1980年以来中国大宗作物空间格局变化分析

利用1980～2014年间的大宗作物(玉米、水稻、小麦、棉花、油菜)面积数据,以省级行政区为研究单元,采用多种数理统计和GIS空间分析技术,结合同期作物之间的竞争性用地关系,对全国上述五类大宗作物的空间分布格局及其变化特征进行分析.研究结果表明:玉米的空间分布相对较均衡;小麦的空间格局总的变化不明显但是省际分布最不均衡;棉花近30 a来空间格局变化极其显著,其面积重心从河南境内不断地向西北地区移动,目前位于甘肃省境内;油菜的面积重心自湖北境内不断地向南推移到湖南境内,水稻的面积重心则自江西境内逐渐向北移动到湖北境内.另外,部分区域的同期作物(如油菜与小麦、棉花与春玉米)空间格局变化存在明显的“消-长”关系,特别是在甘肃和内蒙,油菜小麦的面积变化有着极强的负相关性,其pearson系数低于-0.8.作物种植的成本收益变化是造成这些大宗作物空间格局变化的主要原因,城市化发展的程度、农民非农就业机会的高低、同期作物之间的比较效益差距等也是这些大宗作物时空格局产生变化的重要原因.     

Optimization of thermal performance of the parabolic trough solar collector systems based on GA-BP neural network model

The aim of this paper is to optimize the thermal performance (system output energy, thermal efficiency, and heat loss of cavity absorber) of parabolic trough solar collector (PTC) systems in order to improve its thermal performance, based on the genetic algorithm-back propagation (GA-BP) neural network model. There are a number of undefined problems, fuzzy or incomplete information and a complex thermal performance of the PTC systems. Therefore, the thermal performance prediction of the PTC systems based on GA-BP neural network model was developed. Subsequently, the metrics performances have been adopted to comprehensively understand the algorithm and evaluate the prediction accuracy. Results revealed that the GA-BP neural network model can be successfully used to predict the complex nonlinear relationship between the input variables and thermal performance of the PTC systems. The cosine effect has a great influence on the thermal performance; thereby the geometrical structure of the PTC systems was optimized. It was found that the optimized geometrical structure was beneficial to improve the thermal performance of the PTC system. In conclusion, the GA-BP neural network model has higher prediction accuracy than the other algorithm and it can be feasible and reliable.     

自组织理论和耗散结构理论及其地学应用

介绍了自组织、自组织临界态理论和耗散结构理论的概念及其近年来在地学特别是地球化学研究领域的应用情况     

非线性在特大型船闸运行水污染控制中的应用

应用非线性动力学、分形理论、混沌学,研究了特大型船闸运行水污染系统,结合葛洲坝特大型船闸运行系统自组织特征和水污染事件,论述了船闸水污染非线性、分形特征,建立了动力方程、水质预测预报模型,指出常规理论方法研究中存在的问题,提出了水污染系统非线性研究是今后着重需要深入探讨研究的领域,具有重要的实用价值.     

加速车道几何参数对合流区交通状况的影响分析*

为分析加速车道几何参数对合流区交通状况的影响,基于实验方案和效率-冲突率评价指标,构建实验平台并标定对应参数,结合实际交通场景数据及速度偏差和交通冲突相关系数指标,验证实验平台有效性。结果表明:w,l随主线流量增大而增大,合流区交通状况逐步变好;随主线流量增大,在l=60 m时,w对合流区交通状况的影响较大且整体交通状况较差,而l相应增大后,w对交通状况影响较小。     

一种纳米气溶胶发生系统的设计及性能测试

气溶胶发生系统是校准大气颗粒物测量仪器、研究纳米颗粒物特性和开展烟雾箱模拟实验的必备仪器之一.针对现有气溶胶发生仪器稳定性差和不利于外场监测等缺点,本研究设计了一款新型纳米气溶胶发生系统(包括气溶胶发生器和扩散干燥管),并通过搭建实验系统对该仪器的工作性能进行了测试.在性能测试中使用氯化钠(NaCl)-水溶液和癸二酸二辛酯(DOS)-异丙醇溶液分别产生固态NaCl和液态DOS气溶胶,利用扫描电迁移率粒径谱仪测试生成气溶胶的粒径分布.测试结果表明,通过调节溶液浓度(0.01～0.50 g·L-1)和载气流量(1.64～3.67 L·min-1),生成不同大小(几何平均粒径:25～51nm)和不同数浓度(106～107个·cm-3)的气溶胶.对仪器稳定性能测试发现,在3 h的测试时间里生成的气溶胶几何平均粒径变化小于6%,数浓度变化小于12%.     

指数型刚度非线性隔震系统的隔震性能分析

目前应用的隔震系统往往处于非线性工作状态,隔震设计仍基本停留在线性隔震理论的基础上,使隔震系统的设计存在诸多缺陷,因此加强对非线性隔震理论的研究十分重要。用指数型刚度表示的隔震系统在非线性隔震系统中有较强的代表性,只要改变指数参数的正负号就可以简单地反映出隔震材料或隔震元件的硬特性或软特性。通过对隔震系统建立的数学模型在核爆近区和远区的地冲击加速度作用下的隔震性能进行数值计算分析,证明隔震系统刚度特性对隔震性能有很大影响,该分析方法对隔震材料的选择和系统的设计有重要的参考价值。     

Emission source-based ozone isopleth and isosurface diagrams and their significance in ozone pollution control strategies

In the past decade, ozone (O₃) pollution has been continuously worsening in most developing countries. The accurate identification of the nonlinear relationship between O₃ and its precursors is a prerequisite for formulating effective O₃ control measures. At present, precursor-based O₃ isopleth diagrams are widely used to infer O₃ control strategy at a particular location. However, there is frequently a large gap between the O₃-precursor nonlinearity delineated by the O₃ isopleths and the emission source control measures to reduce O₃ levels. Consequently, we developed an emission source-based O₃ isopleth diagram that directly illustrates the O₃ level changes in response to synergistic control on two types of emission sources using a validated numerical modeling system and the latest regional emission inventory. Isopleths can be further upgraded to isosurfaces when co-control on three types of emission sources is investigated. Using Guangzhou and Foshan as examples, we demonstrate that similar precursor-based O₃ isopleths can be associated with significantly different emission source co-control strategies. In Guangzhou, controlling solvent use emissions was the most effective approach to reduce peak O₃ levels. In Foshan, co-control of on-road mobile, solvent use, and fixed combustion sources with a ratio of 3:1:2 or 3:1:3 was best to effectively reduce the peak O₃ levels below 145 ppbv. This study underscores the importance of using emission source-based O₃ isopleths and isosurface diagrams to guide a precursor emission control strategy that can effectively reduce the peak O₃ levels in a particular area.     

综合污染指数计算公式的改进

针对水环境质量的算术均值污染指数和几何均值污染指数评价方法的缺点,提出采用新模式计算综合污染指数,用此方法对南通市的内河水质进行分析。并与均值污染指数法和几何均值综合污染指数法进行了比较,效果显著。