Evaluation of Cracks Caused by Mechanical Vibrations in Buildings

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Utilização da mínima quantidade de lubrificante (MQL) com água no processo de retificação cilíndrica em cerâmica avançada com rebolo de ligante resino cerâmico/metálico

Pós-graduação em Engenharia Mecânica - FEB

Morphofunctional characterization of decellularized vena cava as tissue engineering scaffolds

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Desenvolvimento de sistema eletrônico para instrumentar um DPL em ensaio dinâmico de resistência do solo

Pós-graduação em Engenharia Elétrica - FEIS

Elimination of All-Optical Cycles in Wavelength-Routed Optical Networks

A transparent (wide-area) wavelength-routed optical network may be constructed by using wavelength cross-connect switches connected together by fiber to form an arbitrary mesh structure. The network is accessed through electronic stations that are attached to some of these cross-connects. These wavelength cross-connect switches have the property that they may configure themselves into unspecified states. Each input port of a switch is always connected to some output port of the switch whether or not such a connection is required for the purpose of information transfer. Due to the presence of these unspecified states, there exists the possibility of setting up unintended alloptical cycles in the network (viz., a loop with no terminating electronics in it). If such a cycle contains amplifiers [e.g., Erbium- Doped Fiber Amplifiers (EDFA’s)], there exists the possibility that the net loop gain is greater than the net loop loss. The amplified spontaneous emission (ASE) noise from amplifiers can build up in such a feedback loop to saturate the amplifiers and result in oscillations of the ASE noise in the loop. Such all-optical cycles as defined above (and hereafter referred to as “white” cycles) must be eliminated from an optical network in order for the network to perform any useful operation. Furthermore, for the realistic case in which the wavelength cross-connects result in signal crosstalk, there is a possibility of having closed cycles with oscillating crosstalk signals. We examine algorithms that set up new transparent optical connections upon request while avoiding the creation of such cycles in the network. These algorithms attempt to find a route for a connection and then (in a post-processing fashion) configure switches such that white cycles that might get created would automatically get eliminated. In addition, our call-set-up algorithms can avoid the possibility of crosstalk cycles.

Global Competence: Determination of its Importance for Engineers Working in a Global Environment

We live and work in a world that is even more interconnected and interdependent than ever before. Engineers must now not only develop technical engineering competence, but must also develop additional skills and competencies including global competence to obtain success within a global engineering environment. The purpose of this study was to determine whether multinational companies considered global competence an important skill in mechanical engineering graduates when making hiring decisions. The study was an exploratory study that utilized an extensive literature review to identify eight global competencies for engineering success within a global environment and also included a survey instrument completed by Brigham Young University (BYU) mechanical engineering alumni in 48 states and 17 countries. The study focused on an evaluation of standard hiring technical engineering competencies with eight global competencies identified in the literature review. The study established that standard engineering technical competencies were the most important consideration when hiring mechanical engineers, but global competence was also considered important by a majority of all survey respondents with six of the eight global competencies rated important by 79 to 91% of respondents with an ability to communicate cross-culturally the highest-rated global competence. The importance of global competence in engineers when making hiring decisions, as considered by large companies who employed more than 10,000 employees or who had annual revenue exceeding $1 billion (US$) per year, was particularly strong. The majority of respondents (70%) indicated that companies were willing to provide training and experience to help engineers obtain success in a global engineering environment. In addition, a majority of respondents (59.9%) indicated that companies valued the efforts of higher educational engineering institutions to prepare engineers for success in a global environment with only 4.8% of respondents indicating that they did not value the efforts of higher education engineering institutions. However, only 27% of respondents agreed that colleges and universities were successful in this endeavor. Globalization is not a passing phenomenon, it is here to stay. Colleges and universities throughout the world need to recognize the importance of globalization and the interdependence and interconnectedness among the world’s population. Therefore, it is important to identify, develop, and provide opportunities for international collaboration and interaction among students and faculty throughout the world and to focus on developing global competence as an important outcome for engineering graduates.

Charge generation, charge transport, and residual charge in the electrospinning of polymers: A review of issues and complications

Electrospinning has become a widely implemented technique for the generation of nonwoven mats that are useful in tissue engineering and filter applications. The overriding factor that has contributed to the popularity of this method is the ease with which fibers with submicron diameters can be produced. Fibers on that size scale are comparable to protein filaments that are observed in the extracellular matrix. The apparatus and procedures for conducting electrospinning experiments are ostensibly simple. While it is rarely reported in the literature on this topic, any experience with this method of fiber spinning reveals substantial ambiguities in how the process can be controlled to generate reproducible results. The simplicity of the procedure belies the complexity of the physical processes that determine the electrospinning process dynamics. In this article, three process domains and the physical domain of charge interaction are identified as important in electrospinning: (a) creation of charge carriers, (b) charge transport, (c) residual charge. The initial event that enables electrospinning is the generation of region of excess charge in the fluid that is to be electrospun. The electrostatic forces that develop on this region of charged fluid in the presence of a high potential result in the ejection of a fluid jet that solidifies into the resulting fiber. The transport of charge from the charge solution to the grounded collection device produces some of the current which is observed. That transport can occur by the fluid jet and through the atmosphere surrounding the electrospinning apparatus. Charges that are created in the fluid that are not dissipated remain in the solidified fiber as residual charges. The physics of each of these domains in the electrospinning process is summarized in terms of the current understanding, and possible sources of ambiguity in the implementation of this technique are indicated. Directions for future research to further articulate the behavior of the electrospinning process are suggested. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3682464]

Describing fatigue crack growth and load ratio effects in Al 2524 T3 alloy with an enhanced exponential model

The fatigue crack behavior in metals and alloys under constant amplitude test conditions is usually described by relationships between the crack growth rate da/dN and the stress intensity factor range Delta K. In the present work, an enhanced two-parameter exponential equation of fatigue crack growth was introduced in order to describe sub-critical crack propagation behavior of Al 2524-T3 alloy, commonly used in aircraft engineering applications. It was demonstrated that besides adequately correlating the load ratio effects, the exponential model also accounts for the slight deviations from linearity shown by the experimental curves. A comparison with Elber, Kujawski and "Unified Approach" models allowed for verifying the better performance, when confronted to the other tested models, presented by the exponential model. (C) 2012 Elsevier Ltd. All rights reserved.

ESTIMATING REACTION CONSTANTS BY AB INITIO MOLECULAR MODELING: A STUDY ON THE OXIDATION OF PHENOL TO CATECHOL AND HYDROQUINONE IN ADVANCED OXIDATION PROCESSES

Molecular modeling is growing as a research tool in Chemical Engineering studies, as can be seen by a simple research on the latest publications in the field. Molecular investigations retrieve information on properties often accessible only by expensive and time-consuming experimental techniques, such as those involved in the study of radical-based chain reactions. In this work, different quantum chemical techniques were used to study phenol oxidation by hydroxyl radicals in Advanced Oxidation Processes used for wastewater treatment. The results obtained by applying a DFT-based model showed good agreement with experimental values available, as well as qualitative insights into the mechanism of the overall reaction chain. Solvation models were also tried, but were found to be limited for this reaction system within the considered theoretical level without further parameterization.

Estimating reaction constants by ab initio molecular modeling: a study on the oxidation of phenol to catechol and hydroquinone in advanced oxidation processes

Molecular modeling is growing as a research tool in Chemical Engineering studies, as can be seen by a simple research on the latest publications in the field. Molecular investigations retrieve information on properties often accessible only by expensive and time-consuming experimental techniques, such as those involved in the study of radical-based chain reactions. In this work, different quantum chemical techniques were used to study phenol oxidation by hydroxyl radicals in Advanced Oxidation Processes used for wastewater treatment. The results obtained by applying a DFT-based model showed good agreement with experimental values available, as well as qualitative insights into the mechanism of the overall reaction chain. Solvation models were also tried, but were found to be limited for this reaction system within the considered theoretical level without further parameterization.

Study of the Influence of Localized Vibrational Modes in Charge Transport Properties at Nanoscale Systems.

In molecular and atomic devices the interaction between electrons and ionic vibrations has an important role in electronic transport. The electron-phonon coupling can cause the loss of the electron's phase coherence, the opening of new conductance channels and the suppression of purely elastic ones. From the technological viewpoint phonons might restrict the efficiency of electronic devices by energy dissipation, causing heating, power loss and instability. The state of the art in electron transport calculations consists in combining ab initio calculations via Density Functional Theory (DFT) with Non-Equilibrium Green's Function formalism (NEGF). In order to include electron-phonon interactions, one needs in principle to include a self-energy scattering term in the open system Hamiltonian which takes into account the effect of the phonons over the electrons and vice versa. Nevertheless this term could be obtained approximately by perturbative methods. In the First Born Approximation one considers only the first order terms of the electronic Green's function expansion. In the Self-Consistent Born Approximation, the interaction self-energy is calculated with the perturbed electronic Green's function in a self-consistent way. In this work we describe how to incorporate the electron-phonon interaction to the SMEAGOL program (Spin and Molecular Electronics in Atomically Generated Orbital Landscapes), an ab initio code for electronic transport based on the combination of DFT + NEGF. This provides a tool for calculating the transport properties of materials' specific system, particularly in molecular electronics. Preliminary results will be presented, showing the effects produced by considering the electron-phonon interaction in nanoscale devices.

Essays on Wage and Price Formation in Sweden

Study IReal Wage Determination in the Swedish Engineering Industry This study uses the monopoly union model to examine the determination of real wages and in particular the effects of active labour market programmes (ALMPs) on real wages in the engineering industry. Quarterly data for the period 1970:1 to 1996:4 are used in a cointegration framework, utilising the Johansen's maximum likelihood procedure. On a basis of the Johansen (trace) test results, vector error correction (VEC) models are created in order to model the determination of real wages in the engineering industry. The estimation results support the presence of a long-run wage-raising effect to rises in the labour productivity, in the tax wedge, in the alternative real consumer wage and in real UI benefits. The estimation results also support the presence of a long-run wage-raising effect due to positive changes in the participation rates regarding ALMPs, relief jobs and labour market training. This could be interpreted as meaning that the possibility of being a participant in an ALMP increases the utility for workers of not being employed in the industry, which in turn could increase real wages in the industry in the long run. Finally, the estimation results show evidence of a long-run wage-reducing effect due to positive changes in the unemployment rate. Study IIIntersectoral Wage Linkages in Sweden The purpose of this study is to investigate whether the wage-setting in certain sectors of the Swedish economy affects the wage-setting in other sectors. The theoretical background is the Scandinavian model of inflation, which states that the wage-setting in the sectors exposed to international competition affects the wage-setting in the sheltered sectors of the economy. The Johansen maximum likelihood cointegration approach is applied to quarterly data on Swedish sector wages for the period 1980:1–2002:2. Different vector error correction (VEC) models are created, based on assumptions as to which sectors are exposed to international competition and which are not. The adaptability of wages between sectors is then tested by imposing restrictions on the estimated VEC models. Finally, Granger causality tests are performed in the different restricted/unrestricted VEC models to test for sector wage leadership. The empirical results indicate considerable adaptability in wages as between manufacturing, construction, the wholesale and retail trade, the central government sector and the municipalities and county councils sector. This is consistent with the assumptions of the Scandinavian model. Further, the empirical results indicate a low level of adaptability in wages as between the financial sector and manufacturing, and between the financial sector and the two public sectors. The Granger causality tests provide strong evidence for the presence of intersectoral wage causality, but no evidence of a wage-leading role in line with the assumptions of the Scandinavian model for any of the sectors. Study IIIWage and Price Determination in the Private Sector in Sweden The purpose of this study is to analyse wage and price determination in the private sector in Sweden during the period 1980–2003. The theoretical background is a variant of the “Imperfect competition model of inflation”, which assumes imperfect competition in the labour and product markets. According to the model wages and prices are determined as a result of a “battle of mark-ups” between trade unions and firms. The Johansen maximum likelihood cointegration approach is applied to quarterly Swedish data on consumer prices, import prices, private-sector nominal wages, private-sector labour productivity and the total unemployment rate for the period 1980:1–2003:3. The chosen cointegration rank of the estimated vector error correction (VEC) model is two. Thus, two cointegration relations are assumed: one for private-sector nominal wage determination and one for consumer price determination. The estimation results indicate that an increase of consumer prices by one per cent lifts private-sector nominal wages by 0.8 per cent. Furthermore, an increase of private-sector nominal wages by one per cent increases consumer prices by one per cent. An increase of one percentage point in the total unemployment rate reduces private-sector nominal wages by about 4.5 per cent. The long-run effects of private-sector labour productivity and import prices on consumer prices are about –1.2 and 0.3 per cent, respectively. The Rehnberg agreement during 1991–92 and the monetary policy shift in 1993 affected the determination of private-sector nominal wages, private-sector labour productivity, import prices and the total unemployment rate. The “offensive” devaluation of the Swedish krona by 16 per cent in 1982:4, and the start of a floating Swedish krona and the substantial depreciation of the krona at this time affected the determination of import prices.

Engineering knowledge-based variance-reduction simulation and G-dominance for structural frame robust optimization

[EN] This paper proposes the incorporation of engineering knowledge through both (a) advanced state-of-the-art preference handling decision-making tools integrated in multiobjective evolutionary algorithms and (b) engineering knowledge-based variance reduction simulation as enhancing tools for the robust optimum design of structural frames taking uncertainties into consideration in the design variables.The simultaneous minimization of the constrained weight (adding structuralweight and average distribution of constraint violations) on the one hand and the standard deviation of the distribution of constraint violation on the other are handled with multiobjective optimization-based evolutionary computation in two different multiobjective algorithms. The optimum design values of the deterministic structural problem in question are proposed as a reference point (the aspiration level) in reference-point-based evolutionary multiobjective algorithms (here g-dominance is used). Results including

Studio di biomateriali usati come scaffold per Tissue Engineering e loro caratterizzazione con tecniche spettroscopiche vibrazionali e di analisi termica

This research investigated someone of the main problems connected to the application of Tissue Engineering in the prosthetic field, in particular about the characterization of the scaffolding materials and biomimetic strategies adopted in order to promote the implant integration. The spectroscopic and thermal analysis techniques were usefully applied to characterize the chemico-physical properties of the materials such as – crystallinity; – relative composition in case of composite materials; – Structure and conformation of polymeric and peptidic chains; – mechanism and degradation rate; – Intramolecular and intermolecular interactions (hydrogen bonds, aliphatic interactions). This kind of information are of great importance in the comprehension of the interactions that scaffold undergoes when it is in contact with biological tissues; this information are fundamental to predict biodegradation mechanisms and to understand how chemico-physical properties change during the degradation process. In order to fully characterize biomaterials, this findings must be integrated by information relative to mechanical aspects and in vitro and in vivo behavior thanks to collaborations with biomedical engineers and biologists. This study was focussed on three different systems that correspond to three different strategies adopted in Tissue Engineering: biomimetic replica of fibrous 3-D structure of extracellular matrix (PCL-PLLA), incorporation of an apatitic phase similar to bone inorganic phase to promote biomineralization (PCL-HA), surface modification with synthetic oligopeptides that elicit the interaction with osteoblasts. The characterization of the PCL-PLLA composite underlined that the degradation started along PLLA fibres, which are more hydrophylic, and they serve as a guide for tissue regeneration. Moreover it was found that some cellular lines are more active in the colonization of the scaffold. In the PCL-HA composite, the weight ratio between the polymeric and the inorganic phase plays an essential role both in the degradation process and in the biomineralization of the material. The study of self-assembling peptides allowed to clarify the influence of primary structure on intermolecular and intermolecular interactions, that lead to the formation of the secondary structure and it was possible to find a new class of oligopeptides useful to functionalize materials surface. Among the analytical techniques used in this study, Raman vibrational spectroscopy played a major role, being non-destructive and non-invasive, two properties that make it suitable to degradation studies and to morphological characterization. Also micro-IR spectroscopy was useful in the comprehension of peptide structure on oxidized titanium: up to date this study was one of the first to employ this relatively new technique in the biomedical field.

Valutazione del comportamento differito di una trave inflessa realizzata in due fasi

La presente tesi analizza il comportamento differito in una prova di flessione su quattro punti su una trave prefabbricata con getto di soletta integrativa in opera. Sono riportati i risultati della prova di carico e di rottura sulla trave. Le prove sono state eseguite presso il Laboratorio di Prove Strutture (DISTART) dell'Università di Bologna. La trave è composta di due tipi di calcestreuzzo, realizzati in tempi diversi e con proprietà meccaniche diverse. L'obiettivo della campagna sperimentale è studiare l'effetto delle fasi di costruzione sull'evoluzione delle tensioni e delle deformazioni nel tempo e sulla resistenza ultima della trave. Il comportamento sperimentale è stato confrontato con i risultati numerici ottenuti con un modello a fibre in grado di cogliere anche i fenomeni legati al creep.