An Efficient Approach to Reliability-based Topology Optimization for Continua under Material Uncertainty

This contribution presents a computationally efficient method for reliability-based topology optimization for continuum domains under material properties uncertainty. Material Young’s modulus is assumed to be lognormally distributed and correlated within the domain. The computational efficiency is achieved through estimating the response statistics with stochastic perturbation of second order, using these statistics to fit an appropriate distribution that follows the empirical distribution of the response, and employing an efficient gradient-based optimizer. Two widely-studied topology optimization problems are examined and the changes in the optimized topology is discussed for various levels of target reliability and correlation strength. Accuracy of the proposed algorithm is verified using Monte Carlo simulation

An Efficient Approach to Reliability-based Topology Optimization for Continua under Material Uncertainty

This contribution presents a computationally efficient method for reliability-based topology optimization for continuum domains under material properties uncertainty. Material Young’s modulus is assumed to be lognormally distributed and correlated within the domain. The computational efficiency is achieved through estimating the response statistics with stochastic perturbation of second order, using these statistics to fit an appropriate distribution that follows the empirical distribution of the response, and employing an efficient gradient-based optimizer. Two widely-studied topology optimization problems are examined and the changes in the optimized topology is discussed for various levels of target reliability and correlation strength. Accuracy of the proposed algorithm is verified using Monte Carlo simulation

Exploring the effects of pre-task planning time on EFL learners' narrative writing

The present study is carried out in order to provide deeper insights into the differential effects of pre-task planning time conditions on Iranian EFL learners' narrative writing production (accuracy, fluency, and complexity). To this end, three intact classes comprising 70 EFL language learners, studying in private language institutes in Iran, were randomly assigned to either no pre-task planning, 5 minute pre-task planning or 10 minute pre-task planning conditions. Analysis of the written narratives and the results of a series of one-way ANOVA revealed that both 5 minute and 10 minute pre-task planning groups showed substantial progress compared to those in the no pre-task planning group regarding the accuracy, fluency and complexity of their output. The obtained results support the view that providing pre-task planning opportunities leads task performers to produce the kind of output which displays improved complexity, accuracy, and fluency. The results also have some implications for teachers and practitioners in EFL contexts.El present estudi es va dur a terme amb la finalitat de proporcionar informació sobre els efectes del temps de planificació prèvia a la tasca en l'escriptura narrativa d'aprenents d'anglès com a llengua estrangera iranians (precisió, fluïdesa i complexitat). Amb aquest objectiu, 70 estudiants de tres classes d'instituts d'idiomes privats a l'Iran van ser assignats a l'atzar a grups sense temps de planificació, amb 5 minuts de planificació o amb 10 minuts de planificació. L'anàlisi de les narratives escrites i els resultats de les anàlisis ANOVA unidireccionals van revelar que els grups que van tenir 5 o 10 minuts de planificació prèvia a la tasca van mostrar un progrés substancial en comparació amb el grup sense temps de planificació quant a la precisió, fluïdesa i complexitat de la seva producció. Els resultats obtinguts suggereixen que proporcionar oportunitats de planificació prèvia a la tasca resulta en millor complexitat, precisió i fluïdesa. Els resultats també tenen algunes implicacions per al professorat.El presente estudio se llevó a cabo con el fin de proporcionar información sobre los efectos del tiempo de planificación previa a la tarea en la escritura narrativa de estudiantes de inglés como lengua extranjera iraníes (precisión, fluidez y complejidad). Con este objetivo, 70 estudiantes de tres clases de institutos de idiomas privados en Irán fueron asignadas al azar a grupos sin tiempo de planificación, con 5 minutos de planificación o con 10 minutos de planificación. El análisis de las narrativas escritas y los resultados de los análisis ANOVA unidireccionales revelaron que los grupos que tuvieron 5 o 10 minutos de planificación previa a la tarea mostraron un progreso sustancial en comparación con el grupo sin tiempo de planificación en cuanto a la precisión, fluidez y complejidad de su producción. Los resultados obtenidos sugieren que proporcionar oportunidades de planificación previa a la tarea resulta en mejor complejidad, precisión y fluidez. Los resultados también tienen algunas implicaciones para el profesorado.La présente étude a été réalisée afin de fournir des informations sur les effets du temps de planification préalable aux tâches sur l'écriture narrative des étudiants iraniens d'anglais langue seconde (précision, fluidité et complexité). À cette fin, 70 étudiants de trois classes des instituts de langue privés en Iran ont été assignés au hasard à des groupes sans temps de planification, 5 minutes de planification ou 10 minutes de planification. L'analyse des récits écrits et les résultats des analyses ANOVA unidirectionnelles ont révélé que les groupes qui avaient 5 ou 10 minutes de planification préalable aux tâches ont montré des progrès substantiels par rapport au groupe sans temps de planification en termes de précision, de fluidité et la complexité de sa production. Les résultats obtenus suggèrent que l'offre d'opportunités de planification pré-tâche se traduit par une meilleure complexité, précision et fluidité. Les résultats ont également des implications pour les enseignants

Roughness-Induced Vehicle Energy Dissipation: Statistical Analysis and Scaling

The energy dissipated in a vehicle suspension system due to road roughness affects rolling resistance and the resulting fuel consumption and greenhouse gas emission. The key parameters driving this dissipation mechanism are identified via dimensional analysis. A mechanistic model is proposed that relates vehicle dynamic properties and road roughness statistics to vehicle dissipated energy and thus fuel consumption. A scaling relationship between the dissipated energy and the most commonly used road roughness index, the International Roughness Index (IRI), is also established. It is shown that the dissipated energy scales with IRI squared and scaling of dissipation with vehicle speed V depends on road waviness number w in the form of V[superscript w−2]. The effect of marginal probability distribution of the road roughness profile on dissipated energy is examined. It is shown that although the marginal distribution of the road profile does not affect the identified scaling relationships, the multiplicative factor in these relationships does change from one distribution to another. As an example of practical application, the model is calibrated with the empirical HDM-4 model for different vehicle classes