Beyond the simple Proximity Force Approximation: geometrical effects on the non-retarded Casimir interaction

We study the geometrical corrections to the simple Proximity Force Approximation for the non-retarded Casimir force. We present analytical results for the force between objects of various shapes and substrates, and between pairs of objects. We compare the results to those from more exact numerical calculations. We treat spheres, spheroids, cylinders, cubes, cones, and wings; the analytical PFA results together with the geometrical correction factors are summarized in a table.Comment: 18 pages, 19 figures, 1 tabl

Prácticas de consumo más sustentables de la energía eléctrica

Para lograr un uso racional y sustentable de la energía eléctrica en edificaciones, se requiere aplicar estrategias de ahorro que sean consecuencia de un análisis del consumo eléctrico, de la cultura de uso de los equipos, de las actividades de conservación y mantenimiento a los equipos e instalaciones eléctricas. Este trabajo busca convertirse en una guía con información que relaciona la ingeniería eléctrica con la sustentabilidad para que las personas puedan realizar acciones de ahorro de energía eléctrica

STRUCTURE ANALYSIS AND BIOMASS MODELS FOR PLUM TREE (PRUNUS DOMESTICA L.) IN ECUADOR

The development of dendrometric methodologies could allow accurate estimation of variables associated with the crown, such as primary production (fruit and timber) and tree vigor. The aim of this work was to develop a suitable method to estimate woody biomass in plum trees (Prunus domestica L.) in Imbabura, Ecuador by using an adapted dendrometry. Form factors and regression models were defined for branch volume calculation. From this, the distribution of woody biomass in the crown tree was characterized in every stratum. Occupation Factor and regression models were obtained in order to calculate the biomass in the crown tree, which can be used to estimate the CO2 captured in its structure during its development. Regression models for calculation of whole volume of the tree and pruned biomass were directly obtained from crown diameter and crown height with Rajustated 2 of 0.74 and 0.81. The average moisture content of green material was 51%, and the average density of dry material was 0.66 ± 0.07 g cm−3. Proximate analysis of plum wood showed at 79.8 ± 9.2% volatiles and 2.1 ± 0.3% ash. Elemental analysis of the wood pointed to 46.5 ± 1.2% C, 6.1 ± 0.5% H, 46.3 ± 1.2% O, 0.6 ± 0.3% N, 0.06 ± 0.02% S and 0.02 ± 0.01% Cl. Cl, S and N contents are lower than the limits established by the standard EN 14691-part 4.With 46% of C, considering the relation 3.67 (44/12) between CO2 and C content, the CO2 sequestrated in the materials is 1.11 Mg m−3 wood material. Such method represents a tool to manage orchard resources and for assessing other parameters, such as raw materials for cultivation, fruit production, CO2 sink and waste materials (residual wood) used for energy or industry.The authors appreciate the financial support provided by the ECUMASA, Red ecuatoriana para la investigacion del aprovechamiento energetico de la biomasa.Velázquez Martí, B.; Cazco-Logroño, C. (2017). STRUCTURE ANALYSIS AND BIOMASS MODELS FOR PLUM TREE (PRUNUS DOMESTICA L.) IN ECUADOR. Experimental Agriculture. 54(1):133-141. https://doi.org/10.1017/S001447971600079XS133141541Velázquez-Martí, B., Estornell, J., López-Cortés, I., & Martí-Gavilá, J. (2012). Calculation of biomass volume of citrus trees from an adapted dendrometry. Biosystems Engineering, 112(4), 285-292. doi:10.1016/j.biosystemseng.2012.04.011Velázquez-Martí, B., Fernández-González, E., López-Cortés, I., & Salazar-Hernández, D. M. (2011). Quantification of the residual biomass obtained from pruning of vineyards in Mediterranean area. Biomass and Bioenergy, 35(8), 3453-3464. doi:10.1016/j.biombioe.2011.04.009Velázquez-Martí, B., Fernández-González, E., López-Cortés, I., & Salazar-Hernández, D. M. (2011). Quantification of the residual biomass obtained from pruning of trees in Mediterranean olive groves. Biomass and Bioenergy, 35(7), 3208-3217. doi:10.1016/j.biombioe.2011.04.042B. Velazquez-Marti, & E. Annevelink. (2009). GIS Application to Define Biomass Collection Points as Sources for Linear Programming of Delivery Networks. Transactions of the ASABE, 52(4), 1069-1078. doi:10.13031/2013.27776Sajdak, M., & Velazquez-Marti, B. (2012). Estimation of pruned biomass form dendrometric parameters on urban forests: Case study of Sophora japonica. Renewable Energy, 47, 188-193. doi:10.1016/j.renene.2012.04.002Pérez-Arévalo, J. J., Callejón-Ferre, A. J., Velázquez-Martí, B., & Suárez-Medina, M. D. (2015). Prediction models based on higher heating value from the elemental analysis of neem, mango, avocado, banana, and carob trees in Guayas (Ecuador). Journal of Renewable and Sustainable Energy, 7(5), 053122. doi:10.1063/1.4934593Maltamo, M. (2004). Estimation of timber volume and stem density based on scanning laser altimetry and expected tree size distribution functions. Remote Sensing of Environment, 90(3), 319-330. doi:10.1016/j.rse.2004.01.006García-Tejero, I. F., Durán-Zuazo, V. H., Arriaga, J., & Muriel-Fernández, J. L. (2012). Relationships between trunk- and fruit-diameter growths under deficit-irrigation programmes in orange trees. Scientia Horticulturae, 133, 64-71. doi:10.1016/j.scienta.2011.10.022Estornell, J., Velázquez-Martí, B., López-Cortés, I., Salazar, D., & Fernández-Sarría, A. (2014). Estimation of wood volume and height of olive tree plantations using airborne discrete-return LiDAR data. GIScience & Remote Sensing, 51(1), 17-29. doi:10.1080/15481603.2014.883209EN 14691-part 4 (2009). Solid biofuels – Fuel Specifications and classes – Wood chips for non-industrial use. 10p.Doruska, P. F., & Burkhart, H. E. (1994). Modeling the diameter and locational distribution of branches within the crowns of loblolly pine trees in unthinned plantations. Canadian Journal of Forest Research, 24(12), 2362-2376. doi:10.1139/x94-305Deckmyn, G., Evans, S. P., & Randle, T. J. (2006). Refined pipe theory for mechanistic modeling of wood development. Tree Physiology, 26(6), 703-717. doi:10.1093/treephys/26.6.703Bessou, C., Basset-Mens, C., Tran, T., & Benoist, A. (2012). LCA applied to perennial cropping systems: a review focused on the farm stage. The International Journal of Life Cycle Assessment, 18(2), 340-361. doi:10.1007/s11367-012-0502-zAndersen, H.-E., Reutebuch, S. E., & McGaughey, R. J. (2006). A rigorous assessment of tree height measurements obtained using airborne lidar and conventional field methods. Canadian Journal of Remote Sensing, 32(5), 355-366. doi:10.5589/m06-030Olson, M. E., & Rosell, J. A. (2012). Vessel diameter-stem diameter scaling across woody angiosperms and the ecological causes of xylem vessel diameter variation. New Phytologist, 197(4), 1204-1213. doi:10.1111/nph.12097Gracia, C., Velázquez-Martí, B., & Estornell, J. (2014). An application of the vehicle routing problem to biomass transportation. Biosystems Engineering, 124, 40-52. doi:10.1016/j.biosystemseng.2014.06.00

Emission lines from rotating proto-stellar jets with variable velocity profiles. I. Three-dimensional numerical simulation of the non-magnetic case

Using the Yguazu-a three-dimensional hydrodynamic code, we have computed a set of numerical simulations of heavy, supersonic, radiatively cooling jets including variabilities in both the ejection direction (precession) and the jet velocity (intermittence). In order to investigate the effects of jet rotation on the shape of the line profiles, we also introduce an initial toroidal rotation velocity profile, in agreement with some recent observational evidence found in jets from T Tauri stars which seems to support the presence of a rotation velocity pattern inside the jet beam, near the jet production region. Since the Yguazu-a code includes an atomic/ionic network, we are able to compute the emission coefficients for several emission lines, and we generate line profiles for the H, [O I]6300, [S II]6716 and [N II]6548 lines. Using initial parameters that are suitable for the DG Tau microjet, we show that the computed radial velocity shift for the medium-velocity component of the line profile as a function of distance from the jet axis is strikingly similar for rotating and non-rotating jet models. These findings lead us to put forward some caveats on the interpretation of the observed radial velocity distribution from a few outflows from young stellar objects, and we claim that these data should not be directly used as a doubtless confirmation of the magnetocentrifugal wind acceleration models.Comment: 15 pages, 8 figures. Accepted to publication in Astronomy and Astrophysic

The topological classification of one-dimensional symmetric quantum walks

We give a topological classification of quantum walks on an infinite 1D lattice, which obey one of the discrete symmetry groups of the tenfold way, have a gap around some eigenvalues at symmetry protected points, and satisfy a mild locality condition. No translation invariance is assumed. The classification is parameterized by three indices, taking values in a group, which is either trivial, the group of integers, or the group of integers modulo 2, depending on the type of symmetry. The classification is complete in the sense that two walks have the same indices if and only if they can be connected by a norm continuous path along which all the mentioned properties remain valid. Of the three indices, two are related to the asymptotic behaviour far to the right and far to the left, respectively. These are also stable under compact perturbations. The third index is sensitive to those compact perturbations which cannot be contracted to a trivial one. The results apply to the Hamiltonian case as well. In this case all compact perturbations can be contracted, so the third index is not defined. Our classification extends the one known in the translation invariant case, where the asymptotic right and left indices add up to zero, and the third one vanishes, leaving effectively only one independent index. When two translationally invariant bulks with distinct indices are joined, the left and right asymptotic indices of the joined walk are thereby fixed, and there must be eigenvalues at $1$ or $-1$ (bulk-boundary correspondence). Their location is governed by the third index. We also discuss how the theory applies to finite lattices, with suitable homogeneity assumptions.Comment: 36 pages, 7 figure