巧设促优化——新课程背景下初中科学课堂作业的优化设计研究

作业作为教与学的交叉点,它既是学生学习知识、发展思维、培养能力的最常规的一项实践活动,又是学生在亲身实践中巩固知识、深化知识、形成技能的重要环节。随着新课程教学的深入推进,作为教学改革内容之一的作业,如何更好地为教学服务,日益被广大教师所重视。基于此,从科学作业中存在的问题入手,就如何优化科学课堂作业的设计,从巧妙设计自主型作业,设计实践型作业,设计创编型作业,设计生活化作业和设计交叉型作业五个维度进行实践探索,收到了不错的教学实效。

INTEGRATED DESIGN OF AN ELECTRIC POWERED UNMANNED AIR VEHICLE USING CONCURRENT SUBSPACE DESIGN

The concurrent subspace design (CSD) framework has been used to conduct a preliminary design optimization of an electric powered, unmanned air vehicle (EPUAV) operating at a low Reynolds number. A multidisciplinary system analysis that includes aerodynamics, weights, propulsion, performance and stability and control has been developed for this class of vehicles. The CSD framework employs artificial neural network based response surfaces to provide approximations to the design space. The EPUAV system includes 25 continuous and 4 discrete design variables. The CSD framework was able to identify feasible designs with significant weight reductions relative to any previously considered (i.e. initial database) designs. This was accomplished with a limited number of system analyses. The results also demonstrate the nature of this design framework adaptive to changes in design requirements.

GEOMETRIC DESIGN OF DEPLOYABLE/RETRACTABLE MAST

To simplify the complicated design process of deployable/retractable structures, a new design process is developed. The process is divided into three phases： the concept design phase, the model phase and the optimization phase. In each phase, different parameter targets have to be fulfilled. According to three phases, a deployable/retractable mast composed of four right triangle prism modules in the longitudinal direction is designed. It can be deployed and folded simultaneously by the linear movements of sleeve-joints. The deployable and retractable movement of the mast is analyzed and key joint forms are designed. Then bar diameters and joint forms are modified based on mast structural mechanics characteristics in the optimization phase. Finally a 1：1 scaled model mast is built to verify the design and the optimization. Analytical results show that the model mast has the advantages of simple locking mechanism, fewer types of joints and bars, so it can be easily manufactured.

Shape Optimal System for Linear Elastic Structures

An integrated system FSOP2D,including modules for the shape optimal modeling,structural analysis,sensitivity analysis,optimal method library and post- processing,is developed.By selecting fictitious loads as the design variables that has a linear relationship with the grid point locations and using design sensitivity analysis of the domain method,it is easier to solve the velocity field.In the course of optimal iterations,mesh distortion is kept to a minimum,sensitivity derivatives of object function,stress constraints and displacement constraints are derived.Computation of sensitivity analysis is achieved in the system.Two engineering examples are used to prove the system's effectiveness,the optimal results can successfully be obtained by lesser number of iterations.

Configuration Optimization of Two-Rail Sliders on Dynamic Characteristic

An optimal design methodology for the configuration of two rail slider was proposed to get better dynamic performance. The taper length, taper height and the rail width of the reading/writing head are considered as design variables. The complex geometry method is utilized as the search scheme in the optimization process. Optimization results show that the new slider has better dynamic characteristics and is more stable than the original designed slider. The optimization process also demonstrates that the optimum model and optimum method is effective.

A Method for Solving Computer-Aided Product Design Optimization Problem Based on Back Propagation Neural Network

Because of the powerful mapping ability, back propagation neural network (BP-NN) has been employed in computer-aided product design (CAPD) to establish the property prediction model. The backward problem in CAPD is to search for the appropriate structure or composition of the product with desired property, which is an optimization problem. In this paper, a global optimization method of using the a BB algorithm to solve the backward problem is presented. In particular, a convex lower bounding function is constructed for the objective function formulated with BP-NN model, and the calculation of the key parameter a is implemented by recurring to the interval Hessian matrix of the objective function. Two case studies involving the design of dopamine β-hydroxylase (DβH) inhibitors and linear low density polyethylene (LLDPE) nano composites are investigated using the proposed method.

A structural design of multilevel decomposition and domain mapping

An integrated optimization design was described using multilevel decomposition technique on the base of the parametric distribution and independent axiom at the stages of lower level. Based on Pareto optimum solution, the detailed parameters at lower level can be defined into the independent axiom. The suspension design was used as the simulation example. In an axiomatic design for the optimization design, the uncoupled and decoupled designs between functional requirements and design parameters are generally needed. But using the design sensitivity(or screening) of design parameters, the approximate uncoupled design is developed on behalf of the decoupled and coupled designs. Successive design parameters were applied to the suspension of torsion beam axle. The structural performance increases by 18%. The kinematic and compliance performance increases by 6% within the feasible ranges.

Application of the optimal Latin hypercube design and radial basis function network to collaborative optimization

Improving the efficiency of ship optimization is crucial for modem ship design. Compared with traditional methods, multidisciplinary design optimization （MDO） is a more promising approach. For this reason, Collaborative Optimization （CO） is discussed and analyzed in this paper. As one of the most frequently applied MDO methods, CO promotes autonomy of disciplines while providing a coordinating mechanism guaranteeing progress toward an optimum and maintaining interdisciplinary compatibility. However, there are some difficulties in applying the conventional CO method, such as difficulties in choosing an initial point and tremendous computational requirements. For the purpose of overcoming these problems, optimal Latin hypercube design and Radial basis function network were applied to CO. Optimal Latin hypercube design is a modified Latin Hypercube design. Radial basis function network approximates the optimization model, and is updated during the optimization process to improve accuracy. It is shown by examples that the computing efficiency and robustness of this CO method are higher than with the conventional CO method.

Robust design and optimization for autonomous PV-wind hybrid power systems

This study presents a robust design method for autonomous photovoltaic (PV)-wind hybrid power systems to obtain an optimum system configuration insensitive to design variable variations. This issue has been formulated as a constraint multi-objective optimization problem, which is solved by a multi-objective genetic algorithm, NSGA-II. Monte Carlo Simulation (MCS) method, combined with Latin Hypercube Sampling (LHS), is applied to evaluate the stochastic system performance. The potential of the proposed method has been demonstrated by a conceptual system design. A comparative study between the proposed robust method and the deterministic method presented in literature has been conducted. The results indicate that the proposed method can find a large mount of Pareto optimal system configurations with better compromising performance than the deterministic method. The trade-off information may be derived by a systematical comparison of these configurations. The proposed robust design method should be useful for hybrid power systems that require both optimality and robustness.

Research on virtual dynamic optimization design for NC machine tools

Virtual dynamic optimization design can avoid the repeated process from de-sign to trial-manufacture and test.The designer can analyze and optimize the productstructures in virtual visualization environment.The design cycle is shortened and the costis reduced.The paper analyzed the peculiarity of virtual optimization design,and put for-wards the thought and flow to implement virtual optimization design.The example to opti-mize the internal grinder was studied via establishing precise finite element model,modi-fying the layout of Stiffened Plates and designing parameters of the worktable,and usingthe technology of modal frequency revision and the technology of multiple tuned damper.The result of optimization design compared the new grinder with the original grinder showsthat the entire machine's first orders natural frequency is enhanced by 17%,and the re-sponse displacement of the grinding-head has dropped by 28% under the first order natu-ral frequency and by 41% under second order natural frequency.Finally,the dynamic per-formance of the internal grinder was optimized.

Series Design of Large-Scale NC Machine Tool

Product system design is a mature concept in western developed countries. It has been applied in war industry during the last century. However,up until now,functional combination is still the main method for product system de-sign in China. Therefore,in terms of a concept of product generation and product interaction we are in a weak position compared with the requirements of global markets. Today,the idea of serial product design has attracted much attention in the design field and the definition of product generation as well as its parameters has already become the standard in serial product designs. Although the design of a large-scale NC machine tool is complicated,it can be further optimized by the precise exercise of object design by placing the concept of platform establishment firmly into serial product de-sign. The essence of a serial product design has been demonstrated by the design process of a large-scale NC machine tool.

Optimization and Control of Extractive Distillation with Heat Integration for Separating Benzene/Cyclohexane Mixtures

In this work, the extractive distillation with heat integration process is extended to separate the pressure-insensitive benzene-cyclohexane azeotrope by using furfural as the entrainer. The optimal design of extractive distillation process is established to achieve minimum energy requirement using the multi-objective genetic algorithm, and the results show that energy saving for this heat integration process is 15.7%. Finally, the control design is performed to investigate the system's dynamic performance, and three control structures are studied. The pressure-compensated temperature control scheme is proposed based on the first two control structures, and the dynamic responses reveal that the feed disturbances in both flow rate and benzene composition can be mitigated well.

Development of Experimental Device for Compression Load Deflection of Car Door Seals

A new experimental device has been developed for analyzing compression load deflection of the door seal by using stereovision theory. Precision instruments of optical grating and force sensor are also integrated in this device. Force-displacement response characteristics of compression at varied speed can be controlled. Solid foundations for characteristic and structure as well as optimization design of the car door seal are elucidated.

Applications of Power Rail Track Program to Tracings of Brazilian Railways

In Brazil, the use of software and applications in railway geometric designs is rare. Currently, after the division and privatization of the national rail network, the concessionaires who assumed the administration, are investing in modernization, recovery and extension of this transport model to make it more efficient. The PIL （Program of Investment in Logistics） has generated growth of the sector in response to the amount of investments, greatly enhancing the load capacity and optimizing the geometric design, which would allow speed of 80 km/h. Based on this information, the objective of this research is to verify the software applications of Power Rail Track Program of Bentley Systems, Inc. for geometric designs in future deployments of railways in Brazil. This software is based on numerical calculations, including roller adjustment by the least squares method to calculate and choose the best alignments, and regression tools, to a fast and effectively optimization of various parameters of the geometry for a future or existing railway. Different variables that allow you to optimize the geometric design are analyzed, considering several optional alignments and complex restrictions present in geometric design, taking into account variables such as circular curves, transition, tangents and rays. The software regression tools include curvature diagrams identifying points and curves, tangent and spirals. The analysis results are presented quickly and points can be added or deleted from the regression analysis, providing improved tracing. The software also allows to detail the elements of the executive project of the railway line such as rails, joints, turning points, waypoints and others. The result of this study has shown that the application of the Power Rail Track Program generates significant cost savings in time and increases in productivity, providing greater opportunity to optimize the geometry and reducing geometric design costs.

Design optimization of a torpedo shell structure

An optimized methodology to design a more robust torpedo shell is proposed. The method has taken into account reliability requirements and controllable and uncontrollable factors such as geometry, load, material properties, manufacturing processes, installation, etc. as well as human and environmental factors. The result is a more realistic shell design. Our reliability optimization design model was developed based on sensitivity analysis. Details of the design model are given in this paper. An example of a torpedo shell design based on this model is given and demonstrates that the method produces designs that are more effective and reliable than traditional torpedo shell designs. This method can be used for other torpedo system designs.

Research and design of the main equipments and structure of Xiangjiaba shiplift

The type of pinion and rack vertical shiplifts has been developed in recent a couple of years in the construction of dams.But the design methods and methodologies have rarely been discussed in literature.The Xiangjiaba shiplift is the second shiplift of this type following the Three Gorges shiplift.Being aimed at the technological rationality of the design in synthetically considering security,economy and applicability,this paper presents the research results of some vital issues relating the design of the Xiangjiaba shiplift,including the determination of design water depth of ship chamber based on fluid numeral computation and physical model test,the optimum design of general layout of main equipments and the civil structure of the Xiangjiaba shiplift,the finite element method(FEM) analysis of stress,vibration modes and the buckling of ship chamber,antiseismic research and the design of structures and mechanisms of the shiplift and the optimum design of driving mechanisms.This research provides the theoretical basis for the design of the Xiangjiaba shiplift.The design principles and research methods are valuable for the design of the same type of shiplifts.

Development of two-axis control index table driven by direct drive motors

The stability and reliability of a tilting index table should be considered at the design stage. A design method for the lightweight and improvement of the stability of the structure in a tilting index table was proposed using a commercial analysis program, ANSYS Workbench 12, by analyzing the static-thermal characteristics of the developed high-accuracy tilting index table at its design stage. The results of the performed structural analysis show that the maximum stress is generated at the stock tail part. An optimum design for the stock tail part was carried out to reduce the maximum stress and deformation. Also, the design variables were determined by considering the support of the stock tail part for the C-axis body. In the comparison of the results before and after the optimization, the maximum deformation and stress are improved by 2.8% and 8%, respectively.

Structural Multi-objective Probabilistic Design for Six Sigma

Uncertainties in engineering design may lead to low reliable solutions that also exhibit high sensitivity to uncontrollable variations. In addition, there often exist several conflicting objectives and constraints in various design environments. In order to obtain solutions that are not only "multi-objectively" optimal, but also reliable and robust, a probabilistic optimization method was presented by integrating six sigma philosophy and multi-objective genetic algorithm. With this method, multi-objective genetic algorithm was adopted to obtain the global Pareto solutions, and six sigma method was used to improve the reliability and robustness of those optimal solutions. Two engineering design problems were provided as examples to illustrate the proposed method.

Toward Exhaustive Teaching of Relational Database Indexes

There are several indexing techniques that can optimize system performances. The choice of the right index type in a schema can improve the DB performances by up to 80%. Unfortunately the illustrations of the various techniques are scattered over a number of texts and manuals, and the courses for database designers are often somewhat incomplete. The present paper shows a didactical experience which tackles this kind of limitations. In particular, the authors have prepared a textbook that includes twenty-one different index formats; it discusses advantages and disadvantages of each indexing technique, and has been positively validated during advanced courses on relational database design.

A Case Study on Optimization of Urban Design Base on Wind Environment Simulation

Wind environment simulation of a commercial district in Baise city of Guangxi Province, China, is carried out in the design phase. The results are analyzed and based on the evaluation standard for greening building of China. The simulation method is discussed in detail, and some suggestions for wind environment optimization are put forward, which might be helpful for similar research.