Academic literature on the topic 'Elementos não uniformes'

O termo Bioma refere-se a uma área do espaço geográfico representada por um tipo uniforme de ambiente, dentro do qual é possível identificar características similares de macroclima, fitofisionomia, solo e altitude (WALTER, 1986). Dentro dessas áreas espécies surgiram e se desenvolveram em resposta à essas características do ambiente. Tal processo permite que por exemplo, dentro dessas áreas os vegetais apresentem aspectos, formas e processos fisiológicos característicos (CRAWLEY, 1989). Dessa maneira, a manutenção desses biomas, com suas características ambientais únicas, é de fundamental importância para a manutenção da biodiversidade e dos serviços ecossistêmicos que ali ocorrem (regulação climática, ciclo de matéria, segurança alimentar, entre outros) (PBMC/BPBES, 2018; JOLY et al., 2019). O Brasil é formado por seis grandes biomas: Amazônia, Caatinga, Cerrado, Mata Atlântica, Pampas e Pantanal (IBGE, 2019). Dentro desses ambientes são encontrados uma grande diversidade de fauna e flora e características únicas de relevo e clima. Essa variedade de biomas está relacionada a grande extensão territorial do Brasil e a sua posição geográfica. Todas essas características fazem do Brasil o maior detentor de biota continental do mundo, sendo estimado um valor entre 15% e 20% das aproximadamente 1,5 milhões de espécies descritas no planeta. Só de plantas vasculares os números mais recentes citados são de 56108 espécies, com 12400 (22%) endêmicas. Esses dados representam aproximadamente 22% do total mundial (LEWINSOHN; PRADO, 2002; SHEPHERD, 2002; HUBBELL, 2008; GIAM et al., 2010). Dentro desse contexto, os biomas Cerrado e Pantanal se integram por meio dos rios que nascem nos planaltos do Cerrado. Esses rios contribuem na formação do Pantanal, nas planícies inundáveis da bacia do Paraguai (BRASIL, 2007). No Domínio Cerrado, a dinâmica ambiental é proveniente de uma marcada sazonalidade climática com duas estações bem definidas, o período seco e o período chuvoso (ASSAD, 1994; SILVA, 2011). Essa sazonalidade climática modifica constantemente as propriedades do solo, da flora e da paisagem e a reestruturação de muitas comunidades (AMARAL et al., 2013; MALHEIROS, 2016). No Pantanal as áreas conhecidas como planícies de inundação se caracterizam pela presença de hábitats que variam de aquáticos a terrestres, de acordo com o grau de comunicação com o rio principal (PAZ; TUCCI, 2010). Os ciclos de secas e cheias são um importante fenômeno hídrico para a região, criando um sistema complexo e dinâmico (JUNK; DA SILVA, 1999; RESENDE, 2008). O Cerrado é uma das 25 áreas do mundo consideradas críticas para a conservação, devido à riqueza biológica e à alta pressão antrópica a que vem sendo submetido (MYERS et al., 2000). O Pantanal, por sua vez, é reconhecido mundialmente pela abundância de sua fauna (MITTERMEIER et al., 1990; HARRIS et al., 2005) e é considerado Reserva da Biosfera e Patrimônio Natural da Humanidade pela Unesco (BRASIL, 2018). O conhecimento dos aspectos que envolvem a fauna, a flora e as características dessas paisagens são de extrema importância para a sua conservação e preservação. As áreas de transição entre esses dois biomas, chamadas áreas de ecótono, se fazem presentes no estado do Mato Grosso do Sul. Nessa região, os biomas Cerrado e Pantanal possuem correlações quanto aos aspectos geomorfológicos e fitogeográficos (RODRIGUES et al., 2017). Na região o encontro entre o Planalto de Maracaju-Campo Grande e a Planície Pantaneira é uma área comum de elementos bióticos e abióticos entre o planalto e a planície (FILHO et al., 2009). A transição entre dois ecossistemas implica a existência de uma área com valores intermediários para diversos parâmetros ambientais (NEIFF, 2003). Por um lado, a área de transição pode gerar um aumento na biodiversidade, dado o fato dessas áreas apresentarem representantes de fauna e flora dos dois ecossistemas (VELOSO et al., 1991). Contudo, essas áreas de transição podem também representarem barreira ou área de isolamento com ecossistemas vizinhos (MALANSON, 1997). Desta forma, uma análise voltada para as áreas de ecótono entre esses dois biomas faz-se necessária, uma vez que a preservação de um depende da preservação do outro. Sobretudo para o entendimento de que essas paisagens de ecótono podem ser responsáveis pelo isolamento e amortecimento das alterações dentro dos biomas Cerrado e Pantanal. Este E-book traz estudos desenvolvidos na área de ecótono Cerrado Pantanal no município de Aquidauana (MS) e entorno. O município está localizado a 130 Km a oeste da capital Campo Grande. Aquidauana por se tratar de um município com influência dos biomas Cerrado e Pantanal, abriga uma grande biodiversidade, sendo citada pelo Ministério do Meio Ambiente (BRASIL, 2002) como área prioritária para conservação da biodiversidade. Na mesma via, o município se destaca por sua vocação turística e agropecuária, o que demanda atenção, devido ao processo de intensa ocupação e exploração antrópica dos recursos naturais. Dessa maneira, o conhecimento de suas características ambientais e dos processos ecológicos desempenhados por sua fauna e flora contribuem para sua preservação e manutenção.

Entre la producción de los talleres epigráficos de Tarraco destaca la ingente serie de pedestales tripartitos exentos para las estatuas honoríficas de magistrados y sacerdotes provinciales. Se trata de un tipo de monumento tallado de manera uniforme y sistemática desde finales del siglo I hasta finales del II dC. El inicio de su producción coincidió con la reforma urbanística Flavia de la zona superior de la ciudad, que pasó a ser el área de representación del concilium Hispaniae citerioris (PHC). En ella se configuró también la imagen corporativa de la Tarraconense, una vez concedido el ius Latii, a través de la creación de una magnífica y uniforme galería con las estatuas de los flamines PHC a expensas del propio concilio. El texto inciso en sus pedestales perpetuaba la memoria de cada individuo y el honor de su flaminado, pero también mencionaban explícitamente su origo, que evocaba muchas comunidades repartidas por todo el territorio recientemente incorporadas de iure al estado romano. Muchas de ellas estaban muy alejadas de Tarraco y no necesariamente conocidas para la mayoría de la población, por lo que la exposición pública de los nombres de estas ciudades en los pedestales de conciudadanos ilustres contribuyó a aumentar el prestigio colectivo tan manifiestamente evocado en Tarraco en la mencionada galería de viri flaminales. Un elemento clave para la creación de esta imagen unificada fue el empleo del marmor local de gran calidad, la piedra de Santa Tecla, que pronto fue exportado e imitado para monumentos semejantes en otras ciudades de la Tarraconensis, lo que contribuyó a que este modelo de pedestal tripartito de Tarraco llegase a ser un símbolo de estatus para las élites locales, tal como demuestra su localización incluso en ciudades muy alejadas del inmediato entorno de la capital provincial, incluso en otros conventus.

Linear sparse antenna arrays have been widely studied in array processing literature. They belong to the general class of non-uniform linear arrays (NULAs). Sparse arrays need fewer sensor elements than uniform linear arrays (ULAs) to realize a given aperture. Alternately, for a given number of sensors, sparse arrays provide larger apertures and higher degrees of freedom than full arrays (ability to detect more source signals through direction-of-arrival (DOA) estimation). Another advantage of sparse arrays is that they are less affected by mutual coupling compared to ULAs. Different types of linear sparse arrays have been studied in the past. While minimum redundancy arrays (MRAs) and minimum hole arrays (MHAs) existed for more than five decades, other sparse arrays such as nested arrays, co-prime arrays and super-nested arrays have been introduced in the past decade. Subsequent to the introduction of co-prime and nested arrays in the past decade, many modifications, improvements and alternate sensor array configurations have been presented in the literature in the past five years (2015–2020). The use of sparse arrays in future communication systems is promising as they operate with little or no degradation in performance compared to ULAs. In this chapter, various linear sparse arrays have been compared with respect to parameters such as the aperture provided for a given number of sensors, ability to provide large hole-free co-arrays, higher degrees of freedom (DOFs), sharp angular resolutions and susceptibility to mutual coupling. The chapter concludes with a few recommendations and possible future research directions.

Oxygen is the most important element in common, rock-forming minerals. Earth’s crust and mantle contain about 44 wt. % oxygen, and even with its dense iron core, the bulk Earth is estimated to be approximately 30% oxygen. Considering the low mass and large size of the oxygen atom, the oxygen content is even higher if expressed in terms of vol. % or mol. %. For the above reason, a central problem of stable isotope geochemistry is to explain the distribution of oxygen isotope ratios in rocks. As shown in this chapter, much of the diversity in the abundance ratios is related to interactions of rocks with Earth’s extensive hydrosphere, which is nearly 89 wt. % oxygen. Even though hydrogen is only a minor element in rocks, some discussion of hydrogen isotopes is included here because they provide powerful complementary relationships to evaluate fluid-rock interactions. It has been suspected for centuries, and has now been proven by oxygen isotope data (see later), that Earth and the Moon have very similar origins. In particular, the δ18O values of large rock reservoirs on the Moon and Earth are practically identical. Diverse lunar lithologies have remarkably uniform values ranging only from +5.4 to +6.8 relative to SMOW, with the subset of lunar igneous rocks showing even less variation at +5.7 ± 0.2 (Epstein and Taylor, 1971; Taylor and Epstein, 1973). The same limited range of values is found for the largest lithologic reservoirs on Earth. For example, mid-ocean ridge (MOR) basalts are the most abundant igneous rock type on Earth, and cover practically the entire ocean floor. The δ18O values of these basalts are practically uniform at +5.7 ± 0.5 (Kyser, 1986). Similarly, other mafic lavas, as well as peridotites, pyroxenites, and practically all other mantle materials with the exception of the ophiolites and eclogites, have δ18O values in the restricted range of +5.0 to +8.0. Moreover, no apparent secular trend over geologic time has been found in the bulk δ18O values of these reservoirs. For these reasons, it is likely that the bulk δ18O values of Earth and the Moon are identical and very close to +5.7 ± 0.2.

This chapter discusses Thucydides' and Hobbes's ideas of human nature, which are often said to be very similar. International relations theorists are just as much prone to this mistake as others, referring to Thucydides, as they do to Hobbes, as a “realist.” Hobbes's view is close to the view of the famous “Athenian thesis” repeated throughout Thucydides' History of the Peloponnesian War. That thesis is similar in many ways to the realist thesis, claiming that human beings are universally selfish and always motivated by fear, honor, and interest. Since they are compelled by their passions, they are not to be blamed for their actions, and, as Thucydides' character Diodotus points out, they can be controlled only through superior power and brute force. However, the chapter argues that, in contradiction to the Athenian thesis, Thucydides' overall treatment of human nature proves that it is not so uniform and that passions do not force people to act. Individuals are responsible for their actions, capable of reason, and therefore guilty when they allow their passions to overcome their good sense. In Thucydides' view, political problems cannot be permanently solved, because there are elements in human nature that cannot be manipulated. While Thucydides depicts the bloodthirsty violence of civil war as well as genocidal international warfare as products of the extreme pressures of war, Hobbes sees them as events that take place whenever there is no power strong enough to prevent them.

Abstract This paper presents a methodology for generating conceptual designs of structural shapes and functional elements of machine systems from initial conditions having no preconceived information. Firstly, a feasible design region initially containing nothing is defined. The whole feasible region which is uniformly filled up with finite elements having an extremely low rigidity is here assumed to be a region containing nothing. Then, a seed element grows into a whole structural system in the feasible design region by conducting both the creation of external shapes and the growth of the inner structures. Next, the design method is advanced so that a functional element of a rotational joint is also generated with the structural shapes simultaneously. Finally, the proposed conceptual design method is applied to design of industrial robots.

A method is presented for the solution of Poisson’s Equations using a Lagrangian formulation. The interpolation functions are the Lagrangian operation of those used in the classical finite element method, which automatically satisfy boundary conditions exactly even though there are no nodes on the boundaries of the domain. The integration is introduced in an implicit way by using approximated step functions. Classical surface integration terms used in the weak form are unnecessary due to the interpolation function in the Lagrangian formulation. Furthermore, the Lagrangian formulation simplified the connection between the mesh and the solid structures, thus providing a very easy way to solve the problems without a conforming mesh.

An array of nine square heated elements mounted in a square three-by-three pattern with no gap between the elements on a large vertical adiabatic surface with natural convective flow over the elements has been considered. Each of the elements has a uniform heat flux over its surface, the heat fluxes over eight of the elements being the same and the heat flux over the ninth element being higher than that over the other eight elements. The basic aim of the study was to determine the effect the position of the higher heat flux element on the mean temperatures of the other eight elements. The situation considered is an approximate model of situations that can arise in electronic cooling. The flow has been assumed to be steady and laminar and it has been assumed that the fluid properties are constant except for the density change with temperature which gives rise to the buoyancy forces, this having been treated by using the Boussinesq approach. The solution has been obtained by numerically solving the full three-dimensional form of the governing equations, these equations being written in terms of dimensionless variables using the commercial cfd code FLUENT. The solution has the heat flux Rayleigh number, the Prandtl number, the ratio of the heat flux over the high heat flux element to the heat flux over the other eight elements, and the position of the high heat flux element as parameters. Because of the application that motivated this work results have only been obtained for Pr = 0.7. Results have been obtained for a wide range of values of the other input parameters and the effect of these parameter values on the mean surface temperatures of each of the elements has been studied.

Structured background mesh with regular shaped uniform elements is easy to generate automatically. Analysis using such a mesh is possible with an independent CAD model representing the geometry by using Implicit Boundary Method. This avoids mesh generation difficulties and enables new types of elements that use B-spline approximations instead of the traditional Lagrange interpolations. But the background mesh should ideally have higher resolution in areas where the solution has large gradients. In this paper, T-spline basis functions are used to locally refine a structured mesh. T-splines allow construction of elements with T-junctions maintaining the continuity of the field variable across element boundaries and hence ensure that compatibility conditions are satisfied. T-spline elements are constructed for linear and cubic basis. Essential boundary conditions are applied using implicit boundary method, which allows boundary conditions to be imposed even when there are no nodes on the boundary. T-spline elements are shown to represent constant and linear solution exactly. The mesh refinement technique is evaluated using two dimensional elasticity problem involving stress concentration.

Abstract The objective of this study was to develop new solutions for linear elastic buckling coefficients of rectangular flat plates with support conditions not previously found in the literature. Critical buckling coefficients were found for rectangular flat plates subjected to uniform compression on two opposite edges with one partially supported unloaded edge using the finite element method. Plates with different aspect ratios and with varying support length on the unloaded edges were analyzed. Currently, no solutions are available in the literature for plates subjected to uniform compression and with partially supported unloaded edges. The method developed in this work was verified on problems where closed form mathematical solutions exist. An engineer will be able to use the solutions developed in this work in the design of components that are susceptible to instability failures. Another benefit of this work is to demonstrate to practicing engineers that reliable instability results can be obtained by using standard finite element analysis (FEA) methods. This work considers a small subset of instability problems but the FEA method utilized herein can be effectively used to model a large class of practical instability problems.

Abstract In this paper, the propulsive performance of a caudal peduncle-fin swimmer mimicking a bio-inspired robotic fish model is numerically studied using a fully coupled FSI solver. The model consists of a rigid peduncle and a flexible fin which pitches in a uniform flow. The flexible fin is modeled as a thin plate assigned with non-uniformly distributed stiffness. A finite volume method based in-house Navier-Stokes solver is used to solve the fluid equations while the fin deformation is resolved using a finite element code. The effect of the fin flexibility on the propulsive performance is investigated. The numerical results indicate that the compliance has a significant influence on the performance. Under the parameters studied in this paper, the medium flexible fin exhibits remarkable efficiency improvement as well as thrust augment, while the least flexible fin shows no obvious difference from the rigid one. However, for the most flexible fin, although the thrust production decreases sharply, the efficiency reaches the maximum value. It should be noted that by non-uniformly distributing the rigidity across the caudal fin, our model is able to replicate some fin deformation patterns observed in both the live fish and the experimental robotic fish.

Using the finite element method, the paper presents an explicit expression for the reference stress of tube/pipe bends with various degrees of ovality that are subjected to uniform internal pressures. No such task has been accomplished before. The presented reference stress may be used in conjunction with the uniaxial creep rupture data to obtain the creep life of the bend.

Structured grids with regular shaped uniform elements are easy to generate automatically and have been used in extended finite element approaches to avoid mesh generation difficulties. But the grid or mesh should ideally have higher resolution in areas where the solution has large gradients. In this paper a technique for refinement of structured grids is presented that allows refinement of the grid without violating compatibility requirements by using solution structures constructed using approximate step functions. Essential boundary conditions are applied using implicit boundary method, which allows boundary conditions to be imposed even when there are no nodes on the boundary. This grid refinement technique is evaluated using two dimensional elasticity problems that involve stress concentration.

A utilização do concreto autoadensável reforçado com fibras permite um grande avanço nas propriedades do concreto convencional. As fibras são adicionadas à mistura com a finalidade de melhorar suas propriedades mecânicas no estado endurecido, aliadas às características de alta trabalhabilidade e sem segregação, quando no estado fresco. Este compósito apresenta uma dispersão mais uniforme das fibras dentro dos elementos estruturais, graças à eliminação de compactação e vibrações, visto que as vibrações tendem a causar a segregação das fibras. Assim, podem ser executados elementos estruturais de espessuras reduzidas com alta qualidade, majorando sua resistência à tração na flexão e suavizando a curva de tensão-deformação, quando comparados ao concreto sem incorporação de fibras. Ainda, pode aumentar a segurança com a prevenção de fissuras e o aumento da tenacidade do concreto. Os tipos de fibras comumente utilizadas são de origem metálica, constituídas de aço carbono e sintéticas, com variações de polímeros inorgânicos. Elas exercem diferente influência no comportamento do material. De modo a verificar a influência da utilização da adição de fibras nas propriedades do material, foi dosado um traço de concreto autoadensável, com fibras de aço de três fatores de forma, nas porcentagens de 0,25%, 0,5% e 1,0% em relação ao volume total do material. Após a avaliação dos resultados foi possível afirmar que a mistura testada com melhores resultados possui uma taxa de 1,0% da fibra com maior fator de forma. Apresentou perda de apenas 9,1% na resistência à compressão, aumento de 261% da resistência à tração na flexão e mais de 31 vezes o acréscimo do valor de fator de tenacidade em relação à mistura referência. Este estudo mostra que o concreto autoadensável com a incorporação de fibras metálicas tem aplicabilidade em situações onde é necessária elevada resistência a esforços de tração e elevada tenacidade, podendo ser utilizado em elementos onde se busca uma redução de armadura de tração e aumento da vida útil, contribuindo para a segurança e qualidade.DOI: http://dx.doi.org/10.4995/HAC2018.2018.5369

The California State Rail Plan (CSRP) is among the best rail plan documents published by any jurisdiction in the United States to date. As such, the CSRP is used in this paper as the basis of comparison to other state rail service plans. These plans will have been submitted to the Federal Railroad Administration (FRA) on record as of June 2020—as required under Section 303 of the Passenger Rail Investment and Improvement Act (PRIIA) of 2008. The purpose of this paper is to identify the best practices and gaps that may inform California and other states in their future rail service plan development. This paper is grounded in the realization that, while the general outline of FRA requirements is uniform for all states, the actual content and inclusion of these requirements in the myriad state plans varies greatly. For example, California was granted an exception to help update FRA Rail Plan Guidance for its 2018 Rail Plan, other states have complained that FRA guidance and requirements on rail service planning have put state rail agencies in the position of constantly writing plans with little or no time to implement them. Throughout this research, the authors identify all the elements of FRA guidelines as reflected in the CSRP and rail plans of other states. This report also identifies the best features and planning strategies that may inform and improve the state rail planning process going forward, steps that will positively contribute to the public benefit of enhanced rail systems.