ABSTRACT. Time metrics are extremely important to evaluate the transmission performance on Wireless Mesh Networks (WMNs), whose main characteristic is to use multihop technology to extend the network coverage area. One of such metrics is WCETT (Weighted Cumulative Expected Transmission Time), in which transmission times per hop are weighted for both proactive and reactive conditions. Furthermore, such metrics are able to detect delays that can degrade some network services. This paper presents an optimization model to minimize WCETT in a WMN, subject to constraints grouped by bandwidth, flow control and power control. As the model includes nonlinear constraints, we propose a heuristic to solve it, which divides the problem in two subproblems. The first subproblem maximizes the network link capacity and a Simulated Annealing algorithm is used to solve it. Considering the link capacities obtained, the second subproblem minimizes the WCETTs, which is formulated as a linear programming model. Some numerical results are presented, based on instances of WMNs randomly generated. Some of these results are compared with the results obtained by a commercial simulator in order to verify the coherence of the proposed heuristic for realistic scenarios.
<p>With the dissemination of the additive manufacturing by deposition of molten material, popularly known as 3D printing, studies on the mechanical properties of the pieces manufactured through this process are necessary to increase the understanding of their behaviors, as well as to know how to expand the application horizons of the technology in the manufacture of items that will<br />work under mechanical stresses. Therefore, the aim of this article is to analyze the influence of two printing parameters (number of perimeters and filling density) on the mechanical properties of specimens manufactured in PLA from 3D printing. For the study, the specimens made of PLA filament with a diameter of 1.75 mm, using the FDM technique and a 3D Cloner DH Plus model machine, were submitted to tensile test. From the analyzes carried out, it was possible to verify that the number of perimeters is more relevant with regard to the mechanical resistance to traction. The results were satisfactory and allow to trace interesting parallels with the data obtained in other studies used as references in present work.</p><p><br /><strong>Key words</strong>: PLA; 3D printing; number of perimeters; filling density; mechanical properties.</p><p>==================================================================</p><p>Com a disseminação da manufatura aditiva por deposição de material fundido, popularmente conhecida como impressão 3D, fazem-se necessários estudos a respeito das propriedades mecânicas das peças fabricadas por este processo a fim de aumentar a compreensão do comportamento destes objetos e expandir os horizontes de aplicação da tecnologia na fabricação de itens que irão trabalhar sob solicitações mecânicas. Portanto, o objetivo deste artigo é analisar a influência de dois parâmetros de impressão (número de perímetros e densidade de preenchimento) sobre as propriedades mecânicas de corpos de prova fabricados em PLA a partir da impressão 3D. Para o estudo, os corpos de prova foram confeccionados a partir do filamento de PLA com diâmetro de 1,75 mm, por meio da técnica FDM, utilizando uma máquina 3D Cloner, modelo DH Plus, e submetidos ao ensaio de tração. A partir das análises efetuadas, foi possível constatar que o parâmetro “número de perímetros” é mais relevante no que tange a resistência mecânica à tração. Os resultados foram satisfatórios e permitem traçar paralelos interessantes com dados obtidos em outros estudos utilizados como referência na elaboração deste artigo.</p><p><br /><strong>Palavras-chave</strong>: PLA; impressão 3D; número de perímetros; densidade de preenchimento; propriedades mecânicas</p>
Abstract:The use of QoS parameters to evaluate the quality of service in a mesh network is essential mainly when providing multimedia services. This paper proposes an algorithm for planning wireless mesh networks in order to satisfy some QoS parameters, given a set of test points (TPs) and potential access points (APs). Examples of QoS parameters include: probability of packet loss and mean delay in responding to a request. The proposed algorithm uses a Mathematical Programming model to determine an adequate topology for the network and Monte Carlo simulation to verify whether the QoS parameters are being satisfied. The results obtained show that the proposed algorithm is able to find satisfactory solutions.
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