考虑与跟驰模型结合的自由换道模型及仿真

考虑跟驰过程与换道过程的结合,在车辆换道过程的具体实施过程中引入跟驰模型,以全速度差模型为基础,对换道过程中的换道加速度进行确定,并通过对天津市视频录像换道时间的统计分析,建立了换道距离与换道时车头偏角之间的关系.最后利用Netlogo平台对模型进行了实现与仿真分析,结果表明:该模型很好地体现了实际换道的特点.     

考虑热力耦合的轨道车辆车轮建模与仿真

以城市轨道车辆车轮为研究对象, 建立了S型辐板轨道车辆车轮模型, 利用有限元方法研究了不同磨耗情况下车轮结构应力和热应力的变化特点, 分析了结构场和温度场的耦合作用对车轮应力特性的影响, 获得了热力耦合作用下的车轮结构应力和热应力的耦合规律。仿真结果表明: 随着车轮踏面的磨耗, 其结构应力、热应力与耦合应力均呈非线性变化, 在车轮直径为800~840mm的磨损区间, 耦合应力较稳定, 当磨损到直径小于800mm之后, 其耦合应力增长较快, 特别是磨耗到770mm时, 耦合应力骤升, 磨耗到限时耦合应力达到179.5 MPa; 车轮的耦合应力是复杂的三维空间力系的叠加, 在耦合应力分布上, 车轮辐板处耦合应力最大点位置发生漂移现象, 制动结束时的车轮辐板处耦合应力最大, 大于结构应力最大值与热应力最大值, 因此, 耦合应力在车轮应力中占主导作用, 在车轮的结构设计时, 建议考虑结构应力和热应力的耦合作用, 把耦合应力作为车轮疲劳强度的评价指标。     

Computer simulation of microscopic stress distribution in complex microstructure using a phase field model

Microscopic stress distribution in a metallic material which has complex microstructure is simulated using a phase field model. The fundamental equations which take into account the coupling effects among phase transformation, temperature and stress/strain are used, while thermal effects are neglected to focus on the volumetric change due to phase transformation in this paper. A two-dimensional square region is considered, and the evolution of microscopic stress and the resultant residual stress distribution are calculated using the finite element method. As the phase transformation progresses and grains grow larger, stress is generated around the growing interface. When a grain collides with another one, specifically large stress is observed. Residual stress is finally distributed in the microstructure formed, and apparently large stresses are retained along the grain boundaries. Subsequently, dependency of the stress distribution on microstructure pattern is investigated. First, variously sized square grains are tested, and it reveals that the maximum stress tends to decrease as the grain size becomes smaller. Next, the shapes of the grains are varied. As a result, the stress distribution is remarkably affected, while the maximum stress value does not change so much. More complicated grain arrangement is finally tested with eight or nine grain models. Then, it is revealed as a common feature that large stress is generated along the grain boundaries and that the stress distribution is dependent on the grain arrangement.     

Soil microstructure evolution and macro deformation mechanism for controlling construction disturbance in Shanghai soft soil

Abundant practical evidences have indicated that the soil progressively loses its structural configuration under construction disturbance and this can result in long-term macro deformation. The fundamental understanding of soil microstructure evolution subject to construction disturbance is necessary for controlling disturbance in excavation projects and minimizing ground settlement. The microstructure of Shanghai soft soil is investigated in this study. The laboratory isotropic compression tests are respectively performed on the virgin soil and the reconstructed Shanghai soft soil to investigate the macro deformation of soil under disturbance. Discrete element method model is used to study the micro particle level responses of soil under disturbance. The laboratory tests and numerical simulations provide theoretical basis for construction disturbance mitigation to ensure safety and stability of excavation projects.     

Simulation and analysis of microstructure evolution of IN718 in rotary forgings by FEM

A numerical analysis was performed to study the in?uence of process parameters on the microstruc-ture evolution of IN718 alloy in rotary forging using the finite element method(FEM).For this purpose, a constitutive equation considering the effects of strain hardening and dynamic softening of IN718 alloy was built.The constitutive equation and microstructure models were implemented into the finite element code to investigate the microstructure evolution during rotary forging subject to large deformations.The simulations were carried out in the ratio of initial height to diameter range 0.2-0.8, the angle of the rocker 3°-7° and the relative feed per revolution range 0.01-0.1 r-1.The research results revealed the deformation mechanism and the correlation of process parameters with the grain size evolution of IN718 alloy during rotary forging.These provide evidence for the selection of rotary forging parameters.     

经皮注射骨形态发生蛋白复合PVP载体修复股骨头骨缺损的实验研究

目的　研究经皮注射骨形态发生蛋白 (BMP)复合可溶性载体聚乙烯吡咯烷酮 (PVP)是否能促进股骨头骨缺损的修复 ,探讨治疗股骨头骨缺损的新方法。方法　将 2 0只成年兔犬股骨头部制成骨缺损模型 ,实验分四组 ,注射BMP与PVP复合组 ,单纯注射BMP组 ,自然修复组和正常组。通过X线片、组织病理学、碱性磷酸酶、新生骨钙磷含量测定和生物力学等手段检测其成骨性能。结果　注射BMP PVP组术后 1 2周全部发生骨性愈合 ,而单纯注射BMP及自然修复组无 1例发生骨性愈合。结论　经皮注射BMP PVP复合物具有促进骨修复的作用 ,有可能成为治疗骨缺损的一种方法。     

考虑旋转效应的弹性车轮降噪效果与影响参数研究

以某款弹性车轮及其原型普通车轮为研究对象,在考虑车轮旋转带来的移动荷载效应和陀螺效应的前提下,应用2.5维结构有限元法和2.5维声学边界元法预测车轮在给定轮轨粗糙度激励下的振动和声辐射;针对40、80和120 km·h^-1三个运行速度,分析了弹性车轮的降噪机理,研究了弹性车轮橡胶层的材料参数对弹性车轮降噪效果的影响。研究结果表明：车轮旋转使得原本非0节径模态频率处的声功率峰值分叉为2个峰值,其中一个峰值频率比原模态频率高,另一个峰值频率比原模态频率低,2个峰值频率差近似等于车轮的旋转频率乘以2倍的模态节径数;在所考虑的工况下,车轮旋转对车轮声辐射的影响最高达3.2 dB(A),因此,在预测车轮的声辐射时,必须考虑旋转对预测结果的影响;如果橡胶弹性模量太小,则轮箍容易振动,从而有可能辐射比普通车轮更高的噪声;从车轮声辐射的角度,橡胶弹性模量存在一个最佳值,在这个值下,弹性车轮的声功率最低,且低于原型车轮的声功率10 dB(A)以上;增加橡胶阻尼总是有利于车轮噪声的控制,但增加阻尼产生的降噪效果随橡胶弹性模量的增大而降低;对于同一弹性车轮,随着运行速度的提升,相对原型普通车轮的降噪效果不断降低,速度从40 km·h^-1增大到120 km·h^-1,降噪效果降低达4 dB(A)以上。     

Sensitivity analysis of parameters for multi-stand roll forming using a new booting model

Multi-stand roll forming is a process that has very complicated deformation behaviour and shows significant nonlinearity.In this paper, the sensitivity analysis of parameters for multi-stand roll forming was performed via a new booting finite element method(FEM) model.Compared with the most of simulation, the new model is more consistent with production process and can account for the effects of roll rotating speed.Based on the model, the process of an open section channel formed with 10 passes was simulated and the sensitivity analysis was conducted with orthogonal experiment design combined FEM model.The multi-stand roll forming process can be efficiently analyzed by the new booting model.And sensitivity analysis shows the hardening exponent plays an important role in controlling the quality of the products.     

Alterable-element method for vehicle-bridge interaction considering the transient jump of wheel

The so called "alterable-element method" (AEM) was introduced to deal with the coupling interac-tion of vehicle and sub-structure considering the actual transient jump of wheel, while the classical "contact allalong" assumption based on which wheels and lower structure are always contact was abandoned. The alterableelement used in this method is a conceptional element, which is used to calculate the coupling interaction ofupper and lower structures and has some typical characteristics: firstly it flows along with the moving of contactpoint; secondly whether it is used for calculation depends on the contact state; thirdly its sizes could changeaccording to specific problems and so on. VISUAL FORTRAN program was coded, and different moving vehiclemodels were presented taking into consideration the effects of random corrugation in the numerical study. Thenumerical solutions are favored comparing with the results obtained by alternative methods when there is nojump phenomenon existed. With abrupt irregularity, the transient jump of wheel was studied using the presentmethod.     

考虑风险和贡献因素的港口合作收益分配模型

为了有效地激励港口之间实现联盟, 实现港口联盟成员的共赢, 考虑各港口在合作中的贡献及所承担的风险, 根据互惠互利原则、贡献收益相匹配原则和风险收益相匹配原则, 构建一个基于合作博弈的港口收益分配的非线性规划模型, 通过具体算例对模型进行了应用分析。分析结果表明: 由收益分配模型得到的各个港口的收益均高于各个港口单独经营所得到的收益, 各个港口的收益之和等于3个港口联盟体所得到的总收益, 因此, 规划模型能带来较高的经济效益, 并实现经济效益的合理分配。     

考虑开行比例的大小交路列车开行方案优化

分析了城市轨道交通的大小交路列车开行比例关系,划分了2种典型的大小交路列车开行比例; 基于跨交路乘客对直达列车的选择偏好与换乘行为,提出了2种开行比例模式下乘客的广义出行费用计算方法; 考虑共线区段列车运行间隔的匹配关系,计算了运营车底数量; 以乘客出行费用和企业运营费用最小化为目标,构建了适用于多编组的大小交路列车开行方案优化模型,并针对开行方案编制流程和模型特点,设计了开行时段优化算法和遗传算法对模型进行求解; 以上海地铁8号线为例,研究了全日列车开行时段划分及其最优开行方案; 考虑固定编组和多编组与大小交路的组合运营模式,分析了单一交路运营与组合运营模式下的最优方案及其运营指标; 研究了乘客选择偏好和时间价值对开行方案和小交路折返站的影响。研究结果表明：与单一交路运营模式相比,大小交路运营模式下的乘客候车时间成本增幅超过11%;固定列车编组条件下,开行比例1:1模式下的小交路长度比开行比例2:1模式下的小交路长4个区间; 多编组运营的早高峰系统总成本降幅超过1.87%,比固定编组运营更具优势; 乘客对直达列车的选择偏好对多编组开行方案的影响较固定编组更大,当选择偏好概率大于0.3时,多编组开行方案的小交路折返站位置向外围延伸; 当时间价值增至原来的1.8倍及以上时,固定编组的运营模式由大小交路变为单一交路。     

考虑拥挤交通流再分配的单点自组织信号控制方法

为解决目前拥挤交通流无法得到有效疏散的问题,研究一种考虑局部拥挤条件下交通流再分配的自组织信号控制方法。提出该方法的基本原理,拥挤交通流的再分配原则,关键相位的确定方法,并结合模糊理论研究绿灯相位的切换条件,最后以单交叉口为例,借助VISSIM软件进行仿真验证。结果表明,该方法有较好的控制效果。     

边坡变形破坏机制的底摩擦试验模拟

介绍边坡变形破坏机制的底摩擦试验模拟方法,通过底摩擦试验模拟边坡的变形破坏演变过程,分析边坡的变形破坏机制,找出适当的边坡处治办法。     

Morphological evolution of a void under thermal and mechanical loads

A model for the morphological evolution of a void under thermal and mechanical loads is established, and the thermodynamics potential of the model is given based on energy principle. Thus, the path and the bifurcation condition of the morphological evolution of the void are described, which gives some insight into the reliability of the interconnect under combined thermal and mechanical loads.     

客车企业现状与核心竞争力的形成

我国大中型客车行业，有目录内生产企业71家，形成了年产10万辆大中型客车的生产能力，而1999年，全国客车市场有效需求量仅为3.7万辆．全行业生产能力有效发挥37％。竞争由此愈演愈烈，行业内的每一个人都在情不自禁地去考虑竞争带来的威胁和机会。     

城市出租车需求仿真预测模型研究

针对城市出租车需求的动态不确定性问题,在分析城市出租车需求系统的特点和影响因素的基础上,构建其人工神经网络BP网络预测模型,应用MATLAB进行数值仿真,研究城市出租车需求变化的动态规律,以期对城市出租车需求量作出有效预测.     

从车展看大型客车市场现状及发展趋势

商用车展,一方面是参展商向专业观众展示产品和企业形象,提升企业自身的知名度和美誉度;另一方面是提供业内信息交流,帮助企业发现目标客户、了解产品技术市场发展和分析各企业战略布局的最新趋势。     

考虑软弱下卧层及沉降影响的独立基础优化设计

笔者讨论了独立基础在考虑强度和变形条件下的优化设计 .导出了确定独立基础底面尺寸的优化数学模型 ,导出了偏心荷载作用下基础的高度和底面配筋的计算公式 ,求解优化解采用最优化方法的复合形法和罚函数法 .通过基础实例和工程实例的计算表明优化设计可以节省材料和工程量 5 %～ 1 6 % .所以将本文优化方法用于基础设计 ,会产生较大的经济效益 .     

事件检测概率神经网络模型的建立与验证

在对概率神经网络(PNN)的分类机理、输入向量选取和网络设置进行分析的基础上,建立了用于识别两类事件模式(无事件模式和有事件模式)的事件检测PNN模型。采用高速公路路段1-880实地线圈数据集和事件数据集验证模型,通过比较PNN模型与多层前向神经网络(MLF)模型的结果,发现无论对于向北、向南或混合方向的高速公路事件检测,PNN模型的检测率(DR)比MLF模型高;平均检测时间(MTTD)比MLF模型短:但误报率(FAR)也较高。概率神经网络是高速公路事件检测的一种有效算法,其在理论基础、算法和学习速度等方面比多层前向神经网络具有优势。     

桥式起重机的防摇问题及其分析与仿真

笔者在文中论述了桥式起重机的防摇问题运动分析的简明数学模型,应用经典控制理论化解为传递函数模型,并使用SIMULINK对此进行仿真,说明了起重机运行时吊物摇动的基本规律和基本控制方法.