Monte Carlo simulations of post-common-envelope white dwarf + main sequence binaries: comparison with the SDSS DR7 observed sample

Detached white dwarf + main sequence (WD+MS) systems represent the simplest population of post-common envelope binaries (PCEBs). Since the ensemble properties of this population carries important information about the characteristics of the common-envelope (CE) phase, it deserves close scrutiny. However, most population synthesis studies do not fully take into account the effects of the observational selection biases of the samples used to compare with the theoretical simulations. Here we present the results of a set of detailed Monte Carlo simulations of the population of WD+MS binaries in the Sloan Digital Sky Survey (SDSS) Data Release 7. We used up-to-date stellar evolutionary models, a complete treatment of the Roche lobe overflow episode, and a full implementation of the orbital evolution of the binary systems. Moreover, in our treatment we took into account the selection criteria and all the known observational biases. Our population synthesis study allowed us to make a meaningful comparison with the available observational data. In particular, we examined the CE efficiency, the possible contribution of internal energy, and the initial mass ratio distribution (IMRD) of the binary systems. We found that our simulations correctly reproduce the properties of the observed distribution of WD+MS PCEBs. In particular, we found that once the observational biases are carefully taken into account, the distribution of orbital periods and of masses of the WD and MS stars can be correctly reproduced for several choices of the free parameters and different IMRDs, although models in which a moderate fraction (<=10%) of the internal energy is used to eject the CE and in which a low value of CE efficiency is used (<=0.3) seem to fit better the observational data. We also found that systems with He-core WDs are over-represented in the observed sample, due to selection effects.Comment: 15 pages, 7 figures, accepted for publication in A&

Hydraulic and stability analysis of the supporting layer of wedge-shaped blocks

Presented at the Protections 2016: 2nd international seminar on dam protection against overtopping: concrete dams, embankment dams, levees, tailings dams held on 7th-9th September, 2016, at Colorado State University in Fort Collins, Colorado, USA. The increasing demand for dam and levee safety and flood protection has motivated new research and advancements and a greater need for cost-effective measures in overtopping protection as a solution for overtopping concerns at levees and dams. This seminar will bring together leading experts from practice, research, development, and implementation for two days of knowledge exchange followed by a technical tour of the Colorado State University Hydraulic Laboratory with overtopping flume and wave simulator. This seminar will focus on: Critical issues related to levees and dams; New developments and advanced tools; Overtopping protection systems; System design and performance; Applications and innovative solutions; Case histories of overtopping events; Physical modeling techniques and recent studies; and Numerical modeling methods.Includes bibliographical references.Wedge shaped blocks (WSB) are attracting increasing attention as protection against overtopping for earth and rock-fill dams. However, there are limited examples of application and some aspects of the technology merit additional research and improvement. One key issue is the design of drainage and supporting layer for WSB protections. During overtopping, part of the overflow leaks through the joints between blocks, hence circulating through the granular material. The permeability and thickness of the supporting layer must be sufficient to prevent the flow from generating pressure on the bottom side of the blocks, which contributes to its destabilization. However, it must also be structurally stable to avoid undesirable deformations on the downstream face. Both the material permeability and the layer thickness determine the hydraulic behavior of this element. These, together with the weight of the blocks and the slope of the downstream face, directly influence mass and block stability. These aspects should be taken into account for the numerical modeling of seepage through the supporting layer. To this end, an application of the open source software Kratos Multi-physics was employed. A parametric study was conducted to quantify the influence of each design variable in the safety factor against mass sliding of the supporting and drainage layer

Lo humano en riesgo: la educación frente a la globalización

Los especialistas ponen al descubierto los principales desafíos político-educativos, teóricos y prácticos del discurso sobre la educación y plantean la necesidad de que esta se abra para dar acceso a la integración de la persona y a la orientación de una sociedad configurada por valores humanos fundamentales, esto es, la búsqueda de una educación en verdad humana en la era de la globalización.ITESO, A.C

Applications of numerical methods in design and evaluation of overtopping protection systems

Presented at the Protections 2016: 2nd international seminar on dam protection against overtopping: concrete dams, embankment dams, levees, tailings dams held on 7th-9th September, 2016, at Colorado State University in Fort Collins, Colorado, USA. The increasing demand for dam and levee safety and flood protection has motivated new research and advancements and a greater need for cost-effective measures in overtopping protection as a solution for overtopping concerns at levees and dams. This seminar will bring together leading experts from practice, research, development, and implementation for two days of knowledge exchange followed by a technical tour of the Colorado State University Hydraulic Laboratory with overtopping flume and wave simulator. This seminar will focus on: Critical issues related to levees and dams; New developments and advanced tools; Overtopping protection systems; System design and performance; Applications and innovative solutions; Case histories of overtopping events; Physical modeling techniques and recent studies; and Numerical modeling methods.Includes bibliographical references.The development of overtopping protection systems often requires detailed analyses of complex physical phenomena. This hinders the comprehensive knowledge of their behavior, and therefore the development of suitable design criteria. In recent years, the authors have developed and validated different methods, combining continuous, particle and discrete numerical techniques, to obtain accurate and reliable solutions of different numerical problems involving fluid-soil-structure interaction. In this contribution, some applications of these methods to the study of dam protection against overtopping are presented. The main advantages of this approach include the ability to extract results of the governing variables (pressure, velocity) at any location of the domain, and the possibility to consider scenarios without the restrictions of the experimental facilities (flow rates, size, scale effects). In particular, the contribution gathers examples of application of numerical methods in a) analysis of rockfill dam stability against overtopping, including seepage evolution and deformation of the downstream shoulder, and b) stability analysis of wedge-shaped-blocks subjected to vandalism

Relación entre motivos de práctica de actividad física y nivel de formación de usuarios de centros deportivos

Los centros deportivos necesitan adaptar sus servicios a los intereses de los usuarios. Para ello es imprescindible segmentar el mercado atendiendo a las tradicionales variables sociodemográficas y otras como las motivaciones y las actitudes. El objetivo de la investigación fue conocer los motivos de los usuarios para acudir a los centros deportivos estableciendo perfiles diferenciadores en función de sus diferentes niveles de formación académica. Los usuarios señalaron el Disfrute (3.93 ± .60) y el Fitness/Salud (3.84 ± .71) como los motivos más relevantes. Los usuarios sin formación se sentían motivados por el Fitness y Disfrute, mientras que los usuarios con formación profesional por Fitness y Apariencia. La vinculación de los motivos de práctica de actividad física del usuario con su nivel de formación mostró diferencias significativas en todos los factores. Estos resultados posibilitan ofertar servicios más eficientemente ya que permite un mejor ajuste a las demandas de los usuarios aumentando su fidelidad

Análisis de la validez de las ecuaciones de estimación del 1RM con técnica de parada: una nueva propuesta

This study validates new regression equations to estimate the value of the absolute maximum dynamic strength (1RM) by means of a maximum number of repetitions test to muscular failure (nRM) executed with stop technique. Also, this study assesses the validity of the equations that are already stablished in the international publications to estimate the load (% 1RM) and the 1RM value from a nRM test in executions with stop technique. The results indicate that the new equations proposed in this research [Bench Press 1RM = weight lifted in kg (-0,01841*nRM)+0,981; Full Squat 1RM = weight lifted in kg (-0,01176*nRM)+0,975] show substantially better validity levels (SEM = 1,8-2,2 kg; R2 = 0,956-0,988), and therefore of greater predictive ability, than the rest of equations described in the international literature to date.El objetivo de esta investigación es validar nuevas ecuaciones de regresión para estimar el valor de fuerza dinámica máxima absoluta (1RM) mediante test de máximo número de repeticiones hasta el fallo muscular (nRM) ejecutados con técnica de parada o stop. Igualmente, se estudian los niveles de validez que presentan las ecuaciones que ya se encuentran actualmente definidas en la literatura internacional para estimar la magnitud de la carga (%1RM) y el valor de 1RM a partir de un test nRM en ejecuciones con técnica de parada. Los resultados indican que las nuevas ecuaciones propuestas en esta investigación [1RM en Press Banca = masa desplazada en kg (-0,01841*nRM)+0,981; 1RM en Sentadilla Completa = masa desplazada en kg (-0,01176*nRM)+0,975] muestran indicadores sustancialmente mejores de validez(ET = 1,8-2,2 kg; R2 = 0,956-0,988), y por lo tanto de mayor capacidad predictiva, que el resto de ecuaciones definidas en la literatura internacional hasta la fecha

Cluster variation method and disorder varieties of two-dimensional Ising-like models

I show that the cluster variation method, long used as a powerful hierarchy of approximations for discrete (Ising-like) two-dimensional lattice models, yields exact results on the disorder varieties which appear when competitive interactions are put into these models. I consider, as an example, the plaquette approximation of the cluster variation method for the square lattice Ising model with nearest-neighbor, next-nearest-neighbor and plaquette interactions, and, after rederiving known results, report simple closed-form expressions for the pair and plaquette correlation functions.Comment: 10 revtex pages, 1 postscript figur

Confinement Effects in Antiferromagnets

Phase equilibrium in confined Ising antiferromagnets was studied as a function of the coupling (v) and a magnetic field (h) at the surfaces, in the presence of an external field H. The ground state properties were calculated exactly for symmetric boundary conditions and nearest-neighbor interactions, and a full zero-temperature phase diagram in the plane v-h was obtained for films with symmetry-preserving surface orientations. The ground-state analysis was extended to the H-T plane using a cluster-variation free energy. The study of the finite-T properties (as a function of v and h) reveals the close interdependence between the surface and finite-size effects and, together with the ground-state phase diagram, provides an integral picture of the confinement in anisotropic antiferromagnets with surfaces that preserve the symmetry of the order parameter.Comment: 10 pages, 8 figures, Accepted in Phys. Rev.