Equalização para Sistemas OFDM Óptico

Na ´ultima d´ecada a t´ecnica OFDM (Orthogonal Frequency Division Multiplex ) tem ganhado cada vez mais espa¸co nas comunica¸coes com e sem fio. A ´area das comunica¸coes ´opticas tamb´em se desenvolveu bastante nos ´ultimos anos. Recentemente iniciou-se a jun¸cao destes dois recursos: a t´ecnica OFDM e o canal ´optico. Dentro deste panorama, este trabalho se propoe a estudar a conjuga¸cao destes dois recursos e propor um sistema ´optico simples, onde a compensa¸cao de dispersao e o alocamento de banda ficam sob a resposabilidade da OFDM aplicando a t´ecnica de equaliza¸cao de canal utilizando tons piloto. A esta t´ecnica ´e dado o nome de OOFDM (Optical OFDM). Neste trabalho foi considerado um sistema ´optico de fibra monomodo padrao com modula¸cao de intensidade e detec¸cao direta (IM-DD - Intensity Modulation - Direct Detection), visando deixar a parte ´optica simples. Na transmissao OFDM foi utilizada a simetria hermitiana, para a transmissao em banda base, mapeamento 16-QAM e a aloca¸cao variada atrav´es do bit loading. Para corrigir a dispersao do canal foi implementada uma estima¸cao e equaliza¸cao de canal atrav´es de tons piloto e interpola¸cao linear. O sistema foi simulado e os resultados mostraram a possibilidade de uma transmissao em 20 km de fibra com taxa de 47 Gbps com BER ≈ 10−5 e EVM ≈ −22 dB. Os resultados possibilitam a atua¸cao desta t´ecnica em redes metropolitanas e como solu¸cao para enlaces de ´ultima milha em altas taxas de bits

Faculty versus Student Repeatability on Evaluating Translucency of the Anterior Dentition

The objective was to compare the repeatability between dental faculty, whose clinical practice was primarily restorative dentistry, and final year dental students in categorizing the inherent translucency of images selected at random using either a 3- or 7-point scale (translucent to opaque). Digital images of anterior dentition were randomly selected based on inherent translucency. Thirty images (five were repeated) were randomized and categorized by 20 dental students and 20 faculty on their inherent translucency. Statistical analysis was performed using an F test for analysis of variance at 95% confidence interval. A covariance parameter estimate (CPE) was accomplished to compare the inter-rater variability of the dental faculty and dental students. Statistically, more variability occurred between Slides (CPE of 0.185 (p = 0.001)) and between Subject and Slide (CPE of 0.122 (p = 0.0002)) than within subjects (CPE of 0.021 (p = 0.083)). Viewing repeat Slides, Students (CPE = 0.16) were more consistent (p \u3c 0.05) than faculty (CPE = 1.8) using the 3- point scale, while the CPE was the same (CPE = 0.669) using 7-point scale. Dental students and faculty were consistent using the 7-point scale to judge repeat slides, while dental students in this limited pilot study were more consistent when viewing a repeat slide using the 3-point scale

Selecting new Brachiaria humidicola hybrids for Western Brazilian Amazon.

Brachiaria humidicola is a perennial and stoloniferous forage grass, with excellent adaptation to infertile soils and waterlogging. Producers in northern Brazil have become interested in this species, especially after the degradation of large areas of lowly permeable soils sown with B. brizantha cv. Marandu, which is highly intoler-ant of soil waterlogging (Andrade and Valentim 2006). However, since only 3 cultivars of B. humidicola are registered in Brazil (Mapa 2013), there is a need to de-velop new cultivars adapted to the range of environ-mental conditions experienced. Recently, Embrapa Beef Cattle obtained intraspecific hybrids of B. humidicola that need to be evaluated agronomically, aiming at sub-sequent grazing trials and future releases. The objective of this study was to evaluate and select apomictic and sexual hybrids of B. humidicola under the environmental conditions of the state of Acre, in western Brazilian Amazon.Publicado também nos Anais do 22º INTERNATIONAL GRASSLAND CONGRESS, Sidney, 2013

Selecting New \u3cem\u3eBrachiaria humidicola\u3c/em\u3e Hybrids for Western Brazilian Amazon

Brachiaria humidicola is a perennial and stoloniferous forage grass, with excellent adaptation to infertile soils and waterlogging. Producers in northern Brazil have become interested in this species, especially after the degradation of large areas of lowly permeable soils sown with B. brizantha cv. Marandu, which is highly intolerant of soil waterlogging (Andrade and Valentim 2006). However, since only 3 cultivars of B. humidicola are registered in Brazil (Mapa 2013), there is a need to develop new cultivars adapted to the range of environmental conditions experienced. Recently, Embrapa Beef Cattle obtained intraspecific hybrids of B. humidicola that need to be evaluated agronomically, aiming at subsequent grazing trials and future releases. The objective of this study was to evaluate and select apomictic and sexual hybrids of B. humidicola in the environmental conditions of the state of Acre, in western Brazilian Amazon

Dynamical large deviations for a boundary driven stochastic lattice gas model with many conserved quantities

We prove the dynamical large deviations for a particle system in which particles may have different velocities. We assume that we have two infinite reservoirs of particles at the boundary: this is the so-called boundary driven process. The dynamics we considered consists of a weakly asymmetric simple exclusion process with collision among particles having different velocities

Ecosystem services from converted land: the importance of tree cover in Amazonian pastures.

Deforestation is responsible for a substantial fraction of global carbon emissions and changes in surface energy budgets that affect climate. Deforestation losses include wildlife and human habitat, and myriad forest products on which rural and urban societies depend for food, fiber, fuel, fresh water, medicine, and recreation. Ecosystem services gained in the transition from forests to pasture and croplands, however, are often ignored in assessments of the impact of land cover change. The role of converted lands in tropical areas in terms of carbon uptake and storage is largely unknown. Pastures represent the fastest-growing form of converted land use in the tropics, even in some areas of rapid urban expansion. Tree biomass stored in these areas spans a broad range, depending on tree cover. Trees in pasture increase carbon storage, provide shade for cattle, and increase productivity of forage material. As a result, increasing fractional tree cover can provide benefits land managers as well as important ecosystem services such as reducing conversion pressure on forests adjacent to pastures. This study presents an estimation of fractional tree cover in pasture in a dynamic region on the verge of large-scale land use change. An appropriate sampling interval is established for similar studies, one that balances the need for independent samples of sufficient number to characterize a pasture in terms of fractional tree cover. This information represents a useful policy tool for government organizations and NGOs interested in encouraging ecosystem services on converted lands. Using high spatial resolution Rio Branco, Brazil. A semivariogram and devolving spatial resolution are employed to determine the coarsest sampling interval that may be used, minimizing effects of spatial autocorrelation. The coarsest sampling interval that minimizes spatial dependence was about 22 m. The area-weighted fractional tree cover for the study area was 1.85 %, corrected for a slight bias associated with the coarser sampling resolution. The pastures sampled for fractional tree cover were divided between ?high? and ?low? tree cover, which may be the result of intentional incorporation of arboreal species in pasture. Further research involving those ranchers that have a higher fractional tree cover may indicate ways to promote the practice on a broader scale in the region

Seleção de amendoim forrageiro para cultivo em Mato Grosso do Sul.

Entre as leguminosas forrageiras utilizadas no consórcio com gramíneas, o amendoim forrageiro (Arachis spp.) destaca-se pela adaptação em pastagens formadas em solos de baixa permeabilidade, elevada persistência, resistência ao pastejo, uma vez que seus estolões apresentam-se fortemente enraizados, e por apresentar reservas de sementes enterradas. Por seu desempenho ser pouco conhecido nas regiões de Cerrado, objetivou-se avaliar e selecionar acessos dessa leguminosa visando o seu uso em pastagens cultivadas em Mato Grosso do Sul

Nutrient status of cattle grazing systems in the western brazilian Amazon.

Low-input cultivated pastures to feed cattle have dominated land use after forest clearing for decades in the western Brazilian Amazon. This study was undertaken to help understand the inherent nutrient supply dynamics underwriting cattle performance on three farms in the state of Acre. We assessed soil chemical and physical properties associated over time with different land uses following forest clearing. This information permitted specifying a conceptual model of nutrient stocks and flows under the observed grazing system, which produced insights about the dynamics of soil nutrient degradation. Above ground forage mass, topsoil nutrient concentrations and soil bulk density were measured. Land covers were Brachiaria spp. grasses, a grass-Pueraria phaseoloides mix, cropland and forest. Most soil nutrient parameters initially decreased after clearing, gradually recovering over time with grass-only pastures; however, 20 yr-old pastures had 20% less forage mass. Most pasture system nutrients on these farms resided in topsoil and roots, where large stocks of mature forage supported soil fertility with recycled nutrients from litter. Estimates of partial topsoil nutrient balances were negative. This suggested that corresponding nutrient stocks and the accumulation of forage mass were probably maintained primarily through the sum of inflows from cattle excreta, the subsoil, soil organic matter, and litter mineralization with scant input of commercial fertilizer. Therefore, herd management to increase animal system productivity via higher stocking rates on vegetatively younger forage requires monitoring of nutrient stocks and flows and fertilization that assures replenishment of the nutrients extracted. Otherwise, rapid depletion of soil nutrient stocks will lead to system degradation and failure