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
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
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
A mathematical model was developed for layout optimization of truss structures with discrete variables subjected to dynamic stress, dynamic displacement and dynamic stability constraints. By using the quasi-static met...A mathematical model was developed for layout optimization of truss structures with discrete variables subjected to dynamic stress, dynamic displacement and dynamic stability constraints. By using the quasi-static method, the mathematical model of structure optimization under dynamic stress, dynamic displacement and dynamic stability constraints were transformed into one subjected to static stress, displacement and stability constraints. The optimization procedures include two levels, i.e., the topology optimization and the shape optimization. In each level, the comprehensive algorithm was used and the relative difference quotients of two kinds of variables were used to search the optimum solution. A comparison between the optimum results of model with stability constraints and the optimum results of model without stability constraint was given. And that shows the stability constraints have a great effect on the optimum solutions.展开更多
This research explored the application potential of PUM thin-overlay technology on airport rapid maintenance.The rapid curing process of polyurethane binder determines the limited time window for mixing and constructi...This research explored the application potential of PUM thin-overlay technology on airport rapid maintenance.The rapid curing process of polyurethane binder determines the limited time window for mixing and construction of polyurethane-bonded mixture(PUM),which presents significant difference with hot-mix asphalt(HMA)technology.Therefore,this research investigated and optimized the mix design of PUM for airport thin-overlay technology based on its thermosetting characteristics.First,limestone and basalt were comprehensively compared as an aggregate for PUM.Then,the effects of molding and curing conditions were studied in terms of mixing time,molding method,molding parameters and curing temperature.Statistical analysis was also conducted to evaluate the effects of gradation and particle size on PUM performances based on gray relational analysis(GRA),thus determining the key particle size to control PUM performances.Finally,the internal structural details of PUM were captured by X-ray CT scan test.The results demonstrated that it only took 12 hours to reach 75%of maximum strength at a curing temperature of 50°C,indicating an efficient curing process and in turn allowing short traffic delay.The internal structural details of PUM presented distribution of tiny pores with few connective voids,guaranteeing waterproof property and high strength.展开更多
研究目的:基于国内外对道岔转辙器轮载在过渡段范围内变化规律研究提出的道岔轮轨关系设计指标和结构不平顺设计指标,结合生产实际,提出道岔动力参数设计方法,编制成岔区轮轨静态接触几何关系计算程序,实现道岔转辙器轮载过渡段的快速...研究目的:基于国内外对道岔转辙器轮载在过渡段范围内变化规律研究提出的道岔轮轨关系设计指标和结构不平顺设计指标,结合生产实际,提出道岔动力参数设计方法,编制成岔区轮轨静态接触几何关系计算程序,实现道岔转辙器轮载过渡段的快速优化设计。研究结论:以LMA型踏面动车组直向通过设计时速350 km 18号道岔为例进行分析,得出:(1)降低尖轨起始承载断面顶面降低值对提高车体的横向加速度是有利的;(2)减小尖轨起始承载的断面对提高车体的横向稳定性也是有利的;(3)轮载转移点越靠后,道岔的横向及竖向不平顺明显增加,尖轨顶面纵坡虽有所减小,但对车体的横向平稳性极为不利;(4)动力学参数设计法在方案比选中是合理的和可行的。展开更多
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.
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.
基金Project supported by the National Natural Science Foundation of China (Nos. 10002005 and 10421002)the Natural Science Foundation of Tianjin (No.02360081)the Education Committee Foundation of Tianjin (No.20022104)the Program for Changjiang Scholars and Innovative Research Team in University of China and the 211 Foundation of Dalian University of Technology
文摘A mathematical model was developed for layout optimization of truss structures with discrete variables subjected to dynamic stress, dynamic displacement and dynamic stability constraints. By using the quasi-static method, the mathematical model of structure optimization under dynamic stress, dynamic displacement and dynamic stability constraints were transformed into one subjected to static stress, displacement and stability constraints. The optimization procedures include two levels, i.e., the topology optimization and the shape optimization. In each level, the comprehensive algorithm was used and the relative difference quotients of two kinds of variables were used to search the optimum solution. A comparison between the optimum results of model with stability constraints and the optimum results of model without stability constraint was given. And that shows the stability constraints have a great effect on the optimum solutions.
基金This study was supported by the National Natural Science Foundation of China under Grant number of 51861145402.
文摘This research explored the application potential of PUM thin-overlay technology on airport rapid maintenance.The rapid curing process of polyurethane binder determines the limited time window for mixing and construction of polyurethane-bonded mixture(PUM),which presents significant difference with hot-mix asphalt(HMA)technology.Therefore,this research investigated and optimized the mix design of PUM for airport thin-overlay technology based on its thermosetting characteristics.First,limestone and basalt were comprehensively compared as an aggregate for PUM.Then,the effects of molding and curing conditions were studied in terms of mixing time,molding method,molding parameters and curing temperature.Statistical analysis was also conducted to evaluate the effects of gradation and particle size on PUM performances based on gray relational analysis(GRA),thus determining the key particle size to control PUM performances.Finally,the internal structural details of PUM were captured by X-ray CT scan test.The results demonstrated that it only took 12 hours to reach 75%of maximum strength at a curing temperature of 50°C,indicating an efficient curing process and in turn allowing short traffic delay.The internal structural details of PUM presented distribution of tiny pores with few connective voids,guaranteeing waterproof property and high strength.
文摘研究目的:基于国内外对道岔转辙器轮载在过渡段范围内变化规律研究提出的道岔轮轨关系设计指标和结构不平顺设计指标,结合生产实际,提出道岔动力参数设计方法,编制成岔区轮轨静态接触几何关系计算程序,实现道岔转辙器轮载过渡段的快速优化设计。研究结论:以LMA型踏面动车组直向通过设计时速350 km 18号道岔为例进行分析,得出:(1)降低尖轨起始承载断面顶面降低值对提高车体的横向加速度是有利的;(2)减小尖轨起始承载的断面对提高车体的横向稳定性也是有利的;(3)轮载转移点越靠后,道岔的横向及竖向不平顺明显增加,尖轨顶面纵坡虽有所减小,但对车体的横向平稳性极为不利;(4)动力学参数设计法在方案比选中是合理的和可行的。
