基于改进多父辈遗传算法的农机调度优化方法

农机装备跨区作业存在作业任务重、转移范围大、作业时效性强等问题,传统的农机调度缺乏科学合理的调配方案.该研究开展了基于改进遗传算法的多机协同作业任务调度方法研究.首先对多块农田需连续进行多种生产任务的问题进行分析,建立在农机数量、转移距离、作业准备时间及作业时间等约束条件下的时间窗农机作业调度模型;然后以最小化作业时间...     

Rapid determination of estrogens in milk samples based on magnetite nanoparticles/polypyrrole magnetic solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry

In this study, a nanocomposite of polypyrrole-coated magnetite nanoparticles (denoted as MNPs/PPy) was prepared and employed as magnetic solid-phase extraction (MSPE) sorbent for extraction of estrogens from milk samples. Because the polypyrrole coating possessed a highly π-conjugated structure and hydrophobicity, MNPs/PPy showed excellent performance for the estrogen extraction. Estrogens could be captured directly by MNPs/PPy from milk samples without protein precipitation. Moreover, the extraction could be carried out within 3 min. Thus, a rapid, simple, and effective method for the analysis of estrogens in milk samples was established by coupling MNPs/PPy-based MSPE with liquid chromatography-tandem mass spectrometry (LC-MS/MS). The limits of detections for estrogens investigated were in the range of 5.1-66.7 ng/L. The recoveries of estrogens (concentration range of 0.5-20 ng/mL) from milk samples were in the range of 83.4-108.5%, with relative standard deviations ranging between 4.2 and 15.4%.     

Prediction of daily reference evapotranspiration by a multiple regression method based on weather forecast data

Prediction of daily reference evapotranspiration (ET ₀) is the basis of real-time irrigation scheduling. A multiple regression method for ET ₀ prediction based on its seasonal variation pattern and public weather forecast data was presented for application in East China. The forecasted maximum temperature (T _max), minimum temperature (T _min) and weather condition index (WCI) were adopted to calculate the correction coefficient by multilinear regression under five time-division regimes (10 days, monthly, seasonal, semi-annual and annual). The multiple regression method was tested for its feasibility for ET ₀ prediction using forecasted weather data as the input, and the monthly regime was selected as the most suitable. Average absolute error (AAE) and root mean square error (RMSE) were 0.395 and 0.522 mm d^?1, respectively. ET ₀ prediction errors increased linearly with the increase in temperature prediction error. A temperature error within 3 K is likely to result in acceptable ET ₀ predictions, with AAE and average absolute relative error (AARE) <0.142 mm d^?1 and 5.8%, respectively. However, one rank error in WCI results in a much larger error in ET ₀ prediction due to the high sensitivity of the correction coefficient to WCI and the large relative error in WCI caused by one rank deviation. Improving the accuracy of weather forecasts, especially for WCI prediction, is helpful in obtaining better estimations of ET ₀ based on public weather data.     

沙地刚性轮构型仿生设计及牵引性能数值分析

为了提高车轮牵引性能,改善车辆在松散沙土介质环境的通过能力,该文以善于沙地奔跑的鸵鸟足部关键部位—足趾甲为仿生原型,通过仿生优化轮刺结构,设计出具有高牵引性能的仿生轮刺式沙地刚性轮,并以一种模拟月壤作为试验松散沙土介质材料,采用离散元软件PFC2D?的内置语言FISH和相关命令,建立了适用于非规则结构刚性轮的轮壤相互作用动态模拟系统,并获得试验验证。通过仿生轮刺式刚性轮与模拟月壤相互作用离散元模拟,并与矩形轮刺式刚性轮模拟结果对照,从轮下模拟月壤颗粒细观运动、接触力场、速度场以及车轮挂钩牵引力角度,验证了仿生轮刺式刚性轮具有优越的牵引性能,在车轮滑转率50%的稳定运行状态下,仿生轮刺式刚性轮的牵引性能可提高5.2%左右。该研究为提高刚性轮在松散沙土介质环境中的牵引性能提供了全新设计和研究手段。     

中国农业循环经济标准体系构建与对策

农业循环经济标准体系构建是开展农业循环经济的基础性和统领性工作,目前中国在农业循环经济领域已积累了较多成功经验,但尚未建立完整的标准体系。该文剖析了中国农业循环经济标准体系构建所存在的核心问题,基于农业产业链和农产品生命周期视角,系统阐述了中国农业循环经济领域的标准体系构建过程、基本组成、结构维度(包含产业链维、产业维、层次维)、制定原则和结构框图,构建了包括基础、管理通用、产业链链接、方法与专用等4个层次的农业循环经济标准体系;最后详细解析了农业循环经济、生态农业及有机农业标准关系的关系;并根据中国循环农业产业发展的实际需求,按照轻重缓急原则提出亟需制定的相关标准建议,可为中国农业循环经济标准化、规范化发展提供理论依据。     

几种土壤结构改良剂的制备及其效用

近年来不少地区土壤中有机质减少,土壤结构状态变劣,成为生产上极需解决的问题。改良土壤结构,除多施有机肥料^[3,4],种植牧草等措施外,施用以天然的有机物及无机物制备的,或人工合成的高分子有机化合物,也是很有效的办法^[1]。本文介绍了几种土壤结构改良剂的研制及其效应,初步证明施用土壤结构改良剂能有效地增加土壤中团粒结构,改善作物生长条件,有利于提高产量。     

广州薇甘菊潜在空间分布预测分析

薇甘菊是广州最主要的林业有害入侵植物之一。基于广州薇甘菊的实际调查数据及其对应的14个环境因子的定量关系,利用主成分分析确定主要影响因子,据此结合GIS预测其潜在分布区。结果表明:海拔、年平均温度、年均日照时数、以及降水因子年平均降水量、最湿季度降水量、最干季度降水量这6个因子对薇甘菊的分布影响最大。薇甘菊的高度适生区为黄浦区、萝岗区;适生区分布在广州南沙区、天河区,以及增城市、从化市、番禺区局部地区;荔湾区、海珠区以及番禺和从化局部地区为非适生区。广州96%以上的区域均适合薇甘菊的生长,潜在分布区与实际分布区有较好的对应。     

轮式车辆传动系自激振动强度及其影响因素分析

建立了车辆传动系的数学模型,并用平均法求解,得出了车辆传动系自激振动振幅的表达式,研究了影响自激振动振幅的因素及其影响规律,并与相平面分析的结果相比较,验证了该振幅表达式的正确性。当滑转率大于临界滑转率时,地面附着系数随滑转率增加而减小的斜率车辆平均滑转率、发动机转速三个因素增大,自激振幅随之增大。     

施药方法及土壤含水对燕麦畏与氟乐灵挥发及光解性的影响及其药效

采用培养皿中燕麦幼芽及室内盆栽法,探讨不同施药方法及土壤含水量对燕麦畏、氟乐灵挥发度与光解性的影响及其药效。结果表明,燕麦畏与氟乐灵的药效发挥与在阳光下暴露的时间长短成负相关。燕麦畏的药效在土壤湿度5～30％间,随土壤湿度增加而降低。在土壤湿度为5％时,药后4h内耙地混土,药效最好。而氟乐灵药效发挥受土壤湿度影响不大,发挥药效的关键因素是施药后耙地混土。     

辣椒连作研究进展

辣椒是一种重要蔬菜作物,由于连年耕种辣椒存在连作障碍问题;国内外学者对辣椒连作问题作了较深入的研究.针对国内外辣椒连作的研究进展,主要从土壤微生物环境、连作土壤的微生态条件、辣椒自毒分析和化感作用、辣椒免疫系统及自身抗性作用机理等方面分别进行了综述,并对其今后的发展方向作了展望.