大豆在回转带上的运动分析

目前，广泛使用的精选装置主要是利用摩擦特性的螺旋精选机、回转带式精选机。其中，回转带式精选机精选质量较高，对虫伤破嘴豆、虫眼豆的分选率能达到99％。依据大豆的摩擦特性和带式分选的基本工作原理，分析了大豆与回转带问的斜碰撞问题；考虑大豆沿带宽方向的运动，建立了大豆在回转带面上运动轨迹方程，为完善带式大豆精选机提供依据。     

人体受冲击后向后翻倒的动力学仿真

将人体简化为关于矢状面对称的三刚体力学模型,肌肉、韧带和肌腱等生理组织的作用简化为作用在关节上的力矩,采用Kane方法建立动力学方程;对人体向后翻倒的过程进行计算机模拟,运用自适应格式的四阶Runge-Kutta方法计算数值解。结果表明:小腿角速度越大,倒地经历的时间越短,受到的地面冲量越大;大腿角速度越大,倒地经历的时间越长,受到的地面冲量越小。利用倒地时地面对人体的冲量可进一步分析骨盆在地面冲击力作用下的应力分布,对骨盆损伤的预防和诊断治疗起指导作用。     

Long-term heathland restoration on former grassland: The results of a 17-year experiment

European lowland heaths have declined by up to 80% due to land use change and lack of management. There has been considerable research into the restoration of this threatened habitat. However, long-term outcomes of restoration are poorly understood, especially in situations where past agricultural land use imposes severe constraints on community re-assembly. In 1989 a large-scale experiment was established to examine the effectiveness of five treatments to restore heathland on formerly productive grassland: (i) natural regeneration; (ii) herbicide application to facilitate regeneration; (iii) cultivation and application of seed-rich heathland vegetation; (iv) soil removal and incorporation of heathland topsoil; and (v) heathland translocation. After 17 years the pH of the unamended agricultural soil remained significantly higher than that of the adjacent heathland. All treatments showed different trajectories of vegetation change in the long-term. Natural colonisation by heathland species was slow due to seed limitation, resulting in formation of an acid grassland community. Heathland community assembly was not facilitated by destruction of the initial grassland with herbicide. Incorporation of topsoil had an intermediate effect on pH reduction. This may explain the subsequent failure of the plant community to assemble in the anticipated proportions, and the dominance of leguminous scrub species (Ulex spp.). Turf translocation was effective in reducing pH to the required range and restoring the heathland community in the long-term. However, this technique should only be considered as a means of ‘rescue’ when habitat destruction is otherwise unavoidable. The only practical and sustainable means of increasing heathland extent on former farmland is the application of seed-bearing vegetation cut as part of routine management. However, this technique needs refining in order to establish the full range of characteristic heathland species.     

成本法和权益法在企业投资中的应用

作者详细论述成本法和权益法在企业投资中该如何应用,阐明了投资者与被投资者之间的关系;并利用成本法和权益法的条件及如何变换使用两法,为投资企业和被投资企业在资产运作过程中提供了法律依据。     

小河水电站溢洪道体型优化试验研

小河水电站溢洪道试验泄流能力大于设计泄流能力，整体布置方案优化后泄流能力满足设计要求，并大大减小了工程量。针对溢流堰闸墩后产生的水冠以及出口消能段存在的问题，通过模型试验进行体型优化，取得了较为理想的成果。① 中墩由原来4.0m改成3.0m厚并在其后部以流线型尾墩相连接，基本消除了水冠，大大降低了冲击波高，泄槽水流稳定。② 经过窄缝式挑坎和斜切挑坎试验方案比较，斜切坎能够很好地适应溢洪道轴线与下游河道流态衔接，同时达到了消能和改善下游河道流态的目的。     

基于多元振荡黏菌算法的田路分割模型参数优化方法

田路分割是农机轨迹语义分割模型的重要任务之一,其目的是将轨迹自动分割为田间作业轨迹和道路行驶轨迹。该文选用基于方向分布的田路分割模型（Field-Road Trajectory Segmentation Based On Direction Distribution,BDFRTS）,田路分割模型的参数是影响其分割准确性及精度的关键因素,传统的参数选择方法效率较低且难以获得较好的方案,限制了模型的分割性能。因此,该文尝试从参数优化的角度研究模型的性能提升,提出的方法主要包括两个方面,首先建立了一种基于元启发式算法（Metaheuristic Algorithms,MA）的田路分割模型参数优化解决方案;其次,在黏菌算法（Slime Mould Algorithm,SMA）的基础上提出了一种改进的多元振荡黏菌算法（Multiplex Oscillation Slime Mould Algorithm,MOSMA）求解参数优化方案以更好地提高模型的分割性能。MOSMA分别提出一种动态引导策略与多元振荡策略强化了黏菌的振荡收缩反应及细胞质的流动过程,进而增强了算法的优化能力。为验证所提参数优化方法的有效性,将博创联动提供的中国农机在2021年9月底-10月中下旬进行水稻收割的作业轨迹作为数据集开展试验。试验结果表明,该文所提方法有效地提升了田路分割模型的准确性和性能。MOSMA-BDFRTS分割模型在10组高密度轨迹中的平均准确率相比网格搜索田路分割模型,粒子群田路分割模型分别提高了25和28个百分点;在10组低密度轨迹中分割的平均准确率分别提高了17和14个百分点。该研究可为田路分割技术提供合理的性能优化方案,也为农业机械运动轨迹分割技术的效率研究提供参考依据。     

基于激光点云的三维虚拟果园构建方法

针对果园管理数字化程度低、构建方法较为单一等问题,本研究提出了一种基于激光点云的三维虚拟果园构建方法。首先采用手持式三维点云采集设备（3D-BOX）结合即时定位与地图构建-激光测距与测绘（Simultaneous Localization and Mapping-Lidar Odometry and Mapping,SLAM-LOAM）算法获取果园点云数据集;然后通过统计滤波算法完成点云数据离群点与噪声点的去除,并结合布料模拟算法（Cloth Simulation Filtering,CSF）与DBSCAN（Density-Based Spatial Clustering of Applications with Noise）聚类算法,实现地面去除与果树聚类分割,进而使用VoxelGrid滤波器降采样;最后利用Unity3D引擎,构建虚拟果园漫游场景,将作业机械的实时GPS（Global Positioning System）数据从WGS-84坐标系转换为高斯投影平面坐标系,并通过LineRenderer显示实时轨迹,实现作业机械运动轨迹控制与作业轨迹的可视化展示。为验证虚拟果园构建方法的有效性,在海棠果园与芒果园开展果园构建方法测试。结果表明,所提出的点云数据处理方法对海棠果树与芒果树聚类分割的准确率分别达到了95.3%与98.2%;通过与实际芒果园的果树行距、株距对比,虚拟芒果园的平均行间误差约为3.5%,平均株间误差约为6.6%。并且将Unity3D构建出的虚拟果园与实际果园相比,该方法能够有效复现果园三维实际情况,得到了较好的可视化效果,为果园的数字化建模与管理提供了一种技术方案。     

Migration of invasive Spodoptera frugiperda(Lepidoptera: Noctuidae) across the Bohai Sea in northern China

The fall armyworm(FAW), Spodoptera frugiperda(J. E. Smith), is an important agricultural pest with a strong migratory ability. While the species is native to the Americas, it has recently invaded China, ravaging crops in many provinces(autonomous regions, municipalities). Its long-distance migration, which is critical to understand for pest management programs, has been well studied in its native region. In other regions however, the moth's migration patterns have not yet been characterized. Here, the migratory behavior of FAW populations in China was studied on an isolated island located in the center of the Bohai Strait from spring to autumn 2019, the year in which FAW first reached this region, by using searchlight trapping, stable carbon isotopes and trajectory simulation. The main results were summarized as follows:(i) The number of FAW moths caught by searchlight trapping provided direct evidence that the species migrated across the Bohai Sea.(ii) Species identification was confirmed by both morphology and molecular methods, and only the "corn-strain" that preferentially infests maize and sorghum was found in the collections.(iii) Stable carbon isotope measurements showed that up to 95.07% of captured moths displayed the C4 isotope signature, thus providing additional evidence that this species is a migrant as there are no major C4 plants at the trapping site.(iv) Backward trajectory analysis indicated that the pest now threatens to expand its range into the agriculturally important region of Northeast China, and thus authorities in this region should be vigilant to the threat posed by this species. Together, these findings add to our knowledge concerning the occurrence of FAW in northern China, and will help us to develop sustainable and effective monitoring, forecasting, and pest management strategies.     

水稻钵苗“D形”静轨迹移栽机构逆向设计与分析

通过对夹取式水稻钵苗移栽作业农艺要求的分析,得出具有"D形"静轨迹的取苗爪更便于从秧箱中夹取水稻钵苗进行移栽。为了实现"D形"静轨迹,采用封闭节曲线拟合技术,通过给定型值点确定机构作业要求的运动轨迹,建立机构逆运动学模型,求解出非圆齿轮非匀速传动比函数,从而设计出非圆齿轮节曲线。计算实例验证了该逆向设计方法的可行性,通过该方法可方便获得更为复杂要求的运动规律,实现轨迹的再现和取苗段姿态的控制,可为移栽机的设计提供一种新方法。     

广西东北部稻区白背飞虱早期迁入虫源分析

 【目的】研究监测广西东北部稻区白背飞虱早期迁入的峰期,分析其虫源,为白背飞虱的早期预警和有效防治提供依据。【方法】2007—2010年在广西兴安县设置一盏佳多自动虫情测报灯,分析灯诱数据确定迁入高峰期,并运用Hysplit_4软件对其迁入高峰期进行轨迹分析确定虫源地。【结果】广西兴安县白背飞虱一般在5月中旬至6月下旬大量迁入,2007年和2010年白背飞虱早期迁入量远远大于2008和2009年,4年来的最大迁入峰期随着时间推移。轨迹分析显示,虫源地主要位于越南北部、海南、广西南部和广东西南部稻区。【结论】西南低空急流为白背飞虱的大规模北迁提供了运载气流,降雨使得白背飞虱在本地大量降落。