Creep-rupture reliability analysis

A probabilistic approach to the correlation and extrapolation of creep-rupture data is presented. Time temperature parameters (TTP) are used to correlate the data, and an analytical expression for the master curve is developed. The expression provides a simple model for the statistical distribution of strength and fits neatly into a probabilistic design format. The analysis focuses on the Larson-Miller and on the Manson-Haferd parameters, but it can be applied to any of the TTP's. A method is developed for evaluating material dependent constants for TTP's. It is shown that optimized constants can provide a significant improvement in the correlation of the data, thereby reducing modelling error. Attempts were made to quantify the performance of the proposed method in predicting long term behavior. Uncertainty in predicting long term behavior from short term tests was derived for several sets of data. Examples are presented which illustrate the theory and demonstrate the application of state of the art reliability methods to the design of components under creep

Gravitational radiation from pulsar glitches

The nonaxisymmetric Ekman flow excited inside a neutron star following a rotational glitch is calculated analytically including stratification and compressibility. For the largest glitches, the gravitational wave strain produced by the hydrodynamic mass quadrupole moment approaches the sensitivity range of advanced long-baseline interferometers. It is shown that the viscosity, compressibility, and orientation of the star can be inferred in principle from the width and amplitude ratios of the Fourier peaks (at the spin frequency and its first harmonic) observed in the gravitational wave spectrum in the plus and cross polarizations. These transport coefficients constrain the equation of state of bulk nuclear matter, because they depend sensitively on the degree of superfluidity.Comment: 28 page

Study of the stress intensity factors in the bulk of the material with synchrotron diffraction

Artículo de Proceedings de Congreso Internacional Fatigue2017In this work we present the results of a hybrid experimental and analytical approach for estimating the stress intensity factor. It uses the elastic strains within the bulk obtained by synchrotron X-ray diffraction data. The stress intensity factor is calculated using a multi-point overdeterministic method where the number of experimental data points is higher than the number of unknowns describing the elastic field surrounding the crack-tip. The tool is tested on X-ray strain measurements collected on a bainitic steel. In contrast to surface techniques the approach provides insights into the crack tip mechanics deep within the sample.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. The authors are grateful to the ESRF for ID15 beamtime awarded under MA-1483. Financial support of Universidad de Malaga through Plan Propio, Junta de Andalucía through Proyectos de Excelencia grant reference TEP-3244, Campus de Excelencia Internacional del Mar (CEIMAR) and Ministerio de Economia y Competitividad through grant reference MAT2016-76951-C2-2-P is also acknowledged. PJW acknowledges an ERC advanced grant

Modeling Wood Moisture Sorption Hysteresis Based on Similarity Hypothesis. Part II. Capillary-Radii Approach

The applicability of Mualem's capillary-radii model to wood moisture sorption hysteresis is evaluated. The model further simplifies the prediction of sorption hysteresis in that scanning curves can be obtained from the moisture content and relative humidity data of the boundary isotherms, with no other intermediate parameters needed. A comparison of predicted moisture contents with actual experimental data points for yellow-poplar (Liriodendron tulipifera) indicates that the model consistently underestimates the primary desorption scanning isotherms, with errors ranging from -0.01 to -1.31. These prediction errors are slightly larger than those obtained from an earlier model based on Mualem's direct similarity hypothesis

I-V curves of Fe/MgO (001) single- and double-barrier tunnel junctions

In this work, we calculate with ab initio methods the current-voltage characteristics for ideal single- and double-barrier Fe/MgO (001) magnetic tunnel junctions. The current is calculated in the phase-coherent limit by using the recently developed SMEAGOL code, combining the nonequilibrium Green function formalism with density-functional theory. In general we find that double-barrier junctions display a larger magnetoresistance, which decays with bias at a slower pace than their single-barrier counterparts. This is explained in terms of enhanced spin filtering from the middle Fe layer sandwiched in between the two MgO barriers. In addition, for double-barrier tunnel junctions, we find a well defined peak in the magnetoresistance at a voltage of V=0.1 V. This is the signature of resonant tunneling across a majority quantum well state. Our findings are discussed in relation to recent experiments

Terahertz photoconductivity and plasmon modes in double-quantum-well field-effect transistors

Double-quantum-well field-effect transistors with a grating gate exhibit a sharply resonant, voltage tuned terahertz photoconductivity. The voltage tuned resonance is determined by the plasma oscillations of the composite structure. The resonant photoconductivity requires a double-quantum well but the mechanism whereby plasma oscillations produce changes in device conductance is not understood. The phenomenon is potentially important for fast, tunable terahertz detectors

Evaluation of Three Organic Products With Three Doses for Boat Control (Phytophthora Infestans) in Potato Cultivation (Solanum Tuberosum cv. Fripapa) Riobamba Canton, Chimborazo Province

This research proposes to evaluate three ecological products with three doses for the control disease (Phytophthora infestans) in the potato crop (Solanum tuberosum cv. Fripapa) in the Riobamba canton, Chimborazo province. Three ecological products helped: Citrubact, Fosficarben, and Bioplus in high medium and low doses recommended by the producers, making applications every two weeks in this crop, to determine the best product in both the P. infestans control and performance of growing marginal rate. A design of randomized complete blocks (RCBD) in bifactorial combinations with 9 treatments, 4 replications and a control were used. As a result, the lower incidence of the disease was obtained by Fosficarben treatment in high doses (4cc/Lt) with 8.33%, due to the component ion phosphite, which has a direct effect on the fungal metabolism. The same behaviour was observed in the intensity where Fosficarben in high doses (4cc/Lt) obtained 12,83%, being the lower intensity of the research. The treatment with better performance was also Fosficarben in high doses with 21496, 80l<h/ha. According to the economic analysis the treatment composed by Citrubact in low-doses (lcc/Lt) got a higher marginal rate of return in relation to other treatments of 798.97% and a net income of 2631.28 USD and a variable cost, followed by the Bioplus treatmentdue in medium doses (4cc/Lt) with 765.14% of marginal rate. In conclusion, it is possible to control P. infestans in the potato crop by using ecological products, obtaining a good performance, a healthy product and economic income. Keywords: ecological products, potato crop, control disease. Resumen La presente investigación propone: evaluar tres productos ecológicos con tres dosis para el control de lancha (Phytophthora infestans) en el cultivo de papa (Solanum tuberosum cv. Fripapa) Cantón Riobamba, Provincia de Chimborazo. Ayudándonos de tres productos ecológicos: Citrubact. Fosficarben y Bioplus, en dosis alta media y baja recomendadas por las empresas productoras, realizando aplicaciones cada dos semanas en este cultivo, para determinar el mejor producto, tanto en el control de P. infestans, como en rendimiento del cultivo y tasa de retorno marginal. Se utilizó un diseño de bloques completos al azar (DBCA) en arreglo bifactorial combinatorio, con 9 tratamientos, 4 repeticiones y un testigo. Resultando que la menor incidencia de la enfermedad la obtuvo el tratamiento formado por Fosficarben en dosis alta (4cc/lt) con 8,33%, esto se debe a que contiene ion fosfito, que ejerce un efecto directo sobre el metabolismo fúngico. El mismo comportamiento se pudo observar en la intensidad donde Fosficarben en dosis alta (4cc/lt) obtuvo 12,83% siendo la menor intensidad del estudio. El tratamiento con mayor rendimiento también fue Fosficarben en dosis alta (4cc/lt) con 21496,80 kg/ha. En al análisis económico el tratamiento formado por Citrubact en dosis baja (1 cc/lt) obtuvo una mayor tasa de retorno marginal en relación al resto de tratamientos de 798,97%, con un beneficio neto de 2631,28 USD y un costo variable de 177,55 USD; debido a su dosis baja, es el más rentable de los tratamientos en estudio, seguido por el tratamiento conformado por Bioplus en dosis media (4 cc/lt) con 765,14% de tasa de retorno marginal. En conclusión se puede controlar a P. infestans en el cultivo de papa utilizando productos ecológicos, obteniendo un buen rendimiento, un producto sano y generando ingresos económicos. Palabras clave: productos ecológicos, cosecha de papas, control de enfermedades