自由飞行下基于高斯白噪声的碰撞风险模型

飞机的安全性在自由飞行中受到通信导航监视性能、人为因素、防撞系统等因素的影响,其中通信导航监视性能会导致飞机产生定位误差,这种定位误差具有高斯白噪声的特性。主要考虑飞行定位误差的高斯白噪声特性,将此误差用概率表示为以理论位置向外辐射,根据飞机的相对运动,建立基于高斯白噪声的碰撞风险模型,给出模型中各参数的求解方法,从而得到碰撞风险。最后用算例验证了模型的可行性,在现行的安全目标水平之下为相关运行部门提供相应的最小安全间距,为实际运行奠定一定的理论基础。     

LABORATORY TESTS OF EROSION DEPENDENCE ON PROPERTIES OF SOILS AND RAINFALL1

ABSTRACT: One hundred and sixty-two rainfall-induced soil erosion tests were conducted to assist in predicting soil loss and subsequent increase in total suspended solids leaving a highway construction site during a rainfall event. A rainfall simulator and a water flume were constructed for the tests. Soil shear strength, compressive strength, rainfall intensity, and soil bed slope were treated as variables during the experiments. The soil with a higher shear strength resisted soil erosion better than lower strength soils. Soil loss was nearly independent of shear strength at low rainfall intensity but at high intensities, the shear strength was more important in resisting soil loss. Lower soil loss can be expected for cohesive soils if the compressive strength is high.     

基于MOVES的西安市出租车污染物排放分析

利用MOVES模型对2012年西安市出租车油改气后污染物排放因子进行模拟,得出污染物CO、NOx、PM2.5、PM10、HC的排放因子分别为3.488 1 g/km、0.370 0 g/km、0.004 7 g/km、0.005 1 g/km、0.095 2 g/km,计算得到5种污染物的年排放总量分别为4 830.76 t、512.42 t、6.51 t、7.06 t、131.85 t。将得到的数据与2010年相关数据比对,说明出租车油改气后污染物排放量在机动车总排放量中所占比例有所下降。     

铜绿微囊藻和孟氏颤藻在富营养化湖泊中生长特征的模拟研究

为了模拟富营养化状态下2种蓝藻在湖泊中的生长特征,采用大型室内湖泊模拟装置进行了模拟研究,并通过三角瓶实验以及光合作用速率的响应实验对模拟装置中藻的生长特征进行了分析.湖泊模拟装置中,铜绿微囊藻和孟氏颤藻在对数生长期的特征生长速率分别为0.43d-1和0.32d-1,但对数生长期很短,仅3～4d.在对数期后有一个很长的"线性期",即生物量随时间近似成线性增长.在氮、磷较为充分的条件下,由于较强的光合作用导致了水体pH的升高,以及生物量增高导致了藻的自遮蔽作用,使藻的生长容易出现碳源限制和光限制.受水下光的影响,2种藻细胞内叶绿素a含量在对数期内一直增大.随后颤藻细胞内叶绿素a含量又逐渐降低,而微囊藻细胞内叶绿素a含量仍保持较高的水平,其原因可能是微囊藻能适应更高的pH.     

Analysis of effects of driver’s evasive action time on rear-end collision risk using a driving simulator

Introduction: Driver’s evasive action is closely associated with collision risk in a critical traffic event. To quantify collision risk, surrogate safety measures (SSMs) have been estimated using vehicle trajectories. However, vehicle trajectories cannot clearly capture presence and time of driver’s evasive action. Thus, this study determines the driver’s evasive action based on his/her use of accelerator and brake pedals, and analyzes the effects of the driver’s evasive action time (i.e., duration of evasive action) on rear-end collision risk. Method: Fifty drivers’ car-following behavior on a freeway was observed using a driving simulator. An SSM called “Deceleration Rate to Avoid Crash (DRAC)” and the evasive action time were determined for each driver using the data from the driving simulator. Each driver tested two traffic scenarios – Cars and Trucks scenarios where conflicting vehicles were cars and trucks, respectively. The factors related to DRAC were identified and their effects on DRAC were analyzed using the Generalized Linear Models and random effects models. Results: DRAC decreased with the evasive action time and DRAC was closely related to drivers’ gender and driving experience at the road sections where evasive action to avoid collision was required. DRAC was also significantly different between Cars and Trucks scenarios. The effect of the evasive action time on DRAC varied among different drivers, particularly in the Trucks scenario. Conclusions: Longer evasive action time can significantly reduce crash risk. Driver characteristics are more closely related to effective evasive action in complex driving conditions. Practical Applications: Based on the findings of this study, driver warning information can be developed to alert drivers to take specific evasive action that reduces collision risk in a critical traffic event. The information is likely to reduce the variability of the driver’s evasive action and the speed variations among different drivers.     

预浓缩系统-全二维气相色谱-飞行时间质谱分析环境空气中挥发性有机物

采用SummA罐采集样品，自动进样器进样，三级冷阱预浓缩样品，全二维气相色谱／飞行时间质谱法（GC×GC／TOFMS）测试分析，以较长的非极性柱Rxi-5MS（60m×320μm×1．0μm）作为第一维柱，较短的中等极性柱DB-17MS（2．0×0．1mm×0．1μm）作为第二维柱，对环境空气中的VOC成分进行了定性定量分析。通过考察方法的线性范围、精密度、加标回收率、检出限与《空气和废气监测分析方法》（四版）给出的两个方法比较，证实该方法特性不仅满足方法学要求，而且能够更加准确快速监测环境空气中VOC。     

Development of a FRAM-based framework to identify hazards in a complex system

System-based approaches such as Functional Resonance Analysis Model (FRAM) are developed to model the complex interactions of system variables and their performance variabilities that may lead to a hazardous scenario in a complex system. However, they have limitations to be applied in process industries for hazard identification since they are heavily based on qualitative analysis and expert elicitations. To overcome the limitations of the system-based hazard identification, the study developed a FRAM-based framework to integrate a human performance model, an equipment performance model, and a first-principle based chemical process model into a hybrid simulator, which will be able to aid hazard analysis in the process industries. The simulator is capable of simulating the performance variabilities of the functions through the aggregation of mathematical models within a complex system, which can be used to simulate potential hazard situations and identify the corresponding interactions. Interaction analysis is conducted by applying association rule mining to the simulated data. The impact of the interactions among upstream functions on the performance of downstream functions can be identified by interpreting the rules, whose antecedents contain upstream functions and consequents contain downstream functions.     

Effect of alcohol use on accelerating and braking behaviors of drivers

Objective: The present study examines the accelerating and braking behaviors of drivers at different blood alcohol concentrations (BACs) in heterogeneous driving conditions using driving simulator experiments.

Methods: Eighty-two licensed drivers performed simulated driving in a rural road environment designed in the driving simulator at 4 BAC levels: 0.00, 0.03, 0.05, and 0.08%. Driving performance was analyzed using vehicle control variables such as mean acceleration and mean brake pedal force. Generalized linear mixed models were developed to quantify the effect of different alcohol levels and explanatory variables such as driver’s age, gender, and other factors on the driving performance indicators.

Results: Alcohol use was reported as a significant factor affecting the accelerating and braking performance of drivers. The acceleration model results indicated that drivers’ mean acceleration increased by 0.013, 0.026, and 0.027 m/s² for BAC levels of 0.03, 0.05, and 0.08%, respectively. Results of the brake pedal force model showed that drivers’ mean brake pedal force increased by 1.09, 1.32, and 1.44 N for BAC levels of 0.03, 0.05, and 0.08%, respectively. Age was a significant factor in both the models where a 1-year increase in driver age resulted in a 0.2% reduction in mean acceleration and a 19% reduction in mean brake pedal force. Driving experience could compensate for the negative effects of alcohol to some extent while driving.

Conclusions: The findings of the present study revealed that drivers tend to be more aggressive and impulsive under the influence of alcohol, which deteriorates their driving performance. Impairment in accelerating and braking behaviors of drivers under the influence of alcohol leads to increased crash probabilities. The conclusions may provide reference in making countermeasures against drinking and driving and contribute to traffic safety.     

Comparison of the Photodegradation of Imazethapyr in Aqueous Solution,on Epicuticular Waxes,and on Intact Corn (Zea Mays) and Soybean (Glycine Max) Leaves

A direct, controlled comparison of the photodegradation of imazethapyr has been made between imazethapyr in aqueous solutions, imazethapyr on the surface of epicuticular waxes of corn and soybean plants, and imazethapyr on the surface of intact corn and soybean plant leaves. In some experiments, the imazethapyr solutions were allowed to evaporate partially or fully after application to better model environmental conditions. The photodegradation of imazethapyr was fastest in aqueous solutions (k?=?0.16?±?0.02?h^?1) and slowest on the surface of corn and soybean plants (k_corn?=?0.00048?±?0.001?h^?1 and k_soy?=?0.00054?±?0.003?h^?1). Experiments allowing evaporation during irradiation have intermediate rate constants (e.g., k_corn?=?0.082?±?0.005?h^?1). Finally, identification of photoproducts was also examined on epicuticular waxes of corn and soybean plants for the first time.     

改进的灰色马尔科夫模型在飞行事故率预测中的应用

基于灰色理论和马尔科夫理论,建立传统的灰色预测模型和灰色马尔科夫预测模型;对传统灰色预测模型的背景值和初值的构造存在一定的误差进行改进,并用改进后的新模型对飞行事故率预测的结果与传统的灰色马尔科夫模型进行对比;仿真结果表明:改进后的灰色马尔科夫模型预测精度有了进一步的提高并验证了算法的有效性。