现场摊铺沥青混合料特征与路面非均匀性预测研究

非均匀性是造成沥青路面早期损坏的一个重要原因,分析非均匀性的产生原因及影响因素对控制沥青路面的非均匀性具有重要意义。为了研究摊铺机后沥青混合料特征与路面上的各种非均匀性的关系,笔者首先根据现场摊铺沥青路面非均匀性特征及其原因,定义了沥青路面上出现的非均匀性类型;其次,在摊铺全幅路面上横向不同位置取料进行室内抽提试验,分析了沥青路面摊铺过程中材料变化特征,并与路用性能试验结果进行了相关分析;最后,采用灰关联分析方法研究了各因素对非均匀性(密度)的影响,并据此建立非均匀性的密度预测模型。

基于室内定位技术的智慧疏导系统设计

为提高紧急情况下人员的疏散效率,通过UWB室内定位技术、Eclipse开发平台、FengMap三维室内地图引擎,搭建基于室内定位技术的智慧疏导系统的框架,并结合智慧疏导系统的特点,设计出基于Dijkstra算法的智慧疏导模型和密度预测模型等。所设计的智慧疏导系统可以更好地结合火场动态变化实现对人员的智慧疏导,有效避免传统智能疏导系统的缺点,更高效安全地引导人员进行疏散。

Physical and chemical processes promoting dominance of the toxic cyanobacterium Cylindrospermopsis raciborskii

The freshwater cyanobacterium, Cylindrospermopsis raciborskii （Woloszyflska） Seenayya and Subba Raju is a common species in lakes and reservoirs globally. In some areas of the world it can produce cytoand hepatotoxins （cylindrospermopsins, saxitoxins）, making blooms of this species a serious health concern for humans. In the last 10 15 years, there has been a considerable body of research conducted on the ecology, physiology and toxin production of this species and this paper reviews these studies with a focus on the cylindrospermopsin （CYN）-producing strains. C. raciborskii has low light requirements, close to neutral buoyancy, and a wide temperature tolerance, giving it the capacity to grow in many lentic waterbodies. It also has a flexible strategy with respect to nitrogen （N） utilisation; being able to switch between utilising fixed and atmospheric N as sources of N fluctuate. Additionally this species has a high phosphate （DIP） affinity and storage capacity. Like many cyanobacteria, it also has the capacity to use dissolved organic phosphorus （DOP）. Changes in nutrient concentrations, light levels and temperature have also been found to affect production of the toxin CYN by this species. However, optimal toxin production does not necessarily occur when growth rates are optimal. Additionally, different strains of C. raciborskii vary in their cell quota of CYN, making it difficult to predict toxin concentrations, based on C. raciborskii cell densities. In summary, the ecological flexibility of this organism means that controlling blooms of C. raciborskii is a difficult undertaking. However, improved understanding of factors promoting the species and toxin production by genetically capable strains will lead to improved predictive models of blooms.

Failure probability analysis of coal crushing induced by uncertainty of influential parameters under condition of in-situ reservoir

The uncertainties of some key influence factors on coal crushing,such as rock strength,pore pressure and magnitude and orientation of three principal stresses,can lead to the uncertainty of coal crushing and make it very difficult to predict coal crushing under the condition of in-situ reservoir.To account for the uncertainty involved in coal crushing,a deterministic prediction model of coal crushing under the condition of in-situ reservoir was established based on Hoek-Brown criterion.Through this model,key influence factors on coal crushing were selected as random variables and the corresponding probability density functions were determined by combining experiment data and Latin Hypercube method.Then,to analyze the uncertainty of coal crushing,the firstorder second-moment method and the presented model were combined to address the failure probability involved in coal crushing analysis.Using the presented method,the failure probabilities of coal crushing were analyzed for WS5-5 well in Ningwu basin,China,and the relations between failure probability and the influence factors were furthermore discussed.The results show that the failure probabilities of WS5-5 CBM well vary from 0.6 to 1.0; moreover,for the coal seam section at depth of 784.3-785 m,the failure probabilities are equal to 1,which fit well with experiment results; the failure probability of coal crushing presents nonlinear growth relationships with the increase of principal stress difference and the decrease of uniaxial compressive strength.

Theoretical predictions of viscosity of methane under confined conditions

Density functional theory has been confirmed as a reliable approach in the descriptions of inhomogeneous fluids.By integrating the density functional theory into the revised local average density model, a theoretical approach is constructed to investigate the local shear viscosity in the confined conditions. In the density functional theory,the weighted density approximation for attractive part and the modified fundamental measure theory for repulsion contribution are adopted to accurately describe the inhomogeneous systems. By comparing with simulation data, the theoretical model is tested. In this work, the shear viscosities of methane are calculated in different external fields(on a hard wall, a solvophobic wall and in slit pores with different widths). In addition, the effects of temperature on the local density and viscosity are also considered. It shows that the effect of temperature on the shear viscosity is more obvious on solid surfaces. The calculation provides an approach to determine the viscosity under confined conditions, which is extremely significant in real industrial applications.

Using Organic Matter and pH to Estimate the Bulk Density of Afforested/Reforested Soils in Northwest and Northeast China

Regression models for predicting soil bulk density(BD) have usually been related to organic matter content, but it remains unknown whether soil acidity modifies this relationship, particularly for afforested/reforested soils. We measured soil BD along with organic matter content and pH in an afforested/reforested area in Northwest and Northeast China. Using these measurements, we parameterized and validated three BD models: the Adams equation, and exponential and radical models. Model validation showed that the Adams equation failed to predict the BD of the afforested/reforested soils, producing a large overestimation. Incorporation of soil pH into the Adams equation significantly improved its performance. The exponential and radical models parameterized by the measured data simulated soil BD quite well, particularly when soil pH was incorporated. However, incorporation of soil texture variables into these models did not improve model performance compared with the pH-modified models. This led to the conclusion that the Adams equation, exponential, and radical models with pH modification are applicable to afforested/reforested soils with various acidities.

Living on the edge： Effects of body size, group density and microhabitat selection on escape behaviour of southern leopard frogs Lithobates sphenocephalus

Models of optimal escape strategy predict that animals should move away when the costs of fleeing （metabolic and opportunity costs） are outweighed by the costs of remaining. These theoretical models predict that more vulnerable individuals should be more reactive, moving away when an approaching threat is further away. We tested whether escape behaviour （includ- ing ＇escape calling＇） ofLithobates sphenocephalus approached by a human was influenced by body size or the initial microhabi- tat that the individual was found in. Irrespective of their size, frogs in the open tended to remain immobile, enhancing their cryp- sis. Frogs in cover showed different responses according to their body size, but, contrary to our initial predictions, larger frogs showed greater responsiveness （longer flight initiation distance and distances fled） than small frogs. Small frogs tended to remain closer to water and escaped into water, while larger individuals were more likely to jump to terrestrial cover and call during escape. Density of frogs near the focal animal had no effect on escape behaviour. This study indicates a range of escape responses in this species and points to the importance of divergent escape choices for organisms which live on the edge of different environments .