CAJ | 학술논문

二代小波是公认较好的降噪手段，但是降噪效果依赖于基函数、分解层数和阈值等参数设置。经验模态分解（empirical mode decomposition ，EMD）无需参数设定，按照频率特性将信号分解成本征模函数（in-trinsic mode function ，IM F），对IM F滤波，实现了信号自适应去噪。拉曼光谱中信号和噪声交叠集中在极高频段，EMD产生模态混叠问题，影响去噪效果。应用总体平均经验模态分解（ensemble empirical mode de-composition ，EEMD）拉曼光谱克服了模态混叠，有效区分出高频信号和噪声，获得了与小波函数相似去噪效果。文中首先对一段非线性非平稳豆油脂拉曼光谱EMD分解，可见模态混叠，EEMD分解出清晰模态的特征分量。然后分别用快速傅里叶变换（fast Fourier transform ，FFT ）、小波变换（Wavelet）、EMD和EEMD处理含噪光谱，信噪比、均方根误差、相关系数三个方面指标表明 FFT 高频去噪效果最差，其次是EMD ，恰当的Wavelet同EEMD效果相当，EEMD的优势是降噪过程的自适应。最后提出光谱时频分析方法和IM F噪声属性判别准则研究趋势。
이대소파시공인교호적강조수단，단시강조효과의뢰우기함수、분해층수화역치등삼수설치。경험모태분해（empirical mode decomposition ，EMD）무수삼수설정，안조빈솔특성장신호분해성본정모함수（in-trinsic mode function ，IM F），대IM F려파，실현료신호자괄응거조。랍만광보중신호화조성교첩집중재겁고빈단，EMD산생모태혼첩문제，영향거조효과。응용총체평균경험모태분해（ensemble empirical mode de-composition ，EEMD）랍만광보극복료모태혼첩，유효구분출고빈신호화조성，획득료여소파함수상사거조효과。문중수선대일단비선성비평은두유지랍만광보EMD분해，가견모태혼첩，EEMD분해출청석모태적특정분량。연후분별용쾌속부리협변환（fast Fourier transform ，FFT ）、소파변환（Wavelet）、EMD화EEMD처리함조광보，신조비、균방근오차、상관계수삼개방면지표표명 FFT 고빈거조효과최차，기차시EMD ，흡당적Wavelet동EEMD효과상당，EEMD적우세시강조과정적자괄응。최후제출광보시빈분석방법화IM F조성속성판별준칙연구추세。
It is well known that the second generation wavelet is the best de-noising means ,but the result of de-noising depends on how to set up the basis function ,decomposition layers and threshold parameters .Without parameter setting empirical mode decomposition (EMD) decomposes the signal into intrinsic mode functions (IMF) ,then structuring IMF filter and the de-noising process is adaptive .It is worth noting that the signal and the noise are mixed together in very high frequency ,that is to say that there has been mode overlap ,and what happened will affect the de-noising effect .It was found that ensemble empirical mode de-composition (EEMD) decomposes Raman spectrum into the signal and the noise effectively avoiding from mode overlap in high frequency in the experiments ,and it is similar with wavelet in de-nosing effect fortunately .At first ,a period of non-linear and non-smooth bean greases Raman spectrum was decomposed by EMD in the paper ,there was mode overlap ,but the authors have got clear characteristic components by EEMD .Secondly noisy spectrum was processed by fast Fourier transform (FFT ) ,wave-let ,EMD and EEMD independently ,and signal to noise ratio ,root mean square error and correlation coefficient indicate that FFT is the worse means in high frequency de-noising than EMD ,and the appropriate wavelet is similar with EEMD in de-noising result ,but the de-noising process of EEMD is adaptive .In the last section ,a brief research direction of the spectrum study method in time frequency field and noise properties criterion on IM F are given for the future .