A Time-Periodic Lyapunov Approach for Motion Planning of Controllable Driftless Systems on SU(n)

For a right-invariant and controllable driftless system on SU(n), we consider a time-periodic reference trajectory along which the linearized control system generates su(n): such trajectories always exist and constitute the basic ingredient of Coron's Return Method. The open-loop controls that we propose, which rely on a left-invariant tracking error dynamics and on a fidelity-like Lyapunov function, are determined from a finite number of left-translations of the tracking error and they assure global asymptotic convergence towards the periodic reference trajectory. The role of these translations is to avoid being trapped in the critical region of this Lyapunov-like function. The convergence proof relies on a periodic version of LaSalle's invariance principle and the control values are determined by numerical integration of the dynamics of the system. Simulations illustrate the obtained controls for $n=4$ and the generation of the C--NOT quantum gate.Comment: Submitte

Design optimization of high-performance electrodynamic actuators for use in a cryogenically cooled telescope

An analysis and optimization of a mirror-actuator system for large excursion/high-frequency chopping is developed. The results of this analysis, combined with laboratory measurements of a prototype actuator operating at cryogenic temperatures, allow performance predictions to be made for a real system utilizing this technology

Preparo do solo e rotação de culturas para o feijoeiro irrigado.

Os objetivos deste trabalho foram avaliar os efeitos de diferentes sistemas de preparo do solo e de rotação de culturas sobre o rendimento do feijoeiro irrigado, no período de inverno.bitstream/item/59064/1/Foco-50.pd

Public policies and food security and family farming networks: contributions to the construction of effectiveness indicators.

This work presents a methodology for investigating the performance of public politics regarding food security networks formed in Brazilian municipalities aimed at increasing income and employment in familiar farming. These programs need to further develop the methodologies used for studying their efficiency so that they can reach a new stage in the improvement and use of management tools thereby achieving beteer results of social inclusion and/or food security. This paper constitutes a first effort to bring together indicators for the evaluation of the efficiency of public politicies

Qualidade da água em reservatórios prediais. Contributos para o PSA da Póvoa de Varzim

A exploração de sistemas de abastecimento de água para consumo humano é uma atividade de grande complexidade pela necessidade de se garantir uma melhoria contínua de eficácia e eficiência no serviço prestado aos consumidores. De acordo com a Organização Mundial da Saúde, a forma mais eficaz de garantir uma água segura pode concretizar-se através da implementação de planos de segurança da água que contemplam a descrição detalhada do sistema de abastecimento, a identificação de perigos, a avaliação do risco e o estabelecimento de medidas necessárias para os controlar, abarcando todas as etapas do sistema, desde a bacia de captação até à torneira do consumidor. Uma das grandes dificuldades na aplicação deste conceito situa-se nas redes prediais urbanas, uma vez que a propriedade privada limita a responsabilidade das entidades gestoras dos sistemas públicos em assegurar uma responsabilidade direta sobre a qualidade da água nestas redes. O presente trabalho de investigação teve como objetivo avaliar a qualidade da água em reservatórios prediais e em torneiras de consumidores na cidade da Póvoa de Varzim, constituindo-se um contributo para a implantação de um plano de segurança da água nesta cidade portuguesa

Estimations for the Single Diffractive production of the Higgs boson at the Tevatron and the LHC

The single diffractive production of the standard model Higgs boson is computed using the diffractive factorization formalism, taking into account a parametrization for the Pomeron structure function provided by the H1 Collaboration. We compute the cross sections at next-to-leading order accuracy for the gluon fusion process, which includes QCD and electroweak corrections. The gap survival probability ($$) is also introduced to account for the rescattering corrections due to spectator particles present in the interaction, and to this end we compare two different models for the survival factor. The diffractive ratios are predicted for proton-proton collisions at the Tevatron and the LHC for the Higgs boson mass of $M_H$ = 120 GeV. Therefore, our results provide updated estimations for the diffractive ratios of the single diffractive production of the Higgs boson in the Tevatron and LHC kinematical regimes.Comment: 20 pages, 6 figures, 3 table

Radiolysis of ammonia-containing ices by energetic, heavy and highly charged ions inside dense astrophysical environments

Deeply inside dense molecular clouds and protostellar disks, the interstellar ices are protected from stellar energetic UV photons. However, X-rays and energetic cosmic rays can penetrate inside these regions triggering chemical reactions, molecular dissociation and evaporation processes. We present experimental studies on the interaction of heavy, highly charged and energetic ions (46 MeV Ni^13+) with ammonia-containing ices in an attempt to simulate the physical chemistry induced by heavy ion cosmic rays inside dense astrophysical environments. The measurements were performed inside a high vacuum chamber coupled to the heavy ion accelerator GANIL (Grand Accelerateur National d'Ions Lourds) in Caen, France.\textit{In-situ} analysis is performed by a Fourier transform infrared spectrometer (FTIR) at different fluences. The averaged values for the dissociation cross section of water, ammonia and carbon monoxide due to heavy cosmic ray ion analogs are ~2x10^{-13}, 1.4x10^{-13} and 1.9x10^{-13} cm$^2$, respectively. In the presence of a typical heavy cosmic ray field, the estimated half life for the studied species is 2-3x10^6 years. The ice compaction (micropore collapse) due to heavy cosmic rays seems to be at least 3 orders of magnitude higher than the one promoted by (0.8 MeV) protons . In the case of the irradiated H2O:NH3:CO ice, the infrared spectrum at room temperature reveals five bands that were tentatively assigned to vibration modes of the zwitterionic glycine (+NH3CH2COO-).Comment: Accepted to be published in Astronomy and Astrophysics; Number of pages: 12; Number of Figures: 7; Number of Tables:

A história da ciência em periódicos brasileiros de química : saberes para formação docente

Apresenta os resultados de pesquisa que teve como objeto de estudo os artigos sobre história da ciência publicados nos periódicos Química Nova e Química Nova na Escola, entre 1978 e 2004, nos quais se buscou destacar os saberes sobre a natureza do conhecimento científico, e que possam contribuir no aprimoramento das concepções docentes sobre a ciência. Mapeamos os artigos, montamos banco de dados, fizemos a leitura e análise do material. A leitura revelou um conjunto de saberes sobre a natureza do conhecimento científico que podem contribuir na formação de professores de ciência, já que apresentam uma imagem da ciência mais próxima da realidade e de seu desenvolvimento, abordando-a em seus múltiplos aspectos