897 resultados para topologia complessi simpliciali casuali omologia topologia algebrica applicata probabilità grafi casuali gruppo fondamentale


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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

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Several clinic evaluations have been possible with radiobiocomplexes labeled with technetium-99m (99mTc). Some natural and synthetic drugs are capable of to interfere on the labeling of blood constituents with 99mTc, as well as on the biodistribution of radiobiocomplexes. Authors have also reported about the toxicity of several natural products. The aim of this study was to compare the effects of the Mentha crispa (hortelã) and of the Hypericum perforatum (hipérico) in different experimental models. On the labeling of red blood cells (RBC) and plasma and cellular proteins with 99mTc, both extracts were capable of to decrease the radioactivity percentage on the cellular compartment and on the fixation on plasma and cellular proteins. On the morphometry of the RBC, only the hortelã was capable to alter the shape and the perimeter/area ratio of the RBC. On the biodistribution of the radiobiocomplex sodium pertechnetate (Na99mTcO4), the hortelã increased the Na99mTcO4 distribution in the kidney, spleen, liver and thyroid, meanwhile the hipérico decreased the Na99mTcO4 distribution in the bone, stomach, lungs and thyroid, and increased the Na99mTcO4 distribution in the pancreas. On the bacterial cultures survival, the hipérico was capable of to protect the bacteria against the stannous chloride (SnCl2) effect. The hipérico did not alter the topology of plasmidial DNA and did not protect the plasmidial DNA against the SnCl2 action. Probably, the effects presented by both extracts could be due to chemical compounds of the extracts that could alter the morphology of the RBC and the plasma membrane ions transport, and/or by phytocomplexes that could be formed with different effects dependent on the biological system considered

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The SONET/SDH Ring Assignment Problem (PALAS) treats to group localities in form of some rings, being respected the traffic's limitations of the equipment. Each ring uses a DXC (Digital Cross Connect) to make the communication with the others, being the DXC the equipment most expensive of the net, minimizing the number total of rings, will minimize the total net cost, problem's objective . This topology in rings provides a bigger capacity of regeneration. The PALAS is a problem in Combinatorial Optimization of NP-hard Class. It can be solved through Heuristics and Metaheuristics. In this text, we use Taboo Search while we keep a set of elite solutions to be used in the formation of a part of the collection of vocabulary's parts that in turn will be used in the Vocabulary Building. The Vocabulary Building will be started case Taboo Search does not reach the best solution for the instance. Three approaches had been implemented: one that only uses vocabulary's parts deriving of Taboo Search, one that it only uses vocabulary's parts randomly generated and a last one that it uses half come of the elite and half randomly generated

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The objective of this thesis is proposes a method for a mobile robot to build a hybrid map of an indoor, semi-structured environment. The topological part of this map deals with spatial relationships among rooms and corridors. It is a topology-based map, where the edges of the graph are rooms or corridors, and each link between two distinct edges represents a door. The metric part of the map consists in a set of parameters. These parameters describe a geometric figure which adapts to the free space of the local environment. This figure is calculated by a set of points which sample the boundaries of the local free space. These points are obtained with range sensors and with knowledge about the robot s pose. A method based on generalized Hough transform is applied to this set of points in order to obtain the geomtric figure. The building of the hybrid map is an incremental procedure. It is accomplished while the robot explores the environment. Each room is associated with a metric local map and, consequently, with an edge of the topo-logical map. During the mapping procedure, the robot may use recent metric information of the environment to improve its global or relative pose

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Internet applications such as media streaming, collaborative computing and massive multiplayer are on the rise,. This leads to the need for multicast communication, but unfortunately group communications support based on IP multicast has not been widely adopted due to a combination of technical and non-technical problems. Therefore, a number of different application-layer multicast schemes have been proposed in recent literature to overcome the drawbacks. In addition, these applications often behave as both providers and clients of services, being called peer-topeer applications, and where participants come and go very dynamically. Thus, servercentric architectures for membership management have well-known problems related to scalability and fault-tolerance, and even peer-to-peer traditional solutions need to have some mechanism that takes into account member's volatility. The idea of location awareness distributes the participants in the overlay network according to their proximity in the underlying network allowing a better performance. Given this context, this thesis proposes an application layer multicast protocol, called LAALM, which takes into account the actual network topology in the assembly process of the overlay network. The membership algorithm uses a new metric, IPXY, to provide location awareness through the processing of local information, and it was implemented using a distributed shared and bi-directional tree. The algorithm also has a sub-optimal heuristic to minimize the cost of membership process. The protocol has been evaluated in two ways. First, through an own simulator developed in this work, where we evaluated the quality of distribution tree by metrics such as outdegree and path length. Second, reallife scenarios were built in the ns-3 network simulator where we evaluated the network protocol performance by metrics such as stress, stretch, time to first packet and reconfiguration group time

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There are some approaches that take advantage of unused computational resources in the Internet nodes - users´ machines. In the last years , the peer-to-peer networks (P2P) have gaining a momentum mainly due to its support for scalability and fault tolerance. However, current P2P architectures present some problems such as nodes overhead due to messages routing, a great amount of nodes reconfigurations when the network topology changes, routing traffic inside a specific network even when the traffic is not directed to a machine of this network, and the lack of a proximity relationship among the P2P nodes and the proximity of these nodes in the IP network. Although some architectures use the information about the nodes distance in the IP network, they use methods that require dynamic information. In this work we propose a P2P architecture to fix the problems afore mentioned. It is composed of three parts. The first part consists of a basic P2P architecture, called SGrid, which maintains a relationship of nodes in the P2P network with their position in the IP network. Its assigns adjacent key regions to nodes of a same organization. The second part is a protocol called NATal (Routing and NAT application layer) that extends the basic architecture in order to remove from the nodes the responsibility of routing messages. The third part consists of a special kind of node, called LSP (Lightware Super-Peer), which is responsible for maintaining the P2P routing table. In addition, this work also presents a simulator that validates the architecture and a module of the Natal protocol to be used in Linux routers

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The greater part of monitoring onshore Oil and Gas environment currently are based on wireless solutions. However, these solutions have a technological configuration that are out-of-date, mainly because analog radios and inefficient communication topologies are used. On the other hand, solutions based in digital radios can provide more efficient solutions related to energy consumption, security and fault tolerance. Thus, this paper evaluated if the Wireless Sensor Network, communication technology based on digital radios, are adequate to monitoring Oil and Gas onshore wells. Percent of packets transmitted with successful, energy consumption, communication delay and routing techniques applied to a mesh topology will be used as metrics to validate the proposal in the different routing techniques through network simulation tool NS-2

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The reconfiguration of a distribution network is a change in its topology, aiming to provide specific operation conditions of the network, by changing the status of its switches. It can be performed regardless of any system anomaly. The service restoration is a particular case of reconfiguration and should be performed whenever there is a network failure or whenever one or more sections of a feeder have been taken out of service for maintenance. In such cases, loads that are supplied through lines sections that are downstream of portions removed for maintenance may be supplied by the closing of switches to the others feeders. By classical methods of reconfiguration, several switches may be required beyond those used to perform the restoration service. This includes switching feeders in the same substation or for substations that do not have any direct connection to the faulted feeder. These operations can cause discomfort, losses and dissatisfaction among consumers, as well as a negative reputation for the energy company. The purpose of this thesis is to develop a heuristic for reconfiguration of a distribution network, upon the occurrence of a failure in this network, making the switching only for feeders directly involved in this specific failed segment, considering that the switching applied is related exclusively to the isolation of failed sections and bars, as well as to supply electricity to the islands generated by the condition, with significant reduction in the number of applications of load flows, due to the use of sensitivity parameters for determining voltages and currents estimated on bars and lines of the feeders directly involved with that failed segment. A comparison between this process and classical methods is performed for different test networks from the literature about networks reconfiguration

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Ensuring the dependability requirements is essential for the industrial applications since faults may cause failures whose consequences result in economic losses, environmental damage or hurting people. Therefore, faced from the relevance of topic, this thesis proposes a methodology for the dependability evaluation of industrial wireless networks (WirelessHART, ISA100.11a, WIA-PA) on early design phase. However, the proposal can be easily adapted to maintenance and expansion stages of network. The proposal uses graph theory and fault tree formalism to create automatically an analytical model from a given wireless industrial network topology, where the dependability can be evaluated. The evaluation metrics supported are the reliability, availability, MTTF (mean time to failure), importance measures of devices, redundancy aspects and common cause failures. It must be emphasized that the proposal is independent of any tool to evaluate quantitatively the target metrics. However, due to validation issues it was used a tool widely accepted on academy for this purpose (SHARPE). In addition, an algorithm to generate the minimal cut sets, originally applied on graph theory, was adapted to fault tree formalism to guarantee the scalability of methodology in wireless industrial network environments (< 100 devices). Finally, the proposed methodology was validate from typical scenarios found in industrial environments, as star, line, cluster and mesh topologies. It was also evaluated scenarios with common cause failures and best practices to guide the design of an industrial wireless network. For guarantee scalability requirements, it was analyzed the performance of methodology in different scenarios where the results shown the applicability of proposal for networks typically found in industrial environments

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Technological evolution of industrial automation systems has been guided by the dillema between flexibilization and confiability on the integration between devices and control supervisory systems. However, there are few supervisory systems whose attributions can also comprehend the teaching of the communication process that happens behind this technological integration, where those which are available are little flexible about accessibility and reach of patterns. On this context, we present the first module of a didactic supervisory system, accessible through Web, applied on the teaching of the main fieldbus protocols. The application owns a module that automatically discovers the network topology being used and allows students and professionals of automation to obtain a more practical knowledgment by exchanging messages with a PLC, allowing those who are involved to know with more details the communication process of an automation supervisory system. By the fact of being available through Web, the system will allow a remote access to the PLC, comprehending a larger number of users. This first module is focused on the Modbus protocol (TCP and RTU/ASCII)

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This study shows the implementation and the embedding of an Artificial Neural Network (ANN) in hardware, or in a programmable device, as a field programmable gate array (FPGA). This work allowed the exploration of different implementations, described in VHDL, of multilayer perceptrons ANN. Due to the parallelism inherent to ANNs, there are disadvantages in software implementations due to the sequential nature of the Von Neumann architectures. As an alternative to this problem, there is a hardware implementation that allows to exploit all the parallelism implicit in this model. Currently, there is an increase in use of FPGAs as a platform to implement neural networks in hardware, exploiting the high processing power, low cost, ease of programming and ability to reconfigure the circuit, allowing the network to adapt to different applications. Given this context, the aim is to develop arrays of neural networks in hardware, a flexible architecture, in which it is possible to add or remove neurons, and mainly, modify the network topology, in order to enable a modular network of fixed-point arithmetic in a FPGA. Five synthesis of VHDL descriptions were produced: two for the neuron with one or two entrances, and three different architectures of ANN. The descriptions of the used architectures became very modular, easily allowing the increase or decrease of the number of neurons. As a result, some complete neural networks were implemented in FPGA, in fixed-point arithmetic, with a high-capacity parallel processing

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The use of Field Programmable Gate Array (FPGA) for development of digital control strategies for power electronics applications has aroused a growing interest of many researchers. This interest is due to the great advantages offered by FPGA, which include: lower design effort, high performance and highly flexible prototyping. This work proposes the development and implementation of an unified one-cycle controller for boost CFP rectifier based on FPGA. This controller can be applied to a total of twelve converters, six inverters and six rectifiers defined by four single phase VSI topologies and three voltage modulation types. The topologies considered in this work are: full-bridge, interleaved full-bridge, half-bridge and interleaved half-bridge. While modulations are classified in bipolar voltage modulation (BVM), unipolar voltage modulation (UVM) and clamped voltage modulation (CVM). The proposed project is developed and prototyped using tools Matlab/Simulink® together with the DSP Builder library provided by Altera®. The proposed controller was validated with simulation and experimental results

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Currently, there are several power converter topologies applied to wind power generation. The converters allow the use of wind turbines operating at variable speed, enabling better use of wind forces. The high performance of the converters is being increasingly demanded, mainly because of the increase in the power generation capacity by wind turbines, which gave rise to various converter topologies, such as parallel or multilevel converters. The use of converters allow effective control of the power injected into the grid, either partially, for the case using partial converter, or total control for the case of using full converter. The back-to-back converter is one of the most used topologies in the market today, due to its simple structure, with few components, contributing to robust and reliable performance. In this work, is presented the implementation of a wind cogeneration system using a permanent magnet synchronous generator (PMSG) associated with a back-to-back power converter is proposed, in order to inject active power in an electric power system. The control strategy of the active power delivered to the grid by cogeneration is based on the philosophy of indirect control

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This work proposes a formulation for optimization of 2D-structure layouts submitted to mechanic and thermal shipments and applied an h-adaptive filter process which conduced to computational low spend and high definition structural layouts. The main goal of the formulation is to minimize the structure mass submitted to an effective state of stress of von Mises, with stability and lateral restriction variants. A criterion of global measurement was used for intents a parametric condition of stress fields. To avoid singularity problems was considerate a release on the stress restriction. On the optimization was used a material approach where the homogenized constructive equation was function of the material relative density. The intermediary density effective properties were represented for a SIMP-type artificial model. The problem was simplified by use of the method of finite elements of Galerkin using triangles with linear Lagrangian basis. On the solution of the optimization problem, was applied the augmented Lagrangian Method, that consists on minimum problem sequence solution with box-type restrictions, resolved by a 2nd orderprojection method which uses the method of the quasi-Newton without memory, during the problem process solution. This process reduces computational expends showing be more effective and solid. The results materialize more refined layouts with accurate topologic and shape of structure definitions. On the other hand formulation of mass minimization with global stress criterion provides to modeling ready structural layouts, with violation of the criterion of homogeneous distributed stress

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In recent years there has been a significant growth in technologies that modify implant surfaces, reducing healing time and allowing their successful use in areas with low bone density. One of the most widely used techniques is plasma nitration, applied with excellent results in titanium and its alloys, with greater frequency in the manufacture of hip, ankle and shoulder implants. However, its use in dental implants is very limited due to high process temperatures (between 700 C o and 800 C o ), resulting in distortions in these geometrically complex and highly precise components. The aim of the present study is to assess osseointegration and mechanical strength of grade II nitrided titanium samples, through configuration of hollow cathode discharge. Moreover, new formulations are proposed to determine the optimum structural topology of the dental implant under study, in order to perfect its shape, make it efficient, competitive and with high definition. In the nitriding process, the samples were treated at a temperature of 450 C o and pressure of 150 Pa , during 1 hour of treatment. This condition was selected because it obtains the best wettability results in previous studies, where different pressure, temperature and time conditions were systematized. The samples were characterized by X-ray diffraction, scanning electron microscope, roughness, microhardness and wettability. Biomechanical fatigue tests were then conducted. Finally, a formulation using the three dimensional structural topology optimization method was proposed, in conjunction with an hadaptive refinement process. The results showed that plasma nitriding, using the hollow cathode discharge technique, caused changes in the surface texture of test specimens, increases surface roughness, wettability and microhardness when compared to the untreated sample. In the biomechanical fatigue test, the treated implant showed no flaws, after five million cycles, at a maximum fatigue load of 84.46 N. The results of the topological optimization process showed well-defined optimized layouts of the dental implant, with a clear distribution of material and a defined edge