共查询到20条相似文献，搜索用时 15 毫秒
1.
This study introduces a two-part factor mixture model as an alternative analysis approach to modeling data where strong floor effects and unobserved population heterogeneity exist in the measured items. As the names suggests, a two-part factor mixture model combines a two-part model, which addresses the problem of strong floor effects by decomposing the data into dichotomous and continuous response components, with a factor mixture model, which explores unobserved heterogeneity in a population by establishing latent classes. Two-part factor mixture modeling can be an important tool for situations in which ordinary factor analysis produces distorted results and can allow researchers to better understand population heterogeneity within groups. Building a two-part factor mixture model involves a consecutive model building strategy that explores latent classes in the data for each part as well as a combination of the two-part. This model building strategy was applied to data from a randomized preventive intervention trial in Baltimore public schools administered by the Johns Hopkins Center for Early Intervention. The proposed model revealed otherwise unobserved subpopulations among the children in the study in terms of both their tendency toward and their level of aggression. Furthermore, the modeling approach was examined using a Monte Carlo simulation. 相似文献
2.
Study on the Fuzzy COntrol Strategy of Automobile with CVT 总被引：3，自引：0，他引：3
In order to study the dynamic characteristics of automobile with a CVT system, a bond graph analysis model of continuously variable transmission is established.On the base of the simulation state space equations that are established with bond graph theory,a fuzzy control strategy with an expert system of starting process has been introduced.Considering uncertain system parameters and exterior resistance disturbing,the effect of the profile of membership function and the defuzzification algorthm on the capacity of the fuzzy controller has been studied.The result of simulation proves that the proposed fuzzy controller is effective and feasible,Such controller has been employed in the actual control and has proved practicable.The study lays a foundation for design of the fuzzy controller for automobile with a CVT system. 相似文献
3.
Giuseppe Carlo Marano 《浙江大学学报(A卷英文版)》2008,9(1):15-25
Based on a multiobjective approach whose objective function （OF） vector collects stochastic reliability performance and structural cost indices, a structural optimization criterion for mechanical systems subject to random vibrations is presented for supporting engineer＇s design. This criterion differs from the most commonly used conventional optimum design criterion for random vibrating structure, which is based on minimizing displacement or acceleration variance of main structure responses, without considering explicitly required performances against failure. The proposed criterion can properly take into account the design-reliability required performances, and it becomes a more efficient support for structural engineering decision making. The multiobjective optimum （MOO） design of a tuned mass damper （TMD） has been developed in a typical seismic design problem, to control structural vibration induced on a multi-storey building structure excited by nonstationary base acceleration random process A numerical example for a three-storey building is developed and a sensitivity analysis is carried out. The results are shown in a useful manner for TMD design decision support. 相似文献
4.
陈永乐 《福建工程学院学报》2021,(6):588-594
为了研究参数化防火设计方法和技术,从“分”与“合” 的角度探讨了防火规范编制与实际设计流程的矛盾,确定了按照正向设计逻辑将离散的规范条文组织为完整、标准化的设计算法和设计工具的研究思路。对防火规范和其他专项建筑规范中相关条文和设计参数进行系统性梳理,将设计流程总结为建筑定性、疏散宽度计算和疏散宽度校核与设计3 个部分,进而建立整体设计逻辑模型。基于计算性设计思维的技术和方法,总结了从设计规范的自然语言向算法的程序语言转化的一般方法,提出了符合实际设计流程和习惯的参数化设计算法,从理论和应用两个方面对参数化设计工具和方法在民用建筑防火设计中的应用进行了初步探索。 相似文献
5.
Based on the study of existing typical micro-milling tools and the actual demand for micro-milling tools,the P3 design principle and design flow for ultra-hard micro-milling tool were introduced to give basic guidance for theoptimization of micro-milling tools. Then, according to the P3 design flow, the manufacturing process of polycrystallinediamond （PCD） micro-milling tool was proposed, and the PCD micro-milling tool with diameter of 0.5 mm wasdeveloped. Finally, the micro-milling test on the slot was carried out to study the milling performance of PCD micromillingtool. 相似文献
6.
This paper makes an approach to the approximate optimum in structural design, which combines the global response surface (GRS)
based multivariate adaptive regression splines (MARS) with Move-Limit strategy (MLS). MARS is an adaptive regression process,
which fits in with the multidimensional problems. It adopts a modified recursive partitioning strategy to simplify high-dimensional
problems into smaller highly accurate models. MLS for moving and resizing the search sub-regions is employed in the space
of design variables. The quality of the approximation functions and the convergence history of the optimization process are
reflected in MLS. The disadvantages of the conventional response surface method (RSM) have been avoided, specifically, highly
nonlinear high-dimensional problems. The GRS/MARS with MLS is applied to a high-dimensional test function and an engineering
problem to demonstrate its feasibility and convergence, and compared with quadratic response surface (QRS) models in terms
of computational efficiency and accuracy. 相似文献
7.
张建军 《北京工业职业技术学院学报》2013,12(2):14-17
网站设计中的SEO优化策略关系着整个网站的访问量和网站的宣传力度,为了提升网站的宣传力度,通过对搜索引擎工作过程和原理的分析,提出了网站设计中结构布局、页面设计和内容设计的优化策略,在网站设计中具有重要的应用价值。 相似文献
8.
To improve the suspension performance and steering stability of light vehicles, we built a kinematic simulation model of a whole independent double-wishbone suspension system by using ADAMS software, created random excitations of the test platforms of respectively the left and the right wheels according to actual running conditions of a vehicle, and explored the changing patterns of the kinematic characteristic parameters in the process of suspension motion. The irrationality of the suspension guiding mechanism design was pointed out through simulation and analysis, and the existent problems of the guiding mechanism were optimized and calculated. The results show that all the front-wheel alignment parameters, including the camber, the toe, the caster and the inclination, only slightly change within corresponding allowable ranges in design before and after optimization. The optimization reduces the variation of the wheel-center distance from 47.01 mm to a change of 8.28 mm within the allowable range of -10 mm to 10 mm, promising an improvement of the vehicle steering stability. The optimization also confines the front-wheel sideways slippage to a much smaller change of 2.23 mm; this helps to greatly reduce the wear of tires and assure the straight running stability of the vehicle. 相似文献
9.
A maximally flat FIR filter design method based on explicit formulas combined with simulated annealing and random search was presented. Utilizing the explicit formulas to calculate the ini- tial values, the firate-word-length FIR filter design problem was converted into optimization of the filter coefficients, An optimization method combined with local discrete random search and simulated annealing was proposed, with the result of optimum solution in the sense of Chebyshev approximation. The proposed method can simplify the design process of FIR filter and reduce the calculation burden. The simulation result indicates that the proposed method is superior to the traditional round off method and can reduce the value of the objective function to 41%～74%. 相似文献
10.
The aim of this study is to explore the potential of various plant ramifications as concept generators for creating a brand topology optimization solution for stiffness design of continuum structures under harmonic force excitations. Firstly, a mathematical model is built to identify analytical laws that underlie the optimality of the effective but individual design rules of existing leaf venation morphogenesis. Then, a new evolutionary algorithm is developed to find the optimal topology of stiffened structures under harmonic force excitations. Candidate stiffeners are treated as being alive, growing at locations with a maximum displacement response gradient along the structural surface. Since the scale of the candidate stiffeners can be adaptively expanded or reduced during the simulation, computational resources could be saved, thereby enhancing the flexibility of topology optimization. Finally, the suggested approach is applied to a case study in which the displacement amplitude at specified locations is defined as the objective and the volume of added stiffeners as the constraint. The simulation process shows how the stiffness design of continuum structures can be conducted automatically using this bionic approach. 相似文献
11.
赖学江黄森炜廖洪毅曹智校陈清云 《福建工程学院学报》2021,(4):372-377
以深圳某办公楼为例,探讨冰蓄冷空调系统运行策略的优化。采用鸿业全年负荷计算及能耗分析软件(HY-EP)进行全年动态负荷模拟,对冷负荷的负荷率进行分析。在选定冰蓄冷系统后,基于模拟结果和地区的峰谷平电价的特点,采用了基于全年动态负荷结果分析预测和结合前一天的负荷作为当日的负荷预测,将全年逐日运行策略简化为4 种设备的运行方案,控制较为容易实现,且需要增加的初投资较少,是结合冰蓄冷系统与全年动态负荷模拟技术的创新应用。 相似文献
12.
An approach was presented to intensify the mixing process. Firstly, a novel concept, the dissipation of mass transfer ability(DMA) associated with convective mass transfer, was defined via an analogy to the heat-work conversion. Accordingly, the focus on mass transfer enhancement can be shifted to seek the extremum of the DMA of the system. To this end, an optimization principle was proposed. A mathematical model was then developed to formulate the optimization into a variational problem. Subsequently, the intensification of the mixing process for a gas mixture in a micro-tube was provided to demonstrate the proposed principle. In the demonstration example, an optimized velocity field was obtained in which the mixing ability was improved, i.e., the mixing process should be intensified by adjusting the velocity field in related equipment. Therefore, a specific procedure was provided to produce a mixer with geometric irregularities associated with an ideal velocity. 相似文献
13.
14.
褚万军 《宁夏师范学院学报》2013,(6):88-92
分析了随着计算机网络技术的发展,许多高校网络实验设备的缺乏甚至空白,已很难满足实践教学的需求,真实的实训环境难以搭建,导致计算机网络实践教学很难进行的现状;介绍了RIP协议的基本原理,提出了一种基于Packet Tracer模拟环境下的RIP协议配置及实现的仿真实践教学设计;给出了网络拓扑结构图,实现了RIP协议的配置全过程,并对实践的结果进行了验证,为构建RIP实践教学环境提供了一种可行的、廉价的高性能解决方案. 相似文献
15.
针对复杂结构仿真中有限元仿真精度及效率不高的问题,提出采用高阶响应面方法进行建模及优化,并用桥梁模型来验证。选取合适参数,采用试验设计获取响应样本点,基于数理统计的逐步回归法对各自变量进行显著性分析,筛选对目标响应函数显著度高的自变量,再应用最小二乘法拟合各自变量的系数,得到三阶多项式响应面模型,用多目标优化算法进行优化。对比修正前后模态频率,结果表明应用响应面方法能得到简单而高精度的结构模型,从而验证了高阶响应面方法在建模及模型优化中的有效性。 相似文献
16.
In order to enhance the reliability of an uncertain structure with interval parameters and reduce its chance of function failure under potentially critical conditions, an interval reliability-based design optimization model is constructed. With the introduction of a unified formula for efficiently computing interval reliability, a new concept of the degree of interval reliability violation (DIRV) and the DIRV-based preferential guidelines are put forward for the direct ranking of various design vectors. A direct interval optimization algorithm integrating a nested genetic algorithm (GA) and the Kriging technique is proposed for solving the interval reliability-based design model, which avoids the complicated model transformation process in indirect ones and yields an interval solution that provides more insights into the optimization problem. The effectiveness of the proposed algorithm is demonstrated by a numeric example. Finally, the proposed direct reliability-based design optimization method is applied to the optimization of a press upper beam with interval uncertain parameters, the results of which demonstrate its feasibility and effectiveness in engineering. 相似文献
17.
The structure stiffness of presses has great effects on the forming precision of workpieces, especially in near-net or net shape forming. Conventionally the stiffness specification of presses is empirically determined, resulting in poor designs with insufficient or over sufficient stiffness of press structures. In this paper, an approach for the structure design of hydraulic presses is proposed, which is forming-precision-driven and can make presses costeffective by lightweight optimization. The approach consists of five steps:(1)the determination of the press stiffness specification in terms of the forming precision requirement of workpieces;(2)the conceptual design of the press structures according to the stiffness and workspace specifications, and the structure configuration of the press;(3)the prototype design of the press structures by equivalently converting the conceptual design to prototypes;(4)the selection of key structure parameters by sensitivity analysis of the prototype design; and(5)the optimization of the prototype design. The approach is demonstrated and validated through a case study of the structure design of a 100 MN hydraulic press. 相似文献
18.
The combined use of dry cooling （DC） system and dedicated ventilation （DV） system to decouple cool-ing and dehumidification process for energy efficiency was proposed for subtropical climates like Hong Kong. In this study, the energy performance and condensation risk of the use of DCDV system were examined by analyzing its ap-plication in a typical office building in Hong Kong. Through hour-by-hour simulation using actual equipment per-formance data and realistic building and system characteristics, it was found that with the use of DCDV system, the annual energy consumption could be reduced by 54%in comparison with the conventional system （constant air vol-ume with reheat system）. In respect of condensation risk, it was found that the annual frequency of occurrence of con-densation on DC coil was 35 h. Additional simulations were conducted to examine the influence of different parame-ters on the condensation risk of DCDV system. Measures to ensure condensate-free on DC coil were also discussed. 相似文献
19.
To reduce the environmental impact of mechanical parts, an approach integrating structural design and material selection was studied. Adding the discrete variable of material, a hybrid optimization model was built with the aim of minimizing environmental impact and based on an ordinary structure optimization model. An optional material set was built by combining measures of qualitative and quantitative screening, while the lifecycle environmental impact of the materials was quantified using the method of Eco-indicator 99. Two groups of structurally optimal solutions were calculated with ideal and negative-ideal materials selected respectively, and then the hybrid model was simplified by comparing the solutions. A material environmental performance index was calculated using an analytic method. By comparing this index for every material in the optional material set, the optimal material can be found and the structural solutions calculated. This method was applied to a dowel bar design process as a case study. The results show that the environmental impact of each material has a significant effect on the optimal structural solution, and it is necessary to study the integration of structural design and material selection. 相似文献
20.
为解决二维无线传感器网络随机部署产生的节点分布不均、覆盖率低的问题,提出一种融合元启发式算法的网络部署方案。该方案以节点部署空间作为约束条件、网络覆盖范围作为目标函数对二维网络覆盖模型进行数学建模。针对白骨顶鸡优化算法全局探索能力不强且在迭代后期容易陷入局部最优的缺点,该方案引入复合突变策略和随机反向策略对原算法进行改进。在二维网络覆盖模型进行的仿真测试结果表明:部署改进白骨顶鸡优化算法的二维无线传感器网络不仅网络覆盖率更高,节点也更加均匀,验证了改进白骨顶鸡优化算法解决节点部署问题的有效性和实用性。 相似文献