Dynamic actions on bridge slabs due to heavy vehicle impact on roadside barriers

The use of roadside safety barriers in Italy has changed in recent years: the number of installed devices has increased, and so have their stiffness and resistance. These changes were necessary because early barrier design was inadequate to contain and redirect heavy vehicles. The change in barrier design led to an increase in stiffness and resistance; consequently, the action transferred to the structure by the device increased. The need for resistance on the bridge slabs can be too high because the peculiar action of the roadside barriers was not adequately taken into account in the oldest bridge design codes. In addition, characterizing the actions transferred to the bridge slab is difficult because of the dynamic nature of vehicle impacts on roadside barriers. Given the impossibility of performing a full-scale laboratory test for every bridge deck, the use of computational mechanics applied to dynamic impact/interaction problems is one of the best ways to establish these actions in the project phase. Research was conducted into the use of a three-dimensional finite element model of the bridge slab-barrier-vehicle system to perform a numerical simulation of the impact, according to the procedure used for the roadside barrier homologation crash test, described in the European Standard EN 1317

Impurity assisted nanoscale localization of plasmonic excitations in graphene

The plasmon modes of pristine and impurity doped graphene are calculated, using a real-space theory which determines the non-local dielectric response within the random phase approximation. A full diagonalization of the polarization operator is performed, allowing the extraction of all its poles. It is demonstrated how impurities induce the formation of localized modes which are absent in pristine graphene. The dependence of the spatial modulations over few lattice sites and frequencies of the localized plasmons on the electronic filling and impurity strength is discussed. Furthermore, it is shown that the chemical potential and impurity strength can be tuned to control target features of the localized modes. These predictions can be tested by scanning tunneling microscopy experiments.Comment: 5 pages, 4 figure

Model and design of a double frequency piezoelectric resonator

A novel design of a multifrequency mechanical resonator with piezoelectric materials for energy harvesting is presented. The electromechanical response is described by a finite element model, which predicts the output voltage and the generated powe

Direct Evidence on Risk Attitudes and Migration

Geographic mobility is important for the functioning of labor markets because it brings labor resources to where they can be most efficiently used. It has long been hypothesized that individuals' migration propensities depend on their attitudes towards risk, but the empirical evidence, to the extent that it exists, has been indirect. In this paper, we use newly available data from the German Socio-Economic Panel to measure directly the relationship between migration propensities and attitudes towards risk. We find that individuals who are more willing to take risks are more likely to migrate between labor markets in Germany. This result is robust to stratifying by age, sex, education, national origin, and a variety of other demographic characteristics, as well as to the level of aggregation used to define geographic mobility. The effect is substantial relative to the unconditional migration propensity and compared to the conventional determinants of migration. We also find that being more willing to take risks is more important for the extensive than for the intensive margin of migration.Migration, attitudes, risk

Rebâtir la confiance après une grève de longue durée : est-ce possible ?

Cette étude a pour but d’analyser les facteurs contribuant à bâtir la confiance entre employés syndiqués et cadres après une grève de longue durée dans une succursale bancaire. Des entrevues semi-dirigées auprès de treize employés et cinq cadres, des observations et une analyse documentaire ont servi à déterminer ces facteurs. Ces derniers ont été analysés à la lumière des écrits scientifiques pour établir un modèle relationnel et analyser la situation vécue par les membres de l’organisation à l’étude.The effects of strikes have always preoccupied industrial relations’ scholars and practitioners. Even though statistically, there have been fewer strikes in Quebec during the last few years, they have not been of lesser interest. The most recent strikes have been more apparent because of their longer duration. This study discusses trust between managers and unionized employees who have returned to work after a fourteen-month strike. The objective is to better understand the phenomenon of trust in a situation of organizational conflict and, more precisely, to analyze the factors that contribute to re-establishing trust between union employees and managers following this major conflict.A few theoretical concepts about trust help us understand the basic elements needed to produce collaborative relationships. Among other things, categories of trust established by Lewicki and Bunker (1996) as well as Zucker (1986) are presented to help make a better judgment with regard to the different types of relationships and to understand the way in which they present themselves in particular situations. This section ends with an overview of the authors’ theoretical perspective, an institutional approach, which makes reference to Powell and Dimaggio’s (1991) framework.Because of the difficulty to access multiple companies affected by a strike, a qualitative case study was conducted. Thirteen union employees and five managers chosen randomly among each job category from a total of forty-six employees make up the sample. They were interviewed during semi-structured interviews six months following the end of the strike. Observations about individual behaviour during the interview period were also taken into consideration. An analysis of internal documents from the organization helped bring out factual information about the state of the relationship between the two groups before, during and after the strike. It is the use of these three traditional methods that helped construct the case presented. Not only does it explain the events surrounding the conflict by using a balanced approach including information obtained from union employees and company managers, but it also includes references to articles published in local newspapers to give a temporality and a sense of place to the events.Subsequently, the authors undertake a discussion about ways to reconstruct trust among the parties. Tables detailing the factors that can contribute to reconstructing trust according to each party are presented with representative quotes from the semi-structured interviews. In total, three common factors were raised—communication, material investments and human investments. Communication is a central concept, but it also includes its share of complexities because the simple act of communicating is not sufficient. Even if, in basic terms, material investments are perceived as advantages, they are not in practice, according to the literature on this subject. Human investments can also bring new dynamics to a company, but cannot be done to the detrimental need of removing existing personnel. To these factors, the union employees add six additional ones including desire, supervision, recognition and appreciation, respect of the collective agreement and the importance of not resorting to outsourcing. The managers also came up with four additional factors—responsibility, comprehension, company vision and the importance of providing projects to union employees. All these factors are systematically analyzed in the article in direct relation to the written scientific and theoretical literature on these subjects.In light of this analysis, it is possible to establish a relationship between these factors and a hierarchy of their importance that can serve to explore the possibility of reestablishing trust within the organization. These relationships and this hierarchy are presented in an illustration which summarizes the study. Explanations about its creation and the way to interpret it are also included. It is important, however, to note that although the study reveals a number of important factors needed to study trust, it has its limitations which can only be rectified by studying each factor in a distinct fashion and by weighing each one individually during subsequent research.In conclusion, this research demonstrates the difficulty to establish trust within an organization because the company does not recognize the union’s presence and its role. The company is rather searching to achieve its own objectives without taking the values and interests of its employees into account as well as those of the trade union. From a theoretical point of view, the study helps identify the limitations to trust relationships between various groups of employees, the effects of strikes on returning to work and of trust in the after-strike context. Paths for future research are explored. It is suggested to replicate the study in an institution in the same field or in different fields to open the door to the possibility of generalization. Secondly, it is suggested to weigh the factors to find out which ones would have the greatest impact on the creation of trust. And, finally, measuring the level of trust that really exists between the parties would be beneficial in understanding the scope of the division which separates them.El objetivo de este estudio es de analizar los factores que contribuyen a construir la confianza entre empleados sindicalizados y directivos después de una huelga de larga duración en una sucursal bancaria. Para determinar estos factores, se utilizaron entrevistas semi-dirigidas con trece empleados y cinco cuadros, observaciones directas y un análisis documentario. Dichos factores fueron analizados a la luz de escritos científicos para establecer un modelo racional y analizar la situación vivida por los miembros de la organización al estudio