9 resultados para Two-point boundary value problems
em Universidade Federal do Rio Grande do Norte(UFRN)
Resumo:
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 espectral de reflectarrays com substrato de duas camadas dielétricas anisotrópicas uniaxiais
Resumo:
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
Resumo:
This paper has two objectives: (i) conducting a literature search on the criteria of uniqueness of solution for initial value problems of ordinary differential equations. (ii) a modification of the method of Euler that seems to be able to converge to a solution of the problem, if the solution is not unique
Resumo:
The present work is an initiative of undertaking a perspective that values the aspects of the city in its diversity. The one that t intends is to discuss the urbanity starting from the aspect of the image, of the history, and about main point, to value the point of the individual's view that lives the urban space in its more several configurations: the house, the street, the neighborhood, and the city in wider scale. The described historical research defines the city as space of the human accomplishments. When analyzing the moments of the most recent history of the urban life the modernity/post-modernity notions they are explored in the sense of illuminating the wealth, continuity and it breaks of patterns of behavior, and on the other hand, to describe a I overfly in the several times of the city. The prominences of aspects of the archaeology and of the descriptive resource they are related, for its time, the most punctual perspective of the practical research, the instance of the neighborhood, specifically High City and Riverside, configuring an immersion in the daily more punctual of the city, valuing forms of being, aiming the perspective of the personal computer as point-of-view. The images of the city assume the paper of representing the documental about the current features of the urbanity. It is without a doubt that at the present time the photographic image already possesses a paper of prominence it is as research instrument, be as main source for a work on files of photos. The photographic images in the present work possess a prominence place, focusing specific places of the city in the time. Finally, the individual's voice valued under the perspective on as the person's knowledge that inhabits and live the urbanity he/she understands the knowledge of the life in the city and, more than in any other place, a middle where the loss of action models is pointed very easily tends in view the dynamic movement of the practices and renewal of new indications; in the same space in that becomes urgent to build marks starting from which the individual can shimmer the future. And in that space the individual's voice is valued as rich source of information on living the scenery of conflicts of the present time
Resumo:
Microstrip antennas are widely used in modern telecommunication systems. This is particularly due to the great variety of geometries and because they are easily built and integrated to other high frequency devices and circuits. This work presents a study of the properties of the microstrip antenna with an aperture impressed in the conducting patch. Besides, the analysis is performed for isotropic and anisotropic dielectric substrates. The Multiport Network Model MNM is used in combination with the Segmentation Method and the Greens function technique in the analysis of the considered microstrip antenna geometries. The numerical analysis is performed by using the boundary value problem solution, by considering separately the impedance matrix of the structure segments. The analysis for the complete structure is implemented by choosing properly the number and location of the neighboor element ports. The numerial analysis is performed for the following antenna geometries: resonant cavity, microstrip rectangular patch antenna, and microstrip rectangular patch antenna with aperture. The analysis is firstly developed for microstrip antennas on isotropic substrates, and then extended to the case of microstrip antennas on anisotropic substrates by using a Mapping Method. The experimental work is described and related to the development of several prototypes of rectangular microstrip patch antennas wtih and without rectangular apertures. A good agreement was observed between the simulated and measured results. Thereafter, a good agreement was also observed between the results of this work and those shown in literature for microstrip antennas on isotropic substrates. Furthermore, results are proposed for rectangular microstrip patch antennas wtih rectangular apertures in the conducting patch
Resumo:
The professional profile of public administrators in Brazil is changing very rapidly in recent years, seeking to meet the principle of efficiency by public agencies at all levels. The admission of the permanent government employee under the Public Administration is by competition, however, commissioned positions are free appointment of managers, which allows effective participation of external experts according to their respective standards and norms. In this context, this dissertation seeks to understand the main characteristics of the profile of the occupants of commissioned positions in Direct Public Administration of the State of Rio Grande do Norte, noting the differences between those with functional link with the have nots. For this study, by data collection and content analysis, a mapping of the administrative structure of the Government of the State of Rio Grande do Norte was done, i.e., the organization of the Executive Branch, which is regulated by the Complementary Law no. 163/1999 and its amendments, which consists of 53 (fifty three) entities, these 29 (twenty nine) are agencies of the direct administration and the remaining 24 (twenty four) comprises the indirect administration. With the collected data, analysis on the number of commissioned positions of each organ of the State of Rio Grande do Norte and information on education, age, length of service, gender and functional link with the direct administration was carried out. Data were available from SEARH in June/2013, when they totaled 58,733 (fifty-eight thousand seven hundred thirty-three) servers, these 2.15% (two point fifteen percent) occupy commissioned positions, corresponding to 1,262 commissioned positions under the Direct Administration, below the national average of 4% (four percent). Of total commissioned positions 64.7% (sixty-four point seven percent) have no functional link with the direct administration, while only 35.3% (thirty -five point three percent) have functional link. It was noticed that there are no clear and specific criteria for the appointments of commissioned positions in the State. They occur freely, as provided in the State Constitution. Another conclusion is the importance of Public Administration define and improve their capacity, competence and efficiency in the delivery of public services. For that it is necessary to invest in their workforce composed of permanent employees and commissioned positions to define the appropriate professional profile
Resumo:
In this work we have elaborated a spline-based method of solution of inicial value problems involving ordinary differential equations, with emphasis on linear equations. The method can be seen as an alternative for the traditional solvers such as Runge-Kutta, and avoids root calculations in the linear time invariant case. The method is then applied on a central problem of control theory, namely, the step response problem for linear EDOs with possibly varying coefficients, where root calculations do not apply. We have implemented an efficient algorithm which uses exclusively matrix-vector operations. The working interval (till the settling time) was determined through a calculation of the least stable mode using a modified power method. Several variants of the method have been compared by simulation. For general linear problems with fine grid, the proposed method compares favorably with the Euler method. In the time invariant case, where the alternative is root calculation, we have indications that the proposed method is competitive for equations of sifficiently high order.
Resumo:
With the increasing complexity of software systems, there is also an increased concern about its faults. These faults can cause financial losses and even loss of life. Therefore, we propose in this paper the minimization of faults in software by using formally specified tests. The combination of testing and formal specifications is gaining strength in searches mainly through the MBT (Model-Based Testing). The development of software from formal specifications, when the whole process of refinement is done rigorously, ensures that what is specified in the application will be implemented. Thus, the implementation generated from these specifications would accurately depict what was specified. But not always the specification is refined to the level of implementation and code generation, and in these cases the tests generated from the specification tend to find fault. Additionally, the generation of so-called "invalid tests", ie tests that exercise the application scenarios that were not addressed in the specification, complements more significantly the formal development process. Therefore, this paper proposes a method for generating tests from B formal specifications. This method was structured in pseudo-code. The method is based on the systematization of the techniques of black box testing of boundary value analysis, equivalence partitioning, as well as the technique of orthogonal pairs. The method was applied to a B specification and B test machines that generate test cases independent of implementation language were generated. Aiming to validate the method, test cases were transformed manually in JUnit test cases and the application, created from the B specification and developed in Java, was tested. Faults were found with the execution of the JUnit test cases
Resumo:
Formal methods and software testing are tools to obtain and control software quality. When used together, they provide mechanisms for software specification, verification and error detection. Even though formal methods allow software to be mathematically verified, they are not enough to assure that a system is free of faults, thus, software testing techniques are necessary to complement the process of verification and validation of a system. Model Based Testing techniques allow tests to be generated from other software artifacts such as specifications and abstract models. Using formal specifications as basis for test creation, we can generate better quality tests, because these specifications are usually precise and free of ambiguity. Fernanda Souza (2009) proposed a method to define test cases from B Method specifications. This method used information from the machine s invariant and the operation s precondition to define positive and negative test cases for an operation, using equivalent class partitioning and boundary value analysis based techniques. However, the method proposed in 2009 was not automated and had conceptual deficiencies like, for instance, it did not fit in a well defined coverage criteria classification. We started our work with a case study that applied the method in an example of B specification from the industry. Based in this case study we ve obtained subsidies to improve it. In our work we evolved the proposed method, rewriting it and adding characteristics to make it compatible with a test classification used by the community. We also improved the method to support specifications structured in different components, to use information from the operation s behavior on the test case generation process and to use new coverage criterias. Besides, we have implemented a tool to automate the method and we have submitted it to more complex case studies