基于突变理论的国内外火灾科学研究进展和展望

简要归纳了突变模型的特征和突变理论的应用方式,重点综述了突变理论在火灾科学中的应用情况,概括了突变理论在火灾科学中三个应用特点。针对具体油气爆炸实验数据,利用随机突变理论,对油气爆炸的突变模式进行了初步研究,说明了建立统计突变模型的可行性。最后指出了突变理论应用于火灾科学的未来研究方向。     

Motorcycle active safety systems: Assessment of the function and applicability using a population-based crash data set

Objective: Motorcycles and mopeds, often referred to as powered 2-wheelers (PTWs), play an important role in personal mobility worldwide. Despite their advantages, including low cost, space occupancy, and fuel efficiency, the risk of sustaining serious or fatal injuries is higher than that for occupants of passenger cars. The development of safety systems specific for PTWs represents a potential way to reduce casualties among riders. With the proliferation of new active and passive safety technologies, the question as to which might offer the most value is important. In this context, a prioritization process was applied to a set of PTW active safety systems to evaluate their applicability to crash scenarios alone and in combination. The systems included in the study were antilock braking (ABS), autonomous emergency braking (AEB), collision warning, curve warning, and curve assist.

Methods: With the functional performance of the 5 safety systems established, the relevance of each system to specific crash configurations and vehicle movements defined by a standardized accident classification system used in Victoria, Australia, was rated by 2 independent reviewers, with a third reviewer acting as a moderator where disagreements occurred. Ratings ranged from 1 (definitely not applicable) to 4 (definitely applicable). Using population-based crash data, the number and percentage of crashes that each safety system could potentially influence, or be relevant for, was defined. Applying accepted injury costs permitted the derivation of the societal economic cost of PTW crashes and the potential reductions associated with each safety system given a theoretical crash avoidance effectiveness of 100%.

Results: In the 12-year period 2000–2011, 23,955 PTW riders and 1292 pillion passengers were reported to have been involved in a road crash, with over 500 killed and more than 10,000 seriously injured; only 3.5% of riders/pillion passengers were uninjured. The total economic cost associated with these injured riders and pillion passengers was estimated to be AU$11.1 billion (US$7.70 billion; €6.67 billion). The 5 safety systems, as single solutions or in combination, were relevant to 57% of all crashes and to 74% of riders killed. Antilock braking was found to be relevant to the highest number of crashes, with incremental increases in coverage when combined with other safety systems.

Conclusions: The findings demonstrate that ABS, alone and in combination with other safety systems, has the potential to mitigate or possibly prevent a high percentage of PTW crashes in the considered setting. Other safety systems can influence different crash scenarios and are also recommended. Given the high cost of motorcycle crashes and the increasing number of PTW safety technologies, the proposed approach can be used to inform the process of selection of the most suitable interventions to improve PTW safety.     

Testing the environmental Kuznets curve hypothesis for water footprint indicator: a cross-sectional study

The water footprint analysis has become a rapidly growing field of research although little attention has been paid to its relationship with economic growth. Using the available cross-section data, this study examines how the per capita water footprint varies as a function of per capita income within the environmental Kuznets curve framework at both aggregated and disaggregated level of water footprint. In addition, the issue of omitted variables is investigated by incorporating a number of control variables. Estimation results show no evidence in favour of an inverted-U environmental Kuznets curve, but they yield, in most cases, an evolution into an N-shaped relationship. This means that water footprint rises in the beginning with incomes, then falls as nations grow wealthier to rise again at very high income levels. This calls into question the traditional economic view of income growth sustainability as it applies to water.     

Determining Decision Thresholds and Evaluating Indicators when Conservation Status is Measured as a Continuum

Categorization of the status of populations, species, and ecosystems underpins most conservation activities. Status is often based on how a system's current indicator value (e.g., change in abundance) relates to some threshold of conservation concern. Receiver operating characteristic (ROC) curves can be used to quantify the statistical reliability of indicators of conservation status and evaluate trade‐offs between correct (true positive) and incorrect (false positive) classifications across a range of decision thresholds. However, ROC curves assume a discrete, binary relationship between an indicator and the conservation status it is meant to track, which is a simplification of the more realistic continuum of conservation status, and may limit the applicability of ROC curves in conservation science. We describe a modified ROC curve that treats conservation status as a continuum rather than a discrete state. We explored the influence of this continuum and typical sources of variation in abundance that can lead to classification errors (i.e., random variation and measurement error) on the true and false positive rates corresponding to varying decision thresholds and the reliability of change in abundance as an indicator of conservation status, respectively. We applied our modified ROC approach to an indicator of endangerment in Pacific salmon (Oncorhynchus nerka) (i.e., percent decline in geometric mean abundance) and an indicator of marine ecosystem structure and function (i.e., detritivore biomass). Failure to treat conservation status as a continuum when choosing thresholds for indicators resulted in the misidentification of trade‐offs between true and false positive rates and the overestimation of an indicator's reliability. We argue for treating conservation status as a continuum when ROC curves are used to evaluate decision thresholds in indicators for the assessment of conservation status. Determinación de Umbrales de Decisiones y Evaluación delos Indicadores cuando se Mide el Estado de de Conservación como un Continuo     

Economic Valuation of Subsistence Harvest of Wildlife in Madagascar

Wildlife consumption can be viewed as an ecosystem provisioning service (the production of a material good through ecological functioning) because of wildlife's ability to persist under sustainable levels of harvest. We used the case of wildlife harvest and consumption in northeastern Madagascar to identify the distribution of these services to local households and communities to further our understanding of local reliance on natural resources. We inferred these benefits from demand curves built with data on wildlife sales transactions. On average, the value of wildlife provisioning represented 57% of annual household cash income in local communities from the Makira Natural Park and Masoala National Park, and harvested areas produced an economic return of U.S.$0.42 ha^?1· year^?1. Variability in value of harvested wildlife was high among communities and households with an approximate 2 orders of magnitude difference in the proportional value of wildlife to household income. The imputed price of harvested wildlife and its consumption were strongly associated (p< 0.001), and increases in price led to reduced harvest for consumption. Heightened monitoring and enforcement of hunting could increase the costs of harvesting and thus elevate the price and reduce consumption of wildlife. Increased enforcement would therefore be beneficial to biodiversity conservation but could limit local people's food supply. Specifically, our results provide an estimate of the cost of offsetting economic losses to local populations from the enforcement of conservation policies. By explicitly estimating the welfare effects of consumed wildlife, our results may inform targeted interventions by public health and development specialists as they allocate sparse funds to support regions, households, or individuals most vulnerable to changes in access to wildlife. Valoración Económica de la Caza de Subsistencia de Vida Silvestre en Madagascar     

Decoupling Streamflow Responses to Climate Variability and Land Use/Cover Changes in a Watershed in Northern China

Restored annual streamflow (Q_r) and measured daily streamflow of the Chaohe watershed located in northern China and associated long‐term climate and land use/cover data were used to explore the effects of land use/cover change and climate variability on the streamflow during 1961‐2009. There were no significant changes in annual precipitation (P) and potential evapotranspiration, whereas Q_r decreased significantly by 0.81 mm/yr (p < 0.001) over the study period with a change point in 1999. We used 1961‐1998 as the baseline period (BP) and 1999‐2009 the change period (CP). The mean Q_r during the CP decreased by 39.4 mm compared with that in the BP. From 1979 to 2009, the grassland area declined by 69.6%, and the forest and shrublands increased by 105.4 and 73.1%, respectively. The land use/cover change and climate variability contributed for 58.4 and 41.6% reduction in mean annual Q_r, respectively. Compared with the BP, median and high flows in the CP decreased by 38.8 and up to 75.5%, respectively. The study concludes that large‐scale ecological restoration and watershed management in northern China has greatly decreased water yield and reduced high flows due to the improved land cover by afforestation leading to higher water loss through evapotranspiration. At a large watershed scale, land use/cover change could play as much of an important role as climate variability on water resources.     

电动汽车辐射源的仿真分析

本文运用目前较为流行的三种仿真工具来对电动汽车辐射源进行仿真分析,运用MATLAB的simulink模块对汽车电池模型等效电路进行模型的搭建与仿真分析电路电流,得到电流的表达式和仿真图,再根据对电流图形进行曲线拟合,得到电流的近似表达式。把表达式当作是时间的函数,这样就可以将电池工作时的电流导入到CST中并作为激励源进行空间的仿真分析,得到电磁波的分布图。     

悬浮泥沙对蓝藻光合及细胞化学计量的影响

选取水华微囊藻Microcystis flos-aquae为实验材料,在含不同浓度的悬浮泥沙中培养,测定其光合特性和胞内营养元素含量.结果显示,除低浓度悬浮泥沙组外,水华微囊藻比生长速率和chla浓度均低于对照组,且随着时间的延长,含泥沙组水华微囊藻的光合活性F_v/F_m显著下降.水华微囊藻的最大放氧速率P_m和光饱和点I_k随着泥沙浓度的增加而减小,而暗呼吸速率R_d和光抑制作用β显著升高.此外,随着泥沙浓度的升高,水华微囊藻单位细胞C和P含量显著降低,而单位细胞N含量略微升高;由于胞内P含量变化较大,导致N/P比和C/P比显著升高,而C/chla比值随泥沙浓度的增加呈下降的趋势.由此可见,悬浮泥沙虽然因光衰减效应减少了水华微囊藻胞内C含量以及能量供给,但微囊藻通过调节自身生理机能和代谢策略,优先补给C和提高N的合成,节约P合成的能量,通过调节胞内C：N：P储存的优化分配,以适应含悬浮泥沙的外界环境维持生长.     

煤巷迎头深部瓦斯赋存规律的实验数据分析

根据近两年来对不同矿区、不同煤层的不同煤巷掘进工作面迎头深部瓦斯赋存量以及突出预测数据的现场及实验室测定结果,得出一个在动态应力场作用下的工作面(掘进、回采)迎头深部瓦斯赋存量随深度变化的一个驼峰曲线,即工作面迎头深部的瓦斯赋存量受采动的影响而在不太深的位置处(如5~10m)会产生一个赋存峰,随着深度的增加瓦斯赋存量并非随之一直增大,其分布特征也与现有认识不尽相同。该测定结果为解释和研究工作面迎头深部的瓦斯运移、应力场分布、突出预测等提供了一个现场数据结论,为煤岩体流变模型的建立提供了相应的参考,也提出针对测定结果的疑问。