Las Positas College

Las empresas turísticas necesitan para poder competir ofrecer productos y servicios de calidad que satisfagan las necesidades de los consumidores. Esto implica disponer de un sistema de gestión de calidad que controle todo el proceso de prestación de servicios desde la compra de las materias primas hasta los servicios postventa. Un mecanismo habitual para incorporar la gestión de la calidad en las empresas turísticas son los sistemas de calidad, el más popular es el de la Q del ICTE. Para comprobar la eficiencia de la implantación del sistema de calidad Q del ICTE, hemos tomado los resultados económicos de dos muestras aleatorias de establecimientos hoteleros: unos que han implantado la Q y el otro que no. Y mediante un test para el contraste de diferencias entre dos medias, se ha determinado si el resultado medio de la primera muestra ha sido superior al resultado medio de la segunda (la muestra no expuesta).

Book Review| May 01 2018 Review: From Mission to Microchip: A History of the California Labor Movement by Fred B. Glass From Mission to Microchip: A History of the California Labor Movement. By Fred B. Glass. (Oakland, University of California Press, 2016. xviii + 524 pp.) John J. Rosen John J. Rosen Las Positas College Search for other works by this author on: This Site PubMed Google Scholar Pacific Historical Review (2018) 87 (2): 380–381. https://doi.org/10.1525/phr.2018.87.2.380 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation John J. Rosen; Review: From Mission to Microchip: A History of the California Labor Movement by Fred B. Glass. Pacific Historical Review 1 May 2018; 87 (2): 380–381. doi: https://doi.org/10.1525/phr.2018.87.2.380 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentPacific Historical Review Search This content is only available via PDF. © 2018 by the Pacific Coast Branch, American Historical Association2018 Article PDF first page preview Close Modal You do not currently have access to this content.

Abstract Generalized constitutive models, which can be used in explicit finite-element analysis, are being developed to accurately model composite systems under impact conditions. These models requi...

ABSTRACT We present observations of Q1549-C25, an ∼ L * star-forming galaxy at z = 3.15 for which Lyman-continuum (LyC) radiation is significantly detected in deep Keck/LRIS spectroscopy. We find no evidence of contamination from a lower-redshift interloper close to the line of sight in the high signal-to-noise spectrum of Q1549-C25. Furthermore, the morphology of Q1549-C25 in V 606, J 125, and H 160 Hubble Space Telescope (HST) imaging reveals that the object consists of a single, isolated component within 1″. In combination, these data indicate Q1549-C25 as a clean spectroscopic detection of LyC radiation, only the second such object discovered to date at z ∼ 3. We model the spectral energy distribution of Q1549-C25, finding evidence of negligible dust extinction, an age (assuming continuous star formation) of ∼1 Gyr, and a stellar mass of M * = 7.9 × 10 9 M ⊙ . Although it is not possible to derive strong constraints on the absolute escape fraction of LyC emission, f esc(LyC), from a single object, we use simulations of intergalactic and circumgalactic absorption to infer f esc ( LyC ) ≥ 0.51 at 95% confidence. The combination of deep Keck/LRIS spectroscopy and Hubble Space Telescope imaging is required to assemble a larger sample of objects like Q1549-C25, and obtain robust constraints on the average f esc(LyC) at z ∼ 3 and beyond.

The need for accurate material models to simulate the deformation, damage, and failure of polymer matrix composites under impact conditions is becoming critical as these materials are gaining increased usage in the aerospace and automotive industries. There are a variety of material models currently available within commercial transient dynamic finite-element codes to analyze the response of composite materials under impact conditions. However, there are several features that are lacking in the currently available models that could improve the predictive capability of the impact simulations. To address these needs, a combined elasto-plastic model with damage suitable for implementation within transient dynamic finite-element codes has been developed. A key feature of the improved material model is the use of tabulated stress-strain data in a variety of coordinate directions to fully define the stress-strain response of the material. Currently, the model development efforts have focused on creating the plasticity portion of the model. A commonly used composite failure model has been generalized and extended to a strain-hardening-based orthotropic yield function with a non-associative flow rule. The coefficients of the yield function are computed based on the input stress-strain curves using the effective plastic strain as the tracking variable. The coefficients of the flow rule are determined in a systematic manner based on the available stress-strain data for the material. The evolution of the yield surface is examined, in detail, for a sample composite. A numerical algorithm based on the classic radial return method is employed to compute the evolution of the effective plastic strain. A specific laminated composite is examined to demonstrate the process of characterizing and analyzing the response of a composite using the developed model. The developed material model is suitable for use within commercial transient dynamic finite-element codes for use in analyzing the nonlinear response of polymer composites.

A meshfree modeling technique of material flow in the three-dimensional multiphysics thermomechanical friction stir welding process is presented. In this numerical model, the discretization in space is derived by the Element-Free Galerkin method using a Lagrangian meshfree convex approximation. The discrete thermal and mechanical equations are weakly coupled as the time advances using a forward difference scheme. A mortar contact algorithm is employed to model the stirring effect and heat generation due to frictional contact. Heat conductance between contacting bodies is considered as a function of contact pressure. A two-way adaptive procedure is introduced to the coupled thermomechanical system to surpass potential numerical problems associated with the extensive material deformation and spatial discretization. In each adaptive phase, a consistent projection operation utilizing the first-order meshfree convex approximation is performed to remap the solution variables. Finally, a three-dimensional multiphysics thermomechanical coupled friction stir welding problem is analyzed to demonstrate the effectiveness of the present meshfree numerical procedure.

SUMMARYA three‐dimensional microstructure‐based finite element framework is presented for modeling the mechanical response of rubber composites in the microscopic level. This framework introduces a novel finite element formulation, the meshfree‐enriched FEM, to overcome the volumetric locking and pressure oscillation problems that normally arise in the numerical simulation of rubber composites using conventional displacement‐based FEM. The three‐dimensional meshfree‐enriched FEM is composed of five‐noded tetrahedral elements with a volume‐weighted smoothing of deformation gradient between neighboring elements. The L2‐orthogonality property of the smoothing operator enables the employed Hu–Washizu–de Veubeke functional to be degenerated to an assumed strain method, which leads to a displacement‐based formulation that is easily incorporated with the periodic boundary conditions imposed on the unit cell. Two numerical examples are analyzed to demonstrate the effectiveness of the proposed approach. Copyright © 2012 John Wiley & Sons, Ltd.

The modelling of parachutes at Irvin Aerospace Inc. was based on the penalty Euler-Lagrange coupling method to compute the interaction between an Arbitrary Lagrange Euler formulation for the air flow and an updated Lagrangian finite element formulation for the canopy dynamics. This approach did not permit the effect of fabric porosity to be accounted for. In this paper, a new porosity Euler-Lagrange coupling models the fabric permeability by assessing the interaction forces based on the Ergun porous flow model. This paper provides validations for the technique when considering parachute applications and discusses the interest of this development to the parachute designer.

The purpose of this study is to demonstrate a methodology for springback compensation in sheet metal stamping operations. An optimization method based on the D-optimality criterion for experimental design and successive linear response surface approximations is employed to minimize the difference between the simulation results and the intended design. A subdomain reduction scheme is applied to determine the subdomain size for each iteration. The procedure, which has been implemented in the program LS-OPT, is interfaced with the simulation package LS-DYNA, and the parametric preprocessor TrueGrid. These tools are used to input original tool geometry, material, and process parameters, identify design variables, perform springback simulations and output optimized tool geometry. The standardized NUMISHEET’96 S-Rail is used as a benchmark example in this study. A converged optimized design is obtained in four or five iterations. It is found that springback trends are consistent with changes in the die shape, thereby suggesting other effective strategies for springback compensation.