Ressoador retangular defenda com quatro camadas fotônicas

Recently, planar antennas have attracted interest due to its characteristics as well as the advantages they offer compared to other types of antennas. In the area of mobile communications the need for such antennas has become increasingly intense due to development, which requires antennas that operate in multifrequency and broadband. The microstrip antennas have narrow bandwidth due to losses in the dielectric caused by irradiation. Another limitation is the radiation pattern degradation due to generation of surface waves in the substrate. Some techniques are being developed to minimize this bandwidth limitation, as is the case in the study of type materials PBG - Photonic Band Gap, to compose the dielectric material. The analysis developed in this work were performed with use of the method LTT - Transverse Transmission Line, in the field of Fourier transform that uses a component propagating in the y direction (transerve real direction of propagation z), thus treating the general equations of the fields electric and magnetic fields as a functions of y E and Hy . This work has as main objective the method LTT structures resonator line slot with four layers of material photonic PBG, for obtaining the complex resonant frequency and efficiency of this structure. PBG theory is applied to obtain the relative permittivity for the substrate biases sep compounds photonic material. Numerical-computational results in graph form in two dimensions for all the analysis are presented for the proposed structures that have photonic materials, as substrates

Acoplador e linha de lâmina unilateral e bilateral com substrato fotônico

The aim of this work is to characterize and use the characteristic parameters of the planar structures constructed with fin lines looking for their applications in devices, using PBG Photonic Band Gap photonic materials as substrate, operating in the millimeter and optic wave bands.The PBG theory will be applied for the relative permittivity attainment for the PBG photonic substrate s and p polarizations. The parameters considered in the structures characterization are the complex propagation constant and the characteristic impedance of unilateral and bilateral fin lines that were obtained by the use of the TTL Transverse Transmission Line Method, together with the Method of the Moments. The final part of this work comprises studies related to the behavior of the asymmetric unilateral fin line coupler with photonic substrate. This research opens perspectives for new works in this modern area. Numerical results are shown by means of bi-dimensional and three-dimensional graphics. Conclusions and suggestions for future works are also presented

Otimização do controle eletrônico do diagrama de radiação de arranjos de antenas usando algoritmos genéticos com codificação real

Antenna arrays are able to provide high and controlled directivity, which are suitable for radiobase stations, radar systems, and point-to-point or satellite links. The optimization of an array design is usually a hard task because of the non-linear characteristic of multiobjective, requiring the application of numerical techniques, such as genetic algorithms. Therefore, in order to optimize the electronic control of the antenna array radiation pattem through genetic algorithms in real codification, it was developed a numerical tool which is able to positioning the array major lobe, reducing the side lobe levels, canceling interference signals in specific directions of arrival, and improving the antenna radiation performance. This was accomplished by using antenna theory concepts and optimization methods, mainly genetic algorithms ones, allowing to develop a numerical tool with creative genes codification and crossover rules, which is one of the most important contribution of this work. The efficiency of the developed genetic algorithm tool is tested and validated in several antenna and propagation applications. 11 was observed that the numerical results attend the specific requirements, showing the developed tool ability and capacity to handle the considered problems, as well as a great perspective for application in future works.

Predicao de campo em comunicacao sem fio

Even living in the XXI century are still some difficulties in access to broadband Internet in several Brazilian cities, due to the purchasing power of people and lack of government investment. But even with these difficulties, we seek to encourage the use of wireless technology, which is based on the IEEE 802.11b protocol - also known as Wi-Fi (Wireless Fidelity) Wireless Fidelity Communications, having wide range of commercial applications in the world market, nationally and internationally. In Brazil, this technology is in full operation in major cities and has proved attractive in relation to the access point to multipoint and point-to-point. This paper is a comparative analysis of prediction field, using models based on the prediction of propagation loss. To validate the techniques used here, the Okumura-Hata models, modified Okumura-Hata, Walfisch-Ikegami model, were applied to a wireless computer network, located in the neighborhood of Cajupiranga in the city of Melbourn, in Rio Grande do Norte . They are used for networking wireless 802.11b, using the Mobile Radio to measure signal levels, beyond the heights of the antennas and distances from the transmitter. The performance data versus distance are added to the graphs generated and compared with results obtained through calculations of propagation models

Análise espectral de reflectarrays com substratos de duas camadas dielétricas anisotrópicas uniaxiais

Recently, an amazing development has been observed in telecommunication systems. Two good examples of this development are observed in mobile communication and aerospace systems. This impressive development is related to the increasing need for receiving and transmitting communication signals. Particularly, this development has required the study of new antennas and filters. This work presents a fullwave analysis of reflectarrays. The considered structures are composed by arrays of rectangular conducting patches printed on multilayer dieletric substrates, that are mounted on a ground plane. The analysis is developed in the spectral domain, using an equivalent transmission line method in combination with Galerkin method. Results for the reflection coefficient of these structures are presented and compared to those available in the literature. A good agreement was observed. Particularly, the developed analysis uses the transmission lines theory in combination with the incident potentials and the field continuity equations, at the structures interfaces, for obtaining the scattered field components expressions as function of the patch surface currents and of the incident field. Galerkin method is used to determine the unknown coefficients in the boundary value problem. Curves for the reflection coefficient of several reflectarray geometries are presented as function of frequency and of the structural parameters

Análise do espalhamento espectral em superfícies de estruturas complexas para comunicações móveis

In this work, the transmission line method is explored on the study of the propagation phenomenon in nonhomogeneous walls with finite thickness. It is evaluated the efficiency and applicability of the method, considering materials like gypsum, wood and brick, found in the composition of the structures of walls in question. The results obtained in this work are compared to those available in the literature, for several particular cases. A good agreement is observed, showing that the performed analysis is accurate and efficient in modeling, for instance, the wave propagation through building walls and integrated circuit layers in mobile communication and radar system applications. Later, simulations of resistive sheets devices such as Salisbury screens and Jaumann absorbers and of transmission lines made of metal-insulator-semiconductor (MIS) are made. Thereafter, it is described a study on frequency surface selective structures (FSS). It is proposed the development of devices and microwave integrated circuits (MIC) of such structures, for the accomplishment of experiments. Finally, future works are suggested, for instance, on the development of reflectarrays, frequency selective surfaces with dissimilar elements, and coupled frequency selective surfaces with elements located on different layers

Aplicação do método LTT às estruturas retangulares e triangulares em multicamadas e empilhadas em substratos PBG para comunicações móveis

Recently the planar antennas have been studied due to their characteristics as well as the advantages that they offers when compared with another types of antennas. In the mobile communications area, the need for this kind of antennas have became each time bigger due to the intense increase of the mobile communications that needs of antennas which operate in multifrequency and wide bandwidth. The microstrip antennas presents narrow bandwidth due the loss in the dielectric generated by radiation. Another limitation is the radiation pattern degradation due the generation of surface waves in the substrate. In this work some used techniques to minimize the disadvantages (previously mentioned) of the use of microstrip antennas are presented, those are: substrates with PBG material - Photonic Bandgap, multilayer antennas and with stacked patches. The developed analysis in this work used the TTL - Transverse Transmission Line method in the domain of Fourier transform, that uses a component of propagation in the y direction (transverse to the direction real of propagation z), treating the general equations of electric and magnetic field as functions of y and y . This work has as objective the application of the TTL method to microstrip structures with single and multilayers of rectangular and triangular patches, to obtaining the resonance frequency and radiation pattern of each structure. This method is applied for the treatment of the fields in stacked structures. The Homogenization theory will be applied to obtaining the effective permittivity for s and p polarizations of the substrate composed of PBG material. Numerical results for the triangular and rectangular antennas with single layer, multilayers resonators with triangular and rectangular patches are presented (in photonic and isotropic substrates). Conclusions and suggestions for continuity of this work are presented

Utilização do Linux como ferramanenta antivírus em redes corporativas

Apresentamos um sistema implementado em Linux® com o intuito de proteger redes contendo estações de trabalho Windows® contra agentes maliciosos. O sistema, denominado LIV - Linux® Integrated Viruswall, agrega características existentes em outras soluções e acrescenta novas funcionalidades. Uma das funcionalidades implementadas é a capacidade de detecção de estações de trabalho contaminadas tendo como base a análise do tráfego de rede. Outra é o uso de uma técnica denominada compartilhamento armadilha para identificar agentes maliciosos em propagação na rede local. Uma vez detectado um foco de contaminação, o LIV é capaz de isolá-lo da rede, contendo a difusão do agente malicioso. Resultados obtidos pelo LIV na proteção de uma rede corporativa demonstram a eficácia da análise do tráfego de rede como instrumento de detecção de agentes maliciosos, especialmente quando comparada a mecanismos tradicionais de detecção, baseados exclusivamente em assinaturas digitais de códigos maliciosos

Método dinâmico aplicado para antenas cilíndricas

Nowadays there has been a major breakthrough in the aerospace area, with regard to rocket launches to research, experiments, telemetry system, remote sensing, radar system (tracking and monitoring), satellite communications system and insertion of satellites in orbit. This work aims at the application of a circular cylindrical microstrip antenna, ring type, and other cylindrical rectangular in structure of a rocket or missile to obtain telemetry data, operating in the range of 2 to 4 GHz, in S-band. Throughout this was developed just the theoretical analysis of the Transverse transmission line method which is a method of rigorous analysis in spectral domain, for use in rockets and missiles. This analyzes the spread in the direction "ρ" , transverse to dielectric interfaces "z" and "φ", for cylindrical coordinates, thus taking the general equations of electromagnetic fields in function of e [1]. It is worth mentioning that in order to obtain results, simulations and analysis of the structure under study was used HFSS program (High Frequency Structural Simulator) that uses the finite element method. With the theory developed computational resources were used to obtain the numerical calculations, using Fortran Power Station, Scilab and Wolfram Mathematica ®. The prototype was built using, as a substrate, the ULTRALAM ® 3850, of Rogers Corporation, and an aluminum plate as a cylindrical structure used to support. The agreement between the measured and simulated results validate the established processes. Conclusions and suggestions are presented for continuing this work

Avaliação de desempenho da codificação wavelet em canais seletivos em frequência

Wavelet coding has emerged as an alternative coding technique to minimize the fading effects of wireless channels. This work evaluates the performance of wavelet coding, in terms of bit error probability, over time-varying, frequency-selective multipath Rayleigh fading channels. The adopted propagation model follows the COST207 norm, main international standards reference for GSM, UMTS, and EDGE applications. The results show the wavelet coding s efficiency against the inter symbolic interference which characterizes these communication scenarios. This robustness of the presented technique enables its usage in different environments, bringing it one step closer to be applied in practical wireless communication systems

Análise espectral de reflectarrays com substrato de duas camadas dielétricas anisotrópicas uniaxiais

Recently, an amazing development has been observed in telecommunication systems. Two good examples of this development are observed in mobile communication and aerospace systems. This impressive development is related to the increasing need for receiving and transmitting communication signals. Particularly, this development has required the study of new antennas and filters. This work presents a fullwave analysis of reflectarrays. The considered structures are composed by arrays of rectangular conducting patches printed on multilayer dieletric substrates, that are mounted on a ground plane. The analysis is developed in the spectral domain, using an equivalent transmission line method in combination with Galerkin method. Results for the reflection coefficient of these structures are presented and compared to those available in the literature. A good agreement was observed. Particularly, the developed analysis uses the transmission lines theory in combination with the incident potentials and the field continuity equations, at the structures interfaces, for obtaining the scattered field components expressions as function of the patch surface currents and of the incident field. Galerkin method is used to determine the unknown coefficients in the boundary value problem. Curves for the reflection coefficient of several reflectarray geometries are presented as function of frequency and of the structural parameters

Desgaste de polímeros estruturais de engenharia em contato de deslizamento com cilindro metálico

Present work proposed to map and features the wear mechanisms of structural polymers of engineering derived of the sliding contact with a metallic cylindrical spindle submitted to eccentricity due to fluctuations in it is mass and geometric centers. For this it was projected and makes an experimental apparatus from balancing machine where the cylindrical counterbody was supported in two bearings and the polymeric coupon was situated in a holder with freedom of displacement along counterbody. Thus, the experimental tests were standardized using two position of the two bearings (Fixed or Free) and seven different positions along the counterbody, that permit print different conditions to the stiffness from system. Others parameters as applied normal load, sliding velocity and distance were fixed. In this investigation it was used as coupon two structural polymers of wide quotidian use, PTFE (polytetrafluroethylene) and PEEK (poly-ether-ether-ketone) and the AISI 4140 alloy steel as counterbody. Polymeric materials were characterized by thermal analysis (thermogravimetric, differential scanning calorimetry and dynamic-mechanical), hardness and rays-X diffractometry. While the metallic material was submitted at hardness, mechanical resistance tests and metallographic analysis. During the tribological tests were recorded the heating response with thermometers, yonder overall velocity vibration (VGV) and the acceleration using accelerometers. After tests the wear surface of the coupons were analyzed using a Scanning Electronic Microscopy (SEM) to morphological analysis and spectroscopy EDS to microanalysis. Moreover the roughness of the counterbody was characterized before and after the tribological tests. It was observed that the tribological response of the polymers were different in function of their distinct molecular structure. It were identified the predominant wear mechanisms in each polymer. The VGV of the PTFE was smaller than PEEK, in the condition of minimum stiffness, in function of the higher loss coefficient of that polymer. Wear rate of the PTFE was more of a magnitude order higher than PEEK. With the results was possible developed a correlation between the wear rate and parameter (E/ρ)1/2 (Young modulus, E, density, ρ), proportional at longitudinal elastic wave velocity in the material.

Efeito da adição de argila expandida e adições minerais na formulação de concretos estruturais leves autoadensáveis

The search for alternative materials with lower density, reduction in heat transfer and propagation of noise associated with the ease of handling and application in concrete structures, represents an enormous challenge in the formulation and knowledge of the performance of self-compacting lightweight concrete, which has technology little known nationally, and appears on the international scene as an innovative material and alternative to conventional concrete. Based on these, this study set out to study self-compacting lightweight concrete made with two distinct grades of expanded clay associated with the addition of plasticizing/superplasticizers additives and mineral additions of metakaolin and bagasse ash of sugar cane. There is also an object of study, evaluation of pozzolanic activity of mineral admixtures and their influence on the durability characteristics of concrete. The rheological, physical, mechanical and microstructural analysis in this study served as basis in the classification of concretes autoadensáveis, targeting the national technical requirements for their classification in the category autoadensável and lightweight structural. The inclusion of mineral admixtures (metakaolin and bagasse ash of sugar cane), partial replacement of cement, pozzolanic activity and demonstrated maintenance of mechanical properties through the filler effect, a reduction of up to 76% of the nitrogen gas permeability in blend with 20% bagasse ash. All concretes had rheology (cohesion and consistency) suitable for self-adensability as well as strength and density inherent structural lightweight concrete without presenting phenomena of segregation and exudation

Envelhecimento ambiental acelerado em PRF a base de tecidos híbridos kevlar/vidro: propriedades e instabilidade estrutural

There are a number of damaging mechanisms that various materials can suffer in service. However, when working with polymer composite materials, this is something that requires analysis, especially when exposed to adverse environmental conditions. Thus, the objective of the present thesis is the study of the direct influence of environmental aging and the form of hybridization of the reinforcement woven on the structural stability, surfacedegradation and fracture process of polymer composites laminates. For this, the development of two polymer composite laminates was necessary, where one of them was reinforced with a bi-directional woven with hybrid strandsofkevlar-49/glass-Efibers, and the other also with a bi-directionalwoven, however with weft and warpformed of alternating strandsof Kevlar-49 fibers and glass-E fiber The reinforcementwoven are industrially manufactured. Both laminates use a polyester resin as a matrixand are made up of four layers each. All laminates were industrially prepared by the hand lay-up method of manufacturing. To do this, test specimens were manufactured of the respective laminates and submitted to environmental aging accelerated through the aging chamber. They were exposed to alternating cycles of UV radiation and moisture (heated steam) for a standard defined period. At the end of the exposure period the specimens were subjected to mechanical tests of uniaxial tensile and bending in three points and to the characterizationsof the fracture and surface deterioration. In addition, they were submitted to a structural degradation assessment by the measurement of mass variation technique (MMVT) and the measurement of thickness variation technique (MTVT), this last technique being developed in this thesis. At the end of the analysis it was observed that the form of hybridization of the reinforcement woven and the aging process directly influence with losses or gain in mechanical properties, with losses in the structural degradation and in the formation and propagation of damage mechanism of the developedcomposite laminates

Avaliação da produção de sedimento na bacia hidrográfica do rio Potengi através do modelo SWAT

Anthropic disturbances in watersheds, such as inappropriate building development, disorderly land occupation and unplanned land use, may strengthen the sediment yield and the inflow into the estuary, leading to siltation, changes in the reach channel conformation, and ecosystem/water quality problems. Faced with such context, this study aims to assess the applicability of SWAT model to estimate, even in a preliminary way, the sediment yield distribution along the Potengi River watershed, as well as its contribution to the estuary. Furthermore, an assessment of its erosion susceptibility was used for comparison. The susceptibility map was developed by overlaying rainfall erosivity, soil erodibility, the slope of the terrain and land cover. In order to overlap these maps, a multi-criteria analysis through AHP method was applied. The SWAT was run using a five year period (1997-2001), considering three different scenarios based on different sorts of human interference: a) agriculture; b) pasture; and c) no interference (background). Results were analyzed in terms of surface runoff, sediment yield and their propagation along each river section, so that it was possible to find that the regions in the extreme west of the watershed and in the downstream portions returned higher values of sediment yield, reaching respectively 2.8 e 5.1 ton/ha.year, whereas central areas, which were less susceptible, returned the lowest values, never more than 0.7 ton/ha.ano. It was also noticed that in the west sub-watersheds, where one can observe the headwaters, sediment yield was naturally forced by high declivity and weak soils. In another hand, results suggest that the eastern part would not contribute to the sediment inflow into the estuary in a significant way, and the larger part of the sediment yield in that place is due to anthropic activities. For the central region, the analysis of sediment propagation indicates deposition predominance in opposition to transport. Thus, it s not expected that isolated rain storms occurring in the upstream river portions would significantly provide the estuary with sediment. Because the model calibration process hasn t been done yet, it becomes essential to emphasize that values presented here as results should not be applied for pratical aims. Even so, this work warns about the risks of a growth in the alteration of natural land cover, mainly in areas closer to the headwaters and in the downstream Potengi River