Natural frequencies of rectangular Mindlin plates coupled with stationary fluid

The present study is concerned with the free vibration analysis of a horizontal rectangular plate, either immersed in fluid or floating on its free surface. The governing equations for a moderately thick rectangular plate are analytically derived based on the Mindlin plate theory (MPT), whereas the velocity potential function and Bernoulli’s equation are employed to obtain the fluid pressure applied on the free surface of the plate. The simplifying hypothesis that the wet and dry mode shapes are the same, is not assumed in this paper. In this work, an exact-closed form characteristics equation is used for the plate subjected to a combination of six different boundary conditions. Two opposite sides are simply supported and any of the other two edges can be free, simply supported or clamped. To demonstrate the accuracy of the present analytical solution, a comparison is made with the published experimental and numerical results in the literature, showing an excellent agreement. Then, natural frequencies of the plate are presented in tabular and graphical forms for different fluid levels, fluid densities, aspect ratios, thickness to length ratios and boundary conditions. Finally, some 3-D mode shapes of the rectangular Mindlin plates in contact with fluid are illustrated.     

Interference of vortex-induced vibration and transverse galloping for a rectangular cylinder

The phenomenon of interference between vortex-induced vibration (VIV) and galloping in the transverse degree of freedom was studied in the wind tunnel in the case of a spring-mounted slender rectangular cylinder with a side ratio of 1.5 having the short side perpendicular to the flow. The tests were carried out in a wide Scruton number range, starting from low values and increasing it in small steps by using eddy-current viscous dampers. This study helped understanding the dynamics of the interaction between the two excitation mechanisms and clearly highlighted the transition through four regimes of VIV-galloping interference. It was found that a high value of the mass-damping parameter is required to decouple the ranges of excitation of vortex-induced vibration and galloping completely, and for the quasi-steady theory to predict the galloping critical wind speed correctly. This conclusion is also relevant from the engineering point of view, as it means that structures and structural elements with ordinary mass-damping properties can exhibit sustained vibrations in flow speed ranges where no excitation is predicted by classical theories of vortex-induced vibration and galloping. Although most of the experimental tests were conducted in smooth flow at zero angle of attack, the paper also discusses the sensitivity of the results to a small variation of the mean flow incidence and to the presence of a low-intensity free-stream turbulence.     

Fluctuation strength of modulated sound radiated from rectangular plates with mixed boundary conditions

A generalized differential quadrature method is developed for solving the sound radiated from the forced vibrating rectangular plates with mixed boundary conditions in this paper. The fluctuation strength of the radiated sound, which is modulated by another sound near the plates, is studied. The effects of the modulation frequency and the modulation degree on fluctuation strength are revealed. The effects of the radiated sound frequency and the structural modal density are also studied and compared. The numerical results are presented to show the characteristics of the fluctuation strength of the modulated sound radiated from rectangular plates with mixed boundary conditions.     

变系数曲线支承矩形厚板自由振动的傅里叶分析

本文给出了变系数曲线支承的Ａｍｂａｒｓｕｍｉａｎ矩形厚板自由振动问题的级数解，将位移和剪力在板域内展成重傅里叶级数，将其导数在边界上展成单傅里叶级数，通过傅里叶变换将控制微分方程和边界条件转化成关于位移级数的系数的一组无穷线性代数方程，最终将板的自由振动问题转化为矩阵特征值问题。     

Exact Green's function for rectangular potentials and its application to quasi-bound states

In this work we calculate the exact Green's function for arbitrary rectangular potentials. Specifically we focus on Green's function for rectangular quantum wells enlarging the knowledge of exact solutions for Green's functions and also generalizing and resuming results in the literature. The exact formula has the form of a sum over paths and always can be cast into a closed analytic expression. From the poles and residues of the Green's function the bound states eigenenergies and eigenfunctions with the correct normalization constant are obtained. In order to show the versatility of the method, an application of the Green's function approach to extract information of quasi-bound states in rectangular barriers, where the standard analysis of quantum amplitudes fail, is presented.     

第三类热边界条件对激光晶体热效应的影响

以各向异性半解析热分析理论为基础,研究矩形横截面Nd∶YVO4激光晶体在有第三类热边界条件工作时,激光晶体温度场分布和晶体抽运面热形变分布.通过激光晶体工作特点分析,建立符合激光晶体工作状态的热模型.利用各向异性介质热传导方程的半解析求解方法,得出了矩形截面Nd∶YVO4晶体的温度场、端面热形变场的通解表达式.研究结果表明：当使用输出功率为15 W半导体激光器端面中心入射Nd∶YVO4晶体（晶体掺钕离子质量分数为0.5%）时,在抽运端面中心获得499.5 K最高温度和0.99 μm最大热形变量.和将第三类热边界条件近似为第二类热边界条件的通用做法相比更准确.这种方法可以应用到其它激光晶体热问题研究中,为有效解决激光系统热问题提供了理论依据.     

Computational evaluation of mass filter acceptance and transmittance influenced by developing fields: An application of the plane method to investigate prefilter efficacy for rectangular wave operated mass filters

The acceptance of quadrupole mass filters is improved when the alternating current (AC) and direct current (DC) fields are developed separately. Physically, this is achieved when a short RF only quadrupole (prefilter) is situated directly ahead of the mass filter. The acceptance gained by a system operating with a prefilter can be observed as an increase in sensitivity over conventional operation. Frequency dynamic duty cycle based rectangular waveform driven (rectangular wave) mass filters, a recent development, currently do not operate with prefilters. Little is known about the influence of duty cycle changes on the acceptance of rectangular wave mass filters. The sensitivity gain seen by conventional systems operating with prefilters indicates that the sensitivity of duty cycle based rectangular wave systems should increase comparably. The objective of this work was to determine prefilter efficacy for nonspecific rectangular wave mass filter systems. In this work, the plane method of acceptance was used to model the change to the acceptance and transmittance of sine and rectangular waveform driven mass filters under different modes of field development. Both systems indicated a fourfold increase in sensitivity when the mass filtering DC or duty cycle was delayed.     

巷道中电磁波传输特性研究

随着通信技术的发展,地面移动通信技术在不断提高,但是煤矿井下移动通信技术进展缓慢,主要是由于矿井下恶劣的通信环境以及对通信的特殊要求。为了使复杂的问题简单化,文章将矿井巷道理想化,根据理想波导理论,研究了直巷道内电磁波的传输特性和损耗特性,并且估算了TE10波在一定的巷道壁电导率情况下的损耗和传输距离,本文对巷道内无线电通信的发展有着重要的理论指导意义。     

Miniaturized microstrip bandpass filter designed using rectangular dual spiral resonator

A miniaturized microstrip bandpass filter based on a rectangular dual spiral resonator (DSR) is proposed in this paper. The rectangular DSR bandpass filter is centered at 3.65 GHz to suit for Wireless LAN (IEEE802.11y) application. The proposed filter offers transmission zero at the high side of out-of-band response. Across the bandwidth, the measured minimum insertion loss is about 1.7 dB, while the measured return loss is better than 19 dB. Measurement results are good agreement and closed to the simulated ones. The total circuit size of the miniaturized bandpass filter is about 0.145λ_g by 0.135λ_g, where λ_g is the guided wavelength at 3.65 GHz.     

矩形波导不连续性的有限元分析

本文应用Gelerkin有限元法对矩形波导H面和E面不连续性问题进行了研究,编制了一个通用的计算机程序.对矩形波导H面弯曲、E面弯曲以及T型结头进行了计算机辅助设计,理论计算与测试结果吻合很好,证明了本文方法的正确性.