Evaluation of Surface Residual Stresses in Friction Stir Welds Due to Laser and Shot Peening

The effects of laser, and shot peening on the residual stresses in Friction Stir Welds (FSW) has been investigated. The surface residual stresses were measured at five different locations across the weld in order to produce an adequate residual stress profile. The residual stresses before and after sectioning the coupon from the welded plate were also measured, and the effect of coupon size on the residual stress relaxation was determined and characterized. Measurements indicate that residual stresses were not uniform along the welded plate, and large variation in stress magnitude could be exhibited at various locations along the FSW plate. Sectioning resulted in significant residual stress relaxation in the longitudinal direction attributed to the large change in dimensions in this direction. Overall, Laser and shot peening resulted in a significant reduction in tensile residual stresses at the surface of the specimens

Formación del docente indígena wayuu para la alfabetización en contextos bilingües

La presente investigación tuvo como objetivo analizar la formación del docente intercultural bilingüe en su tarea de alfabetizador en los Centros de Educación Inicial (CEI) wayuu pertenecientes a la Parroquia Idelfonso Vásquez, Maracaibo, estado Zulia, en Venezuela. Los referentes teóricos consideraron el marco histórico y legal de la Educación Intercultural Bilingüe (EIB) en Venezuela como una modalidad del sistema escolar, así como las últimas tendencias de las investigaciones en materia de didáctica de la lectura y la escritura en lengua materna en contextos bilingües. Se trató de una investigación descriptiva, de campo y transeccional que utilizó la observación directa y no participativa de clases, el análisis de las planificaciones didácticas, la entrevista y el cuestionario semiestructurado. Los sujetos fueron 12 docentes indígenas de EIB que laboran en los CEI interculturales. Los resultados revelaron que la metodología de enseñanza del Wayuunaiki (L1) se basa en un modelo tradicional, con estrategias descontextualizadas, mecánicas y repetitivas, que impiden que los educandos wayuu utilicen ampliamente su lengua. El poco contacto con la lengua escrita de la L1 favorece el aprendizaje del castellano como L2 predominante. La formación del docente intercultural bilingüe es insuficiente para asumir la alfabetización de las nuevas generaciones desde la Educación Inicial, de una alfabetización que trascienda y que ayude a preservar la lengua a pesar de las fuertes presiones sociales. Sobre la base de los resultados y de los constructos teóricos analizados, se diseñó una propuesta de formación para el docente de EIB, que incluye a los docentes no indígenas como un aporte a la realidad educativa de la EIB en las instituciones educativas de la parroquia Idelfonso Vásquez, que puede ser extrapolable a otros centros educativos del estado Zulia.The following research was aimed at analyzing the formation of bilingual intercultural teachers in their task of teaching literacy skills at Wayuu early childhood education centers located in the Parish Ildefonso Vásquez, in Maracaibo, Zulia State, Venezuela. The theoretical framework considered the historical and legal support of Intercultural Bilingual Education (IBE) in Venezuela as a modality of the Venezuelan educational system as well as the latest trends in research on teaching reading and writing in native language in bilingual contexts. This was a descriptive, in-field and transectional research. Data was collected by means of direct and non-participant observations of classes, the analysis of lesson plans, interviews and a semi-structured questionnaire. The subjects were 12 indigenous teachers working at intercultural childhood education centers. Results revealed that the teaching methodology in Wayuunaiki (L1) is based on a traditional model which comprises the use decontextualized, mechanical and repetitive strategies that prevent Wayuu learners to communicate in their mother tongue. The few contact with L1 written language promotes the development of Spanish as L2. The bilingual intercultural teacher training is inadequate to assume literacy processes of future generations from early childhood education, one that transcends literacy and contributes to preserve the language despite the strong social pressures. Based on the results as well as on the theoretical background, a training proposal for the IBE teachers was designed, which includes non-indigenous teachers, as a contribution to educational reality of the Parish Idelfonso Vásquez, which is likely to be implemented in other educational institutions in Zulia state

A Solid-State Processing Approach to Enhance the Mechanical Performance of Polyolefins

This study aims to present and evaluate the use of solid-state processing for improving the mechanical properties of polyolefins. Isotactic polypropylene (i-PP) was selected to be studied due to its inferior mechanical properties in comparison to common plastics such as polyethylene (PET) and polyvinyl chloride (PVC). Recently, i-PP has garnered attention due to its attributes such as low-cost and recyclability. However, it requires additional processing to improve its mechanical performance. In this study, cryomilling was used to introduce various concentrations (0.2 - 1 wt. %) of diparamethyldibenzyldiene sorbitol (MDBS), as reinforcing agent, into the i-PP polymer. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to characterize the structural and thermal characteristics of the generated blends. Compression molding was utilized to fabricate thin films, and subsequently subjected to tensile testing using a universal testing machine. Results from DSC indicate the ability of cryomilling to generate a homogenous blend by indicating an increase in the crystallization temperature. Moreover, results from the tensile tests showed an increase in tensile strength. The improvements in the mechanical properties of polyolefins with the addition of sorbitol-derivatives can be attributed to the reduction in the average spherulite size of the polymer

Solid-State Processing Approach to Enhance the Mechanical Properties of Polypropylene

Agenda: Background; Research Problem; Methodology; Results and Discussion; Conclusions

Alphabetization in a Second Language at Wayuu Indigenous Schools in the State of Zulia: Curriculum, Educational Policies and Teaching Practice

El objetivo de la investigación fue analizar las políticas de alfabetización en castellano empleadas por las docentes de Educación Preescolar de la Parroquia Idelfonso Vásquez del Municipio Maracaibo, Estado Zulia. La investigación fue descriptiva-explicativa. Las técnicas de recolección fueron la entrevista y el análisis documental, siendo un cuestionario el instrumento utilizado. Dadas las características de la recogida de datos se optó por un análisis de la información cuali-cuantitativo. Se encontró que la alfabetización es predominantemente en castellano, con base en metodologías tradicionales. Los resultados indican que existe en los niños interés por la lengua escrita en castellano, pero presentan algunas dificultades de comunicación cuando la docente de aula desconoce la lengua materna. Se concluye que hace falta la ejecución efectiva de políticas de alfabetización cónsonas con el marco legal de la educación intercultural bilingüe y con los principios de una didáctica de la segunda lenguaThe aim of this research was to analyze Spanish literacy policies employed by pre-school teachers in the Idelfonso Vásquez Parish in Maracaibo, State of Zulia. The research was descriptive and explanatory; data collection techniques were the interview and documentary analysis. A questionnaire was used as the instrument. Information was analyzed from a quali-quantitative perspective. Analyses revealed that literacy takes place predominantly in Spanish, based on traditional methodologies. Results showed that children are interested in the written language in Spanish but have some communication difficulties when the classroom teacher does not know their mother tongue. The main conclusion is that there is a need for implementing effective literacy policies that comply both with the legal framework for intercultural bilingual education and with the principles of second language teaching

Use of Flexible Sensor to Characterize Biomechanics of Canine Skin

Background Suture materials and techniques are frequently evaluated in ex vivo studies by comparing tensile strengths. However, the direct measurement techniques to obtain the tensile forces in canine skin are not available, and, therefore, the conditions suture lines undergo is unknown. A soft elastomeric capacitor is used to monitor deformation in the skin over time by sensing strain. This sensor was applied to a sample of canine skin to evaluate its capacity to sense strain in the sample while loaded in a dynamic material testing machine. The measured strain of the sensor was compared with the strain measured by the dynamic testing machine. The sample of skin was evaluated with and without the sensor adhered. Results In this study, the soft elastomeric capacitor was able to measure strain and a correlation was made to stress using a modified Kelvin-Voigt model for the canine skin sample. The sensor significantly increases the stiffness of canine skin when applied which required the derivation of mechanical models for interpretation of the results. Conclusions Flexible sensors can be applied to canine skin to investigate the inherent biomechanical properties. These sensors need to be lightweight and highly elastic to avoid interference with the stress across a suture line. The sensor studied here serves as a prototype for future sensor development and has demonstrated that a lightweight highly elastic sensor is needed to decrease the effect on the sensor/skin construct. Further studies are required for biomechanical characterization of canine skin

Application of Bayesian Belief Network for Agile Kanban Backlog Estimation

What is Agile Kanban? Different from Kanban for JIT manufacturing! Visualization of workflow Limit work in process (WIP

Rheological, In Situ Printability and Cell Viability Analysis of Hydrogels for Muscle Tissue Regeneration

Advancements in additive manufacturing have made it possible to fabricate biologically relevant architectures from a wide variety of materials. Hydrogels have garnered increased attention for the fabrication of muscle tissue engineering constructs due to their resemblance to living tissue and ability to function as cell carriers. However, there is a lack of systematic approaches to screen bioinks based on their inherent properties, such as rheology, printability and cell viability. Furthermore, this study takes the critical first-step for connecting in-process sensor data with construct quality by studying the influence of printing parameters. Alginate-chitosan hydrogels were synthesized and subjected to a systematic rheological analysis. In situ print layer photography was utilized to identify the optimum printing parameters and also characterize the fabricated three-dimensional structures. Additionally, the scaffolds were seeded with C2C12 mouse myoblasts to test the suitability of the scaffolds for muscle tissue engineering. The results from the rheological analysis and print layer photography led to the development of a set of optimum processing conditions that produced a quality deposit while the cell viability tests indicated the suitability of the hydrogel for muscle tissue engineering applications