Powell–Sabin B‐splines and unstructured standard T‐splines for the solution of the Kirchhoff–Love plate theory exploiting Bézier extraction

The equations that govern Kirchhoff–Love plate theory are solved using quadratic Powell–Sabin B‐splines and unstructured standard T‐splines. Bézier extraction is exploited to make the formulation computationally efficient. Because quadratic Powell–Sabin B‐splines result in ‐continuous shape functions, they are of sufficiently high continuity to capture Kirchhoff–Love plate theory when cast in a weak form. Unlike non‐uniform rational B‐splines (NURBS), which are commonly used in isogeometric analysis, Powell–Sabin B‐splines do not necessarily capture the geometry exactly. However, the fact that they are defined on triangles instead of on quadrilaterals increases their flexibility in meshing and can make them competitive with respect to NURBS, as no bending strip method for joined NURBS patches is needed. This paper further illustrates how unstructured T‐splines can be modified such that they are ‐continuous around extraordinary points, and that the blending functions fulfil the partition of unity property. The performance of quadratic NURBS, unstructured T‐splines, Powell–Sabin B‐splines and NURBS‐to‐NURPS (non‐uniform rational Powell–Sabin B‐splines, which are obtained by a transformation from a NURBS patch) is compared in a study of a circular plate. Copyright © 2015 John Wiley & Sons, Ltd.     

Optimization of silicon solar cell fabrication based on neural network and genetic programming modeling

This study describes techniques for the cascade modeling and the optimization that are required to conduct the simulator-based process optimization of solar cell fabrication. Two modeling approaches, neural networks and genetic programming, are employed to model the crucial relation for the consecutively connected two processes in solar cell fabrication. One model (Model 1) is used to map the five inputs (time, amount of nitrogen and DI water in surface texturing and temperature and time in emitter diffusion) to the two outputs (reflectance and sheet resistance) of the first process. The other model (Model 2) is used to connect the two inputs (reflectance and sheet resistance) to the one output (efficiency) of the second process. After modeling of the two processes, genetic algorithms and particle swarm optimization were applied to search for the optimal recipe. In the first optimization stage, we searched for the optimal reflectance and sheet resistance that can provide the best efficiency in the fabrication process. The optimized reflectance and sheet resistance found by the particle swarm optimization were better than those found by the genetic algorithm. In the second optimization stage, the five input parameters were searched by using the reflectance and sheet resistance values obtained in the first stage. The found five variables such as the texturing time, amount of nitrogen, DI water, diffusion time, and temperature are used as a recipe for the solar cell fabrication. The amount of nitrogen, DI water, and diffusion time in the optimized recipes showed considerable differences according to the modeling approaches. More importantly, repeated applications of particle swarm optimization yielded process conditions with smaller variations, implying greater consistency in recipe generation.     

Application of partial mutual information variable selection to ANN forecasting of water quality in water distribution systems

Recent trends in the management of water supply have increased the need for modelling techniques that can provide reliable, efficient, and accurate representation of the complex, non-linear dynamics of water quality within water distribution systems. Statistical models based on artificial neural networks (ANNs) have been found to be highly suited to this application, and offer distinct advantages over more conventional modelling techniques. However, many practitioners utilise somewhat heuristic or ad hoc methods for input variable selection (IVS) during ANN development.This paper describes the application of a newly proposed non-linear IVS algorithm to the development of ANN models to forecast water quality within two water distribution systems. The intention is to reduce the need for arbitrary judgement and extensive trial-and-error during model development. The algorithm utilises the concept of partial mutual information (PMI) to select inputs based on the analysis of relationship strength between inputs and outputs, and between redundant inputs. In comparison with an existing approach, the ANN models developed using the IVS algorithm are found to provide optimal prediction with significantly greater parsimony. Furthermore, the results obtained from the IVS procedure are useful for developing additional insight into the important relationships that exist between water distribution system variables.     

Interferometer for cold neutrons

Design and setup of an interferometer for cold and ultracold neutrons are described. As neutron optical components three holographically produced gratings are arranged in triple Laue geometry. The gratings are adjusted during their recording process in photosensitized polymer slabs once for ever. Employing this device we measured the coherence function of a cold neutron beam by means of interferometry.     

The acculturation gap-distress hypothesis among high-risk Mexican American families.

The authors tested the acculturation gap-distress hypothesis by examining whether parent-adolescent acculturation gaps were associated with greater conflict and youth conduct problems among 260 high-risk Mexican American families. The authors operationalized acculturation gaps in 2 ways: parent-youth mismatches in acculturation style, and parent-youth discrepancies in acculturation toward both mainstream and heritage cultures. Acculturation gaps were common, but results of hierarchical regression analyses indicated that parent-youth discrepancies in acculturation toward mainstream and heritage cultures were not related to increased conflict or youth conduct problems. Conduct problems were no higher in families in which the adolescent was more aligned with mainstream culture than the parent. Unexpectedly, the authors found more youth conduct problems in families in which the youth was more aligned with traditional culture than the parent. The results call into question the assumption that the more rapid acculturation of adolescents to American culture inevitably leads to distress in minority families. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

基于谱分析的一类截尾二阶非线性模型盲辨识的方法(英)

提出一种基于自相关谱分析的对一类截尾Volterra非线性模型-二阶非线性模型进行盲辨识的算法．理论分析和计算机仿真均显示，该算法准确通用，适合于实际工程应用．     

Characterization of lead zirconate titanate (53/47) films fabricated by a simplified sol–gel acetic-acid route

Lead zirconate titanate [PZT (53/47)] films (around 200 nm thick) were prepared by the sol–gel acetic-acid route, spin-coating onto Si/SiO₂/Pt substrates. A simple thermal annealing program rendered complete crystallization to the perovskite phase and full removal of the organic material. The 53/47 film composition was attained in the bulk, however, X-ray photoelectron spectroscopy detected a different titanium/zirconium ratio at the film surface. Hysteresis loops were measured using a film-tester constructed at our laboratory. The single-annealed films showed a high resistive leakage. A second annealing cycle led to a better film densification and a marked reduction in surface roughness, significantly enhancing the ferroelectric response. Ferroelectric domains were mapped by piezoresponse force measurements. The relatively-simple experimental procedure applied allowed the fabrication of good quality ferroelectric films.     

Identifying Strategies to Support Junior Secondary Students to Engage in Scientific Investigation Tasks

Abstract

This article describes the outcome of a collaborative project between the Hong Kong Institute of Education and four secondary schools that aims to promote the development of scientific investigation skills. The project team designed scientific investigation tasks collaboratively with the teachers and provided school-based support when the tasks were implemented. A total of six teachers and 575 students were involved. Data were collected through questionnaires completed by the students and individual interviews with science teachers about their classroom practice after the completion of the project. The findings suggest that the students did not meet many difficulties and that there were positive influences on students’ interest in learning science. The teachers perceived that there were challenges related to raising students’ self-regulated learning abilities, structuring tasks that were at appropriate levels of difficulty, and promoting group cooperation among the students. Finally, the article argues that the strategies implemented in this study were effective, though it takes much time and effort to help students develop self-regulated learning abilities. The conclusion suggests that teachers consider these challenges collectively and proposes a two-staged model for planning scientific investigation tasks.