Static and cinematic tests of GPS receivers

Os sistemas de navegação global por satélites, em especial o GPS, mais completo e conhecido, tem multiplicado suas aplicações no meio agrícola. O desempenho de receptores, no entanto, não é devidamente conhecido entre os usuários; assim, este trabalho visou avaliar receptores com distintas configurações e o uso de correções diferenciais por meio de ensaios estáticos e cinemáticos; no primeiro caso foram avaliados, concomitantemente, oito receptores ativando ou não as correções diferenciais WAAS e EGNOS, além de sinais privados específicos para alguns desses receptores; também se testaram intensidades de filtragem disponíveis em alguns dos receptores. No ensaio cinemático utilizaram-se dois receptores de navegação fixados sobre a cabine de um trator, tendo como referência um receptor GPS RTK. Na primeira avaliação os resultados mostraram que as correções WAAS e EGNOS não adicionam qualidade ao posicionamento na região de Piracicaba, SP. As correções diferencias privadas via satélite demonstraram ser mais acuradas que os demais sistemas avaliados. O ensaio sob condição cinemática, com GPS RTK de referência, permitiu o cálculo de erros no sentido perpendicular ao percurso, indicando ser de fácil execução.The global navigation satellite systems, especially the GPS, well known and totally implemented, have been intensively used in agriculture. The performance of receivers, however, is not properly disseminated among the users, so the aim of this work is to evaluate receivers with distinct configurations and the use of differential corrections through static and cinematic tests. In the first case eight receivers were tested activating or not the differential corrections WAAS and EGNOS, besides specific augmentation signals for some of the receivers and filtering intensities available for some of the receivers. In the cinematic condition two navigation receivers were mounted on the top of a tractor cab and tested using a GPS RTK receiver as reference. In the first evaluation the results showed that WAAS and EGNOS corrections do not add quality to the positioning in the Piracicaba, SP region. The private differential corrections by satellite were more accurate than the other systems tested. The test under cinematic condition, using a GPS RTK receiver as reference allowed the easy computation of the errors in the perpendicular of travel direction

Studies about soil electrical conductivity measurements

A condutividade elétrica é a capacidade que um material possui em conduzir corrente elétrica, e uma das suas utilidades na agricultura provém do fato de que a massa do solo com sua variabilidade na composição físico-química apresenta diferentes níveis de condutividade elétrica (CE). O objetivo do presente trabalho foi estudar o comportamento da CE no solo e avançar no entendimento dos fatores que regem seus níveis de variação e desenvolver sistemas que permitam a mensuração contínua da CE do solo para a geração de mapas. Construiu-se um sistema com várias configurações de mensuração da CE e, nas avaliações em campo, os resultados foram parcialmente satisfatórios. Num estudo detalhado utilizando apenas um sistema comercial para sua mensuração, obteve-se a indicação clara de que a CE responde às variações na textura do solo e em seus teores de umidade, o que demonstra o potencial que ela tem como ferramenta para facilitar e baratear o processo de obtenção de dados para a caracterização física dos solos.The electric conductivity is the capacity of a material in driving electric current and one of its usefulness in the agriculture comes from the fact that the soil electrical conductivity (EC) varies with its intrinsic physicochemical variability. The objective of this work was to study the EC behavior and advance on the factors understanding that affects its variability, and develops systems for measuring and mapping EC. We built a system with several measurement configurations, and on the field tests the results were partially satisfactory. In a detailed study using only a commercial EC measuring equipment the results clearly indicated that EC relates with soil texture and moisture, and may represent an important and low price tool for collecting data and characterizing soil physical properties.CNPqFAPES

RFQ-cooler for low-energy radioactive ions at ISOLDE

A radio frequency ion cooler and buncher project at the CERN-ISOLDE facility is presented. Monte Carlo simulations, based on the ion mobility concept will be discussed. Future options for the facility are outlined

Un couplage Boussinesq - équation intégrale appliquée à l'interaction de la houle avec des obstacles bidimensionnels

6ppNational audienceOn présente ici une méthode de couplage entre les équations de Boussinesq "étendues", suivant la formulation potentielle de Jamois, et la méthode d'équation intégrale. La mise en œuvre est réalisée dans le cas d'un bassin à houle bidimensionnel. Des validations sont présentées

Zaoyang chondrite cooling history from pyroxene Fe(2+)-Mg intracrystalline ordering and exolutions

The Zaoyang ordinary chondrite fell as a single 14.15-kg mass in Hubey province (China) in October 1984 and was classified as a non-brecciated H5 chondrite, shock facies b. Cooling rate in pyroxenes can be calculated down to about 1000 C by using fine textures and at still lower temperatures (700 to 200 C) by intracrystalline ordering processes. The crystal chemistry of clinopyroxene and orthopyroxene from the matrix of the H5 Zaoyang chondrite has been investigated by X-ray structure refinement and detailed microprobe analysis. By comparison with terrestrial pyroxenes cell and polyhedral volumes in clino- and orthopyroxenes show a low crystallization pressure. Fe(2+) and Mg are rather disordered in M1 and M2 sites of clino- and orthopyroxenes; the closure temperatures of the exchange reaction are 600 and 512 C respectively, which is consistent with a quite fast cooling rate, estimated of the order of one degree per day. The closure temperature for the intercrystalline Ca-Mg exchange reaction for clino- and orthopyroxene showing clinopyroxene lamellae about 10 microns thick. Kinetic evaluations based on the thickness of exolved lamellae give a cooling rate of not more than a few degrees per 10(exp 4) years. The different cooling rates obtained from Fe(2+)-Mg intracrystalline partitioning and exolution lamellae suggest an initial episode of slow cooling at 900 C, followed by faster cooling at temperatures of 600-500 C at low pressure conditions. The most probable scenario of the meteorite history seems that the exolved orthopyroxene entered the parental chondrite body after exolution had taken place at high temperature. Subsequent fast cooling occurred at low temperature after the formation of the body

Structural determinants of multimerization and dissociation in 2-Cys peroxiredoxin chaperone function

Peroxiredoxins (PRDXs) are abundant peroxidases present in all kingdoms of life. Recently, they have been shown to also carry out additional roles as molecular chaperones. To address this emerging supplementary function, this review focuses on structural studies of 2-Cys PRDX systems exhibiting chaperone activity. We provide a detailed understanding of the current knowledge of structural determinants underlying the chaperone function of PRDXs. Specifically, we describe the mechanisms which may modulate their quaternary structure to facilitate interactions with client proteins and how they are coordinated with the functions of other molecular chaperones. Following an overview of PRDX molecular architecture, we outline structural details of the presently best-characterized peroxiredoxins exhibiting chaperone function and highlight common denominators. Finally, we discuss the remarkable structural similarities between 2-Cys PRDXs, small HSPs, and J-domain-independent Hsp40 holdases in terms of their functions and dynamic equilibria between low- and high-molecular-weight oligomers

Scattering of scalar perturbations with cosmological constant in low-energy and high-energy regimes

We study the absorption and scattering of massless scalar waves propagating in spherically symmetric spacetimes with dynamical cosmological constant both in low-energy and high-energy zones. In the former low-energy regime, we solve analytically the Regge-Wheeler wave equation and obtain an analytic absorption probability expression which varies with $M\sqrt{\Lambda}$, where $M$ is the central mass and $\Lambda$ is cosmological constant. The low-energy absorption probability, which is in the range of $[0, 0.986701]$, increases monotonically with increase in $\Lambda$. In the latter high-energy regime, the scalar particles adopt their geometric optics limit value. The trajectory equation with effective potential emerges and the analytic high-energy greybody factor, which is relevant with the area of classically accessible regime, also increases monotonically with increase in $\Lambda$, as long $\Lambda$ is less than or of the order of $10^4$. In this high-energy case, the null cosmological constant result reduces to the Schwarzschild value $27\pi r_g^2/4$.Comment: 12 pages, 6 figure

Time variable cosmological constant of holographic origin with interaction in Brans-Dicke theory

Time variable cosmological constant (TVCC) of holographic origin with interaction in Brans-Dicke theory is discussed in this paper. We investigate some characters for this model, and show the evolutions of deceleration parameter and equation of state (EOS) for dark energy. It is shown that in this scenario an accelerating universe can be obtained and the evolution of EOS for dark energy can cross over the boundary of phantom divide. In addition, a geometrical diagnostic method, jerk parameter is applied to this model to distinguish it with cosmological constant.Comment: 10 pages, 9 figure

Quantum Statistical Entropy and Minimal Length of 5D Ricci-flat Black String with Generalized Uncertainty Principle

In this paper, we study the quantum statistical entropy in a 5D Ricci-flat black string solution, which contains a 4D Schwarzschild-de Sitter black hole on the brane, by using the improved thin-layer method with the generalized uncertainty principle. The entropy is the linear sum of the areas of the event horizon and the cosmological horizon without any cut-off and any constraint on the bulk's configuration rather than the usual uncertainty principle. The system's density of state and free energy are convergent in the neighborhood of horizon. The small-mass approximation is determined by the asymptotic behavior of metric function near horizons. Meanwhile, we obtain the minimal length of the position $\Delta x$ which is restrained by the surface gravities and the thickness of layer near horizons.Comment: 11pages and this work is dedicated to the memory of Professor Hongya Li