The town that food saved? Investigating the promise of a local food economy in Vermont

Proponents of the local food movement point to its environmental, economic, and social benefits, yet there is little research on the extent to which particular local food projects live up to these promises. Vermont leads the country in farm stands, direct-to-consumer sales, and farmers’ markets per capita and the town of Hardwick, Vermont has received substantial media attention for its growing economy based on new food and agriculture businesses, including being the subject of a book entitled The Town that Food Saved. Using interviews with local food participants and analysis of US Census data, the paper assesses the impact of the local food economy in Hardwick using environmental, economic, and social outcomes. The paper also examines how the agricultural renaissance there has been accepted, resisted, and shaped by local actors. Using Census data, the paper finds that between 2000 and 2016, the unemployment rate in Hardwick remained steady, mean incomes increased, and 296 new jobs have been retained. In addition, the percentage of families in Hardwick with income below the poverty level decreased between 2000 and 2016, and the percentage of families accessing supplemental nutrition assistance program (SNAP) benefits increased. The paper also finds that many participants in the Hardwick food economy have concerns about the accessibility, affordability, and inclusivity of the newer food-based projects there. The paper concludes with a discussion of the ways in which Hardwick fulfils some of the hopes and concerns of the local food movement, and the potential for place-based agricultural development.     

Drivers of Interbasin Transfers in the United States: Insights from Sampling

Interbasin transfers (IBTs) are manmade transfers of water that cross basin boundaries. In an analysis of 2016 data, this work identified 2,161 reaches crossing United States (U.S.) Geological Survey hydrologic unit code 6 boundaries in the U.S. The objectives of this study were to characterize and classify IBTs, and examine the development drivers for a subset of 109 (~5%) of the IBT reaches through examination of samples from different climate regions of the U.S. The IBTs were classified as being near irrigated agricultural lands, near cities, or rural IBTs not near cities or irrigated land. IBTs near both cities and irrigated agricultural land were designated as city + irrigated agriculture. The 109 samples were selected, based on approximate proportional distribution to the total number of IBTs within each climate region, with representation of areas having a high density of IBTs. Analysis of the samples revealed that in the U.S., there have been four major drivers for basin transfers: irrigation for agriculture, municipal and industrial water supply, commercial shipping or navigation, and drainage or flood management. The most common has been drainage or flood management, though IBTs at least partially driven by agricultural needs are also prevalent. The majority of the sampled IBTs were constructed between 1880 and 1980, with peaks in development between 1900–1910 and 1960–1970. The samples also showed the drivers of IBT development evolved over time, reflecting changes in regional economies, populations, and needs.     

The impact of UV treatment on microbial control and DBPs formation in full-scale drinking water systems in northern China

To manage potential microbial risks and meet increasingly strict drinking water health standards, UV treatment has attracted increasing attention for use in drinking water systems in China. However, the effects of UV treatment on microbial control and disinfection by-products (DBPs) formation in real municipal drinking water systems are poorly understood. Here, we collected water samples from three real drinking water systems in Beijing and Tianjin to investigate the impacts of UV treatment on microbial control and DBP formation. We employed heterotrophic plate count (HPC), flow cytometry (FCM), quantitative PCR analysis, and high-throughput sequencing to measure microorganisms in the samples. Different trends were observed between HPC and total cell count (measured by FCM), indicating that a single indicator could not reflect the real degree of biological re-growth in drinking water distribution systems (DWDSs). A significant increase in the 16S rRNA gene concentration was observed when the UV system was stopped. Besides, the bacterial community composition was similar at the phylum level but differed markedly at the genera level among the three DWDSs. Some chlorine-resistant bacteria, including potential pathogens (e.g., Acinetobacter) showed a high relative abundance when the UV system was turned off. It can be concluded that UV treatment can mitigate microbial re-growth to some extent. Finally, UV treatment had a limited influence on the formation of DBPs, including trihalomethanes, haloacetic acids, and nitrogenated DBPs. The findings of this study may help to understand the performance of UV treatment in real drinking water systems.     

一次冷锋过程中我国区域空气污染边界层特征

利用常规地面气象和探空资料、ERA-interim再分析资料、以及全国PM_2.5浓度数据,针对2015年3月7~11日一次冷空气南下的锋面天气过程中,我国华北、华东地区出现的大范围空气污染,开展了高空各层天气形势分析,以及本次过程中污染区域由北至南6个城市（北京、章丘、郑州、南阳、武汉、长沙）边界层气象要素的垂直结构及其时空演变特征的研究.结果表明：在污染前期（3月7~8日）中高纬度500hPa平直的纬向环流和地面均压场,为污染天气的发生和维持以及空气污染物的集聚提供了有利的环流场.污染中期（3月8~10日）冷空气南下,地面冷高压向华东地区移动,重污染区域随冷高压前部的弱低压场或均压场由北向南移动.伴随着天气系统移动,六个地面观测站的边界层特征在时空上表现出相似性,由北向南各站在污染期间先后出现多层逆温,风速较小,逆温层下相对湿度较大.此次多层逆温的形成是由于夜间近地面辐射冷却、冷锋移动过程中产生的锋面逆温以及边界层以上的下沉运动造成的.本研究揭示了在天气系统移动中,位于天气系统相同部位站点的边界层结构具有共同的特征,及其与空气污染的关系.     

超低改造下中国火电排放清单及分布特征

本研究基于2018年火电在线监测和环境统计等数据,自下而上编制了中国高分辨率火电行业排放清单,并核算了排放浓度、排放因子和排放量.结果表明超低排放政策效果显著：2018年火电SO₂、NO_x和烟尘平均排放浓度分别为37.57、56.71和7.41mg ·m^-3.比2015年分别下降58.71%、43.12%和60.79%;中国燃煤机组的SO₂、NO_x和烟尘平均排放因子分别为0.30、0.48和0.06 g ·kg^-1,比2015年分别下降55.2%、36.84%和62.5%;中国火电SO₂、NO_x、烟尘和PM_2.5总排放量分别为72.14、118.38、14.90和13.59万t ·a^-1,比2015年分别下降41.32%、19.29%、48.12%和40.39%.     

基于多流域生态网络模型的用水系统结构特征演化分析

以黄淮海流域为案例,将其涵盖生态环境和社会经济用水的水资源利用系统作为研究对象,构建多流域生态网络模型,从系统整体角度自上而下对其进行描述并开展生态网络分析,通过系统整体分析指标的计算,对黄淮海流域在2003~2014年期间系统结构特征的演化进行了分析.研究结果表明,2003~2014年期间,通过"十一五"、"十二五"规划所开展的多项水资源可持续利用措施的实施,系统受到来自外界环境的压力和干扰有所减小,系统逐渐趋于稳定,但却仍存在着生态用水量严重短缺的问题,系统的可持续性还有待进一步研究和提高.     

Addressing the challenges of implementing safety instrumented systems in multi-product batch processes

Adapting the requirements of IEC 61511 to a batch system can be frustrating, particularly for multi-product units. While a Safety Instrumented System (SIS) for continuous operation is often a straightforward detect-decide-act loop, implementing a SIS for a batch system may involve multiple safety functions, time- or state-dependence, intricate calculations, or complex installations. Relationships between the SIS elements and the basic process control system (BPCS) must be tightly managed, providing both for the safety of the unit and its ability to operate without spurious trips or other hindrances. These issues are further complicated when multiple products requiring different functions or setpoints are produced in the same SIS-protected batch unit.This paper will discuss the challenges particular to the design, operation, and maintenance of a SIS in multi-product batch operations and present practical options for successfully resolving the concerns. A key insight into successful adaptation is treating the batch SIS as a “permission” system for the BPCS to operate. Although many items can be addressed through clever engineering practices, sustainable success relies on proactive, robust management of the safety lifecycle.     

基于HFACS的中国特别重大煤矿事故研究

特别重大煤矿事故一直被认为是中国最严重的社会问题之一。本论文的研究目标有两个。首先,分析中国特别重大煤矿事故的致因因素;其次,定量考察事故致因因素间的相互作用关系。基于HFACS模型,在层级层面上,94起特别重大煤矿事故的实证表明:"不安全行为"的发生频率最高;在类别层面上,"监管不力"的发生频率最高;在指标层面上,"对违法行为失察或制止不力"的发生频率最高。借助OR技术,计算得出上一层级对下一层级指标的影响关系,并得到了一系列致因因素间的影响路径,这为遏制和预防特别重大煤矿事故提供了"路线图"。     

Data classification and performance evaluation for the most commonly-used univariate alarm systems

Alarm systems are critically important for safe and efficient operations of industrial plants, but many industrial alarm systems are suffering from too many nuisance alarms. This paper proposes a method to classify normal and abnormal data segments and evaluate performance indices for the most commonly used univariate alarm systems. The proposed method consists of three steps. First, piece-wise linear representations are exploited in separating historical data samples of an analog process variable configured with alarms into data segments with same qualitative trends. Second, data segments are classified into normal, abnormal and unclassified conditions via a mean hypothesis test; a required assumption is that data segments in normal and abnormal conditions have different mean values being distinguishable from alarm thresholds. Third, based on the normal and abnormal data, performance indices of univariate alarm systems are calculated, including two newly formulated ones as the false alarm duration ratio and the missed alarm duration ratio. The effectiveness of the proposed method is illustrated by numerical and industrial examples.