A nonlinear vehicle-structure interaction methodology with wheel-rail detachment and reattachment

. A vehicle-structure interaction methodology with a nonlinear contact formulation based on contact and target elements has been developed. To solve the dynamic equations of motion, an incremental formulation has been used due to the nonlinear nature of the contact mechanics, while a procedure based on the Lagrange multiplier method imposes the contact constraint equations when contact occurs. The system of nonlinear equations is solved by an efficient block factorization solver that reorders the system matrix and isolates the nonlinear terms that belong to the contact elements or to other nonlinear elements that may be incorporated in the model. Such procedure avoids multiple unnecessary factorizations of the linear terms during each Newton iteration, making the formulation efficient and computationally attractive. A numerical example has been carried out to validate the accuracy and efficiency of the present methodology. The obtained results have shown a good agreement with the results obtained with the commercial finite element software ANSY

A 3-form Gauge Potential in 5D in connection with a Possible Dark Sector of 4D-Electrodynamics

We here propose a 5-dimensional {\bf Abelian gauge} model based on the mixing between a $U(1)$ potential and an Abelian 3-form field by means of a topological mass term. An extended covariant derivative is introduced to minimally couple a Dirac field to the $U(1)$ potential, while this same covariant derivative non-minimally couples the 3-form field to the charged fermion. A number of properties are discussed in 5D; in particular, the appearance of a topological fermionic current. A 4-dimensional reduced version of the model is investigated and, { \bf in addition to the $U(1)$ electric- and magnetic-sort of fields,} there emerges an extra set of electric- and magnetic-like fields which contribute a negative pressure and may be identified as a possible fraction of dark energy. The role of the topological fermionic current is also contemplated upon dimensional reduction from 5D to 4D. Other issues we present in 4 space-time dimensions are the emergence {\bf of a pseudo-scalar massive particle,} an extra massive neutral gauge boson,{\bf which we interpret as a kind of paraphoton}, and the calculation of spin- and velocity-dependent interparticle potentials associated to the exchange of the intermediate bosonic fields of the model.Comment: -- 30 pages -- L. P. R. Ospedal appears as a new co-author; modifications by inclusion of the gravitational sector and the attainment of a spin- and velocity-dependent potential as an application have been worked out in this Revised Versio

Supersymmetrization of the Radiation Damping

We construct a supersymmetrized version of the model to the radiation damping \cite{03} introduced by the present authors \cite{ACWF}. We dicuss its symmetries and the corresponding conserved Noether charges. It is shown this supersymmetric version provides a supersymmetric generalization of the Galilei algebra obtained in \cite{ACWF}. We have shown that the supersymmetric action can be splited into dynamically independent external and internal sectors.Comment: 9 page

Order and Disorder in AKLT Antiferromagnets in Three Dimensions

The models constructed by Affleck, Kennedy, Lieb, and Tasaki describe a family of quantum antiferromagnets on arbitrary lattices, where the local spin S is an integer multiple M of half the lattice coordination number. The equal time quantum correlations in their ground states may be computed as finite temperature correlations of a classical O(3) model on the same lattice, where the temperature is given by T=1/M. In dimensions d=1 and d=2 this mapping implies that all AKLT states are quantum disordered. We consider AKLT states in d=3 where the nature of the AKLT states is now a question of detail depending upon the choice of lattice and spin; for sufficiently large S some form of Neel order is almost inevitable. On the unfrustrated cubic lattice, we find that all AKLT states are ordered while for the unfrustrated diamond lattice the minimal S=2 state is disordered while all other states are ordered. On the frustrated pyrochlore lattice, we find (conservatively) that several states starting with the minimal S=3 state are disordered. The disordered AKLT models we report here are a significant addition to the catalog of magnetic Hamiltonians in d=3 with ground states known to lack order on account of strong quantum fluctuations.Comment: 7 pages, 2 figure

Procrastination is not only a “thief of time”, but also a thief of happiness: It buffers the beneficial effects of telework on well-being

This study draws on the affective events theory to understand how telework may influence workers’ well-being. Hence this study aimed to (1) analyze the indirect relationship between telework and well-being via daily micro-events, and (2) test whether procrastination would moderate this indirect effect. To test the goals, data was gathered from a sample of teleworkers in the IT sector (N=232). To analyze the data, a moderated mediation analysis was performed in SPSS with PROCESS macro. The results showed that micro-daily events mediated the positive relationship between telework and well-being; however, this relation was conditional upon the levels of workers’ levels of procrastination, that is, this link became weaker for those who were procrastinators. By highlighting the importance of telework, daily micro-events, and procrastination, this study offers managers distinct strategies for enhancing their employees' well-being. Despite the existing research investigating the effect of telework on well-being, studies investigating the intervening mechanisms between these two constructs are scarce. Moreover, there is a lack of research investigating the moderating effect of procrastination in these relations. Hence, this study fills these gaps and advances knowledge on the process that explains how (via daily micro-events) and when (when procrastination is low) teleworking influences workers’ well-being.info:eu-repo/semantics/publishedVersio

Optical doping and damage formation in AIN by Eu implantation

AlN films grown on sapphire were implanted with 300 keV Eu ions to fluences from 3×1014 to 1.4×1017 atoms/cm2 in two different geometries: “channeled” along the c-axis and “random” with a 10° angle between the ion beam and the surface normal. A detailed study of implantation damage accumulation is presented. Strong ion channeling effects are observed leading to significantly decreased damage levels for the channeled implantation within the entire fluence range. For random implantation, a buried amorphous layer is formed at the highest fluences. Red Eu-related photoluminescence at room temperature is observed in all samples with highest intensities for low damage samples (low fluence and channeled implantation) after annealing. Implantation damage, once formed, is shown to be stable up to very high temperatures.FCT - POCI/FIS/57550/2004FCT - PTDC/FIS/66262/2006FCT - PTDC/CTM/100756/200

Satisfação com as práticas de gestão de recursos humanos e intenção de turn over num hotel de cinco estrelas: o papel mediador da perceção de suporte organizacional

Employees’ satisfaction with human resources management (HRM) practices has been envisaged as a solid predictor of turnover; nonetheless, how these practices may influence employee’s behavior is still an unclear process. There are suggestions that HRM practices may be distal determinants of turnover, as their effects may be mediated by more proximal variables such as perceived organizational support. This study empirically tested a model of research arising from these theoretical suggestions in a five-star hotel. The data collected from the survey of 152 workers were subjected to structural equation analyses. The results showed that the theoretical model had a strong fit to the data, giving empirical support to the prediction that satisfaction with HRM practices reduces turnover intentions, by increasing perceived organizational support. The importance of these results is discussed and interpreted from the point of view of strategic gains associated to the quality of HRM practices for the management of voluntary turnover.info:eu-repo/semantics/publishedVersio

Pustulose Palmoplantar Recalcitrante: Já foi Considerada a Hipótese de Dermite de Contacto Alérgica?

Palmoplantar pustulosis (PPP) is a chronic and relapsing disease of the palms and soles, which tends to be difficult to treat. Classically it was described as a subtype of psoriasis. Nowadays it is regarded as a separate entity, although plaque-type psoriasis affects concomitantly many patients with PPP. A link between allergic contact dermatitis (ACD) and PPP has been described, and the former may encompass a potential to perpetuate the latter. Hereby we report two cases of difficult to treat plantar pustulosis. Underneath the dermatosis’s refractive nature was an allergic sensitization to potassium dichromate and cobalt chloride. Leather shoes and leather insoles were commonly worn, and both allergens are employed by the leather industry. Clinical remission was achieved in both cases with allergen eviction. Patch testing must be considered in cases of PPP without response to treatment. If relevant sensitization is found, allergen eviction measures are mandatory.A pustulose palmoplantar (PPP) é uma doença crónica e recorrente das palmas e plantas, que tende a ser díficil de tratar. Classicamente era descrita como um subtipo de psoríase. Actualmente é considerada uma entidade distinta, embora psoríase em placas afecte concomitantemente muitos doentes com PPP. Uma relação entre dermite de contacto alérgica (DCA) e PPP já foi descrita, e a primeira acarreta um potencial de perpeptuar a última. Aqui descrevemos dois casos de pustulose plantar de tratamento díficil. Subjacente à natureza refractária da dermatose, encontrava-se uma sensitização alergénica ao dicromato de potássio e ao cloreto de cobalto. Sapatos e palmilhas de cabedal eram comumente usadas pelas doentes, e ambos os alergénios referidos são utilizados na indústria do cabedal. Remissão clínica foi atingida em ambos os casos com evicção alergénica. O testes epicutâneos devem ser considerados em casos de PPP refractários ao tratamento. Se for demonstrada sensibilização relevante, medidas de evicção alergénica são obrigatórias

Control of quantum transverse correlations on a four-photon system

Control of spatial quantum correlations in bi-photons is one of the fundamental principles of Quantum Imaging. Up to now, experiments have been restricted to controlling the state of a single bi-photon, by using linear optical elements. In this work we demonstrate experimental control of quantum correlations in a four-photon state comprised of two pairs of photons. Our scheme is based on a high-efficiency parametric downconversion source coupled to a double slit by a variable linear optical setup, in order to obtain spatially encoded qubits. Both entangled and separable pairs have been obtained, by altering experimental parameters. We show how the correlations influence both the interference and diffraction on the double slit.Comment: 14 pages, 6 figure

Conformal Bulk Fields, Dark Energy and Brane Dynamics

In the Randall-Sundrum scenario we analyze the dynamics of a spherically symmetric 3-brane when the bulk is filled with matter fields. Considering a global conformal transformation whose factor is the $Z_2$ symmetric warp we find a new set of exact dynamical solutions for which gravity is bound to the brane. The set corresponds to a certain class of conformal bulk fields. We discuss the geometries which describe the dynamics on the brane of polytropic dark energy.Comment: 12 pages, latex, 2 figures. Talk given by Rui Neves at the Fourth International Conference on Physics Beyond the Standard Model, Beyond the Desert 03, Fundamental Experimental and Theoretical Developments in Particle Physics, Accelerator, Non-Accelerator and Space Approaches, Max Planck Institut f. Kernphysik/MPI Heidelberg, Castle Ringberg, Tegernsee, Germany, 9-14 June 2003. To be published in the Conference Proceedings, Springer-Verlag, Heidelberg, German