液体中光击穿所激发声场的理论研究

以液体中光击穿所激发声场为研究对象,在等离子体椭球模型的基础上,为方便理论计算,简化等离子体椭球模型,提出了等离子体椭圆盘模型,对光击穿所激发声场进行了理论研究.得到了等离子体椭圆盘辐射声场的声压规律,并利用椭圆坐标变换,依据马修函数特性和模态的正交性,求得了等离子体椭圆盘振动位移的解析表达式.     

固-液结构圆柱声子晶体中弹性波的模式和带隙

利用一维固-液结构圆柱声子晶体中弹性波横向受限的条件,推导弹性波在一维固-液结构圆柱声子晶体中各个模式满足的关系式,研究各个模式弹性波的特征.并用色散函数计算各模式弹性波的带隙随模式量子数和圆柱半径的变化规律.得出一维固-液结构圆柱声子晶体的带隙由模式量子数和圆柱半径确定.     

A novel design using meshed-planar fan-electromagnetic bandgap (MP-FEBG) structure for ultra-wideband (UWB) antenna

A concept to combine the plane fan antenna with the meshed-planar electromagnetic bandgap (MP-EBG) structure is proposed; and then, based on the theory, a novel ultra-wideband (UWB) antenna with double-deck meshed-planar fan-electromagnetic bandgap (MP-FEBG) is designed. The structure of the sector is beneficial to the increase of the antenna bandwidth. The double layer structure can greatly reduce the size of the antenna, and the aperture structure can easily adjust antenna's performance. The antenna is compact in size, suitable for UWB applications. An antenna model was established on the substrate of FR4 and at least 79.1% dimension of the antenna was reduced by the traditional UWB antenna in the related documents. The simulation results show that the antenna can achieve a wide bandwidth from 3.20 to 15.78 GHz with return loss less than −10 dB and exhibit stable antenna gain. Furthermore, the measurement result is in better consistence with the simulation result.     

基于数字式MEMS传感器的声阵列成像系统设计*

常规驻极体传声器阵列成像系统存在数据采集系统复杂、体积大的问题,因而阵列传感器数量一般不超过60个,成像质量较差。为此,本文以数字式MEMS声传感器基础设计了260个传感器的声阵列,数据采集系统由FPGA控制,并嵌入到前端阵列中,后端是在另一个FPGA控制下的1个DSP芯片和2个PC104模块组成的集成系统,其中高速DSP芯片完成阵列信号处理以实现声成像功能。该系统能够实现对普通车间环境下机械设备噪声、气体泄漏噪声的现场成像测试,形成动态声像图。测试表明,该系统抗干扰能力强、声像分辨率高、成像速度快,实用效果良好。     

Superb thermal stability purple-blue phosphor through synergistic effect of emission compensation and nonradiative transition restriction of Eu2+

Phosphors with outstanding luminescence thermal stability are desirable for high-power phosphor-converted light-emitting diode (pc-LED) lightings. High structural rigidity and large bandgap of phosphor hosts are helpful to suppress nonradiative relaxation of optical centers and realize excellent thermal stability. Unfortunately, few host materials simultaneously possess aforementioned structural features. Herein, we confirm that Sr₃(PO₄)₂ (SPO) phosphate possesses high structural rigidity (Debye temperature, Θ_D = 559 K) and large bandgap (E_g = 8.313 eV) by density functional theory calculations. As expected, Eu²⁺-doped SPO purple-blue phosphors show extraordinary thermal stability. At 150/300 °C, SPO:5%Eu²⁺ presents emission loss of only 4%/8% and a predicated ultrahigh thermal quenching temperature of 973 °C. The most strikingly discoveries here are that thermal-induced emission compensation appears within two distinct Eu²⁺ sites of SPO host. The outstanding thermal stability, on one hand, is attributed to rigid structure and large bandgap of host that inhibits nonradiative relaxation of Eu²⁺ and on the other hand, the emission self-compensation of Eu²⁺. Benefiting from synergistic effect of emission compensation and nonradiative transition restriction of Eu²⁺, as-prepared SPO:5%Eu²⁺ purple-blue phosphor not only presents superior thermal stability but also high internal quantum efficiency of 95.1% and excellent hydrolysis resistant. Some advanced applications are explored including white LED lighting and wide-color-gamut display. Our work provides in-deep insights into structure-property relationships of thermally stable phosphors.     

Changes in the physical properties of low bandgap polymer after interaction with ionic liquids

Over the past few years, polymers shown comprehensive utilization in optical devices, solar cells, sensors, and other such devices. However, the efficiency of these devices remains a problem. We have synthesized new thiophene based, lowband gap polymer, poly(2-heptadecyl-4-vinylthieno[3,4-d] [1,3] selenazole) (PHVTS) and investigated the interactions between the PHVTS and ionic liquids (ILs), in this study. We have used imidazolium- and ammonium-family ILs, and studied the interactions using various spectroscopic techniques such UV–visible, FTIR, and confocal Raman spectroscopies. Additionally, we studied surface morphology of the polymer-IL film. Spectroscopic studies show that both families of ILs can interact with the newly synthesized polymer poly(2-heptadecyl-4-vinylthieno[3,4-d] [1,3] selenazole). However, the imidazolium-family Ionic Liquid-polymer (IL-polymer) mixture films show higher conductivities than ammonium-family IL–polymer mixture films.     

声表面波技术检测糜烂性毒剂芥子气的研究

声表面波技术是这些年来得到迅猛发展的一门前沿学科,是传感器技术中引人注目的新兴分支。由于声表面波化学传感器具有体积小、成本低、灵敏度高、易于集成化、智能化、实现远距离检测等多种优点,因而在军用、民用领域显示了良好的应用前景[1-3]。芥子气是糜烂性化学毒剂中最为     

Stochastic sensitivity analysis of coupled acoustic-structural systems under non-stationary random excitations

This paper presents a new sensitivity analysis method for coupled acoustic–structural systems subjected to non-stationary random excitations. The integral of the response power spectrum density (PSD) of the coupled system is taken as the objective function. The thickness of each structural element is used as a design variable. A time-domain algorithm integrating the pseudo excitation method (PEM), direct differentiation method (DDM) and high precision direct (HPD) integration method is proposed for the sensitivity analysis of the objective function with respect to design variables. Firstly, the PEM is adopted to transform the sensitivity analysis under non-stationary random excitations into the sensitivity analysis under pseudo transient excitations. Then, the sensitivity analysis equation of the coupled system under pseudo transient excitations is derived based on the DDM. Moreover, the HPD integration method is used to efficiently solve the sensitivity analysis equation under pseudo transient excitations in a reduced-order modal space. Numerical examples are presented to demonstrate the validity of the proposed method.     

水下对转螺旋桨流致辐射噪声机理与预报方法*

水下对转螺旋桨流致辐射噪声的预报对于水下目标的特征提取和分类识别具有重要意义。由桨叶的旋转引起的湍流场是水下对转螺旋桨流致辐射噪声的源场。分述了水下对转螺旋桨湍流边界层脉动、旋转干涉效应和空化效应引发的水动力噪声机制和研究进展,比较了目前工程应用中的3种对转螺旋桨流致辐射噪声预报方法的特点。在分析对转螺旋桨流致辐射噪声数值预报难点的基础上,综述了对转螺旋桨流致辐射噪声计算方法的研究进展,指出间接数值模拟方法是工程中进行对转螺旋桨流致辐射噪声预报的有效方法。