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

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

Efficient Computation of Multiple Density-Based Clustering Hierarchies

HDBSCAN*, a state-of-the-art density-based hierarchical clustering method, produces a hierarchical organization of clusters in a dataset w.r.t. a parameter mpts. While the performance of HDBSCAN* is robust w.r.t. mpts in the sense that a small change in mpts typically leads to only a small or no change in the clustering structure, choosing a "good" mpts value can be challenging: depending on the data distribution, a high or low value for mpts may be more appropriate, and certain data clusters may reveal themselves at different values of mpts. To explore results for a range of mpts values, however, one has to run HDBSCAN* for each value in the range independently, which is computationally inefficient. In this paper, we propose an efficient approach to compute all HDBSCAN* hierarchies for a range of mpts values by replacing the graph used by HDBSCAN* with a much smaller graph that is guaranteed to contain the required information. An extensive experimental evaluation shows that with our approach one can obtain over one hundred hierarchies for the computational cost equivalent to running HDBSCAN* about 2 times.Comment: A short version of this paper appears at IEEE ICDM 2017. Corrected typos. Revised abstrac

Melhoramento da população de milho CMS 14.

A ausencia de sistemas de produção tecnificados, a não utilizacao de insumos modernos e, principalmente a não disponibilidade de sementes melhoradas, são fatores que concorrem de maneira decisiva para as baixas produtividades de milho no Amapá. As cultivares tradicionalmente plantadas como Pretinha e Palha Roxa não apresentaram rendimentos satisfatorios. Com o objetivo de se obter uma nova variedade de milho, a partir da população CMS 14 (Pool 25), a mais produtiva que a original, realizou-se nesta população o primeiro ciclo de seleção massal estratificada. Os trabalhos foram conduzidos no município de Mazagão, em solo Gley Pouco Humico hidromorfico.bitstream/item/65042/1/AP-1985-melhoramento-populacao-milho.pd

Characterization of Vehicle Behavior with Information Theory

This work proposes the use of Information Theory for the characterization of vehicles behavior through their velocities. Three public data sets were used: i.Mobile Century data set collected on Highway I-880, near Union City, California; ii.Borl\"ange GPS data set collected in the Swedish city of Borl\"ange; and iii.Beijing taxicabs data set collected in Beijing, China, where each vehicle speed is stored as a time series. The Bandt-Pompe methodology combined with the Complexity-Entropy plane were used to identify different regimes and behaviors. The global velocity is compatible with a correlated noise with f^{-k} Power Spectrum with k >= 0. With this we identify traffic behaviors as, for instance, random velocities (k aprox. 0) when there is congestion, and more correlated velocities (k aprox. 3) in the presence of free traffic flow

GPS-based CERN-LNGS time link for Borexino

We describe the design, the equipment, and the calibration of a new GPS based time link between CERN and the Borexino experiment at the Gran Sasso Laboratory in Italy. This system has been installed and operated in Borexino since March 2012, and used for a precise measurement of CNGS muon neutrinos speed in May 2012. The result of the measurement will be reported in a different letter.Comment: 13 pages, 11 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

Produção e distribuição sazonal de litter em áreas de caatinga sob diferentes manejos.

Resumo: O litter compreende restos vegetais e animais. Sua presença confere proteção ao solo evitando o efeito negativo das enxurradas, mantendo a temperatura e estrutura do solo. Este trabalho objetivou quantificar a produção e distribuição de litter em áreas de caatinga raleada e não manipulada. Três áreas foram utilizadas: raleada para fins pastoris, raleada para fins apícolas e não manipulada. A produção foi obtida a partir do lançamento de molduras e 1,0x0,25m em diferentes épocas do ano de 2012. O litter foi fracionado manualmente em seus componentes e determinados suas proporções da massa total. A área não manipulada apresentou maior produção de litter, 5.714,35 Kg/ha enquanto a área de Caatinga raleada para fins apícolas a menor produção, 3.921,21 Kg/ha. A miscelânea foi a fração do litter que apresentou maior representatividade chegando a responder por 50% de toda a produção. A produção de litter de uma área nativa pode ser semelhante a uma área raleada. A produção tem relação direta com a precipitação. Esta mostrou sazonalidade na produção total, contrariando suas frações que mantiveram-se equilibrados durante todo o ano. [Seasonal production and distribution of litter in different areas under caatinga managements]. Abstract: The litter includes plant and animal remains. Its presence confers protection to the ground avoiding the negative effect of floods, keeping the temperature and soil structure. This study aimed to quantify the production and distribution of litter in areas of thinned caatinga and not manipulated. Three areas were used for grazing purposes thinned, thinned for apiculture and not manipulated. The production was obtained from the launch of frames and 1.0 x0, 25m at different times of the year 2012. The litter was manually fractionated into its components, and certain proportions of their total mass. The area had not manipulated greater production of litter, 5714.35 kg / ha while the area of Caatinga thinned for apiculture lower production, 3921.21 kg / ha. The smorgasbord was the fraction of the litter with the highest representation coming to account for 50% of all production. The production of litter from an area native can be similar to a thinned area. The production is directly related to precipitation. The total production of litter showed seasonality, contradicting its fractions which remained balanced throughout the year

Uso do orçamento forrageiro em abordagem participativa para produção de caprinos no bioma caatinga.

Resumo: O uso do orçamento forrageiro (OF) com enfoque participativo visa envolver agricultores no processo de construção de técnicas que possam ser facilmente utilizadas para o manejo sustentável dos recursos naturais. O objetivo deste trabalho foi testar OF como instrumento para planejamento do rebanho caprino. A experiência foi conduzida em área individual de 11ha, em assentamento no sertão do Apodi (RN). A área foi composta por cultivo de algodão agroecológico, sistema agrossilvipastoril e pasto nativo. O rebanho foi de vinte animais. OF foi realizado em três etapas: levantamento da produção de massa seca total de forragem disponível, avaliação do efetivo animal e planejamento. As informações do levantamento determinaram o tempo máximo de uso da área para manter as metas de ganho de peso para cabritos e manutenção de peso dos adultos. As práticas agroecológicas aumentaram a oferta de forragem. Houve manutenção do peso das cabras e ganhos de peso nas novilhas. Os cabritos ganharam peso de forma linear. O monitoramento permitiu confirmar que a ferramenta do orçamento forrageiro foi efetiva em auxiliar no planejamento zootécnico do rebanho no semiárido. [Forage budget on participatory approach to goat production in caatinga biome]. Abstract: Forage budget (FB) using participatory approach had been used to include smallholders in technology generation process and improving transfer technology for others. This research was carried out to test FB as a tool to make a planning for goat production system in Brazilian semi arid land. In an individual settlement area about 11 ha was implemented it. There were agroecological cotton system, agrossilvipastoral and native vegetation there. There were 20 animal in the area. FB was implemented in three phases: quantification of forage biomass total and available, herd evaluation and planning. It was determinate a maximum time to keep animal in the land using information from planning that preview as goal keep weight in goats and gain weight in kids. Ecological practices improved amount of forage. There was possible keep weight in goats. Young goats had gained weight. All kids gained weight during experimental period. Monitoring zootechnical aspects were effective to ensure forage budget like a good tool to help smallholders in sustainable planning use natural resources