The design of optimal heterogeneous catalysts for N_(2)-to-NH_(3) conversion is often dictated by the scaling relations,which result in a volcano curve that poses a limit on the catalytic performance.Herein,we reveal ...The design of optimal heterogeneous catalysts for N_(2)-to-NH_(3) conversion is often dictated by the scaling relations,which result in a volcano curve that poses a limit on the catalytic performance.Herein,we reveal a bowl active site that can break the scaling relations,through investigating the catalytic mechanisms of N_(2)-to-NH_(3) conversion on the lanthanide intermetallic electride catalyst LaRuSi by first-principles modeling.This bowl active site,composed of four surface La cations and one subsurface Si atom rich in electrons,plays the key role in enabling efficient catalysis.With adaptive electrostatic and orbital interactions,the bowl active site promotes the adsorption and activation of N_(2) that delivers facile cleavage of N-N bond,while destabilizes the adsorptions of ^(*)NH_(x)(x=1,2,3)species,which facilitates the release of the final NH_(3) product.By comparison with other electride catalysts isostructural to LaRuSi,we confirm the breaking of scaling relations between the adsorptions of ^(*)NH_(x) species and that of^(*)N on the bowl active site.Thus,this bowl active site presents a design concept that breaks the scaling relations for highly efficient heterogeneous catalysis of N_(2)-to-NH_(3) conversion.展开更多
For effectively improving the overall performance of fire truck frame structure,and solving the complexity of previous methods in the frame optimization design process,the traditional grey relational grade ranking nee...For effectively improving the overall performance of fire truck frame structure,and solving the complexity of previous methods in the frame optimization design process,the traditional grey relational grade ranking needs to be improved.First,the first-order modal test was conducted to verify the validity of the initial frame model.Then,based on this model,a high-strength steel frame was designed to reduce deformation,maximum stress,and frame mass,and increase the fatigue life and the frequencies of the first bending modal and first torsional modal.Sixty groups of sample points were generated through Hammersley method.Subsequently,improved grey relational analysis with principal component analysis was proposed to realize the optimal design of the frame structure.Finally,the optimal combination of design parameters for the frame was obtained using the proposed method.Meanwhile,the optimized frame structure is found by comparing the models before and after optimization,and the mass is reduced by 14.8%.Moreover,the computational cost can be reduced by 135%when the proposed method is compared with the previous algorithm.Therefore,the proposed method can effectively improve the performance of the frame and improve the computational efficiency.展开更多
The article introduces a new method for three-dimensional reproduction of edentulous dental casts,and wax occlusion rims with jaw relation by using a commercial high-speed line laser scanner and reverse engineering so...The article introduces a new method for three-dimensional reproduction of edentulous dental casts,and wax occlusion rims with jaw relation by using a commercial high-speed line laser scanner and reverse engineering software and evaluates the method’s accuracy in vitro.The method comprises three main steps：（i）acquisition of the three-dimensional stereolithography data of maxillary and mandibular edentulous dental casts and wax occlusion rims;（ii）acquisition of the three-dimensional stereolithography data of jaw relations;and（iii）registration of these data with the reverse engineering software and completing reconstruction.To evaluate the accuracy of this method,dental casts and wax occlusion rims of 10 edentulous patients were used.The lengths of eight lines between common anatomic landmarks were measured directly on the casts and occlusion rims by using a vernier caliper and on the three-dimensional computerized images by using the software measurement tool.The direct data were considered as the true values.The paired-samples t-test was used for statistical analysis.The mean differences between the direct and the computerized measurements were mostly less than 0.04 mm and were not significant（P.0.05）.Statistical significance among 10 patients was assessed using one-way analysis of variance（P,0.05）.The result showed that the 10 patients were considered statistically no significant.Therefore,accurate three-dimensional reproduction of the edentulous dental casts,wax occlusion rims,and jaw relations was achieved.The proposed method enables the visualization of occlusion from different views and would help to meet the demand for the computer-aided design of removable complete dentures.展开更多
The theory of grey systems is a new technique for performing prediction, relational analysis and decision making in many areas. In this paper, the use of grey relational analysis for optimizing the square hole flangin...The theory of grey systems is a new technique for performing prediction, relational analysis and decision making in many areas. In this paper, the use of grey relational analysis for optimizing the square hole flanging process parameters with considerations of the multiple response (the average flanging height, regular flanging and maximum strain) is introduced. Various flanging parameters, such as the blank inner radius rb, blank inner width B0, are considered. An orthogonal array is used for the experimental design. Multiple response values are obtained using finite element analysis (FEA). Optimal process parameters are determined by the grey relational grade obtained from the grey relational analysis for multi-performance characteristics (flanging height, regular flanging and maximum strain). Analysis of variance (ANOVA) for the grey relational grade is implemented. The results showed good agreement with the experiment result. Grey relational analysis can be applied in multiple response optimi-zation designs.展开更多
An experimental study was undertaken to express the hardening Swift law according to friction stir welding （FSW） aluminum alloy 2017. Tensile tests of welded joints were run in accordance with face centered composit...An experimental study was undertaken to express the hardening Swift law according to friction stir welding （FSW） aluminum alloy 2017. Tensile tests of welded joints were run in accordance with face centered composite design. Two types of identified models based on least square method and response surface method were used to assess the contribution of FSW independent factors on the hardening parameters. These models were introduced into finite-element code ＂Abaqus＂ to simulate tensile tests of welded joints. The relative average deviation criterion, between the experimental data and the numerical simulations of tension-elongation of tensile tests, shows good agreement between the experimental results and the predicted hardening models. These results can be used to perform multi-criteria optimization for carrying out specific welds or conducting numerical simulation of plastic deformation of forming process of FSW parts such as hydroforming, bending and forging.展开更多
Selection of air conditioning（AC） cold/heat sources generally concerns about certain aspects and cannot reveal the whole profile of the problems. Grey relation analysis （GRA） is a data processing method to categor...Selection of air conditioning（AC） cold/heat sources generally concerns about certain aspects and cannot reveal the whole profile of the problems. Grey relation analysis （GRA） is a data processing method to categorize the correlation extent of compared sequences and a certain reference sequence in a system with uncertain information. It is applied to evaluating and selecting AC cold/heat sources from four main aspects, which are technology, economy, reliability, and operation and management. Case study shows that the result for selecting AC cold/heat sources with the GRA method can be more reasonable and convincible. Thus it offers a new approach for designers in heating, ventilating and air conditioning field to compare and evaluate different AC cold/heat sou rces.展开更多
Experimentally, the best design gives estimates of the desired effects and contrasts with maximum precision. Efficiency as a discriminating factor enables comparison of designs. The goal of Response Surface Methodolog...Experimentally, the best design gives estimates of the desired effects and contrasts with maximum precision. Efficiency as a discriminating factor enables comparison of designs. The goal of Response Surface Methodology (RSM) is the determination of the best settings of the in-put variables for a maximum (or a minimum) response within a region of interest, R. This calls for fitting a model that adequately represents the mean response since such a model, is then used to locate the optimum. D-, A-, E- and T-Optimal designs of a rotatable design of degree two in four dimensions constructed using balanced incomplete block designs (BIBD) when the number of replications is less than three times the number of pairs of treatments occur together in the design and their relative efficiencies to general designs are presented. D-optimal design had 88 runs after replicating the factorial part twice and the axial part thrice with an optimal variance of 0.6965612 giving an efficiency of 97.7% while for A- and T-optimal designs they are formed with 112 runs each obtained by replicating the factorial part two times and axial part six times. Their optimal variances are 0.05798174 and 1.29828 respectively, with efficiency of 71.8% for A-optimal and 87.5% for T-optimal design. E-optimal design was found to be the most efficient design with an only 32 runs comprising only of the factorial part and with an optimal variance of 0.4182000, attaining an efficiency of approximately 1%. This study proposes the adoption of the E-optimal design in estimating the parameters of a rotatable second-order degree model constructed using BIBD for less costs and time saving.展开更多
This paper investigates the configuration design associated with boundary-constrained swarm flying.An analytic swarm configuration is identified to ensure the passive safety between each pair of spacecraft in the radi...This paper investigates the configuration design associated with boundary-constrained swarm flying.An analytic swarm configuration is identified to ensure the passive safety between each pair of spacecraft in the radial-cross-track plane.For the first time,this work derives the explicit configurable spacecraft amount to clarify the configuration's accommodation capacity while considering the maximum inter-spacecraft separation constraint.For larger-scale design problem that involves hundreds of spacecraft,this paper proposes an optimization framework that integrates a Relative Orbit Element(ROE)affine transformation operation and successional convex optimization.The framework establishes a multi-subcluster swarm structure,allowing decoupling the maintenance issues of each subcluster.Compared with previous design methods,it ensures that the computational cost for constraints verification only scales linearly with the swarm size,while also preserving the configuration optimization capacities.Numerical simulations demonstrate that the proposed analytic configuration strictly meets the design constraints.It is also shown that the proposed framework reduces the handled constraint amount by two orders compared with direct optimization,while achieving a remarkable swarm safety enhancement based on the existing analytic configuration.展开更多
In order to propose a seismic design spectrum that includes the effect of rupture directivity in the near-fault region, this study investigates the application of equivalent pulses to the parameter attenuation relatio...In order to propose a seismic design spectrum that includes the effect of rupture directivity in the near-fault region, this study investigates the application of equivalent pulses to the parameter attenuation relationships developed for near-fault, forward-directivity motions. Near-fault ground motions are represented by equivalent pulses with different waveforms defined by a small number of parameters （peak acceleration, A, and velocity V; and pulse period, Tv）. Dimensionless ratios between these parameters （e.g., ATv/V, VTv/D） and response spectral shapes and amplitudes are examined for different pulses to gain insight on their dependence on basic pulse waveforms. Ratios of ATv/V, VTv/D, and the ratio of pulse period to the period for peak spectral velocity （Tv-p） are utilized to quantify the difference between rock and soil sites for near-fault forward-directivity ground motions. The ATv/Vratio of recorded near-fault motions is substantially larger for rock sites than that for soil sites, while Tvp/Tv ratios are smaller at rock sites than at soil sites. Furthermore, using simple pulses and available predictive relationships for the pulse parameters, a preliminary model for the design acceleration response spectra for the near-fault region that includes the dependence on magnitude, rupture distance, and local site conditions are developed.展开更多
Performance of the proton exchange membrane fuel cell(PEMFC)is appreciably affected by the channel geometry.The branching structure of a plant leaf and human lung is an efficient network to distribute the nutrients in...Performance of the proton exchange membrane fuel cell(PEMFC)is appreciably affected by the channel geometry.The branching structure of a plant leaf and human lung is an efficient network to distribute the nutrients in the respective systems.The same nutrient transport system can be mimicked in the flow channel design of a PEMFC,to aid even reactant distribution and better water management.In this work,the effect of bio-inspired flow field designs such as lung and leaf channel design bipolar plates,on the performance of a PEMFC was examined experimentally at various operating conditions.A PEMFC of 49 cm2 area,with a Nafion 212 membrane with a 40%catalyst loading of 0.4 mg·cm-2 on the anode side and also 0.6 mg·cm-2 on the cathode side is assembled by incorporating the bio-inspired channel bipolar plate,and was tested on a programmable fuel-cell test station.The impact of the working parameters like reactants’relative humidity(RH),back pressure and fuel cell temperature on the performance of the fuel cell was examined;the operating pressure remains constant at 0.1 MPa.It was observed that the best performance was attained at a back pressure of 0.3 MPa,75°C operating temperature and 100%RH.The three flow channels were also compared at different operating pressures ranging from 0.1 MPa to 0.3 MPa,and the other parameters such as operating temperature,RH and back pressure were set as 75°C,100%and 0.3 MPa.The experimental outcomes of the PEMFC with bio-inspired channels were compared with the experimental results of a conventional triple serpentine flow field.It was observed that among the different flow channel designs considered,the leaf channel design gives the best output in terms of power density.Further,the experimental results of the leaf channel design were compared with those of the interdigitated leaf channel design.The PEMFC with the interdigitated leaf channel design was found to generate 6.72%more power density than the non-interdigitated leaf channel design.The fuel cell with interdigitated leaf channel design generated5.58%more net power density than the fuel cell with non-interdigitated leaf channel design after considering the parasitic losses.展开更多
In-vessel components are important parts of the EAST superconducting tokamak. They include the plasma facing components, passive plates, cryo-pumps, in-vessel coils, etc. The structural design, analysis and related R...In-vessel components are important parts of the EAST superconducting tokamak. They include the plasma facing components, passive plates, cryo-pumps, in-vessel coils, etc. The structural design, analysis and related R＆D have been completed. The divertor is designed in an up-down symmetric configuration to accommodate both double null and single null plasma operation. Passive plates are used for plasma movement control. In-vessel coils are used for the active control of plasma vertical movements. Each cryo-pump can provide an approximately 45 m^3/s pumping rate at a pressure of 10^-1 Pa for particle exhaust. Analysis shows that, when a plasma current of 1 MA disrupts in 3 ms, the EM loads caused by the eddy current and the halo current in a vertical displacement event （VDE） will not generate an unacceptable stress on the divertor structure. The bolted divertor thermal structure with an active cooling system can sustain a load of 2 MW/m^2 up to a 60 s operation if the plasma facing surface temperature is limited to 1500 ℃. Thermal testing and structural optimization testing were conducted to demonstrate the analysis results.展开更多
This paper presents a methodology for constructing seismic design spectra in near-fault regions. By analyzing the characteristics of near-fault pulse-type ground motions, an equivalent pulse model is proposed, which c...This paper presents a methodology for constructing seismic design spectra in near-fault regions. By analyzing the characteristics of near-fault pulse-type ground motions, an equivalent pulse model is proposed, which can well represent the characteristics of the near-fault forward-directivity and fling-step pulse-type ground motions. The normalized horizontal seismic design spectra for near-fault regions are presented using recorded near-fault pulse-type ground motions and equivalent pulse-type ground motions, which are derived based on the equivalent pulse model coupled with ground motion parameter attenuation relations. The normalized vertical seismic design spectra for near-fault regions are obtained by scaling the corresponding horizontal spectra with the vertical-to-horizontal acceleration spectral ratios of near-fault pulse-type ground motions. The proposed seismic design spectra appear to have relatively small dispersion in a statistical sense. The seismic design spectra for both horizontal and vertical directions can provide alternative spectral shapes for seismic design codes.展开更多
The identification of design pattern instances is important for program understanding and software maintenance. Aiming at the mining of design patterns in existing systems, this paper proposes a subgraph isomorphism a...The identification of design pattern instances is important for program understanding and software maintenance. Aiming at the mining of design patterns in existing systems, this paper proposes a subgraph isomorphism approach to discover several design patterns in a legacy system at a time. The attributed relational graph is used to describe design patterns and legacy systems. The sub-graph isomorphism approach consists of decomposition and composition process. During the decomposition process, graphs corresponding to the design patterns are decomposed into sub-graphs, some of which are graphs corresponding to the elemental design patterns. The composition process tries to get sub-graph isomorphism of the matched graph if sub-graph isomorphism of each subgraph is obtained. Due to the common structures between design patterns, the proposed approach can reduce the matching times of entities and relations. Compared with the existing methods, the proposed algorithm is not linearly dependent on the number of design pattern graphs. Key words design pattern mining - attributed relational graph - subgraph isomorphism CLC number TP 311.5 Foundation item: Supported by the National Natural Science Foundation of China (60273075) and the Science Foundation of Naval University of Engineering (HGDJJ03019)Biography: LI Qing-hua (1940-), male, Professor, research direction: parallel computing.展开更多
In the course of network supported collaborative design, the data processing plays a very vital role. Much effort has been spent in this area, and many kinds of approaches have been proposed. Based on the correlative ...In the course of network supported collaborative design, the data processing plays a very vital role. Much effort has been spent in this area, and many kinds of approaches have been proposed. Based on the correlative materials, this paper presents extensible markup language （XML） based strategy for several important problems of data processing in network supported collaborative design, such as the representation of standard for the exchange of product model data （STEP） with XML in the product information expression and the management of XML documents using relational database. The paper gives a detailed exposition on how to clarify the mapping between XML structure and the relationship database structure and how XML-QL queries can be translated into structured query language （SQL） queries. Finally, the structure of data processing system based on XML is presented.展开更多
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.Conseque...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.展开更多
The acquisition of valuable design knowledge from massive fragmentary data is challenging for designers in conceptual product design.This study proposes a novel method for acquiring design knowledge by combining deep ...The acquisition of valuable design knowledge from massive fragmentary data is challenging for designers in conceptual product design.This study proposes a novel method for acquiring design knowledge by combining deep learning with knowledge graph.Specifically,the design knowledge acquisition method utilises the knowledge extraction model to extract design-related entities and relations from fragmentary data,and further constructs the knowledge graph to support design knowledge acquisition for conceptual product design.Moreover,the knowledge extraction model introduces ALBERT to solve memory limitation and communication overhead in the entity extraction module,and uses multi-granularity information to overcome segmentation errors and polysemy ambiguity in the relation extraction module.Experimental comparison verified the effectiveness and accuracy of the proposed knowledge extraction model.The case study demonstrated the feasibility of the knowledge graph construction with real fragmentary porcelain data and showed the capability to provide designers with interconnected and visualised design knowledge.展开更多
The influence of KOH concentration (8 and 12 M) and curing conditions as temperature (40℃ and 60℃), time (7 and 28 days) and relative humidity (85% and 95% RH), on compressive strength of metakaolin-based geopolymer...The influence of KOH concentration (8 and 12 M) and curing conditions as temperature (40℃ and 60℃), time (7 and 28 days) and relative humidity (85% and 95% RH), on compressive strength of metakaolin-based geopolymers (MK-based GP) was evaluated. Derived from the experimental design technique, and using a factorial design 2<sup>K</sup> with two replications in the center point, eighteen experiments were conducted. The results reveal that the best performance conditions of geopolymerization to develop a higher compressive strength of 20 MPa are 12 M KOH to 60℃ and 85% RH at 28 curing days. With these conditions, the value of relative humidity of 85%, promotes high strength compact samples, and a maximum of 42 MPa at 90 days. The results of significant, compressive design of GP showed that KOH concentration and curing relative humidity were the most important factors, followed by curing time and temperature. The GP were characterized by XRD, and their evolution on compression strength was followed by SEM.展开更多
Spacecraft formation flying is an attractive new concept in international aeronautic fields because of its powerful functions and low cost. In this paper, the formation design and PD closed-loop control of spacecraft ...Spacecraft formation flying is an attractive new concept in international aeronautic fields because of its powerful functions and low cost. In this paper, the formation design and PD closed-loop control of spacecraft formation flying in elliptical orbits are discussed. Based on two-body relative dynamics, the true anomaly is applied as independent variable instead of the variable of time. Since the apogee is considered as the starting point, the six integrating constants are calculated. Therefore, the algebraic solution is obtained for the relative motion in elliptical orbits. Moreover, the formation design is presented and both circular formation and line formation are provided in terms of an algebraic solution. This paper also discusses the PD-closed loop control for precise formation control in elliptical orbits. In this part, the error-type state equation is put forward and the linear quadratic regulator （LQR） method is used to calculate PD parameters. Though the gain matrix calculated from LQR is time-variable because the error-type state equation is time variable, the PD parameters are also considered as constants because of their small changes in simulation. Finally, taking circular formation as an example, the initial orbital elements are achieved for three secondary spacecraft. And the numerical simulation is analyzed under PD formation control with initial errors and J2 perturbation. The simulation results demonstrate the validity of PD closed-loop control scheme.展开更多
This study integrated instrumental and relational approaches to the teaching and learning of solids in a preservice teacher＇s class. The researcher guided the preservice teachers to gather various prisms, pyramids, a...This study integrated instrumental and relational approaches to the teaching and learning of solids in a preservice teacher＇s class. The researcher guided the preservice teachers to gather various prisms, pyramids, and spheres to study the total surface areas and volumes. At the end of the integrated models, the test scores showed closed relationships in the concurrent instructional strategies of the integrated models. The researcher therefore, recommended the design models for the teaching and learning of solids in mathematics.展开更多
文摘The design of optimal heterogeneous catalysts for N_(2)-to-NH_(3) conversion is often dictated by the scaling relations,which result in a volcano curve that poses a limit on the catalytic performance.Herein,we reveal a bowl active site that can break the scaling relations,through investigating the catalytic mechanisms of N_(2)-to-NH_(3) conversion on the lanthanide intermetallic electride catalyst LaRuSi by first-principles modeling.This bowl active site,composed of four surface La cations and one subsurface Si atom rich in electrons,plays the key role in enabling efficient catalysis.With adaptive electrostatic and orbital interactions,the bowl active site promotes the adsorption and activation of N_(2) that delivers facile cleavage of N-N bond,while destabilizes the adsorptions of ^(*)NH_(x)(x=1,2,3)species,which facilitates the release of the final NH_(3) product.By comparison with other electride catalysts isostructural to LaRuSi,we confirm the breaking of scaling relations between the adsorptions of ^(*)NH_(x) species and that of^(*)N on the bowl active site.Thus,this bowl active site presents a design concept that breaks the scaling relations for highly efficient heterogeneous catalysis of N_(2)-to-NH_(3) conversion.
基金the National Natural Science Foundation of China(No.51975244)。
文摘For effectively improving the overall performance of fire truck frame structure,and solving the complexity of previous methods in the frame optimization design process,the traditional grey relational grade ranking needs to be improved.First,the first-order modal test was conducted to verify the validity of the initial frame model.Then,based on this model,a high-strength steel frame was designed to reduce deformation,maximum stress,and frame mass,and increase the fatigue life and the frequencies of the first bending modal and first torsional modal.Sixty groups of sample points were generated through Hammersley method.Subsequently,improved grey relational analysis with principal component analysis was proposed to realize the optimal design of the frame structure.Finally,the optimal combination of design parameters for the frame was obtained using the proposed method.Meanwhile,the optimized frame structure is found by comparing the models before and after optimization,and the mass is reduced by 14.8%.Moreover,the computational cost can be reduced by 135%when the proposed method is compared with the previous algorithm.Therefore,the proposed method can effectively improve the performance of the frame and improve the computational efficiency.
基金the Twelfth Five-Year National Key Technologies Research and Development Program of China(grant no.2012BAI07B00)the National High Technology Research and Development Program(‘863’Program)of China(grant nos.2013AA040801 and 2013AA040802)+1 种基金the National Natural Science Foundation of China(grant no.81271181)the Scientific Research Innovation Foundation for Youth Doctors of Peking University School of Stomatology(2011)
文摘The article introduces a new method for three-dimensional reproduction of edentulous dental casts,and wax occlusion rims with jaw relation by using a commercial high-speed line laser scanner and reverse engineering software and evaluates the method’s accuracy in vitro.The method comprises three main steps：（i）acquisition of the three-dimensional stereolithography data of maxillary and mandibular edentulous dental casts and wax occlusion rims;（ii）acquisition of the three-dimensional stereolithography data of jaw relations;and（iii）registration of these data with the reverse engineering software and completing reconstruction.To evaluate the accuracy of this method,dental casts and wax occlusion rims of 10 edentulous patients were used.The lengths of eight lines between common anatomic landmarks were measured directly on the casts and occlusion rims by using a vernier caliper and on the three-dimensional computerized images by using the software measurement tool.The direct data were considered as the true values.The paired-samples t-test was used for statistical analysis.The mean differences between the direct and the computerized measurements were mostly less than 0.04 mm and were not significant（P.0.05）.Statistical significance among 10 patients was assessed using one-way analysis of variance（P,0.05）.The result showed that the 10 patients were considered statistically no significant.Therefore,accurate three-dimensional reproduction of the edentulous dental casts,wax occlusion rims,and jaw relations was achieved.The proposed method enables the visualization of occlusion from different views and would help to meet the demand for the computer-aided design of removable complete dentures.
基金Project (No. 50475020) supported by the National Natural ScienceFoundation of China
文摘The theory of grey systems is a new technique for performing prediction, relational analysis and decision making in many areas. In this paper, the use of grey relational analysis for optimizing the square hole flanging process parameters with considerations of the multiple response (the average flanging height, regular flanging and maximum strain) is introduced. Various flanging parameters, such as the blank inner radius rb, blank inner width B0, are considered. An orthogonal array is used for the experimental design. Multiple response values are obtained using finite element analysis (FEA). Optimal process parameters are determined by the grey relational grade obtained from the grey relational analysis for multi-performance characteristics (flanging height, regular flanging and maximum strain). Analysis of variance (ANOVA) for the grey relational grade is implemented. The results showed good agreement with the experiment result. Grey relational analysis can be applied in multiple response optimi-zation designs.
文摘An experimental study was undertaken to express the hardening Swift law according to friction stir welding （FSW） aluminum alloy 2017. Tensile tests of welded joints were run in accordance with face centered composite design. Two types of identified models based on least square method and response surface method were used to assess the contribution of FSW independent factors on the hardening parameters. These models were introduced into finite-element code ＂Abaqus＂ to simulate tensile tests of welded joints. The relative average deviation criterion, between the experimental data and the numerical simulations of tension-elongation of tensile tests, shows good agreement between the experimental results and the predicted hardening models. These results can be used to perform multi-criteria optimization for carrying out specific welds or conducting numerical simulation of plastic deformation of forming process of FSW parts such as hydroforming, bending and forging.
文摘Selection of air conditioning（AC） cold/heat sources generally concerns about certain aspects and cannot reveal the whole profile of the problems. Grey relation analysis （GRA） is a data processing method to categorize the correlation extent of compared sequences and a certain reference sequence in a system with uncertain information. It is applied to evaluating and selecting AC cold/heat sources from four main aspects, which are technology, economy, reliability, and operation and management. Case study shows that the result for selecting AC cold/heat sources with the GRA method can be more reasonable and convincible. Thus it offers a new approach for designers in heating, ventilating and air conditioning field to compare and evaluate different AC cold/heat sou rces.
文摘Experimentally, the best design gives estimates of the desired effects and contrasts with maximum precision. Efficiency as a discriminating factor enables comparison of designs. The goal of Response Surface Methodology (RSM) is the determination of the best settings of the in-put variables for a maximum (or a minimum) response within a region of interest, R. This calls for fitting a model that adequately represents the mean response since such a model, is then used to locate the optimum. D-, A-, E- and T-Optimal designs of a rotatable design of degree two in four dimensions constructed using balanced incomplete block designs (BIBD) when the number of replications is less than three times the number of pairs of treatments occur together in the design and their relative efficiencies to general designs are presented. D-optimal design had 88 runs after replicating the factorial part twice and the axial part thrice with an optimal variance of 0.6965612 giving an efficiency of 97.7% while for A- and T-optimal designs they are formed with 112 runs each obtained by replicating the factorial part two times and axial part six times. Their optimal variances are 0.05798174 and 1.29828 respectively, with efficiency of 71.8% for A-optimal and 87.5% for T-optimal design. E-optimal design was found to be the most efficient design with an only 32 runs comprising only of the factorial part and with an optimal variance of 0.4182000, attaining an efficiency of approximately 1%. This study proposes the adoption of the E-optimal design in estimating the parameters of a rotatable second-order degree model constructed using BIBD for less costs and time saving.
基金co-supported by the National Natural Science Foundation of China(Nos.52272408,U21B2008)the Guangdong Basic and Applied Basic Research Foundation,China(No.2023B1515120018)。
文摘This paper investigates the configuration design associated with boundary-constrained swarm flying.An analytic swarm configuration is identified to ensure the passive safety between each pair of spacecraft in the radial-cross-track plane.For the first time,this work derives the explicit configurable spacecraft amount to clarify the configuration's accommodation capacity while considering the maximum inter-spacecraft separation constraint.For larger-scale design problem that involves hundreds of spacecraft,this paper proposes an optimization framework that integrates a Relative Orbit Element(ROE)affine transformation operation and successional convex optimization.The framework establishes a multi-subcluster swarm structure,allowing decoupling the maintenance issues of each subcluster.Compared with previous design methods,it ensures that the computational cost for constraints verification only scales linearly with the swarm size,while also preserving the configuration optimization capacities.Numerical simulations demonstrate that the proposed analytic configuration strictly meets the design constraints.It is also shown that the proposed framework reduces the handled constraint amount by two orders compared with direct optimization,while achieving a remarkable swarm safety enhancement based on the existing analytic configuration.
基金International (Regional) Cooperative Research Program of China National Natural Science Foundation Under Grant No. 50420120133 and Heilongjiang Natural Science Foundation Under Grant No. ZGJ03-03
文摘In order to propose a seismic design spectrum that includes the effect of rupture directivity in the near-fault region, this study investigates the application of equivalent pulses to the parameter attenuation relationships developed for near-fault, forward-directivity motions. Near-fault ground motions are represented by equivalent pulses with different waveforms defined by a small number of parameters （peak acceleration, A, and velocity V; and pulse period, Tv）. Dimensionless ratios between these parameters （e.g., ATv/V, VTv/D） and response spectral shapes and amplitudes are examined for different pulses to gain insight on their dependence on basic pulse waveforms. Ratios of ATv/V, VTv/D, and the ratio of pulse period to the period for peak spectral velocity （Tv-p） are utilized to quantify the difference between rock and soil sites for near-fault forward-directivity ground motions. The ATv/Vratio of recorded near-fault motions is substantially larger for rock sites than that for soil sites, while Tvp/Tv ratios are smaller at rock sites than at soil sites. Furthermore, using simple pulses and available predictive relationships for the pulse parameters, a preliminary model for the design acceleration response spectra for the near-fault region that includes the dependence on magnitude, rupture distance, and local site conditions are developed.
文摘Performance of the proton exchange membrane fuel cell(PEMFC)is appreciably affected by the channel geometry.The branching structure of a plant leaf and human lung is an efficient network to distribute the nutrients in the respective systems.The same nutrient transport system can be mimicked in the flow channel design of a PEMFC,to aid even reactant distribution and better water management.In this work,the effect of bio-inspired flow field designs such as lung and leaf channel design bipolar plates,on the performance of a PEMFC was examined experimentally at various operating conditions.A PEMFC of 49 cm2 area,with a Nafion 212 membrane with a 40%catalyst loading of 0.4 mg·cm-2 on the anode side and also 0.6 mg·cm-2 on the cathode side is assembled by incorporating the bio-inspired channel bipolar plate,and was tested on a programmable fuel-cell test station.The impact of the working parameters like reactants’relative humidity(RH),back pressure and fuel cell temperature on the performance of the fuel cell was examined;the operating pressure remains constant at 0.1 MPa.It was observed that the best performance was attained at a back pressure of 0.3 MPa,75°C operating temperature and 100%RH.The three flow channels were also compared at different operating pressures ranging from 0.1 MPa to 0.3 MPa,and the other parameters such as operating temperature,RH and back pressure were set as 75°C,100%and 0.3 MPa.The experimental outcomes of the PEMFC with bio-inspired channels were compared with the experimental results of a conventional triple serpentine flow field.It was observed that among the different flow channel designs considered,the leaf channel design gives the best output in terms of power density.Further,the experimental results of the leaf channel design were compared with those of the interdigitated leaf channel design.The PEMFC with the interdigitated leaf channel design was found to generate 6.72%more power density than the non-interdigitated leaf channel design.The fuel cell with interdigitated leaf channel design generated5.58%more net power density than the fuel cell with non-interdigitated leaf channel design after considering the parasitic losses.
基金JSPS-CAS Core-University Program on Basic Research of Nuclear Fusion Reactor Engineering in 2007
文摘In-vessel components are important parts of the EAST superconducting tokamak. They include the plasma facing components, passive plates, cryo-pumps, in-vessel coils, etc. The structural design, analysis and related R＆D have been completed. The divertor is designed in an up-down symmetric configuration to accommodate both double null and single null plasma operation. Passive plates are used for plasma movement control. In-vessel coils are used for the active control of plasma vertical movements. Each cryo-pump can provide an approximately 45 m^3/s pumping rate at a pressure of 10^-1 Pa for particle exhaust. Analysis shows that, when a plasma current of 1 MA disrupts in 3 ms, the EM loads caused by the eddy current and the halo current in a vertical displacement event （VDE） will not generate an unacceptable stress on the divertor structure. The bolted divertor thermal structure with an active cooling system can sustain a load of 2 MW/m^2 up to a 60 s operation if the plasma facing surface temperature is limited to 1500 ℃. Thermal testing and structural optimization testing were conducted to demonstrate the analysis results.
基金Special Scientific Research Fund of Earthquake Profession of China under Grant No.201208013National Natural Science Foundation of China under Grant No.51238012
文摘This paper presents a methodology for constructing seismic design spectra in near-fault regions. By analyzing the characteristics of near-fault pulse-type ground motions, an equivalent pulse model is proposed, which can well represent the characteristics of the near-fault forward-directivity and fling-step pulse-type ground motions. The normalized horizontal seismic design spectra for near-fault regions are presented using recorded near-fault pulse-type ground motions and equivalent pulse-type ground motions, which are derived based on the equivalent pulse model coupled with ground motion parameter attenuation relations. The normalized vertical seismic design spectra for near-fault regions are obtained by scaling the corresponding horizontal spectra with the vertical-to-horizontal acceleration spectral ratios of near-fault pulse-type ground motions. The proposed seismic design spectra appear to have relatively small dispersion in a statistical sense. The seismic design spectra for both horizontal and vertical directions can provide alternative spectral shapes for seismic design codes.
文摘The identification of design pattern instances is important for program understanding and software maintenance. Aiming at the mining of design patterns in existing systems, this paper proposes a subgraph isomorphism approach to discover several design patterns in a legacy system at a time. The attributed relational graph is used to describe design patterns and legacy systems. The sub-graph isomorphism approach consists of decomposition and composition process. During the decomposition process, graphs corresponding to the design patterns are decomposed into sub-graphs, some of which are graphs corresponding to the elemental design patterns. The composition process tries to get sub-graph isomorphism of the matched graph if sub-graph isomorphism of each subgraph is obtained. Due to the common structures between design patterns, the proposed approach can reduce the matching times of entities and relations. Compared with the existing methods, the proposed algorithm is not linearly dependent on the number of design pattern graphs. Key words design pattern mining - attributed relational graph - subgraph isomorphism CLC number TP 311.5 Foundation item: Supported by the National Natural Science Foundation of China (60273075) and the Science Foundation of Naval University of Engineering (HGDJJ03019)Biography: LI Qing-hua (1940-), male, Professor, research direction: parallel computing.
基金supported by National High Technology Research and Development Program of China (863 Program) (No. AA420060)
文摘In the course of network supported collaborative design, the data processing plays a very vital role. Much effort has been spent in this area, and many kinds of approaches have been proposed. Based on the correlative materials, this paper presents extensible markup language （XML） based strategy for several important problems of data processing in network supported collaborative design, such as the representation of standard for the exchange of product model data （STEP） with XML in the product information expression and the management of XML documents using relational database. The paper gives a detailed exposition on how to clarify the mapping between XML structure and the relationship database structure and how XML-QL queries can be translated into structured query language （SQL） queries. Finally, the structure of data processing system based on XML is presented.
基金the financial support from the Distinguished Young Scholars of China by the National Natural Science Foundation of China(51325802)the National Natural Science Foundation of China(51178340,52078358,and 52008304)。
文摘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.
基金This research is supported by the Chinese Special Projects of the National Key Research and Development Plan(2019YFB1405702).
文摘The acquisition of valuable design knowledge from massive fragmentary data is challenging for designers in conceptual product design.This study proposes a novel method for acquiring design knowledge by combining deep learning with knowledge graph.Specifically,the design knowledge acquisition method utilises the knowledge extraction model to extract design-related entities and relations from fragmentary data,and further constructs the knowledge graph to support design knowledge acquisition for conceptual product design.Moreover,the knowledge extraction model introduces ALBERT to solve memory limitation and communication overhead in the entity extraction module,and uses multi-granularity information to overcome segmentation errors and polysemy ambiguity in the relation extraction module.Experimental comparison verified the effectiveness and accuracy of the proposed knowledge extraction model.The case study demonstrated the feasibility of the knowledge graph construction with real fragmentary porcelain data and showed the capability to provide designers with interconnected and visualised design knowledge.
文摘The influence of KOH concentration (8 and 12 M) and curing conditions as temperature (40℃ and 60℃), time (7 and 28 days) and relative humidity (85% and 95% RH), on compressive strength of metakaolin-based geopolymers (MK-based GP) was evaluated. Derived from the experimental design technique, and using a factorial design 2<sup>K</sup> with two replications in the center point, eighteen experiments were conducted. The results reveal that the best performance conditions of geopolymerization to develop a higher compressive strength of 20 MPa are 12 M KOH to 60℃ and 85% RH at 28 curing days. With these conditions, the value of relative humidity of 85%, promotes high strength compact samples, and a maximum of 42 MPa at 90 days. The results of significant, compressive design of GP showed that KOH concentration and curing relative humidity were the most important factors, followed by curing time and temperature. The GP were characterized by XRD, and their evolution on compression strength was followed by SEM.
文摘Spacecraft formation flying is an attractive new concept in international aeronautic fields because of its powerful functions and low cost. In this paper, the formation design and PD closed-loop control of spacecraft formation flying in elliptical orbits are discussed. Based on two-body relative dynamics, the true anomaly is applied as independent variable instead of the variable of time. Since the apogee is considered as the starting point, the six integrating constants are calculated. Therefore, the algebraic solution is obtained for the relative motion in elliptical orbits. Moreover, the formation design is presented and both circular formation and line formation are provided in terms of an algebraic solution. This paper also discusses the PD-closed loop control for precise formation control in elliptical orbits. In this part, the error-type state equation is put forward and the linear quadratic regulator （LQR） method is used to calculate PD parameters. Though the gain matrix calculated from LQR is time-variable because the error-type state equation is time variable, the PD parameters are also considered as constants because of their small changes in simulation. Finally, taking circular formation as an example, the initial orbital elements are achieved for three secondary spacecraft. And the numerical simulation is analyzed under PD formation control with initial errors and J2 perturbation. The simulation results demonstrate the validity of PD closed-loop control scheme.
文摘This study integrated instrumental and relational approaches to the teaching and learning of solids in a preservice teacher＇s class. The researcher guided the preservice teachers to gather various prisms, pyramids, and spheres to study the total surface areas and volumes. At the end of the integrated models, the test scores showed closed relationships in the concurrent instructional strategies of the integrated models. The researcher therefore, recommended the design models for the teaching and learning of solids in mathematics.
