The suitability of hedonic models for cost-benefit analysis: Evidence from commuting flows

We compare two estimates of benefits arising from the construction of new bridges in south-west Norway. One estimate comes from a hedonic property value model. Rather than follow an approach which is strictly theoretically correct, we adopt Rosen’s simple first-stage approach. To investigate and validate whether this simplified approach gives a reasonable estimate, we compare it to an estimate derived from a travel demand model. We find that a variant of an ex post hedonic house price model gives very similar estimates to the estimates from the travel demand model. This supports a hypothesis that the simplistic hedonic approach is reasonable.     

溴化锂制冷机环保性分析

介绍了直燃式溴化锂吸收式制冷机的制冷原理和特点,其具有能源利用率高、消耗电量是相同制冷量的电力空调的23%、使用的制冷剂不会破坏大气臭氧层、噪音低等优点,与电力空调相比,溴化锂空调在环保、节能方面有着无可比拟的优越性。     

基于知识的原油运输船港航系统的评价决策模型及分析

我国原油进口是一项长期的国家战略,原油进口量逐年增长,原油进口的的海运需求相当大,所以需要科学合理的原油运输系统的论证、设计和建设。本文从原油运输船型的发展和趋势出发,运用基于知识的最短路径模型,结合综合必要费率对包含船、港、航和货值的原油运输系统经济性进行了计算和分析,从而选择合理的原油运输船型和专用码头的合理吨位。     

建立上海国际航运中心的研究

在上海建立国际航运中心，是尽快把上海建成国际经济、贸易、金融中心的重要组成部分，两者相辅组成。该文对建立国际航运中心的必要性与可能性，基本功能与特征，存在问题，发展目标与建设步骤，从理论上与实际上进行了分析，在此基础上，提出了符合国际经济发展方向、并且有可操作性的结论与建议。     

浅述过水侧石在天津临港经济区清河道道路设计中的应用

多年以来,我国的城市道路建设均使用城市地下雨水管道收集路面雨水,这种方法破坏了原有的雨水循环系统,产生了很多问题。在临港经济区清河道的道路设计中,因地制宜地设计了一种过水侧石,既不破坏原来的雨水循环系统,又极大地降低了工程量。详细介绍这种过水侧石在清河道道路设计中的应用。     

接触网雷击跳闸率的新算法

结合接触网的受雷情况和结构特点建立接触网的雷击模型,分别给出线路遭受直接雷击和感应雷击时接触网的耐雷水平计算公式。基于广义积分法,提出计入感应雷击的计算接触网雷击跳闸率的方法。以常见的复线接触网为例,按照给出的模型和计算方法计算接触网的跳闸率,并将计算结果与实际情况比较。研究结果表明:接触网遭受感应雷击时的耐雷水平较低,因感应雷击造成的接触网雷击跳闸次数占总雷击跳闸次数的31.6%,感应雷击对接触网的跳闸影响是明显的;计入感应雷击计算的总跳闸次数更接近实际运行值。     

Optimal funding allocation strategies for safety improvements on urban intersections

Urban intersections crashes cause significant economic loss. The safety management process undertaken by most states in the United States is referred to as Highway Safety Improvement Program and consists of three standardized steps: (i) identification of critical crash locations, (ii) development of countermeasures, and (iii) resource allocation among identified crash locations. Often these three steps are undertaken independently, with limited detail of each step at the state planning agencies. The literature review underlines the importance of the third step, and the lack of sophisticated tools available to state planning agencies for leveraging information obtained from the first two steps. Further, non-strategic approaches and unavailability of methods for evaluating policies may lead to sub-optimal funding allocation. This paper overcomes these limitations and proposes multiple optimal resource allocation strategies for improvements at urban intersections that maximize safety benefits, under budget and policy constraints. Proposed policy measures based on benefits maximization (economic competitiveness), equitable allocation (equity), and relaxation of mutually exclusiveness (multiple alternatives at one location) produce significantly different alternative and fund allocation. The proposed models are applied to selected intersections in four counties of southeast Michigan. Results reinforce the applicability of the strategies/policies and tools developed in this paper for safety project funding allocation on critical urban intersections.     

地铁车站直接蒸发式空调解决方案探讨

直接蒸发式空调系统以节能、占地小、控制灵活等特点多用于中小型建筑,地铁车站空调的冷量规模和空气末端的数量具备采用直接蒸发空调机组的条件,针对该系统应用于地铁车站进行具体分析,根据地铁车站特点,对冷却水系统进行优化整合,提出整体配置方案,从空气处理过程、制冷压缩循环、系统运营成本、土建和设备初投资等方面与常规空调系统进行对比分析。结果表明:该系统具有一定的优势,同时也指出了其存在的缺点和局限性;在设计中应根据具体工程的特点判断是否采用该系统。直接蒸发式空调系统作为一种运行节能、投资节省的空调方式,可以为地铁工程空调系统设计提供一种新的思路和参考。     

基于运量的国民经济效益网络计算法

通过对现行国民经济效益计算方法的研究,运用交通分配理论论证了现行计算方法中运量分析存在的问题。依据交通分配理论和消费者剩余理论,将交通建设项目吸引区内整个路网作为研究对象,建立了基于运量的国民经济效益网络计算法。实例计算表明该方法的有效性。     

Numerical investigation of turbulence near a sheared air–water interface. Part 1: Turbulence statistics beneath a flat water surface sheared by wind

Direct numerical simulation (DNS) and large eddy simulation (LES) of turbulent shear flow beneath a flat water surface with imposed wind shear stress are presented. The results of DNS indicate that there are clear differences, and also similarities, between wind-driven flow and the flow near a solid wall. The qualitative structures of turbulence are similar in both types of flow. Low-speed streaks are also present in wind-driven flow. On the other hand, profiles of the mean velocity and turbulence intensities in wind-driven flow are significantly different from those in flow near a solid wall. The differences are attributed to the lack of a viscous sublayer, and to the boundary condition which allows fluctuations of the tangential velocity components at the boundary. LES of the same flow was also carried out to evaluate subgrid-scale models. It was shown that the features of the flow observed in DNS are well simulated by all models tested, and that the discrepancies between DNS and LES with the dynamic mixed model are very small. Received: August 17, 2000 / Accepted: December 22, 2000