舰艇螺旋桨外形及参数测定

利用反射片作为瞄准目标的电子全站仪用于工业产品不规则外形检测和设计参数测定，需要解决的问题是：指定点位的测设，大地三维坐标的测定，大地坐标系和工业设计独立坐标系的转换，图形的制作和参数计算，本文介绍利用电子全站仪测定舰艇螺旋桨的外形尺寸及叶片参数的理论、方法和实测结果。     

U71Mn钢疲劳裂纹扩展速率da/dN的测定与分析

对铁路钢轨材料U71Mn钢的疲劳裂纹扩展速率da/dN进行了测定,并用AutoCAD较为精确地得到了a-N曲线的离散值,最后用回归分析法得到了该材料在稳定扩展状态下的裂纹扩展速率。试验数据的相关系数检验表明:本文所得到的结果比较理想,对评价其寿命有参考价值。     

高速公路工程招标工作探讨

建筑工程招投标制度是实行由建设单位公开招标,通过竞争,选择质量高、信誉好、造价及施工方案合理的企业承担施工任务的制度。招标工作是工程建设成功与否的基础,文中对在招标工作中标段划分、招标的先后顺序、标价确定的合理性和合同文件制订的科学性等问题进行了深入探讨。     

Travel mode choices in small cities of China: A case study of Changting

The existing literature on urban transportation planning in China focuses primarily on large cities and neglects small cities. This paper aims to fill part of the knowledge gap by examining travel mode choice in Changting, a small city that has been experiencing fast spatial expansion and growing transportation problems. Using survey data collected from 1470 respondents on weekdays and weekends, the study investigates the relationship between mode choice and individuals’ socio-economic characteristics, trip characteristics, attitudes, and home and workplace built environments. While more than 35 percent of survey respondents are car owners, walk, bicycle, e-bike, and motorcycle still account for over 85 percent of trips made during peak hours. E-bike and motorcycle are the dominant means of travel on weekdays, but many people shift to walking and cycling on weekends, making non-motorized and semi-motorized travel especially important for non-commuting trips. Results of multinomial logistic regression show that: (1) job-housing balance might exert different effects on mode choice in different types of urban areas; (2) negative attitude towards e-bike and motorcycle is associated with more walking and cycling; and (3) land use diversity of workplace is related to commuting mode choice on weekdays, while land use diversities of both residential and activity places do not significantly affect mode choice on weekends. Our findings imply that planning and design for small cities needs to differentiate land use and transportation strategies in various types of areas, and to launch outreach programs to shift people’s mode choice from motorized travel to walking and cycling.     

驾驶员操作域的计算机辅助判定

本文介绍了一种驾驶员手臂的运动模型，该模型共有六个自由度，肩部有五个，肘部有一个，用该模型进行驾驶员操作域的计算机辅助判定。据此对驾驶室内的仪器，仪表及各类控制器进行优化而已设计，使其人机工效达到最佳。     

内燃机车中间直流电压的选择与变流系统标准化设计

针对我国交流传动内燃机车电传动系统的设计要求，分析了中间直流电压对电传动系统的影响，探讨了中间直流电压的选择及变流系统标准化，系统化设计思想，提出了选择1500V和2600V作为中间直流电压设计标准的建议，在此基础上计算出各种机车功率范围的几种标准化牵引变流器的主要参数。     

西南地区膨胀土(岩)堑坡湿化层厚度的确定

本文论述了湿化层的形成机理和确定方法 ,讨论了西南地区膨胀土 (岩 )湿化层与风化层的区别与联系 ,对湿化层的分区层厚及物理力学性质进行了研究     

水翼艇最佳控制研究

本文探讨了最佳控制在水翼艇姿态控制上的应用,使用数字机对全浸式水翼艇的控制进行辅助设计和闭路仿真。初步结果表明:基于现代控制理论设计的自动驾驶仪,可以取得显著优于古典控制的控制效果。对所论最佳控制系统的实现,本文提出并论证了一种切实可行的水翼艇分级-分散微处理机控制方案。     

Level and attitude control of the active suspension system with integral and derivative action

A 7-DOF full-car model with optimal active control suspension is utilized to evaluate the vehicle dynamic performances which are achieved through proposed controllers. The optimal controller, which includes the integral action for the suspension deflection, considerably improves the attitude control of a vehicle because the rolling and pitching motion in cornering and braking maneuvers are reduced, respectively. In the viewpoint of level control, the integral control acting on the suspension deflection results in the zero steady-state deflection in response to static body forces and ramp road input. The dynamic characteristics of the suspension control system are evaluated in terms of time domain and frequency domain. The simulations in the time domain demonstrate the advantages of the active suspension system obtained by penalizing the integral and derivative of suspension deflections and the derivative of roll and pitch angles in the performance index. The frequency characteristic curves obtained by simulations regarding integral action or derivative action show the increase of both ride comfort and road-holding performances by maximizing the use of suspension deflections. The potential of derivative control is shown by the performances of the car traveling over a bump and braking.     

封闭舱室环境空气中低浓度挥发性脂肪酸分析

对舰艇舱室封闭环境中的挥发性脂肪酸进行检测,建立低浓度挥发性脂肪酸采样、预处理和分析方法。采用硅胶吸附剂对航行中某潜艇封闭舱室的挥发性脂肪酸进行浓缩富集,超纯水超声解吸后用气相色谱-氢火焰离子化检测器(GC-FID)检测。定量检测了6种挥发性脂肪酸,舱室中挥发性脂肪酸的总浓度在3.8~97.5 ppb之间,舱室中检出频次最多的为乙酸,其次为丙酸,异丁酸、异戊酸和正戊酸在部分舱室中偶有检出,其中正丁酸均未检出。由于这些组分的嗅阈值普遍较低,这些组分的存在对舱室环境气味环境的影响不容忽视。通过该方法可以定量测定舰艇舱室封闭环境中的低嗅阈值、低浓度的挥发性脂肪酸化合物,检出限低,灵敏度高,是目前比较可靠的舰艇舱室大气检测方法。