Thermo-rheological-kinetical Study of Compression Molding of Fibre-reinforced Composites

International audienceTo improve the modeling of fiber reinforced composites, we present in this work numerical methods able to compute both fiber-reinforced composites deformation in squeeze flow and thermal-kinetic evolution. The rheology is given by an homogeneous orthotropic model for fiber composites which describes the anisotropy of the in-plane fiber. The thermics is then extended accounting for the reaction here formulated by the Bailleul's model. Both physics are related since the kinetic evolution as well as the temperature profile modify the rheology of the composites, giving raise to the thermo-rheological-kinetical coupling by means of the viscosity temperature dependence. A study case is presented, where the mold temperature is set to 150 • C with a composite sample at 40 • C. Thermal transfer begins as well as sample compression at constant speed. We present the evolution of the reaction, temperature and viscosity at the core and the surface. Reaction in the core of the material is much quicker than in the surface. Which means that a mapping of viscosity values is presented during the reaction modifying the mechanical response

Numerical study of turbulence models in the computation of blood flow in cannulas

In recent years, CFD has become an increasingly used tool in the design of blood-based devices. However, the estimation of red blood cells damage (hemolysis) remains a very important challenge due to the complex rheology of blood and the turbulence present in most pumping devices. The objective of this study was to identify an appropriate turbulence model suitable for predicting hemolysis in Hemodialysis cannula. Several modern turbulence models were evaluated in comparison to Direct Numerical Simulation (DNS), which was used as the gold standard. The fluid dynamics in the cannula was modeled as a coaxial jet in which Reynolds’ number approached 2800. Based on comparison of velocity and stress time-averaged profiles, the Shear Stress Transport (SST) model with Gamma-Theta transition was identified as an optimal compromise between accuracy and computational cost

Management Models in SMEs, Strategic Tool in Business Management

The business sector constitutes an engine for the Ecuadorian economy through the generation of employment and redistribution of wealth. Therefore, given the current economic dynamics of high competition, globalization of markets, and use of information and communication technologies, business managers need to use different tools such as management models to achieve acceptable levels of utility, profitability, customer satisfaction and permanence in the consumer market. This research involved an analysis of the impact on corporate management of applying different management models of Small and Medium Enterprises (SMEs) in the city of Riobamba, province of Chimborazo (Ecuador). The study was descriptive, cross-sectional, exploratory and non-experimental and it was conducted in the first half of 2019. Data were collected through field investigation and the application of a structured survey with a sample composed of 136 managers, owners and administrators, from a population of 440 entrepreneurs. The results showed that 93% of entrepreneurs knew about the existence of management models, and 41% recorded that total quality is the most applied model followed by continuous improvement (18%) and re-engineering (13%). We conclude that entrepreneurs consider management models to be crucial in the management of their company. Keywords: management model, business management, strategies, competitiveness, SMEs. Resumen El sector empresarial en todos sus niveles constituye un motor para la economía ecuatoriana, por la generación de empleo y redistribución de la riqueza; por ello los gerentes de las empresas dada la actual dinámica económica por la alta competencia, globalización de los mercados, uso de las tecnologías de información y comunicación, entre otras variables, necesita utilizar diferentes herramientas como son los modelos gerenciales para lograr niveles aceptables de utilidad, rentabilidad, satisfacción de los clientes y permanencia en el mercado consumidor. La investigación tiene como objetivo efectuar un análisis de la aplicación e incidencia en la gestión corporativa, de diferentes modelos gerenciales de las Pequeñas y Medianas empresas (Pymes) de la ciudad de Riobamba, provincia de Chimborazo (Ecuador). El estudio es descriptivo, transversal, exploratorio y no experimental efectuado en el primer semestre del año 2019, realizado mediante una investigación de campo, a través de la aplicación de una encuesta estructurada, seleccionando una muestra compuesta por 136 gerentes, propietarios y administradores, de una población de 440 empresarios. Los resultados obtenidos evidenciaron que el 93% de los empresarios conocen de la existencia de modelos gerenciales, el 41% registra que la calidad total es el modelo más aplicado seguido del mejoramiento continuo (18%) y Reingeniería (13%). Se concluye que los empresarios y emprendedores consideran a los modelos gerenciales de mucha importancia en la dirección de su empresa. Palabras clave: modelo gerencial, gestión empresarial, estrategias, competitividad, pymes

The Comparability of Men Who Have Sex With Men Recruited From Venue-Time-Space Sampling and Facebook: A Cohort Study

Background: Recruiting valid samples of men who have sex with men (MSM) is a key component of the US human immunodeficiency virus (HIV) surveillance and of research studies seeking to improve HIV prevention for MSM. Social media, such as Facebook, may present an opportunity to reach broad samples of MSM, but the extent to which those samples are comparable with men recruited from venue-based, time-space sampling (VBTS) is unknown. Objective: The objective of this study was to assess the comparability of MSM recruited via VBTS and Facebook. Methods: HIV-negative and HIV-positive black and white MSM were recruited from June 2010 to December 2012 using VBTS and Facebook in Atlanta, GA. We compared the self-reported venue attendance, demographic characteristics, sexual and risk behaviors, history of HIV-testing, and HIV and sexually transmitted infection (STI) prevalence between Facebook- and VTBS-recruited MSM overall and by race. Multivariate logistic and negative binomial models estimated age/race adjusted ratios. The Kaplan-Meier method was used to assess 24-month retention. Results: We recruited 803 MSM, of whom 110 (34/110, 30.9% black MSM, 76/110, 69.1% white MSM) were recruited via Facebook and 693 (420/693, 60.6% black MSM, 273/693, 39.4% white MSM) were recruited through VTBS. Facebook recruits had high rates of venue attendance in the previous month (26/34, 77% among black and 71/76, 93% among white MSM; between-race P=.01). MSM recruited on Facebook were generally older, with significant age differences among black MSM (P=.02), but not white MSM (P=.14). … See full text for complete abstract

Migration of contaminants from food packages to its content – Brazilian scenario and regulation

Consumers demand pleasant taste and odor in the final food product. Changes in these characteristics may be due to food deterioration or migration of substances from the packaging into food. The production of plastics for food containers involves catalysts which may contain toxic elements. In Brazil, there are limits of migratory substances and procedures for determining its rate. We aim to emphasize the food risks of migration of toxic substances from plastic packaging into its contents, and the Brazilian regulations regarding this issue. PET (polyethylene terephthalate) as raw matter for food packaging, is a concern in Brazil. The research methods currently adopted in Brazil are efficient for As, Cd, Co, Cr, and Sb determination. During PET synthesis and recycling, secondary reactions may form acetaldehyde, diethylene glycol and toxic oligomers. Monitoring by government mechanisms is essential to enforce safe food packaging. However, migration over the product shelf life remains an issue

O programa nacional de fortalecimento da agricultura familiar no Brasil: uma análise sobre a distribuição regional e setorial dos recursos.

No Brasil, as políticas públicas para o espaço rural sempre tenderam a priorizar a agricultura patronal, em detrimento dos agricultores familiares. Todavia, os estudos realizados pelos órgãos FAO - INCRA deram subsídio para a criação do Programa Nacional de Fortalecimento da Agricultura Familiar (PRONAF), resultando em um novo direcionamento dos investimentos públicos, os quais passaram a contemplar o segmento dos agricultores familiares. Entende-se o PRONAF como uma política não-compensatória, que, apesar de seus problemas, tem contribuído de fato para mudanças e melhorias no espaço agrário brasileiro. Desde sua criação no final da década de 1990, o PRONAF passou por várias mudanças em sua estrutura administrativa e operacional, a fim de alcançar seus objetivos e adequar-se face a complexa realidade social agrária brasileira. Sendo assim, o presente estudo visa discutir as ações do Estado por meio desse Programa, a partir de suas linhas de atuação, bem como analisar a distribuição de suas concessões de crédito regional e setorialmente. Assim, os procedimentos metodológicos utilizados para a realização deste trabalho compreendem pesquisa bibliográfica e documental, além de pesquisa em fontes secundárias, no intuito de obter dados e informações relevantes para a análise das relações sociais estabelecidas em meio a esse processo de concretização e espacialização desse Programa. Dentre as implicações do PRONAF pode-se notar em âmbito nacional, uma diminuição da disparidade regional brasileira, bem como a preocupação que o Programa tem demonstrado com os aspectos socioculturais locais e regionais, como forma de garantir que seus investimentos perpassem a dimensão econômica, mas valorize outras dimensões, a exemplo dos elementos culturais