荷电液滴蒸发破碎过程的数学模型

针对荷电液滴蒸发破碎过程伴随的电荷衰减、质量和热量的传递问题进行了理论分析,得出荷电液滴电荷衰减规律,建立荷电液滴蒸发破碎过程的数学模型.建立重力作用下作平抛运动液滴的轨道模型,得出了水平方向与竖直方向上的最大输运距离.研究表明,液滴所带电荷是随时间作指数规律衰减,液滴电导率越高,介电常数越小,电荷衰减越快;液滴完全蒸发所需时间基本上与液滴初始半径的平方成正比.荷电液滴在蒸发过程中,临界电量随液滴温度的增加而减小,当液滴带电量q大于等于临界电量qc时,蒸发过程中发生库仑分裂,并实现了对库仑分裂时刻的预测.     

形态可重构移动机器人行走机构设计与分析

基于用移动机器人代替农民在农田复杂环境下进行劳作、减轻农民作业负担的理念,提出一种轮/履形态可重构移动机器人。该移动机器人由4个相同结构的轮/履形态可重构行走单元以及车体组成,具有轮式和履带式2种行走姿态,以便适应野外复杂地形。轮/履运动形态的可重构可以通过轮/履形态转换装置实现。建立了形态可重构单元的运动学模型、数学模型以及动力学模型,并推导了行走单元的数学模型,得到行走单元机器人在攀越台阶越障时机器人摆杆角度与台阶高度h的关系,以及能够攀爬的坡度范围。在Simulink以及ADAMS中建立了行走单元虚拟样机以及仿真环境,并设计了样机。通过对虚拟样机仿真以及Matlab理论值计算,末端速度和加速度的仿真值与理论值误差的数量级仅在10-8～10-6之间,验证了其数学模型以及运动学模型的正确性。     

台风“凤凰”路径强度变化对太湖北岸风雨影响的诊断

为探讨2014年第16号台风“凤凰”运动路径怪异和数次登陆强度不变的特点,了解其给太湖北岸地区带来的风雨影响,通过对台风环境背景场的天气学分析和物理量诊断,对16号台风“凤凰”的路径动态、强度变化、结构特征进行分析。结果表明：受副高进退和引导气流作用,台风“凤凰”沿着副高外围,先后经历西进、北上,东出的运动,深层引导气流能较好的指示台风的运动。台风“凤凰”自身体积较小,发生发展前期海温偏低,海洋热容量低,温度条件不利于台风的增强。同时,台风流场结构极为不对称,随着垂直风切的增强,台风强度减弱,并经过数次登陆,破坏了环流结构,总体强度难以增强。由于台风路径偏东,强度偏弱,影响范围较小,水汽输送条件不利,且无冷空气配合,太湖北岸地区在此次台风过程中以中雨为主,风力影响集中在台风环流中心附近,影响总体较小。     

Recommended urban storm water infiltration devices for different types of run-off under varying hydrogeological conditions

Background, aim, and scope  The decentralised near-natural infiltration of storm water in urban areas over a long-term period can cause local pollution of soil, seepage water and groundwater due to heavy metals (e.g. Pb, Zn, Cu), polycyclic aromatic hydrocarbons (PAH), petroleum hydrocarbons and readily soluble salts, which compounds are partly classified as hazardous. The aim of this paper is to present a recommendation matrix for suitable storm water infiltration devices. The scope is limited to eight different run-off types and two different infiltration devices (swales and trenches with three different trench-filling materials) under two different hydrogeological conditions (high adsorbing soil with low permeability, low adsorbing soil with high permeability). The examined run-off types are sub-divided as follows: run-off from unpaved areas (gardens, grassed areas, cultivated land); green roofs, aluminium roofs; roofs without zinc gutters and down-pipes; roofs with zinc gutters and down-pipes; copper roofs; zinc roofs and trafficked areas (cycle and pedestrian ways, yards, car parks and residential roads). The recommendation matrix should assist decision-makers such as city planners, architects and private house builders. Materials and methods  The potential for storm water infiltration to pollute soil, seepage water and groundwater is investigated with long-term 3-D numerical water flow and chemical transport modelling in unsaturated and saturated zones over 50 years, which were already presented by Zimmermann et al. (Water Sci Technol 51(2):11–19, 2005). The recommendation is based on a comparison between modelling results and several guideline values prepared by several German authorities. The evaluation process leads to four hazard levels regarding the impact on topsoil (i.e. first 20 cm of the soil), on seepage water (1 m below the infiltration device) and on groundwater (at the unsaturated–saturated boundary). Results  The recommendation matrix consists of 56 individual statements. Relating to dissolved organic substances like phenanthrene and fluoranthene, the infiltration of trafficked areas run-off is critical. The infiltration of metalliferous run-off has a high hazard accumulation potential. Here the storm water infiltration via sub-ground of low permeability and high adsorbing soil material is critical for seepage water in any case; the infiltration of zinc roofs run-off via trench infiltration devices is even critical for groundwater at 4 m depth. Sub-ground of low permeability and high adsorbing soil material has a lower potential hazard in terms of storm water infiltration from roof run-off. The storm water infiltration via swales effects a very large accumulation of heavy metals in the topsoil. The storm water infiltration via trenches leads to the accumulation of hazardous substances in the deeper sub-ground, particularly where the trench-filling material has low adsorbing capacity and high permeability. Discussion  The transferability of the results to other sites depends particularly on the hydrogeological conditions. Before using the recommendation matrix, details of the hydrogeological conditions should be collected. The long-term simulation process is simplified by several impact factors such as non-constant rainfall, soils heterogeneity, macro-porous flow, particle-bounded transport and microbiological decomposition. Conclusions  Based on the scale of risks to soils, seepage water and groundwater, the matrix should be used in the selection of the roof construction materials and appropriate storm water infiltration devices so that the environmental risks can be minimised. If the sub-ground has a high permeability and low adsorption capacities, the infiltration of metalliferous roof run-off water is, in general, not advisable without putting treatment facilities in place upstream. Thus, architects need to realise that the choice of a suitable infiltration device depends, on the one hand, on the type of run-off and, on the other hand, on the hydrogeological condition and the building materials. Recommendations and perspectives  Replacement of the topsoil in swale infiltration devices is recommended because, in particular, heavy metal (zinc) in run-off from roofs with zinc gutters and down-pipes accumulates in the soil matrix. The replacement interval depends on the hydrogeological conditions and, for this run-off example, lies between 10 and 20 years. If infiltration is essential, constructing special treatment facilities upstream can be an alternative. The existing numerical model could be adapted to suit other site-specific materials and be enhanced regarding several complex impact factors.     

副热带高压对“灿鸿”和“苏迪罗”台风路径的影响

本文利用美国国家环境预报中心(NCEP)6 h一次的全球分析资料及其10 d低通滤波资料对"灿鸿"和"苏迪罗"台风期间的环流场进行分析。结果表明,副高减弱和加强是台风路径北折和维持西行的原因,且在滤波场上该作用更加明显,对台风业务预报更有帮助。     

A Newly Developed Differential Steering Rubber-tracked Agriculture Tractor

1　Introduction　　 Since Caterpillar Inc unveiled its Challenger35and4 5agricultural tractors in1 994 ,thedifferential steering rubber- tracked tractor has become a new member of the farm tractorfamily.John Deere officially introduced its80 0 0 T Series of tractors in1 996 and so did CaseIH.YITUO Group,the biggestagriculture tractor manufactory in china,has also developed asimilar kind of tractor.The tractor,DFH- 1 30 2 R,is under testing now and will be availablenext year.This paper …     

MAX125在发电机励磁调节器中的应用

发电机励磁调节器的主要任务是维持发电机机端电压恒定。发电机励磁调节器中,需要多通道同步采样数据。A/D转换器MAX125可以很好地满足通道同步采集数据的要求。为此,介绍了MAX125的特性及其在发电机励磁调节器中的具体应用。     

“文学自觉”再思考——以诗、骚、赋为重点

日本学者铃木虎雄和鲁迅先生提出魏晋文学自觉说以来聚讼颇多。参与争论的学人忽视了不同历史阶段下思想文化发展背景,但没有把握住当时文学发展的总体特点,只是搜集分析一些具体的材料就得出结论。文章梳理先秦至建安三国时期文学发展的大致特征、脉络,可以为思考文学自觉提供另一条思路。     

我国环境现状与环评走势分析

结合我国的环境现状,从环评力度、管理、层次、规划、信息及公众参与机制等方面对新形势下的环境评价走势进行分析。     

农村地区学校田径运动发展瓶颈及发展策略研究

田径运动是一项最基本的体育运动项目，也是我国大中小学体育课程中必不可少的教学内 容，田径运动也有利于学生增强身体素质，还可以有效锻炼学生的意志力与优良品格。中学开始由于 升学压力和其他因素导致学生对于田径运动的参与度不高，尤其是农村地区的学校田径运动的发展 受到的限制因素更多。分析农村地区学校田径运动发展的瓶颈，针对具体的问题，提出农村地区学校 田径运动的发展策略，以期为我国农村地区学校的田径运动发展提供一些理论支持。