Representational success: A new paradigm for achieving species protection by reserve site selection

Models for designing habitat reserve networks have focused on minimizing the number of sites necessary to cover each species one or more times. A solution to this problem is usually one from among a large number of alternative optimal configurations of sites. This paper develops an iterative method for building reserve networks that produces an optimal solution to the species set covering problem (SSCP) and also maximizes the number of species covered two or more times, three or more times, and so on, conditional on the solution to the previous iteration. We refer to this as representational success. Thus, a pareto optimal species set covering is achieved that is preferable to an arbitrary optimal solution to the SSCP.     

Structural perturbations of models used in mathematical biology

The paper discusses the importance of understanding structural perturbations of models used in mathematical biology, where we mainly focus on ecology and dynamical systems. We describe first briefly the classical modeling strategy and the derivation of model structures. Structural perturbations are then discussed, mainly in the framework of ODEs. We give some examples how insights obtained from this type of model could be transfered to other kinds of models. Finally we propose an alternative modeling strategy characterized by a systematic investigation of a models neighbourhood in an appropriately chosen model class.     

资源承载力监测——以西藏“一江两河”地区为例

对自然资源的无序开发和对生态系统的破坏制约了我国的可持续发展。资源承载力是描述地区发展受自然资源限制的重要工具,也是衡量区域可持续发展的重要依据。基于西藏“一江两河”地区县级统计数据,定量计算水、土和生态等资源承载力,并根据定量评价结果构建资源承载力监测体系并应用于“一江两河”地区。研究结果表明:（1）“一江两河”地区人粮关系趋于紧张,部分地区人口—粮食—土地矛盾突出,76.5%的县土地资源承载力下降,83.3%的县土地资源承载指数增长;“一江两河”地区各县（市、区）水资源承载力远大于实际人口,承载指数均小于0.05,但77.8%的县水资源承载力下降,县域承载指数均增长;各县生态承载力增长,承载指数下降,部分县处于生态赤字状态。（2）“一江两河”地区资源承载力的主要制约因素由生态承载力转变为土地资源承载力。2000—2015年,在“一江两河”地区资源承载力处于临界超载或超载的县中,对资源承载状态影响最大的资源承载力由生态承载力逐步转变为土地资源承载力。（3）“一江两河”地区资源承载力等级逐渐提升,可能带来的危害或负面影响程度降低。2000—2015年,资源承载力为三级（中度负载）及以下等级的县由15个（83.3%）降至3个（16.7%）。资源承载力长效监测机制的建立有助于明晰资源开发利用现状,科学利用区域自然资源,促进地区生态保护和可持续发展。     

基于GAM模型的太湖叶绿素a含量与环境因子相关性分析

随着富营养化程度的加剧,太湖近30年来水华频发.为了探讨太湖西部沿岸水华暴发与环境因子的关系,于2017年4月1-18日（当地历年蓝藻暴发早期）在太湖西部沿岸进行了密集原位调查.共采集样品72个,测定了水温、溶解氧、各形态氮、磷营养盐浓度以及风速等环境指标,并利用GAM（广义相加模型）定量分析了叶绿素a含量与各环境因子间的关系.结果表明:①叶绿素a含量波动幅度较大（17.10~795.89 mg/m3）,太湖西部沿岸带有明显的蓝藻水华暴发现象.②水温、风速以及硝态氮浓度与叶绿素a含量的变化显著相关（P<0.05）,各环境因子按其对叶绿素a含量变化的解释率排序为水温>风速>硝态氮浓度.其中水温是影响叶绿素a含量最为重要的环境因子,叶绿素a含量随着水温的升高呈现明显上升趋势.风速也是影响叶绿素a含量的关键因子之一,较低的风速（<3 m/s）有利于蓝藻的漂移集聚从而形成水华,引起叶绿素a含量的升高.研究显示,GAM模型较好地解释了叶绿素a的含量变化,模型总体解释度达到70.6%,可为太湖西部沿岸蓝藻水华早期的预测预警提供一定的基础支撑.      

Correlation between crash avoidance maneuvers and injury severity sustained by motorcyclists in single-vehicle crashes

Objectives: In order to improve motorcycle safety, this article examines the correlation between crash avoidance maneuvers and injury severity sustained by motorcyclists, under multiple precrash conditions. Method: Ten-year crash data for single-vehicle motorcycle crashes from the General Estimates Systems (GES) were analyzed, using partial proportional odds models (i.e., generalized ordered logit models). Results: The modeling results show that “braking (no lock-up)” is associated with a higher probability of increased severity, whereas “braking (lock-up)” is associated with a higher probability of decreased severity, under all precrash conditions. “Steering” is associated with a higher probability of reduced injury severity when other vehicles are encroaching, whereas it is correlated with high injury severity under other conditions. “Braking and steering” is significantly associated with a higher probability of low severity under “animal encounter and object presence,” whereas it is surprisingly correlated with high injury severity when motorcycles are traveling off the edge of the road. The results also show that a large number of motorcyclists did not perform any crash avoidance maneuvers or conducted crash avoidance maneuvers that are significantly associated with high injury severity. Conclusions: In general, this study suggests that precrash maneuvers are an important factor associated with motorcyclists' injury severity. To improve motorcycle safety, training/educational programs should be considered to improve safety awareness and adjust driving habits of motorcyclists. Antilock brakes and such systems are also promising, because they could effectively prevent brake lock-up and assist motorcyclists in maneuvering during critical conditions. This study also provides valuable information for the design of motorcycle training curriculum.     

南方某县居民尿镉浓度和相关影响因素研究

本文采用整群随机抽样的方法,抽取污染区、对照区10个村的1274个居民开展内暴露及问卷调查,通过采集这些居民的晨尿和10个村的土壤、大气颗粒物、饮用水、大米样品,对采集的所有样品进行了镉含量的测定.同时,将这些检测调查资料通过MLwiN 2.02软件进行多水平模型拟合,以评估南方某县污染区和对照区居民尿镉含量在不同水平之间的差异性,并找出影响这种差异的社会人口和环境方面的因素.结果表明,居民的尿镉含量在村和个体不同水平上均存在显著差异,其中,QL-3、FJ-4污染区人体尿镉含量明显高于其它研究区,远远超过其临界值.多水平模型的结果显示,土壤镉含量、大米镉含量、居民性别、居民的外出工作时长和居住地离污染企业的距离对居民尿镉水平有影响,而居民的年龄、涉镉工作时长、吸烟时长和在当地生活时长这4个因素对居民尿镉水平的影响差异没有统计学意义.与一般线性模型相比,多水平模型拟合的效果更佳.研究表明,多水平模型能够较合理地揭示居民尿镉水平的地区差异及社会人口和环境因素的影响.     

模糊数学法在兰州市地表水环境质量评价中的应用分析研究

根据模糊数学理论,建立了水环境质量模糊综合评价数学模型.选取兰州市地表水为研究对象,对兰州市地表水(黄河岸门桥断面)2009年-2014年全年各项水质平均值进行水环境质量评价,更加综合的评价兰州市地表水环境质量变化趋势及主要污染物,科学的分析兰州市地表水环境质量现状和存在的问题.结果表明:兰州市地表水2009年-2014年环境质量呈日益改善的状态,2009年-2010年兰州市地表水环境质量综合评价结果属于V类,2010年-2014年兰州市地表水环境质量综合评价结果属于Ⅰ类,水体中主要污染物为总氮.     

Are dispersion models suitable for simulating small gaseous chlorine releases?

Dispersion models are mostly validated on the basis of historical dispersion experiments. The latter imply large quantities of hazardous products (flammable or toxic gases), and are dedicated to study the dispersion of the resulting clouds on great distances from the source to reach a better knowledge of the different phases of gas dispersion (slumping, creeping, passive dispersion…).However, dispersion models have hardly been validated on small releases and therefore require more validation on small plumes of dangerous gases. Indeed, what is their reliability in case of accidents involving small amounts (e.g., chlorine leakages at swimming pools’ installations), and for small distances downwind the gas source? This information is of prime interest in so far as small releases are more likely to occur than larger ones.This paper reports on chlorine small-scale dispersion experiments and deals with the comparison between experimental data of ground level concentrations in the plume and predicted concentrations obtained from several dispersion models.     

人群疏散中"非适应性"行为的研究

本文从人与人的相互作用和社会学、心理学的角度,对人群疏散中“非适应性”行为的理论、计算机模型、模拟原理等进行了较为深入的研究,并以具体实例说明了Building Exodus软件在人群疏散模拟分析中的具体应用,为完善该研究方向的计算机模型和促进软件的开发提供理论和方法的指导.文章得出的结论是：“非适应”人群行为的研究需要从心理学和社会学的角度建立人群中个人行为与社会行为的理论框架.“非适应”人群行为的研究方法必须与紧急情况相结合,而紧急情况是一个由多个人员组成的复杂系统,大量人群环境的模拟需要涉及到人与人之间,人与环境之间的相互作用.