Nondestructive testing using stress waves: wave propagation in layered media

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaves 35-36).The use of stress waves in several civil engineering applications such as nondestructive testing of soil deposits or pavement systems has become extremely popular over the last few years. In all cases, a dynamic impulse is applied to the surface of the investigated medium, and the corresponding motions associated with the propagation of stress waves are recorded by receivers located at different points away from the source of loading. In many applications, these are primarily surface (Rayleigh) waves. The properties of the medium and the potential existence of defects can be determined from the appropriate interpretation of the recorded motions. Although current interpretation processes are performed considering accurate solutions to the dynamic problem, a situation of interest arises when a soil stratum is underlain by a much stiffer material. Researchers have established that no surface waves will propagate through a soil medium below a threshold frequency for the case when the soil base is assumed to be infinitely rigid. When dealing with vertical loads, some researchers had originally suggested that the threshold frequency corresponds to the natural frequency of the soil layer in dilatation/compression. This would imply that for a saturated soil having a value of Poisson's Ratio close to 0.5, surface waves would never be generated - a conjecture which is clearly incorrect. The goals of the research project were to determine the threshold frequency as a function of Poisson's Ratio of the soil layer and to investigate the surface-wave propagation phenomena for values close to the mentioned frequency. Two approaches were utilized to achieve the research objectives. The first approach consisted in developing analytical expressions for the relations between displacements and stresses due to plane waves propagating in a soil layer. The second approach considered the study of the phase shift in the motions at different points under steady state conditions. Both approaches used wave propagation results provided by computer simulation programs. The results of this study are figures showing the variation of the apparent wave propagation velocity corresponding to the threshold frequency divided by the shear wave velocity of the medium as a function of Poisson's ratio and a comparison with the P-wave velocity

Microporomechanical modeling of shale

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 401-429).Shale, a common type of sedimentary rock of significance to petroleum and reservoir engineering, has recently emerged as a crucial component in the design of sustainable carbon and nuclear waste storage solutions and as a prolific natural gas source. Despite its importance, the highly heterogeneous and anisotropic nature of shale has challenged the theoretical modeling and prediction of its mechanical properties. This thesis presents a comprehensive microporomechanics framework for developing predictive models for shale poroelasticity and strength. Modeling is accomplished through a multi-scale approach, in which the experimental evidence gathered from novel nanoindentation techniques and conventional macroscopic tests informs the development of a suit of micromechanics tools for linking composition and microstructure to material performance. Based on a closed loop approach of calibration and validation of elastic and strength properties at different length scales, it was possible to deconstruct shale to the scale of an elementary material unit with mechanical behaviors governed by invariant properties, and to upscale these behaviors from the nanoscale to the macroscale of engineering applications. The elementary building block for elasticity is an anisotropic solid characterizing the in situ stiffness of highly consolidated clay.(cont.) This intrinsic behavior represents the composite response of clay platelets, interlayer galleries, and interparticle contacts, yielding an invariant stiffness with respect to clay mineralogy. The anisotropic nanogranular nature of the porous clay in shale as inferred from nanoindentation is confirmed through micromechanics modeling. The intrinsic anisotropy of the clay fabric is suggested as the dominant factor driving the multi-scale anisotropic poroelasticity of unfractured shale compared to the contributions of geometrical sources related to shapes and orientations of particles. For strength properties, the micromechanics approach revealed that the frictional behavior of the elementary unit of compacted clay is scale independent, whereas a scale effect modifies its cohesive behavior. Having established a fundamental material unit and the adequate micromechanics representation for the microstructure, the macroscopic diversity of shale predominantly depends on two volumetric properties derived from mineralogy and porosity: the clay packing density and the silt inclusion volume fraction. The proposed two-parameter microporoelastic and strength models represent appealing alternatives for use in geomechanics and geophysics applications.by J. Alberto Ortega.Ph.D

Comportamiento Innovador de la Estación de servicio Inés Galeano en el Municipio de Sébaco, Departamento de Matagalpa, periodo del año 2016

La presente investigación tiene como objetivo, analizar el comportamiento innovador de la empresa: Estación de servicio Inés Galeano en la ciudad de Sébaco en el departamento de Matagalpa, en el periodo del año 2016. Esta investigación se realizó con el propósito de identificar si la empresa ha realizado Innovaciones y si estas se realizaron de forma proactiva o reactiva. La importancia de conocer y analizar las principales innovaciones implementadas por la Estación de servicio Inés Galeano radica en que permite a la empresa conocer cuáles son sus aciertos y flaquezas en términos de innovación lo cual es cada vez más importante, ya que en un mercado cada vez más competitivo y globalizado una empresa que no innova de manera acertada tiende a desaparecer. La estación de servicios Inés Galeano es una empresa con un comportamiento Innovador mixto dirigida a un sector amplio del mercado, las innovaciones aplicadas permiten a la empresa la preferencia y la fidelidad de sus clientes aunque la empresa debe prestar atención a la percepción de sus clientes ya que al realizar acciones de forma innovadora estas deben estar acordes a la demanda del mercado. Las principales innovaciones de la estación de servicios Inés Galeano son innovación en las mejoras de la calidad del producto, la innovación en la calidad de la atención al cliente, mejoras constantes en la infraestructura y algunas técnicas de merchandising así como la diversificación en nuevos servicios. Por otra parte la Estación de servicios Inés Galeano realiza las innovaciones de manera rápida lo cual es de gran importancia porque le permite ser pionera en el mercad

Factores de riesgo para Escabiosis en pacientes atendidos porconsultorio externo del Hospital La Caleta, 2018 - 2019

La escabiosis (sarna) es una infección contagiosa relacionada principalmente con las consecuencias de la pobreza como el hacinamiento, se extiende rápidamente de persona a persona, especialmente en las que no poseen una adecuada higiene. Nuestro principal objetivo fue determinar los factores de riesgo para escabiosis en pacientes atendidos por consultorio externo en el Hospital la Caleta durante los años 2018 y 2019, a través de un estudio tipo analítico, observacional, retrospectivo y transversal, de diseño casos y controles. Se analizó un total de 110 historias clínicas y se usó un muestreo de tipo aleatorio simple. En el análisis bivariado los factores de riesgo asociados fueron Hacinamiento (OR=6.02, IC 95% 2.63 ? 13.77 y p=0.000), grupo etario niñez (OR=2.84, IC 95% 1.31 ? 6.16 y p=0.008), pobre aseo personal (OR=4.92, IC 95% 1.89 ? 12.83 y p=0.000), contacto con una persona con prurito (OR=10.872, IC 95% 2.361 ? 50.059 y p=0.000) y antecedente de escabiosis (OR=16.714, IC 95% 2.102 ? 132.927 y p=0.001); al análisis de regresión lineal se encontró una fuerte asociación para las variables hacinamiento (p=0.000), pobre aseo personal (p=0.005), contacto con una persona con prurito (p=0.008) y grupo etario niñez (p=0.018). Se concluye que en el Hospital La Caleta los principales factores de riesgo para escabiosis fueron el hacinamiento, el pobre aseo personal, el contacto con una persona con prurito, el grupo etario niñez y el antecedente de escabiosis.Tesi

Taller de práctica de valores y su efecto en la convivencia escolar en una institución educativa privada, SJL. Lima,2023

Esta investigación estudió la convivencia escolar (CE) y el efecto de la práctica de valores(PV) en ella. El objetivo principal fue determinar qué incidencia tiene la PV en ella.. La metodología fue de tipo aplicada, nivel explicativo, método hipotéticodeductivo, enfoque cuantitativo, y diseño cuasi-experimental. La población consistió en 86 alumnos de secundaria en una IE privada en SJL, Lima, Perú. La muestra fue de 63 estudiantes. Los datos se recolectaron mediante encuesta y un cuestionario validado por expertos con confiabilidad de 0.8 (Cronbach). La muestra se separó en dos grupos, grupo experimental(GE) y grupo control(GC). Ambos grupos se sometierom a un pre-Test. Seguidamente se impartió un taller de valores(TdV) de siete sesiones sólo al GE. Finalmente ambos grupos respondieron a un post-Test. Los resultados mostraron que el TdV tuvo un efecto significativo de 18.22% de mejora en la convivencia estudiantil. para el GE. La prueba U de Mann-Whitney [p de 0,012 (p < 0,05)] y Wilcoxon [p=0,000 (p < 0,05)]. permitieron aceptar la hipótesis general y las específicas, que postulaban que dicha influencia significativa de los valores (PV) ocurrió en sus tres dimensiones (convivencia inclusiva, convivencia democrática, y convivencia pacífica)

Towards more sustainable material formulations: a comparative assessment of PA11-SGW flexural performance versus oil-based composites

The replacement of commodity polyolefin, reinforced with glass fiber (GF), by greener alternatives has been a topic of research in recent years. Cellulose fibers have shown, under certain conditions, enough tensile capacities to replace GF, achieving competitive mechanical properties. However, if the objective is the production of environmentally friendlier composites, it is necessary to replace oil-derived polymer matrices by bio-based or biodegradable ones, depending on the application. Polyamide 11 (PA11) is a totally bio-based polyamide that can be reinforced with cellulosic fibers. Composites based on this polymer have demonstrated enough tensile strength, as well as stiffness, to replace GF-reinforced polypropylene (PP). However, flexural properties are of high interest for engineering applications. Due to the specific character of short-fiber-reinforced composites, significant differences are expected between the tensile and flexural properties. These differences encourage the study of the flexural properties of a material prior to the design or development of a new product. Despite the importance of the flexural strength, there are few works devoted to its study in the case of PA11-based composites. In this work, an in-depth study of the flexural strength of PA11 composites, reinforced with Stoneground wood (SGW) from softwood, is presented. Additionally, the results are compared with those of PP-based composites. The results showed that the SGW fibers had lower strengthening capacity reinforcing PA11 than PP. Moreover, the flexural strength of PA11-SGW composites was similar to that of PP-GF compositesPostprint (published version

Job satisfaction and motivation of public employees in Spain

Our purpose is to analyze job satisfaction and motivation of public employees in Spain to respond two questions. First, whether there is divergence between different public occupations and, second, what are the distinguishing features of that diversity? Using data from the Spanish Survey of Labor Conditions (ECVT, Encuesta de Condiciones y Vida en el Trabajo) 2006-2010, we estimate regressions for each of the 17 public occupations, with job satisfaction and motivation as the dependent variables, and a number of economic and socio-demographic determinants as exogenous variables. Our results, which can be considered contributions to the study of public management, reveal that the importance that public employees assign to the performance of their work, that is to say, to the idea of public service, is clearly a source of job satisfaction. These results do not fully support certain criticisms that require management philosophies to be closer to the private model, assuming that this can be more efficient for public employees

Generational Differences at Work in Spain

The purpose of this paper is to explore differentials in the job satisfaction and the organizational commitment of Baby Boomers and Generation X. In light of multiple age segments in the workforce, and the ageing population, human resource management strategies aimed at attracting, engaging, and retaining employees of all ages are of strategic importance. Through the use of the large-scale Quality of Life at Work, 2006-2010 survey (Spain), we have carried out an empirical approach that points to real and significant differences between these two generations, with respect to wages, leisure time, co-worker relationships, occupations, and human relationships. The findings of our study suggest that management will increasingly be required to take the generational diversity of the workforce into account. The value of this paper is to show several marked differences between generation groups in the labour market and, subsequently, it concludes by considering the implications of our results for work management both in theory and in practice

Generational Differences at Work in Spain

The purpose of this paper is to explore differentials in the job satisfaction and the organizational commitment of Baby Boomers and Generation X. In light of multiple age segments in the workforce, and the ageing population, human resource management strategies aimed at attracting, engaging, and retaining employees of all ages are of strategic importance. Through the use of the large-scale Quality of Life at Work, 2006-2010 survey (Spain), we have carried out an empirical approach that points to real and significant differences between these two generations, with respect to wages, leisure time, co-worker relationships, occupations, and human relationships. The findings of our study suggest that management will increasingly be required to take the generational diversity of the workforce into account. The value of this paper is to show several marked differences between generation groups in the labour market and, subsequently, it concludes by considering the implications of our results for work management both in theory and in practice

Job satisfaction and motivation of public employees in Spain

Our purpose is to analyze job satisfaction and motivation of public employees in Spain to respond two questions. First, whether there is divergence between different public occupations and, second, what are the distinguishing features of that diversity? Using data from the Spanish Survey of Labor Conditions (ECVT, Encuesta de Condiciones y Vida en el Trabajo) 2006-2010, we estimate regressions for each of the 17 public occupations, with job satisfaction and motivation as the dependent variables, and a number of economic and socio-demographic determinants as exogenous variables. Our results, which can be considered contributions to the study of public management, reveal that the importance that public employees assign to the performance of their work, that is to say, to the idea of public service, is clearly a source of job satisfaction. These results do not fully support certain criticisms that require management philosophies to be closer to the private model, assuming that this can be more efficient for public employees