Preface : (Boundary Element Method) Computers and Structures 83 (2005)

The Boundary Element Method is a powerful numerical technique well rooted in everyday engineering practice. This is shown by boundary element methods included in the most important commercial computer packages and in the continuous publication of books composed to explain the features of the method to beginners or practicing engineers. Our first paper in Computers & Structures on Boundary Elements was published in 1979 (C & S 10, pp. 351–362), so this Special Issue is for us not only the accomplishment of our obligation to show other colleagues the possibilities of a numerical technique in which we believe, but also the celebration of our particular silver jubilee with this Journal

A partial reconfiguration based microphone array network emulator

Nowadays, microphone arrays are used in many applications for sound-source localization or acoustic enhancement. The current Micro-Electro-Mechanical Systems (MEMS) technology allows the development of networks of microphone arrays at a relatively low cost. Unfortunately, the evaluation of these networks requires controlled acoustic environments, such as anechoic chambers, to avoid possible distortions and acoustic artifacts. In this paper, we present a partial reconfigurable FPGA platform to emulate a network of microphone arrays. Our platform provides a controlled simulated acoustic environment, able to evaluate the impact of different network configurations such as the number of microphones per array, the network's topology or the used detection method. Data fusion techniques, combining the data collected by each node, are used in this platform. In addition, our platform is also capable to converge to the ideal network with regards to power consumption, while still maintaining the desired level of sound-source localization accuracy. A graphical user interface provides a friendly control of the network and the parameters under test during the execution of the partial reconfiguration operations. Several experiments are presented to demonstrate some of the capabilities of our platform

Numerical treatment of thick shells with holes

A Boundary Integral Equation Method (B.I.E.M.)formulation is presented. After a general situation of the method among other usual numerical ones, the possibilities of discretization are developed. As this is done only in the boundary the treatment of tridimensional problems is greatly simplified in comparison with other methods. Some results on a simple shell with holes are finally presented

Demonstration of a partial reconfiguration based microphone array network emulator

The current Micro-Electro-Mechanical System (MEMS) technology allows to deploy relatively low-cost Wireless Sensor Networks (WSN) composed of MEMS microphone arrays for accurate sound-source localization. However, the evaluation and the selection of the most accurate and power-efficient network's topology is not trivial when considering dynamic MEMS microphone arrays. Despite software simulators are usually considered, they are high-computational intensive tasks which require hours to days to be completed. Our demonstrator is an FPGA-based network emulator, which provides a fast network design-space exploration. The user can easily evaluate a network's topology with different nodes' configurations and multiple sound sources in matter of seconds. An intuitive graphical user interface hides from the user the dynamic partial reconfigurations needed by the network emulator to set the node's configurations. As a result, a probability map generated from the fusion of the output data from the nodes and an error on the estimation of the sound-source location are graphically represented

Irreversible adiabatic decoherence of dipole-interacting nuclear-spin pairs coupled with a phonon bath

We study the quantum adiabatic decoherence of a multispin array, coupled with an environment of harmonic phonons, in the framework of the theory of open quantum systems. We follow the basic formal guidelines of the well-known spin-boson model, since in this framework it is possible to derive the time dependence of the reduced density matrix in the adiabatic time scale, without resorting to coarse-graining procedures. However, instead of considering a set of uncoupled spins interacting individually with the boson field, the observed system in our model is a network of weakly interacting spin pairs; the bath corresponds to lattice phonons, and the system-environment interaction is generated by the variation of the dipole-dipole energy due to correlated shifts of the spin positions, produced by the phonons. We discuss the conditions that the model must meet in order to fit within the adiabatic regime. By identifying the coupling of the dipole-dipole spin interaction with the low-frequency acoustic modes as the source of decoherence, we calculate the decoherence function of the reduced spin density matrix in closed way, and estimate the decoherence rate of a typical element of the reduced density matrix in one- and three-dimensional models of the spin array. Using realistic values for the various parameters of the model we conclude that the dipole-phonon mechanism can be particularly efficient to degrade multispin coherences, when the number of active spins involved in a given coherence is high. The model provides insight into the microscopic irreversible spin dynamics involved in the buildup of quasiequilibrium states and in the coherence leakage during refocusing experiments in nuclear magnetic resonance of crystalline solids.Fil: Dominguez, Federico Daniel. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: González, Cecilia Élida. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Segnorile, Hector Hugo. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Zamar, Ricardo César. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentin

Degradabilidad ruminal in siyu de granos de maíz de genotipos contrastantes en bovinos

The rumen digestion of three maize hybrids with contrasting characteristics: flint (PROZEA 33), semi dent (AW 190 mg) and dent (CL 849 EXP), presented in the form of whole grains and three milling fractions, was evaluated. Each material was incubated in the rumens of 3 Hereford steers, fitted with rumen cannulaes, in nylon bags, for 3, 6, 9, 12, 24 and 48 hours for the three fractions, and 48 hours only for whole grain. The information obtained was fitted by an exponential equation with lag time, and the results subjected to analysis of variance and compared by test of Tukey. The highest effective degradability (ED) (p<0.05) was that of the dent hybrid, followed by the semi dent and, finally, the flint hybrid, but the last two were not significantly different. The comparison between fractions shows that the highest ED was found in the smallest one (p<0.05), with no differences between the other two. The ED of the whole grains was very low for all hybrids. It is concluded that the particle size obtained by grinding and the hybrid type affect the rumen digestion of the maize grain, and that the whole grains of maize are poorly digested.Se evaluó la digestión ruminal de tres híbridos de maíz con características contrastantes: flint (PROZEA 33), semidentado (AW 190 MG) y dentado (EXP 849 CL), presentados en forma de grano entero y tres fracciones obtenidas de la molienda: (< 1mm; > 1mm <2mm; >2mm). Cada material fue incubado en el rumen de 3 novillos Hereford provistos de cánula ruminal, en bolsas de nylon, durante 3, 6, 9, 12, 24 y 48 horas para las tres fracciones y 48 horas solamente para el grano entero. La información obtenida fue ajustada mediante una ecuación exponencial con tiempo de retardo, y los resultados sometidos a análisis de varianza, y prueba de Tukey. La degradabilidad efectiva (DE) más alta (p<0.05) fue para el híbrido dentado, seguido por el semidentado y finalmente el flint, aunque estos dos últimos no mostraron diferencias significativas. La DE fue mayor en la fracción más fina, y similar en las otras dos. La degradabilidad ruminal de los granos de maíz enteros fue muy baja, para todos los híbridos. Se concluye que el tamaño de las partículas obtenidas por molienda y el tipo de híbrido utilizado afectan la digestión del grano de maíz, y que los granos enteros son pobremente digeridos

Clinical feasibility of quantitative ultrasound texture analysis: A robustness study using fetal lung ultrasound images

OBJECTIVES: To compare the robustness of several methods based on quantitative ultrasound (US) texture analysis to evaluate its feasibility for extracting features from US images to use as a clinical diagnostic tool. METHODS: We compared, ranked, and validated the robustness of 5 texture-based methods for extracting textural features from US images acquired under different conditions. For comparison and ranking purposes, we used 13,171 non-US images from widely known available databases (OUTEX [University of Oulu, Oulu, Finland] and PHOTEX [Texture Lab, Heriot-Watt University, Edinburgh, Scotland]), which were specifically acquired under different controlled parameters (illumination, resolution, and rotation) from 103 textures. The robustness of those methods with better results from the non-US images was validated by using 666 fetal lung US images acquired from singleton pregnancies. In this study, 2 similarity measurements (correlation and Chebyshev distances) were used to evaluate the repeatability of the features extracted from the same tissue images. RESULTS: Three of the 5 methods (gray-level co-occurrence matrix, local binary patterns, and rotation-invariant local phase quantization) had favorably robust performance when using the non-US database. In fact, these methods showed similarity values close to 0 for the acquisition variations and delineations. Results from the US database confirmed robustness for all of the evaluated methods (gray-level co-occurrence matrix, local binary patterns, and rotation-invariant local phase quantization) when comparing the same texture obtained from different regions of the image (proximal/distal lungs and US machine brand stratification). CONCLUSIONS: Our results confirmed that texture analysis can be robust (high similarity for different condition acquisitions) with potential to be included as a clinical tool

Genetic diversity for drought tolerance in the native forage grass Trichloris crinita and possible morpho-physiological mechanisms involved

The use of drought tolerant genotypes is one of the main strategies proposed for coping with the negative effects of global warming in dry lands. Trichloris crinita is a native forage grass occupying extensive arid and semi-arid regions in the American continent, and used for range grazing and revegetation of degraded lands. To identify drought-tolerant genotypes and possible underlying physiological mechanisms, this study investigated drought tolerance in 21 genetically diverse T. crinita genotypes under natural field conditions.. The accessions were grown under irrigated (control) and drought conditions for 84 days after initiation of the drought treatment (DAIDT), which coincided with flowering initiation. Various morpho-physiological traits were monitored, including total-, foliage-, and root biomass yield, dry matter partitioning to individual plant organs (roots, leaves, stems, and panicles), total leaf area, chlorophyll content, photochemical efficiency of photosystem II, stomatal conductance, and number of panicles per plant. Broad and significant variation (p<0.001) was found among the accessions for all the traits. Three highly tolerant and three very sensitive accessions were identified as the most contrasting materials, and their responses to drought stress were confirmed over two years of experiments. Under prolonged drought conditions (84 DAIDT), the tolerant accessions were generally more productive than the rest for all the biomass yield components analyzed, and this was associated with a postponed and more attenuated decrease in variables related to the plant photosynthetic activity, such as stomatal conductance, chlorophyll content, and photochemical efficiency. In contrast to previous findings, our data indicate no direct relationship between drought tolerance and the level of aridity in the accessions natural habitats, but rather suggest genetic heterogeneity and ample variation for drought tolerance in T. crinita natural populations derived from a particular location or environment. Also, having low total and forageable biomass yield, or increased biomass allocation to the roots (i.e., lower foliage/root ratio), under optimal water availability, were not associated with greater drought tolerance. The drought-tolerant accessions identified are of value for future genetic research and breeding programs, and as forage for range grazing and revegetation in arid regions.Fil: Dominguez, Deolindo Luis Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; ArgentinaFil: Cavagnaro, Juan Bruno. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; ArgentinaFil: Panasiti Ros, J.. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Departamento de Ciencias Biológicas. Cátedra de Fisiología Vegetal; ArgentinaFil: Le, A. T.. Jeju National University; Corea del SurFil: Chung, Y. S.. Jeju National University; Corea del SurFil: Cavagnaro, Pablo Federico. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Mendoza-San Juan. Estación Experimental Agropecuaria Mendoza; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentin

Relevamiento de la agricultura periurbana en una microregión de La Pampa

La creciente población de los centro urbanos genera tensión hacia las franjas periurbanas, donde se desarrollan actividades de producción de alimentos para la población próxima; desencadenando conflictos relacionados al uso de la tierra. Los emprendimientos, básicamente familiares, generan trabajo por lo que se motivan políticas para su apoyo, generando redes de intercambio de productos e insumos urbanos que sostienen estas tramas productivas. En este proceso surgen interrogantes sobre las prácticas productivas, la eficiencia y calidad en la distribución, la inocuidad de los alimentos y el impacto en la salud de la población. Este trabajo tiene como objetivo realizar un relevamiento de la Agricultura Urbana y Periurbana, realizado en la microrregión 6 de la provincia de La Pampa y cómo las Tecnologías de la Información y Comunicación permiten sistematizar y analizar la información relevada.Sociedad Argentina de Informática e Investigación Operativ