Suchergebnisse

La modelación y la simulación con agentes es una tercera vía de hacer ciencia, y su potencial no radica en la predicción, sino en la comprensión de procesos fundamentales de fenómenos complejos. ¿De qué forma la modelación y simulación computacional basada en agentes puede ayudar en ciencias sociales a estudiar fenómenos complejos? El supuesto es que permite estudiar mediante sociedades artificiales la emergencia de fenómenos, y establecer vínculos entre los supuestos teóricos y los hechos empíricos. Además, los modelos basados en agentes permiten estudiar comportamientos emergentes a nivel macro a partir de estudiar comportamientos micro –bottom up-. Al respecto, este documento tiene el objetivo de construir un inicial estado del arte en este tema. Los retos y problemas pendientes se ubican en la validación empírica, en este sentido la estimación estadística y el modelado acompañado son los principales enfoques.

Thanks to the recent changes in the Chilean regulations for education, external technical assistance (ATE) has evolved from previous government programmes to become an important element in the policy for school improvement. Since 2008, ATEs have been providing technical and pedagogical support to schools, financed with resources from the Preferential School Subsidy Law (SEP). These resources from SEP are handed to municipal and subsidised primary schools catering for vulnerable students as these schools commit with ambitious improvement goals, set by the Chilean Ministry of Education (MINEDUC) to be achieved through a four-year improvement plan. Although external assistance is not a new phenomenon in my country there are few studies on the subject, most of them focus on its impact in school effectiveness. Fewer have explored the relationship between external agents and schools, particularly with teachers and school leaders, as it is where the improvement process and change takes place. My research question addresses this issue and follows the experience of a project of external assistance to a municipal primary school. Through interviews and a questionnaire application I reviewed the perception of teachers, school leaders and external agents about this process, their roles and relationships. Issues of school autonomy, trustful and collaborative relationships and external agents' flexibility are featured as the most relevant things for the people involved in this project; also, limited time and resources, the school background and the external agents' expertise appear as the most complex issues in this experience. Finally, as a result of the analysis and discussion, I argue about the complex relationship between external agents and school staff, underpinned by several principles and practical orientations. Also, I argue that a view about schools empowered of their improvement plans is highly relevant to understand the influence of external assistance in the process of improvement and change.

El sistema educativo nacional en México contempla la educación básica, la educación media superior y la educación superior. El tema de interés en este documento es la importancia de la mediación escolar en el nivel medio superior conocido como bachillerato o preparatoria, este nivel prepara y forma a jóvenes estudiantes para el ingreso a la educación superior o universitaria. En ese tenor de formación a los estudiantes, es pertinente socializar las herramientas y técnicas de los mecanismos alternativos para la gestión y solución de conflictos en pro de una cultura de paz. La mediación escolar coadyuva al sistema educativo en la formación del estudiante toda vez que es una persona que está transitando a una edad adulta en el que adquiere mayor número de responsabilidades. Este tipo de mediación otorga a la comunidad estudiantil potencializar los espacios de convivencia reforzando el diálogo y comunicación con participación activa, plural y respeto.

<p>Realizou-se a análise do processo de atendimento nos caixas de um supermercado, por meio da simulação, comparando os resultados obtidos pela simulação com a Teoria das Filas. As variáveis de entrada foram coletadas no sistema real (tempos dos intervalos entre as chegadas sucessivas de clientes nas filas e os tempos de atendimento dos caixas), sendo ajustadas funções de distribuição de probabilidade por meio do teste de Kolmogorov-Smirnov ao nível de 15% de probabilidade. A simulação, quando comparada à Teoria das Filas, mostrou-se uma ferramenta com maior capacidade de representar a realidade, por considerar a variação aleatória dos dados de entrada com maior exatidão. O melhor cenário avaliado sugere a realização de treinamento dos funcionários dos caixas normais e a realocação de um atendente dos caixas normais do turno da manhã para o caixa rápido no turno da tarde, o que contribuiria para a minimização das filas e tempos de espera dos clientes. Os benefícios deste cenário implicam o aumento de eficiência no funcionamento do processo de atendimento, a maior satisfação dos clientes e o equilíbrio na taxa de utilização dos servidores.</p><p>Palavras-chave: Supermercado. Caixa de atendimento. Arena. Teoria das Filas.</p>

© 2014 Elsevier Ltd. Zygosaccharomyces rouxii is an osmophilic yeast responsible for a large amount of economic loss in high sugar food production. Statistical modelling techniques were used in the present study to assess the individual effects of different chemical preservatives (potassium sorbate, sodium benzoate, dimethyldicarbonate, vanillin, ferulic, p-coumaric and caffeic acids) to control the growth of a cocktail of five yeast strains belonging to this species and isolated from spoilt concentrated grape juices. None of the preservatives assayed were able to completely inhibit the Z. rouxii growth. However, the mathematical models obtained in a high sugar culture media showed that especially four preservatives (potassium sorbate, sodium benzoate, dimethyldicarbonate and vanillin) were the best options to control the growth of this microorganism, obtaining a maximum reduction on yeast growth of approximately 40%. On the contrary, p-coumaric and caffeic acids were the preservatives with the lower effects, which only showed a maximum growth reduction percentage of approximately 15%. Results obtained in this paper could be very useful for industry for a better control of this spoilage yeast in concentrated grape juice. ; This research was supported by the Technological ProjectMZASJ51007: Support for Regional Viticulture Development – INTA. The authors wish to kindly thank to Dra. Amparo Querol (IATA-CSIC) for her generous scientific advice. M.C. Rojo is a Doctoral student Fellow of CONICET. F.N. Arroyo-López wants to thank CSIC and Spanish government for his Ramón y Cajal postdoctoral research contract. ; Peer Reviewed

The effect of pH (1.7-3.2) and sugar concentration (64-68 °Brix) on the growth of Zygosaccharomyces rouxii MC9 using response surface methodology was studied. Experiments were carried out in concentrated grape juice inoculated with Z.rouxii at isothermal conditions (23°C) for 60 days. pH was the variable with the highest effect on growth parameters (potential maximum growth rate and lag phase duration), although the effect of sugar concentration were also significant. In a second experiment, the time for spoilage by this microorganism in concentrated grape juice was evaluated at isothermal (23°C) and non-isothermal conditions, in an effort to reproduce standard storage and overseas shipping temperature conditions, respectively. Results show that pH was again the environmental factor with the highest impact on delaying the spoilage of the product. Thereby, a pH value below 2.0 was enough to increase the shelf life of the product for more than 60 days in both isothermal and non-isothermal conditions. The information obtained in the present work could be used by producers and buyers to predict the growth and time for spoilage of Z.rouxii in concentrated grape juice. © 2013 Elsevier Ltd. ; This research was supported by the Technological Project MZASJ51007: Support for Regional Viticulture Development – INTA. The authors wish to thank to the concentrating grape juice industry for providing all the samples used in the present study. M.C. Rojo is a Doctoral student Fellow of CONICET. F.N. Arroyo-López wants to thank CSIC and Spanish government for his Ramón y Cajal postdoctoral research contract. ; Peer Reviewed