Crossing Limit Cycles of Planar Piecewise Hamiltonian Systems with Linear Centers Separated by Two Parallel Straight Lines

In this paper, we have studied several classes of planar piecewise Hamiltonian systems with three zones separated by two parallel straight lines. Firstly, we give the maximal number of limit cycles in these classes of systems with a center in two zones and without equilibrium points in the other zone (or with a center in one zone and without equilibrium points in the other zones). In addition, we also give examples to illustrate that it can reach the maximal number.

Straight and twisted Weyl nodal line phonons in Ho2CF2 material

Based on first-principles calculations, symmetry analysis and model construction, we predict that Ho2CF2hosts both straight and twisted Weyl nodal lines in its bulk phonon spectrum. We identify that the top two phonon bands entangle with each other, forming two straight Weyl nodal lines on the K–H and K′–H′paths at the Brillouin zone(BZ) boundary,and six twisted Weyl nodal lines within the BZ. All the Weyl nodal lines along the kz direction and across the entire BZ.The symmetry analysis indicates that these Weyl nodal lines are protected by the PT symmetry and crystal symmetry. The Berry phase and drumhead-like nontrivial surface states are calculated. We also construct a tight-binding model to describe these nodal lines. Our work provides an excellent material platform for exploring the fascinating physics associated with straight and twisted Weyl nodal line phonons.

Study on Forced Straight-Line Guidance for the Final Translation Phase of Spacecraft Rendezvous

Aimed at the problem of final translation of space rendezvous for the applications such as docking,inspection and tracking,optimal straight-line guidance algorithm based on pulse/continuous low-thrust in the context of Clohessy-Wiltshire dynamics is proposed.Two modes of guidance strategy:varying-speed and fixed-speed approaching scheme for V-bar and R-bar approach by using constant/finite low-thrust propulsion respectively are studied,and the corresponding fuel-optimal conditions are obtained.Numerical simulation is conducted to verify and test the proposed algorithms.The results show that there is generally no different between the fuel consumptions by using the two different approaching modes for V-bar case.However,the conclusion for Rbar case is different that the using of continuous low-thrust cost more fuel and transfer time.

A New Method for Locating Calculation of Arbitrary Spatial Straight Line or Plane in NC Machining

In the manufacturing process, we often encounter so me location machining of space arbitrary straight lines and planes that are not on ly unparalleled but also not vertical with the machine tool spindle or the cutti ng tool. In the past, we can do the location machining through the methods of dr awing line and making level in the ordinary machine tool. In the numerical contr ol machining of the CNC machine tool and manufacturing center, however, the spac e location and angle of the arbitrary straight lines and planes must be precisel y calculated in advance. So that precisely locating can be guaranteed in machini ng. Therefore, how to work out the space location angle of the arbitrary straigh t lines and planes to be machined both conveniently and precisely, turns out to be the must-be-solved chief problem in the numerical control machining. In thi s paper, through the deeply research of this problem, a new kind of calculating formula that calculates and defines the space location angle of the arbitrary st raight lines and planes by using the methods of analytic calculating. The formul a has been applied in the practical manufacturing calculation. It is proved that the new space angle calculating methods of arbitrary straight lines and planes is convenient in calculating and precise in locating. And it provides us a n ew, brief and precise calculating method in the numerical control machining of t he numerical control machine tool and manufacturing center.

Type Synthesis of Spatial Straight Line Mechanisms with only Revolute Joints

Spatial straight line mechanisms are a class of spatial mechanisms whose end-effectors generate the trajectory with the form of exact straight lines, which have potential applications in many industrial sectors. This study aims to synthesis the spatial straight line mechanisms with only revolute joints, meaning that no prismatic joints are included. According to the generalized function sets and the law of one dimensional rotation, the type of compositions of characteristic and the corresponding conditions are derived. Furthermore, some novel symmetrical and asymmetrical spatial straight line mechanisms are synthesized through assembling specific kinematic chains under the corresponding conditions. Finally, several synthesized spatial straight line mechanisms are illustrated to show the effectiveness of the synthesis methodology.

Influence of the Fitted Straight Line for Confidence Bands Algorithm in Q-Q Plots

Confidence bands in a Normal Q-Q Plot allow us to detect non-normality of a data set rigorously, and in such a way that the conclusion does not depend on the subjectivity of the observer of the graph. In the construction of the graph, it is usual to fit a straight line to the plotted points, which serves both to check the hypothesis of normality (linear configuration of the plotted points) and to produce estimates of the parameters of the distribution. We can opt for dif-ferent types of lines. In this paper, we study the influence of five types of fitted straight lines in a Normal Q-Q Plot used for construction the confidence bands based on the exact distribution of the order statistics.

A self-organization formation configuration based assignment probability and collision detection

The formation control of multiple unmanned aerial vehicles(multi-UAVs)has always been a research hotspot.Based on the straight line trajectory,a multi-UAVs target point assignment algorithm based on the assignment probability is proposed to achieve the shortest overall formation path of multi-UAVs with low complexity and reduce the energy consumption.In order to avoid the collision between UAVs in the formation process,the concept of safety ball is introduced,and the collision detection based on continuous motion of two time slots and the lane occupation detection after motion is proposed to avoid collision between UAVs.Based on the idea of game theory,a method of UAV motion form setting based on the maximization of interests is proposed,including the maximization of self-interest and the maximization of formation interest is proposed,so that multi-UAVs can complete the formation task quickly and reasonably with the linear trajectory assigned in advance.Finally,through simulation verification,the multi-UAVs target assignment algorithm based on the assignment probability proposed in this paper can effectively reduce the total path length,and the UAV motion selection method based on the maximization interests can effectively complete the task formation.

船舶管子柔性产线控制系统设计与实现

随着先进制造技术不断提升迭代以及产品质量追溯管控要求,船舶管子制造也由传统粗放的生产模式不断向自动化生产模式演变,众多船厂逐步实现并推广,以便消除制造效率与焊接质量等方面的瓶颈。为了提高产线自动化水平,应不断优化和改进相应产线控制系统。结合现场实际调研需求,梳理管子自动化产线制造工艺,并从系统功能、数据库设计、系统集成等方面进行研究与实现,以满足管子自动化产线任务接收,对具有限定条件的柔性管加工生产线精细化管理。通过任务的合并标序,完成无序上料到有序生产的能力建设。通过全周期的监控并控制自动化产线,实现安全、有序、高效的无人化生产。

35 kV交流输电线路直线塔无人机巡检自动化控制系统设计

为解决35 k V交流输电线路直线塔巡检无人机自适应能力差,导致巡检作业易出错中断的问题,该文设计一种新型无人机巡检自动化控制系统。此系统由MPU9250九自由度惯性传感器、加速度计、磁力计,采集输电线路直线塔无人机巡检状态数据,通过积分法、三角函数关系、倾斜补偿方法,解算获取直线塔无人机巡检的姿态、速度、位置数据信息;使用基于模糊PID的自动化控制器,计算无人机巡检的姿态、速度、位置偏差与偏差率,自动调整无人机旋翼转速,控制无人机巡检状态,完成35 kV交流输电线路直线塔无人机巡检自动化控制。实验中,此系统使用下,无人机巡检状态与指定轨迹一致,俯仰角、横滚角、航向角偏差值为0°。

平尺配测微表检测坐标定位系统运动直线度

对应用平尺配测微表检测运动直线度进行研究,提出了一种新方法——截段回归法,此方法突破了平尺自身长度的局限性,弥补了其他标准器在被测对象尺寸超过其适用范围,或是直线度误差超过其测量范围时无法测量的不足。可进行更长距离、误差范围更大的直线度检测,并对方法进行了验证和不确定度评定。

Research on Distance Judgement Method from Point to Line to Generate a Line

Regarding the problem that the traditional straight-line generating has a low accuracy, we study straightline generating with the distance of point to line. We explore generating a line to approximate the ideal line and the issue is to pick out the pixel point of approximating the ideal line. The paper plays a significant scientific role in elucidating linear optimization norm and it lays a foundation for showing a straight line. The algorithm is valuable for computer graphics.

累积投票制强制执行能否保护中小股东利益?--基于断点回归的实证检验

以2008-2020年A股上市公司为样本,运用精确断点回归方法检验累积投票制强制执行对控股股东利益侵占的影响,并进一步考察股权自由现金流水平在其中发挥的调节效应。研究发现:累积投票制强制执行政策能够显著抑制控股股东利益侵占,该政策能够促使上市公司累积投票制的实施,并通过制衡机制、抵御机制及预防机制改善公司治理,保护中小股东利益。进一步研究表明,在股权自由现金流水平越高的企业,累积投票制强制执行越有效。因此,累积投票制强制执行政策具有一定的合理性,应予以坚持并进一步推行。

Sectional Dimensions Identification of Metal Profile by Image Processing

In steel plants, estimation of the production system characteristic is highly critical to adjust the system parameters for best efficiency. Although the system parameters may be tuned very well, due to the machine and human factors involved in the production line some deficiencies may occur in product. It is important to detect such problems as early as possible. Surface defects and dimensional deviations are the most important quality problems. In this study, it is aimed to develop an approach to measure the dimensions of metal profiles by obtaining images of them. This will be of use in detecting the deviations in dimensions. A platform was introduced to simulate the real-time environment and images were taken from the metal profile using 4 laser light sources. The shape of the material is generated by combining the images taken from different cameras. Real dimensions were obtained by using image processing and mathematical conversion operations on the images. The results obtained with small deviations from the real values showed that this method can be applied in a real-time production line.

THE E_3~1 TYPE OF CUBIC SYSTEMS WITH TWO INTEGRAL STRAIGHT LINES

The existence and uniqueness of limit cycle for the E 1 3 type of cubic systems with two integral straight lines has been studied in this paper. It is found that the system has no limit cycle when the two integral straight lines intersect each other; it has a unique limit cycle when the two integral straight lines are paralleled. The sufficient and necessary conditions are also given to guarantee the existence of the unique limit cycle.

Global Phase Portraits of Uniform Isochronous Centers System of Degree Six with Polynomial Commutator

This paper studies the global phase portraits of uniform isochronous centers system of degree six with polynomial commutator.Such systems have the form x=-y+xf(x,y),y=x+yf(x,y),where f(x,y)=a_(1)x+a_(2)xy+a_(3)xy^(2)+a_(4)xy^(3)+a_(5)xy^(4)=xσ(y),and any zero of 1+a_(1)y+a_(2)y^(2)+a_(3)y^(3)+a_(4)y^(4)+a_(5)y^(5),y=y is an invariant straight line.At last,all global phase portraits are drawn on the Poincare disk.

应用网上直报系统实施实习护生和带教老师的双向评价

教学双方通过双向评价，能充分发挥“教”与“学”双方的主动性，提高教学质量和水平^[1]。以往评价多采用纸质问卷调查的方法口^[1-2]，每次需要组织大量人力、印制表格、花费时间进行调查和人工统计，其结果存在偏差。我院2011年1～6月采取网上直报的方法开展实习护生和带教老师的双向评价调查，取得较好效果，现报告如下。

不完全驱动船舶航迹控制输入输出线性化设计

针对船舶航迹保持控制系统模型中存在的非线性 ,建立了不完全驱动水面船舶直线航迹控制系统的非线性数学模型 ;基于输入输出线性化技术 ,采用重定义输出变量思想 ,提出了一种状态反馈控制律。该控制律克服了转首角速度不能为零及重定义输出变量中组成元素的收敛性不能保证的局限 ,使得偏航船舶能够渐近镇定于直线参考航迹 ,并以实习船为例 ,利用MatlabSimulink工具箱进行了计算机仿真研究 ,并对所提出的控制器进行了验证。结果表明 ,所提出的控制器具有比较理想的控制效果和良好的瞬态性能。

旋流器与直线脱水筛在首钢水厂尾矿干排系统中的应用

本文简单概述了常见的几种尾矿处理方法,并针对首钢水厂铁矿尾矿库库容紧张,尾矿将无处排放,造成水厂铁矿不能正常生产这一问题进行了技术改造。首钢水厂铁矿应用由旋流器和直线脱水筛组成的陆凯尾矿干排系统与现场原有浓密机配合使用对尾矿进行浓缩脱水处理,溢流器溢流和筛下产物再采用浓密机进行二次浓缩的方法,实现了水厂铁矿的技术升级,使水厂铁矿成为全国唯一一家实现全尾干排的大型国企。结果表明:流程改造后首钢水厂的技术指标及经济效益明显提高,达到了最初确定的62%的干排率,筛上尾矿含水率在20%左右,实现尾矿干排可以直接装车运输,达到降低尾矿入库量,延长尾矿库服务年限的预期效果。

考虑架空输电线路状态的线路覆冰监测系统的研究

近年来,我国输电线路冰灾情况日益严重,能够准确监测线路覆冰情况,进而采取防冰、除冰的措施显得至关重要。目前国内已经有了些架空线路的覆冰力学模型,但各个模型对于现场线路覆冰的监测还有一定的误差。分析了现有的覆冰力学计算模型,提炼了力学模型的关键计算量,提出基于直线塔受力分析的覆冰计算模型。该模型利用架空线路状态方程计算导线温度和外力变化,导线长度、水平应力和垂直荷载的变化,从而求解出导线覆冰的重量和覆冰的等值厚度。该覆冰模型已经应用在覆冰在线监测系统里面,涵盖覆冰模块的建模以及监测系统的监视和告警功能的展示。通过实例验证,该模型能准确监测输电线路的覆冰情况,并正确做出覆冰告警。

列车车轴空间直线度检测

为了准确、快速地测量列车车轴的空间直线度,构建了列车车轴空间直线度测量系统,对所述测量系统采用的空间圆拟合、空间直线拟合、直线度测量等算法进行研究。首先,根据被测对象的特征介绍了基于空间平面与空间球相切空间圆拟合算法;然后,利用随机采样一致性(RANSAC)算法迭代出符合模型的最佳点集,在列车车轴截面空间圆拟合获取的数据基础上对列车车轴截面空间圆圆心所处数据进行分析,并利用狼群算法拟合空间直线,即通过空间截面所处位置的列车车轴截面空间圆的圆心坐标拟合列车车轴空间直线;最后,利用狼群算法对列车车轴空间直线度进行测量,并把测量数据与激光跟踪仪数据进行对比。实验结果表明:基于狼群算法的列车车轴空间直线度测量精度为0.01mm,能够满足列车车轴空间直线度测量的高精度、高稳定性及测量重复性等要求。