一种基于S波段缝隙贴片的双频涡旋波天线北大核心CSCD

随着5G等新一代通信技术的迅速发展,对信道容量和频谱利用效率的需求越来越高。以双频天线为阵元进行组阵,将同时在两个谐振频率处产生OAM波束,大大提高了频谱的利用率。本文提出一种基于S波段缝隙贴片的双频涡旋波天线。其由八个阵元以60mm为半径均匀排列,阵元为切角U型槽天线,采用同轴馈电。通过调节该双频涡旋波天线各阵元的馈电相位,实现了在2.7 GHz和3.7 GHz处同时产生七种不同模态的OAM波束。仿真结果显示：其在低频处|S11|<-10dB的回波损耗带宽为0.24 GHz(2.57～2.81 GHz),高频处为0.25 GHz(3.57～3.82 GHz)。双频带内隔离度均大于23dB。本天线可以进一步提高雷达系统的分辨率。     

A GENERAL ANALYTICAL SOLUTION FOR ELASTIC VIBRATION OF RECTANGULAR THIN PLATES

A general solution of differential equation for lateral displacement function of rectangular elastic thin plates in free vibration is established in this paper. It can be used to solve the vibration problem of rectangular plate with arbitrary boundaries. As an example. the frequency and its vibration mode of a rectangular plate with four edges free have been Solved.     

基于重线和笔画连通性的视频文字二值化方法

文字二值化是实现提取视频文字信息的重要步骤。在复杂背景下,现有二值化方法不仅难以有效抑制背景干扰,而且对文字定位精度要求过高。提出一种复杂背景下稳健的视频文字二值化方法,首先,引入了穿越线的概念,通过找到一条穿越文字行的穿越线,在笔画中植入关键点。进而,充分利用文字笔画的连通性,利用区域生长的方法,完成二值化过程。实验表明,该方法能够在复杂背景下得到较理想的文字二值化图像,不受文字颜色、字体、大小等因素的影响。     

FREE VIBRATION OF ANISOTROPIC RECTANGULAR PLATES BY GENERAL ANALYTICAL METHOD

According to the differential equation for transverse displacement function of anisotropic rectangular thin plates in free vibration, a general analytical solution is established. This general solution, composed of the composite solutions of trigonometric function and hyperbolic function, can satisfy the problem of arbitrary boundary conditions along four edges. The algebraic polynomial with double sine series solutions can also satisfy the problem of boundary conditions at four corners. Consequently, this general solution can be used to solve the vibration problem of anisotropic rectangular plates with arbitrary boundaries accurately. The integral constants can be determined by boundary conditions of four edges and four corners. Each natural frequency and vibration mode can be solved by the determinate of coefficient matrix from the homogeneous linear algebraic equations equal to zero. For example, a composite symmetric angle ply laminated plate with four edges clamped has been calculated and discussed.     

轴对称载荷作用下迭层复合材料旋转壳的分段解析法

纤维缠绕旋转壳体结构具有重量轻、强度高、易加工等优点,这样的壳体在宇航技术中应用最多,这样的壳体沿子午线的刚度是变化的,但通常是正交异性的,且壳壁很薄,因而可以用分段解析法求得近似解。即把壳体沿其旋转轴分成许多个截壳单元,对每一截壳用解析法求 ...     

大曲率圆环壳对称变形的应力公式

压力容器封头顶点开孔接管处,为了减小应力集中,常做成半径很小的圆角,如图1所示.因此应将接管处看成是包含有经向曲率半径R_1很小的圆环壳.当采用薄壳结构力学方法求得圆环壳的内力和内矩后,如仍采用薄壳的应力公式来计算最大应力,则误差将随着R_1的减小而更加增大.本文参照大曲率杆的应力计算方法建立了大曲率圆环壳对称变形的应力公式,可以较精确地计算出圆角处的局部应力.如图2所示,圆环壳子午面微段中面以及距离中面为z 沿经线的长分别为     

正交异性矩形板弯曲问题的解析解

本文对求解正交异性矩形板弯曲问题,采用先建立微分方程的一般解,然后根据边界条件确定积分常数,求解了特征方程为复数根的情形。     

ANALYSIS OF SYMMETRIC LAMINATED RECTANGULAR PLATES IN PLANE STRESS

Symmetric laminated plates used usually are anisotropic plates. Based on the fundamental equation for anisotropic rectangular plates in plane stress problem, a general analytical solution is established accurately by method of stress function. Therefore the general formula of stress and displacement in plane is given. The integral constants in general formula can be determined by boundary conditions. This general solution is composed of solutions made by trigonometric function and hyperbolic function, which can satisfy the problem of arbitrary boundary conditions along four edges, and the algebraic polynomial solutions which can satisfy the problem of boundary conditions at four corners. Consequently this general solution can be used to solve the plane stress problem with arbitrary boundary conditions. For example, a symmetric laminated square plate acted with uniform normal load, tangential load and nonuniform normal load on four edges is calculated and analyzed.     

一种全天候智能运动辅助系统的研究

本文设计了一种基于传感器和无线传输的运动辅助系统,人员佩戴的单元模块通过LoRa与上位机通信.接收上位机发出的心跳信号、采集运动和定位信息.肢体传感器通过2.4 G无线通信与相应的单元模块通信以及采集肢体运动数据.LoRa使得上位机可远程获取人员数据.单元模块和肢体传感器间采用2.4 G近距离通信,避免了各人员间数据干扰.