Characterization of solar-grade silicon produced by the SiF4-Na process

A process was developed for producing low cost solar grade silicon by the reaction between SiF4 gas and sodium metal. The results of the characterization of the silicon are presented. These results include impurity levels, electronic properties of the silicon after crystal growth, and the performance of solar photovoltaic cells fabricated from wafers of the single crystals. The efficiency of the solar cells fabricated from semiconductor silicon and SiF4-Na silicon was the same

Algumas considerações sobre o estudo estatístico de medições de dose em grãos de argamassas por luminescência estimulada opticamente

Fundação das Universidades PortuguesasMinisterio de Ciencia e Innovación (Espanha)Fundação para a Ciência e a Tecnologia (FCT)Ação Integrada E-141”(Fundação das Universidades Portuguesas)/“Acción Integrada PT2009-0077” (Ministerio de Ciencia e Innovación)/PEst-OE/CTE/UI0697/201

Microscopy studies in support of dating of mortars of historical buildings

Fundação das Universidades PortuguesasMinisterio de Ciencia e InnovaciónFundação para a Ciência e a Tecnologia (FCT

Multibody-Based Input and State Observers Using Adaptive Extended Kalman Filter

[Abstract] The aim of this work is to explore the suitability of adaptive methods for state estimators based on multibody dynamics, which present severe non-linearities. The performance of a Kalman filter relies on the knowledge of the noise covariance matrices, which are difficult to obtain. This challenge can be overcome by the use of adaptive techniques. Based on an error-extended Kalman filter with force estimation (errorEKF-FE), the adaptive method known as maximum likelihood is adjusted to fulfill the multibody requirements. This new filter is called adaptive error-extended Kalman filter (AerrorEKF-FE). In order to present a general approach, the method is tested on two different mechanisms in a simulation environment. In addition, different sensor configurations are also studied. Results show that, in spite of the maneuver conditions and initial statistics, the AerrorEKF-FE provides estimations with accuracy and robustness. The AerrorEKF-FE proves that adaptive techniques can be applied to multibody-based state estimators, increasing, therefore, their fields of applicationThis research was partially financed by the Spanish Ministry of Science, Innovation and Universities and EU-EFRD funds under the project “Técnicas de co-simulación en tiempo real para bancos de ensayo en automoción” (TRA2017-86488-R), and by the Galician Government under grant ED431C2019/29Xunta de Galicia; ED431C2019/2

Kalman filters based on multibody models: linking simulation and real world. A comprehensive review

[Abstract] The Kalman filter algorithm estimates variables of linear systems combining information from real sensors and a mathematical model of the system. It may be applied to observe nonlinear systems by means of a linearization of the system model. Multibody system dynamics constitutes a methodology for the analysis and design of mechanical systems. During the last twenty years, many ways of employing a multibody model as the Kalman filter model have been explored. This paper gathers up diverse algorithms, from the first ones based on the continuous expressions of the filter, to the indirect methods that enable real-time implementations of the observation of mechanical systems with a large number of variables. A detailed explanation of the methods and a description of the strengths and weaknesses of each one is presented along this paper, including a benchmark evaluating the performance of the methods. An important aspect of the Kalman filter is the characterization of the system uncertainty by means of white Gaussian noise. Sometimes, the statistical properties of the noise are unknown. Several methods to determine these properties are described, and a new methodology to model systems perturbed by colored noise (time-correlated noise) is presented. In Kalman filters based on multibody models, the information from a real mechanical system can be employed to keep the model behaving like the actual system with a great level of accuracy, linking the simulation to the real behavior of the system

Three-Body Dynamics and Self-Powering of an Electrodynamic Tether in a Plasmasphere

The dynamics of an electrodynamic tether in a three-body gravitational environment are investigated. In the classical two-body scenario the extraction of power is at the expense of orbital kinetic energy. As a result of power extraction, an electrodynamic tether satellite system loses altitude and deorbits. This concept has been proposed and well investigated in the past, for example for orbital debris mitigation and spent stages reentry. On the other hand, in the three-body scenario an electrodynamic tether can be placed in an equilibrium position fixed with respect to the two primary bodies without deorbiting, and at the same time generate power for onboard use. The appearance of new equilibrium positions in the perturbed three-body problem allow this to happen as the electrical power is extracted at the expenses of the plasma corotating with the primary body. Fundamental differences between the classical twobody dynamics and the new phenomena appearing in the circular restricted three-body problem perturbed by the electrodynamic force of the electrodynamic tether are shown in the paper. An interesting application of an electrodynamic tether placed in the Jupiter plasma torus is then considered, in which the electrodynamic tether generates useful electrical power of about 1 kW with a 20-km-long electrodynamic tether from the environmental plasma without losing orbital energy

Asymptotic Solution for the Current Profile of Passive Bare Electrodynamic Tethers

A relatively high-accuracy analytical solution for the current and potential profile along a passive bare electrodynamic tether is provided using perturbation theory. An ad hoc nondimensional formulation of the governing local bias and orbital motion limited current collection equations allows one to approach the problem with a perturbation technique in which a parameter, epsilon, quantifies the influence of ohmic effects on the final solution. For the case of small ohmic effects an approximate solution is obtained with a third-order expansion. Conversely, the case of dominant ohmic effects is treated based on an extension of the exact analytical solution available for the particular case of zero load and negligible potential drop at the cathodic end of the tether. After computing the analytical current and potential profile the maximum and average current, the Lorentz force and torque, as well as the optimum load impedance for maximum power generation are obtained. When compared with the exact, numerically-computed solution an accuracy of better than5%is achieved for the computation of the average current across the full parameter space. The error with respect to the generated power becomes negligible when the load impedance is set to the optimum value, while it can grow to a maximum of about 30% for the less relevant case in which the load impedance of the power generation system is badly mismatched. The results, which are valid for a general rectilinear passive electrodynamic tether with constant cross section satisfying orbital motion limited theory and irrespective of the particular orbit configuration, will be of aid in the design and analysis of space missions involving bare electrodynamic tethers

Magnetic Ground State of Pr0.89_{0.89}LaCe0.11_{0.11}CuO4+α−δ_{4+\alpha-\delta} with Varied Oxygen Depletion Probed by Muon Spin Relaxation

The magnetic ground state of an electron-doped cuprate superconductor Pr$_{1-x}$LaCe$_x$CuO$_{4+\alpha-\delta}$ ($x=0.11, \alpha\simeq0.04$) has been studied by means of muon spin rotation/relaxation (\msr) over a wide variety of oxygen depletion, $0.03\le\delta\le0.12$. Appearance of weak random magnetism over entire crystal volume has been revealed by a slow exponential relaxation. The absence of $\delta$-dependence for the random magnetism and the multiplet pattern of muon Knight shift at higher fields strongly suggest that the random moments are associated with excited Pr$^{3+}$ ions under crystal electric field.Comment: 6 pages, 4 figures, submitted to J. Phys. Soc. Jp

Relationship among growth curve, nutrient consumption and genetic transformation efficiency of 'Albariño' (Vitis vinifera) cell suspensions

Embryogenic cell suspensions of grapevine (Vitis sp.) have been proposed as the best target to approach genetic transformation challenges. However, optimal phase and growth period of cell suspensions for successful gene transfer have not been investigated. Here, a step by step protocol to initiate and establish cell suspensions of 'Albariño' (V. vinifera) in only 4 weeks is presented. Growth kinetics, cell viability and nutrient consumption (phosphates and nitrates) as well as the number of transient transgenic events (using the uidA reporter gene) were studied in 'Albariño' cell suspensions grown for an 18-days period. Based on biomass growth, the exponential phase of cell suspensions was reached between days 3 to 6. Nutrient uptake results point to the exhaustion of phosphate in the culture medium at day 6. Moreover, the highest number of transgenic events after biolistic bombardment was obtained from cell suspensions grown for 6 days (4032 ± 695 blue spots), compared to 12 and 18 days of continuous culture. Plant regeneration percentage varied depending on the age of the culture and the selected embryo type. In conclusion, this paper shows for the first time the relationship between growth curve and nutrient consumption of embryogenic cell suspension with efficiency in genetic transformation and plant regeneration of grapevine