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With the increase of technology in the electronics industry, new methods have emerged, resulting in smaller components and higher processing capacity. In contrast, problems related to rate of heat transfer of these components have been increasing and with this reduction in size, the temperature began to be an important variable to be observed in equipment. Normally, performance improvements, such as computers or racks of telephone exchanges, translate directly into greater heat dissipation of electronic devices that make up the device, and consequently, high rates of heat transfer. Thus, the cooling of electronic equipment gained paramount importance as the effect of increased power densities in micro-electronic equipment made available by advances in semiconductor technology. Because of this, whenever we face interesting challenges in finding a technique of removing heat more effectively for these high-tech applications, is one of those challenges, which underpin this research is to determine the properties of the constituent components of a new system cooling is a heat exchanger based on phase change of a fluid inert. There are a few examples: automotive radiator and air conditioning, cooling and optoelectronic LEDs. A heat exchanger is physically designed to enhance and to improve the surface in contact with the cooling fluid around it, like air. Approach air velocity, choice of material and surface treatment are some of the factors that influence the thermal resistance and thermal performance of these components. In this research, the epoxy resin with metallic charge, has lower thermal conductivity than aluminum, for example, however, it does not conduct electricity, getting great importance of electronic devices nowadays.

Made available in DSpace on 2021-06-25T11:11:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-03-01 Mechanisms usually transmit power by welded links into a shaft. Should this weld be partial, like fillet welds, there will be an area of stress concentration that could behave like a crack due to sharp corners. These can lead to structural failures due to fatigue. Consequently, to properly design, inspect and maintain these mechanisms it is necessary to use fracture mechanics stress intensity factors. The crack mesh simplicity required by the boundary element method allows easy modeling even for complex geometry. This technique will be used to obtain such parameters for a double fillet weld found in a diverter damper mechanism responsible for controlling hot gas flow to heat recovery steam generator in power plants. But the solutions presented can be used for similar geometrical configurations, specially to shaft link mechanisms. Empirical equations were also obtained to further ease fracture mechanics and fatigue analysis for this kind of geometry. Department of Maintenance Petrobras S.A Department of Mechanical Engineering Universidade Estadual Paulista (UNESP), Brasil Avenue, 56 Department of Mechanical Engineering Universidade Estadual Paulista (UNESP), Brasil Avenue, 56

In the use of acoustic correlation methods for water leak detection, sensors are placed at pipe access points either side of a suspected leak, and the peak in the cross-correlation function of the measured signals gives the time difference (delay) between the arrival times of the leak noise at the sensors. Combining this information with the speed at which the leak noise propagates along the pipe, gives an estimate for the location of the leak with respect to one of the measurement positions. It is possible for the structural dynamics of the pipe system to corrupt the time delay estimate, which results in the leak being incorrectly located. In this paper, data from test-rigs in the United Kingdom and Canada are used to demonstrate this phenomenon, and analytical models of resonators are coupled with a pipe model to replicate the experimental results. The model is then used to investigate which of the two commonly used correlation algorithms, the Basic Cross-Correlation (BCC) function or the Phase Transform (PHAT), is more robust to the undesirable structural dynamics of the pipe system. It is found that time delay estimation is highly sensitive to the frequency bandwidth over which the analysis is conducted. Moreover, it is found that the PHAT is particularly sensitive to the presence of resonances and can give an incorrect time delay estimate, whereas the BCC function is found to be much more robust, giving a consistently accurate time delay estimate for a range of dynamic conditions.

Magneto-rheological elastomers (MRE) are materials that change their stiffness and damping properties when subject to a magnetic field. They have evolved from magneto-rheological fluids which have some disadvantages, in that the particles in the fluid tend to collect as sediment. This means that the fluids require agitation to prevent this. MREs are a new material, so not much work has been carried out on their use to control vibration in mechanical structures. This paper investigates the effectiveness of MREs to control wave motion in a one-dimensional structure. A model of an MRE, coupled to a beam, is developed so that simulations can be conducted to demonstrate the effectiveness of MRE as a wave control measure. It is shown that the MRE can be used to control the amplitudes of the reflected and transmitted waves from the section of beam containing the MRE.

Leaks have been detected and localized in water distribution in many countries for years, by using the cross-correlation of pipe vibration measured either side of a suspected leak and/or by using listening sticks. However, in modern plastic pipes this is problematic because of the strong coupling between the water and the pipe which results in significant attenuation of the coupled fluid-pipe wave, which in turn is responsible for the propagation of leak noise. Hence leak noise does not propagate as far as it did in older metallic pipes. This paper discusses how the vibro-acoustic behavior of the water-pipe-soil system influences leak noise propagation. To investigate this, a numerical model is developed, and the results are compared with those from an analytical model for two water pipe systems, one in the UK and one in Brazil. Experimental results are also presented. It is shown that the important difference between the two systems is the shear stiffness of the surrounding soil, which has a profound effect on both the speed of leak noise propagation and the attenuation of the noise along the pipe.

Water loss through leakage in water pipeline distribution systems is a serious issue due to the increasing scarcity of water, such as the recent problem faced by Sao Paulo State in Brazil. Although older metallic pipes are now being replaced by plastic pipes they still suffer from leakage. Unfortunately, correlation techniques, which are used to locate leaks by correlating signals from two vibration sensors attached to the pipe, are less effective in plastic pipes because of higher leak noise attenuation. Hence, the gain setting of the sensors used to collect leak signals have to be carefully selected to enhance the effectiveness of correlation techniques when applied to plastic pipes. However, this is not simple in practical situations, so that the acquired data can become saturated (clipped) or be very small. This paper describes the effects of clipping on the estimation of time delay by severely distorting the signals by using the signum function. It transpires, that although this adds some noise to the original signals, and potentially reduces the bandwidth of which there are measurable leak noise signals, it does not have a profound effect on time delay estimation and hence the accuracy of the leak location. Leak noise signals measured in controlled conditions on a bespoke test-rig constructed by South Staffs Water plc, are used to demonstrate how this process works.

Made available in DSpace on 2019-10-06T16:25:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-05-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Leak noise correlators are commonly used to detect and locate leaks in buried water pipes. They use the cross-correlation function between leak noise signals measured using hydrophones or accelerometers placed on the pipe either side of the leak. The efficacy of a correlator is dependent upon knowledge of the speed at which the leak noise propagates along the pipe as well as how much it attenuates with distance. The leak noise is carried in a predominantly fluid-borne wave in the pipe, which is heavily influenced by the pipe and soil properties. Although the pipe properties can be determined relatively easily, estimation of the soil properties surrounding the pipe is more problematic. It is desirable to have an accurate estimate of the soil properties, so that current models can be developed and used to improve understanding of leak noise propagation and hence leak detection capabilities. In this paper a novel approach to determining the bulk and shear moduli of the soil from measurements of the predominantly fluid-borne wave in a buried plastic pipe, is described. The measured data are compared with corresponding data predicted from a model, and the soil properties are determined using an optimization algorithm. The method is applied to two different sites, one in the UK, where the soil properties surrounding the pipe are representative of sandy soil, and one in Brazil, where the surrounding soil has properties that are representative of clay soil. It is found that the bulk and shear modulus can be estimated in the pipe buried in sandy soil, but in the clay soil it is only possible to estimate the shear modulus. Department of Mathematics UTFPR - Federal University of Technology of Paraná, Cornélio Procópio Department of Mechanical Engineering UNESP - São Paulo State University, Ilha Solteira Institute of Sound and Vibration Research University of Southampton Highfield Department of Biosystems Engineering UNESP - São Paulo State University, Tupã Department of Mechanical Engineering UNESP - São Paulo State University, Ilha Solteira Department of Biosystems Engineering UNESP - São Paulo State University, Tupã FAPESP: 2013/50412-3 FAPESP: 2017/14432-0

Made available in DSpace on 2018-12-11T17:28:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-12-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Several composites and nanocomposites based on a polymeric matrix and ceramic fillers are being pursued for use as multifunctional and innovative materials. Nevertheless, there is a series of challenges to be solved in this area such as the understanding of the role of interfaces and the synergy between matrix and fillers. In this work, vulcanized natural rubber nanocomposites were prepared with different concentrations of two kinds of ceramic nanoparticles, potassium strontium niobate (KSr2Nb5O15 or KSN) and nickel–zinc ferrite (Ni0.5Zn0.5Fe2O4 or NZF), synthesized by a chemical method known as the modified polyol method. Morphological and thermal characterizations were carried out by AFM, TG/DTG, TG/FTIR and DSC. The thermal properties of nanocomposites were compared and discussed as functions of concentration, type and surface of nanoparticles. The results obtained suggest that the base concentration for both types of nanoparticles inside the polymer matrix volume greatly adds to the increase in thermal stability up to 11 % and the glass transition temperature up to 10 °C. A similar evolution for the glass transition temperature (Tg), thermal stability temperature (TS) and dielectric permittivity (ε′) was identified, suggesting that these phenomena are mainly dominated by the same mechanisms. These results point to the possibility for the thermal parameter modulation in magnetic and ferroelectric nanocomposites by means of a suitable control of concentration and properties of the KSN and NZF nanoparticles. FEIS—Faculdade de Engenharia de Ilha Solteira UNESP—Univ Estadual Paulista Ministério da Ciência Tecnologia e Inovação—MCTI Department of Biosystem Engineering UNESP—Univ Estadual Paulista FCT—Faculdade de Ciências e Tecnologia UNESP—Univ Estadual Paulista FEIS—Faculdade de Engenharia de Ilha Solteira UNESP—Univ Estadual Paulista Department of Biosystem Engineering UNESP—Univ Estadual Paulista FCT—Faculdade de Ciências e Tecnologia UNESP—Univ Estadual Paulista FAPESP: 2009/00523-8 CNPq: 454843/2014-3 CNPq: 455323/2014-3 CNPq: 480377/2013-8

Water companies are under constant pressure to ensure that water leakage is kept to a minimum. Leak noise correlators are often used to help find and locate leaks. These devices correlate acoustic or vibration signals from sensors which are placed either side the location of a suspected leak. The peak in the cross-correlation function of the measured signals gives the time difference between the arrival times of the leak noise at the sensors. To convert the time delay into a distance, the speed at which the leak noise propagates along the pipe (wave-speed) needs to be known. Often, this is estimated from historical wave-speed data measured on other pipes obtained at various times and under various conditions, or it is estimated from tables which are calculated using simple formula. Usually, the wave-speed is not measured directly at the time of the correlation measurement and is therefore potentially a source of significant error in the localisation of the leak. In this paper, a new method of measuring the wave-speed in-situ in the presence of a leak, that is robust and simple, is explored. Experiments were conducted on a bespoke large scale buried pipe test-rig, in which a leak was also induced in the pipe between the measurement positions to simulate a condition that is likely to occur in practice. It is shown that even in conditions where the signal to noise ratio is very poor, the wave-speed estimate calculated using the new method is less than 5% different from the best estimate of 387 m s −1 .

Detection and location of leaks in buried plastic fluid-filled pipes are topics of increasing concern for water distribution companies. Acoustic correlation techniques have been widely used to provide an accurate estimate of the position of a leak in order to reduce the wastage of water. However, this technique depends on an accurate estimate of the wave propagation speed along the pipe, which is heavily dependent on the type of soil in which the pipe is buried. The soil also affects the distance that leak noise will propagate along the pipe. This paper describes theoretical and experimental investigations into the way the coupling conditions between the pipe and the soil affects the propagation characteristics of the wave that propagates leak noise in the pipe. Two water pipe systems which have different soil properties are considered: one is in Brazil and the other one is in UK. For the Brazilian pipe system, it is found that the shear modulus rather than the bulk modulus of the soil, has a profound effect on the wave motion in the pipe since it is buried in a clay-like soil. In this case, only the shear wave in the soil propagates away from the pipe. For the UK pipe system, which has sandy soil, both compressional and shear waves propagate away from the pipe. An analysis of the physical effects of fluid-pipe-soil interface and their corresponding parameters on the pipe wave speed and attenuation is also carried out. The results show that the axial coupling between the pipe and the soil has an important effect in the UK pipe system, but has a negligible effect in the Brazilian pipe system.

© 2018 Elsevier Ltd In many countries, leaks are located in water distribution pipes by using the cross-correlation of pipe vibration measured either side of a suspected leak. However, in modern plastic pipes this can be problematic due to strong coupling between the water, the pipe and the soil, affecting the propagation of leak noise within the pipe. This paper concerns an analytical, numerical and experimental investigation into the way in which soil properties influence leak noise propagation in buried plastic water pipes. The analytical model allows a detailed investigation into the physical effects of the soil on leak noise (wave) propagation in the pipe, in particular on the wave-speed and wave attenuation. Results highlight that, in addition to the pipe hoop stiffness, the shear stiffness of the soil can have a significant effect on the wave-speed in the pipe. Experimental measurements were conducted at two different sites - one in the UK and the other in Brazil. In the UK system, both dilatational and shear waves in the soil propagate away from the pipe, resulting in large wave attenuation in the pipe. However, in the Brazilian system, only shear waves propagate resulting in smaller wave attenuation in the pipe.

To accurately determine the position of a leak in a buried plastic water pipe using acoustic correlation, a good estimate of the speed of noise propagation (wave speed) is required. The factors that affect this wave speed, and attenuation of the wave as it propagates along the pipe, include the pipe flexibility and the soil properties. These effects are discussed in this paper, and are illustrated by way of simulations for two different pipe sizes and two different soil types. It is shown that the soil type in Brazil can have a profound effect on the wave speed and hence the accuracy of leak location. Some practical problems in estimating the wave speed from in-situ measurements are also outlined. Although this is relatively simple to measure in principle, in practice it is extremely difficult to do, for a variety of reasons. Some of these are discussed and the reason why this measurement is particularly problematic with plastic water distribution pipes is illustrated.

In this research, a vapor chamber embedded in the base of a heat sink was experimentally analyzed for the application in thermal management of microelectronics. The vapor chamber was produced by a copper and molybdenum alloy with length of 240 mm, width of 54 mm, thickness of 3 mm, and capillary structures composed by copper screen meshes. The working fluid used was de-ionized water. The pure aluminum heat sink was cooled by air forced convection and the evaporator vapor chamber was heated using an electrical resistor simulating integrated circuit power dissipation. The experimental tests were done in a suction type wind tunnel with open return for a heat load varying from 20 to 80 W and for an airflow velocity varying from 1 to 4 m/s. The experimental results showed that the considered vapor chamber worked successfully, maintaining low operating temperature.

In recent decades, an increasing effort has been made not only to foster cost-effective, competitive and innovative industries but also to create smart materials. In this work, we present the morphological, magnetic and mechanical characterizations, as well as the effect of a magnetic field on the mechanical properties of magnetic nanocomposites type magnetorheological elastomers (MRE), based on carbonyl iron particles, embedded in a silicone elastomer (SR/IRON). These MREs were prepared by the curing process at room temperature of the silicone rubber and different concentrations of iron particles, 18%, 33% and 48% in volume. From mechanical tests assisted by a magnetic field: (i) a strong dependence on the mechanical response with the application of a magnetic field on the samples and (ii) a variation between 34% and 61% on the mechanical properties of the MRE related to the particle concentration in the samples. These results point to the possibility of using these nanocomposites based on silicon rubber and iron as smart materials type MRE and in vibration absorption systems, once they exhibit acceptable values of mechanical dependence with the applied external magnetic field.

Improvements on prognostics and health management (PHM) techniques are extremely important in order to prevent system failure and reduce costs with maintenance and machine downtime. In the particular case of system components subjected to fracture failure, such improvements are closely related to the effect of crack propagation mechanisms on the quantification of the system remaining useful life (RUL). This chapter presents a review of the state-of-the-art of crack propagation modeling techniques and discusses the current limitations of finite elements methods (FEM) to model structures with cracks. The chapter also gives special attention to peridynamics (PD), a continuum non-local approach that has been considered to be a promising method to model structures with crack discontinuities. Therefore, the purpose of this chapter is to answer the following research question: “Can PD be a potential alternative to FEM on modeling of crack propagation problems in predicting RUL?” In order to answer this question, a literature review of the most relevant works on crack modeling field is presented and discussed. An application that involves a classical 2D crack propagation problem in a pre-notched glass plate is also included, in which comparisons between numerical predictions and experimental observations were performed. It was shown that PD produces more accurate predictions than FEM based-methods from both qualitative and quantitative perspectives.

Gears are the components in many mechanical systems that are likely to develop faults due to their dynamic characteristics, such as the cyclic loading applied to the meshing teeth. The main faults in gears are pitting and scuffing, where the tooth profile (involute) is heavily affected, and hence, signal processing techniques have been developed to aid in the detection of gear faults in their early stages. It is already known that the dynamic behaviour of a mechanical system changes when its characteristics are affected (such as in the presence of a fault), and as a result, the vibration of such a system can be used to detect a fault in its early stage. To investigate and develop techniques based on vibration analysis, a physical understanding of the system involving meshing gears is required. In this chapter, a model is introduced that can be used for simulating vibration data of toothed meshing gears. The data generated by the simulations is then used to investigate some classic techniques used in gear fault detection problems.

A common way to detect and locate leaks in buried water pipes is to use leak noise correlators. Vibration or acoustic signals are measured on or in the pipe using sensors placed either side of the leak, and the difference in the leak noise arrival times (time delay) at the sensors is estimated from the peak in the cross-correlation function of these signals. Over many years, much effort has been spent on improving the quality of the leak noise signals with the aim of improving the time delay estimate. In this paper it is shown that even if the signals suffer from severe amplitude distortion through either clipping or quantization, then an accurate time delay estimate can be obtained provided that the zero crossings in the noise data are preserved. This is demonstrated by using polarity co-incidence correlation on simulated and measured data. The use of random telegraph theory is also used as an approximation to allow the derivation of approximate analytical solutions for the cross-correlation function and cross spectral density of clipped noise to facilitate further insight into the effects of severe clipping.

Made available in DSpace on 2018-12-11T17:25:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-02-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Nickel-zinc ferrites as well as their nanocomposites formed by natural rubber are desirable because they take advantage of the thermal, mechanical and magnetic properties of each component. However, to date, the effect of the size, shape and concentration of the magnetic fillers on the magnetic properties of nanocomposite has not been studied in detail. In this report, we are presenting results about the influence of the geometric characteristic of fillers on the magnetic parameters of nanocomposites. Nickel-zinc ferrite nanopowders (NZF) with stoichiometry Ni0.5Zn0.5Fe2O4 were synthesized by a chemical route named the Modified Polyol Method (MPM) and magnetic nanocomposites were prepared with concentrations between 1 and 10 phr of ferrite nanopowders by thermal compression and hot pressing. From TEM images of ferrite nanopowders aggregates and primary particles in the nanometric scale were identified with aspect ratio different from 1 (r = a/b = 0.99, 0.55 and 0.43). From VSM measurements and particle size, the NZF may be classified as a ferrimagnetic material in a paramagnetic state and the saturation magnetization (MS) was equal to 36.4 emu/g. Performing VSM experiments with different degrees between the sample and the magnetic field, differences up to 9% were identified for the MS indicating a dependence of magnetic parameters on the concentration and shape of particles and aggregates. Magnetization versus time assays were carried out via VSM and two distinct relaxation times were achieved and associated with different populations of size and/or shape for the magnetic fillers. These results point to the possibility of modulation of the magnetic properties of vulcanized natural rubber composites by means of a suitable engineering process to control the concentration, size and shape of magnetic nanoparticles and agglomerates. FEIS - Faculdade de Engenharia de Ilha Solteira, UNESP - Univ Estadual Paulista Ministério da Ciência, Tecnologia e Inovação - MCTI Department of Biosystem Engineering, UNESP - Univ Estadual Paulista FCT - Faculdade de Ciências e Tecnologia, UNESP - Univ Estadual Paulista CellMat Laboratory, Condensed Matter Physics Department, University of Valladolid FEIS - Faculdade de Engenharia de Ilha Solteira, UNESP - Univ Estadual Paulista Department of Biosystem Engineering, UNESP - Univ Estadual Paulista FCT - Faculdade de Ciências e Tecnologia, UNESP - Univ Estadual Paulista CNPq: 11208/13-9 FAPESP: 2009/00523-8 CNPq: 449999/2014-9 CNPq: 454843/2014-3 CNPq: 455323/2014-3 CNPq: 480377/2013-8 CNPq: BEX 5129/09-5

Made available in DSpace on 2018-12-11T16:58:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-01-15 Acoustic correlators have been used for many years to locate and detect leaks in buried water distribution pipes. Currently, the only way to compare different correlators directly is in the field. This can be problematic as it may be difficult to present exactly the same conditions to each correlator. In recent years, the way in which leak noise propagates in buried water pipes has been determined, and this has enabled the development of a virtual pipe whose behaviour can be simulated in the computer. By coupling the filtering properties of the pipe with electrodynamic shakers, a proof-of-concept virtual pipe test-rig has been developed that will allow different correlators to be compared directly in laboratory conditions. Different situations, such as pipe material and size, and measurement positions, as well as leak strength can be simulated. The theoretical basis of the test-rig and details of the proof-of-concept system are discussed in this paper. It is shown that careful consideration of the dynamics of the shakers is vital if the system is to faithfully model situations that are found in the field. Department of Mechanical Engineering, UNESP, Ilha Solteira Department of Biosystem Engineering, UNESP, Tupã Institute of Sound and Vibration Research, University of Southampton Department of Mechanical Engineering, UNESP, Ilha Solteira Department of Biosystem Engineering, UNESP, Tupã

Novel materials suitable for engineering applications are under development in a number of research centers. Among them, fluids and gels that can change their rheological properties start to grow in importance for smart structures applications. Such materials usually present changes in their properties due to action of an external field, such as electric or magnetic. It has been observed that changes may occur very fast, allowing applications in active control, for instance. There are two main classes of the so-called smart fluids, one exploiting the electro-rheological (ER) effect, and the other exploiting the magneto-rheological (MR) effect. These variable rheology fluids can have their mechanical properties modeled in terms of different behaviors of the field-dependent stress–strain curve. For the pre-yield region of the stress–strain curve the fluid behaves like a viscoelastic material, then as plastic in the post-yield region, and as viscoelastic-plastic in the transition through yield region. Considering that smart fluids exhibit linear shear behavior at small strain levels, similar to many viscoelastic materials, it is convenient to model variable rheology fluids with the same approaches developed for viscoelastically damped structures. As a study case, a sandwich beam with ER fluid core is modeled with finite element method. The dynamical behavior is assessed with the Golla-Hughes-McTavish (GHM) method to incorporate the frequency dependence properties of the ER fluid in a structural time domain model, admitting its behavior as viscoelastic and dependent on an electric field. The results are compared with analytical models and experimental data available in literature, aiming to illustrate the potential of variable rheology fluids in further smart structures concepts.

In this research, the thermal behavior of a vapor chamber embedded in the base of a heat sink was experimentally analyzed considering the influence of the heat source position. The vapor chamber was produced by a copper and molybdenum alloy with length of 240 mm, width of 54 mm, thickness of 3 mm, and capillary structures composed by copper screen meshes. The working fluid used was de-ionized water. The pure aluminum heat sink was cooled by air forced convection and the evaporator vapor chamber was heated using an electrical resistor simulating integrated circuit power dissipation. The experimental tests were done in a suction type wind tunnel with open return for a heat load varying from 20 to 80 W, for an airflow velocity varying from 1 to 4 m/s, and for three different heat source positions. The experimental results showed that, independently of the heat source position, the considered vapor chamber worked successfully, maintaining low operating temperature.

Com o grande desenvolvimento da tecnologia, houve um aumento no empacotamento eletronico, com o consequente aumento da dissipacao de potencia termica. O desconhecimento da potencia se tornou um entrave, fazendo com que os fabricantes superdimensionem o sistema de resfriamento de seus produtos [1]. O objetivo deste trabalho e analisar numericamente o processo de conveccao forcada em arranjo de obstaculos dentro de um canal, cuja velocidade de resfriamento esteja entre 2 a 4 m/s. A Figura 1 mostra o dominio computacional onde sao regidas as equacoes classicas de conservacao (massa, momentum e energia e modelo de turbulencia k-epsilon (k-E) e RNG). O software utilizado para a solucao do problema e o ANSYS FLUENT®. As condicoes de contorno foram temperatura e velocidade de entrada uniformes, fluxo de calor conhecido nos componentes e superficies laterais e da base adiabaticas, as condicoes na saida sao calculadas pelo software.

Nanocomposites are multiphase materials of which, at least one of the phases, has a dimension smaller than 100 nm. These materials have attracted technological and scientific interest due to their multifunctional characteristics and potential, which allow them to combine unique properties which are not found in traditional commercial materials, such as natural rubber alone. The objective of this work is to analyse the toxicity of nanoparticles and nanocomposites when applied to mammal cells in order to obtain bioactive agents, as well as to evaluate the potential to be applied in biological systems. Ferroelectric ceramic nanoparticles of KSr2Nb5O15 (KSN) and paramagnetic ceramic nanoparticles Ni0.5Zn0.5Fe2O4 (NZF) were prepared and utilized to produce functional and multifunctional nanocomposites based on vulcanized natural rubber (NR/KSN and NR/NZF) with different nanoparticle concentrations. For both kinds of nanoparticles and both classes of nanocomposites, independently of the nanoparticle concentration, it is not possible to observe any reduction of the cellular viability until the incubation time is finished. In this way, these results point to the possibility of using these nanoparticles and nanocomposites, from the toxicity point of view, as bioactivity agents in biological systems based on mammalian cells.

Made available in DSpace on 2014-12-03T13:09:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-05-01Bitstream added on 2014-12-03T13:23:13Z : No. of bitstreams: 1 WOS000336642100003.pdf: 2131149 bytes, checksum: 6be06a88966661ec4bc93978ed725cb3 (MD5) Leaks in pipes are a common issue encountered in the water industry. Acoustic methods are generally successful in finding and locating leaks in metallic pipes, however, they are less effective when applied to plastic pipes. This is because leak-noise signals are heavily attenuated due to high damping in the pipe-wall and sound radiation into the soil. As result, high frequency leak noise does not travel long distances. To determine how far leak noise may travel in a pipe at any frequency, the attenuation of the wave responsible for leak noise propagation should be known. In this paper a new method to estimate this is described. The method is then applied to some measurements made on a bespoke pipe-test rig in the UK, and the results are compared with theoretical predictions. Univ Estadual Paulista, Dept Mech Engn, Sao Paulo, SP, Brazil Univ Southampton, Inst Sound & Vibrat Res, Southampton SO9 5NH, Hants, England Hydrosave, Walsall, W Midlands, England South Staffs Water, Walsall, W Midlands, England Univ Estadual Paulista, Dept Mech Engn, Sao Paulo, SP, Brazil

Este trabalho apresenta uma proposta de modelagem para um trocador de calor que opera atraves da ebulicao de um fluido de trabalho, objetivando analisar a distribuicao de temperatura quando utilizado em conjunto nos sistemas eletronicos, visto que os componentes eletronicos estao cada vez menores e dissipando muito mais calor. O trocador de calor estudado e conhecido como vapor chamber. Uma analise numerica utilizando um modelo simplificado de resistencias termicas sera realizada. Este modelo sera criado para ser utilizado no software ANSYS®. A vapor chamber sera representada por varios blocos, cada um com uma resistencia termica efetiva, e a contribuicao de cada bloco na transferencia de calor total sera investigada. Uma vez que o desempenho termico global depende da condutividade termica de cada bloco, a avaliacao podera dizer quais blocos contribuem para uma melhor eficiencia na troca de calor. Os experimentos fornecerao os valores das condutividades termicas necessarios para serem inseridos no modelo computacional, e desta forma, o perfil de temperatura podera ser encontrado.Este modelo e adequado para a monitorizacao de problemas que envolvem falhas em componentes eletronicos devido a alta temperatura.

1, 2, 3 Universidade Estadual Paulista “Julio de Mesquita Filho” – Faculdade de Engenharia, Departamento de Engenharia Mecânica, Ilha Solteira (SP), Brasil, jcfukushima@aluno.feis.unesp.br, tabone@dem.feis.unesp.br, bazani@dem.feis.unesp.br 4 Universidade Estadual Paulista “Julio de Mesquita Filho” – Faculdade de Engenharia, Departamento de Engenharia Civil, Ilha Solteira (SP), Brasil, nataliamic@aluno.feis.unesp.br

Resumo: O problema proposto neste trabalho e a definicao das curvas de operacao de um ventilador centrifugo atraves de simulacao computacional. A definicao dessas curvas se faz necessaria, pois em algumas aplicacoes esses ventiladores podem trabalhar em paralelo e a predicao numerica pode melhorar o desempenho do sistema. Alem do levantamento das curvas de operacao, este trabalho tem como objetivo a exposicao e solucao de problemas inerentes ao processo de simulacao numerica, como uma malha adequada, criterios de convergencia de resultados, definicao de interfaces e condicoes de contorno. Esses resultados foram validados atraves de curvas obtidas experimentalmente de um ventilador centrifugo similar ao do modelo usado.

The compacting of electronic components has been generating problems in maintaining the systems stable, so a thermal study of electronic equipment is one of the most important aspects of these components, in which is indeed decisive for its reliability. Thermal studies on these components consist of experimental tests and computational simulations that will guarantee that the results satisfy or not the requirements of the product specifications. Telecommunication systems involve, in general, thousands of these components, in which are most of the time stored in a type of cabinets. In these cabinets, a large number of devices dissipate heat altering the behavior of the components. This way, they should understand the temperature fields and the air flow inside these systems for the optimization and maintenance of this kind of system. This study had as objective to determine the fields of temperature, and the air flow inside the central phone cabinets, considering forced convection. Through the analysis of experimental results, alterations and optimizations in the positioning and in the amount of boards, components, fans and blowers, was suggested. With the experimental test using wind tunnel, the dissipated potency can be calculated, and it can be included in the computing simulations to do a simplified modeling of the phone cabinets in the commercial program ANSYS ICEPAK®

Este trabajo trata sobre el estudio del comportamiento dinámico de estructura de losa de concreto. Estructuras bastante leves y esbeltas están cada vez más presentes en la construcción civil, y son muy susceptibles a los efectos de vibraciones causadas por los propios usuarios. En este caso, el aislamiento es bastante complejo, y los niveles de vibraciones deben ser controlados por las propias características de la estructura, el cual torna el conocimiento de sus propiedades dinámicas en una condición fundamental para el desarrollo de proyectos que ofrezcan no apenas seguridad, como también conforto a los usuarios. Este trabajo describe la aplicación de una técnica de ajuste de modelado, elaborado por el método de elementos finitos, para el caso de placas.

Univ State Sao Paulo, UNESP, Coll Engn Ilha Solteira, Dept Mech Engn, Ilha Solteira, SP, Brazil

Orientador : Loir Afonso Moreira Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica Resumo: Este trabalho apresenta um elemento subparamétrico hierárquico baseado na versão p do método dos elementos finitos para a análise de placas e cascas. O primeiro nível de aproximação da solução é obtido através do elemento finito quadrilateral quadrático de nove nós da família Lagrangeana, baseado na degeneração de um elemento sólido tridimensional e na formulação de Reissner-Mindlin, com integração numérica consistente. Para outros níveis de aproximação, sucessivos refinamentos hierárquicos são usados, objetivando remover a caracteristica de rigidez excessiva do elemento na análise de placas e cascas finas. Tal formulação é aplicada na análise estática e dinâmica de placas e cascas (finas e moderadamente grossas). Exemplos numéricos são apresentados para mostrar a precisão, eficiência e vantagens da presente formulação. Os resultados numéricos obtidos nos exemplos de aplicação são comparados com soluções analíticas e outras técnicas numéricas, disponíveis na literatura Abstract: This research presents a subparametric hierarchical finite element based on the p-version concept for the analysis of plates and shells. The first level of approximation for the solution is obtained through the isoparametric quadrilateral quadratic nine-no de Lagrangean shell finite element, based on the degeneration of three-dimensional solid element and the Reissner-Mindlin's formulation, with consistent numerical integration. For other approximation levels, successive hierarchical refinements are used, aiming to remove the characteristic of excessive rigidity of the isoparametric element in the analysis ofthin plates and shells. Such formulation is applied to static and dynamic analysis of plates and shells (thin and moderately thick). Numerical examples are presented to show the accuracy, efficiency and advantages of present formulation. Numerical results obtained for the application examples are compared with analytical solutions and other numerical techniques, available in the open literature Doutorado Mecânica dos Sólidos e Projeto Mecânico Doutor em Engenharia Mecânica

Orientador: Loir Afonso Moreira Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica Resumo: Em 1970, Ahmad apresentou uma formulação, para análise de placas e cascas, baseada na degeneração de um elemento tridimensional, através da redução de sua dimensão na direção da espessura. O campo de deslocamento era, então, interpolado a partir das funções de forma da família Serendipity e, para a obtenção das características do elemento, utilizava-se integração numérica consistente. Os resultados obtidos por esse elemento foram excelentes para situações de placas e cascas moderadamente grossas, atendendo, portanto, à teoria de Mindlin-Reissner; contudo, com a redução da espessura, o elemento tomava-se, excessivamente, rígido e os resultados não tendiam, como era de se esperar, àqueles da teoria clássica de Kirchhoff para placas e cascas finas. O objetivo deste trabalho é o estudo comparativo, na análise dinâmica de placas e cascas, entre o desempenho, utilizando-se integração numérica consistente, do elemento finito isoparamétrico, quadrilateral, quadrático, da família Serendipity e do elemento finito isoparamétrico, quadrilateral, quadrático, da família Lagrangeana, obtidos, ambos, a partir da formulação de Ahmad; pretende-se estabelecer, dentre os dois elementos, qual é o mais adequado para iniciar o desenvolvimento de um elemento finito subparamétrico do tipo hierárquico, baseado no conceito da aproximação p, visando retirar a característica de rigidez excessiva do elemento de Ahmad, para situações de placas e cascas finas Abstract: In 1970, Ahmad presented a fonnulation for the analysis of plates and shells, based on the degeneration of three-dimensional solid element, by reducing its dimension in the thickness direction. The displacement field was then interpolated through the shape functions of Serendipity family and, in order to achieve the element characteristics, consistent numerical integration was used. The obtained results were excellent for moderately thick plates and shells applications, being in accordance with the Mindlin-Reissner's theory; however, with the reduction ofthe thickness, the element became excessively rigid and the results did not tend to those of the KirchhofJ's theory for thin plates and shells. The purpose of this work is the comparative study in the dynamic analysis of plates and shells conceming the perfonnance, considering consistent numerical integration, of the isoparametric, quadrilateral, quadratic finite element of Serendipity family and of the isoparametric, quadrilateral, quadratic finite element of Lagrangean family, achieved, both, from the Ahmad's fonnulation; one intends to establish, between both elements, which is the most adequate to start the development of a subparametric hierarchical element, based on the p approximation concept, objectifying to remove the characteristic of excessive rigidity of the Ahmad's element for the situations of thin plates and shells Mestrado Mecânica dos Sólidos e Projeto Mecânico Mestre em Engenharia Mecânica