Consensus Acceleration in Multiagent Systems with the Chebyshev Semi-Iterative Method

We consider the fundamental problem of reaching consensus in multiagent systems; an operation required in many applications such as, among others, vehicle formation and coordination, shape formation in modular robotics, distributed target tracking, and environmental modeling. To date, the consensus problem (the problem where agents have to agree on their reported values) has been typically solved with iterative decentralized algorithms based on graph Laplacians. However, the convergence of these existing consensus algorithms is often too slow for many important multiagent applications, and thus they are increasingly being combined with acceleration methods. Unfortunately, state-of-the-art acceleration techniques require parameters that can be optimally selected only if complete information about the network topology is available, which is rarely the case in practice. We address this limitation by deriving two novel acceleration methods that can deliver good performance even if little information about the network is available. The first proposed algorithm is based on the Chebyshev semi-iterative method and is optimal in a well defined sense; it maximizes the worst-case convergence speed (in the mean sense) given that only rough bounds on the extremal eigenvalues of the network matrix are available. It can be applied to systems where agents use unreliable communication links, and its computational complexity is similar to those of simple Laplacian-based methods. This algorithm requires synchronization among agents, so we also propose an asynchronous version that approximates the output of the synchronous algorithm. Mathematical analysis and numerical simulations show that the convergence speed of the proposed acceleration methods decrease gracefully in scenarios where the sole use of Laplacian-based methods is known to be impractical

Improving Resource Efficiency with Partial Resource Muting for Future Wireless Networks

We propose novel resource allocation algorithms that have the objective of finding a good tradeoff between resource reuse and interference avoidance in wireless networks. To this end, we first study properties of functions that relate the resource budget available to network elements to the optimal utility and to the optimal resource efficiency obtained by solving max-min utility optimization problems. From the asymptotic behavior of these functions, we obtain a transition point that indicates whether a network is operating in an efficient noise-limited regime or in an inefficient interference-limited regime for a given resource budget. For networks operating in the inefficient regime, we propose a novel partial resource muting scheme to improve the efficiency of the resource utilization. The framework is very general. It can be applied not only to the downlink of 4G networks, but also to 5G networks equipped with flexible duplex mechanisms. Numerical results show significant performance gains of the proposed scheme compared to the solution to the max-min utility optimization problem with full frequency reuse.Comment: 8 pages, 9 figures, to appear in WiMob 201

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

Efeito da adubação nitrogenada e do pastejo sobre a frequência de espécies invasoras em ambientes de pastagem cultivada.

Altas doses de nitrogênio e manejo do pastejo mais intensivo tendem a diminuir a freqüência de espécies invasoras, pelo favorecimento do crescimento da espécie principal e efeito do pastejo sobre a presença de espécies invasoras de potencial forrageiro

Estudo da divergência genética em linhagens brasileiras de anaplasma marginale através da utilização do gene da proteína principal de superfície MSP1&#945.

Bovine anaplasmosis, caused by rickettsia Anaplasma marginale, represent one of the most important diseases ofruminants worldwide, causing significant economic losses in Brazil. This pathogen can be transmitted byRhipicephalus (Boophilus) microplus infected tick; by biting flies or by blood-contaminated fomites. The major surface proteins (msp) are involved in host-pathogen and tick-pathogen interactions and have been used as markers in A. marginale characterization and genetics studies In this study were characterized A. marginale strains obtained from naturally infected cattle from Rondônia, Acre and São Paulo State. The msp1 gene was amplified from A. marginale DNA extracted from erythrocytes by PCR in a 50 μl volume of PCR MasterMix (Promega, USA). Amplified fragments were purified and used directly for sequencing . The nucleotide and amino acid sequences of A. marginale msp1 were used for sequence alignment and genetics analysis. Multiple sequence alignment was performed using the Clustal X software. Nucleotides were coded as unordered, discrete characters with five possible character-states; A, C, G, T, or N, and gaps were coded as missing data. After a first proceeding and removal of the regions without genetic information, was carried the definitive alignment. Searches for the most parsimonious tree employed the branch and bound. The stability of the inferred topology was assessed via bootstrap analysis.. Through alignment analysis of the slighter variable region of msp1a gene, five rickettsia isolated types were identified in the A. marginale populations from São Paulo, Rondônia and Acre states. These results indicates that the strains of Acre state were less similar with São Paulo sample and not have divergence within strains obtained of samples provide

Morfogênese de capim-tanzânia (Panicum maximum cv. Tanzânia) em diferentes condições de manejo em pasto cultivado e irrigado.

Objetivou-se analisar o impacto da intensificação do uso do pasto, através de diferentes tipos de manejos, sobre características morfogênicas do Panicum maximum cv. Tanzânia

Características morfogênicas do capim Tanzânia (Panicum maximum cv. Tanzânia) submetido a diferentes graus de intensificação do manejo de pastagem no Nordeste brasileiro.

Este experimento foi conduzido para avaliar os efeitos de diferentes intensidades de manejo da pastagem sobre características morfogênicas de capim-tanzânia. Os tratamentos impostos ao pasto foram os manejos: intensivo (resíduo pós-pastejo de 30cm e adubação com 600 kg N/ha ano), moderado (resíduo pós-pastejo de 45cm, adubação 300 kg N/ha ano), leve (resíduo pós-pastejo 45cm sem adubação) e extensivo (resíduo pós-pastejo 30cm sem adubação). As características estudadas foram: filocrono, taxa de aparecimento de folhas, taxa de alongamento de folhas, taxa de alongamento de colmo e taxa de senescência. Todas as variáveis foram afetadas por tratamento. As taxas de aparecimento e alongamento de folhas e o alongamento de colmo foram maiores nos tratamentos que receberam adubação nitrogenada. Por outro lado a taxa de senescência foi mais alta no manejo extensivo. Provavelmente este efeito foi determinado pelo mais longo período de descanso (extensivo). Em geral a intensificação foi boa para a maioria das características morfogênicas, significando condição adequada para a produção de forragem