液化石油气发动机试验研究及发展趋势

介绍了液化石油气 (LPG)汽车发动机国内外研究进展情况 ,并简要介绍了本研究所在这方面所开展的工作 ,重点阐述了LPG汽车发动机的发展趋势以及采用电控LPG缸内直喷技术的优点和意义     

A computerized household activity scheduling survey

Household activity scheduling is widely regarded as the underlying mechanism through which people respond to emerging travel demand management policies. Despite this, very little fundamental research has been conducted into the underlying scheduling process to improve our understanding and ability forecast travel. The experimental survey approach presented in this paper attempts to fill this gap. At the core of the survey is a Computerized Household Activity Scheduling (CHASE) software program. The program is unique in that it runs for a week long period during which time all adult household members login daily to record their scheduling decisions as they occur over time. An up-front interview is used to define a household's activity agenda and mode availability. A sample of 41 households (66 adults and 14 children) was used to assess the performance of the survey. Analysis focuses on times to completion, daily scheduling steps, activity-travel patterns, and scheduling time horizons. Overall, the results show that the computer-based survey design was successful in gathering an array of information on the underlying process, while minimizing the burden on respondents. The survey was also capable of tracing traditionally observed activity-travel outcomes over a multi-day period with minimal fatigue effects. The paper concludes with a detailed discussion on future survey design, including issues of instrument bias, use of the Internet, and improved tracing of spatial behaviour. Future use of the survey methodology to enhance activity-travel diary surveys and stated responses experiments is also discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

金属磁记忆无损检测的研究现状和关键问题

金属磁记忆检测技术自提出以来，便受到了广泛的重视，作为一种新兴的无损检测方法，能够对铁磁材料的应力集中、早期损伤及损伤程度等进行评估。但是，目前的研究多集中于磁记忆检测的板件试验，对磁记忆的物理模型和应力定量化评估方面的研究不够深入。基于此，总结了国内外关于磁记忆效应机理、磁信号影响因素、磁记忆损伤评价参数及基础试验研究方面的研究现状和进展，对金属磁记忆检测技术亟待解决的关键性问题进行了讨论，并指出金属磁记忆检测技术未来的发展趋势。结果表明：由于磁记忆信号的影响因素非常复杂，缺乏系统的试验和理论依据，目前只是停留在初步理论摸索和简单应用上，影响了该技术的量化发展和工程应用；要利用磁记忆检测技术进行应力定量化评估，必须要明确影响磁记忆信号的多种因素及其影响程度；现有的损伤评价参数都只是提取了磁信号的某些特征，并未进行全面的磁信号特征分析，具有一定的局限性；磁记忆技术的试验研究多集中于不同材料性质的静载拉伸试验和疲劳试验，受载形式单一，对构件性质的研究很少，而钢结构中梁、板等主要构件均承受弯剪应力作用。可见，要将磁记忆检测技术应用于钢结构，必须对弯剪应力作用下的构件磁记忆信号变化规律进行研究。     

块石路堤、护坡导热系数的实验研究

讨论了块石路堤、护坡试样在表面温度周期波动时自然对流产生的条件,分析了开放系统和封闭系统块石试样内部的热传输机理,以说明其热扩散系数和导热系数的确定方法。指出开放系统的试样由于传热形式不单一而不利于热扩散系数和导热系统的精确测定,而封闭系统试样内部的传热形式以热传导为主。结果表明,可用封闭系统的细长圆柱试样来测试路堤、护坡块石的热扩散系数和导热系数。     

提高天然气汽车动力性能的研究

提出了一种提高天然气汽车动力性能的方案 ,设计了控制系统及其执行部件 ,从汽油的加浓量、加浓点、减气点、点火提前角度等方面进行了优化试验研究 ;在保持天然气汽车良好排放性与燃料经济性的情况下 ,使天然气发动机的功率由原来不足汽油发动机功率的 80 %提高到 95 %以上。     

土的冲击压实试验研究

介绍了对冲击压实所进行的系列试验研究,研制出了将冲击夯技术应用于大面积连续压实机械的模型,并进行了模型对比试验,得到了满意的结论。     

混凝土泵车冲击载荷对结构动态特性的影响

使用ADAMS软件建立了混凝土泵车臂架系统的动力学仿真分析模型,对泵车臂架系统在不同峰值的油缸冲击载荷下的动态响应进行了详细分析。通过响应分析可知,减小油缸冲击载荷是改善泵车振动性能的有效途径之一。该理论研究结果得到了试验验证。     

Yardsticks on the road: Regulatory contracts and cost efficiency in the Norwegian bus industry

In this paper a cost frontier model is estimated for an eleven-year panel of Norwegian bus companies (1136 company-year observations) using the methodology proposed by Battese and Coelli (1995). The main objective of the paper is to investigate to what extent different type of regulatory contracts affect company performance. The panel model proposed by Battese and Coelli (1995) allow for year/company specific efficiency measures to be estimated. Thus, unobservable network or other time invariant characteristic of the operating environment can be controlled for by analyzing the dynamics of measured productivity across time for firms regulated under different types of contracts, rather than relying solely on variations across companies during one time period. Therefore, the paper offers methodological and data advantages over previous work on this subject. The main and robust result of the paper is that the adoption of a more high-powered scheme based on a yardstick type of regulation significantly reduces operating costs. The results contained in this paper thus confirms theoretical predictions regarding the incentive properties of high powered incentive schemes and in particular the dynamic benefits of yardstick competition.     

波形钢腹板预应力混凝土箱梁的试验研究

为研究波形钢腹板预应力混凝土箱梁这种新型桥梁结构的力学性能,根据国外已建实桥的箱梁尺寸,设计了缩尺模型试验梁。通过测试模型梁在静力荷载作用下的挠度和应变,来分析这种箱梁结构的弯曲、扭转和畸变等力学特性。试验结果表明:在弯曲荷载作用下,波形钢腹板主要承担剪力,而弯矩仅由混凝土顶板和底板来承担,同时箱梁的挠度应计及钢腹板的剪切变形的影响。另外,波形钢腹板预应力混凝土箱梁对偏心荷载作用时产生的扭转变形和畸变的抵抗能力相对较差。波形钢腹板预应力混凝土箱梁具有区别于传统混凝土箱梁结构的的力学特性。     

预应力锚索框架型地梁的内力计算

提出了预应力锚索框架型地梁内力的一种计算方法，即把框架地梁分解成单梁，按温克尔(Winkler)假定计算各单梁的内力，由此进行框架地梁的尺寸和配筋设计。在内力计算中同时考虑框架地梁的锚索张拉阶段和工作阶段。通过实际工程说明了计算方法。