滴灌下生物质改良材料对盐渍土水盐氮运移的调控效应

为探究生物质改良材料对滴灌盐渍土水、盐、肥运移过程的调控效应，采用土箱模拟试验，研究了水肥一体化滴灌条件下，生物炭和腐殖酸两种改良材料对盐渍土水、盐、氮运移和再分布过程及其时空分布特征的影响规律。结果表明：在滴灌条件下，盐渍土壤水盐的时空动态变化表现出明显的水分入渗驱动的盐分运移过程和蒸发扩散驱动的水盐再分布过程；铵态氮含量在时间上表现出先增大、后减小的变化趋势，在空间上的运移再分布特征较弱；硝态氮含量初始时空分布表现出与水盐相似的运移特征，受铵态氮硝化作用的多重影响，后期空间分布与铵态氮空间分布相似；生物炭通过提高土壤饱和导水率，增大了入渗阶段土壤水、盐、氮的运移速率和分布范围；腐殖酸通过提高土壤田间持水率增大了再分布过程土壤水、盐、氮的分布范围和强度，同时其对尿素的水解和硝化过程表现出更强的抑制效果。应用生物质改良材料在改变土壤物理性状进而调控滴灌土壤水盐运移的同时，还影响土壤氮素转化运移过程及其分布，这为水肥一体化滴灌盐渍农田的节水、控盐、减肥治理提供了理论基础。     

用简易诊断法检查判断液压系统各元件的工作性能

故障的排除首先在于判断，目前基层维修网点大多数没有检测仪器和设备，出了故障乱拆乱卸，导致液压元件工作失灵，甚至整车液压系统瘫痪。拖拉机液压系统产生故障的主要原因是液压元件工作性能恶化引起的。为此，介绍了在没有检测仪器和设备的条件下，如何应用简易诊断法检查判断各液压元件的工作性能。     

手动比例复合阀在中高压液压绞纲机中的应用

中高压液压技术在海洋捕捞机械—绞纲机中的使用推动了我国渔业机械的发展,手动比例复合阀在中高压液压技术上的应用则大大加快了液压绞纲机在国内渔业生产中的普及。目前,我国浙江、江苏、福建、广东和山东等省沿海渔民使用的绞纲机普遍采用带手动比例复合阀的液压系统。为此,对手动比例复合阀换向、溢流、调速集成等功能进行了分析。     

农机液压技术的应用与发展

液压技术的应用已成为现代化农业机械的典型标志。为此,介绍了农机液压技术的应用现状;并根据科学技术的发展,简要分析了农机液压技术的发展趋势。     

Impact on soil physical properties of using large-grain legumes for catch crop cultivation under different tillage conditions

In Central Europe, various plant species including large-grain legumes and their mixtures are grown as catch crops, particularly between grains harvested early and subsequent summer crops. This article investigates the question of how soil structure in the topsoil is influenced when catch cropping with large-grain legumes (experimental factor A: without catch crop, with catch crop) under different ploughless tillage conditions during catch crop seeding (experimental factor B: deep tillage/25–30 cm, shallow tillage/8–10 cm). Five one-year trials were performed using standard machinery at various sites in Germany. Soil core samples extracted from the topsoil in the spring after catch crop cultivation served to identify air capacity, saturated hydraulic conductivity and precompression stress. The above-ground and below-ground biomass yields of the catch crops were also determined at most of the sites. In addition, the soil compaction risk for the working steps in the experiments was calculated using the REPRO model.The dry matter yield of the catch crops varied considerably between the individual trial sites and years. In particular, high levels of dry matter were able to form in the case of early seeding and a sufficient supply of precipitation. The soil structure was only rarely affected positively by catch crop cultivation, and catch crops did not contribute in the short term to loosening already compacted topsoils. In contrast, mechanical soil stresses caused by driving over the ground and additional working steps used in cultivating catch crops often led to lower air capacity in these treatments. This is consistent with the soil compaction risks calculated using the REPRO model, which were higher in the treatments with catch cropping. Catch crop cultivation also only resulted in improved mechanical stability at one location. The positive effect of deep ploughless tillage on air capacity and saturated hydraulic conductivity, however, became more clearly evident regardless of catch crop cultivation. In order for catch crop cultivation with large-grain legumes to be able to have a favourable impact on soil structure, it is therefore important that cultivating them does not result in any new soil compaction. In the conditions evaluated, deep tillage was more effective at loosening compacted topsoil than growing catch crops.     

支管射流三通结构优化与试验

为了提高支管射流三通水力性能,改善滴灌的灌水均匀性,基于CFX数值模拟技术,对进口宽度为15 mm的支管射流三通进行结构优化.选取位差、劈距、劈尖半径和侧壁倾角为影响因素,通过四因素三水平正交设计了9组模型,边界条件设定为进口压力100 kPa.选取支管射流三通出口设计流量为评价标准,支管射流三通最优结构尺寸为位差5.5 mm、劈距113 mm、劈尖半径13 mm、侧壁倾角10°.此结构尺寸参数下的支管射流三通水力性能试验结果表明:在进口水压为100 kPa时,支管射流三通脉冲频率为148次/min,水头压力振幅为37.9 kPa,水头压力损失为16.7 kPa,出口流量为0.698 L/s;支管射流三通所接滴灌带长度为60 m时,与普通支管三通相比,支管射流三通的灌水均匀系数提高了2.78%,流量偏差率降低了4.72%.该研究可为射流技术在脉冲滴灌系统的研究、开发与应用提供理论依据.     

基于Simulink的液压系统建模与仿真

针对农业机械中液压系统结构复杂、研发周期长等问题,通过分析农业机械中液压回路各个组成元件特性,基于Simulink构建元件动态数学模型。对液压回路进行研究,分析了液压回路在不同元件参数下的动态性能,为优化液压回路系统提供参考。     

抛物线形混凝土衬砌渠道标准化结构形式研究

通过实例比较了2种常用的抛物线形渠道水力最佳断面参数,得出二次抛物线渠道的水力性能优于半立方抛物线形渠道,并推导出了二次抛物线渠道实用经济断面的计算公式,提出了详细的计算步骤,给出了二次抛物线渠道实用经济断面水力计算表以供设计人员使用。同时,根据渠道工程实际应用情况和现行规范要求,提出了抛物线形混凝土衬砌渠道标准化结构形式,计算得出了常用抛物线形混凝土渠道结构尺寸、不同比降流量表,在实际工程应用中可根据设计渠道的具体情况进行选用。     

3D打印技术在水利水电工程施工中应用研究

对3D打印技术进行应用研究,阐述其精度、强度和速度等关键性能指标合理性,能够有效避免特殊形式结构部位的施工带来的成本、工期及质量问题,增加工程效益,并对溢流堰面特殊部位计算表面曲线轮廓,进行实验3D打印,最后总结3D打印在水利水电工程施工中的优势。