1000 resultados para Largura dos sarrafos
Resumo:
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
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This work presents a theoretical and experimental analysis about the properties of microstrip antennas with integrated frequency selective surfaces (Frequency Selective Surface - FSS). The integration occurs through the insertion of the FSS on ground plane of microstrip patch antenna. This integration aims to improve some characteristics of the antennas. The FSS using patch-type elements in square unit cells. Specifically, the simulated results are obtained using the commercial computer program CST Studio Suite® version 2011. From a standard antenna, designed to operate in wireless communication systems of IEEE 802.11 a / b / g / n the dimensions of the FSS are varied to obtain an optimization of some antenna parameters such as impedance matching and selectivity in the operating bands. After optimization of the investigated parameters are built two prototypes of microstrip patch antennas with and without the FSS ground plane. Comparisons are made of the results with the experimental results by 14 ZVB network analyzer from Rohde & Schwarz ®. The comparison aims to validate the simulations performed and show the improvements obtained with the FSS in integrated ground plane antenna. In the construction of prototypes, we used dielectric substrates of the type of Rogers Corporation RT-3060 with relative permittivity equal to 10.2 and low loss tangent. Suggestions for continued work are presented
Resumo:
This paper presents an evaluative study about the effects of using a machine learning technique on the main features of a self-organizing and multiobjective genetic algorithm (GA). A typical GA can be seen as a search technique which is usually applied in problems involving no polynomial complexity. Originally, these algorithms were designed to create methods that seek acceptable solutions to problems where the global optimum is inaccessible or difficult to obtain. At first, the GAs considered only one evaluation function and a single objective optimization. Today, however, implementations that consider several optimization objectives simultaneously (multiobjective algorithms) are common, besides allowing the change of many components of the algorithm dynamically (self-organizing algorithms). At the same time, they are also common combinations of GAs with machine learning techniques to improve some of its characteristics of performance and use. In this work, a GA with a machine learning technique was analyzed and applied in a antenna design. We used a variant of bicubic interpolation technique, called 2D Spline, as machine learning technique to estimate the behavior of a dynamic fitness function, based on the knowledge obtained from a set of laboratory experiments. This fitness function is also called evaluation function and, it is responsible for determining the fitness degree of a candidate solution (individual), in relation to others in the same population. The algorithm can be applied in many areas, including in the field of telecommunications, as projects of antennas and frequency selective surfaces. In this particular work, the presented algorithm was developed to optimize the design of a microstrip antenna, usually used in wireless communication systems for application in Ultra-Wideband (UWB). The algorithm allowed the optimization of two variables of geometry antenna - the length (Ls) and width (Ws) a slit in the ground plane with respect to three objectives: radiated signal bandwidth, return loss and central frequency deviation. These two dimensions (Ws and Ls) are used as variables in three different interpolation functions, one Spline for each optimization objective, to compose a multiobjective and aggregate fitness function. The final result proposed by the algorithm was compared with the simulation program result and the measured result of a physical prototype of the antenna built in the laboratory. In the present study, the algorithm was analyzed with respect to their success degree in relation to four important characteristics of a self-organizing multiobjective GA: performance, flexibility, scalability and accuracy. At the end of the study, it was observed a time increase in algorithm execution in comparison to a common GA, due to the time required for the machine learning process. On the plus side, we notice a sensitive gain with respect to flexibility and accuracy of results, and a prosperous path that indicates directions to the algorithm to allow the optimization problems with "η" variables
Resumo:
This work aims to investigate the behavior of fractal elements in planar microstrip structures. In particular, microstrip antennas and frequency selective surfaces (FSSs) had changed its conventional elements to fractal shapes. For microstrip antennas, was used as the radiating element of Minkowski fractal. The feeding method used was microstrip line. Some prototypes were built and the analysis revealed the possibility of miniaturization of structures, besides the multiband behavior, provided by the fractal element. In particular, the Minkowski fractal antenna level 3 was used to exploit the multiband feature, enabling simultaneous operation of two commercial tracks (Wi-Fi and WiMAX) regulated by ANATEL. After, we investigated the effect of switches that have been placed on the at the pre-fractal edges of radiating element. For the FSSs, the fractal used to elements of FSSs was Dürer s pentagon. Some prototypes were built and measured. The results showed a multiband behavior of the structure provided by fractal geometry. Then, a parametric analysis allowed the analysis of the variation of periodicity on the electromagnetic behavior of FSS, and its bandwidth and quality factor. For numerical and experimental characterization of the structures discussed was used, respectively, the commercial software Ansoft DesignerTM and a vector network analyzer, Agilent N5230A model
Resumo:
The main objective of this work is to optimize the performance of frequency selective surfaces (FSS) composed of crossed dipole conducting patches. The optimization process is performed by determining proper values for the width of the crossed dipoles and for the FSS array periodicity, while the length of the crossed dipoles is kept constant. Particularly, the objective is to determine values that provide wide bandwidth using a search algorithm with representation in bioinspired real numbers. Typically FSS structures composed of patch elements are used for band rejection filtering applications. The FSS structures primarily act like filters depending on the type of element chosen. The region of the electromagnetic spectrum chosen for this study is the one that goes from 7 GHz to 12 GHz, which includes mostly the X-band. This frequency band was chosen to allow the use of two X-band horn antennas, in the FSS measurement setup. The design of the FSS using the developed genetic algorithm allowed increasing the structure bandwidth
Resumo:
The increasing demand for high performance wireless communication systems has shown the inefficiency of the current model of fixed allocation of the radio spectrum. In this context, cognitive radio appears as a more efficient alternative, by providing opportunistic spectrum access, with the maximum bandwidth possible. To ensure these requirements, it is necessary that the transmitter identify opportunities for transmission and the receiver recognizes the parameters defined for the communication signal. The techniques that use cyclostationary analysis can be applied to problems in either spectrum sensing and modulation classification, even in low signal-to-noise ratio (SNR) environments. However, despite the robustness, one of the main disadvantages of cyclostationarity is the high computational cost for calculating its functions. This work proposes efficient architectures for obtaining cyclostationary features to be employed in either spectrum sensing and automatic modulation classification (AMC). In the context of spectrum sensing, a parallelized algorithm for extracting cyclostationary features of communication signals is presented. The performance of this features extractor parallelization is evaluated by speedup and parallel eficiency metrics. The architecture for spectrum sensing is analyzed for several configuration of false alarm probability, SNR levels and observation time for BPSK and QPSK modulations. In the context of AMC, the reduced alpha-profile is proposed as as a cyclostationary signature calculated for a reduced cyclic frequencies set. This signature is validated by a modulation classification architecture based on pattern matching. The architecture for AMC is investigated for correct classification rates of AM, BPSK, QPSK, MSK and FSK modulations, considering several scenarios of observation length and SNR levels. The numerical results of performance obtained in this work show the eficiency of the proposed architectures
Resumo:
An cylinder-parabolic solar concentrator is presented to produce steam for different applications. This prototype was built in glass fiber with dimensions that follow a study of optimization of parameters inherent in the optical reflection of sunlight by the surface of reflection and absorption of the same by tubing that leads the fluid of work. The surface of the concentrator of 2.24 m² has been covered by layers of mirror with 1.0 m of lenght and 2.0 cm wide. The absorb tubing consists of a copper tube diameter equal to 28 mm. The concentrator is moving to follow the apparent motion of the sun. It will be presented the processes of manufacturing and assembly of the concentrator proposed, which has as main characteristics the facilities construction and assembly, in addition to reduced cost. Will be presented data from tests performed to produce steam setting up some parameters that diagnose the efficiency of the concentrator. It will be demonstrated the viabilities thermal, economic and of materials of the proposed system.The maximum temperature achieved in the vacuum tube absorber was 232.1°C and average temperature for 1 hour interval was 171.5°C, obtained in a test with automation. The maximum temperature achieved in the output of water was 197.7°C for a temperature of 200.0°C in the absorber tube. The best average result of the water exit temperature to interval of 1 hour was 170.2°C for a temperature of 171.2°C, in the absorber tube, obtained in test with automation. Water exit mean temperatures were always above of the water steaming temperature. The concentrator present a useful efficiency of 38% and a production cost of approximately R$ 450,00 ( $ 160.34)
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The modern technology of materials and structural integrity of pipelines requests the use of inspection tools named inspection pigs to detect, localize and measure the length, width and depth dimensions of the thickness losses of walls of buried and underwater pipelines in service. These tools run them internally, performing and recording measurements, with performance that varies according to the pig s technology. It has been developed recently an instrumented pig technology, called feller pig. This work aims to indicate factors that influence the feller pig technology performance in the detection and in the accuracy of measurement of the length, width and depth dimensions of the thickness losses on the internal surface of an oil pipeline wall under normal conditions of oil pipe inspection with pig. In this work, is made a collection of factors and an analyses of the technology based on the available literature, as well as an experiment to observe the technology and the factors operating. In the experiment, a feeler pig is used in a pipeline built in carbon steel and in operation that flows petroleum, in witch are observed areas with internal thickness losses occurred naturally. Some of these areas and their dimensions taken by automated ultra-sound scanner are compared with the ones indicated by the feller pig. Based on the data collection, on the analysis and on the experiment, the influence of factors object of this research is discussed. It is concluded that, among these, there are factors related to pipe fabrication tolerances, to wear of pig components, to internal adhesive wear of pipeline, to other pipeline damages and to technology characteristics. Finally, actions are suggested to know better, improve and define the applicability of this technology
Resumo:
It s presented a solar collector to be used in a system for heating bath water, whose main characteristic is its low cost. The collector consists of five plates of PVC with 10 mm thick, 200 mm in width and 1400mm in length, with an area equal to 1.4 square meters. The plates were connected in parallel to the ends of PVC tubes of 40 mm and 32 mm. The plates were coated on one side with aluminum sheets of soft drinks and beers cans open. The system worked on a thermosiphon and was tested in two configurations: the plates uncoated and coated with aluminum material, to determine the influence of material on the efficiency of the collector. For both configurations was used EPS plates below the surface to minimize heat losses from the botton. The thermal reservoir of the heating system is, also, alternative and low cost, since it was constructed from a polyethylene tank for storing water, with volume of 150 end 200 liters. It will be presented the thermal efficiency, heat loss, water temperature of the thermal reservoir at the end of the process and simulation of baths for a house with four residents. The will be demonstrated thermal, economic and material viability of the proposed collector, whose main innovation is the use of recyclables materials, cans of beer and soft drinks, to increase the temperature of the absorber plate.
Resumo:
The aim of this study was to determine the response of morphological traits of four tolerant and susceptible sugarcane cultivars (SP81-3250, SP83-2847, RB855453 and RB72454) related to two water regimes. At 84 days after emergence the plants were submitted to water availability treatments (no water deficiency and water deficiency), and evaluated in three periods: zero, 28 and 56 days, after implantation of these treatments (DAT). The cultivars SP81-3250 and SP83-2847, when subjected to water stress for prolonged periods in early development, present higher leaf width, less damage to the green leaf number and leaf area, an increase in stomatal density in adaxial and abaxial leaf surface, and higher production of dry matter, and therefore were considered tolerant. The leaf +3 length not allowed to characterize the varieties to drought tolerance.
Resumo:
It was studied a system for heating water to be used to obtain water for bathing at home, the absorbing surface of the collector is formed by one plate of polycarbonate. The polycarbonate plate has 6 mm thick, 1.050 mm wide and 1.500 mm long with an area equal to 1,575 m². The plate was attached by its edges parallel to PVC tubes of 32 mm. The system worked under the thermo-siphon and was tested for two configurations: plate absorber with and without isolation of EPS of 30 mm thick on the bottom surface in order to minimize heat losses from the bottom. The tank's thermal heating system is alternative and low cost, since it was constructed from a polyethylene reservoir for water storage, with a volume of 200 liters. Will present data on the thermal efficiency, heat loss, water temperature of thermal reservoir at the end of the process simulation and baths. Will be demonstrated the feasibility of thermal, economic and material pickup proposed for the intended purpose.
Resumo:
In 1998 the first decorticator was developed in the Textile Engineering Laboratory and patented for the purpose of extracting fibres from pineapple leaves, with the financial help from CNPq and BNB. The objective of the present work was to develop an automatic decorticator different from the first one with a semiautomatic system of decortication with automatic feeding of the leaves and collection of the extracted fibres. The system is started through a command system that passes information to two engines, one for starting the beater cylinder and the other for the feeding of the leaves as well as the extraction of the decorticated fibres automatically. This in turn introduces the leaves between a knife and a beater cylinder with twenty blades (the previous one had only 8 blades). These blades are supported by equidistant flanges with a central transmission axis that would help in increasing the number of beatings of the leaves. In the present system the operator has to place the leaves on the rotating endless feeding belt and collect the extracted leaves that are being carried out through another endless belt. The pulp resulted form the extraction is collected in a tray through a collector. The feeding of the leaves as well as the extraction of the fibres is controlled automatically by varying the velocity of the cylinders. The semi-automatic decorticator basically composed of a chassis made out of iron bars (profile L) with 200cm length, 91 cm of height 68 cm of width. The decorticator weighs around 300Kg. It was observed that the increase in the number of blades from 8 to twenty in the beater cylinder reduced the turbulence inside the decorticator, which helped to improve the removal of the fibres without any problems as well as the quality of the fibres. From the studies carried out, from each leaf 2,8 to 4,5% of fibres can be extracted. This gives around 4 to 5 tons of fibres per hectare, which is more than that of cotton production per hectare. This quantity with no doubt could generate jobs to the people not only on the production of the fibres but also on their application in different areas
Resumo:
Os objetivos deste trabalho foram desenvolver e avaliar o rendimento operacional de um equipamento para controle de plantas aquáticas, além de estabelecer procedimentos que permitissem a otimização dessa prática na UHE de Americana-SP. O equipamento constitui-se de uma esteira de margem (3,0 m de largura x 10,0 m de comprimento) para captação e condução das plantas até um picador, que as fragmenta antes do descarte, facilitando assim sua decomposição e seu transporte. A análise realizada indicou que a capacidade operacional foi de aproximadamente 7,73 m³ h-1. Considerando-se a menor taxa de crescimento observada no histórico do reservatório, 2,27%, o sistema deveria permitir a remoção de aproximadamente 28 m³ h-1. Dessa forma, esse equipamento pode funcionar como um método auxiliar no controle das plantas aquáticas, não realizando um controle efetivo se empregado de forma isolada.
Resumo:
Os ensaios de largura de trabalho e uniformidade de distribuição são de difícil execução para o agricultor por exigirem equipamentos, recursos e métodos complexos. Portanto, este trabalho teve como objetivo avaliar coletores alternativos para tornar mais acessível a regulagem e a avaliação de distribuidores de fertilizantes sólidos a lanço. Foram utilizados quatro diferentes conjuntos de coletores: i) coletores construídos segundo a norma ISO 5690/1; ii) coletores de polietileno (bandejas plásticas) com tela de sombreamento para evitar o ricochete de material; iii) coletores formados por caixas de leite longa vida, e iv) coletores formados por vasos de polietileno (número 3,5). Também foram utilizados três diferentes distribuidores para as avaliações. Os coletores alternativos apresentaram maior retenção de partículas que os coletores normatizados. A largura efetiva de trabalho obtida para os coeficientes de variação de 12,5; 15; 17,5 e 20% variou entre os coletores nos diferentes percursos. O coletor que mais se assemelhou à norma foram os vasos de polietileno. Constatou-se que a altura dos coletores foi mais importante para sua eficiência do que a sua área de coleta.
Resumo:
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)