基于模糊神经网络的农村电力短期负荷预测

为提高负荷预测精度,提出了一种新的模糊神经网络短期负荷预测模型。该模型将模糊系统和神经网络的优点融合在一起,并利用小生境遗传算法优化模糊神经网络参数,提升网络运算性能。某农村地区电力短期负荷预测的计算结果表明,该方法具有较好的预测效果。     

奶牛精确饲喂装置检测系统的研究

精确饲喂装置检测系统的核心技术是奶牛个体采食量检测技术.系统采用了螺旋输送料技术、非接触式的无线射频识别(RFID)技术和称重传感器技术.采食活动前,系统核对奶牛个体信息和启动螺旋输料系统进行投料,收集奶牛个体的采食数据,在上位机中利用Visval Basic 6.0 编写系统应用软件,实现对采食数据的接收、显示、存储和分析处理.     

Soil salinity related to physical soil characteristics and irrigation management in four Mediterranean irrigation districts

Irrigated agriculture is threatened by soil salinity in numerous arid and semiarid areas of the Mediterranean basin. The objective of this work was to quantify soil salinity through electromagnetic induction (EMI) techniques and relate it to the physical characteristics and irrigation management of four Mediterranean irrigation districts located in Morocco, Spain, Tunisia and Turkey. The volume and salinity of the main water inputs (irrigation and precipitation) and outputs (crop evapotranspiration and drainage) were measured or estimated in each district. Soil salinity (EC_e) maps were obtained through electromagnetic induction surveys (EC_a readings) and district-specific EC_a-EC_e calibrations. Gravimetric soil water content (WC) and soil saturation percentage (SP) were also measured in the soil calibration samples. The EC_a-EC_e calibration equations were highly significant (P < 0.001) in all districts. EC_a was not significantly correlated (P > 0.1) with WC, and was only significantly correlated (P < 0.1) with soil texture (estimated by SP) in Spain. Hence, EC_a mainly depended upon EC_e, so that the maps developed could be used effectively to assess soil salinity and its spatial variability. The surface-weighted average EC_e values were low to moderate, and ranked the districts in the order: Tunisia (3.4 dS m⁻¹) > Morocco (2.2 dS m⁻¹) > Spain (1.4 dS m⁻¹) > Turkey (0.45 dS m⁻¹). Soil salinity was mainly affected by irrigation water salinity and irrigation efficiency. Drainage water salinity at the exit of each district was mostly affected by soil salinity and irrigation efficiency, with values very high in Tunisia (9.0 dS m⁻¹), high in Spain (4.6 dS m⁻¹), moderate in Morocco (estimated at 2.6 dS m⁻¹), and low in Turkey (1.4 dS m⁻¹). Salt loads in drainage waters, calculated from their salinity (EC_dw) and volume (Q), were highest in Tunisia (very high Q and very high EC_dw), intermediate in Turkey (extremely high Q and low EC_dw) and lowest in Spain (very low Q and high EC_dw) (there were no Q data for Morocco). Reduction of these high drainage volumes through sound irrigation management would be the most efficient way to control the off-site salt-pollution caused by these Mediterranean irrigation districts.     

混凝土受拉软化特性对完全联合承载蜗壳非线性有限元分析的影响研究

完全联合承载蜗壳是一种为解决高HD值蜗壳结构钢衬厚度过大并保证其整体安全性的结构形式,但在我国工程中应用很少.三峡电站完全联合承载蜗壳由于结构尺寸大、HD值高,其工作机理复杂,结构分析难度较大.运用ABAQUS程序对该蜗壳结构进行了非线性有限元分析,比较在不同的混凝土材料软化特性曲线方案下的混凝土结构损伤情况及钢衬和钢筋应力,为结构三维非线性计算采用何种软化曲线计算以及钢筋的合理化配置提供依据.     

轴压比对矩形钢管混凝土框架受力性能影响的有限元分析

基于一榀单跨两层矩形钢管混凝土框架的抗震性能试验,利用通用有限元软件ABAQUS建立了框架的非线性有限元分析模型,模型中考虑了混凝土反复荷栽下的刚度退化.通过与试验结果的对比分析,验证了该模型的正确性,可以用于矩形钢管混凝土框架的结构分析中.利用该模型对不同轴压比下框架的骨架曲线进行了对比,并对其受力性能进行了分析,结果表明:随着轴压比的增大,框架的延性和承载力随之降低.     

Modeling subsurface drainage for salt load management in southeastern Australia

Subsurface drainage has been implemented in irrigation areas of South-eastern Australia to control water logging and land salinisation. Subsurface drainage has been identified as a major salt exporter from irrigated areas. The water table management simulation model DRAINMOD-S was evaluated to simulate daily water table depth, drain outflow, and salt loads by using experimental field data from a two year field trial was carried out in the Murrumbidgee Irrigation Area South-eastern Australia to study different options for subsurface drainage system design and management to reduce salt load export. Three subsurface drainage systems were modeled, deep widely spaced pipe drains, shallow closely spaced drains and deep pipe drains that were managed with weirs to prevent flow when the water table fell below 1.2 m. The reliability of the model has been evaluated by comparing observed and simulated values. Good agreement was found between the observed and simulated values. The model confirmed the field observations that shallow drains had the lowest salt load and that by managing deep drains with weirs salt loads could be significantly reduced. This work shows the value of the DRAINMOD-S model in being able to describe various drainage design and management strategies under the semi-arid conditions of South-eastern Australia. The model can now be used to investigate design and management options in detail for different site conditions. This will assist decision makers in providing appropriate subsurface drainage management policies to meet drainage disposal constraints within integrated water resources management planning.     

江阴市耕地重金属污染及其评价

江阴市在2004年对全市耕地和灌溉水的主要污染物质─重金属进行了较为全面的调查,对土壤和灌溉水进行了多种评价分析。结果显示:全市90%以上的耕地安全、清洁,97%以上的耕地没有受到重金属污染。并对调查结果进行了分析,提出了初步的对策与建议。     

中国水环境态势与方略

由于过去人类水资源利用的不合理,目前我国水环境已经恶化到极其严重的地步。文章系统地分析了我国水系、湖泊、海域的水环境状况,并针对我国实际污染情况提出了相应的防治措施     

高纬度地区多功能日光温室设计

高纬度地区的传统日光温室常由于结构设计不合理,冬季生产需要补温,果蔬种植和加工环节分离,运输中容易发生冻害,制约该地区温室的冬季生产。该文基于传统日光温室优点及存在问题,结合高寒地区气候特点,从温室结构优化和功能创新2方面提出新型日光温室设计方案。利用经典温室设计理论,结合生产实际,对采光角度、前屋面弧度、保温性能等进行优化,并对雪荷载、风荷载、屋面活荷载、作物吊挂荷载进行计算,利用结构分析软件midas计算温室结构的受力稳定性,对温室各参数设计的合理性进行验证。优化结果为:总跨度16 m,一层种植部分跨度9 m,生产加工部分跨度7 m,总高度6.5 m,前屋面主采光角37°,土地利用率达到1.7。该设计实现了高纬度地区温室冬季不加温种植果蔬,利用传统温室后墙的遮阴部分,创造地上、地下3层使用空间,显著提高了土地利用率,实现种植、加工、存储多种功能集成,是高纬度地区日光温室的一种创新尝试,可以作为棚室种植园区的核心节点温室。     

Using rainfall simulation and site measurements to predict annual interrill erodibility and phosphorus generation rates from unsealed forest roads: Validation against in-situ erosion measurements

The measurement of soil erosion rates under natural rainfall conditions is costly and time consuming. Data provided by rainfall simulation and static site measurements can be used to predict erosion rates under natural conditions, however the accuracy of this method is largely untested. This is especially true for erosion rates from unsealed forest roads. In this study, the values for a range of erodibility indices calculated from rainfall simulation experiments are compared to observed erodibility index values from 1 year of detailed in-situ erosion monitoring of seven different forest road types. The prediction of phosphorus generation rates from rainfall simulation and/or soil sampling was also evaluated. The results showed that a series of commonly used erodibility indices such as sediment per unit rainfall, sediment per unit runoff, sediment per unit EI₃₀, and sediment per unit rainfall energy were poorly predicted from the rainfall simulation experiments. Five of the six indices tested substantially overpredicted the observed erodibility at one site, a gravel road subjected to minimal traffic. For the other six road sites predictions were poor and highly variable, the coefficient of efficiency ranging from − 13.32 to 0.17 for these erodibility indices. A modified index, the ratio of sediment per unit rainfall energy to the mean rate of rainfall energy input, was able to predict annual erosion rates from six different road surfaces using rainfall simulation data with a coefficient of efficiency of 0.9. The results indicate that existing erodibility indices are not suitable for predicting observed erosion rates on forest roads using rainfall simulation data as collected in this study. It is argued that the modified index is more suited to sites (such as compacted roads) where interrill processes dominate, and erosion rates are less sensitive to peak flows. With respect to nutrient generation rates, rainfall simulation was able to accurately predict the observed proportion by mass of total phosphorus (TP) in runoff with a coefficient of efficiency of 0.96. Direct soil sampling of the road surface could also be used to predict the proportion by mass of TP in runoff. Concentrations of total nitrogen in forest road materials were found to be at the lower detection limit of the laboratory instruments.