矩形弯曲隧道中电磁波的传输特性分析

由矩形弯曲隧道中电磁波沿水平方向极化模式的各场分量出发,应用边界条件得到了在弯曲隧道中电磁波传播的衰减率公式,从而得到了弯曲隧道中电磁波传播衰减率与弯曲半径之间的关系曲线和衰减率与频率之间的变化曲线。结果表明,弯曲的存在,极大地增加了电磁波传播的衰减率。在弯曲半径不变的情况下,当频率增加超过一定值时,衰减率会随着频率的增高而变大,而变化的幅度与弯曲半径有关,半径越小,衰减率增加得越快。在曲率半径较小时,频率越高,电磁波的衰减率越大,但当曲率半径大于一定数值时,则频率越高,电磁波的衰减率越小。     

带有传送带的矩形巷道中电磁波传播特性研究

为了研究带有传送带的矩形巷道电磁波传播规律,提出一种基于电磁波传播理论和多波模理论的等效分析法,旨在降低研究电磁波传播计算的复杂性.利用计算机对有传送带的矩形巷道中电磁波传播规律进行仿真,将等效分析法方案计算出的仿真数据分别与矿井巷道中实际测量的3组数据进行对比分析.实验结果表明:等效分析法可以近似分析带有传送带的矩形...     

天线波瓣宽度对巷道中电磁波传播特性的影响

选取矩形巷道作为受限空间模型,基于镜像射线追踪法,通过仿真及实验分析验证了全向天线和不同的定向天线对受限空间内电波覆盖的影响.在巷道、矿井这类受限空间中,定向天线的第一分界点比全向天线的第一分界更远;在矩形巷道中,半功率宽度对电波覆盖效果起着至关重要的作用,同时可以通过适当增加第一零点宽度来改善电波的覆盖效果;定向天线...     

煤矿巷道壁粗糙度对电磁波传播的影响

根据多波模传输理论推导出多波模综合作用下因巷道壁粗糙度引起的电磁波衰减计算公式,并采用多波模模型仿真分析巷道壁粗糙度对电磁波衰减特性的影响。Matlab仿真结果表明,巷道壁粗糙度对电磁波衰减特性的影响随频率升高而增大,由于波导效应和巷道壁粗糙度的共同作用,煤矿井巷电波传播存在一个0.4～2GHz的低衰减频段。     

矿车对电磁波传输特性影响的测量

矿车的存在改变了煤矿巷道的截面形状和尺寸,从而影响了电磁波传输特性的传输特性。文章对煤矿巷道中矿车对电磁波的影响进行了现场测量,详细分析了测量数据。测量结果表明:电磁波的传输衰减与车厢的长度和传输的频率有关;矿车的存在使电磁波的传输衰减增大;在50~900 MHz范围内,电磁波的频率越高、衰减越小,越有利于电磁波的传输。     

矩形巷道电磁波传播混合模型分界点的研究

为了更精确地描述矩形巷道电磁波传播近场区的传播特性,运用两路径模型结合Fresnel区域理论,推导了巷道近场区第一分界点距离的公式;在分界点之前,传播损耗遵循自由空间传播特性,而在分界点之后,可用多模波导传播模型预测.通过3组实测结果来验证该模型在天线不同位置、不同载波频率下的合理性,所得结论将会加深对巷道环境中电磁波传播机制的深刻理解.     

天线位置对矩形隧道电磁波传播机制分界点的影响

为精确地描述矩形空隧道内电磁波传播特性,根据传播理论与几何知识,推导出了矩形隧道中天线安装不同位置下分界点的计算公式;并通过实验验证了天线安装在不同位置下的结果。结果表明:在典型的宽大于高的矩形隧道中,分界点距离主要受天线高度变化而变化,受横向距离影响较小。证明提出的确定隧道电磁波传播分界点的方法是可行的。     

煤矿井下爆炸性环境下电磁波热效应的安全性研究

GB/T 3836.1—2021《爆炸性环境第1部分：设备通用要求》规定爆炸性环境中射频设备的阈功率不得大于6 W,该规定限制了大功率射频设备在煤矿井下的应用,而现有针对爆炸性环境电磁安全性的相关研究缺乏完善的理论分析和实验验证。针对上述问题,推导了电磁波热效应方程,分析得出影响电磁波耦合瓦斯和煤尘混合气体产生热能的可控参数为电磁波耦合时间、电场强度和电磁波频率。以GB/T 3836.1—2021中可能堆积煤尘的电气设备表面温度最高不能超过150℃的规定为依据,采用多物理场仿真软件COMSOL对不同发射功率的电磁波耦合瓦斯和煤尘混合气体的热效应安全性进行了仿真实验,结果表明：满足温度不超过150℃的电磁波热效应安全阈发射功率为16.48 W;随着电磁波发射功率的增加,电磁波热效应安全时长（电磁波耦合瓦斯和煤尘混合气体产生的热能不会使环境温度超过150℃对应的时间段）逐渐减少,但只要在安全时长内,电磁波的发射功率不受限制。     

煤矿井下电磁干扰对通信和监控系统的影响分析

文章从电磁波在矩形巷道中的传输特性出发,分析了电磁波低于和高于截止频率的衰减特性,总结了井下各种电磁辐射干扰源产生干扰的情况。通过对井下电磁干扰实测数据的分析,得出井下电磁干扰的频段主要为500 MHz以下;当干扰源与通信和监控系统的距离为几米远时,其对系统基本不会产生影响。     

巷道障碍物对风速监测位置的影响研究

现有高精度风速传感器在井下的安装位置统一采用正常风流流动状况下的方案,未综合考虑巷道放置障碍物等导致风流异常的情况,达不到智能通风的风速精度要求,难以实现矿井的安全生产。针对上述问题,以小纪汗煤矿11218回风巷为研究对象,对井下巷道中障碍物不同位置与不同尺寸对风速的影响展开研究,结合现场实测巷道基础参数与Fluent软件构建贴合该矿特征的巷道模型,研究了距上游端口10 m处底板放置的障碍物与两帮的距离（简称间距L）及其形状大小、放置方式等因素对巷道风速监测位置的影响。(1)定量分析结果发现：各模型于断面直角处存在微小部分的合理风速区域,其面积在L=0.5 m时最大,L=1 m时次之,L=0时最小;随着间距L的增加,风速传感器最佳布设位置随x坐标（巷道走向）的增加呈均匀分布-截面直角处微量分布-空心圆角矩形分布的规律,且合理风流向两帮扩散更快;L=0时,顶板位置中垂线的合理风流分布在2.59～2.78 m处;L=0.5 m时,顶板位置中垂线的合理风流分布在2.59～2.80 m处;L=1 m时,顶板位置中垂线的合理风流分布在2.61～2.78 m处。(2)定性分析结果表明：放置障碍物巷...     

A novel adaptive high-order sliding mode control based on integral sliding mode

This paper presents an adaptive high-order sliding mode control scheme targeting for uncertain minimum phase nonlinear single-input-single-output (SISO) systems, which can be equivalently formulated as the finite-time stabilization of high-order input-output dynamics subject to the uncertainties of parameters such as a chain of integrators. The proposed controller is derived from the concept of integral sliding mode and consists of two parts, one part of which achieves the finite-time stabilization of the high-order input-output dynamics without uncertainties by solving a finite-horizon optimal control problem with a free-final-state. The other part adopts the adaptive sliding mode control technique considering the practical bounded uncertainties, by which a modified switching gain adaptation algorithm is developed so that the on-line switching gain selection can be executed and the upper bounds of the uncertainties are not requisite in advance. As a result, a high-order sliding mode is established, ensuring the sliding variables and its high-order derivatives converge to an arbitrarily small vicinity of the origin in finite time. Therefore, the proposed controller achieves fixed convergence time and further improves strong robustness against bounded uncertainties with lower chattering and the easy implementation. Simulation results are presented in detail to verify the effectiveness and feasibility of the proposed algorithm.     

矩形脉冲激励的SMA振子的瞬态响应分析

研究了矩形脉冲激励下SMA振子瞬态响应的全局特性.采用多项式形式的本构方程描述SMA弹簧的恢复力,以此建立SMA振子的动力学方程;且将矩形脉冲激励的SMA振子的瞬态响应响应分为两个阶段:第一阶段是在外力恒定时的衰减振动;第二阶段是没有外力激励的衰减振动.讨论了平衡点的数目,给出了SMA振子的在不同条件下的相平面和时间历程图.最后,采用数值解验证理论分析结果的有效性.研究结果表明,对于不同强度及宽度的矩形脉冲激励,SMA振子会收敛到不同的稳定平衡点,收敛时间较短.     

Design of a rectangular waveguide to cylindrical cavity mode launcher for TE011 mode with maximum quality‐factor

This article presents the design of a mode launcher for launching TE₀₁₁ mode in a cylindrical cavity. In the given design, TE₀₁₁ mode is excited from the top wall of the cylindrical cavity using a rectangular waveguide. This type of top wall excitation of the cavity has been used keeping in view the application of the proposed launcher in coupling analysis of a coaxial magnetron. The proposed design is verified by launching TE₀₁₁ mode in a cylindrical cavity, which is designed to operate at 9.3 GHz with the maximum quality factor. The value of quality factor obtained analytically is 31 030 and the same is verified by comparing it with simulation results obtained from CST and HFSS. Return loss and insertion loss of the mode launcher are obtained as 40.24 and 0.12 dB at 9.3 GHz, respectively. The frequency tunability of the cavity is also studied by changing the length of the cavity by making the bottom wall movable and a tuning range of 200 MHz is achieved. Performance of the top wall excitation is also compared with the conventional TE₀₁₁ mode excitation from the rectangular waveguide through the side wall of the cavity, and both are in good agreement.     

Instantaneous polarization statistics of electromagnetic waves

1 Introduction The polarization information has proven promising for improving the radar per-formance of detection, tracking and recognition. For practical radars, every resolution cell contains a number of scatterers. In the reaction between incident waves and scatter-ers, every scatterer contributes to the total reflected waves. Each scatterer is random and independent. In addition it is impossible to measure the amplitude and phase of every scatterer precisely. So the total returned waves…     

矩形隧道中UHF频段电磁波场强的分布规律

利用几何光学模型,结合试验数据,探讨了矩形巷道中UHF电磁波场强的分布规律,得出了如下结论:发射天线在隧道截面的位置对隧道中电磁波的场强分布有很大影响,当发射天线的位置处于隧道截面的中心时,快衰落收敛最快,接收到的电磁波场强最大;电磁波的场强在隧道截面上近似于余弦分布,当发射天线的位置靠近隧道壁时,电磁波场强在隧道截面的分布相对均匀。该结论可用来预测隧道环境中电磁波的有效覆盖距离,对隧道微蜂窝个人移动通信网的设计和检测也很有用。     

Geometrically non-linear free vibrations of clamped simply supported rectangular plates. Part I: the effects of large vibration amplitudes on the fundamental mode shape

The geometrically non-linear free vibrations of thin isotropic and laminated rectangular composite plates with fully clamped edges have been successfully investigated in previous series of works using a theoretical model based on Hamilton’s principle and spectral analysis. The objective of this work is the extension of the above model to the case of clamped clamped simply supported simply supported rectangular plates, denoted by CCSSSSRP, in order to determine their fundamental non-linear mode shape, and associated amplitude-dependent resonant frequencies, and flexural stress distribution. Numerical data are given for both linear and non-linear analysis, for various plate aspect ratios and vibration amplitudes. Good agreement was found with previous published results.     

Three-dimensional electromagnetic simulation of electronic circuits of general shape

A general purpose CAD tool, the IE3D electromagnetic simulator is presented in this article. The simulator is based on an integral equation, a method-of-moment formulation for a full-wave solution of three-dimensional (3D) arbitrarily shaped structures in microwave and millimeter-wave integrated circuits (MMIC), high temperature superconductor (HTS) circuits, microstrip antennas, RF printed circuit boards (PCB), and high speed digital circuit packaging. The primary solution of the simulator is the current distribution on a metallic structure in an environment of multilayered substrates on infinitely extended ground plane. The circuit parameters of the structure in either S-parameter form or RLC-SPICE equivalent circuit form is extracted from the solved current distribution. The simulator consists of an MS-Windows-based layout editor, a schematic editor, an electromagnetic simulator, and a post processor. The simulator can perform stand-alone electromagnetic simulation and optimization and mixed electromagnetic and nodal analysis. Simulation results for structures in various high frequency and high speed domains are presented and compared to measured results. © 1994 John Wiley & Sons, Inc.     

矩形截面矿井巷道三维WSN覆盖机理

无线传感器节点在矿井巷道内壁上多采用径向直线型和径向V字型部署。针对矩形截面矿井巷道的无线传感器节点如何在三维空间实现单重无缝覆盖的问题,通过分析巷道几何尺寸,推导出其节点在两种部署类型中的最小感知半径;进一步推导出其节点覆盖密度与节点感知半径、巷道高度、巷道宽度之间的函数关系,比较两种部署类型节点覆盖密度,为现实运用选择节点部署方式提供有力依据。仿真实验验证了推导结果的正确性。利用推导的结论结合矿井的几何尺寸,可直接计算出节点必须满足的最小感知半径、部署方法、部署位置和覆盖密度,从而提高节点覆盖的有效性,减少工程成本支出。     

Adaptive high-order sliding mode control based on quasi-time delay estimation for uncertain robot manipulator

This paper presents the design, and validation of a new adaptive control system based on quasi-time delay estimation (Q-TDE) augmented with new integral second-order terminal sliding mode control (ISOTSMC) for a manipulator robot with unknown dynamic uncertainty and disturbances. Contrary to the conventional TDE, the proposed Q-TDE becomes sufficient to invoke a fixed artificial time delay and utilize the past data only of the control input to approximate the unknown system''s dynamic uncertainties. The incorporating of new adaptive reaching law with ISOTSMC augmented with Q-TDE policy ensures the continuous performance tracking of the robot manipulator''s trajectories using output feedback. This combination may achieve high performance with a significant chattering reducing procedure. By utilizing the Lyapunov function theory, it can be demonstrated that the robot system is stable and all signals in closed-loop are converging in finite time. Consequently, Simulation and comparative studies with two degrees of freedom robot manipulator were carried out to validate the effectiveness of the designed control scheme.