Divergent effects of defoliation intensity and frequency on tiller growth and production dynamics of Pascopyrum smithii and Hesperostipa comata

Rotational stocking theoretically enables regrazing of regrowth, but regrowth may be limited in xerophytic vegetation. We tested the hypothesis that regrowth would be slow and fixed in Hesperostipa comata (a caespitose, drought‐tolerant grass), while growth would be flexible in Pascopyrum smithii (a rhizomatous, less drought‐tolerant grass) under increasing defoliation and moisture, by assessing tiller growth rates, population dynamics and plant yield on marked plants in a Dry Mixed Grass prairie. Plots were clipped in late summer to simulate a deferred control, or intermittently during the growing season (May–August) at high intensity–low frequency (HILF), low intensity–high frequency (LIHF) or high intensity–high frequency and crossed with two water treatments (ambient and addition) in both a xeric upland and a mesic lowland. Growing season defoliation increased tiller growth rates of P. smithii in the upland, whereas HILF and LIHF reduced growth in the lowland. All defoliation regimes increased tiller growth for H. comata. Tiller populations of H. comata increased with frequent defoliation, while tiller populations of P. smithii decreased regardless of defoliation regime. Frequent defoliation, regardless of intensity, reduced yield relative to the deferred control for both grasses. While water addition consistently increased growth rates and reduced differences in tiller number among defoliation treatments, the regrowth of both grasses remained similar under varied defoliation with ambient moisture. High moisture conditions also promoted regrowth more in P. smithii compared to H. comata. In summary, neither grass species displayed an inherently fixed or flexible tiller or plant yield response in response to defoliation or moisture.     

青饲料收获机切碎辊刀具的优化设计及试验

青饲料收获机切碎辊刀具的设计直接影响秸秆的切割质量。刀具与秸秆接触时的受力分析表明，切割力与秸秆的压应力有关，而压应力不仅与秸秆物理特性有关，也与刀刃的倾斜角有关。利用Ansys-Workbench有限元软件进行仿真分析，结果表明,当刀具材料为65Mn、刀具厚度为8 mm、刀尖倾斜角度为30°时，刀具的等效应力最小。以秸秆层厚度、刀具倾斜角、秸秆含水率为试验因素，以切割装置切割秸秆时的扭矩值为试验指标，通过正交试验及交互作用分析，确定了因素对指标影响的主次关系为：A2>C2>B2>A>BC>AC>C>B，当秸秆层厚度7.5 cm、刀具倾斜角度35°、秸秆含水率35%时，刀辊扭矩值最小。验证试验结果表明选取的较优参数组合真实可行。该研究为新型刀具及防堵刀辊的机理研究提供了理论和试验借鉴。     

大豆植株分杈数自动提取算法研究

根据大豆植株分杈个数可以预估大豆的产量。为了满足现代农业预测农产品产量的需要,本文提出一种大豆植株分杈数自动提取算法,即首先将采集到的大豆植株图片进行灰度变换、滤波、阈值分割得到二值图像,再进行形态学中的闭运算操作得到大豆植株的轮廓,然后基于Zhang并行快速细化算法提取骨架,最后借助改进的角点检测算法对大豆植株的所有分杈点进行标记并自动统计分杈数,仿真结果与大豆植株实际分杈点一致。     

基于知识工程的旋耕机刀辊的快速设计系统研究

为了提高旋耕机刀辊的设计效率，建立了一种基于知识工程的对旋耕机刀辊的快速设计系统：在查阅整理旋耕机刀辊设计流程及规则知识的基础上，建立刀辊参数库、规则库、实例库等知识库，选用SQL语言对知识库进行添加、查询、修改；应用基于规则和实例的混合推理方法，以SolidWorks和Visual Studio为系统开发平台，应用API二次开发工具和VB.NET语言开发刀辊的快速设计系统，实现尺寸驱动模型变更和不同农耕农艺要求下刀辊的参数化快速设计。在Intel i5处理器、系统内存8 GB配置环境下，快速设计系统运行 3~5 min即可设计出满足用户需求的刀辊CAD模型并输出文件，满足使用需求。     

旋转编码器在回转体回转角度测量中的应用

针对回转体回转角度测量的实际情况，研制了新型回转体回转角度测量仪。该测量仪是以光、机、电为一体的旋转编码器作为传感器，测量回转体的回转角度。这种测量输出的信号为数字信号，克服了零漂、测量准确度低等缺点，提高了测量的准确度和可靠性。     

提高减速箱中橡胶油封-金属转轴密封性能的方法

减速箱橡胶油封漏油是一个尚未解决的一个棘手问题 .从摩擦学的角度分析 ,漏油的原因主要是油封与转轴接触部位不符合摩擦学的要求 ,造成此处的摩擦系数过高 ,油封磨损过快 .介绍了几种降低橡胶油封与转轴之间摩擦系数的方法     

Crop structure in winter oats and the effect of nitrogen on quality-related characters

The relationship between panicle structure and oat grain quality characteristics was examined in a winter oat (Avena sativa) experiment, cv. Gerald, fertilized with 80 and 200 kg/ha N. Spikelets on each whorl were counted and separated into primary, secondary, and tertiary grains, which were counted and weighed, and the kernels extracted manually and weighed. Tiller and whorl rank had relatively small effects on weight per grain and kernel content. Nitrogen application significantly increased weight per primary and secondary grain on the main stem and T1, the first tiller, while spikelet and grain numbers increased only on T1. However, weight per grain and kernel contents in all whorls on both the main stem and T1 were not significantly affected by nitrogen. Although kernel contents were significantly affected by nitrogen application on some occasions, increases and decreases were less than 2.5%. Across the whole plant, numbers of primary and secondary grains increased at the higher nitrogen application, but weight per primary grain and kernel contents were unaffected. However, weight per secondary grain significantly increased at the higher nitrogen application, thus improving uniformity of grain size which is of value to millers.     

楔形减阻旋耕刀设计与试验

为解决旋耕整地作业阻力大、能耗高等问题,该文基于旋耕刀理论受力模型设计了一种楔形减阻旋耕刀。采用Inventor和HyperMesh软件分别创建国标旋耕刀及楔形减阻旋耕刀的三维模型和切削土壤模型,分析了楔形减阻旋耕刀的应力强度,对比了国标旋耕刀与楔形减阻旋耕刀的切削阻力。通过田间试验对比了国标旋耕刀与楔形减阻旋耕刀的扭矩、功耗与碎土率。结果表明:楔形减阻旋耕刀所受最大应力为29.49 MPa,远小于材料的屈服强度430 MPa,在保证刀身强度的前提下,与国标旋耕刀相比,楔形减阻旋耕刀质量减轻8.3%;平均切削阻力较国标旋耕刀下降10.65%。在相同工况条件下,楔形减阻旋耕刀的平均扭矩为648.916 N·m,较国标旋耕刀下降11.35%;楔形减阻旋耕刀的平均功耗为67.3kW,较国标旋耕刀下降9.29%,碎土率提高4%,耐磨性能与国标旋耕刀持平,能够达到在降低作业功耗的同时,提高耕作质量并保证刀具使用寿命。     

家具构件旋转摩擦焊接接合性能研究

圆棒榫旋转摩擦焊接技术具有加工速度快,胶合强度高,且无需任何石化类胶黏剂的优势。以南方松为基材,以双圆榫旋转摩擦焊接和白乳胶胶合的"T"型、"L"型实木构件为研究对象,通过力学强度测试对比两种不同节点接合方式的接合强度以及不同插人深度对圆榫旋转摩擦焊接强度的影响。结果表明,圆棒榫旋转摩擦焊接技术是一种颇具潜力的家具构件连接方式。