基于多MEMS梁的微波功率检测芯片

为了优化MEMS微波功率检测芯片的微波性能,提高其制备的可靠性,建立了悬臂梁结构在线式MEMS微波功率检测芯片的S参数模型,研究了悬臂梁的数目对微波功率检测芯片微波性能的影响。对多梁结构微波功率检测芯片微波性能进行理论推导和仿真,制备了单梁、双梁结构MEMS微波功率检测芯片样品,并进行了测试。结果表明,在8~12 GHz的频率范围内,单梁结构的微波功率检测芯片回波损耗小于-27 dB,双梁结构的微波功率检测芯片回波损耗小于-18.5 dB,单梁、双梁微波功率检测芯片传输特性变化趋势与理论值基本一致,验证了S参数模型的正确性。

山区S形曲线桥梁施工关键技术研究

针对山区公路桥梁施工存在的机械材料运输困难、施工组织难度大等问题,本文旨在提出一套适用于山区S形曲线桥梁施工的预制T形组合梁制作、运输和安装方法,以提高施工效率和质量。首先分析山区桥梁施工的特点,对S形曲线桥梁中T形组合梁的预制流程及施工控制要点开展技术创新和优化。首先提出了改进的T梁预制方法,基于钢筋定位架优化了钢筋布设精度和效率,并通过智能张拉设备、自动喷淋系统等智能化手段,有效提高了预制梁的成品品质。其次,针对安装效率的挑战,研究提出了一种左右幅整体架设的预制梁安装方案,基于此对T形组合梁的安装流程进行了优化。通过在某大桥项目中的实际应用与验证,结果表明,本技术方案可提高T梁预制和架设精度,有效控制S形桥梁纵向及横向的线形。本研究为山区S形曲线桥梁施工提供了一套T形组合梁从生产到安装的全过程标准化技术方案,为类似项目提供了宝贵的技术参考与实践指导。

Alignment of beam position monitors in cryomodule of CADS injector Ⅱ

Significant temperature difference(300-77 K or even 4 K) can cause large deformations and displacements of the beam position monitors(BPMs),which affect BPMs measurement resolution or even cause their malfunction in cryogenic situations.In this paper,to check the offset from the mechanical to electrical center in low temperature(77 K),Fourier's law and finite element method are used to simulate cryo-deformation.Laser tracker and micro-alignment telescope are employed in combined BPM calibration,installation and monitoring.The calibration error is<0.02 mm,and the installation and monitoring precision are 0.06 mm and 0.01 mm,respectively.The monitored cryo-deformation agrees well with the simulation results.These indicate that the combined alignment can improve performance of the BPM system.All these guaranteed the success of running the 9.55 MeV@2.14 mA cw protons.

Effect of rotary inertia on stability of axially accelerating viscoelastic Rayleigh beams

The dynamic stability of axially moving viscoelastic Rayleigh beams is pre- sented. The governing equation and simple support boundary condition are derived with the extended Hamilton＇s principle. The viscoelastic material of the beams is described as the Kelvin constitutive relationship involving the total time derivative. The axial tension is considered to vary longitudinally. The natural frequencies and solvability condition are obtained in the multi-scale process. It is of interest to investigate the summation parametric resonance and principal parametric resonance by using the Routh-Hurwitz criterion to obtain the stability condition. Numerical examples show the effects of viscos- ity coefficients, mean speed, beam stiffness, and rotary inertia factor on the summation parametric resonance and principle parametric resonance. The differential quadrature method （DQM） is used to validate the value of the stability boundary in the principle parametric resonance for the first two modes.

Approximate analytical solutions and experimental analysis for transient response of constrained damping cantilever beam

Vibration mode of the constrained damping cantilever is built up according to the mode superposition of the elastic cantilever beam. The control equation of the constrained damping cantilever beam is then derived using Lagrange＇s equation. Dynamic response of the constrained damping cantilever beam is obtained according to the principle of virtual work, when the concentrated force is suddenly unloaded. Frequencies and transient response of a series of constrained damping cantilever beams are calculated and tested. Influence of parameters of the damping layer on the response time is analyzed. Analyitcal and experimental approaches are used for verification. The results show that the method is reliable.

Vibration suppression of magnetostrictive laminated beams resting on viscoelastic foundation

The vibration suppression analysis of a simply-supported laminated composite beam with magnetostrictive layers resting on visco-Pasternak’s foundation is presented.The constant gain distributed controller of the velocity feedback is utilized for the purpose of vibration damping.The formulation of displacement field is proposed according to Euler-Bernoulli’s classical beam theory(ECBT),Timoshenko’s first-order beam theory(TFBT),Reddy’s third-order shear deformation beam theory,and the simple sinusoidal shear deformation beam theory.Hamilton’s principle is utilized to give the equations of motion and then to describe the vibration of the current beam.Based on Navier’s approach,the solution of the dynamic system is obtained.The effects of the material properties,the modes,the thickness ratios,the lamination schemes,the magnitudes of the feedback coefficient,the position of magnetostrictive layers at the structure,and the foundation modules are extensively studied and discussed.

Solving Nonlinear Differential Equation Governing on the Rigid Beams on Viscoelastic Foundation by AGM

In the present paper a vibrational differential equation governing on a rigid beam on viscoelastic foundation has been investigated. The nonlinear differential equation governing on this vibrating system is solved by a simple and innovative approach, which has been called Akbari-Ganji＇s method （AGM）. AGM is a very suitable computational process and is usable for solving various nonlinear differential equations. Moreover, using AGM which solving a set of algebraic equations, complicated nonlinear equations can easily be solved without any mathematical operations. Also, the damping ratio and energy lost per cycle for three cycles have been investigated. Furthermore, comparisons have been made between the obtained results by numerical method （Runk45） and AGM. Results showed the high accuracy of AGM. The results also showed that by increasing the amount of initial amplitude of vibration （A）, the value of damping ratio will be increased, and the energy lost per cycle decreases by increasing the number of cycle. It is concluded that AGM is a reliable and precise approach for solving differential equations. On the other hand, it is better to say that AGM is able to solve linear and nonlinear differential equations directly in most of the situations. This means that the final solution can be obtained without any dimensionless procedure Therefore, AGM can be considered as a significant progress in nonlinear sciences.

Practical realization of dual S arm antenna for beam steering applications

A dual S shaped micro strip antenna with a realistic feed is proposed for generation of tilted beam radiation pattern pertaining for beam steering applications. To achieve this, four feeding points are located at a distance of 5.6 mm from the antenna centre. These feeding points when excited one by one generate four tilted beams in four different space quadrants, thus yielding a beam steerable antenna, Importantly, since the proposed antenna is symmetrical in the structure, all the four tilted beams have the same radiation pattern characteristics. A further enhancement of the antenna bandwidth is also achieved using 100-μn capacitive coupling between the feed and the antenna strip.

Seismic interferometry and estimation of the Green's function using Gaussian beams

This study investigates seismic interferometry in which the Green＇s function is estimated between two receiv- ers by cross-correlation and integration over sources. For smoothly varying source strengths, the dominant contributions of the correlation integral come from the stationary phase directions in the forward and backward directions from the alignment of the two receivers. Gaussian beams can be used to evaluate the correlation integral and concentrate the amplitudes in a vicinity of the stationary phase regions instead of completely relying on phase interference. Several numerical examples are shown to illustrate how this process works. The use of Gaussian beams for the evaluation of the correlation integral results in stable estimates, and also provides physical insight into the estimation of the Green＇s function based on seismic interferometry.

Second-order temporal interference of two independent light beams at an asymmetrical beam splitter

The second-order temporal interference of classical and nonclassical light at an asymmetrical beam splitter is discussed based on two-photon interference in Feynman＇s path integral theory. The visibility of the second-order interference pattern is determined by the properties of the superposed light beams, the ratio between the intensities of these two light beams, and the reflectivity of the asymmetrical beam splitter. Some requirements about the asymmetrical beam splitter have to be satisfied in order to ensure that the visibility of the second-order interference pattern of nonclassical light beams exceeds the classical limit. The visibility of the second-order interference pattern of photons emitted by two independent single-photon sources is independent of the ratio between the intensities. These conclusions are important for the researches and applications in quantum optics and quantum information when an asymmetrical beam splitter is employed.

Analysis of wave propagation in a functionally graded nanobeam resting on visco-Pasternak＇s foundation

Wave propagation analysis for a functionally graded nanobeam with rectangular cross-section resting on visco-Pasternak＇s foundation is studied in this paper. Timoshenko＇s beam model and nonlocal elasticity theory are employed for formulation of the problem. The equations of motion are derived using Hamilton＇s principals by calculating kinetic energy, strain energy and work due to viscoelastic foundation. The effects of various parameters such as wavenumber, non-homogeneous index, nonlocal parameter and three parameters of foundation are performed on the phase velocity of the nanobeam. The obtained results indicate that some parameters such as non-homogeneous index, nonlocal parameter and wavenumber have significant effect on the response of the system.

Modification of the Properties of Cu_x S Thin Films by Low Energy Ion Beam Implantation

Cu x S thin films are implanted by low energy N + ion beam. The influences of the energy and dose of N + ion implantation on Cu x S films are investigated. The results show that the ratio of copper to sulfur is increased to some extent, the constituents of the film are turned to rich copper phase from rich sulfurous phase after ion beam irradiation. X-ray diffraction spectrum and optical transmission spectra of sample have confirmed the results.

Research Modification of Liquid Hydrocarbons Irradiated by a Nanosecond e-Beam

Air or inert atmosphere irradiation of liquid normal alkanes C5-C8 and benzene by electron beam was carried out. Oxidation （in the air） or isomerization （in the inert gases） of liquid normal alkanes under electron beam was shown. Action of electron beam on benzene molecules in the air or in the inert atmosphere leads to biphenyl, terphenyl and polymers. Irradiation by the bunch of electrons of mixture hexane with 10% benzene reduced to firm fractions （fullerene＇s similar structures） in a deposit.

Wavelet Beam Propagation Method for Study the Integrated Optical Waveguide

A new numerical technique based on the wavelet derivative operator is presented as an alternative to BPM to study the integrated optical waveguide. The wavelet derivative operator is used instead of FFT/IFFT or finite difference to calculate the derivatives of the transverse variable in the Helmholtz equation. Results of numerically simulating the injected field at z =0 are exhibited with Gaussian distribution in transverse direction propagating through the two dimensional waveguides (with linear and/or nonlinear refractive index) , which are similar to those in the related publications. Consequently it is efficient and needs not absorbing boundary by introducing the interpolation operator during calculating the wavelet derivative operator. The iterative process needs fewer steps to be stable. Also, when the light wave meets the changes of mediums, the wavelet derivative operator has the adaptive property to adjust those changes at the boundaries.

Dependence of Structural and Optoelectrical Properties on the Composition of Electron Beam Evaporated Zn_xCd_(1-x)S Thin Films

Thin films of ZnxCd1-xS have been prepared by electron beam evaporation of a mixture of ZnS & CdS powders. The films are deposited onto sodalime glass slides under similar conditions.The composition of the films is varied from CdS to ZnS (x=0 to 1). The films show a regular change in color from toner red to orange yellow as Zn concentration increases to maximum.These films are characterized for their optical, electricaI and structural properties. The bandgap value of ZnxCd1-xS films is found to vary linearIy from 2.20 eV to 3.44 eV with change in the x value from 0 to 1. The resistivity of these films is in the range of 171.0 Ωcm to 5.5× 106Ωcm for x=0~0.6. All the samples show cubic structure after annealing in air at 250℃ for 40 min.The lattice constant ao varies from 0.5884 nm to 0.54109 nm linearly.

Experimental Measurement of the Generalized Stokes Parameters of a Radially Polarized Random Electromagnetic Beam

Utilizing the Young’s double slits and Mach-Zehnder interferometer, we proposed an experimental method to measure the generalized Stokes parameters of a radially polarized random electromagnetic beam. After the partially coherent beam propagating through the Young’s double slits, the interference fringe is obtained by the help of a Mach-Zehnder interferometer consisting of apertures, quarter-wave plates and polarizers. The electric cross-spectral density matrix is detected by the coherence degree of interference fringe and the density of each single slit. The generalized Stokes parameters can be obtained from the electric cross-spectral density matrix. This experiment measures the generalized Stokes parameters of the random electromagnetic beam successfully. The results show that the spectral degree of coherence for copolarized cases (xx and yy) is similar with that for cross-polaried cases (xy and yx) for the radially polarized random electromagnetic beam. This method will help us determine the change of the polarization and coherence of the light in propagation by detecting the change of the generalized Stokes parameters.

Bending the Foundation Beam on Elastic Base by Two Reaction Coefficient of Winkler’s Subgrade

A new method for analysis of counter beams is presented in the paper. The analysis has taken into account their stiffness EI, Winkler’s space with modulus of subgrade reaction k and equality deformities of the foundation beam with the ground. The solution is found by using the numerical analysis of the Winkler’s model, with variation of different moduli of the subgrade reaction k2 outside the force zone r, while under the force P exists the modulus of the subgrade reaction k, up to the definition of minimum bending moments. The exponential function k2(r), as the geometric position of the minimum moments is approximately assumed. From the potential energy conditions of the reciprocity of displacement and reaction, the width of the zone r and the modulus of the subgrade reaction k2 are explicitly determined, introducing in the calculation initial and calculation soil displacement wsi successively. At the end of the paper, it presented numerical example in which the influence of k and k2 values on bending moments of the counter beam is analyzed. The essential idea of this paper is to decrease the quantity of the reinforcement in the foundations, beams, i.e. to obtain a cost-efficient foundation construction.

LINEAR ACTIVE STRUCTURES AND MODES (Ⅱ) —DISCRETE SYSTEMS AND BEAMS

The basic concepts about the active structures and some attributes of the modes were presented in paper “Liner Active Structures and Modes]( I) ". The characteristics of the active discrete systems and active beams were discussed, especially, the stability of the active structures and the orthogonality of the eigenvectors. The notes about modes were portrayed by a model of a seven-storeyed building with sensors and actuators. The concept of the adjoint active structure was extended from the discrete systems to the beams that were the representations of the continuous structures. Two types of beams with different placements of the measuring and actuating systems were discussed in detail. One is the beam with the discrete sensors and actuators, and the other is the beam with distributed sensor and actuator function. The orthogonality conditions were derived with the modal shapes of the active beam and its adjoint active beam. An example shows that the variation of eigenvalues with feedback amplitude for the homo-configuration and non-homo-configuration active structures.

基于多注速调管的S波段9MeV能量可调加速管设计与研制

设计了一种S波段9 MeV驻波电子直线加速管。工作频率为2998 MHz,管长为780 mm。其使用3.1 MW多注速调管作为微波功率源,最大工作比可达到2‰,同时通过调节加速管输入功率及电子枪高压,可实现打靶电子束能量连续可调,可应用于无损检测领域,为工业探伤提供合适的能量、提高探伤效率。本文以工业领域常用的9 MeV/6 MeV能挡为例进行仿真设计及束流测试。

车辆荷载作用下钢-混凝土组合梁疲劳应力分析

【目的】随着桥梁服役期延长和车辆荷载增加等多种因素的影响,结构承载力会变得越来越弱,疲劳寿命不断降低,最终可能导致低应力疲劳破坏。因此有必要对车辆荷载下拱桥钢混组合梁的疲劳细节应力进行研究。【方法】采用数值模拟的方法,利用Midas FEA NX软件建立3个标准长度的三维实体精细有限元模型,分析钢混组合梁易损疲劳关键点的位置,并研究车辆荷载横向最不利加载位置和纵向加载下的疲劳细节应力变化规律。【结果】结果表明,组合梁次横梁与中纵梁交点处有三处疲劳关键点;靠近桥梁中线位置是车辆荷载下钢梁疲劳最不利的横向加载位置;四种不同标准的纵向车辆加载时,三个疲劳关键点均出现两次应力峰值,且最大应力幅值均低于常幅疲劳强度的极限值。【结论】研究成果可为钢-混凝土组合梁试验和相关研究提供参考。