Concentrations of ultrafine particles at a highway toll collection booth and exposure implications for toll collectors

Research regarding the magnitude of ultrafine particle levels at highway toll stations is limited. This study measured ambient concentrations of ultrafine particles at a highway toll station from October 30 to November 1 and November 5 to November 6, 2008. A scanning mobility particle sizer was used to measure ultrafine particle concentrations at a ticket/cash tollbooth. Levels of hourly average ultrafine particles at the tollbooth were about 3-6 times higher than those in urban backgrounds, indicating that a considerable amount of ultrafine particles are exhausted from passing vehicles. A bi-modal size distribution pattern with a dominant mode at about < 6 nm and a minor mode at about 40 nm was observed at the tollbooth. The high amounts of nanoparticles in this study can be attributed to gas-to-particle reactions in fresh fumes emitted directly from vehicles. The influences of traffic volume, wind speed, and relative humidity on ultrafine particle concentrations were also determined. High ambient concentrations of ultrafine particles existed under low wind speed, low relative humidity, and high traffic volume. Although different factors account for high ambient concentrations of ultrafine particles at the tollbooth, measurements indicate that toll collectors who work close to traffic emission sources have a high exposure risk.     

号码携带现场试验业务管理相关问题的研究

主要介绍了我国实施号码携带业务现场试验时,所确定的号码携带业务管理相关方面的规定,以及我国对管理相关问题的分析和考虑。     

号码携带接口协议测试工具的功能需求研究

从当前对号码携带接口协议进行验证测试的实际需求出发,通过深入地分析号码携带接口协议的特点,掌握该协议与其它协议之间的共性及特性,从而有针对性地提出了适用于检验该协议测试工具的功能架构以及功能需求。     

Does remediation save lives? — On the cost of cleaning up arsenic-contaminated sites in Sweden

Sweden has only just begun remediation of its many contaminated sites, a process that will cost an estimated SEK 60,000 million (USD 9100 million). Although the risk assessment method, carried out by the Swedish EPA, is driven by health effects, it does not consider actual exposure. Instead, the sites are assessed based on divergence from guideline values. This paper uses an environmental medicine approach that takes exposure into account to analyse how cancer risks on and near arsenic-contaminated sites are implicitly valued in the remediation process. The results show that the level of ambition is high. At 23 contaminated sites, the cost per life saved varies from SEK 287 million to SEK 1,835,000 million, despite conservative calculations that in fact probably underestimate the costs. It is concluded that if environmental health risks are to be reduced, there are probably other areas where economic resources can be used more cost-effectively.     

我国号码携带业务访问数据库技术方案的研究

主要对我国在试验期间网间移动号码携带访问数据库的技术方案进行了研究和分析,包括不同业务如何确定访问数据库的运营商网络,以及运营商网内访问数据库的方式。但任何一种方案都不是完美的,不可能同时满足所有运营商的要求。目前只能站在整个行业的角度,暂时确定了一个试验阶段的技术方案。将来再根据实际情况,考虑未来开展号码携带时的技术方案。     

Mobile web for under-privileged in developing countries

In developing nations, Internet infrastructure in scarce; however, majority of people in developing countries also need access to information that matter for their daily life and livelihood. As cost of computers are higher than mobile phones and infrastructure for running computers by stable electricity is not widely available at many places of under developed and developing (hence, referred as developing) countries. One of the major options for under-privileged people in developing countries to access information is through mobile phone. A mobile device with GPRS for access to Internet services is still expensive for a common man to afford in developing countries. Therefore, to offer mobile web for the developing countries, we need to look at SMS (Short Message Service) as transport bearer, which is cheaper and can support most of the actionable services (many important services which needs a few bytes to exchange the information). SMS as transport bearer has one constraints – it does not interoperate (i.e., a user belong to one service provider is not able to access services by SMS-data of another service provider). In this paper, we propose a routing algorithm that makes SMS-data interoperable. We also propose architecture for mobile web over SMS as transport bearer for seamless application access in roaming, number portability, and vehicular condition. Substantial researches have been done on performance of TCP/IP for wireless web that mainly focused on three applications viz., file transfer, Electronic mail, and World Wide Web. This paper presents performance of actionable information through online transaction over TCP/IP and SMS under similar conditions; it shows SMS is not at a disadvantage compared to TCP/IP.     

Vertical variations of particle number concentration and size distribution in a street canyon in Shanghai, China

Measurements of particle number size distribution in the range of 10-487 nm were made at four heights on one side of an asymmetric street canyon on Beijing East Road in Shanghai, China. The result showed that the number size distributions were bimodal or trimodal and lognormal in form. Within a certain height from 1.5 to 20 m, the particle size distributions significantly changed with increasing height. The particle number concentrations in the nucleation mode and in the Aitken mode significantly dropped, and the peaking diameter in the Aitken mode shifted to larger sizes. The variations of the particle number size distributions in the accumulation mode were less significant than those in the nucleation and Aitken modes. The particle number size distributions slightly changed with increasing height ranging from 20 to 38 m. The particle number concentrations in the street canyon showed a stronger association with the pre-existing particle concentrations and the intensity of the solar radiation when the traffic flow was stable. The particle number concentrations were observed higher in Test I than in Test II, probably because the small pre-existing particle concentrations and the intense solar radiation promoted the formation of new particles. The pollutant concentrations in the street canyon showed a stronger association with wind speed and direction. For example, the concentrations of total particle surface area, total particle volume, PM2.5 and CO were lower in Test I (high wind speed and step-up canyon) than in Test II (low wind speed and wind blowing parallel to the canyon). The equations for the normalized concentration curves of the total particle number, CO and PM2.5 in Test I and Test II were derived. A power functions was found to be a good estimator for predicting the concentrations of total particle number, CO and PM2.5 at different heights. The decay rates of PM2.5 and CO concentrations were lower in Test I than in Test II. However, the decay rate of the total particle number concentration in Test I was similar to that in Test II. No matter how the wind direction changed, for example, in the step-up case or wind blowing parallel to the canyon, the decay rates of the total particle number concentration were larger than those of PM2.5 and CO concentrations. For example, CO concentrations decreased by 0.33 and 0.69 at the heights ranging from 1.5 to 38 m in Test I and Test II, while the total particle number concentrations decreased by 0.72 and 0.85 within the same height ranges in Test I and Test II. It is concluded that the coagulation process, besides the dilution process, affected the total particle number concentration.     

高密度电法外接电源轻便化改进的探讨

本文用层叠电池构建电池模块,利用串联增压、并联增流的原理将模块组合成电源来取代过去给高密度电法仪供电的1#电池电源,达到从体积和重量上轻便化的目的。通过对比试验分析,该新电源可以达到与老电源相同的测试效果,但在体积和重量上得到明显降低,减轻了山区线路勘察中高密度电法电源笨重的问题,并节约了劳务成本。     

基于低雷诺数κ-ε模型冲击射流传热的数值模拟

冲机射流在机翼除霜、电子元器件散热等工程领域应用广泛,为进一步研究其传热机理,利用两种低雷诺数κ-ε模型对单股冲击射流的传热进行数值模拟,并与标准κ-ε模型及雷诺应力模型的计算结果进行对比。结果表明,低雷诺数κ-ε模型在两种工况下的计算结果均优于其他模型。湍流热扩散系数作为求解温度场最重要的参数,对传热的计算结果影响极大,通常用湍流普朗特数作为常数求解。在低雷诺数κ-ε模型的基础上,分别通过湍流普朗特数函数求解和t2-εt方程直接求解进行改进,并将计算结果进行比较。结果表明,使用湍流普朗特数函数形式求解湍流热扩散系数能给出更好的预测结果,直接求解仍需进一步改进。     

高生产率计算系统

以往的高端计算领域将峰值运算速度作为衡量计算系统的最重要的指标.然而体系结构的失衡和落后的编程支持成为困扰高性能计算技术发展的关键问题.未来高端计算的发展方向应该着眼于提高系统的生产率,强调系统的易用性和好用性.介绍了HPCS的背景、目标、主要技术挑战以及主要的解决方案和关键技术.