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141.
142.
分散液液微萃取-在线衍生化-气相色谱-质谱联用法检测环境水样品中紫外吸收剂 总被引:1,自引:0,他引:1
建立了分散液液微萃取(dispersive liquid-liquid microextraction,DLLME)-在线衍生化-气相色谱-质谱(GC-MS)方法,将其用于环境水中6种二苯甲酮类紫外吸收剂(BPs)(二苯甲酮、2,4-二羟基二苯甲酮、2-羟基-4-甲氧基二苯甲酮、4-羟基二苯甲酮、2-羟基-4-辛氧基二苯甲酮、2,2'-二羟基-4,4'-二甲氧基二苯甲酮)的检测。系统优化了在线衍生化的条件(如进样口温度、不分流时间、衍生化试剂用量)以及DLLME萃取条件(如萃取剂种类、分散剂种类、萃取剂与分散剂比例、样品体积、样品溶液离子强度及pH值)等。在最优的条件下,所考察的6种BPs检出限为0.011~0.15 μg/L,重现性(RSD)为0.7%~16.6%。该方法结果准确可靠,操作简单,富集效果好,成本较低,环境友好,在实际样品检测中具有一定的应用前景。 相似文献
143.
Y. Sheng D. Roberge L.Gonçalves Neto L. Shen G. Paul-Hus 《Optics & Laser Technology》1996,28(2):129-134
We obtain continuous phase modulation with commercial twisted nematic liquid television. We present theory and experimental implementation of kinoforms, matched spatial filters, circular harmonic filters and synthetic discriminant functions with the phase-mostly filter approach. 相似文献
144.
This paper describes the design and performance of various millimeter-wave printed-circuit filters and diplexers. These components include microstrip/suspended stripline and finline lowpass filters, capacitive-gap and inductive-iris-coupled bandpass filters, spurline bandstop filters, and finline diplexers. State-of-the-art performances from Ka-band (26.5 to 40 GHz) to D-band (110 to 170 GHz) have been obtained. Agreement between the measured and calculated results was also achieved. 相似文献
145.
Jose Patricio Díaz Varela Antoni Torrens Torrell 《Archive for Mathematical Logic》2006,45(8):1011-1020
?ukasiewicz implication algebras are {→,1}-subreducts of Wajsberg algebras (MV-algebras). They are the algebraic counterpart of Super-?ukasiewicz Implicational logics investigated in Komori, Nogoya Math J 72:127–133, 1978. The aim of this paper is to study the direct decomposability of free ?ukasiewicz implication algebras. We show that freely generated algebras are directly indecomposable. We also study the direct decomposability in free algebras of all its proper subvarieties and show that infinitely freely generated algebras are indecomposable, while finitely free generated algebras can be only decomposed into a direct product of two factors, one of which is the two-element implication algebra. 相似文献
146.
We continue investigations of reasonable ultrafilters on uncountable cardinals defined in Shelah [8]. We introduce a general scheme of generating a filter on λ from filters on smaller sets and we investigate the combinatorics of objects obtained this way. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
147.
Content-based image retrieval has been an active area of research for more than ten years.Gabor schemes and support vector machine (SVM) method have been proven effective in image representation and classification. In this paper,we propose a retrieval scheme based on Gabor filters and SVMs for hepatic computed tomography (CT) images query.In our experiments,a batch of hepatic CT images containing several types of CT findings are used for the retrieval test.Precision comparison between our scheme and existing methods is presented. 相似文献
148.
A nonlinear time-varying adaptive filter is introduced, and its derivation using optimal control concepts is given in detail. The filter, which is called the discrete Pontryagin filter, is basically an extension to Sridhar filtering theory. The proposed approach can easily replace the conventional methods of autoregressive (AR) and autoregressive moving average (ARMA) models in their many applications. Instead of using a large number of time-invariant parameters to describe the signal or the time series, a single time-varying function is enough. This function is estimated using optimization techniques. Many features are gained using this approach, such as simpler and compact filter equations and better overall accuracy. The statistical properties of the filter are given, and it is shown that the signal estimate will converge in thepth mean to the true value. 相似文献
149.
Construction of Two-Dimensional Compactly Supported Orthogonal Wavelets Filters with Linear Phase 总被引:3,自引:0,他引:3
Si Long Peng 《数学学报(英文版)》2002,18(4):719-726
In this paper, a large class of two-dimensional orthogonal wavelet filters, (lowpass and highpass), are presented in explicit
expression. We also characterize the filters with linear phase in this case. Some examples are also given, including non-separable
filters with linear phase.
Received September 28, 1999, Accepted July 24, 2000 相似文献
150.
There are perceived drawbacks to using adaptive IIR filters, as opposed to adaptive FIR filters, for active noise control (ANC). These include stability issues, the possible convergence of estimated parameters to biased and/or local minimum solutions and relatively slow rate of convergence. Stability issues can generally be resolved easily using well-established methods. In this Technical Note convergence rates are compared with particular reference to the active control of noise in a duct, for which the dynamics of the cancellation path are important. The characteristics of this application of ANC set it apart from usual signal processing applications of adaptive IIR filters and this has implications for the convergence properties. Various control approaches are considered: IIR least mean squares (IIR-LMS), IIR recursive least squares (IIR-RLS) with FASPIS (Fast Algorithm Secondary Path Integration Scheme) and FIR-LMS. Numerical examples are presented. It is seen that the cancellation path dynamics generally have the effect of changing the performance surface of the estimated IIR filter from bimodal to unimodal, which has consequences for improving the convergence rate of adaptive IIR filters. It is also seen that IIR-RLS has a comparable rate of convergence to FIR-LMS, with the steady-state performance being as good or better. 相似文献