用傅里叶变换—目标因子分析方法对六种氨基酸进行同时测定

对六种氨基酸混合溶液的紫外光谱数据进行傅里叶变换，然后用傅里叶系数进行目标因子分析，计算结果令人满意。     

用于FTS干涉图信号处理的多阶带通滤波器研究

滤波技术的应用是傅里叶变换光谱仪对于光源光谱再现的关键,利用连续时间滤波器Max274设计了Chebyshev带通滤波器,结合实际研制的16阶带通滤波器性能与设计指标符合较好.限制了傅里叶变换光谱仪测量频宽,有效克服了光谱仪光谱测量中汞灯光源交流信号的影响.     

FTIR和Raman光谱技术的进展

本文报道了傅里叶变换红外光谱、傅里叶变换拉曼光谱、约外显微镜和显微拉曼光谱的特点与进展。     

热重分析中逸出气体的傅里叶变换红外光谱测量

随着傅里叶变换红外光谱技术的迅速发展,一些新的联用技术不断涌现并日趋成熟。本文旨在介绍热重分析-傅里叶变换红外光谱(TGA-FTIR)的联机方法、数据处理及结果表示,并以几个实例说明其应用。     

手持式傅里叶变换红外光谱技术的特点及其在无损检测方面的应用

红外光谱因为其具备官能团指认和指纹光谱的性质,广泛应用于物质鉴定、目标物快速筛选和定量分析.傅里叶变换红外光谱仪(FTIR)因其精度高和扫描速度快,目前是主要的红外分析手段.傅里叶变换虹外光谱仪器因为其光学系统的设计,对环境温度、温度十分敏意,分析一般只能在严格控制温度和湿度的实验室进行.随着虹外分析技术的普及,对仪器的应用也更加专业化,并出现进行现场分析的要求.安捷伦公司针对新的应用需求,推出了带有专利干涉仪设计的41 00ExoScan手持式傅里叶变换虹外光谱仪,把分析实验室推到了需要分析的现场,使红外光谱的快速分析效能得到最大的发挥.     

傅里叶光谱仪的智能数据采集器与光谱数据处理系统

根据傅里叶光谱学的基本原理,组成傅里叶变换光谱仪实时数据采集和处理系统。系统中智能数据采集器对干涉图作数据采集,配以干涉图处理与谱图变换软件包的IBM-PC/XT微机作为光谱数据处理系统,对干涉图进行数据处理与谱图变换,以获得正确的光谱图。     

基于扩展傅里叶变换的可变带宽滤波器设计

本文提出了一种基于扩展傅里叶变换（EFT）的可变带宽滤波器（VBF）设计方法。文中定义了扩展傅里叶变换和线性准时不变（LQTI）系统,分析了线性准时不变系统在扩展傅里叶变换域的频率特性,并利用线性准时不变系统的可变带宽频率特性来构建可变带宽滤波器,同时详细分析了可变带宽滤波器的通带变化情况。这种可变带宽滤波器基于一种简单的更新机制,能够有效降低运行时的复杂度。实验结果证明了基于扩展傅里叶变换的可变带宽滤波器的有效性。     

一种抛光液的化学成份分析

对一种水溶性的抛光液产品,在烘除水分后采用有机溶剂进行分离处理,对分离处理后的样品通过傅里叶变换红外光谱仪进行红外光谱测试,并对测试的红外谱图进行解析。结合红外光谱分析和电镜/能谱对元素的检测结果 ,确定样品的成分。在定性分析基础上采用原子吸收光谱法及常规化学分析方法进行定量分析,给出样品的定性和定量分析结果 。     

光导纤维在傅里叶变换红外及拉曼光谱中的发展及应用

本文简要介绍了光导纤维传输光的基本原理,总结了近红外和中红外波长范围的光导纤维的实际应用状况及其近年来光导纤维材料的发展与改进,并对光导纤维在傅里叶变换近红外光谱(FT-NIR)、中红外光谱(FT-MIR)及傅里叶变换拉曼光谱(FT-Raman)中的广泛应用作了综述。     

航空发动机振动数据稀疏傅里叶变换分析

稀疏傅里叶变换是近年来新兴的一种基于信号稀疏特性的频谱分析方法,稀疏傅里叶变换通过识别舍弃对分析结果无影响的频率信号,从而对大数据进行快速准确的处理。为了探究稀疏傅里叶变换在航空发动机振动数据分析中的实用性,结合实际飞行试验振动数据,将稀疏傅里叶变换方法与传统快速傅里叶变换方法在频谱特性、运行时间、算法稳定性等方面进行了研究,通过对比可以发现,稀疏傅里叶变换算法在保证准确率的情况下,可以极大地提高振动数据分析的效率。     

基于WVD谱峭度法在轴承故障诊断中的应用

在对基于短时傅里叶变换(STFT)和基于小波变换的谱峭度法分析的基础上,提出了基于W igner Vil le分布的谱峭度法。将其作为检测工具,利用谱峭度构造最优滤波器提取轴承故障 信息。将这三种谱峭度法应用于滚动轴承故障诊断中进行对比分析。分析结果表明，时频分析方法对信号能量的集中程度和时窗与滤波器的选取是影响谱峭度法应用效果的主要因素。该结果对基于时频分析的谱峭度法理论体系的形成及其在故障诊断中的应用具有实际意义。     

Deconvolution of Stark broadened spectra for multi-point density measurements in a flow Z-pinch

Stark broadened emission spectra, once separated from other broadening effects, provide a convenient non-perturbing means of making plasma density measurements. A deconvolution technique has been developed to measure plasma densities in the ZaP flow Z-pinch experiment. The ZaP experiment uses sheared flow to mitigate MHD instabilities. The pinches exhibit Stark broadened emission spectra, which are captured at 20 locations using a multi-chord spectroscopic system. Spectra that are time- and chord-integrated are well approximated by a Voigt function. The proposed method simultaneously resolves plasma electron density and ion temperature by deconvolving the spectral Voigt profile into constituent functions: a Gaussian function associated with instrument effects and Doppler broadening by temperature; and a Lorentzian function associated with Stark broadening by electron density. The method uses analytic Fourier transforms of the constituent functions to fit the Voigt profile in the Fourier domain. The method is discussed and compared to a basic least-squares fit. The Fourier transform fitting routine requires fewer fitting parameters and shows promise in being less susceptible to instrumental noise and to contamination from neighboring spectral lines. The method is evaluated and tested using simulated lines and is applied to experimental data for the 229.69 nm C III line from multiple chords to determine plasma density and temperature across the diameter of the pinch. These measurements are used to gain a better understanding of Z-pinch equilibria.     

红外傅里叶光谱仪的仪器线形函数及工程应用

提出了利用定量化的仪器线形函数对面阵傅里叶光谱仪像元进行光谱修正的方法。系统介绍了傅里叶光谱仪的仪器线形函数,结合仪器的自身特征建立了仪器线形函数模型,并利用MATLAB进行了仿真计算。通过理论计算给出了中心像元和边缘像元的激光光谱波峰之间的差值,其同实际值的相对误差均值仅为4.21%,修正后的边缘像元光谱准确度达到10-5量级。得到的结果从理论角度证明了利用仪器线形函数对面阵型傅里叶光谱仪进行光谱修正的有效性。最后从实际工程应用的角度出发,提出了针对面阵傅里叶光谱仪非中心像元光谱修正的方法。实验显示该方法具有很强的普适性,可在保证较高光谱准确度的基础上极大地提高光谱定标的效率,降低光谱定标的工作量。     

Mallat算法的光学实现方法

现有的光学小波变换方法均基于连续小波变换,基于离散信号的小波变换算法（Mallat算法）的光学小波变换还没有出现,这阻碍了光学小波变换应用的发展。针对这一问题,分析利用光学4f系统实现Mallat算法的基本原理,提出Mallat算法的光学实现方法。针对空间光调制器只能实现非负的实函数,且CCD只能记录光的强度,给出一种应用于光学4f系统的光学小波滤波器的设计方法。使用该种光学小波滤波器,利用光学4f系统实现Mallat算法的小波分解部分,并通过数值计算实现Mallat算法的小波重构部分。仿真分析和光学实验结果验证了方法的正确性。     

Denoising of measured lightning electric field signals using adaptive filters in the fractional Fourier domain

In this paper, adaptive filters are applied (in the fractional Fourier transform domain – FRFd) for denoising lightning electric-field signals, both in high and low signal-to-noise-ratio (SNR) environments. These filters are based on the concentration energy property of the fractional Fourier transform (FRFT). The proposed method integrates the advantages of leakage least mean square (LLMS) and normalized least mean square (NLMS) algorithms, including a leakage factor γ and a normalized step-size μ, in order to reduce the memory effect when tracking a non-stationary signal and also to reduce the effect of the input signal power on the algorithm performance, respectively. Parameter estimation of adaptive filters is analyzed in several case studies for various lightning-generated electric field signals. The adaptive algorithm is shown to provide better performance in low SNR environments. Finally, some analyses (in terms of temporal parameters of lightning electric-field signals) are included to demonstrate the validity of the method.     

DETERMINATION OF CONCENTRATION AND TEMPERATURE BY A FABRY-PEROT CAVITY FORMED BY TWO FIBER BRAGG GRATINGS

A sensing system based on a Fabry-Perot cavity formed by two fiber Bragg gratings for simultaneous measurements of temperature and liquid concentration is reported. Detailed analysis and discussion of the spectral transmission characteristics of the device are provided based on Coupled-Mode Theory. Through numerical simulation of spectral transmission, reflection spectra are shown to be influenced by the grating and Fabry-Perot cavity lengths, and sensing properties of temperature and liquid concentration are studied. A fast Fourier transform based demodulation method that simultaneously demodulates temperature and liquid concentration signals of the device was studied. The use of the fast Fourier transform provides absolute measurements with high sensitivity. The temperature sensitivity was 0.0104 nm/°C, the resolution was 1°C, the error of repeatability was 4%, the hysteresis was less than 0.010 nm, and the sensitivity of the measurement on liquid reflection was 0.01%.     

EXAMINATION OF ORAL TISSUES BY FOURIER TRANSFORM SPECTRAL IMAGING FLUORESCENCE

Fourier transform imaging spectroscopy was combined with fluorescence microscopy and a cooled CCD detector for examination of human oral tissues. Oral tissue fragments, obtained from patients, were irradiated at 365 nm by a mercury lamp through the microscope objectives. Microscope images were transferred to an imaging Fourier transform spectrometer and to a CCD camera for simultaneous recording of the fluorescence spectra at each image pixel. Detailed information was observed at a microscopic resolution. Oral tissue fragments were also treated with aluminum phthalocyanine tetrasulfonatre (AlPcS₄) prior to irradiation and imaging. Since the latter is preferentially retained in proliferating vascular tissue such as oral tumors, its effect upon the fluorescence imaging is of practical importance. AlPcS₄ is highly soluble in biological solutions and has a strong absorbance at our excitation wavelength and a strong emission peak at λ = 680 nm; therefore, it was found suitable for detection of malignant tumors by this method. It was found that the proposed spectral imaging method, when combined with fluorescence labeling, allows for direct, in vivo, medical examination of oral tissues with detailed spatial resolution.     

基于正交小波变换的计权声级测量

提出了采用正交小波变换进行计权声级测量的方法 ,克服了传统计权声级测量系统中采用模拟计权网络的缺点 ,比采用短时傅里叶变换方法更能反映人耳对噪声的主观感觉特性。理论分析和仿真计算表明 ,该方法是可行的。为了进一步提高计算精度和减少计算复杂度 ,给出了对应于 IIR滤波器的正交小波变换、自适应小波包变换和匹配小波变换等三种可能的改进方法。     

基于Hilbert-Huang变换与理想带通滤波器的系统识别

针对经验模态分解存在模态混叠现象,提出基于Hilbert-Huang变换与理想带通滤波器的系统识别方法。该方法利用傅里叶变换得到结构加速度响应频响函数,粗略估计固有频率范围,通过半功率带宽法设计理想带通滤波器,定量化确定通带带宽,使信号在经过滤波器后频域内零相移,同时不改变其幅值谱。结构响应通过指定频带的理想带通滤波器产生若干窄带信号,利用经验模态分解获取结构模态响应,经Hilbert变换构造模态响应解析信号,并通过线性最小二乘拟合提取结构模态参数与物理参数。结果表明:半功率带宽法可实现带通滤波器频带的定量化设计,理想带通滤波器的零相移特点较好契合Hilbert-Huang变换用于系统识别的要求,两者结合可有效地解决模态混叠现象,减少虚假模态,大大提高结构系统识别精度。