应用频率调制技术减小开关电力变换器的电磁干扰

频率调制技术已应用于减小数百兆赫兹工作频率的数字系统时钟所产生的电磁干扰(EMI).它的工作原理是:通过对初始固定时钟频率进行调制,将单次谐波的能量驱散至某个频带,从而降低处于谐波频率的EMI幅值.当今,随着电力变换器开关频率的提高,应用相关技术来减少开关电源电路的EMI是值得研究的课题.文章提出了利用相应的调制函数进行频率调制的理论基础,分析了不同调制方案及参数情况下减少EMI发射的效果,并且和其他随机调制法进行了比较.用降压变换器对该方法进行了验证试验.此外还对最佳调制函数和参数进行了简要的讨论.     

新导航概念：连线导航

最近的热点话题：连线导航（Connected Navigation）。在大家的讨论中，“连线”指的是以有通信功能的SIM卡为基础，通过实时双向连线，让用户得到实时动态信息。譬如道路拥挤状况、天气预报等。目前导航厂家们忽略了深入思考：连线导航应用是否是车主用户所需要的？导航仪上必须有无线通信（Telematic）的功能，才能接收实时交通信息。且不论车主们是否愿意为此功能付费，那些已有导航仪的车主是否愿意再买一台有通信功能的导航仪，     

Effect of advanced traveler information systems and road pricing in a network with non-recurrent congestion

The effect of the application of advanced transport information system (ATIS) and road pricing is studied in a transportation system under non-recurrent congestion. A stochastic network deterministic user equilibrium model (SNDUE) with elastic demand is formulated and used to evaluate the welfare and private impacts of different market penetrations of ATIS, together with road pricing for a simple network. Both marginal first-best road pricing and a second-best fixed road pricing are considered. The incentives of private users to use ATIS are analyzed and the characteristics of optimum tolls as a function of ATIS market penetration are shown. We conclude that ATIS is an efficient and necessary tool to reduce the effects of non-recurrent incidents in a transportation network, especially when non-recurrent congestion causes a significant deterioration of operational conditions of the network. If the impact of non-recurrent incidents on free flow costs is small or is reduced only to congestion effects, the use of road pricing would be more efficient. Social benefits obtained when jointly implementing ATIS and road pricing are practically the same whether first-best or second-best road pricing is used. Considering the private costs perceived by the network users, and the benefits experienced by equipped users, the maximum level of market penetration achieved could be limited because private benefits disappear after certain market penetration is obtained.     

中国动态交通信息服务如何才有出路？

虽然中国导航电子地图及导航市场迅猛发展，动态交通信息服务已提上议事日程，但发展仅集中于中国几个重点城市，且信息资源缺乏整合，行业分工不明确，一直未出现全国统一标准的交通信息服务者，服务质量难以满足市场需求。在纷杂混乱的局面下，中国动态交通信息服务如何才有出路？本人有以下一些考虑：     

瑞士联邦铁路货运公司Re484机车扩展了TRAXX机车平台

由于机车设计平台的协同作用,仅在短时间内就开发了新型多电流制机车并获得了国家的批准.新加入的是直流路网中用斩波器和中间电路电压可调的功率变换装置.TRAXX机车的自动停车装置的设计适合于所有欧洲国家和走廊.     

A Low-Cost Transfer Function Identification Technique for Automotive Suspensions

An alternative technique for identifying the transfer function of automotive suspension systems is presented in this paper. The method establishes a frequency response from which the transfer function can be determined by using a low cost test rig developed for the purpose. This results in a transfer function matrix which can include asymmetry in the suspension, tyre stiffness and damping. The technique is validated by comparing results for a two-wheeled trailer with those obtained on a conventional hydraulic test rig. Results from this procedure may be used to evaluate passive or active suspension systems or to feed into a suspension modelling process for such purposes as active suspension control strategy development.     

Increasing the capacity of an isolated merge by metering its on-ramp

Measurements taken downstream of freeway/on-ramp merges have previously shown that discharge flow diminishes when a merge becomes an isolated bottleneck. By means of observation and experiment, we show here that metering an on-ramp can recover the higher discharge flow at a merge and thereby increase the merge capacity. Detailed observations were collected at a single merge using video. These data revealed that the reductions in discharge flow are triggered by a queue that forms near the merge in the freeway shoulder lane and then spreads laterally, as drivers change lanes to maneuver around slow traffic. Our experiments show that once restrictive metering mitigated this shoulder lane queue, high outflows often returned to the median lane. High merge outflows could be restored in all freeway lanes by then relaxing the metering rate so that inflows from the on-ramp increased. Although outflows recovered in this fashion were not sustained for periods greater than 13 min, the findings are the first real evidence that ramp metering can favorably affect the capacity of an isolated merge. Furthermore, these findings point to control strategies that might generate higher outflows for more prolonged periods and increase merge capacity even more. Finally, the findings uncover details of merge operation that are essential for developing realistic theories of merging traffic.     

走出导航电子地图“活”得如何？

电子地图走进中国人们的生活，是伴随着GPS汽车导航而来的。经过几年的发展，电子地图的应用，已经远远超出了汽车导航的范围，逐渐渗透到通讯、网络、数码IT、救援监控等领域。那么，离开汽车导航产业的电子地图，又生存得如何呢？ “网络电子地图搜索”的火爆程度不亚于汽车导航，很多网友即使没有经常使用，但肯定使用过或知道网络电子地图搜索。     

A statistical investigation of time-variant hull girder strength of aging ships and coating life

Risk- and reliability-based approaches are increasingly being applied in assisting inspection and maintenance planning. One of the keys to such approaches is properly predicting the hull girder strength (HG) of gradually degradated hull structures. The development has been limited by the lack of data on aging ships—validation of the developed methods has not been possible. To fill the gap of knowledge on hull strength of ships in service, this paper presents a database of as-gauged hull structures and a statistical study of the time-variant HG of tankers. The expanded data set was collected from 2195 as-gauged girth belts (transverse sections) of 211 single-hull tankers that were 12–32 years old. It was intended to (1) provide actual data on hull girder section modulus (HGSM) of tankers, (2) investigate the general trends of the change in the HG over ships’ service life, and (3) propose formulations for presenting time-variant HGSM and coating life.

The data set demonstrated a high variation of HGSM that changed over time. The mean value and standard deviation of HGSM loss were derived as functions of time. The probability density function (pdf) of coating life was also derived. Comparisons were made between previous studies on HG and the current data set. It was found that almost all previous studies showed much greater HG loss than what this database revealed. The refinement of existing calculations appears to be needed. The data set and statistical study were expected to form the basis for validating formulations of HG that are key components in risk- and reliability-based approaches.     

Characterizing European high speed train stations using intermodal time and entropy metrics

This paper presents a quantitative method for characterizing high speed train stations in terms of passenger intermodality. The aim of the procedure is two-fold: firstly, the method is to be used as an objective measure for comparing stations in order to detect suboptimal points and improve the performance of stations as nodal points; secondly, the method provides a means to embed intermodality into regional accessibility models, allowing comprehensive modelling at lower scales. The empirical base of the work comprises data from 27 European high speed rail stations, which is deemed an appropriate statistical sample for the whole European rail network. Using the entropy metric, we found that several different patterns emerged: there was a clear hierarchy of stations which was linked to their respective roles within the system, while strong constraints impeded stations from performing optimally as true intermodal nodes.