圆盘通孔叶轮的能量转换特性

为研究圆盘通孔叶轮的流动及能量转换特性,以能量转换及定量的数学分析为依据,通过对圆盘通孔叶轮内介质的运动规律及受力分析,证明了此类叶轮对水流做功不同于叶片泵的做功机理,即叶轮以产生哥氏加速度的作用力对水做功,且叶轮做功量与水流机械能增量存在等值关系.同时,以理论方式揭示了该类泵的一些不同于离心泵的外特性:叶轮产生的理论扬程不随流量变化而变化;在相同的转速与叶轮直径条件下,圆盘通孔泵将产生更高的扬程.有关圆盘通孔泵的理论结果有助于深化叶轮流动的研究方法,为分析圆盘通孔叶轮内的流动及叶轮做功特性提供一定的理论依据.     

Impact of mowing frequency on arthropod abundance and diversity in urban habitats: A meta-analysis

Urbanization is an important driver of global insect decline. Yet, recent studies have demonstrated the potential of greenspaces in cities to promote biodiversity conservation. One of many factors negatively affecting arthropods in urban areas are unsuitable habitats, as non-woody greenspaces predominantly consist of manicured lawns. Maintenance practices such as high mowing frequencies, can have direct and indirect negative impacts on the local flora and fauna. The present study examines the effects of different mowing regimes on arthropod abundance and diversity by conducting meta-analyses of studies assessing the effect of mowing on arthropod abundance (46 datasets) and taxa richness (23 datasets) in urban environments. Due to a geographical bias in the literature, only data from the temperate, northern hemisphere are analyzed. While our meta-analysis on arthropod abundance showed a medium positive effect (effect size: g = 0.54) of reduced mowing, the cumulative positive effect of reduced mowing on arthropod taxa richness was large (g = 1.25). Grouping the studies not only resulted in lower heterogeneity, but also showed that manicured lawns disproportionately favor the abundance of “pest” species as well as ground-dwelling arthropods. There was also a significantly higher abundance of winged insects on sites with reduced mowing as compared to arthropods without wings. Overall, the findings of the present meta-analysis strongly support the notion that a reduction in mowing frequencies in urban greenspaces benefits insect biodiversity.     

辣椒切片机设计与试验

针对新疆地区辣椒烘干时间长、人工切片效率低、工作量大等问题，设计一种辣椒切片机。通过理论分析与参数计算确定辣椒切片机的关键部件结构和工作参数，运用性能试验，选取影响辣椒切片机工作性能的切割圆盘转速、输送带线速度和切割圆盘高度为试验因素，以切片完整度为试验指标，进行二次旋转正交组合试验，建立试验指标与影响因素回归模型，确定辣椒切片机最优作业参数组合为切割圆盘转速118 r/min，输送带线速度0.5 m/s，切割圆盘高度10 mm。通过试验验证，在该最优参数组合下，切片完整度为97.85%，与模型预测结果基本一致，相较人工切片效率提高344%，可满足新疆地区辣椒切片作业要求。     

基于机器视觉的双圆盘式棉花打顶装置设计与试验

为降低人工打顶的劳动强度，减少化学打顶的环境污染，改善“一刀切”式打顶机构的过打顶情况，通过分析手工打顶过程，设计了一种双圆盘式打顶机构，并基于机器视觉，设计打顶装置单行样机，实现棉花打顶的全程自动化控制。该装置主要由打顶机构、视觉检测机构、运动机构和棉花顶尖识别及控制系统组成。基于棉田调研、结构计算和预试验，确定了打顶装置的整体结构和关键部件尺寸。结合视觉识别研究基础与实际应用，选用YOLO v3算法搭建棉花顶尖识别及控制系统，实现棉花顶尖的识别定位，完成打顶机构的运动控制。以打顶期棉花为研究对象，进行棉花顶尖识别试验、打顶机构性能试验和田间试验，结果表明：棉花顶尖识别试验平均识别率为93%;打顶机构性能试验平均打顶率为94.67%;田间试验平均识别率为85.33%,平均打顶率为78.22%。研究结果可为棉花精准化与智能化打顶的研究提供参考。     

考虑温度系数的盘式制动器热力耦合分析

以合作企业提供的某款盘式制动器为研究对象,将制动盘材料的温度系数考虑在内,并加入了连续制动工况,在有限元分析软件ABAQUS中进行热力耦合分析,得到制动盘的温度场及应力场结果。在合作企业的LINK3900制动惯量试验台上进行试验,对比结果后验证了该应用的准确性。     

施肥对草坪质量及环境的影响

针对目前草坪施肥研究中存在的问题,综述了草坪营养的特点,以及国内外施肥对草坪质量、病虫害发生及对环境的影响,并且提出了今后在草坪施肥研究中应注意的问题。     

不同浓度萘乙酸对草莓穴盘扦插育苗的影响

in order to study the effects of different concentrations of NAA on Strawberry plug cutting seedling, 100, 200, 300, 400, 500mg / L-15 concentration gradients were set to dip the cuttings. The results showed that 200 mg / L-1 NAA was beneficial to improve the cutting survival rate of strawberry seedlings, promote the growth of roots, stems and leaves, and achieved ideal results.