Múltiplas antenas como alternativa para aumentar a taxa de extração de chaves secretas em redes veiculares com desvanecimento lento

The communication in vehicular ad hoc networks (VANETs) is commonly divided in two scenarios, namely vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I). Aiming at establishing secure communication against eavesdroppers, recent works have proposed the exchange of secret keys based on the variation in received signal strength (RSS). However, the performance of such scheme depends on the channel variation rate, being more appropriate for scenarios where the channel varies rapidly, as is usually the case with V2V communication. In the communication V2I, the channel commonly undergoes slow fading. In this work we propose the use of multiple antennas in order to artificially generate a fast fading channel so that the extraction of secret keys out of the RSS becomes feasible in a V2I scenario. Numerical analysis shows that the proposed model can outperform, in terms of secret bit extraction rate, a frequency hopping-based method proposed in the literature.

Aplicação foliar de molibdênio em adubos verdes e o desempenho do feijoeiro em sucessão

The knowledge of molybdenum application in legumes on the availability of N, by BNF, increased enzymatic activity and the residual effect caused on crops growth and yield can contribute to the greater scientific understanding involved in green manure processes. The aim of this study was to evaluate the Mo application and the N from Crotalaria juncea and Canavalia ensiformis green manures on common bean performance. Were conducted field experiments for the crops succession system (green manures - common bean) and laboratory essays for the enzymatic activities. Green manure production was installed in a factorial arrangement 2 x 4, with two green manure legumes species, sunnhemp (Crotalaria juncea) and jack beans (Canavalia ensiformis), and four Mo doses (0, 40, 80, 120 g ha-1) in the form of sodium molybdate (Na2MoO4), foliar applied, in a randomized block design with four replicates. For succession crop (common bean) additional treatment was added, beans grown without any fertilization, following the same experimental design from the previous crop. The dry matter decomposition and the N mineralization of green manure were monitored through collection of residues over time, by using the litter bags method. In laboratory were carried out tests of nitrate reductase activity in green manures and common beans at 90 and 66 days after sowing, respectively. The sunnhemp responded linearly positively to the application of Mo as the dry matter and N accumulation. While the jack beans presented a negative quadratic response for dry matter and there was no adjustment of regression models to N. The jack beans showed a higher decomposition rate and N mineralization compared to sunnhemp. The half lives for decomposing 50% of dry matter on the soil was 123 and 104 days to sunnhemp and jack beans, respectively, and 50% of N present in the residues was mineralized at 93 and 85 days. In common bean, differed from the control for number of pods the dose of 40 g ha-1 of Mo in both species of green manures and the dose 80 g ha-1 of Mo in jack beans. For number of grains only in sunnhemp on the dose of 40 g ha-1 of Mo differ from the control. The nitrate reductase activity was influenced by developmental stage of green manure species. In common bean, the activity of nitrate reductase was up to three times higher than the dose 0 g ha-1 of Mo compared to treatment with application of Mo in both species. There was no effect of Mo doses or species of green manure on common bean yield.

Proposta de avaliação de práticas sustentáveis nas operações de serviço em instituições de ensino superior da Rede Federal de Educação Profissional, Científica e Tecnológica

Higher Education Institutions (HEIs) have an extremely important social role, they are responsible for the place where they work and to form citizens who contribute to a fair and cooperative society. Universities can engage with sustainable development in planning, management, education, research, operations, community services, procurement of materials, transportation and infrastructure; this research seeks to analyze the sustainability practices in service operations in the Higher Education Institutions of the Federal Network of Professional, Scientific and Technological Education in Brazil through the development and application of a model called the Sustainability Assessment for Higher Technological Education (SAHTE). To achieve the proposed goal, a systematic survey of the scientific literature on sustainability assessment models in higher education institutions was conducted, making it possible to identify the characteristics and features of existing models. The model was applied through multiple case studies. The proposal compares the sustainability performance of service operations among individual institutions using a common methodology. It presents five areas to be evaluated in the HEI: Governance and Policies, People, Food, Water and Energy, and Waste and Environment, with a total of 134 questions. The need for greater support from the senior management of institutions to formulate and implement policies on sustainable development was identified when the lack of policies on sustainability in service operations was found; initiatives tend to be isolated. The participation of students and teachers in studies on the daily operations of the campus can be expanded and more widespread. The model seeks to evaluate sustainable practices in the service operations of the Brazilian Federal Network of Professional, Scientific and Technological Education; studies related to the evaluation of teaching sustainability are absent and the applicability of the model in private institutions and other countries is needed. The results obtained with the application of the SAHTE model are useful for the preparation and development of policies on sustainable development, especially in the service operations of the surveyed HEI. The results can sensitize staff and students, who can reflect on their roles in the HEI, as well as the community and suppliers.