The role of asymptotic functions in network optimization and feasibility studies

Solutions to network optimization problems have greatly benefited from developments in nonlinear analysis, and, in particular, from developments in convex optimization. A key concept that has made convex and nonconvex analysis an important tool in science and engineering is the notion of asymptotic function, which is often hidden in many influential studies on nonlinear analysis and related fields. Therefore, we can also expect that asymptotic functions are deeply connected to many results in the wireless domain, even though they are rarely mentioned in the wireless literature. In this study, we show connections of this type. By doing so, we explain many properties of centralized and distributed solutions to wireless resource allocation problems within a unified framework, and we also generalize and unify existing approaches to feasibility analysis of network designs. In particular, we show sufficient and necessary conditions for mappings widely used in wireless communication problems (more precisely, the class of standard interference mappings) to have a fixed point. Furthermore, we derive fundamental bounds on the utility and the energy efficiency that can be achieved by solving a large family of max-min utility optimization problems in wireless networks.Comment: GlobalSIP 2017 (to appear

Electrostatics of electron-hole interactions in van der Waals heterostructures

The role of dielectric screening of electron-hole interaction in van der Waals heterostructures is theoretically investigated. A comparison between models available in the literature for describing these interactions is made and the limitations of these approaches are discussed. A simple numerical solution of Poissons equation for a stack of dielectric slabs based on a transfer matrix method is developed, enabling the calculation of the electron-hole interaction potential at very low computational cost and with reasonable accuracy. Using different potential models, direct and indirect exciton binding energies in these systems are calculated within Wannier-Mott theory, and a comparison of theoretical results with recent experiments on excitons in two-dimensional materials is discussed.Comment: 10 pages, 8 figure

All-strain based valley filter in graphene nanoribbons using snake states

A pseudo-magnetic field kink can be realized along a graphene nanoribbon using strain engineering. Electron transport along this kink is governed by snake states that are characterized by a single propagation direction. Those pseudo-magnetic fields point towards opposite directions in the K and K' valleys, leading to valley polarized snake states. In a graphene nanoribbon with armchair edges this effect results in a valley filter that is based only on strain engineering. We discuss how to maximize this valley filtering by adjusting the parameters that define the stress distribution along the graphene ribbon.Comment: 8 pages, 6 figure

Logarithmic periodicities in the bifurcations of type-I intermittent chaos

The critical relations for statistical properties on saddle-node bifurcations are shown to display undulating fine structure, in addition to their known smooth dependence on the control parameter. A piecewise linear map with the type-I intermittency is studied and a log-periodic dependence is numerically obtained for the average time between laminar events, the Lyapunov exponent and attractor moments. The origin of the oscillations is built in the natural probabilistic measure of the map and can be traced back to the existence of logarithmically distributed discrete values of the control parameter giving Markov partition. Reinjection and noise effect dependences are discussed and indications are given on how the oscillations are potentially applicable to complement predictions made with the usual critical exponents, taken from data in critical phenomena.Comment: 4 pages, 6 figures, accepted for publication in PRL (2004

Matemática, Literatura & Aulas

A aprendizagem da Matemática não ocorre por mera transmissão de saberes do professor para os alunos. A ideia de que o conhecimento pode passar linearmente de uma cabeça – daquele que sabe – para outra(s) cabeça(s) – para aqueles que querem saber –, pelas palavras ditas e escritas, não tem qualquer correspondência com a realidade. A aprendizagem é um processo adaptativo, simultaneamente individual e coletivo, baseado na ação e na reflexão, no qual a comunicação tem um papel fundamental, na medida que permite estabelecer ligação entre as pessoas

Prevalência de anticorpos anti-Toxoplasma gondii em caprinos.

Resumo: A Toxoplasmose pode ser congênita ou adquirida e representa uma das infecções parasitárias mais comuns em caprinos, de qualquer faixa etária, raça e/ou sexo. Estudos epidemiológicos realizados no Brasil e no mundo apontam que a prevalência de anticorpos anti-Toxoplasma gondii varia entre 10% a 86%, independente do sistema de produção adotado. Objetivou-se com este estudo avaliar a prevalência de anticorpos anti-Toxoplasma gondii em caprinos de oito propriedades rurais de Quixadá, Ceará. Foram realizadas coletas de sangue por venipunção da jugular de 93 cabritos, machos e fêmeas, com mais de quatro meses de idade; 54 matrizes e três reprodutores. Os sangues foram centrifugados a 3000xg por 10 minutos para obtenção do soro. Estes foram armazenados em tubos tipo eppendorf® e congelados a -20°C até o momento da realização do teste ELISA indireto, usando como antígeno taquizoítos de T. gondii. A pesquisa foi aprovada pela Comissão de Ética no Uso de Animais da FCAV-UNESP, sob o protocolo 014465/12. As análises estatísticas foram realizadas no programa EPI Info 7.0.9.7 utilizando-se o teste Qui-quadrado. A prevalência de anticorpos anti-T. gondii encontrada: nas oito propriedades foi de 23,33% (35/150) e para as diferentes categorias animais de 15,05% (14/93) para crias; 37,04% (20/54) para matrizes e 33,33% (1/3) para os reprodutores, quando essas foram comparadas houve diferença estatística entre crias x matrizes (P = 0,0006) e crias x reprodutores (P = 0,004). Com relação ao sexo a prevalência encontrada para fêmeas foi de 25,21% (30/119) e para machos de 16,13% (5/31), não foi observada diferença estatística (P = 0,16). O sistema de produção adotado na maioria das propriedades era misto, ou seja, produzia-se carne e leite. Em todas as propriedades estudadas foi encontrado pelo menos um animal soropositivo para T. gondii, demonstrando que formas infectantes do protozoário estão presentes na região estudada. [Prevalence of Toxoplasma gondii antibodies in goats]. Congenital or acquired toxoplasmosis is one of the most common parasitic infections in goats of any age, race and sex. Epidemiological studies carried out in Brazil and around the world show that the prevalence of Toxoplasma gondii antibodies ranges from 10% to 86%, regardless of the adopted production system. The objective of this study was to evaluate the prevalence of antibodies to Toxoplasma gondii in goats from eight farms in Quixadá, Ceará. Blood samples were collected by jugular venipuncture of 93 male and female little goats, older than four months; 54 does and three bucks (breeders). The blood samples were centrifuged at 3000xg for 10 minutes to separate the serum. Serum samples were stored in Eppendorf ® tubes and frozen at -20°C for further testing by the indirect ELISA using as antigen tachyzoites of T. gondii. The study was approved by the Ethics Committee on Animal Use of FCAV - UNESP, under protocol 014465/12. Statistical analyses were performed by the Epi Info 7.0.9.7 software using the Chi-square test. The prevalence of T. gondii antibody for the eight properties studied was as follows: 23.33% (35/150) while within the animal categories, they were 15.05% (14/93) for offspring; 37.04% (20/54) for does; 33% (1/3) for bucks. The statistical analysis showed significant differences between offspring x does (P=0.0006) and offspring x bucks (P=0.004). With respect to gender, the prevalence for does was 25.21% (30/119) while for bucks, it was 16.13% (5/31), but they were not statistically different (P=0.16). The production system adopted in the majority of properties was mixed, that is, they produced meat and milk. All the properties had at least one animal positive for T. gondii, demonstrating that infectious forms of the parasite are present in the studied region.Edição dos Resumos do I Simpósio Internacional de Medicina Veterinária Preventiva (SIMPREV), Jaboticabal, 2013