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.

Determination of Carbon and Nitrogen Isotope Fractions in Tartaric Acid, Oxalic Acid, Glucose and Fructose—National Center of High Technologies of Georgia

Tartaric acid, oxalic acid, glucose, and fructose are highly important compounds. A comprehensive study of these substances is fascinating from a scientific perspective. They are key components found in wine, vegetables, and fruits. Understanding the isotopic compositions in organic compounds is crucial for comprehending various biochemical processes and the nature of substances present in different natural products. Tartaric acid, oxalic acid, glucose, and fructose are widely distributed compounds, including in vegetables and fruits. Tartaric acid plays a significant role in determining the quality and taste properties of wine, while oxalic acid is also prevalent but holds great interest for further research, especially in terms of carbon isotopic composition. We can unveil the mechanisms of processes that were previously impossible to study. Glucose and fructose are the most common monosaccharides in the hexose group, and both are found in fruits, with sweeter fruits containing higher amounts of these substances. In addition to fruits, wheat, barley, rye, onions, garlic, lentils, peppers, dried fruits, beans, broccoli, cabbage, tomatoes, and other foods are also rich sources of fructose and glucose. To determine the mass fraction of the carbon-13 isotope in these compounds, it is important to study their changes during natural synthesis. These compounds can be modified with a carbon center. According to the existing isotopic analysis method, these compounds are converted into carbon oxide or dioxide [1]. At this point, the average carbon content in the given compound is determined, but information about isotope-modified centers is lost. Dilution may occur through the transfer of other carbon-containing organic compounds in the sample or by dilution with natural carbon or carbon dioxide during the transfer process. This article discusses the possibility of carbon-13 isotope propagation directly in these compounds, both completely modified and modified with individual carbon centers. The literature provides information on determining carbon-13 substance in organic compounds, both with a general approach and for individual compounds [2] [3].

Extraction of Laser Stripe Center Line Based on Genetic Algorithm and NURBS Interpolation

To improve the measurement accuracy of structured laser for inner surface dimensions of a deep hole, a new method to extract the laser stripe center line is proposed. An improved adaptive genetic algorithm that can converge rapidly and search the global optimum is used to determine the threshold for the laser stripe segmentation. And then NURBS interpolation which has a good local control capability is adopted to extract the laser stripe center line. Experiments show that the extracted laser stripe center line is stable and the diameter of the deep hole can be measured accurately.

Comparison of visual effects of FS-LASIK for myopia centered on the coaxially sighted corneal light reflex or the line of sight

AIM：To compare visual quality after femtosecond laser in situ keratomileusis（FS-LASIK）,between the coaxially sighted corneal light reflex（CSCLR） group and conventional ablation line of sight（LOS） group.METHODS：In total,243 eyes（122 patients） were treated with centration on the CSCLR（visual axis） and 238 eyes（119 patients） treated with centration on the pupil center（LOS）.Postoperative outcomes [uncorrected visual acuity（UCVA）,best spectacle-corrected visual acuity（BSCVA）],safety index,efficacy index,refractive outcome,ablation center distance from the visual axis,corneal high-order aberrations,subjective discomfort glare and shadowing incidence rate,and contrast sensitivity at 1,3,and 6mo were measured and compared.RESULTS：The mean age was 27.77±7.1y in the CSCLR group and 26.03±7.70 y in the LOS group.Preoperatively,the manifest refraction spherical equivalent（MRSE） was-6.68±2.60 D in the CSCLR group and-6.65±2.68 D in the LOS group.The postoperative UCVA,BSCVA,MRSE（-0.03±0.263 D in the CSCLR group,-0.05±0.265 D in the LOS group）,efficacy index（1.04,1.03）,and safety index（1.09,1.08） were not significantly different between the groups（all P〉0.05）.In total,3% lost one line and more of BSCVA in the CSCLR group,as 9% in the LOS group postoperatively（P〈0.05）.The ablation center deviation was 0.20±0.15 mm from the visual axis（Pentacam system default setting;range,0-0.75 mm） in the CSCLR group,and 0.43±0.22 mm（range,0-1.32 mm） in the LOS group（P〈0.0001）.Statistically significant greater augmentationof total corneal higher-order aberrations（0.15±0.10 μm and 0.20±0.12 μm respectively,P=0.03） and vertical and horizontal coma（P〈0.0001） were noted in the LOS group.Subjective discomfort glare and shadowing incidence rates were 8.59% and 17.5% in the CSCLR and LOS groups,respectively（P〈0.05）.The 1-month postoperative contrast sensitivity visual acuity in the CSCLR group was significantly higher than that in the LOS group on contrast（100%,25%,10%） with a dark background,but there was no significant difference between the groups at 3 or 6m.CONCLUSION：Myopic LASIK centered on the CSCLR achieves significantly lower induction of loss of BSCVA,corneal high-order aberrations,and lower risk of subjective discomfort glare and shadowing,and lower decline in early contrast sensitivity by comparison with centration on the LOS,giving advantages in visual quality postoperatively.

A Study on Comprehensive Modeling for Errors in on-line Measuring System of Machining Center

Based on the theory of multi-body system (MBS), bine’s and huston’s methods are applied to an on-line measuring system of machining center in this paper. Through the study on modeling technique, the comprehensive model for errors calculation in an on-line measuring System of machining center have been built for the first time. Using this model, the errors can be compensated by soft.ware and the measuring accuracy can be enhanced without any more inveSt. This model can be used in all kinds of machining center.

m-degree Center-connecting Line of Finite Points Set and Its Properties

In this paper, we first give the concept of m-degree center-connecting line in n-dimensional Euclidean space Enand investigate its several properties, then we obtain the length of m-degree center-connecting line formula in finite points set. As its application,we extend the Leibniz formula and length of medians formula in n-dimensional simplex to polytope.

Congestion Control Using In-Network Telemetry for Lossless Datacenters

In the Ethernet lossless Data Center Networks (DCNs) deployedwith Priority-based Flow Control (PFC), the head-of-line blocking problemis still difficult to prevent due to PFC triggering under burst trafficscenarios even with the existing congestion control solutions. To addressthe head-of-line blocking problem of PFC, we propose a new congestioncontrol mechanism. The key point of Congestion Control Using In-NetworkTelemetry for Lossless Datacenters (ICC) is to use In-Network Telemetry(INT) technology to obtain comprehensive congestion information, which isthen fed back to the sender to adjust the sending rate timely and accurately.It is possible to control congestion in time, converge to the target rate quickly,and maintain a near-zero queue length at the switch when using ICC. Weconducted Network Simulator-3 (NS-3) simulation experiments to test theICC’s performance. When compared to Congestion Control for Large-ScaleRDMA Deployments (DCQCN), TIMELY: RTT-based Congestion Controlfor the Datacenter (TIMELY), and Re-architecting Congestion Managementin Lossless Ethernet (PCN), ICC effectively reduces PFC pause messages andFlow Completion Time (FCT) by 47%, 56%, 34%, and 15.3×, 14.8×, and11.2×, respectively.

炮孔间距对偏心不耦合装药贯通裂纹扩展的影响

为研究光面爆破中偏心不耦合装药炮孔间距对贯通裂纹扩展的影响,利用同心不耦合装药的孔壁压力计算公式并结合应力波叠加原理,推导偏心不耦合装药的炮孔间距计算方法。基于求得的炮孔间距范围,计算3种岩石介质在不同炮孔间距条件下贯通裂纹的扩展位置,并选择砂岩材料进行数值模拟。结果表明:偏心不耦合装药爆破中,贯通裂纹主要集中于偏心侧;抗拉强度大的岩石,贯通裂纹偏离炮孔连心线的程度也较大。砂岩的炮孔间距为60 cm时,贯通裂纹扩展方向与炮孔连心线重合,连心线下方出现裂纹比较集中的贯通区域;炮孔间距的增大导致贯通裂纹远离炮孔连心线,从而造成欠挖。偏心不耦合装药爆破后,偏心侧岩石的损伤明显大于非偏心侧。

一种基于中线拓扑关系的巷道节点自适应平滑建模方法

地下空间中的三维巷道结构复杂,模型数据庞大,为解决巷道交叉口等特殊位置的精细化表达问题,本研究提出一种基于中线拓扑关系的巷道节点自适应平滑建模方法。该方法根据巷道中心线数据,自适应判别根结点下各子结点间的拓扑关系以区分各类型巷道,并设计一种半拱形曲面构建相应的模型组件,通过组件拼接的方式,实现精细化平滑建模。最后,通过对某一段巷道数据进行验证,建立了一个由三通、四通等各类交叉口平滑相连的完整巷道模型,为地下空间中复杂巷道的精准建模提供了有效的解决途径。

钢铁物流中心平面布局研究

钢铁物流中心将物流的各个环节连接在一起,科学合理地布局钢铁物流中心,对于促进物流中心内各项物流活动高效运作、降低物流成本、提升物流服务质量具有重要意义。结合钢铁物流的特点,研究了钢铁物流中心的功能分区和作业流程,提出适合钢铁物流中心平面布局的原则。根据铁路装卸线是否进入仓库,以及库内桥吊与铁路装卸线的相对关系不同,研究了铁路布置在库外和库内、桥吊垂直和平行铁路布置等4种平面布局方案,并给出了不同布局方案的适用场景。最后结合长沙北货场钢铁物流中心实例,对钢铁物流中心平面布局进行说明,对钢铁物流中心的规划和设计具有一定的参考意义。

顺势而为——三星堆博物馆新馆电气设计

三星堆博物馆新馆电气设计以对博物馆展陈最小干预,平衡建筑功能和其他专业需求,兼顾电气装置能源效率为原则,在分析项目前期调研情况和用电需求基础上,从电气机房选址、供配电系统设计、展陈配合、防雷接地系统等方面介绍三星堆博物馆新馆如何根据园区现状、建筑布局、电气系统特点,进行顺势而为的电气设计。

基于3D激光雷达的鸡舍通道中心线检测方法

针对笼养鸡舍环境下光照强度弱、作业通道内狭小导致机器人巡检时通道中心线检测困难的问题,该研究利用3D激光雷达对鸡舍通道中心线进行获取。首先通过机器人搭载的3D激光雷达对鸡舍作业通道信息进行采集,利用直通滤波、地面点滤波、体素滤波、统计滤波和平面投影对获取的3D激光雷达点云数据进行预处理,获取XOY平面上的点云数据。通过改变K-means聚类初始点选择方式和聚类函数对预处理后的点云数据进行数据分类。利用改进RANSAC算法对分类后的数据进行处理,提取通道中心线。试验结果表明该研究提出的改进K-means聚类算法平均耗时6.98 ms,相较于传统的K-means聚类算法平均耗时减少了29.40 ms,准确率提高了82.41%。该研究提出的改进RANSAC算法中心线提取准确率为93.66%、平均误差角为0.89°、平均耗时为3.97 ms,比LSM算法得到的平均绝对误差角高0.14°,平均耗时减少6.15 ms。表明该研究提出的鸡舍通道中心线检测方法基本满足笼养鸡舍环境实时自主导航的需求,为巡检机器人在鸡舍作业通道内进行激光雷达导航提供了技术支撑。

基于双三次插值和高斯拟合的光条中心亚像素提取方法

针对结构光三维测量的高精度要求,提出一种基于双三次插值和高斯拟合的激光线条亚像素提取方法。该方法首先对光条图像进行感兴趣区域提取、高斯滤波等前处理,其次用形态学方法细化激光线条得到初始中心点,然后使用五点拟合法得到光条法线方向,在光条法线方向上取亚像素的拟合点,利用双三次插值得到亚像素坐标的像素值,最后进行高斯拟合,到光条亚像素中心。实验结果表明,算法平均精度值为0.389147像素,消耗时间为0.056 2 s,具有较高的提取精度和稳定性。

一种基于低温共烧陶瓷技术的一分二功率分配器设计方法

从小型化的要求出发,提出一种一分二等分功率分配器设计方法。以Wilkinson功率分配器结构为基础,将传统功率分配器中的直线型传输线改为螺旋线型传输线。采用低温共烧陶瓷(LTCC)技术进行小型化功率分配器设计,建模时利用立体叠层结构对功率分配器内部的传输线进行布局,内部不同金属层之间使用垂直通孔连接,使得该功率分配器尺寸与传统平面结构功率分配器相比大幅减小。在HFSS软件中完成三维模型建立与电磁仿真,并对设计完成的功率分配器进行加工测试,最终得到该功率分配器回波损耗优于19 dB,插入损耗优于3.5 dB,中心频率2.8 GHz处隔离度优于35 dB,具有较好的隔离度,满足一分二等分功率分配器的性能要求,并且LTCC功率分配器尺寸仅3.18 mm×1.58 mm×0.911 mm。

基于P-中心模型的城市轨道交通线网应急救援站选址研究

[目的]随着城市轨道交通线网的扩大,其系统风险变得更为复杂且不可控。为提高城市轨道交通系统的应急救援能力,需对线网内应急救援站的选址问题展开研究。[方法]将地铁覆盖区域按照城市道路环线进行分区限速,得到任意路径的速度矩阵,结合距离矩阵进行转换后得到时间矩阵。在此基础上,计算任意站点间基于时间的最短路径。考虑时间、救援关系、成本3个方面的约束条件,建立了以系统最大救援时间最小化为目标的P-中心选址模型。以武汉市城市轨道交通线网应急救援站选址为案例,应用该模型,并采用自适应遗传算法在MATLAB软件中进行编程求解,得出该线网应急救援站选址的最优方案。[结果及结论]与相似研究相比,该选址方案投入更少但效益更大,充分证明了所提的P-中心模型具有先进性。

可变重心线路巡检机器人摆振分析及抑制

针对野外输电线巡检机器人(power transmission line inspection robot,PTLIR)受自然风影响出现的机身摆动问题,提出一种在机器人的可变重心箱体中加装摆式动力吸振器(dynamic vibration absorber,DVA)的摆振抑制策略。描述了输电线系统与巡检机器人加装摆式动力吸振器的结构特点。基于Davenport风速谱与输电线系统的特点建立了风扰动模型。分析了机器人行走对输电线的影响,建立了简化后风扰动影响下机器人摆动的动力学模型,仿真了抑振前机器人在风扰动影响下的风振响应;基于拉格朗日方程建立了加装动力吸振器优化后的巡检机器人动力学模型,并完成了吸振器的参数设计。通过仿真不同风速下机器人的风振响应,验证所提出的振动抑制策略的有效性。基于改进结构下的巡检机器人样机,开展了室内风扰动试验。结果表明,所提出的吸振器抑振策略可在一定程度上抑制机器人的机身摆动,提高工作稳定性。该研究过程对其他摆式结构设备的振动抑制具有一定的参考价值。

基于参数化建模思想的四心圆公路隧道洞形优化

合理的四心圆公路隧道断面形式有助于改善衬砌结构的受力状态,减少复合式衬砌的开裂病害,提高隧道结构的耐久性。该文通过Ansys软件APDL参数化编程平台,基于“曲率连续”的设计思想,构建了拱脚区局部洞形几何尺寸参数化建模方程,建立了锚杆加固区等效力学参数计算方法及数值模拟模型,揭示了四心圆公路隧道拱脚区域局部洞形参数设计对衬砌结构内力的影响规律,结合实际工程研究显示:隧道拱脚弧与中墙弧的半径和长度对于隧道复合式衬砌结构内力的影响较明显,增大拱脚弧半径对于抑制衬砌结构内塑性区发展的效果最为明显;为了减小衬砌结构的开裂风险,提出采用衬砌拉应力为控制目标进行局部形状优化思想,通过中墙弧圆心角θ_(2)、拱脚弧圆心角θ_(3)及中墙弧半径R_(2)对衬砌结构内力极值的敏感性及影响规律分析为皮家岭隧道洞形优化提供了理论依据。

基于二阶混联灵敏度矩阵的ECT图像重建

电容层析成像技术求解图像重建问题属于非线性问题。在灵敏度矩阵的推导过程中,通常只保留灵敏度系数的线性部分,但是被忽略的非线性部分同样包含重要的成像信息。为了提高图像重建精度,基于二阶灵敏度系数的数学定义,结合模糊C-均值聚类算法和电场中心线理论,建立了二阶混联灵敏度矩阵,并将矩阵引入到Landweber算法中,提出了二阶Landweber算法;最后,进行仿真和静态实验,并与传统的Tikhonov算法和一阶Landweber算法进行对比,结果表明,二阶混联灵敏度矩阵可以提高图像重建精度。

基于线结构光的零件三维尺寸测量系统

针对原有接触式三维测量技术测量时间长、效率低、对零件有损伤等问题,提出一种基于线结构光的零件三维尺寸测量系统。建立光平面数学模型,采用基于平面靶标的自由移动标定法标定光平面,利用基于Hessian矩阵的Steger方法对线结构光中心提取,通过坐标变换得到零件的三维尺寸。在Visual Studio软件中的Winform窗体应用设计三维测量系统的软件交互界面,搭建实验测量平台进行多个零件的测量实验。实验结果表明,对不同零件三维尺寸测量相误差均小于4%,提出的测量系统及方法具有较高的精度和稳定性,能够满足工程应用。

基于线激光的穴盘格三维重建与参数提取

现代农业嫁接过程中穴盘的参数主要依靠人工输入,针对现代农业自动化嫁接过程中取苗操作时穴盘的参数获取问题,设计了一种基于线结构光三维扫描终端;该扫描终端使用HSV(Hue,Saturation,Value)阈值处理、连通域提取、基于边缘和灰度融合的亚像素中心线提取等步骤提取激光线条中心线;提出了一种穴盘格外壁线激光三维扫描和点云数据处理的方法。首先从点云数据中提取出中央穴盘格外壁和穴盘上边沿;其次,获取取苗操作时所需要的穴盘的高度、穴盘格下底部直线边长、穴盘格顶上开口直线边长、穴盘格下底部曲线边长、穴盘格上开口曲线边长、穴盘壁曲面在不同高度下的三维建模。实验结果表明,该方法提取出的参数平均误差为0.68 mm。