12 resultados para Elastic contact forces


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In this paper analytical transient solutions of dynamic response of one-dimensional systems with sudden change of foundation stiffness are derived. In more details, cantilever dynamic response, expressed in terms of vertical displacement, is extended to account for elastic foundation and then two cantilever solutions, corresponding to beams clamped on left and right hand side, with different value of Winkler constant are connected together by continuity conditions. The internal forces, as the unknowns, can be introduced by the same values in both clamped beam solutions and solved. Assumption about time variation of internal forces at the section of discontinuity must be adopted and originally analytical solution will have to include numerical procedure.

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Starting from theoretical perspectives on globalisation, the following article analyses how current working conditions are affected by globalisation processes. For this purpose, recent developments in the German clothing sector are traced back to the power of economic globalisation processes. Characterising the German clothing sector as pioneer in economic globalisation, we use empirical findings to illustrate how current processes of globalisation influence the work place: At organisational level, corporate strategies aim at rationalisation, standardisation and flexibilisation of work in order to response to the economic pressure of global markets. At individual level these strategies, in turn, speed up working processes and intensify working processes for the employees. Although these developments form strong trends, we conclude that the local embeddedness of companies is still of high importance with regard to organisational and individual consequences of globalisation.

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Transversal vibrations induced by a load moving uniformly along an infinite beam resting on a piece-wise homogeneous visco-elastic foundation are studied. Special attention is paid to the additional vibrations, conventionally referred to as transition radiations, which arise as the point load traverses the place of foundation discontinuity. The governing equations of the problem are solved by the normalmode analysis. The solution is expressed in a form of infinite sum of orthogonal natural modes multiplied by the generalized coordinate of displacement. The natural frequencies are obtained numerically exploiting the concept of the global dynamic stiffness matrix. This ensures that the frequencies obtained are exact. The methodology has restrictions neither on velocity nor on damping. The approach looks simple, though, the numerical expression of the results is not straightforward. A general procedure for numerical implementation is presented and verified. To illustrate the utility of the methodology parametric optimization is presented and influence of the load mass is studied. The results obtained have direct application in analysis of railway track vibrations induced by high-speed trains when passing regions with significantly different foundation stiffness.

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Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica

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A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics

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One of the largest health problems faced worldwide, when evaluated by direct (clinical) as well indirect cost (absenteeism), is the degeneration of the intervertebral disc (IVD) that leads to back pain and, potentially disability and individual´s quality of life decreasing. The intervertebral disc is a mechanical and biological complex structure, formed by a tough outer layer of fibrocartilage called Annulus Fibrosus (AF),which surrounds a soft, elastic and gelatinous core called Nucleus Pulposus (NP). These two structures are completed by two upper and lower encasing layer called Vertebral Endplates (VEP). The degeneration of the IVD is marked by the dehydration of the Nucleus Pulposus, reducing the hydrostatic pressure inside the nucleus, resulting in a loss of capability to support compressive forces, during the active period, and to regain height during the resting period. This situation will compromise the role of shock absorber by the NP and transfers these forces to the AF. This transfer will result in cracks on the AF, deteriorating the IVD, allowing the ingrowth of vessels and nerves. This project was based on the developing a protocol to test suitable NP replacements, in hope to future assessment of discrete mechanical values and characteristics for an NP replacement. For this, Nucleus pulposus samples from goat, encapsulated Hydromed gel denominated “Raviolis” and Chitosan gels, produced via wet route using an ammonium environment, were confined compressed. Chitosan was rheologically tested and swelling capability of all the three type of materials was assessed. Results showed that the Nucleus Pulposus and “Raviolis” have similar mechanical behavior, being able to swell and “build up” hydrostatic pressure after a compression stage, while the Chitosan gel did not showed that ability. Therefore, “Raviolis” are a more suitable candidate to replace the NP than Chitosan gels. It was also observed that confined compression is the key test to perform on any possible candidate to replace the NP.

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Currently, Portugal assumes itself as a democratic rule of substantive law State, sustained by a legal system seeking the right balance between the guarantee of fundamental rights and freedoms constitutional foreseen in Portugal’s Fundamental Law and criminal persecution. The architecture of the penal code lies with, roughly speaking, a accusatory basic structure, “deliberately attached to one of the most remarkable achievements of the civilizational democratic progress, and by obedience to the constitutional commandment”, in balance with the official investigation principle, valid both for the purpose of prosecution and trial. Regarding the principle of non self-incrimination - nemo tenetur se ipsum accusare, briefly defined as the defendant’s right of not being obliged to contribute to the self-incrimination, it should be stressed that there isn’t an explicit consecration in the Portuguese Constitution, being commonly accepted in an implicit constitutional prediction and deriving from other constitutional rights and principles, first and foremost, the meaning and scope of the concept of democratic rule of Law State, embedded in the Fundamental Law, and in the guidelines of the constitutional principles of human person dignity, freedom of action and the presumption of innocence. In any case, about the (in) applicability of the principle of the prohibition of self-incrimination to the Criminal Police Bodies in the trial hearing in Court, and sharing an idea of Guedes Valente, the truth is that the exercise of criminal action must tread a transparent path and non-compliant with methods to obtain evidence that violate the law, the public order or in violation of democratic principles and loyalty (Guedes Valente, 2013, p. 484). Within the framework of the penal process relating to the trial, which is assumed as the true phase of the process, the witness represents a relevant figure for the administration of criminal justice, for the testimonial proof is, in the idea of Othmar Jauernig, the worst proof of evidence, but also being the most frequent (Jauernig, 1998, p. 289). As coadjutant of the Public Prosecutor and, in specific cases, the investigating judge, the Criminal Police Bodies are invested with high responsibility, being "the arms and eyes of Judicial Authorities in pursuing the criminal investigation..." which has as ultimate goal the fulfillment of the Law pursuing the defense of society" (Guedes Valente, 2013, p. 485). It is in this context and as a witness that, throughout operational career, the Criminal Police Bodies are required to be at the trial hearing and clarify the Court with its view about the facts relating to occurrences of criminal context, thus contributing very significantly and, in some cases, decisively for the proper administration of the portuguese criminal justice. With regards to the intervention of Criminal Police Bodies in the trial hearing in Court, it’s important that they pay attention to a set of standards concerning the preparation of the testimony, the very provision of the testimony and, also, to its conclusion. Be emphasized that these guidelines may become crucial for the quality of the police testimony at the trial hearing, thus leading to an improvement of the enforcement of justice system. In this vein, while preparing the testimony, the Criminal Police Bodies must present itself in court with proper clothing, to read before and carefully the case files, to debate the facts being judged with other Criminal Police Bodies and prepare potential questions. Later, while giving his testimony during the trial, the Criminal Police Bodies must, summing up, to take the oath in a convincing manner, to feel comfortable, to start well by convincingly answering the first question, keep an attitude of serenity, to adopt an attitude of collaboration, to avoid the reading of documents, to demonstrate deference and seriousness before the judicial operators, to use simple and objective language, to adopt a fluent speech, to use nonverbal language correctly, to avoid spontaneity responding only to what is asked, to report only the truth, to avoid hesitations and contradictions, to be impartial and to maintain eye contact with the judge. Finally, at the conclusion of the testimony, the Criminal Police Bodies should rise in a smooth manner, avoiding to show relief, resentment or satisfaction, leaving a credible and professional image and, without much formality, requesting the judge permission to leave the courtroom. As final note, it’s important to stress that "The intervention of the Police Criminal Bodies in the trial hearing in Court” encloses itself on a theme of crucial importance not only for members of the Police and Security Forces, who must welcome this subject with the utmost seriousness and professionalism, but also for the proper administration of the criminal justice system in Portugal.

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Field lab: Consulting lab

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Analytical, numerical and experimental models have been developed over time to try to characterize and understand the metal cutting process by chip removal. A true knowledge of the cutting process by chip removal is required by the increasing production, by the quality requirements of the product and by the reduced production time, in the industries in which it is employed. In this thesis an experimental setup is developed to evaluate the forces and the temperature distribution in the tool according to the orthogonal cutting model conditions, in order to evaluate its performance and its possible adoption in future works. The experimental setup is developed in a CNC lathe and uses an orthogonal cutting configuration, in which thin discs fixed onto a mandrel are cut by the cutting insert. In this experimental setup, the forces are measured by a piezoelectric dynamometer while temperatures are measured by thermocouples placed juxtaposed to the side face of the cutting insert. Three different solutions are implemented and evaluated for the thermocouples attachment in the cutting insert: thermocouples embedded in thermal paste, thermocouples embedded in copper plate and thermocouples brazed in the cutting insert. From the tests performed in the experimental setup it is concluded that the adopted forces measurement technique shows a good performance. Regarding to the adopted temperatures measurement techniques, only the thermocouples brazed in the cutting insert solution shows a good performance for temperature measurement. The remaining solutions show contact problems between the thermocouple and the side face of the cutting insert, especially when the vibration phenomenon intensifies during the cut. It is concluded that the experimental setup does not present a sufficiently robust and reliable performance, and that it can only be used in future work after making improvements in the assembly of the thermocouples.

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This research intends to examine if there were significant differences on the brand engagement and on the electronic word of mouth (e-WOM)1 referral intention through Facebook between Generation X and Generation Y (also called millennials). Also, this study intends to examine if there are differences in the motivations that drive these generations to interact with brands through Facebook. Results indicated that Generation Y members consumed more content on Facebook brands’ pages than Generation X. Also, they were more likely to have an e-WOM referral intention as well as being more driven by brand affiliation and opportunity seeking. Finally, currently employed individuals were found to contribute with more content than students. This study fills the gap in the literature by addressing how marketing professionals should market their brand and interact and engage with their customers, based on customers’ generational cohort.

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This project aims to provide feasible solutions to improve customer´s Help Area at Continente Online. The goal is to increase satisfaction and loyalty by reducing the main causes that lead customers to appeal to Call Center or abandon the website. The pursued solution is the implementation of Web Self-Service and the vision taken is focused not only on providing customers basic help tools but also innovate with international best practices to sustain Sonae MC´s present and future market leader position. Customer´s feedback, costs and impact are taken in consideration to find the best fit for the company.

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This study aimed to understand employees’ reactions to organizational politics in Contact Centers. Drawing from a sample of 187 supervisor-employee dyads, we studied the relationship between employees’ perceptions of organizational politics and supervisor-rated task performance and deviance, and mediation effects by authenticity at work and affective commitment. Results indicate that workers tend to react to workplace politics with deviant behavior and worse task performance. We found that the relationship between perceived politics and task performance was mediated by authenticity. The relationship between perceived politics and supervisor-rated deviance was mediated by affective commitment to the organization. Implications for management are discussed.