Fundamental Issues Towards Unified Design Theory of Recycled and Natural Aggregate Concrete Components

In the past 20 years,recycled aggregate concrete(RAC),as a type of low-carbon concrete,has become a worldwide focus of research.However,the design methodology for RAC structural components remains a challenge.Consequently,demands for a unified design of natural aggregate concrete(NAC)and RAC components have been presented.Accordingly,this study analyses the necessity of a unified design theory and provides an in-depth demonstration of the strength determination,compressive constitutive relationship,and design method of concrete components.The coefficient of variation of RAC strength is found to be generally higher than that of NAC strength.The compressive and tensile strengths of RAC can be defined and determined using the same method as that used for NAC.The uniaxial compressive constitutive relationship between NAC and RAC has a unified mathematical expression.However,the elastic modulus of RAC decreases,and its brittleness exhibits an increasing trend compared with that of NAC.Finally,to unify the design formulae of RAC and NAC components for bearing capacity,modification factors for RAC components are proposed considering safety and reliability.Additionally,the feasibility of the proposed unified time-dependent design theory is demonstrated in terms of conceptual design and structural measures considering the effects of strength degradation and reinforcement corrosion.It is believed that this study enriches and develops the basic theory of concrete structures.

Design of new biomedical titanium alloy based on d-electron alloy design theory and JMatPro software

A new kind offl biomedical titanium alloy, Ti-35Nb-4Sn-6Mo-9Zr, composed of non-toxic elements Nb, Mo, Zr and Sn with lower elastic modulus and higher strength was designed based on d-electron alloy design theory and JMatPro software using orthogonal experiment. The microstructure and basic mechanical properties of designed alloy were investigated. The results show that the alloy is composed of single fl equiaxed grains after solution treatment at 800 ~C. Compared with Ti-6A1-4V, the mechanical properties of the designed alloy are more excellent： E=65 GPa, σb=834 MPa, σ0.2=802 MPa, and σ=11%, which is expected to become a promising new type implanted material. The research approach adopted can reduce the experimental time and cost effectively, and get the ideal experimental results.

Design Theory and Method of Complex Products:A Review

Design is a high-level and complex thinking activity of human beings,using existing knowledge and technology to solve problems and create new things.With the rise and development of intelligent manufacturing,design has increasingly reflected its importance in the product life cycle.Firstly,the concept and connotation of complex product design is expounded systematically,and the different types of design are discussed.The four schools of design theory are introduced,including universal design,axiomatic design,TRIZ and general design.Then the research status of complex product design is analyzed,such as innovative design,digital design,modular design,reliability optimization design,etc.Finally,three key scientific issues worthy of research in the future are indicated,and five research trends of“newer,better,smarter,faster,and greener”are summarized,aiming to provide references for the equipment design and manufacturing industry.

DIMENSIONAL DESIGN THEORY AND METHODOLOGY OF 6-DOF SCISSOR PARALLEL MANIPULATOR

Parallel manipulators have many advantages over serial manipulators in termsof high load/weight ratio, velocity, stiffness and precision. A dimensional design theory andmethodology of six degrees of freedom scissor parallel manipulator (SPM) is investigated. The SPMkinematics inverse equation is given. Based on the formulation of the local dexterity and thedefinition about the indexes of workspace incircle radius, the effects of the design parameters onthe dexterity and workspace are discussed. Moreover the incircle radius change ratio about workspaceare defined and used as the evaluated indicator to analyze the effects of the design parameters onthe performances. A dimensional design theory that could satisfy the requirement of dexterity andworkspace is proposed. The dimensional design theory and methodology can be of help in the design,trajectory planning and control of parallel manipulator.

Some Views on the Contribution of Design Theory to Engineering Education

This paper aims at presenting the organisation,the findings and the lessons learnt of a design casestudy workshop organized in the context of UB1-HIT joint master programme.After presenting the content and the evolution of this workshop over the years,findings and lessons learnt are discussed and final conclusions and perspectives are being proposed at the end of the paper.

Advances in design theories of high-speed railway ballastless tracks

The design theories of the ballastless track in the world are reviewed in comparison with the innovative research achievements of high-speed railway ballastless track in China.The calculation methods and parameters concerning train load,thermal effect,and foundation deformation of high-speed railway ballastless track,together with the structural design methods are summarized.Finally,some suggestions on the future work are provided.

Optimal design theories of tuned mass dampers with nonlinear viscous damping

Optimal design theory for linear tuned mass dampers （TMD） has been thoroughly investigated, but is still under development for nonlinear TMDs. In this paper, optimization procedures in the time domain are proposed for design of a TMD with nonlinear viscous damping. A dynamic analysis of a structure implemented with a nonlinear TMD is conducted first. Optimum design parameters for the nonlinear TMD are searched using an optimization method to minimize the performance index. The feasibility of the proposed optimization method is illustrated numerically by using the Taipei 101 structure implemented with TMD. The sensitivity analysis shows that the performance index is less sensitive to the damping coefficient than to the frequency ratio. Time history analysis is conducted using the Taipei 101 structure implemented with different TMDs under wind excitation. For both linear and nonlinear TMDs, the comfort requirements for building occupants are satisfied as long as the TMD is properly designed. It was found that as the damping exponent increases, the relative displacement of the TMD decreases but the damping force increases.

Robust optimization design on impeller of mixed-flow pump

To increase the robustness of the optimization solutions of the mixed-flow pump,the impeller was firstly indirectly parameterized based on the 2D blade design theory.Secondly,the robustness of the optimization solution was mathematically defined,and then calculated by Monte Carlo sampling method.Thirdly,the optimization on the mixed-flow pump′s impeller was decomposed into the optimal and robust sub-optimization problems,to maximize the pump head and efficiency and minimize the fluctuation degree of them under varying working conditions at the same time.Fourthly,using response surface model,a surrogate model was established between the optimization objectives and control variables of the shape of the impeller.Finally,based on a multi-objective genetic optimization algorithm,a two-loop iterative optimization process was designed to find the optimal solution with good robustness.Comparing the original and optimized pump,it is found that the internal flow field of the optimized pump has been improved under various operating conditions,the hydraulic performance has been improved consequently,and the range of high efficient zone has also been widened.Besides,with the changing of working conditions,the change trend of the hydraulic performance of the optimized pump becomes gentler,the flow field distribution is more uniform,and the influence degree of the varia-tion of working conditions decreases,and the operating stability of the pump is improved.It is concluded that the robust optimization method proposed in this paper is a reasonable way to optimize the mixed-flow pump,and provides references for optimization problems of other fluid machinery.

Robust Design Method for Adjustable Mechanisms

Most conventional robust design methods assume design solutions are fixed values. Using these methods, designers set each control factor to a fixed value to maximize the robustness of objective characteristics. However, fluctuations in the objective characteristic often exceed the allowable range in a design problem. Consequently, it is difficult to obtain sufficient robustness using conventional methods. This research defines adjustable control factors whose values can be adjusted within a given range to increase robustness and proposes a method to calculate robustness, including factors to adjust the objective characteristic and derive optimum ranges of the factors. The robustness index, which indicates the feasibility that the objective characteristic values are within the tolerance by the adjustment, is calculated by the Monte Carlo method, while the range of adjustable control factors is optimized using the Vector evaluated particle swarm optimization. Finally, an engineering example is presented to demonstrate the applicability of the proposed method.

Design theory and experimental investigation of the low frequency and high power rare earth magnetostrictive flextensional transducer (Ⅰ). Theoretical part

The energy relationships among all the elements, by which the magnetostrictive transducers are manufactured, in Finite Element Method (FEM) are analyzed, then the expres- sions of FEM dynamics equations and performances formulas for magnetostrictive transducers are derived. The vibrating modes of the class VII transducer and its shell vibration are calcu- lated theoretically and the results point out that there is a breathing mode and if the transducer works at this mode, the transducer will vibrate with a greater volume speed and source level.

General theory and design of microperforated-panel absorbers

A general theory of microperforated-panel absorbers is proposed on the basis of equhaleot circuits. The characterizing parameters of the absorber are its relative acoustic resistance γ, the diameter d of the perforations and the resonance frequency fo. The later two form the perforate constaot k = , which, together with γ, decides the structure and characteristics of the microperforated-panel absorber. The maximum value of the absorption band width △f/f0 is (4/π)tan-1(1＋γ), as k approaches zero, and it does not change much as far as k is less than 1, the cavity depth is nearly a quarter wavelength of the resonance frequency For large values of k, the absorption band narrows down significalltly and the cavity depth required becomes a small fraction of the wavelength. The general properties of the microperforated absorber are discussed.

Revolutionary Objects： Pure Forms and Disorder in Ivan Leonidov＇s Work

This paper analyzes compositional strategies of Russian avant-garde architecture from the 1920s and 1930s through the study of the work of Ivan Leonidov （1902-1959）, one of the leading and most prolific architects of this movement. In this study, Leonidov＇s work is located within its predominant architectural context, and his work is interpreted not only as a reaction against the domineering principles of classicism, but as an evolution and selective continuation of key concepts directly translated from architectural academism. The issues of the use of pure forms--a radical stance at odds with the commonly accepted morphologies of that era--associated with the principles of displaced symmetry, or disorder, are closely looked at and evaluated against both their architectural and political values within the context of post-revolutionary Russia. It is argued that the characteristic of weightlessness in his large-scale planning proposals is revelatory of a particular desire to invade space with political presence, thus demanding to reconsider the relation between space and architectural objects. Parallels are also drawn from French Revolutionary architecture, and from the work of Claude-Nicolas Ledoux in particular, whose search for purity and autonomy in architectural morphology preceded that of Soviet architecture. As Leonidov＇s legacy mainly consists of drawings of buildings that never got built, his influence can often be felt in the work of other architects which until today have drawn formal elements and compositional strategies from his relatively vast volume of un-built work.

Design theory and experimental investigation of the low frequency and high power rare earth magnetostrictive flextensional transducer (Ⅱ). Experimental part

Vibrating modes of the manufactured flextensional transducer and its shell are experimentally investigated. The result are consistent with the theoretical calculations. The acoustical performances for the transducer are measured: resonance frequency is 1.16 kHz in the underwater, bandwidth is 680 Hz, mechanical quality factor is 1.71, transmitting current response is 186.1 dB, electromechanical efficiency is 13.1%.

An Improved Data Exchange Method Between Pro/E and ADAMS

According to the question of how to transfer data between Pro/E and ADAMS correctly, the paper gives an improved importing solution, which combines the interface and the Standard Data Format（SDF） files. It settles the problems caused by improper geometry during the import conducted by the interface software. With the solution ,fea- ture points can be conveniently picked to build kinematic constraints are the preparation of the model will be simpli- fied. An example is given for the method, and corresponding simulations are conducted. The results of the simula- tions verify the validity of the solution.

REVERSE MODELING FOR CONIC BLENDING FEATURE

A novel method to extract conic blending feature in reverse engineering is presented. Different from the methods to recover constant and variable radius blends from unorganized points, it contains not only novel segmentation and feature recognition techniques, but also bias corrected technique to capture more reliable distribution of feature parameters along the spine curve. The segmentation depending on point classification separates the points in the conic blend region from the input point cloud. The available feature parameters of the cross-sectional curves are extracted with the processes of slicing point clouds with planes, conic curve fitting, and parameters estimation and compensation, The extracted parameters and its distribution laws are refined according to statistic theory such as regression analysis and hypothesis test. The proposed method can accurately capture the original design intentions and conveniently guide the reverse modeling process. Application examples are presented to verify the high precision and stability of the proposed method.

Jellyfish bio-inspired Fe@CNT@CuNC derived from ZIF-8 for cathodic oxygen reduction

Biomimetics provides guidance to design and synthesize advanced catalysts for oxygen reduction reaction in microbial fuel cells(MFCs).Herein,jellyfish-inspired Fe clusters on carbon nanotubes connected with CuNC(Fe@CNT@CuNC)were designed and prepared by using zeolitic imidazolate framework(ZIF)-8 precursors to imitate the organic texture and function of jellyfish.The antibacterial effect of Cu^(+)ions depressed the growth of cathode biofilm to ensure rapid mass transport.Fe clusters and CuNC connected by CNTs accelerated the electron transfer from Fe to CuNC.The optimization of oxygen adsorption was caused by electron redistribution between sites of Fe and Cu.Jellyfish-like catalysts achieved a half-wave potential of 0.86 V and onset potential of 0.95 V vs.reversible hydrogen electrode(RHE).MFCs gained the maximum power density of 1600 mW·m^(-2) after 500 h measurement.This work provides insights into the special design of advanced catalysts based on bio-inspiration and biomimetics.

Design theories and maintenance technologies of slab tracks for high-speed railways in China:a review

The durability and reliability of slab track structures are essential for the long-term safety and stable operation of high-speed railways.In order to provide a solid theoretical basis and technical reference for the advancement of high-speed railway quality,this paper comprehensively discusses design theories of slab track structures,service performance evolution and maintenance technologies,and reviews the innovation happening in the industry.On top of that,the damage evolution,fatigue features and durability of slab tracks,which are highly relevant to serviceability,are summarized,and the future research trend of slab track service behaviours is pointed out.In addition,this paper summarizes the rules of establishing standards for damage maintenance,typical solutions for repairing damage and methods of evaluating the maintenance outcomes that combine field tests and numerical simulations.It also envisions a future direction where advanced testing technologies would assist the evaluation of maintenance effects.

Concept and design of super junction devices

The super junction（SJ） has been recognized as the ＂milestone＂ of the power MOSFET, which is the most important innovation concept of the voltage-sustaining layer（VSL）. The basic structure of the SJ is a typical junction-type VSL（J-VSL） with the periodic N and P regions. However, the conventional VSL is a typical resistance-type VSL（R-VSL） with only an N or P region. It is a qualitative change of the VSL from the R-VSL to the JVSL, introducing the bulk depletion to increase the doping concentration and optimize the bulk electric field of the SJ. This paper firstly summarizes the development of the SJ, and then the optimization theory of the SJ is discussed for both the vertical and the lateral devices, including the non-full depletion mode, the minimum specific on-resistance optimization method and the equivalent substrate model. The SJ concept breaks the conventional＂silicon limit＂ relationship of R_（on）∝V_B^（2.5）, showing a quasi-linear relationship of R_（on）∝V_B^（1.03）.

Thermal performance analysis of non-uniform height rectangular fin based on constructal theory and entransy theory

A model of non-uniform height rectangular fin, in which the variation of base's thickness and width are taken into account, is established in this paper. The dimensionless maximum thermal resistance(DMTR) and the dimensionless equivalent thermal resistance(DETR) defined based on the entransy dissipation rate(EDR) are taken as performance evaluation indexes. According to constructal theory, the variations of the two indexes with the geometric parameters of the fin are analyzed by using a finite-volume computational fluid dynamics code, the effects of the fin-material fraction on the two indexes are analyzed. It is found that the two indexes decrease monotonically as the ratio between the front height and the back height of the fin increases subjected to the non-uniform height rectangular fin. When the model is reduced to the uniform height fin, the two indexes increase first and then decrease with increase in the ratio between the height of the fin and the fin space. The fin-material fraction has no effect on the change rule of the two indexes with the ratio between the height of the fin and the fin space. The sensitivity of the DETR to the geometric parameters of the fin is higher than that of the DMTR to the geometric parameters. The results obtained herein can provide some theoretical support for the thermal design of rectangular fins.

Recent developments in superjunction power devices

Superjunction(SJ)is one of the most innovative concepts in the field of power semiconductor devices and is often referred to as a"milestone"in power MOS.Its balanced charge field modulation mechanism breaks through the strong dependency between the doping concentration in the drift region and the breakdown voltage V_(B)in conventional devices.This results in a reduction of the trade-off relationship between specific on-resistance R_(on,sp)and V_(B)from the conventional R_(on,sp)∝V_(B)^(2.5)to R_(on,sp)∝W·V_(B)^(1.32),and even to R_(on,sp)∝W·V_(B)^(1.03).As the exponential term coefficient decreases,R_(on,sp)decreases with the cell width W,exhibiting a development pattern reminiscent of"Moore's Law".This paper provides an overview of the latest research developments in SJ power semiconductor devices.Firstly,it introduces the minimum specific on-resistance R_(on,min)theory of SJ devices,along with its combination with special effects like 3-D depletion and tunneling,discussing the development of R_(on,min)theory in the wide bandgap SJ field.Subsequently,it discusses the latest advancements in silicon-based and wide bandgap SJ power devices.Finally,it introduces the homogenization field(HOF)and high-K voltage-sustaining layers derived from the concept of SJ charge balance.SJ has made significant progress in device performance,reliability,and integration,and in the future,it will continue to evolve through deeper integration with different materials,processes,and packaging technologies,enhancing the overall performance of semiconductor power devices.