Covariant Anomaly and Hawking Radiation from Kerr-Newman Black Hole in Dragging Coordinates Frame

In the light of Robinson and Wilczek's new idea,and motivated by Banerjee and Kulkarni's simplified method of using only the covariant anomaly to derive Hawking radiation from a black hole,we generally extend the work to Kerr-Newman black hole in dragging coordinates frame.It is shown that the flows introduced to cancel the anomaly at the event horizon are equal to the corresponding Hawking radiation in dragging coordinates frame,which supports and extends Robinson and Wilczek's opinion.

基于坐标时间序列的地心运动分析与预测

地心运动会影响地球参考框架原点的准确性,是地球参考框架进行非线性维持必须考虑的因素之一,因此提出对地心运动进行多尺度的建模和预测,以实现毫米级地球参考框架的建立和维持。采用网平移法计算的地心运动、全球地球物理流体中心(global geophysical fluids center,GGFC)和国际GNSS服务(international gnss service,IGS)第三次重处理(IGSR03)提供的3组地心运动数据,首先对其一致性和差异进行了分析,然后分别利用谐波模型和Diff-LSTM模型对地心运动进行了长期和短期的建模与预测,结果显示,GGFC地心运动的预测精度优于1.5 mm,而Diff-LSTM模型的地心运动预测结果在短期内优于谐波模型,当预测步长为17时,GGFC和IGSR03的地心运动预测精度均能达到甚至优于1 mm。表明地心运动的预测精度能够满足基于地球质量中心(center of mass of the total earth system,CM)的瞬时地球参考框架的建立与维持。

一种游动傅科机械编排的捷联惯性间接极区导航算法

针对指北方位、游移方位等机械编排的惯性导航系统在极区附近出现计算溢出、导航误差发散、方向基准缺失等问题,本文提出了一种基于游动傅科机械力学编排的捷联惯性间接极区导航算法。首先,推导了传统坐标系和横向坐标系下的游动傅科机械编排位置、速度和姿态转换关系,并设计了完整的捷联惯性极区导航流程。其次,在详细分析载体沿经线穿越极点时的导航解算性能基础上,提出了一种游动傅科机械编排的捷联惯性间接极区导航算法。实验结果表明,该算法能够实现传统导航与横向导航方式的平滑切换,并借助横向导航信息解决载体穿越极点时无法导航的难题。

某大跨度现浇楼盖结构中框架边梁裂缝原因分析

通过对某大跨度现浇楼盖结构中框架边梁破坏现象的观察和计算结果的分析,得出以下结论:框架边梁与楼盖次梁整体现浇时,端部存在嵌固约束作用,特别是支承多根大跨度次梁的框架边梁始终处于弯剪扭复合受力状态。框架边梁两端1/3跨度内协调扭转嵌固约束作用显著,应高度重视,不可折减或忽略,设计时应考虑抗扭作用;框架边梁中部约1/3跨度内次梁的嵌固约束作用不显著,可不计边梁的约束影响,边梁的最大扭矩变化较小,中部约1/3跨度内次梁可按照两端简支梁设计。

组态视角下产业链和创新链耦合协调多元路径研究

产业链和创新链协调发展对区域高质量发展具有重要意义。通过测算2012—2021年31个省份双链耦合协调度,采用核密度估计描述全国双链耦合协调度的变化趋势和差异;采用必要条件分析(NCA)与模糊集定性比较分析(fsQCA)相结合的方法,挖掘TOE框架下6个前因变量与双链耦合协调度提升的复杂因果关系。结果表明:全国双链耦合协调度不断提升,但省际差距不断增大;单个要素并不构成双链高耦合协调水平的必要条件,高数字产业建设在产生双链高耦合协调水平方面发挥着普遍作用;驱动双链高耦合协调水平的路径具有“殊途同归”特征,产生双链高耦合协调水平的路径分别为数字产业-教育驱动型、数字经济驱动型和数字设施-数字产业-教育均衡驱动型。

高速公路顺层边坡锚索框架梁和抗滑桩联合支护体系变形特征研究

以贵州省乌长高速公路某顺层高边坡为例,建立有限元模型,对锚索框架梁-抗滑桩支护体系的变形规律进行研究。结果表明:对各排锚索施加相同的预应力值不合理,存在锚索框架和抗滑桩顺序破坏的风险,应根据各排锚索随桩顶位移的变化规律,设置差异化的预应力值,使锚索框架和抗滑桩两种支护形式同时达到最佳支护效果;靠近桩顶位置,应设置较低的预应力值,远离桩顶位置,应设置较高的预应力值。提出基于变形协调条件下的锚索预应力值计算方法,得到的锚索预应力值与数值模拟计算结果误差在6%以内,满足设计精度要求。

省级区域CORS标准化运行维护技术研究

本文基于湖北省北斗地基增强系统运行维护实际经验和故障情况统计分析,从坐标框架维护、基准站维护和观测数据维护三方面展开讨论。首先,采取频率为每年一次的全网坐标更新,保持坐标框架的稳定;其次,针对基准站的维护,设定每个基准站的全年巡检频率为2~3次,并对电力故障及网络故障等常见故障进行预防和处理;最后,在数据维护方面,每年进行数据质量分析,确保数据利用率及多路径效应等技术指标满足要求。结果表明,本维护策略的实施,能够确保湖北省北斗地基增强系统全年可利用率保持在95%以上,全年正常运行率达到98%以上。这些经验和方法为湖北省北斗地基增强系统的稳定运行提供有力保障,也可为其它省级区域基准站网的运行维护提供参考。

Automatic Method for Synchronizing Workpiece Frames in Twin-robot Nondestructive Testing System

The workpiece frames relative to each robot base frame should be known in advance for the proper operation of twin-robot nondestructive testing system. However, when two robots are separated from the workpieces, the twin robots cannot reach the same point to complete the process of workpiece frame positioning. Thus, a new method is proposed to solve the problem of coincidence between workpiece frames. Transformation between two robot base frames is initiated by measuring the coordinate values of three non-collinear calibration points. The relationship between the workpiece frame and that of the slave robot base frame is then determined according to the known transformation of two robot base frames, as well as the relationship between the workpiece frame and that of the master robot base frame. Only one robot is required to actually measure the coordinate values of the calibration points on the workpiece. This requirement is beneficial when one of the robots cannot reach and measure the calibration points. The coordinate values of the calibration points are derived by driving the robot hand to the points and recording the values of top center point（TCP） coordinates. The translation and rotation matrices relate either the two robot base frames or the workpiece and master robot. The coordinated are solved using the measured values of the calibration points according to the Cartesian transformation principle. An optimal method is developed based on exponential mapping of Lie algebra to ensure that the rotation matrix is orthogonal. Experimental results show that this method involves fewer steps, offers significant advantages in terms of operation and time-saving. A method used to synchronize workpiece frames in twin-robot system automatically is presented.

The Explanation of the Michelson-Morley Experiment Results by Means Universal Frame of Reference

It is commonly thought that the Michelson-Morley experiment from 1887 and Kennedy-Thorndike experiment from 1932 demonstrated that the universal frame of reference (ether) does not exist and that the velocity of light in vacuum is absolutely constant. The analysis of this experiment led to the creation of the Special Theory of Relativity (STR). The article explains why Michelson-Morley and Kennedy-Thorndike experiments could not detect the universal frame of reference. In this article, a different transformation of time and position than the Lorentz transformation is derived on the basis of the geometric analysis of the Michelson-Morley and Kennedy-Thorndike experiments. The transformation is derived based on the assumption that the universal frame of reference (UFR) exists. UFR is a frame of reference in which the velocity of light is constant in every direction. In inertial frames of reference moving in the UFR, the velocity of light may be different. The article has derived the formula for relative speed and patterns for the maximum and minimum speed of light that can be measured in the inertial system. Finally, the anisotropy of the microwave background radiation has been explained by using the presented theory. According to the body kinematics model presented in this article, anisotropy of cosmic microwave background is the Doppler effect for observer moving in the UFR.

框指令FRAME在数控铣削齿块中的应用

通过对框指令操作的分析提出一种新方法,用以替代在数控镗铣床回转工作台上加工大模数齿块中,齿块中心与工作台回转中心不重合时所需进行的大量的坐标参数计算。

转动参考系中质点运动的动力学分析及数值模拟

转动参考系中质点在惯性力作用下的运动是力学教学的难点,本文分别在匀角速转动参考系、变角速转动参考系和惯性系下对该问题的动力学进行分析,得出质点的动力学微分方程;并基于欧拉法,利用Matlab软件对该问题的动力学微分方程进行了数值计算求解和模拟,直观地画出了质点的运动轨迹,基于程序数据对该问题的运动规律进行了较为深入的分析。将研究内容融入教学中,提高了教学效果,培养了学生解决实际问题的能力,对海洋科学、大气科学等相关的专业的后续专业课学习产生了积极的影响。

气囊式框架地梁边坡支护结构力学性能分析

针对地震、崩塌等自然灾害频发而导致的边坡失稳问题,提出了可快速应对抢险救灾工作的气囊式锚杆框架地梁新型结构,并阐述了该新型结构的工作机理。分析气囊框架地梁受荷时玻璃钢与气囊的受力特性,给出了气囊框架地梁承载力计算方法;结合气压传动和双层弹性地基梁理论,建立了气囊框架地梁-锚杆-土体协调变形的计算模型,给出了气囊式框架地梁在边坡支护施工阶段与工作阶段的力学效应计算方法。结果表明:①气囊式框架梁结构承载力主要由框架梁板厚、板材强度、气囊内压和高度决定,增加框架板厚、板材强度、气囊内压和高度可以提高结构承载力;②气囊式框架梁支护边坡存在施工和工作两个阶段,工作阶段位于坡脚处的框架梁剪力和弯矩出现较大的上升,设计时应作为最不利因素着重考虑;③支护设计时还应综合考虑支护效果、结构承载力和经济性给出设计方案,确保结构在实际抢险救灾中的可靠性、时效性和经济性。研究成果可在边坡快速支护中为新型结构的设计应用提供理论依据和指导。

带斜撑巨型框架-核心筒结构协同分析的哈密顿对偶体系

在连续化假定的基础上,将带斜撑巨型框架与核心筒分别等效为底端固定、上端自由的悬臂梁,等效后的悬臂梁具有弯曲刚度和剪切刚度。将楼板等效成刚性连杆,建立带斜撑巨型框架-核心筒高层建筑结构协同分析的计算模型。在哈密顿力学体系下对结构进行分析,导出哈密顿正则方程,采用精细积分法求解结构在侧向力作用下的位移与内力。用这种方法对带斜撑巨型框架-核心筒结构进行协同分析,理论推导思路清晰、过程简捷,数值计算易于编程、精度较高。采用本文方法对带斜撑巨型框架-核心筒高层建筑结构进行协同分析,可以准确把握结构的整体受力性能,在初步设计阶段对结构方案进行试算和快速分析。

钢桁腹-混凝土组合箱梁畸变效应分析

为研究钢桁腹-混凝土组合箱梁的畸变效应,根据其结构特性和力学特性,考虑共同工作区对组合箱梁腹杆纵向刚度的贡献,提出一种更适用于该类组合箱梁的畸变扇性坐标分布模式。采用新畸变中心定义符合钢桁腹-混凝土组合箱梁畸变变形特征的畸变角,应用能量变分法建立畸变控制微分方程,并给出包含Krylov函数的初参数解。结合数值算例,分析钢桁腹-混凝土组合箱梁在均布畸变荷载作用下的畸变翘曲正应力,并通过有限元软件ANSYS验证所推导理论的正确性。通过改变腹杆壁厚、俯角等关键参数,探究其对畸变内力的影响规律。结果表明:按该方法揭示的钢桁腹-混凝土组合箱梁的畸变应力分布规律与ANSYS计算结果吻合良好;横向畸变框架刚度是影响此类箱梁畸变效应的主要因素,且其对钢腹杆几何特性参数较为敏感。

大跨度钢网架分榀整体吊装+局部高空散拼施工技术

钢网架结构是大跨度空间钢结构中一种常见的结构形式。由于其具有自重轻、强度高、抗震性能好、施工周期短、节能环保等诸多优点,在工业厂房等建筑工程中得到广泛的应用。大跨度空间钢网架在安装施工过程中受杆件长度及杆件规格尺寸以及施工场地和工程造价的限制,无法采用常规钢结构一样采用大吨位起重机械进行吊装。为此,结合实际工程案例,重点阐述一种采用多个起重机械协同控制的吊装方法,在确保施工安全和工程质量的前提下,成功实现大跨度钢网架的分榀整体吊装+局部高空散拼安装。

2-D distributed pose estimation of multi-agent systems using bearing measurements

This article studies distributed pose(orientation and position)estimation of leader–follower multi-agent systems over𝜅-layer graphs in 2-D plane.Only the leaders have access to their orientations and positions,while the followers can measure the relative bearings or(angular and linear)velocities in their unknown local coordinate frames.For the orientation estimation,the local relative bearings are used to obtain the relative orientations among the agents,based on which a distributed orientation estimation algorithm is proposed for each follower to estimate its orientation.For the position estimation,the local relative bearings are used to obtain the position constraints among the agents,and a distributed position estimation algorithm is proposed for each follower to estimate its position by solving its position constraints.Both the orientation and position estimation errors converge to zero asymptotically.A simulation example is given to verify the theoretical results.

船舶肋骨线型高精度拟合方法

船舶肋骨线型拟合的精度直接影响数控肋骨冷弯机弯制的精度,传统“用单条三次曲线拟合一整根肋骨线型”的方法具有无法严格经过所有给定点、误差分析无依据和未考虑曲率半径等缺陷。为避免这些缺陷,将整根肋骨看成多个分段,每个分段是一个独立的三次曲线,且参数数量正好等于已知数数量,使参数的解静定。针对由考虑曲率半径产生的非线性优化问题,将分段函数的处理从全局坐标系转换到局部坐标系,将分段的待求解参数从4个降维至2个,便于指定参数的初始解。利用坐标变换,将局部坐标系的结果转换回全局坐标系,拟合后的肋骨线型满足:严格经过所有给定点;曲率半径以高精度逼近给定值,误差的数量级为10^(-5)。

CORS在区域GNSS控制测量中的应用分析

CORS的实时动态定位服务已广泛应用于我国经济建设的各个领域当中,产生了显著的社会经济效益。利用CORS高精度的坐标基准框架、稳定的基准站点位和完备的GNSS观测数据等资源优势,开展区域GNSS控制测量工作,可进一步发挥CORS效用,降本增效。本文通过具体项目实践,分析验证了CORS在区域GNSS控制测量中的应用效果。

A Note on Natural Coordinates and Frenet Frames

This paper discusses the relationship between natural coordinates in fluid mechanics and orthogonal curvilinear coordinates. Since orthogonal curvilinear coordinates have some excellent mathematical properties, natural coordinates can be applied more widely if they can be transformed to orthogonal curvilinear coordinates. Frenet formulas which describe the differential properties of natural coordinates were compared with the derivative formulas of orthogonal curvilinear coordinates to show that natural coordinates are not generally orthogonal curvilinear coordinates. A method was introduced to transform natural coordinormal planes of the natural coordinates about the streamlines. The transformation is true as long as the natural coordinates satisfy several equations. Vorticity decomposition in the natural coordinates is used to show that these conditional equations are satisfied only if the streamlines are perpendicular to the vortexlines on every given point in the flow field. These equations apply in both planar flows and axisymmetric flows without a circumferential velocity component, but do not apply in some 3-D flows such as Beltrami flow.

Leader-Following Entrapping Control of AUVs Using Bearing Measurements in Local Coordinate Frames

In this paper,the entrapping control problem of discrete-time AUVs with local coordinate frames is studied.To achieve entrapment in arbitrarily shaped orbits and formations,we design a bearingbased leader-following framework fully in the discrete-time domain with four parts:the orientation estimation unit,estimator unit,controller unit and parameters tuning unit.With bearing measurements and communication information,the orientation estimation unit can estimate orientations of local coordinate frames infinite time,and the estimator unit can achieve local localization.Based on estimation,the controller unit can drive each AUV to track the desired orbit or formation with an arbitrary shape.We present su±cient conditions under which stability of the overall system is proved using the theorem offinite-time stability and LaSalle's theorem for the discrete-time system.Moreover,the parameters tuning unit can calculate optimal parameters to improve overall performance.Additionally,we extend our schemes to nonholonomic AUVs with unicycle models.Finally,simulation results demonstrate the effectiveness of the proposed scheme.