Spectral compression

Owens, P.M. and Isenhour, T.L., Infrared Spectral Compression Procedure for Resolution Independent Search Systems , Analytical Chemistry 55, 1548-1553 (1983). 

Spectral compression with wavelet neural network... 

A.K.M. Leung, F.T. Chau. J.B. Gao and T.M. Shih. Application of Wavelet Transform in Infrared Spectrometry Spectral Compression and Library Search, Chcmometric Intelligent Laboratory System. 43 (1998). 69-88. 

F.T. Chau, J.B. Gao. T.M. Shih and J. Wang. Infrared Spectral Compression Procedure using the Fast Wavelet Transform Method. Applied Spectroscopic. 51 (1997). 649-659. 

Application of Wavelet Transform in Infrared Spectrometry Spectral Compression and Library Search. 

Hicks, B.L., Braida, L.D., Durlach, N.I. (1981) Pitch invariant frequency lowering with nonuniform spectral compression. ICCASP Proc. vol. 6, IEEE Int. Conf. on Acoustics, Speech and Signal Processing, New York, pp 121-124... 

We can also condense the dimensionality of our spectra in other ways. One of the most common, and often one of the best, ways is to work with integrated areas of analytically important spectral peaks. We will see in the next chapters, that the factor based methods, PCR and PLS, are nothing more than ILS conducted on data that is first optimally compressed. 

The absorption characteristics of PS I were measured on the four kinds of subphase surfaces during compression. As an example, Figure 2 shows the absorption spectra of the PS I monolayers on the PBV subphase surface under different surface pressures. Two absorption bands at about 420-450 and 676 nm increase with the compression, indicating the accumulation of the PS I to form a condensed monolayer. Compared to the absorption spectrum of PS I in solution (Fig. 3), the band at around 436 nm splits into two peaks. The wave-shaped small band between 470 and 630 nm is due to a low single-to-noise ratio on the water surface. These spectral features together with the jt-A isotherms indicate that PS I remains at the interface, and that the loss of PS I, due to dissolving into the subphase, is not significant [2],... 

Figure 15. Spectral change with time for the mixed monolayers of [MC18] [MA] [HD] and [MC18] [AA] [HD] on the aqueous subphase containg CdCfe and KHCO3 on compression at 15 mN/m. 

In the method, a weighed portion of a sample of coke dried at 110°C (230°F) and crushed to pass a No. 200-mesh sieve, mixed with stearic acid, and then milled and compressed into a smooth pellet. The pellet is irradiated with an x-ray beam and the characteristic x-rays of the elements analyzed are excited, separated, and detected by the spectrometer. The measured x-ray intensities are converted to elemental concentration by using a cahbration equation derived from the analysis of the standard materials. The K spectral lines are used for aU the elements determined by this test method. This test method is also apphcable to the determination of additional elements provided that appropriate standards are available for use and comparison. 

While periodically-poled materials are typically characterized by very narrow spectral acceptance bandwidths (< 1 nm), aperiodically-poled structures (characterized by a linear gradient in grating period) have the advantage of providing sufficiently broad spectral acceptance bandwidths to utilize more of the spectrum associated with picosecond and femtosecond" pulses. They can also simultaneously provide some pulse compression of sufficiently pre-chirped incident pulses ... 

A disadvantage of Fourier compression is that it might not be optimal in cases where the dominant frequency components vary across the spectrum, which is often the case in NIR spectroscopy [40,41], This leads to the wavelet compression [26,27] method, which retains both position and frequency information. In contrast to Fourier compression, where the full spectral profile is fit to sine and cosine functions, wavelet compression involves variable-localized fitting of basis functions to various intervals of the spectrum. The... 

Conformational transitions and electron redistribntion on pressure results in changes of the ion-radical properties and this is essential for optoelectronic devices. Pressure is the thrust distributed over a surface. The most important results of compression are reduction of molecular volumes and conformational changes of organic componnds. Spectral changes of solids are also termed piezo-chromism. Let ns consider several relevant examples of piezochromism. 

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