直角坐标红花采摘机器人的设计与试验

针对红花采摘仍以人工采摘为主、采摘效率低下、费时费力等问题,结合红花物理生长特性及红花种植模式设计了一种直角坐标红花采摘机器人.对直角坐标采摘系统进行参数计算,确定直角坐标采摘系统X轴总长为900 mm,Y轴总长为700 mm,Z轴的行程范围为698 mm.由静力学仿真试验可知:在采摘过程中应用普通碳钢应变最小为6.5...     

Modelling the effect of crop and weed on herbicide efficacy in wheat

Recommended field application rates of herbicides have to give effective weed control in every situation and are, thus, often higher than that required for specific fields. An understanding of the interaction between crop:weed competition and herbicide dose may, in many cases, allow herbicide application rates to be reduced, important both environmentally and economically. We have developed a model of the interaction between crop:weed competition and herbicide dose, using an empirical model of the relationship between crop yield and weed biomass (related to weed density), and an empirical model of the relationship between weed biomass and herbicide dose. The combined model predicts crop yield, given herbicide dose and weed biomass at an interim assessment date. These crop yield loss predictions may be used to quantify the herbicide dose required to restrict yield loss to a given percentage. Parameters of the model were estimated and the model tested, using results from experiments, which used cultivated oats ( Avena sativa ) or oilseed rape ( Brassica napus ) as model weeds in a crop of winter wheat ( Triticum aestivum ).For the crop:weed:herbicide combinations investigated there was little increase in crop yield for herbicide dose rates above 20% of recommended field rates, in broad agreement with the model predictions. There may still be potential for further reduction below this level on economic grounds; the model could be used to estimate the `break-even' herbicide dose.     

新型方钢管混凝土柱-钢梁节点的试验与非线性有限元分析

介绍了新型方钢管混凝土柱与钢梁节点在低周反复荷载作用下的试验结果,分析了内填混凝土、加劲肋长度和梁柱相对尺寸等对节点抗震性能的影响.试验结果表明:各试件实测滞回曲线比较饱满,具有良好的耗能性能.运用ANSYS8.0对各节点试件在低周反复荷载作用下的滞回性能进行非线性模拟计算,分析内填混凝土、加劲肋长度等因素对节点受力性能的影响,结果表明:内填混凝土和加劲肋长度对节点受力性能的影响较大,有限元所得的骨架曲线与实测曲线吻合较好.     

A novel substrate integrated waveguide broadband bandpass filter

A novel broadband substrate integrated waveguide bandpass filter is presented based on the highpass characteristics of substrate integrated waveguide (SIW) and the bandstop performance of photonic band gap (PBG) structure.In order to verify it,a wideband bandpass filter with center frequency of 5.0 GHz and fractional bandwidth of 60% is designed.The electromagnetic simulation results show its good passband characteristics from 3.5 GHz to 6.5 GHz,and the maximun insertion loss is about 0.64 dB.An experimental filter prototype is fabricated with standard PCB technics and measured with the vector network analyzer.The measured results show the passband is from 3.8 GHz to 6.8 GHz,the fractional bandwidth is about 56%,and the minimal insertion loss is about 1.6 dB.The measured results are in good agreement with the simulated results.     

Design in the mandrel land and smoothing the deformation of rectangular tube drawing

With mandrel drawing process and the mechanisms of smoothing deformation have been analyzed. A method of smoothing deformation is brought forward that rectangular tube should be extruded uniformity out of die land with little amount of deformation. The dynamics model simplified and FE model of with mandrel drawing process are established based on FEM software, then simulations are performed. Three points including the center of long side, the center of short side, and the center of corner are positioned for further analysis. As for linear type and step type mandrel lands, the effective plastic strain and contact stress of three key points are evaluated. As for the plastic strain at the center of long side, a most difficult place to ensure surface quality, step type mandrel land can improve 45.5%. As for the contact stress, step type mandrel land can increase to 13MPa from 0. Drawing with step type mandrel land achieves the stress status tensile stress in one orientation and compressive stress in other two orientations, which purposes of little amount of deformation to correct thickness tolerance and improve inner and outer surface quality of rectangular tube.     

手持式GPS三参数的确定

论述了影响手持式GPS精度的因素,并探讨了如何有效提高手持式GPS精度。着重阐述了空间直角坐标系之间的转换关系,并为实现这一转换进行了实践操作,在转换过程中运用了高斯投影的反变换、大地坐标系与空间直角坐标系之间的转换等诸多理论。成功地解算出了WGS-84坐标系与西安80坐标系之间转换的三参数,并且通过实测检验得到了较高的精度。     

进水池形状对吸入涡影响试验研究

为了改善进水池附近的流态,避免吸入涡进入喇叭口,首先以不同淹没深度和不同流量对开敞式进水池进行高速摄影和PIV试验,根据测试的流态提出相应改善措施,然后对矩形进水池和矩形进水池加底部十字架2种方案进行试验,观察并对比其消涡效果.结果表明,相对于开敞式进水池的方案,矩形进水池方案可以使喇叭口处的流态得到改善,并将前者的允许最小淹没深度降低,即在同等条件下改善了旋涡的表面涡纹状态;然后对矩形进水池方案加十字架后,进一步减小了旋涡的影响,并再次降低了允许最小淹没深度,由0.90D降低到0.70D,且改善了旋涡的表面涡纹状态.研究结果对于允许最小淹没深度的改进、降低泵站进水池的工程造价方面具有参考意义.     

矩形农渠机翼形量水槽水力特性数值模拟

采用VOF方法与标准k-ε紊流模型相耦合,对矩形农渠中三种不同收缩比的机翼形量水槽进行三维数值模拟,并将渠道下游断面水深、过流流量等数值计算结果与物理模型试验结果进行对比,结果表明,二者吻合得较好,从而证明采用三维CFD数值模型对实体模型内部流场的模拟是可靠的,为今后机翼形量水槽的深入研究和优化设计提供了新的方法和依据。     

三疣梭子蟹对蟹笼网目和刚性矩形逃逸口的逃逸行为比较

为了解东海近海蟹笼逃逸口类型对三疣梭子蟹（Portunus trituberculatus）逃逸行为的影响,本研究使用红外水下摄像装备,对入笼的三疣梭子蟹在不同行为阶段对安装于侧网靠近笼底一侧的刚性矩形逃逸口（40mm高×200mm宽）和网目逃逸口（由2个位置较低的40mm×60mm和1个位置较高的60mm×60mm破目构成）的行为反应进行了观察。根据三疣梭子蟹探索、发现并接近、穿越企图和穿越逃逸口个体连续行为的4个阶段观察结果显示：相比刚性矩形逃逸口,三疣梭子蟹在网目逃逸口实验蟹笼中的探索行为持续时间更长;在笼底探索的个体能定位、发现并接近2种不同类型逃逸口,但发现并接近网目逃逸口时距离入笼的平均时间（P<0.01）和平均次数（P=0.061）均大于刚性矩形逃逸口;约85%发现并接近逃逸口的三疣梭子蟹企图穿越逃逸口,且在逃逸口类型之间没有显著差异;三疣梭子蟹在网目逃逸口前停留了更长的时间（P=0.006）,且这一时间显著影响着个体是否企图逃逸的行为。所有个体均采用侧身姿态穿越逃逸口,对于刚性矩形逃逸口,个体甲高与逃逸口高度的关系是决定个体能否成功逃逸的关键因素;对于网目逃逸口,个体优先尝试穿越较低逃逸口,并最终全部逃逸。实验结果表明网目逃逸口可以作为蟹笼渔具逃逸装置,生物可降解材料应用可成为缓解蟹笼幽灵捕捞问题的技术手段之一。     

蚁群算法在定制家具矩形零件排样中的应用

零件排样,是指在一定规格的原料板材上,按照一定规则排布若干个不同尺寸规格的零件,在满足订单配套和切割要求的前提下,达到一定的优化目标.本研究以定制家具的零件排样问题为对象,根据定制家具零件排样生产的实际情况,将零件排样问题与蚁群算法(ACA)结合,以最优化原材料利用率为目标构建批次订单排样的数学模型,搜索得到批次零件的...