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.     

回采工作面及采空区瓦斯运移的数学模型及数值模拟研究

为更真实可靠地还原回采工作面及采空区内流场和瓦斯场的分布特征,基于回采工作面和采空区不同的介质属性,并考虑瓦斯扩散能力的差异,建立了各自的强耦合多物理场数学模型,并给出了瓦斯涌出所满足的质量通量边界条件。采用COMSOL Multiphysics构建了强耦合的自由和多孔介质流动以及自由和多孔介质稀物质传递等物理场,以龙煤矿业集团股份有限公司双鸭山分公司的东保卫井田二水平一采区36号煤-570左面为研究对象,研究了回采工作面及采空区稳态下的瓦斯运移特征。结果表明:采空区浅部瓦斯体积分数较小但梯度较大,且随着采空区向深部延伸,瓦斯体积分数的梯度逐渐降低,但其数值逐渐增大并趋于稳定;另外,采空区内实测的瓦斯体积分数分布与数值模拟结果具有较好的一致性,验证了建立的回采工作面及采空区瓦斯运移的数学模型和数值模型的可靠性和准确性。     

Development of pedestrian- and vehicle-related safety performance functions using Bayesian bivariate hierarchical models with mode-specific covariates

Introduction: Pedestrian safety is a major concern as traffic crashes are the leading cause of fatalities and injuries for commuters. Traffic safety research in the past has developed various strategies to counteract traffic crashes, including the safety performance function (SPF). However, there is still a need for research dedicated to enhancing the SPF for pedestrians from perspectives of methodological framework and data input. To fill this gap, this study aims to add to the current SPF development practice literature by focusing on pedestrian-involved collisions, while considering the typical vehicle ones as well. Methods: First, bivariate models are used to account for the common unobserved heterogeneity shared by the pedestrian- and vehicle-related crashes at the same intersections. Second, variable importance ranking technique is used, along with correlation analysis, to determine mode-specific feature input. Third, the exposure information for both modes, annual pedestrian count, and annual daily vehicles traveled are used for model development. Fourth, a recent Bayesian inference approach (integrated nested Laplace approximation (INLA)) was adopted for bivariate setting. Finally, different evaluation criteria are used to facilitate comprehensive model assessment. Results: The results reveal different statistically significant factors contributing to each of the modes. The offset intersection provides better safety performance for both pedestrians and drivers as compared to other intersection designs. The model findings also corroborate the sensibility of using the bivariate models, rather than the separate univariate ones. Practical Applications: The study shows that pedestrians are more vulnerable to various intersection features such as left-turn channelization, intersection control, urban and rural population group, presence of signal mastarm on the cross-street, and mainline average daily traffic. Greater focus should be directed toward such intersection features to improve pedestrian safety.     

Influence of built environment and roadway characteristics on the frequency of vehicle crashes caused by driver inattention: A comparison between rural roads and urban roads

Introduction: With prevalent and increased attention to driver inattention (DI) behavior, this research provides a comprehensive investigation of the influence of built environment and roadway characteristics on the DI-related vehicle crash frequency per year. Specifically, a comparative analysis between DI-related crash frequency in rural road segments and urban road segments is conducted. Method: Utilizing DI-related crash data collected from North Carolina for the period 2013–2017, three types of models: (1) Poisson/negative binomial (NB) model, (2) Poisson hurdle (HP) model/negative binomial hurdle (HNB) model, and (3) random intercepts Poisson hurdle (RIHP) model/random intercepts negative binomial hurdle (RIHNB) model, are applied to handle excessive zeros and unobserved heterogeneity in the dataset. Results: The results show that RIHP and RIHNB models distinctly outperform other models in terms of goodness-of-fit. The presence of commercial areas is found to increase the probability and frequency of DI-related crashes in both rural and urban regions. Roadway characteristics (such as non-freeways, segments with multiple lanes, and traffic signals) are positively associated with increased DI-related crash counts, whereas state-secondary routes and speed limits (higher than 35 mph) are associated with decreased DI-related crash counts in rural and urban regions. Besides, horizontal curved and longitudinal bottomed segments and segments with double yellow lines/no passing zones are likely to have fewer DI-related crashes in urban areas. Medians in rural road segments are found to be effective to reduce DI-related crashes. Practical Applications: These findings provide a valuable understanding of the DI-related crash frequency for transportation agencies to propose effective countermeasures and safety treatments (e.g., dispatching more police enforcement or surveillance cameras in commercial areas, and setting more medians in rural roads) to mitigate the negative consequences of DI behavior.     

腈醛混合化合物对发光菌联合毒性的QSAR研究

测定了羟基乙腈与系列醛类化合物和对苯二甲醛与系列腈类化合物对发光菌(Photobacterium phosphoreum)的联合毒性，探讨了腈醛混合化合物对发光菌的联合毒性机制，并尝试提出了腈醛混合化合物对发光菌联合毒性的QSAR模型．结果表明，不同的腈醛混合化合物对发光菌的联合毒性不同，联合毒性的大小与腈类化合物和醛类化合物之间化学相互作用的程度紧密相关，采用QSAR模型TU=0．842—0．831σ。(n=8，r^2=0．803，SE=0．222，F=24．415，P=0．003)和TU=-0．348—8．450C^*(n=8，r^2=0．874，SE=0．219，F=41．730，P=0．001)分别定量描述羟基乙腈与系列醛类化合物和对苯二甲醛与系列腈类化合物对发光菌的联合毒性．模型具有较高的稳定性和预测能力．     

广东沼气农业模式的典型调查与思考

回顾了广东沼气发展历程,介绍了广东典型沼气农业模式,包括广东西南部丘陵区典型农户沼气模式,广东东部丘陵区典型农户沼气模式,广东东北部丘陵山区典型农户沼气模式,广东低洼地和积水区农户沼气模式,以及广东规模化养殖场沼气模式,并在此基础上分析了沼气农业模式的空间分布规律、沼气模式和经济发展的关系以及沼气发展的系统工程。     

A model of the emergence of infectious pancreatic necrosis virus in Scottish salmon farms 1996–2003

Infectious pancreatic necrosis virus (IPNV) is an increasingly common pathogen in farmed Scottish Atlantic salmon; over 80% of marine sites are now infected, although most do not suffer clinical disease. The increasing prevalence of this pathogen in farms over the period 1996–2003 is modelled using a simple susceptible–infected (SI) epidemic model. Because salmon production approximately doubled over this period, population-dependent and -independent transmission models are compared. The model generates mean R₀ (increase ratio) of 1.41 in fresh and 1.45 in marine water farms at the national level; higher values apply with time under population-dependent transmission (1.58, freshwater, 1.80 marine by 2003). Regional differences in R₀ are mostly moderate, indicating similar regional processes in spite of substantial difference in prevalence. Prevalence of IPNV for marine sites was further increased by the use of smolts (young salmon) from multiple freshwater sources. The model suggests that prevalence is entering dynamic equilibrium and will stabilise or only increase slowly as population increases. Cutting freshwater transmission is the most effective single strategy at reducing IPNV prevalence, but a combination of strategies (including reducing the number of sources of smolts) is better and indeed is required for eradication. Eradication would require cuts in transmission of at least 30–45% and this is unlikely to be practicable.     

Bimodality of the combined removal and signs-of-activities estimator for sampling closed animal populations

The possibility of a bimodal log-likelihood function arises with certain data when the combined removal and signs-of-activities estimator is used. Bimodal log-likelihoods may, in turn, yield disjoint confidence intervals for certain confidence levels. The hypothesis that bimodality is caused by the violation of the equal catchability assumption of the removal model, leading to the combination of contradictory data/models in the combined estimator is set forth. Simulations exploring the effect of the violation of removal model assumptions on estimation and inference showed that the assumption of unequal capture probability influenced the frequency of bimodal likelihoods; similarly, extreme parameter values for probability of capture influenced the number of excessively large confidence intervals produced. A sex-specific combined estimator is developed as a remedial model tailored to the problem. The simulations suggest that both the signs-of-activities estimator and the sex-specific estimator perform equally well over the range of simulations presented, though the signs-of-activities estimator is easier to implement.     

Female choice for complex song in the European starling: a field experiment

Male European starlings Sturnus vulgaris sing long complex songs that appear to be important in the courtship of females but which also influence competitive interactions between males. We tested the hypothesis that females choose mates on the basis of the complexity of their songs, rather than on the quality of the territories the males defended. In order to determine whether certain territories were preferred over others, the first set of birds to settle in the experimental nest-boxes was removed and a second set allowed to settle. Consistent preferences for certain nest-boxes were indicated by correlations between the settlement patterns of the first and second sets of birds. However, males with the most complex song did not necessarily occupy the most preferred nest sites. Males with more complex song acquired mates faster. This relationship remained significant when nest-site preference was statistically controlled, indicating that female starlings chose males with complex song rather than those that defended preferred nest sites. A number of morphological variables were also found to be uncorrelated with female choice. Song complexity in European starlings increases with age, and the evolution of song complexity in this species is consistent with an age-indicator model of sexual selection. Males with larger repertoires were also in better condition, indicating that females obtain high-quality mates by choosing on the basis of male song. Received: 29 April 1995/Accepted after revision: 9 September 1995