High accuracy compact finite difference methods and their applications

Numerical si mulation of complex flow fields withmulti-scale structures is one of the most i mportant andchallenging branches of computational fluid dynamics .Fromlinear analysis and numerical experi ments it hasbeen discovered that the higher-order accurate methodcan give reliable and efficient computational results ,aswell as better resolution of the complex flow fieldswith multi-scale structures . Compact finite differenceschemes , which feature higher-order accuracy andspectral-like resolu…     

考虑剪切效应弹性板弯曲问题的DQ分析方法

A differential quadrature (DQ) method for orthotropic plates was proposed based on Reddy' s theory of plates with the effects of the higher-order transverse shear deformations. Wang-Bert's DQ approach was also further extended to handle the boundary conditions of plates. The computational convergence was studied, and the numerical results were obtained for different grid spacings and compared with the existing results. The results show that the DQ method is fairly reliable and effective.     

Study on absorption coefficients of dual-energy γ-rays in determining phase fractions of multiphase flows

INTRODUCTION The imaging and measurement of multiphase flows has received much attention in recent years, largely because of a need in the oil industry to measure the mass flow rates of oil, water and gas in production pipelines, and the ability to see through objects and make quantitative measurements of the enclosed ma- terials and structures has wide range of applications. However, measurement over a wide range of flow regimes and the ability to very accurately measure the mass flow rat…     

Digital Modeling and Visualization of Hydroelectric Engineering Geoinformation

To describe the spatial tendency and complex relationship of geological structures, a digital modeling based on geographic information system and the visualization of hydroelectric engineering geology information are presented. The functions of information visual query, spatial cutting, section drawing, and coupled analysis with hydraulic structures are realized. The geologic model can match the attribute data with the shape data of geological structures, and organize the information for spatial query and analysis of the 3D model. With an application in Laxiwa hydroelectric project on the upriver of Huanghe River, the method provides a 3D parallel section view and query results of geoinformation, and 3D section views of geoinformation along axis of spillway tunnel,and along the 5th axis with underground structures, respectively.     

Numerical simulation and optimization design of the EGR cooler in vehicle

The EGR （exhaust gas recirculation） technique can greatly reduce the NOx emission of diesel engines, especially when an EGR cooler is employed. Numerical simulations are applied to study the flow field and temperature distributions inside the EGR cooler. Three different models of EGR cooler are investigated, among which model A is a traditional one, and models B and C are improved by adding a helical baffle in the cooling area. In models B and C the entry directions of cooling water are different, which mostly influences the flow resistance. The results show that the improved structures not only lengthen the flow path of the cooling water, but also enhance the heat exchange rate between the cool and hot media. In conclusion we suggest that the improved structures are more powerful than the traditional one.     

CFD Simulation of Film Flow and Gas/Liquid Countercurrent Flow on Structured Packing

A mathematic model of two-phase flow and a physical model of two-dimensional (2D) vertical section for the plate-type structured packing Mellapak 250.Y were set up and verified. The models were used to study the influence of packing’s surface microstructure on the continuity of liquid film and the amount of liquid holdup. Simulation results show that the round corner shape and micro wavy structure are favorable in remaining the continuity of liquid film and increasing the amount of liquid holdup. The appropriate liquid flow rate was determined by investigating different liquid loadings to obtain an unbroken liquid film on the packing surface. The pressure difference between inlet and outlet for gas phase allowed gas and liquid to flow countercurrently in a 2D computational domain. The direction change of gas flow occurred near the phase interface area.     

Simulation and analysis of resin flow in injection machine screw

A method with simulation and analysis of the resin flow in a screw is presented to ease the control of some problems that may affect the efficiency and the quality of the product among existing screws in an injection machine. The physical model of a screw is established to represent the stress, the strain, the relationship between velocity and stress, and the temperature of the cells. In this paper, a working case is considered where the velocity and the temperature distributions at any section of the flow are obtained. The analysis of the computational results shows an ability to master various parameters depending on the specifications.     

Porous structures of natural materials and bionic design

INTRODUCTION After long period natural selections and evolu-tions,natural porous structures always integrate various functions and have many characters superior to artificial porous structures,which are mainly composed of composite and complex structures.Natural porous structures can prevent seeds,eggs,etc.from invasion of water or cracks due to collision,exchange matters with the environment during the metabolism process,and use less material to form larger space under equivalent conditio…     

Numerical study on viscosity reduction in mining heavy oil by circulating hot water

Viscosity reduction is an important process in mining heavy oil.To predict the temperature variation and viscosity variation of heavy oil in flow direction,computational fluid dynamics(CFD) was adopted to simulate the process of heat transfer and flow in this paper.Moreover,an objective function,namely viscosity reduction efficiency,was established to analyze the effect of viscosity reduction.The results indicate that circulating hot water can reduce viscosity significantly,and that the effect of viscosity reduction depends on the inlet temperature and inlet volumetric flow rate of hot water.There is a maximum temperature of heavy oil in flow direction.With the inlet volumetric flow rate of 2.0m3/h and the inlet temperatures of 60,℃,70,℃ and 80,℃,viscosity reduction efficiencies are 94.6%,96.7% and 97.3%,respectively.With the inlet temperature of 70,℃ and the volumetric flow rates of 1.5m3 /h,2.0 m3/h and 2.5m3/h,viscosity reduction efficiencies are 94.4%,96.7% and 97.2%,respectively.     

CFD Prediction of Mean Flow Field and Impeller Capacity for Pitched Blade Turbine

This work focused on exploring a computational fluid dynamics(CFD)method to predict the macromixing characteristics including the mean flow field and impeller capacity for a 45° down-pumping pitched blade turbine(PBT)in stirred tanks. Firstly, the three typical mean flow fields were investigated by virtue of three components of liquid velocity. Then the effects of impeller diameter(D)and off-bottom clearance(C)on both the mean flow field and three global macro-mixing parameters concerning impeller capacity were studied in detail. The changes of flow patterns with increasing C/D were predicted from these effects. The simulation results are consistent with the experimental results in published literature.     

差分精度对液压滑阀内流体数值解析的影响

：以液压控制系统中常用的滑阀为研究对象，通过对滑阀内流体流动的仿真计算，对本中采用的数值解析手法的差分方法、空间计算格子系等计算参数对计算结果的影响进行了分析和讨论。结果表明，上述计算参数对流场构造以及流量的计算结果影响相对较小。2种不同计算方法对滑阀轴向流体力的分析比较得出：作用在滑阀轴方向上的流体力对差分方法、空间计算格子系等计算参数非常敏感。如要得到较高精度的计算结果，采用压强和壁面切应力来直接计算流体力要比应用控制体内流体的动量守恒原理需要更密的计算格子系。这一结果有助于我们在进行流场数值计算时，根据不同的对象选取合适的解析手法和计算参数，节省计算时间，提高计算效率。     

求解瞬态Naiver-Stokes问题的一种稳定化方法

在压力投影及多尺度变分法的基础上,本文针对瞬态Naiver-Stokes问题提出一种新的稳定化方法,此方法采用非协调且不满足inf-sup条件的速度及压力有限元空间。文中的稳定化方法具备一些优势:能避免高阶微分的计算,数据结构与单元边界无关;只在好的尺度上增加离散的速度项,对高雷诺数的流体很有效;不增加计算成本。     

Conceptualizing and Assessing Higher-Order Thinking in Reading

Students engage in higher-order thinking as they read complex texts and perform complex reading-related tasks. However, the most consequential assessments, high-stakes tests, are currently limited in providing information about students’ higher-order thinking. In this article, we describe higher-order thinking in relation to reading. We provide a framework for understanding higher-order thinking in reading, in relation to relevant theories and research in reading, and standards and assessment initiatives. We conclude with the considerations in assessments of higher-order thinking in reading that can help teachers and students work toward attainment of the Common Core State Standards.     

Healing temperature of hybrid structures based on genetic algorithm

The healing temperature of suspen-dome with stacked arches(SDSA)and arch-supported single-layer lattice shell structures was investigated based on the genetic algorithm. The temperature field of arch under solar radiation was derived by FLUENT to investigate the influence of solar radiation on the determination of the healing temperature. Moreover, a multi-scale model was established to apply the complex temperature field under solar radiation. The change in the mechanical response of these two kinds of structures with the healing temperature was discussed. It can be concluded that solar radiation has great influence on the healing temperature, and the genetic algorithm can be effectively used in the optimization of the healing temperature for hybrid structures.     

Higher-Order Assessment in Gross Anatomy: A Comparison of Performance on Higher- Versus Lower-Order Anatomy Questions between Undergraduate and First-Year Medical Students

Gross anatomy is considered by many the backbone of medical education. While learning anatomy has a reputation of requiring mainly rote memorization, modern day anatomy education often involves instruction and assessment at cognitive levels that foster higher-order thinking. In many instances, these higher-order anatomical concepts are taught to graduate students in healthcare-related fields, such as medicine. At this level, students are expected to apply and analyze anatomical information since that is what will ultimately be expected of them as professionals. In contrast, undergraduate anatomy education is typically more introductory in nature and often takes place in the setting of a large-enrollment course that serves as a prerequisite for many health sciences degree programs. In this study, variables related to the assessment of higher-order concepts in clinical anatomy were compared between first-year medical students and undergraduate students enrolled in an upper-level human gross anatomy course. Results demonstrate that undergraduate students perform lower than medical students overall, but the degree of difference in how they perform on higher- versus lower-order questions is comparable. The most notable exception is on practical examinations, where undergraduate students tend to struggle more with applying and analyzing information. Exploration of additional variables provides insight into how the cognitive level being assessed affects the time it takes to answer a question and how different practical examination question types and formats influence student performance. Findings presented in this study have implications for designing anatomy courses and underscore the importance of blueprinting assessments.     

基于小波的曲线设计

小波分析多尺度特征可以替代B样条基,将多尺度特性带入到曲面之中.这样就可以将分辨率较高的曲面分解成小波系数组和分辨率较低的曲面.运用离散内积和非均匀B样条节点插入算法,根据整体光顺度,从曲面对应的最坏节点进行局部光顺,选择最坏节点的光顺区域,运用约束方程,在光顺界面边界基本不变的条件下,对细节部分迭代进行分解,控制误差.在光顺时又可以保持曲面的连续性.     

Comparison and Categorization in the Development of Relational Similarity

4 experiments investigated the development of children's ability to recognize perceptual relational commonalities such as symmetry or monotonicity. In Experiment 1, 6- and 8-year-olds were able to recognize higher-order relational similarity across different dimensions (e.g., size/saturation ) and across different polarities (e.g., increase/decrease ), whereas 4-year-olds could recognize higher-order relational matches only when they were supported by lower-order commonalities (e.g., size/size but not size/saturation matches). Further experiments tested how the processes of comparison and categorization affected 4-year-olds' ability to recognize relational similarity. The results of the experiments supported the hypothesis that comparison and categorization processes lead to changes in children's representations of relational structure, enabling them to recognize more abstract commonalities. A computational model lent further support to the claims.     

图像压缩中小波变换技术的研究

介绍了图像压缩的必要性及小波变换在时域、频域所具有的良好的局域化特性.它弥补了DCT的不足,它的多分辨分析变换特性与人眼的视觉特性非常接近,不但保持原图像在各种分辨率下的精细结构,而且便于和其它新兴图像编码方法相结合,成为当今研究的热点.文中在介绍小波变换的基本理论的基础上,讨论了基于小波分析的图像压缩方法的关键技术.     

The use of assessment in the development of higher-order thinking skills

Abstract

In an increasingly complex and specialised society, it is imperative that individuals think critically and creatively. This kind of thinking is also required to achieve the critical outcomes as stated in the Revised National Curriculum Statement for South Africa. It seems, however, that higher-order thinking is unlikely to occur unless learners are engaged in activities that deliberately promote this kind of thinking. They should also be guided on how to engage in these complex thinking tasks. The aim of this article is to reflect on the use of assessment to promote learners' higher-order thinking skills. The role of assessment has implications for the nature of teacher training programmes. If lecturers model the way assessment can be done to develop higher-order thinking skills, it is hoped that teachers will have little difficulty in adapting it to their unique classroom situations. Examples from language modules of an in-service teacher training programme are used to show how assessment can be implemented to help learners develop higher-order thinking skills within the framework of outcomes-based education and the Revised National Curriculum Statement.     

课堂教学情境下学科高阶思维的结构与发展规律——以语文学科为例

高阶思维发展“沉浸”在不同学科课堂教学情境中,呈现出具有学科思维特点和学科活动特征的内在结构与发展规律。文章以语文学科为例,基于思维结构、高阶思维结构等基本理论,结合对学科思维的深入剖析,建立了认知要素与情感要素协同作用、思维过程与思维品质动态发展的学科高阶思维结构模型;进而以模型为理论框架对学科课堂教学视频进行质性分析,挖掘课堂情境中高阶思维活动发生与发展的表现与特征,构建了以复杂问题解决过程为主线、体现思维活动阶段性特征、高阶思维内在要素协同发挥作用、高阶思维外在品质不同程度提升的学科高阶思维发展规律模型。以期为探析学科高阶思维结构与发展规律提供一种思路与方法,为高阶思维发展取向的学科课堂教学设计与实施提供理论依据。