Channel Bed Slope Effect on the Height of Gravity Waves Produced by a Sudden Downstream Discharge Stoppage

We derive a simple analytical correction of a well-known standard formulation of the gravity wave height produced in a prismatic channel due to a sudden discharge stoppage at the downstream end of the channel. The proposed analytical correction considers the vertical growth of the wave and, as a result, takes into account the effect of the channel bed slope on the wave height. This simple correction is useful to be considered in preliminary designs of relatively long channels subject to unsteady flow conditions.     

Influence of wavelength-to-excavation span ratio on ground motion around deep underground excavations

Accurate estimation of ground motion around excavations is important for dynamic rock support design in deep civil tunnels and underground mines. Among the influencing factors, the wavelength-to-excavation span ratio (λ/D) has a large effect on ground motion. Using an advanced wave propagation simulation tool, we performed two series numerical experiments to study the effect of the λ/D ratio on ground motion near excavation boundaries. The modeling results reveal that the wave field becomes more complex as the λ/D ratio decreases. The absolute PPV (Peak Particle Velocity) values around an excavation are closely related to the intensity of the seismic source but the relative PPV value depends on the λ/D ratio. Amplification factors, defined as the PPV in the excavation model to the PPV in the background model without any excavation, are calculated for each case. The amplification factor around the excavation increases significantly as the λ/D ratio decreases. When the λ/D ratio is greater than 30, the wave amplitudes are less affected by the excavation and a seismic wave loading can be considered as “quasi-static.” When the λ/D ratio is less than 20, significant wave interaction occurs and the wave loading needs to be considered as “dynamic.” The numerical results provide additional insights into the ground motion behavior around excavations under both “quasi-static” and “dynamic” loading conditions.     

Wave interactions and wave-structure scattering in nonlinear patterned waveguides

The nonlinear interactions between discrete optical solitons that propagate in different regimes of diffraction, and the nonlinear scattering of dispersive waves by local optical potentials, were studied experimentally. It is well known in electromagnetism that when linear coherent waves meet they interfere without interactions. Linear waves also scatter through local optical structures without exchanging any power with guided and anti-guided modes of these structures. When a focusing Kerr nonlinearity is present, linearly inhibited phenomena, which break these rules, are shown to exist. Our studies were performed with Silica glass and semiconductor AlGaAs nonlinear planar modulated waveguides, excited by ultra-short pulses in the near infrared spectral regime.     

用解波动方程和曲折光线法分析平面光波导

解波动方程和曲折光线法是分析平面光波导的基本方法．若将二者有效地结合，则分析问题会十分简便．本文首先用解波动方程的方法求出非对称波导的模式方程，然后结合曲折光线法得出的模式方程导出对称波导的模式方程．最后用图解法求出模式方程的数值解．     

流体饱和多孔隙介质中弹性波运动方程的解—伪谱法

本文提出了一种解流体饱和多孔隙介质中波传播方程的数值方法，并详细推导了该方法的计算公式．用此公式对单界面模型中地震波的传播进行了模拟，结果与Ｂｉｏｔ理论预测的相符．     

氢分子的零级波函数

本文从氢的复函原子轨道出发,构造了氢分子的两类零级波函数集。它是好的波函数,具有明确的角动量沿键轴方向分量的测定值,其几率密度与方位角φ无关,在D_∞h或C_∞v群中易于分类。     

PLC在广电中波天线开关自动切换系统中的应用

文章介绍了基于PLC控制的广电中波天线开关自动切换系统的控制原理，系统的整体设计与实际应用结果分析。提供了主要的硬件原理图和软件框图。该系统功能先进、实用，具有良好的应用前景。     

基于电流控制的混合式步进电动机微步驱动技术研究

对电流控制型的二相混合式步进电动微步驱动技术进行了深入研究.探讨了检测波形的非完整性和给定信号波形的设定.在分析快续流和慢续流控制方式的基础上,提出了一种混合续流的新控制方法.仿真结果证明其控制效果明显.还讨论了小电流误差的问题及对策.     

基于单片机、EDA技术的波形发生器的设计

本设计是基于单片机和EDA相结合的技术,用于产生各种频率的正弦波、方波和三角波,其幅值0～5V可调,幅值步进为0.039V,频率步进为1Hz。该波形发生器以单片机(MCS8031)为中心控制单元,由键盘输入模块、数码管显示模块、D/A波形发生模块、幅值调整模块组成。采用DDFS技术,先将要求的波形数据存储于EEPROM中,这样可以保证掉电以后波形数据不丢失。为了达到所要求的高速度,采用FPGA(ALTEAR公司的EPF10K10LC84-4,晶振频率可达40MHz)来实现波形的发生,通过DDFS技术(直接数字频率合成技术)、VHDL语言和单片机汇编语言编程技术的完美结合实现了对正弦波、方波和三角波三种波形的频率、幅值的设置和发生。     

爆炸冲击波对桥梁毁伤的实时模拟

文章介绍了一种模拟爆炸冲击波对桥梁毁伤过程的方法。该方法用3DMAX建立桥梁的表面模型并用VRML格式保存，然后使用Delaunay三角剖分算法对表面模型进行三角剖分，并构造出一种由三菱柱组成的三维实体模型来模拟桥梁的断裂及碎片的产生和运动，文中采用了简单的冲击波－球形冲击波，结合随机函数求解各碎片的初始速度，计算出每帧内各碎片的位置，最后生成桥梁毁伤的动画效果，该方法能逼真地表现出桥梁受冲击波毁的效果，并能满足虚拟战场的实时性要求。