聚焦区域高声强声场分布的测量方法研究

常用的声场分布测量是采用水听器扫描声场的方法,该方法对于声能量密度较大的声场难以测量,因为在这种情况下声振幅比较大,水听器在这种声场中呈现非线性或遭到破坏。设计了一种用辐射压力测量高声强声场分布的方法,该方法利用一根微细管,直接测量声场的冲流压力,通过对声场进行扫描测量可以得到高声强声场压力分布。从理论上分析了这种测量方法的可行性,对测量基本要求及实验装置做了阐述。实验结果证实:该方法可以用来测量高声能密度声场压力分布;测量结果与水听器测量结果基本吻合;测量方法存在测量盲区。     

Fast image method for impulse response calculations of box-shaped rooms

The image method has been used for calculating the impulse response of box-shaped rooms for over 25 years. While this method is functional, it can be inefficient because many of the commonly used mathematical operations are either redundant or unnecessary. This paper addresses these two inefficiencies by proposing both the use of look-up tables to prevent redundant calculations, and the use of a sorting method to allow the prevention of unnecessary calculations. Either technique, by itself, results in a large reduction in computation time. The greatest time reductions, however, can be achieved when both techniques are used together.     

Identification of nonlinear multi-degree-of freedom structures based on Hilbert transformation

The modeling method and identified method adapted to multi-degree-of-freedom structures with strucrural nonlinearities are established. The component mode synthesis method is used to establish the nonlinear governing equations by extending the connected relationships. Based on the modeling method, the Hilbert transform method is applied to identify the nonlinear stiffness of multi-degree-of-freedom structures. Nonlinear analysis and identification of a typical folding wing configuration with three freeplay hinges are investigated. The nonlinear governing equation is established based on present methods and the computing results of different stiffness are checked by finite element programming. In order to illustrate the influence of the nonlinearities, the frequency response characteristics of the structure are analyzed and Hilbert transform is performed. The Hilbert transform identification method is utilized to identify the nonlinear stiffness of nonlinear hinges in the time domain and several parametric studies are performed. In addition, the comparison of response is made to illustrate the feasibility of the methods. The results show that the extending component mode synthesis method in the present work can be used to establish the governing equation with structural nonlinearities. Based on the modeling method, the Hilbert transform identified method can be extended to multi-degree-of-freedom structures accurately.     

用触针下分布电阻的光电导相位法测量半导体中非平衡载流子寿命

本文提出一种测量半导体中非平衡载流子寿命的新方法。这方法是测量触针下分布电阻的光电导相位移,在不同的表面情况和不同的激发光光谱成分下,导得各种结果表达式,文中对通常所使用的测量条件即粗磨表面和长波激发条件给出数值计算的结果。同时,对这些结果进行较为详细的分析和讨论,这个方法具有一系列的优点。例如:1)可以在锭状晶体上测量;2)表面处理十分简单;3)在样品上不需制作固定电极;4)测量仪器简单,操作方便;5)有一定准确度。这个方法可以检验不均匀材料,可供科研机关作研究用,更适合于工厂检验单晶材料用。用这方法在锗和硅样品上进行测量,测得寿命值基本上与其它方法的结果一致。     

一种测量生物组织热导率的新方法

采用脉冲衰减法可以测量生物组织热导率。但是,Chen等人提出的脉冲衰减法采用了“点热源”假设,而实际测量时,探头有一定的几何尺寸,由此造成了测量时的模型误差。本文采用数值实验的方法对这一误差及其影响因素进行了分析。在此基础上,提出了一种考虑了探头尺寸影响的新的脉冲衰减法,推导出了其测量公式。采用已知热导率的工质进行了验证试验,实验测量结果证实了本文对原有测量方法误差的分析;同时也表明,采用本文提出方法可以将测量误差减小到5%以下。     

Extraction current transients: new method of study of charge transport in microcrystalline silicon

The transport properties of microcrystalline silicon, namely, mobility and conductivity, are investigated by a new method, for which the simple theory as well as numerical modeling is presented. The basic idea of the new method is verified on amorphous hydrogenated silicon by comparison with the widely used time-of-flight method. Contrary to time of flight, the new method can be used even for relatively conductive materials. Preliminary results on microcrystalline silicon clearly indicate the critical role of amorphouslike tissue in transport in microcrystalline silicon.     

一种新的360°三维轮廓术

提出了运用相移技术的光刀投影式测量３６０°回转物体三维轮廓的新方法。该方法对投影光刀引入正弦分布光场,利用相移技术对光刀投影狭缝进行相位计算,可得出各点的包裹相位分布,然后再利用光刀投影测量原理得到的高度信息对相位进行去包裹处理,从而得到具有较高精度的相位测量结果。最后根据相位与物体高度的几何关系,得到物体的三维轮廓数据。文中详细介绍了这一技术的原理及实验结果     

Preliminary Study on Measurement of Magnetic Center of Quadrupoles Using Quadrupole Shunt for Hefei Storage Ring

The theoretical analysis of the DC K-modulation of quadrupole for the beam-based alignment method is presented. It is shown that the shift of the orbit,when the focussing strength of one quadrupole magnet is changed,can be described by the perturbed or unperturbed linear lattice parameters. The beam-based alignment system is constructed using DC K-modulation of quadrupole. In order to use the beam-based alignment method one must be able to individually adjust the strength of the quadrupole magnet. So,a switchable shunt resistor is installed on quadrupole to bypass 1%-2.5% magnet current and some solid-state relays are used to switch the shunt resistor in this beam-based alignment system. To improve the measurement accuracy,two methods are used. First method is that beam positions in measured quadrupole magnet are moved by local bump of beam closed orbit using the corrector magnets. Second method is that the root-mean-square of difference in closed orbit is fitted by a parabola function. The system can be not only used to position the beam in the magnetic center of quadrupoles,but also to measure the β function in quadrupole magnets. Some preliminary measurement results are given for Hefei 800MeV electron storage ring. These experimental results show that this system is valid to position the beam to the center of the quadrupole magnets and measure the β function at Hefei Light Source.     

椭圆目标的亚像素边缘定位方法研究

分析和比较了三种常见的基于矩的亚像素边缘定位方法,得出三种方法获取的边缘角度以及OFMM法与ZOM法获取的亚像素边缘相同的结论。提出了一种针对椭圆目标的亚像素边缘定位方法。在ROI提取和SOBEL算子初步检测边缘的基础上,利用初步获取的椭圆目标的几何信息,将参与计算的模板个数减少至一个,从而大大减少了运算时间,提高了算法的运算速度。同时实验结果表明,与其他基于矩的亚像素边缘定位方法相比,新方法不仅有更高的运算速度,而且精度和抗噪性能都有很大地提高。     

ICP-AES测定水中铜结果的不确定度评定

介绍了ICP－AES法测定水中铜的不确定度的评定方法。由于等离子质谱仪（ICP－MS）、紫外分光光度计（UVS）、原子吸收分光光度计（AAS）及原子荧光光度计（AFS）等仪器在定量分析中，校准曲线的绘制，标准样品的使用，测定结果的输出等方面与ICP－AES极为相似，因此本方法不仅可以用于水中其他元素和其他材料的测量结果的评定，而且还可以在评定ICP－MS、UVS、AAS、AFS等仪器的测定结果不的确定度时作参考。     

辛几何算法在计算非磁化等离子体中波传播轨迹时的应用

为了在数值计算中保持哈密顿系统的辛几何结构不变,利用辛几何算法得到了在线性哈密顿系统中射线追踪方程的一般辛差分格式。通过具体算例,利用辛几何算法计算了波在非磁化等离子体中的传播轨迹,并且与传统Runge-Kutta-Fehlberg算法所得结果进行了比较。利用辛几何算法所得传播轨迹与解析解一致,其色散函数值的误差随时间线性增长,能在长时间内保持色散函数值在一个很小的误差范围内。利用传统的Runge-Kutta-Fehlberg算法所得传播轨迹与解析解不一致,其误差随时间做大幅振荡增加。计算结果表明辛几何算法在保持传播轨迹和色散函数值方面具有独特的优势。     

光谱法测量托卡马克等离子体

对托卡马克内部的等离子体进行光谱测量可以得到其内部各种等离子体的状态以及分布等信息。对于不同的测量对象,可以采用各种不同的测量仪器组合以得到较好的结果。文章列出了几种主要的实验方案以及各种方案的测量范围,还有部分测量结果。另外,根据实验的需要设计了另外一种实验组合方案。     

纺织品近红外光谱定性分析的一种新方法

近红外光谱分析技术可用于对样本的快速无损检测,在人们的生产和生活中发挥着越来越重要的作用。支持向量机是建立定性分析模型的常用方法,可通过寻找最优分类超平面将两类样本分开。在小样本情况下,支持向量机方法有其独特的优势。主成分分析是常用的数据降维方法,可将数据降维之后作为支持向量机方法的输入变量,简化模型并提高模型识别的准确性。因此,基于主成分分析的支持向量机(简称PCA-SVM)适合用于建立近红外光谱定性分析模型。多模型方法是人们使用较少的建模方法,用该方法建立的模型一般具有较好的稳定性。将多模型方法与PCA-SVM方法成功结合形成了新方法。以棉锦混合、棉涤混合纺织品为例,用新方法建立了这两类纺织品样本的近红外光谱定性分析模型。建模时将光谱数据按照波长分为4组,用每组光谱数据建立一个子模型,将子模型的输出值进行加权平均便得到最终的预测结果。这样可以更充分地使用光谱数据中所包含的信息。为了便于对比不同的方法,仍使用上述校正集和验证集,又用PCA-SVM方法建立了这两类纺织品样本的近红外光谱定性分析模型。对预测结果做交叉验证,用新方法所建模型判别的正确率的平均值为85.49%,正确率的标准差为0.066 7, 用PCA-SVM方法所建模型判别的正确率的平均值为83.34%,正确率的标准差为0.109 6。研究结果表明用新方法所建模型的分类效果好于用PCA-SVM方法所建模型的分类效果;用新方法建立的模型的稳定性明显高于用PCA-SVM方法建立的模型的稳定性。用PCA-SVM方法所建模型的预测效果受校正集构成情况的影响较大,而用新方法所建模型的预测效果则相对稳定。对废旧纺织品进行分类回收可大量节约纺织原材料,但采用人工分拣方式效率低且成本高。采用近红外光谱分析方法对纺织品进行分类,为废旧纺织品的大规模精细分拣和分级奠定了一定的基础。该新方法有望用于某些其他类型样本的分类。     

通过相移条纹图差分测定相移量的方法

提出一种通过两幅相移条纹图相减来确定它们之间相移量的方法,进行了理论分析和实验验证。两幅相移条纹图相减并归一化后,得到的相移差分函数是振幅只与相移量有关的正弦函数,可以通过确定该函数最大极值的方法得到振幅,进而计算出相移量。介绍了极值直接查找法和平均法两种实现最大极值测量的方法。由于不使用傅里叶变换,减少了运算时间,既可以用于高空间频率条纹,也可以用于稀疏平行条纹,以及任意花样的条纹。在衬比度因子确定后,用这种方法就能够直接在空域内确定两幅条纹图之间的相移量,通过大量采样点进行统计计算,使结果达到很高的精度。将所得到的结果与用傅里叶变换方法得到的结果进行了比较,表明两种方法得到的结果具有完全相同的精度。     

Transient vibration analysis of a completely free plate using modes obtained by Gorman's superposition method

This paper shows that the transient response of a plate undergoing flexural vibration can be calculated accurately and efficiently using the natural frequencies and modes obtained from the superposition method. The response of a completely free plate is used to demonstrate this. The case considered is one where all supports of a simply supported thin rectangular plate under self weight are suddenly removed. The resulting motion consists of a combination of the natural modes of a completely free plate. The modal superposition method is used for determining the transient response, and the natural frequencies and mode shapes of the plates used are obtained by Gorman's superposition method. These are compared with corresponding results based on the modes using the Rayleigh-Ritz method using the ordinary and degenerated free-free beam functions. There is an excellent agreement between the results from both approaches but the superposition method has shown faster convergence and the results may serve as benchmarks for the transient response of completely free plates.     

水下近水面锥柱组合壳声固耦合效应的半解析求解方法

针对水下近水面锥柱组合壳声固耦合多借助于数值方法求解的现状,本文提出一种半解析方法从机理上分析此类问题。首先基于能量泛函和Sanders壳体理论、虚拟弹簧法以及力与力矩平衡条件建立锥柱组合壳的结构模型;然后采用Legendre谱元法和二维傅里叶变换得到含自由液面的水下声场模型;最后由非线性迭代法和高斯积分求解耦合系统声振控制方程。通过与参考文献和数值方法结果的对比,验证了本文方法的收敛性、正确性和可靠性。研究结果表明,结构参数、浸没深度和激励频率与远场辐射声压密切相关。本文工作可推广到水下含内部结构的复杂旋转组合壳在不同结构边界及声边界下的声固耦合问题。      

The Application of Genetic Algorithm in E-Plane Waveguide Filter Design

Traditional optimization methods, such as Powell's method and the Simplex method, are generally very difficult to design high performance filters with the relative band-width less than 0.15% or more than 10%. In this paper, Genetic Algorithm (GA) is used to design filters that meet these requirements. Two special filters are designed in this paper with the relative band-width as 0.15% and 25%, respectively. The numerical results demonstrate that GA can be used to design filters of superior quality when compared to the filters designed by using Powell's method or Simplex method.     

单模激光驱动的超混沌系统的完全同步

利用主动-被动同步法实现了由单模激光驱动的超混沌系统的完全同步.根据稳定性理论,对系统进行了一般分解.以单模激光Lorenz系统和四维超混沌Chen系统为例,验证了这种方法的有效性.仿真模拟结果表明,这种同步方法是快速有效的.利用这种同步方法可以实现对任意高维混沌系统的混沌同步,具有一定的普适性.     

Topological soliton solutions for three shallow water waves models

In this article, we investigate three distinct physical structures for shallow water waves models by the improved ansatz method. The method was improved and can be used to obtain more generalized form topological soliton solutions than the original method. As a result, some new exact solutions of the shallow water equations are successfully established and the obtained results are exhibited graphically. The results showed that the improved ansatz method can be applied to solve other nonlinear differential equations arising from mathematical physics.     

同轴交错膜片加载慢波线的分析

膜片加载圆波导是相对论行波管最主要的慢波结构,同轴结构的膜片加载波导可以拓宽带宽。利用变分法对同轴交错膜片加载的慢波结构（亦称同轴径向线）进行了理论分析,得到了色散方程并进行了数值计算。计算结果表明,它比非同轴结构的带宽有明显的增加。