板梁桥在特种车辆荷载作用下的结构检测与评估

通过对桥梁在特种车辆荷载作用下的结构响应监测和理论计算分析,发现特载对该板梁桥造成的主要损害是削弱了板梁间的联结强度。最后按照相关规范对该桥在经历特种荷载后的技术状况进行了评定。     

政府工程采购的发展情况及存在问题

政府采购机制是规范化我国政府投资建设项目管理的一个重要工作领域。文章针对我国政府采购和政府工程采购的基本发展情况进行了说明,并对政府工程采购发展过程中存在的主要问题进行了分析。     

空车调整最小费用的合理分摊

借助多人合作对策的思想建立了铁路空车调整问题中最小费用合理分摊的数学模型，给出了建立理想分摊向量和特征函数的一种方法，并提供了具体解法，比较有效地解决了空车调整中最小费用的合理分摊问题，为最优调运方案的实际实施提供了前提和保障。     

The speed control effect of highway tunnel sidewall markings based on color and temporal frequency

The low‐luminance monotonous environment in the middle section of highway tunnels offers few reference points and is prone to cause severe visual illusion. Thus, drivers tend to underestimate their driving speed, which can induce speeding behaviors that result in rear‐end collisions. Therefore, discovering low‐cost methods of traffic engineering that reduce this visual illusion and ensure a steady driving speed is an important challenge for current highway tunnel operations. This study analyzes the effects of sidewall markings in typical highway tunnels, specifically observing how their colors and temporal frequencies affect the driver's speed perception in a low‐luminance condition. A three‐dimensional model of the middle section of highway tunnels was built in a driving simulator. Psychophysical tests of speed perception were carried out by the method of limits. The precision of the simulation model was then checked by comparing the results to field test data. The simulation tests studied the stimulus of subjectively equal speed and reaction time in relation to sidewall markings in different colors (red–white combined, yellow–white combined, and blue–white combined). Furthermore, based on the optimal color, the effects of sidewall marking with different temporal frequencies (0.4, 0.8, 1.2, 2, 4, 8, 12, 16, and 32 Hz) on the speed perception of drivers were also analyzed. The test results reveal that the color and temporal frequency of sidewall marking have a significant impact on the driver's stimulus of subjectively equal speed and reaction time. The subjects have the highest speed overestimation and an easy speed judgment with the red–white combined sidewall marking. Within the temporal frequency range of 4.45–7.01 Hz, the subjects have a certain degree of speed overestimation (less than 20%), and the speed perception is sensitive to the temporal frequency changes. Copyright © 2016 John Wiley & Sons, Ltd.     

Design and power flow analysis for multi-speed automatic transmission with hybrid gear trains

A design approach for multi-speed automatic transmission with hybrid gear trains is proposed. The approach can be used to design automatic transmissions composed of planetary gear trains, fixed-axis gear trains or hybrid gear trains and the shifts follow the “one controlled part changing rule”. This approach consists of four parts: determining graphical configuration of the system using hypergraphs, analyzing power flow formulation, obtaining shifts configurations by shift searching algorithm, and determining physical configuration. A nine forward speed automatic transmission is analyzed to highlight the capacities of the proposed approach. The results have shown that the suggested approach is much clearer and less time consuming than the methods currently used.     

车辆运行声车型自动分类的AR模型技术

利用AR参数模型提取采集到的车辆行驶时产生的车外噪声信号的特征,利用假设检验进行特征选择,并设计了BP神经网络进行分类识别.对道路现场采集到的2种车型共计110个信号进行分析,实验结果表明,通过AR参数模型提取车辆车外噪声特征实现车型自动分类是可行的,其分类的正确率达80% 以上.     

ABS最佳滑移率控制算法的增益修正研究

针对汽车ABS最佳滑移率控制中的控制结果最优化问题,提出了在控制算法中添加增益环节以进行修正的新方法:通过在实际滑移率和轮缸压力控制输出环节中引入增益系数,并采用响应面方法拟合增益系数和制动距离之间的定量关系,从而求出增益系数的最佳值,使系统滑移率控制的迟滞现象得到有效缓解.在MATLAB/Simulink环境下建立了相应的仿真模型,并以富康988EXC1型轿车为例,验证了所提方法的有效性.     

混凝土桥梁的温度作用分析和设计

对梯度温度应力的分解分析及对一典型的预应力混凝土连续刚构箱梁桥应力计算比较后,得出梯度温度作用特性及在桥梁结构设计的一些经验.     

降低节能车燃油消耗量的研究(2)

（上接2008年第10期） 化油器的浮子工作高度是否合理,对化油器能否正常工作影响很大,浮子工作高度过高或过低,会造成化油器油平面过低或过高,可燃混合气过浓或过稀,发动机出现动力不足、耗油量偏高等现象。调整浮子高度,尽可能降低浮子工作高度,使化油器提供适度的稀混合气,在不影响动力性或少量降低功率输出的情况下,可达到降低发动机油耗的目的。