiting time, queue length and server utilisation rates) and the analysis of equilibrium solutions. The individual behaviour of the agents involved in queueing systems and their decision making process have received little attention. Although this work has been useful to improve the efficiency of many queueing systems, or to design new processes in social and physical systems, it has only provided us with a limited ability to explain the behaviour observed in many real queues. In this dissertation we differ from this traditional research by analysing how the agents involved in the system make decisions instead of focusing on optimising performance measures or analysing an equilibrium solution. This dissertation builds on and extends the framework proposed by van Ackere and Larsen (2004) and van Ackere et al. (2010). We focus on studying behavioural aspects in queueing systems and incorporate this still underdeveloped framework into the operations management field. In the first chapter of this thesis we provide a general introduction to the area, as well as an overview of the results. In Chapters 2 and 3, we use Cellular Automata (CA) to model service systems where captive interacting customers must decide each period which facility to join for service. They base this decision on their expectations of sojourn times. Each period, customers use new information (their most recent experience and that of their best performing neighbour) to form expectations of sojourn time at the different facilities. Customers update their expectations using an adaptive expectations process to combine their memory and their new information. We label "conservative" those customers who give more weight to their memory than to the xiv Summary new information. In contrast, when they give more weight to new information, we call them "reactive". In Chapter 2, we consider customers with different degree of risk-aversion who take into account uncertainty. They choose which facility to join based on an estimated upper-bound of the sojourn time which they compute using their perceptions of the average sojourn time and the level of uncertainty. We assume the same exogenous service capacity for all facilities, which remains constant throughout. We first analyse the collective behaviour generated by the customers' decisions. We show that the system achieves low weighted average sojourn times when the collective behaviour results in neighbourhoods of customers loyal to a facility and the customers are approximately equally split among all facilities. The lowest weighted average sojourn time is achieved when exactly the same number of customers patronises each facility, implying that they do not wish to switch facility. In this case, the system has achieved the Nash equilibrium. We show that there is a non-monotonic relationship between the degree of risk-aversion and system performance. Customers with an intermediate degree of riskaversion typically achieve higher sojourn times; in particular they rarely achieve the Nash equilibrium. Risk-neutral customers have the highest probability of achieving the Nash Equilibrium. Chapter 3 considers a service system similar to the previous one but with risk-neutral customers, and relaxes the assumption of exogenous service rates. In this sense, we model a queueing system with endogenous service rates by enabling managers to adjust the service capacity of the facilities. We assume that managers do so based on their perceptions of the arrival rates and use the same principle of adaptive expectations to model these perceptions. We consider service systems in which the managers' decisions take time to be implemented. Managers are characterised by a profile which is determined by the speed at which they update their perceptions, the speed at which they take decisions, and how coherent they are when accounting for their previous decisions still to be implemented when taking their next decision. We find that the managers' decisions exhibit a strong path-dependence: owing to the initial conditions of the model, the facilities of managers with identical profiles can evolve completely differently. In some cases the system becomes "locked-in" into a monopoly or duopoly situation. The competition between managers causes the weighted average sojourn time of the system to converge to the exogenous benchmark value which they use to estimate their desired capacity. Concerning the managers' profile, we found that the more conservative Summary xv a manager is regarding new information, the larger the market share his facility achieves. Additionally, the faster he takes decisions, the higher the probability that he achieves a monopoly position. In Chapter 4 we consider a one-server queueing system with non-captive customers. We carry out an experiment aimed at analysing the way human subjects, taking on the role of the manager, take decisions in a laboratory regarding the capacity of a service facility. We adapt the model proposed by van Ackere et al (2010). This model relaxes the assumption of a captive market and allows current customers to decide whether or not to use the facility. Additionally the facility also has potential customers who currently do not patronise it, but might consider doing so in the future. We identify three groups of subjects whose decisions cause similar behavioural patterns. These groups are labelled: gradual investors, lumpy investors, and random investor. Using an autocorrelation analysis of the subjects' decisions, we illustrate that these decisions are positively correlated to the decisions taken one period early. Subsequently we formulate a heuristic to model the decision rule considered by subjects in the laboratory. We found that this decision rule fits very well for those subjects who gradually adjust capacity, but it does not capture the behaviour of the subjects of the other two groups. In Chapter 5 we summarise the results and provide suggestions for further work. Our main contribution is the use of simulation and experimental methodologies to explain the collective behaviour generated by customers' and managers' decisions in queueing systems as well as the analysis of the individual behaviour of these agents. In this way, we differ from the typical literature related to queueing systems which focuses on optimising performance measures and the analysis of equilibrium solutions. Our work can be seen as a first step towards understanding the interaction between customer behaviour and the capacity adjustment process in queueing systems. This framework is still in its early stages and accordingly there is a large potential for further work that spans several research topics. Interesting extensions to this work include incorporating other characteristics of queueing systems which affect the customers' experience (e.g. balking, reneging and jockeying); providing customers and managers with additional information to take their decisions (e.g. service price, quality, customers' profile); analysing different decision rules and studying other characteristics which determine the profile of customers and managers.

La "bientraitance", exploration du concept et essai d'utilisation en santé publique: une expérience à Fribourg (Suisse). ["Bientraitance": conceptual exploration and an example of its application in public health: an experience from Fribourg, Switzerland]

Since the year 2000, the concept of "bientraitance" (for which no equivalent term has yet emerged in either the English or German language) has gained widespread credence among educators, sociologists and health professionals in France and Belgium. This concept emphasizes a constructive approach to care and education rather than merely one of prevention of disasters. Applied in public health, and in particular to mental health promotion, the use of the concept of "bientraitance" can help promote both effectiveness and meaning in the design and planning of community interventions. The article presents an example of an intervention for children and adolescents in Fribourg, Switzerland. The underpinning hypothesis is that the children and youth groups (such as sports clubs, artistic and cultural associations, scouts and guides) represent largely untapped, or under-tapped, informal health resources with a favourable cost-effectiveness profile. "Bientraitance" criteria are used in selecting certain associations offering structured extracurricular group educational activities and collective out-of-school (or after school) programmes. Support is provided to the organisations selected for recruiting new members, in particular those with potentially lower levels of access, for example disabled children or new migrants. The results will be evaluated for the impact of participation in various out-of-school activities on health and health determinants from a prospective and comparative perspective. This paper shows how the concept of "bientraitance" can be useful in the development of a public health intervention.

Tels parents, tels enfants? L'utilisation de données de seconde main dans l'étude des influences politiques parentales en Suisse

''Like Parents, Like Children?'' Using Secondary Data in the Study of Parental Political Influence in Switzerland: This text is devoted to the intergenerational transmission of left-right ideological orientation. Using data from the Swiss Household Panel (www.swisspanel.ch), collected both directly and through intermediaries, it raises the question of the validity of second-hand information, which is discussed on several points. The article also shows that there is a strong long-term coherence between the ideological orientation of parents and their children. It also highlights the fact that the link is not the same for boys as for girls, and it varies between generations. Finally, it shows that strong upward social mobility, compared to the original environment, facilitates emancipation from parental ideology, social inertia being greater for downward and horizontal mobility. Ce texte est consacré à la transmission intergénérationnelle de l'orientation idéologique gauche-droite. Utilisant des données du Panel Suisse de Ménages (www.swisspanel.ch), collectées tant directement que par personnes interposées, il pose la question de la validité des informations de seconde main, qui est étudiée sur plusieurs points. L'article montre en outre qu'il existe à long terme une forte cohérence entre l'orientation idéologique des parents et de leurs enfants. Il met aussi en évidence que ce lien n'est pas la même auprès des garçons qu'auprès des filles, et qu'il varie entre les générations. Finalement, il montre qu'une forte ascension sociale par rapport au milieu d'origine facilite l'émancipation des orientations idéologiques parentales, l'inertie étant plus forte pour les trajectoires descendantes et horizontales.

Mise au point concernantl'utilisation du dosagede l'antigène carcino-embryonnaire (CEA)en clinique

The carcinoembryonic antigen (CEA) is a tumor marker defined by specific heterologous antisera. Elevated levels of circulating CEA have been detected by radioimmunoassay in 20-90 per cent of cases of colorectal carcinomas depending on the degree of tumor spread. The fact that elevation of CEA level can also be observed in other types of carcinomas and in several non malignant conditions greatly limit the value of the CEA test for the early diagnosis of colorectal carcinoma. Thus, the CEA assay should not be used as a screening test for cancer. Repeatecl CEA mesurements, however, appear to be of importance for the evaluation of tumor resection and the detection of tumor recurrence. The only localized tumors known to produce elevation of CEA above the levels observed in non malignant diseases are carcinomas of the large bowel and the pancreas. In carcinomas derived from other organs a marked increase of CEA level is always associated with the presence of distant metastasis. Therefore at the present time the clinical applications of the CEA radioimmunoassay should be limited to the differentiai diagnosis of patients with suspicion of primary colorectal or pancreatic carcinoma, to the detection of distant metastasis in other types of carcinomas and to the post operative follow up of patients who had elevated levels of CEA before surgery. Well-controlled studies are still needed to determine if therapeutic decisions based on CEA results can lead to improved survival.

Pratiques d'utilisation et d'appropriation d'un dispositif d'aide à l'insertion : le cas du contrat emploi-solidarité

C'est à travers l'analyse d'une politique publique d'aide à l'emploi (le contrat emploi solidarité) que nous avons exploré les mécanismes d'insertion professionnelle d'hommes et de femmes privés d'emploi. La sur-représentation des femmes dans ce dispositif, comme dans ceux les plus éloignés de l'emploi, nous a amené à inscrire notre raisonnement dans une problématique de rapports sociaux de sexe. C'est-à-dire que nous faisons l'hypothèse que les pratiques des opérateurs de terrain s'appuyant sur les assignations de sexe, produisent un traitement différencié des politiques d'insertion entre les hommes et les femmes. Celui-ci se caractérise notamment par la non prise en compte des difficultés et des besoins spécifiques des femmes et par une absence de novation dans les formations qui leur sont proposées. Les logiques institutionnelles ainsi à l'oeuvre contribuent implicitement à un renforcement des inégalités entre les sexes et à une reproduction de la division sexuelle du travail déjà observée sur le marché de l'emploi