Benefits of protective fencing to plant and rodent communities of the western Mojave Desert,California

Human disturbance in the western Mojave Desert takes many forms. The most pervasive are livestock grazing and off-highway vehicle use. Over the past few decades several areas within this region have been fenced to preclude human disturbance. These areas provide opportunities to study the impact of human activities in a desert ecosystem. This paper documents the response of plant and small mammal populations to fencing constructed between 1978 and 1979 at the Desert Tortoise Research Natural Area, Kern County, California. Aboveground live annual plant biomass was generally greater inside than outside the fenced plots during April 1990, 1991, and 1992. The alien grassSchismus barbatus was a notable exception, producing more biomass in the unprotected area. Forb biomass was greater than that of alien annual grasses inside the fence during all three years of the study. Outside the fence, forb biomass was significantly higher than that of alien grasses only during spring 1992. Percent cover of perennial shrubs was higher inside the fence than outside, while no significant trend was detected in density. There was als more seed biomass inside the fence; this may have contributed to the greater diversity and density of Merriam's kangaroo rats (Dipodomys merriami), long-tailed pocket mice (Chaetodipus formosus), and southern grasshopper mice (Onychomys torridus) in the protected area. These results show that protection from human disturbance has many benefits, including greater overall community biomass and diversity. The significance and generality of these results can be further tested by studying other exclosures of varying age and configurations in different desert regions of the southwestern United States.     

如何预防飞行过程中的不安全因素

民航飞机的运行过程大致分为起飞、爬升、巡航、航路下降、进近、着陆6个阶段。飞机起飞爬升和进近着陆是飞行事故的高发阶段。笔者分析了飞行各阶段的危险源,尤其将起飞爬升和进近着陆两个阶段作为主要研究内容;指出了飞行各阶段的关键操作技术及原理;提出了起飞可能面临多种危险,给出了起飞前机组风险意识检查单,并列出了国际飞行安全基金会(FSF,FlightSafetyFoundation)提出的进近着陆风险意识检查单;运用机组资源管理工具使飞行员树立安全风险意识,从而达到降低飞行事故率,提高飞行安全水平的目的。     

基于模糊数学的飞行学员安全状态综合评价

探讨飞行学员在训练过程中的安全状态，既可以减少飞行训练事故，保证飞行训练安全，又可以为飞行训练提供参考依据。通过对飞行学员飞行训练调查研究和分析，结合各方面专家在人为因素上的研究成果，建立了飞行学员安全状态综合评价体系，并用层次分析法（AHP）确定各评价指标权重，构建了飞行学员安全状态的模糊综合评价模型，并对飞行学员安全状态进行了综合评价，得出了安全状态综合评价等级。     

遥感三维可视化在南沟泥石流调查中的运用

在中国20年来泥石流遥感调查所取得成绩以及存在问题的基础上,尝试用新方法对泥石流进行研究,即采用遥感三维可视化方法调查泥石流。以汶川南沟为例,利用高精度的卫星遥感影像（quickbird）和1：50000的等高线,在erdas软件的支持下,实现了遥感影像三维可视化。并在此基础上对其应用——虚拟GIS飞行和泥石流流域内崩塌堆积物三雏遥感解译。实践证明由于遥感三维解译能全方位观察泥石流沟谷以及相关的地形地貌,所以其解译的准确率比传统二雏遥感解译率高。     

Frequent summer nuptial flights of ants provide a primary food source for bats

In many ant species, nuptial flight tends to be short in time and assumed to be synchronous across a large area. Here, we report that, in the upper Jordan Valley, northern Israel, massive nuptial flights of Carpenter ants (Camponotus sp.) occur frequently throughout the summer, and their alates form up to 90% of the diet of the greater mouse-tailed bat (Rhinopoma microphyllum) during this period. This fat and protein-rich diet enables female bats to lactate during summer, and the large amount of fat that both sexes accumulate may serve as an energy source for their following winter hibernation and posthibernation mating in early spring (March–April). We suggest that the annual movement of these bats to the Mediterranean region of Israel may have evolved in order to enable them to exploit the extremely nutritious forms of ant alates when the bats’ energetic demands are highest.     

单机寿命监控中飞行时间的确定方法及影响研究

对飞机实际的飞行时间判断正确与否将直接影响到对飞机损伤量的计算。对两种飞行时间确定方法进行了对比,分析表明,通过发动机转速同时结合地速为判断准则,可以更为准确地从飞行参数数据中提取飞行时间。评估了8种机型损伤量的计算结果,对比表明,对于经常使用加力状态起飞的飞机或起降性能一般的飞机来说,飞行时间上的变化会对损伤量的计算值产生较大影响。     

Combining Coordination of Motion Actuators with Driver Steering Interaction

Objective: A new method is suggested for coordination of vehicle motion actuators; where driver feedback and capabilities become natural elements in the prioritization.

Methods: The method is using a weighted least squares control allocation formulation, where driver characteristics can be added as virtual force constraints. The approach is in particular suitable for heavy commercial vehicles that in general are over actuated. The method is applied, in a specific use case, by running a simulation of a truck applying automatic braking on a split friction surface. Here the required driver steering angle, to maintain the intended direction, is limited by a constant threshold. This constant is automatically accounted for when balancing actuator usage in the method.

Results: Simulation results show that the actual required driver steering angle can be expected to match the set constant well. Furthermore, the stopping distance is very much affected by this set capability of the driver to handle the lateral disturbance, as expected.

Conclusion: In general the capability of the driver to handle disturbances should be estimated in real-time, considering driver mental state. By using the method it will then be possible to estimate e.g. stopping distance implied from this. The setup has the potential of even shortening the stopping distance, when the driver is estimated as active, this compared to currently available systems. The approach is feasible for real-time applications and requires only measurable vehicle quantities for parameterization. Examples of other suitable applications in scope of the method would be electronic stability control, lateral stability control at launch and optimal cornering arbitration.     

基于物元模型的航空公司飞行安全风险综合评价

提高航空公司飞行安全风险管理水平的关键是对航空公司飞行安全风险的现状进行科学客观的综合评价。在系统分析影响航空公司飞行安全风险因素的基础上,建立了由机组因素、飞机因素、环境因素和飞行管理4个1级指标及26个2级指标组成的航空公司飞行安全风险指标体系,指标体系中各级评价指标的权重由层次分析法确定;由于航空公司飞行安全风险评价具有物元的可拓性,构建了航空公司飞行安全风险评价的多级物元模型。实例演算表明,物元理论能充分地利用航空公司飞行安全风险评价中的指标信息,确定影响航空公司飞行安全风险的主要因素,以便航空公司采取针对性的措施提高飞行安全风险管理水平。     

车内挥发性有机物检测方法与控制策略研究

以静止状态下车内挥发性有机化合污染物为研究对象,在分析其排放与时间、温度及通风等关系的基础上,对比了国内外车内空气中挥发性有机化合物的检测方法,重点分析了日本汽车工业协会JAMA标准,并在分析国外经验基础上,对我国车内空气挥发性有机污染物的控制策略提出了合理建议。     

火场环境下无人机热损伤试验研究

无人机(UAV)逐步运用于火场搜救,但同时会因为火场高温而受损,为提高UAV在火场救援中的工作效率,设计一种UAV动态测试平台,开展UAV火场飞行试验;分析火场环境下UAV的热损伤情况,探究UAV在火场中的机身温度变化特征和UAV火场飞行安全距离。结果表明:火场热辐射和热对流是造成UAV热损伤的主要形式;旋翼产生的气流场对UAV机身有较为明显的降温效应,在试验工况下最高有25.6℃的降温作用;UAV与火焰的相对距离减少会增加机身的热损伤,在距离0.8 m处开始发生不可逆热损坏,试验工况下UAV火场飞行的安全距离为0.8 m。