芯片级平面环形微腔的品质因数

平面环形微腔作为光学微腔的新型腔体,在保持高品质因数的同时其加工更适合批量生产和易于与其他部件的集成,有着广泛的应用前景。文章讨论并模拟了各因素对平面环形微腔品质因数的影响,在此基础上讨论了高品质因数平面环形微腔的设计和加工。最后给出中北大学微纳中心设计加工的平面环形微腔实例。     

PPLN谐振倍频外腔输出模场的模拟研究

为了探究PPLN外部谐振倍频腔的输出模式,从菲涅尔-基尔霍夫衍射积分公式出发,采用快速傅里叶变换法(FFT)和Fox-Li迭代法数值模拟高斯反射率圆形平凹倍频腔输出基模的场强分布、相位分布和光束质量M2因子,同时与圆形双凹倍频腔做了比较.计算结果表明,两类倍频谐振腔输出塞模均为高斯分布,腔长变化对两类倍频腔输出光束质量...     

环形腔中非线性周期结构介质的双稳态和光限

研究了环腔中的非线性周期结构介质的光学双稳态和光限现象，建立了输入光强与输出光强关系的表达式。理论上给出了临界入射光强低达１０＾７Ｗ／ｃｍ＾２的光学双的条件和非常有效的限光作用的条件。     

测量介质材料复介电常数的准光腔法

针对介质材料,介绍了在毫米波段和亚毫米波段能够准确测量其复介电常数的准光学谐振腔法。准光学谐振腔具有高Q值、使用简便、样品放置容易等许多优点,能够有效地完成介质材料电介质参数精密测量的任务。这种谐振腔为半球型并由一个平面镜和一个凹面铜镜组成,采用固定腔长法或固定频率法进行测量。另外,还介绍了准光学谐振腔的测试系统和最新的研究成果及改进方法,例如测量多层薄膜及在更高频段的测量方法。     

高Q平面环形微腔的制备以及测试

采用MEMS工艺制备平面微盘腔,再通过二氧化碳激光熔融其表面形成为环状结构,通过三维形貌微系统分析仪、原子力显微镜分别测试了其外部尺寸和表面粗糙度,实验结果表明,锥形光纤近场耦合测得微腔品质因素为4.8×105,耦合效率在95%以上,因此激光回流微的方式在得到了新的结构的同时保证了光腔的性能。     

真空腔泄漏对振动筒压力传感器长期稳定性的影响分析

针对高精度绝压振动筒压力传感器的测量压力原理,提出传感器对真空度的要求。介绍了真空腔的设计方法和真空度的测试方法。从漏率的角度分析了真空腔泄漏对传感器长期稳定性和测量准确度的影响,最终给出传感器真空腔设计依据和传感器存储使用要求。     

自适应激光谐振腔系统的稳定性分析

用多变量频域稳定性判据，分析了自适应激光谐振腔系统的稳定性，针对千瓦级ＣＯ２激光非稳腔和五通道弱关联自适应光学系统的计算机模拟结果表明，多变量频域法研究自适应光学动力学系统的稳定性是有效的。     

基于视觉的环形激光陀螺自动调腔系统

针对激光陀螺调腔,设计了一种基于视觉的自动调腔系统.采用基于统计的图像分析方法,对激光陀螺光学谐振腔中的光阑和光束进行定位.根据几何光学,分析了谐振腔中反射镜位置失调与光束偏移之间的关系,并设计了基于图像的闭环位置控制律,对反射镜的位置进行调整.实验表明,该系统能够完成对光阑和光束的自动识别,能够较好地实现激光陀螺的调腔.     

不确定动力学系统的稳定性分析方法

本文应用矩阵范数及奇异值分解的理论,研究不确定动力学系统的稳定性分析方法.文中给出了一个稳定性判据及一个计算实例.     

多商品市场供需均衡的稳定性分析

应用需求弹性矩阵与供应弹性矩阵的概念,将单商品市场供需均衡的稳定性分析推广到了多商品市场的情形。     

Inverse problem of thermoelasticity for the isotropic medium containing a cavity in the case of triaxial tension with constant temperature on the surface

We consider the inverse problem of thermoelasticity for an isotropic medium containing a cavity of unknown shape and subjected to the action of mechanical and thermal loads. Nonlinear equations are deduced for the geometric parameters of an ellipsoidal equistressed cavity. Similar relations for mechanical loads obtained by the other authors follow from the constructed equations as special cases. The numerical analysis is performed and the relationship between the values of the loads and the parameters of the cavity is investigated. The stresses on the equistressed surface of the cavity are found and the influence of temperature on the relationship between the parameters of loads and the geometric characteristics of the equistressed cavity is analyzed. __________ Translated from Problemy Prochnosti, No. 1, pp. 121–131, January–February, 2007.     

Global 2D stability analysis of the cross lid-driven cavity flow with a streamfunction-vorticity approach

We have recently analyzed the global two-dimensional (2D) stability of the staggered lid-driven cavity (LDC) flow with a higher order compact (HOC) approach. In the analysis, critical parameters are determined for both the parallel and anti-parallel motion of the lids and a detailed analysis has been carried out on either side of the critical values.

In this article, we carry out an investigation of flow stabilities inside a two-sided cross lid-driven cavity with a pair of opposite lids moving in both parallel and anti-parallel directions. On discretization, the governing 2D Navier–Stokes (N–S) equations describing the steady flow and flow perturbations results in a generalized eigenvalue problem which is solved for determining the critical parameters on four different grids. Elaborate computation is performed for a wide range of Reynolds numbers (Re) on either side of the critical values in the range 200 ? Re ? 10000. For flows below the critical Reynolds number Re_c, our numerical results are compared with established steady-state results and excellent agreement is obtained in all the cases. For Reynolds numbers above Re_c, phase plane and spectral density analysis confirmed the existence of periodic, quasi-periodic, and stable flow patterns.     

The assessment of human exposure to low frequency and high frequency electromagnetic fields using the boundary element analysis

Analysis of the human body exposed to low frequency and high frequency electromagnetic fields is presented in this work. The formulation of the problem is based on a simplified thick wire model of the human body. The current distribution induced in the body is determined by solving the Pocklington integral equation for a straight thick wire via the Galerkin–Bubnov boundary element method. Once the axial current along the equivalent antenna of the body is obtained, one may calculate the induced current density, electric field, specific absorption rate, and the total absorbed power in the human body. Several realistic exposure examples are given.     

频率对声致羟自由基形成的影响

本文用声化学效率的概念，报道了频率对声致羟自由基形成的影响，在氮气或空气环境中，高频超声辐照所致ＯＨ的化学产率比低频超声辐照时高。     

基于大涡模拟和Lighthill声类比的孔腔流动发声特性研究

孔腔流动发声是气动声学研究领域重要的课题,基于大涡模拟和Lighthill声类比方法,探讨了气体在孔腔流动的流激噪声的发声特性。模拟结果表明,孔腔边界层出口剪切涡、边棱处涡街和腔体内反馈涡的运动诱导了孔腔发声,具有明显的偶极子特性,在高频段腔体内激发了声学驻波模态。通过模拟与实验对比分析了不同流量下噪声量级以及频谱分布规律,研究结果表明:24 kHz以下的声频谱会表现出波峰小范围迁移;24 kHz以上频率对应的声压级随流量增大而增大;腔体长度和特征频率近似满足Strouher公式,即声频特征频率随腔体长度的增大而减小。上述研究结果为下一步设计在线监测安全阀泄漏的报警超声波发声器提供了理论依据。     

高压富水充填溶腔释能降压技术

高压富水充填溶腔具有水量大、水压高、规模范围大、充填介质复杂的特征,工程施工风险极高,采用传统的注浆法进行处理,受地层的不均一性、材料选择、技术水平的影响,难免会出现注浆盲区,施工中一旦注浆盲区被高压水击穿,将会发生大规模突水突泥,造成灾害。针对宜万铁路所遇到的高压富水充填溶腔,通过科技攻关,提出采取释能降压新技术进行处治。经现场实践,安全、经济、可靠,并取得了成功。释能降压技术是针对高压富水充填溶腔采取有计划、有目的的精确爆破揭示,从而释放溶腔所存储的能量,降低施工及运营过程中水土压力对隧道形成影响,之后,通过配套处治措施完成溶腔治理。     

双级永磁同步变频离心机余热采暖应用

本项目利用循环化工基地的工艺循环水输送至分布首站,换出一次水,通过一次管网输送到用户侧,由双级永磁同步变频离心式热泵机组对区域住宅实现供热,从而实现了对工业余热的有效利用.     

爆炸冲击荷载下扩腔体积和能耗随抵抗线的变化规律研究

针对柱状药包爆炸冲击荷载下炮孔周边岩体介质扩腔体积和能耗占比问题,采用爆破破岩和断裂力学理论,结合爆炸具有瞬时、高温、高压等极端态特性,构建了仅以单轴动态抗压为主要依据的过度粉碎区岩石破碎能耗的简易计算公式,并开展了模型试验研究。该研究结果表明:随着最小抵抗线由120 mm增加到200 mm,扩腔半径由炮孔半径的2.6倍增加到4.6倍,扩腔体积增加了3.56倍,呈现明显的指数增长趋势;能耗由524 J增加到1870 J,能耗占比由5.93%上升到21.13%,与现有的研究成果基本一致,验证了计算公式的可行性。该研究结果能够为光面爆破、预裂爆破等控制爆破技术的设计和施工提供理论依据。     

Study on the stability and microstructural properties of barium sulfate nanoparticles produced by nanomilling

Barium sulfate nanoparticles were produced by nanomilling in stirred media mill using sodium salt of polyacrylic acid (PAA-Na) as a dispersant. The particles sizes of the ground product obtained in the grinding mill were determined by dynamic light scattering (DLS), Brunauer–Emmet–Teller (BET) nitrogen gas adsorption method, and transmission electron microscopy (TEM). The mean particle size calculated with various methods yielded different values due to the different characterization techniques. The stability of BaSO₄ nanoparticles produced was analyzed by zeta potential measurement and Turbiscan. The stability of barium sulfate nanoparticles was high in presence of dispersant PAA-Na and higher pH values. Further, the changes in microstructural properties, caused by wet grinding and adsorption of PAA-Na on BaSO₄ nanoparticles, were studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The surface activation and amorphization of BaSO₄ nanoparticles were observed due to increased stresses exerted on the particles during wet grinding.     

基于高频柔性并联激振台柔性转动关节的加工误差分析

 柔性关节因其结构上的优越性已逐步取代传统刚性关节被运用到高频激振领域中.加工误差是一类不可避免的误差,其对柔性铰链工作性能产生了一定的影响.在分析柔性铰链宽度制造误差等5类结构参数误差的基础上,运用Paros J刚度计算公式和Smith S T的误差分析方法建立了加工误差模型,并运用有限元方法模拟了柔性铰链在实际工作条件下的受力变形状况,发现不同的加工误差对柔性关节的刚度影响程度不同,其中厚度误差的影响最大,验证了加工误差模型的准确性.