[en] The transient exact solution of heat conduction in a two-domain composite cylinder is developed using the separation of variables technique. The inner cylinder is isotropic and the outer cylindrical layer is orthotropic. Temperature solutions are obtained for boundary conditions of the first and second kinds at the outer surface of the orthotropic layer. These solutions are applied to heat flow calorimeters modeling assuming that there is heat generation due to nuclear reactions in the inner cylinder. Heat flow calorimeter simulations are carried out assuming that the inner cylinder is filled with plutonium oxide powder. The first objective in these simulations is to predict the onset of thermal equilibrium of the calorimeter with its environment. Two types of boundary conditions at the outer surface of the orthotropic layer are used to predict thermal equilibrium. The procedure developed to carry out these simulations can be used as a guideline for the design of calorimeters. Another important application of these solutions is on the estimation of thermophysical properties of orthotropic cylinders. The thermal conductivities in the vertical, radial and circumferential directions of the orthotropic outer layer can be estimated using this exact solution and experimental data. Simultaneous estimation of the volumetric heat capacity and thermal conductivities is also possible. Furthermore, this solution has potential applications to the solution of the inverse heat conduction problem in this cylindrical geometry. An interesting feature of the construction of this solution is that two different sets of eigenfunctions need to be considered in the eigenfunction expansion. These eigenfunctions sets depend on the relative values of the thermal diffusivity of the inner cylinder and the thermal diffusivity in the vertical direction of the outer cylindrical layer

[en] We present electron spin resonance (ESR) data at 9.4 GHz in the phase separated Pr_0.65Ca_0.25Sr_0.10MnO₃ manganite. The coexistence of two resonance lines are observed below the short-range magnetic-order temperature (T_s∼255 K). One of the ESR line is a paramagnetic contribution retained from the high-temperature phase. The second contribution appears at T_s, which is associated with the presence of ferromagnetic regions. The two contributions can be seen near the charge-order transition, T_CO∼210 K. We study the temperature evolution of the resonance field and the linewidth of the ESR lines

[en] Knowledge of radioactivity levels in soils has a double interest: on the one hand, allows you to set the reference values ??(base Linne) from a region or geographic area, and secondly, to evaluate the external radiation dose received by the population and biota, through appropriate dosimetric model. The natural radioactivity, especially the radionuclides in the natural series. The aim of this study is to determine the levels of gamma emitting radionuclides in marine sediments of the Bay of Cadiz, and dose rates from external radiation received in the areas studied. (Author)

[en] With the aim of studying the stability range of the Zr₂Fe intermetallic when adding Nb, the range of existence of the cubic ternary phase (λ₁) and the corresponding two-phase field between them, four samples were analyzed, each one containing 35 at.% Fe and different at.% Nb: 0.5, 4 10 and 15. Optical and scanning electron metallographies, X-ray diffraction, microprobe analysis and Moessbauer spectroscopy were performed to determine and characterize the phases present in the samples. Results show that the Zr₂Fe compound accepts up to nearly 0.5 at.% Nb in solution, since the Zr₂Fe+λ₁ region is stable in the (0.5-3.5) at.% Nb range. To summarize these results an 800 deg. C section of the ternary Zr-Nb-Fe diagram, in the studied zone, was proposed

[en] The development of a procedure to calibrate the LEACHM and EU-Rotate_N models for simulating water and nitrogen dynamics in cauliflower crops. Calibration was performed using experimental data obtained from measurements in a cauliflower crop sited in Valencia (Spain) region. A procedure based on generalized sensitivity indices for time-dependent outputs was used to determine the most influencing model parameters, in order to reduce the number of parameters to be calibrated and to avoid overparameterization. The most influencing parameters were introduced in an optimization process that uses the experimental measurements of soil water and nitrate content to determine its optimal value and obtain calibrated models.After this analysis, the most important hydraulic parameters found were the coefficients of Campbell’s equation for the LEACHM model and the soil water content at field capacity and drainage coefficient for the EU-Rotate_N model. For the N cycle, the most influencing parameters were those related with the nitrification, humus mineralization rate and residue decomposition for both models. Both calibrated models provided good simulation of soil water content with an error between 5-7%. However, larger errors in soil-nitrate content simulation were found, mainly in the period corresponding to the crop residues incorporation. The prediction of the calibrated models in a different plot gave error values of about 7-9% for soil water content, but for soil nitrate content errors computed were 34% and 58%. After calibration, both models can be used to optimize the farmer water management and fertilization practices in horticultural crops, although in the N case further studies should be performed.

[en] This paper describes the use of passive adsorption/phase change subsystems for use in non-vibration cryocooling modes of operation in space applications. The specific focus here is the optimization and identification of working fluids and adsorbents for use in these systems. The research (Back et al., 1995) has demonstrated specific power densities capable of 1--6 W/kg of total weight for a 60 minute operation, exceeding conventional mechanical cryocooler systems (0.1--1 W/kg). For much shorter on-line passive cooling operations (e.g., 10 minutes) the cooling capacity will be in the range of 5--36 W/kg. Fluids and adsorbents suitable for the range of 30 K up to 200 K in space and biomedical applications are detailed in this paper, and implications for use in hybrid mechanical cryocoolers are discussed

[en] The hexagonal (C14-type) Laves phase Zr(Cr_0.40Fe_0.60)₂ when oxidized in an open furnace was studied by X-ray diffraction and Moessbauer spectroscopy techniques. Oxidation modified part of the original Laves phase and Zr oxides, Cr oxides, α-Cr, (Fe, Cr) oxides, α-Fe and α-Fe₂O₃ appeared. The behaviour of these phases, particularly the Fe-bearing phases, is described in detail through a two stage process (stage I from 0 to ∼7 wt% O₂ and stage II up to 22 wt% O₂). A very small amount of O₂ (stage I) is enough to induce the formation of α-Fe upon oxidation, sustaining a model previously suggested for the oxidation of the Laves phases. This α-Fe is highly Cr-substituted. Oxidation proceeds through the increasing presence of α-Fe₂O₃ and through the structural evolution of Zr oxides (formation of monoclinic, tetragonal and cubic ZrO₂)

[en] In a experimental plot of irrigated table grapes twelve neutron tubes were installed in each of two irrigated basins. Calibration of the neutron probe was done by the regression of the count ratio (R) on the volumetric water content (θ_v). To check the accuracy of the slope of the calibration equation a comparison of the soil water changes expected after known additions of water to soil by rainfall or irrigation with those changes measured with the neutron probe was made. This comparison showed that the neutron probe method on average overestimated the water change by about 22%. This overestimation is attributed to the type of regression used. An alternative method is proposed consisting in taking the mean value between the slope calculated from the regression of R on θ_v and then solving for θ_v, and that calculated from the regression of θ_v on R. It is suggested that measurement of the change in soil water content after a rainfall can be, under certain conditions, an easy way of testing the accuracy of the slope of the calibration equation

[en] In the present work, an X-ray diffraction (XRD) and thermal study of calcium undecanoate is presented. The measured high-resolution XRD powder pattern of the synthesized salt at room temperature, using synchrotron radiation, showed that the salt is a mixture of monohydrated and anhydrous calcium undecanoate. Calcium undecanoate monohydrate proved to have a monoclinic cell with a symmetry described by the P2 1/a space group. The structure dehydrates at about 100 deg. C. After dehydration, the salt undergoes a phase transformation which results in a thermotropic mesophase. Further heating of the salt leads to decomposition and melting. Ketones are the probable products of decomposition at 400 deg. C

[en] Precoated galvanized steel sheets were submitted to Prohesion test (PT) and to outdoor marine exposure test (OT). The corrosion products were different in both cases. Goethite, lepidocrocite, pyrite and magnetite were found in the Prohesion test samples; the presence of akaganeite cannot be discarded. Surprisingly greigite was detected in these samples, suggesting in addition a located microbiological corrosion process. On the other hand, goethite, lepidocrocite, magnetite, akaganeite and silicates were found in outdoor exposure samples. This study allows the conclusion that in the Prohesion G-85 test the corrosion mechanism is different from that in the marine atmosphere for the analyzed samples and could not be used to predict the performance of this type of outdoor exposed materials.