2009年美国市场新车技术概览（下）

当我们提到进口汽车品牌（译者注：这里指在美国市场）时，往往会想到燃油经济性，因为这是市场上进口车型获得赞誉的法宝，也是经济型车辆占据主流的原因。但2009年的进口车型系列看起来却更像是各品牌、各档次车型的群星荟萃，这表明经济型车辆之外的车型也多少进入了美国车市的主流，如KIa（起亚）这样的曾经被视为低价位经济型轿车的制造商也将于2009年推出的新款Borrego，装备了38LV6发动机并可选装4．6LV8发动机，是具有非承载式车身的中型SUV车型；现代汽车公司将于2009年推出的一款豪华运动型轿车——Genesis。     

Th-derived particulate organic carbon fluxes in the northern Barents Sea with comparison to drifting sediment trap fluxes

Large-volume sampling of ²³⁴Th was conducted to estimate particulate organic carbon (POC) export in conjunction with drifting sediment trap deployments in the northern Barents Sea in July 2003 and May 2005. ²³⁴Th-derived POC fluxes averaged 42.3 ± 39.7 mmol C m^− 2 d^− 1 in 2003 and 47.1 ± 30.6 mmol C m^− 2 d^− 1 in 2005. Sediment trap POC fluxes averaged 13.1 ± 8.2 mmol C m^− 2 d^− 1 in 2003 and 17.3 ± 11.4 mmol C m^− 2 d^− 1 in 2005, but better reflected the transient bloom conditions that were observed at each station within a season. Although ²³⁴Th fluxes agreed within a factor 2 at most stations and depths sampled, sediment trap POC fluxes were lower than large-volume POC flux estimates at almost every station. This may represent an under-collection of POC by the drifting sediment traps or, conversely, an over-collection of POC by the large-volume sampling of ²³⁴Th. It is hypothesized that the offset between the two methods is partly due to the presence of the prymnesiophyte Phaeocystis pouchetii, which potentially causes a large variation in > 53-μm POC/²³⁴Th ratios. Due to the large proportion of dissolved carbon or mucilage released by P. pouchetii, and because it is thought that P. pouchetii does not contribute significantly to the vertical export of biogenic matter in the Barents Sea, the application of large-volume sampling of ²³⁴Th may yield relatively high, and possibly inaccurate POC/²³⁴Th ratios. Hence, POC fluxes derived from ²³⁴Th sampling may be inappropriate and drifting sediment traps might be a more reliable method to measure the vertical export of biogenic matter in regions that have recurrent P. pouchetii blooms, such as the Barents Sea.     

Large-scale network partitioning for decentralized traffic management and other transportation applications

For numerous large-scale engineering and science problems, domain decomposition (DD) has generally been accepted by research communities as among the most attractive methods to obtain solutions efficiently. As a prerequisite for the DD solution process, a large domain must be partitioned into several smaller subdomains, with the key to success (of any DD partitioning algorithm) being the number of system boundary nodes. The lower this number, the more efficiently the subdomains can be processed. Although various transportation researchers have hinted at the use of DD, for example, in intelligent transportation systems-enabled decentralized traffic management, it is assumed that the partition is given. This article presents a simple, efficient, and effective algorithm to decompose a transportation network into a predefined number of interconnected subdomains such that the number of system boundary nodes is small (first priority) and the number of nodes in each subdomain is of similar size (second priority). To assess the effectiveness (in terms of minimizing the number of system boundary nodes) of the proposed Shortest Distance Decomposition Algorithm, it is compared with METIS version 5.1.0, currently among the most widely used graph partitioning algorithms worldwide. Using large-scale, real-world transportation test networks, it was found that the Shortest Distance Decomposition Algorithm is better than METIS in 21 of the 27 examples tested; on average, it provided (approximately) 42.0% of the system boundary nodes (as compared to METIS results) in our large-scale examples.     

Estimating bus run times for new limited-stop service using archived AVL and APC data

In recent years, several transit agencies have been trying to be more competitive with the automobile to attract choice riders. Transit agencies can only be competitive if they can provide services that are reliable, have a short access and egress time, and have run times that are comparable to automobiles. Several transit agencies try to be competitive through offering faster service, such as limited-stop (express) bus service. This study uses AVL and APC data, in addition to a disaggregate data obtained from a travel behavior survey, to select stops and estimate run times for a new limited-stop service that will run parallel to a heavily used bus route (67 Saint-Michel) in Montréal, Canada. Three different scenarios are developed based on theory and practice to select stops to be incorporated in the new limited service. The time savings for each scenario are then evaluated as a range and a fourth scenario is developed. A limited-stop service is recommended based on selecting stops serving both directions of the route, major activity points and stop spacing. This study shows that implementing a limited-stop service would yield substantial time savings for both, the new limited service and the existing regular service running in parallel.     

The measure of all things: reflections on changing conceptions of the individual in travel demand modeling

Transportation demand modeling has evolved in scope, theory, and practice in the many decades since the US Bureau of Public Roads pioneered home interview transportation studies in metropolitan households in the early 1940s. The major currents of these developments are discussed in the present paper through consideration of the changing role of the individual—as a source of data, as a unit of analysis, and as the intended beneficiary. In addition to reviewing this history we raise, but are unable to resolve, a growing current concern, namely how the public interest can be best served when the transportation data of greatest value is collected by private entities.     

Exploration of route choice behavior with advanced traveler information using neural network concepts

A model of driver's route choice behavior under advanced traveler information system (ATIS) is developed based on data collected from learning experiments using interactive computer simulation. The experiment subjected drivers to 32 simulated days in which they were to choose between the freeway or a side road. A neural network model is used as a convenient modeling technique in this initial phase of the analysis. The results indicated that most subjects made route choices based mainly on their recent experiences. It was also demonstrated that route choice behaviors are related to the personal characteristics as well as the characteristics of the respective routes. Travel experiences have less effect on the choice of the side road compared to the freeway and the results indicate that the prediction accuracy of the model, the acceptance rate of advice, and the quality of advice are closely correlated. The model developed here was for advice consistently provided at a level of 75 percent accuracy. The paper concludes with a discussion of experimental limitations and suggestions for future research.     

2008年美国市场新车技术概览（下）

本文介绍美国汽车市场上的从欧洲、亚洲进口的最新车型,以便我们了解美国汽车市场的最新动态。 基于轿车基础上的越野车型的市场（指美国市场）已经形成,汽车厂商们便纷纷对原有车型进行改进并不断推出新车型以满足市场的需求。因此,2008年出现了很多全新的此类进口车型。     

2009年美国市场新车技术概览（上）

本文译自美国《MOTOR》杂志,是对2009美国汽车市场新车型所做的技术预览。通过本文,读者可以了解全球汽车最新技术及发展趋势。考虑到目前能源价格是人们关注的焦点,所以2009年度新上市车型的关键词是：燃油经济性。美国国内的汽车制造商也在为此不断努力,并取得了长足的进步和成就。     

Can bus really be the new tram?

BRT appears to be less expensive to build and operate than tram systems but can it really approach the performance level of a tram system and what is the environmental performance of comparable systems?