用于光纤机敏材料与结构损伤估计的人工神经网络

本文以光纤机敏材料与结构中的损伤估计为目的,根据光纤阵列传感信号处理的需要,在给出人工神经网络处理原理与结构基础上,结合应用详细地阐述了适用的反向传播神经网络(BP)模型、自组织特征映射神经网络(Kohonen)模型及其变化形式(LVQ1,LVQ2,LVQ3,LVQ4及LVQ5等),同时给出了仿真实验的结果.     

利用生物发光分析技术快速检测微生物的方法学研究

阻碍三磷酸腺苷－虫萤光素酶发光体系用于微生物快速检测的主要因素之一，在于使用了不适当的非微生物ＡＴＰ清除方法和微生物ＡＴＰ提取方法。文章对非微生物ＡＴＰ的清除和微生物ＡＰＴ提取方法进行了实验研究。     

测定超导体临界特性曲线的新方法

本文描述了测定超导体临界特性曲线的持续电流方法。和文献上通常采用的四引线方法相比较,本方法具有下列优点:(1)I_c(H)曲线的物理意义明确;(2)避免了向液氦杜瓦瓶内输入大电流时技术上的困难;(3)没有烧坏样品的危险。用本方法测量了冷加工铌线的I_c(H)曲线,结果证明了以前用四引线方法所得I_c(H)特性曲线中峯的存在。     

数值求解对流扩散方程的特征有限分析方法

本文在详细分析了对流扩散过程物理特性的基础上,按对流扩散过程的物理要求应用特征方法处理对流项、以能充分描述扩散效应的有限分析方法处理扩散项,建立了一种合乎对流扩散物理要求的、无条件L_∞稳定的、数值模拟对流扩散物理现象的特征有限分析方法;并就非线性情况证明了特征有限分析方法的收敛性、给出了解的误差估计。最后的数值实验表明它能很好地模拟对流扩散过程,数值粘性小,精度高,稳定性好,并且没有伪振荡现象发生。     

声阻法中检测阻抗的测量和提高检测器灵敏度的设计

本文在声阻法检测器等效线路的基础上,提供一种测量检测阻抗的简捷方法。在已知检测阻抗的基础上,对于脱粘状态,进一步探讨了为提高检测灵敏度,如何选择检测器一些参量的方法。理论分析与实验结果较好地符合。对于脱粘状态的检测,灵敏度可以提高五倍以上。     

MODEL-ORDER REDUCTION AND PASS-BAND BASED CALCULATIONS FOR DISORDERED PERIODIC STRUCTURES

This paper is concerned with the dynamics of disordered periodic structures. The free vibration problem is considered. A method akin to the Rayleigh method is presented. This method is particularly suitable for the study of periodic structures as it exploits the nominal periodicity leading to an approximation that greatly reduces the order of the model. The method is used to calculate the natural frequencies and mode shapes for a pass-band by treating the unknown phases between the nominally identical bays as the generalized co-ordinates of the problem. An illustrative example of a cyclically coupled beam model is presented. In spite of a very large reduction in the computational effort, the results obtained are very accurate both for frequencies and mode shapes even when strong mode localization is observed. To test the performance of the proposed approximation further, a situation where two pass-bands are brought close to each other is considered (a coupled beam model having inherent bending-torsion coupling). The method presented here is general in its formulation and has the potential of being used for more complex geometries.     

光刻胶特性曲线参数测量的新方法

文中通过台阶实验的数据结合光刻胶光栅掩模的槽形,得到光刻胶特性参数,利用这些参数可以模拟出任一曝光量,任一显影时间,任一空频下,光栅掩模的槽形.为今后制作符合要求的光栅提供有力依据.     

CRACK DETECTION IN BEAM-TYPE STRUCTURES USING FREQUENCY DATA

A practical method to non-destructively locate and estimate size of a crack by using changes in natural frequencies of a structure is presented. First, a crack detection algorithm to locate and size cracks in beam-type structures using a few natural frequencies is outlined. A crack location model and a crack size model are formulated by relating fractional changes in modal energy to changes in natural frequencies due to damage such as cracks or other geometrical changes. Next, the feasibility and practicality of the crack detection scheme are evaluated for several damage scenarios by locating and sizing cracks in test beams for which a few natural frequencies are available. By applying the approach to the test beams, it is observed that crack can be confidently located with a relatively small localization error. It is also observed that crack size can be estimated with a relatively small size error.     

VIBRATION-BASED DAMAGE IDENTIFICATION USING RECONSTRUCTED FRFS IN COMPOSITE STRUCTURES

This work aims to establish a vibration-based damage identification method for fiber-reinforced laminated composites and their sandwich construction. This new on-line structural damage identification technique uses the structural dynamic system reconstruction method exploiting the frequency response functions (FRFs) of a damaged structure. To verify the effectiveness of this damage identification method, the frequency responses obtained by vibration testing of fatigue-damaged laminated composites and honeycomb sandwich beams with debonding are examined according to the extent of the damage via the fatigue-damage load cycle for laminated composites, and via the debonding extent for honeycomb sandwich beams. The changes of the peaks and valley of the FRFs according to the debonding extent and the fatigue load cycles are examined, and the area changes in the FRFs are also discussed as the damage index. The residual FRFs or the difference between intact and damaged FRFs are newly defined for application of the on-line damage identification method. Finally, the delamination extent for the sandwich beams and the fatigue damage level for the laminated composites can be easily identified in terms of the changes in natural frequencies and damping ratios of the reconstructed FRFs for these damaged composite structures.     

自适应背景对消法在小目标检测中的应用

在小目标跟踪过程中，如何把目标从复杂背景中提取出来是实现跟踪的前题，根据运动背景下运动小目标的特点，提出自适应背景对消滤波法，该方法利用图像序列的相关性来检测目标。     

A NEW METHOD FOR SEPARATING LONGITUDINAL WAVES IN A LARGE DIAMETER HOPKINSON BAR

This paper outlines various methods for separating fundamental longitudinal waves propagating along a Hopkinson pressure bar. Advantages and disadvantages of the different methods are presented and discussed in detail. A new method is then proposed for separating the fundamental waves in the frequency domain. This new method is based on the assumption that wave propagation can be adequately described by the first mode of the Pochhammer-Chree theory. The method requires two-point strain gauge measurements on the pressure bar. Fourier components of the positive wave at one gauge location are determined either from the corresponding Fourier components of the measured strain histories or from their derivatives. The method also makes use of the derivative of the wave number with respect to the circular frequency of the pressure bar. Important points of the implementation of the technique are described. Numerical accuracy of the proposed method is verified by considering a simple example with analytical solution and by comparing measured data derived from a large diameter Hopkinson pressure bar. The proposed method will find application in dynamic material tests using the split Hopkinson pressure bar technique.     

多介质体散射的共轭梯度解法

讨论多个介质体的电磁散射体积分方程的共轭梯度迭代求解方法,给出了介质板上方具有介质目标时的电磁散射的数值结果。     

谱方法用于非定常流动计算的隐式求解

本文对谱方法用于周期性非定常流动的隐式求解方法进行了探讨,分析了影响计算稳定性和收敛速度的因素.提出了结合多重网格的隐式求解方法并对算法进行了验证,初步计算表明本文算法具有良好的稳定性和收敛速度.对于周期性非定常流动,结合本文提出的隐式求解的时域谱方法可以达到很高的精度且具有良好的计算效率.     

A NUMERICAL STUDY OF STRUCTURAL DAMAGE DETECTION USING CHANGES IN THE ROTATION OF MODE SHAPES

Damage detection using changes in global dynamic characteristics has been a hot research topic and attracted civil, aerospace, and mechanical engineering communities in recent years. In this paper, a numerical study of the relationship between damage characteristics and the changes in the dynamic properties is presented. It is found that the rotation of mode shape is a sensitive indicator of damage. The numerical results clarify that the rotation of mode shape has the characteristic of localization at the damaged region even though the displacement modes are not localized. Also, the results illustrate that the rotations of modes are robust in locating multiple damage locations with different sizes in a structure. Furthermore, using the changes in the rotation of mode shape does not need very fine grid of measurements to detect and locate damage, effectively.     

高热流作用下微通道内的周期性射流特性

在低质量流速和高热流密度下,对深度为30μm的微通道内的流动沸腾进行了实验研究,发现了毫秒级周期性喷射流型、液膜的波动及液丝的断裂现象.分析表明,喷射周期的长短与沸腾数(Bo)有关,界面非平衡蒸发导致液丝失稳及液膜波动;微通道宽度方向上的Marangoni效应引起液膜和液丝的收缩、波动及断裂.     

MODERN NMR TECHNIQUES FOR THE STUDY OF LARGE PROTEINS IN SOLUTION

A number of important methodological developments in high resolution NMR spectroscopy have led to significant increases in the size limitations that previously impeded solution structural studies of macromolecules. Specifically, isotope labeling and TROSY triple resonance spectroscopy has resulted in substantial sensitivity and resolution gain for applications to large molecular weight proteins.     

全超导托卡马克极向场超导线圈的失超检测

EAST装置做为全超导托卡马克装置,其纵场和极向场线圈全部由超导磁体组成,所以进行安全,准确,有效的超导线圈的失超保护是装置安全运行的首要环节.由于等离子体电流的建立必须由极向场线圈系统提供极快速的磁通变化,随之产生较高的交流损耗使得极向场线圈很容易发生失超.如何对快速交变脉冲磁场下的超导线圈进行有效的失超检测,这在世界上也无先例可循.EAST装置的失超检测系统经过几十轮单饼超导线圈实验及多轮装置正式放电实验后逐步建立和完善起来,并已通过工程验收满足了装置实验运行要求.本文主要介绍了EAST装置失超检测系统的基本结构和检测原理,重点阐述了极向场超导磁体失超检测的设计方法及实验结果。