Developing a CFD heat transfer model for applying high expansion foam in an LNG spill

Liquefied natural gas (LNG) is widely used to cost-effectively store and transport natural gas. However, a spill of LNG can create a vapor cloud, which can potentially cause fire and explosion. High expansion (HEX) foam is recommended by the NFPA 11 to mitigate the vapor hazard and control LNG pool fire. In this study, the parameters that affect HEX foam performance were examined using lab-scale testing of foam temperature profile and computational fluid dynamics (CFD) modeling of heat transfer in vapor channels. A heat transfer model using ANSYS Fluent® was developed to estimate the minimum HEX foam height that allows the vapors from LNG spillage to disperse rapidly. We also performed a sensitivity analysis on the effect of the vaporization rate, the diameter of the vapor channel, and the heat transfer coefficient on the required minimum height of the HEX foam. It can be observed that at least 1.2 m of HEX foam in height are needed to achieve risk mitigation in a typical situation. The simulation results can be used not only for understanding the heat transfer mechanisms when applying HEX foam but also for suggesting to the LNG facility operator how much HEX foam they need for effective risk mitigation under different conditions.     

“西-宝”高速公路不良气象条件分析及对策

依据近40年的气象资料,对西宝高速公路沿线大雾、降雨、降雪、雷暴、低温、高温、沙尘等灾害性天气进行了分析,得出了沿线各种灾害性天气特征,并对其原因进行了简单分析。分析了这些灾害性天气对高速交通的影响程度,指出西宝高速公路气象服务的关键期,提出了避免不良天气造成交通事故发生的具体措施。     

Exploring the effects of state highway safety laws and sociocultural characteristics on fatal crashes

Objective: Distinguished from the traditional perspectives in crash analyses, which examined the effects of geometric design features, traffic factors, and other relevant attributes on the crash frequencies of roadway entities, our study focuses on exploring the effects of highway safety laws, as well as sociocultural characteristics, on fatal crashes across states.

Methods: Law and regulation related data were collected from the Insurance Institute for Highway Safety, State Highway Safety Offices, and Governors Highway Safety Association. A variety of sociodemographic characteristics were obtained from the U.S. Census Bureau. In addition, cultural factors and other attributes from a variety of resources are considered and incorporated in the modeling process. These data and fatal crash counts were collected for the 50 U.S. states and the District of Columbia and were analyzed using zero-truncated negative binomial (ZTNB) regression models.

Results: The results show that, in law and regulation–related factors, the use of speed cameras, no handheld cell phone ban, limited handheld cell phone ban, and no text messaging ban are found to have significant effects on fatal crashes. Regarding sociocultural characteristics, married couples with both husband and wife in the labor force are found to be associated with lower crash frequencies, the ratios of workers traveling to work by carpool, those driving alone, workers working outside the county of residence, language other than English and limited English fluency, and the number of licensed drivers are found to be associated with higher crash frequencies.

Conclusions: Through reviewing and modeling existing state highway safety laws and sociocultural characteristics, the results reveal new insights that could influence policy making. In addition, the results would benefit amending existing laws and regulations and provide testimony about highway safety issues before lawmakers consider new legislation.     

Gaseous emissions from compressed natural gas buses in urban road and highway tests in China

The natural gas vehicle market is rapidly developing throughout the world, and the majority of such vehicles operate on compressed natural gas(CNG). However, most studies on the emission characteristics of CNG vehicles rely on laboratory chassis dynamometer measurements, which do not accurately represent actual road driving conditions. To further investigate the emission characteristics of CNG vehicles, two CNG city buses and two CNG coaches were tested on public urban roads and highway sections. Our results show that when speeds of 0–10 km/hr were increased to 10–20 km/hr, the CO_2, CO, nitrogen oxide(NO_x), and total hydrocarbon(THC) emission factors decreased by(71.6 ± 4.3)%,(65.6 ± 9.5)%,(64.9 ± 9.2)% and(67.8 ± 0.3)%, respectively. In this study, The Beijing city buses with stricter emission standards(Euro Ⅳ) did not have lower emission factors than the Chongqing coaches with Euro Ⅱ emission standards. Both the higher emission factors at 0–10 km/hr speeds and the higher percentage of driving in the low-speed regime during the entire road cycle may have contributed to the higher CO_2 and CO emission factors of these city buses. Additionally, compared with the emission factors produced in the urban road tests, the CO emission factors of the CNG buses in highway tests decreased the most(by 83.2%), followed by the THC emission factors, which decreased by 67.1%.     

区域大气污染物总量控制技术与示范研究

分析了我国的大气环境问题和特征,剖析了大气污染的成因;重点介绍了区域大气污染物总量控制技术研究中,大气污染物排放清单的编制技术,多尺度的空气质量模拟技术,基于现代控制理论的大气环境容量优化技术,基于环境容量和排放绩效的总量分配技术,多种总量监控方法,科学有效的总量控制管理机制和规则等的关键技术、技术突破、主要研究与理论创新及成果的应用与示范;紧密结合国家空气环境质量管理和大气污染控制的需要,提出了我国大气环境管理、政策和大气环境科学研究的建议.      

Soil compaction--indicators for the assessment of harmful changes to the soil in the context of the German Federal Soil Protection Act

Soil compaction in agriculture induced by large-scale equipment is of growing concern. Heavy wheel loads used in arable cropping have the potential to cause irreversible damage to the subsoil structure and may lead to harmful soil compaction. In order to sustain or improve soil health or fitness on a sustainable basis, indicators are needed to assess the changes in the soil structure and the respective soil functions. This requires an adequate verification of methods for distinguishing between the impairment of soil structure and the disruption of soil functions, and for the respective subject of protection. In this article the link between existing models of soil physical prognosis, practical guidelines, and criteria for the identification of affected soil structure is demonstrated, and a viable concept to distinguish harmful changes to the soil is presented. The concept consists of methods for soil physical analysis such as "pre-compression stress" and "loading ratio", practical recommendations for best management practice, and an indicator-based model for the identification of harmful subsoil compaction derived from a research project for the German Federal Environmental Agency, making it possible to determine for a respective location the required level of action far beyond the common practice of precautions against harmful soil compaction.     

公路建设中水土流失影响及防治措施

公路建设中造成的水土流失越来越严重，水土流失范围呈线状，常常跨越多个流域和地貌类型，因此影响范围较广，且在公路的不同部位水土流失的程度不同，影响期限不同。在实际调查的基础上分析公路建设中水土流失的原因，并提出计算方法及一般性防护措施。     

青藏公路格拉段垃圾污染现状及治理对策

在对青藏格拉段沿线垃圾污染现状进行全面分析的基础上，提出了通过加强环境卫生意识的宣传教育和管理，推行污染者付费制度，采用站点垃圾集中堆放、定期清运等措施来避免青藏公路沿线站点的垃圾污染。     

Can David and Goliath Get Along? Federal Land in Local Places

It is often unclear what the role of a local jurisdiction is with regard to land use management on nearby federal properties. Yet federal lands clearly impact nearby local communities. The US Department of Energy (DOE), with over 100 sites across the United States with varying degrees of environmental contamination, may be in a very difficult position with regard to relationships with local government about land use. Yet few, if any, studies have examined DOE land use issues. This study asks: (1) In general, how do local planners feel about federal government relationships with them? (2) Do local planners feel differently about the DOE than they do about other federal agencies? (3) What reasons explain any differences observed in answer to the second question? To answer these questions, local planners were interviewed from communities adjacent to non-DOE federal properties, and their responses compared to those of planners located near DOE facilities in the same regions. Findings showed that compared to other federal agencies that own land in the same regions, the DOE is relatively poorer at actively involving local officials in land use decisions at its sites. Primary reasons are the historic legacy of a culture of secrecy, focus on mission, and especially the lack of experience, training, or mandates in local planning cooperation. Findings also suggest that this attitude is markedly stronger in areas west of the Rocky Mountains. Recommendations for improved federal–local communications include the development of a vision for local government involvement that is supported by top levels of management and filtered effectively to the site level.