Creep rupture of viscoelastic fiber bundles

We study the creep rupture of bundles of viscoelastic fibers occurring under uniaxial constant tensile loading. A novel fiber bundle model is introduced which combines the viscoelastic constitutive behaviour and the strain controlled breaking of fibers. Analytical and numerical calculations showed that above a critical external load the deformation of the system monotonically increases in time resulting in global failure at a finite time $t_f$, while below the critical load the deformation tends to a constant value giving rise to an infinite lifetime. Our studies revealed that the nature of the transition between the two regimes, i.e. the behaviour of $t_f$ at the critical load $sigma_c$, strongly depends on the range of load sharing: for global load sharing $t_f$ has a power law divergence at $\sigma_c$ with a universal exponent of 0.5, however, for local load sharing the transition becomes abrupt: at the critical load $t_f$ jumps to a finite value, analogous to second and first order phase transitions, respectively. The acoustic response of the bundle during creep is also studied.Comment: 4 pages, 4 figures, APS style, submitted for publicatio

The indigenous languages as a factor of discrimination in two communities in the state of Guerrero

1 archivo PDF (22 páginas). fhundequinquagintaEl acelerado descenso de las lenguas indígenas en México reclama un detallado diagnóstico de tan preocupante situación. La persistencia de los prejuicios y la discriminación inhiben el uso de la lengua náhuatl en los hablantes bilingües de Guerrero, quienes adoptan una doble postura: defienden la lengua indígena y asumen los mismos prejuicios contra aquélla. Tales actitudes se identifican mediante diversas pruebas. Abstract The rapid decline of indigenous languages in Mexico demands a detailed diagnosis of critical situation. The persistence of prejudice and discrimination inhibit the use of the Nahuatl language in bilingual speakers of Guerrero, who adopt a dual approach, first , defend de indigenous language, on the other, assume the same prejudices against it . Such attitudes are identified by diferent tests. PALABRAS CLAVE: actitudes lingüísticas, náhuatl, español, prejuicios. KEY WORDS: Language, Nahuatl, Spanish attitudes, prejudices

Modeling particle-fluid interaction in a coupled CFD-DEM framework

In this work, we present an alternative methodology to solve the particle-fluid interaction in the resolved CFDEM coupling framework. This numerical approach consists of coupling a Discrete Element Method (DEM) with a Computational Fluid Dynamics (CFD) scheme, solving the motion of immersed particles in a fluid phase. As a novelty, our approach explicitly accounts for the body force acting on the fluid phase when computing the local momentum balance equations. Accordingly, we implement a fluid-particle interaction computing the buoyant and drag forces as a function of local shear strain and pressure gradient. As a benchmark, we study the Stokesian limit of a single particle. The validation is performed comparing our outcomes with the ones provided by a previous resolved methodology and the analytical prediction. In general, we find that the new implementation reproduces with very good accuracy the Stokesian dynamics. Complementarily, we study the settling terminal velocity of a sphere under confined conditions

Normas Internacionales de Información Financiera para Pequeñas y Medianas Empresas : Evaluación de la propiedad de planta y equipo de la empresa Buen Pan,S.A. para el periodo que finaliza el 31 e3 diciembre del 2015 según las normas internacionales de información financiera para pequeñas y medianas empresa (NIIF para Pymes)

Las Normas Internacionales de Información Financiera (NIIF) son estándares mundiales de presentación y adopción de materia contable. Las normas hoy en día constituyen un marco normativo de regulación y de presentación para los usuarios externos e internos que tienen la necesidad de interpretar dicha información. La sección 17 de las Normas Internacionales de Información Financiera (NIIF para PYMES) conocida como Propiedad, Planta y Equipo tiene una gran importancia dentro de la presentación de los Estados Financieros. Por lo que es de vital importancia poder tener el pleno conocimiento de dicha sección y aplicar en materia contable sus acápites. El brindar estados financieros en base a NIIF permitirá tener una mayor razonabilidad de la información adaptada a las exigencias mundiales, y poder optar a diferentes mercados

Determination of physical-mechanical characteristics in potatoes (Fianna variety) as parameters for mechanical design

Potatoes are one of the most important agricultural products due to their great nutritional and industrial value. However, the mechanization of this crop is low in many countries. The main aim of this investigation was to characterize the Fianna potato variety. The potatoes were characterized morphologically (polar diameter, equatorial diameter, thickness, geometric diameter, arithmetic diameter, sphericity, and weight), mechanically (static friction coefficient, rolling angle, and axial compression), and by impact and firmness tests. The sample potatoes were distributed into four groups (S1, S2, S3, and S4) according to their size. A random complete blocks design was used to determine the mean values of their characteristics. The results of the physical characteristics showed a higher coefficient of variation in the S1 group. All values tended to decrease except sphericity. The results of the mechanical tests show that the coefficient of static friction increases as the size of the potato decreases, while the relationship of the rolling angle was the opposite. The axial compression results showed values that decreased from Group S1 to Group S4 except for Young's modulus, which ranged from 1,306 to 3,697 MPa in the four groups. Determining these data is necessary because they represent design parameters useful for the development of mechanical equipment

Efl learner’s perspectives about the teaching - learning process of English as a foreign language (EFL) in online Education

This project analyzed the EFL Learners’ perspectives about English as a foreign language [EFL] teaching and learning in online education. The twenty-six EFL students belong to the sixth cycle of Pedagogy of National and Foreign Languages (English) career at the Technical University of Cotopaxi, which were randomly selected. Qualitative research was used initially to comprehend the problematic and a mixed methodology was applied, in which two phases of data collection were carried out. The quantitative phase applied an online survey using a Likert scale to obtain quantifiable data on the teaching-learning process of the English language in online education. For the qualitative part, semi-structured interviews with open-ended questions were used to gather information about the student’s perceptions and the factors that influence their learning of English in a virtual environment. Data analysis of the interview was performed by a bottom-up approach focused on coding, transcription, and subsequent division into three categories and six subcategories representing students’ views of the teaching-learning process in an online modality. On the other hand, for the analysis of the survey, the information was classified and related to the stated objective and the google forms tool was used to statistically extract the percentages for the analysis of results and discussion. Several factors interfere with the students’ language learning inside the online classroom such as methodologies employed, technological resources, level of communication, the time established for each activity, motivational factors. Thus, it is essential to apply artful methods, techniques and activities in the teaching-learning process, focusing on improving the learners’ language skills. The analysis of the interviews and the surveys provides guidelines for enhancing the use of the methods, learning platforms and resources in higher distance education regarding strengths and weaknesses of students. The beneficiaries will be the educational body since it will provide an informed approach of teaching English as a foreign language in a virtual classroom and the perspective of students regarding online learning.Este proyecto analizó las perspectivas de los estudiantes de EFL sobre la enseñanza y el aprendizaje del inglés como lengua extranjera [EFL] en la educación en línea. Los veintiséis estudiantes de EFL pertenecen al sexto ciclo de la carrera de Pedagogía en Lenguas Nacionales y Extranjeras (inglés) de la Universidad Técnica de Cotopaxi, fueron seleccionados aleatoriamente. La investigación cualitativa se utilizó para comprender la problemática y se aplicó una metodología mixta, se realizaron dos fases de recolección de datos. En la fase cuantitativa se aplicó una encuesta en línea utilizando una escala Likert para obtener datos cuantificables sobre el proceso de enseñanza-aprendizaje del idioma inglés en la educación en línea. Para la parte cualitativa se utilizaron entrevistas semiestructuradas con preguntas abiertas para recoger información sobre las percepciones de los alumnos y los factores que influyen en su aprendizaje del inglés en un entorno virtual. El análisis de los datos de la entrevista se realizó mediante un enfoque ascendente centrado en la codificación, transcripción y posterior división en tres categorías y seis subcategorías que representan las opiniones de los estudiantes sobre el proceso de enseñanza-aprendizaje en una modalidad online. Por otro lado, para el análisis de la encuesta, se clasificó la información y se relacionó con el objetivo planteado, se utilizó la herramienta de formularios de Google para extraer estadísticamente los porcentajes para el análisis de resultados y la discusión. Son varios los factores que interfieren en el aprendizaje de idiomas de los alumnos dentro del aula virtual como las metodologías empleadas, los recursos tecnológicos, el nivel de comunicación, el tiempo establecido para cada actividad, los factores motivacionales. Por lo tanto, es esencial aplicar métodos, técnicas y actividades ingeniosas en el proceso de enseñanza-aprendizaje, centrándose en la mejora de las habilidades lingüísticas de los alumnos. El análisis de las entrevistas y de las encuestas proporciona pautas para mejorar el uso de los métodos, las plataformas de aprendizaje y los recursos en la educación superior a distancia en relación con los puntos fuertes y débiles de los estudiantes. Los beneficiarios serán las entidades educativas porque proporcionará un enfoque informado de la enseñanza del inglés como lengua extranjera en un aula virtual y la perspectiva de los estudiantes con respecto al aprendizaje en línea

Discrete Fracture Model with Anisotropic Load Sharing

A two-dimensional fracture model where the interaction among elements is modeled by an anisotropic stress-transfer function is presented. The influence of anisotropy on the macroscopic properties of the samples is clarified, by interpolating between several limiting cases of load sharing. Furthermore, the critical stress and the distribution of failure avalanches are obtained numerically for different values of the anisotropy parameter $\alpha$ and as a function of the interaction exponent $\gamma$. From numerical results, one can certainly conclude that the anisotropy does not change the crossover point $\gamma_c=2$ in 2D. Hence, in the limit of infinite system size, the crossover value $\gamma_c=2$ between local and global load sharing is the same as the one obtained in the isotropic case. In the case of finite systems, however, for $\gamma\le2$, the global load sharing behavior is approached very slowly