Spectral ratioing

Most FTIR spectrometers are single-beam instruments, and, accordingly, in 

It should be noted that the contributions of the air background spectrum will only be completely removed by the spectral ratioing procedure if they are constant. Changes in the relative humidity and CO2 levels in the air in the 

---

On metals in particular, the dependence of the radiation absorption by surface species on the orientation of the electrical vector can be fiilly exploited by using one of the several polarization techniques developed over the past few decades [27, 28, 29 and 30], The idea behind all those approaches is to acquire the p-to-s polarized light intensity ratio during each single IR interferometer scan since the adsorbate only absorbs the p-polarized component, that spectral ratio provides absorbance infonnation for the surface species exclusively. Polarization-modulation mediods provide the added advantage of being able to discriminate between the signals due to adsorbates and those from gas or liquid molecules. Thanks to this, RAIRS data on species chemisorbed on metals have been successfidly acquired in situ under catalytic conditions [31], and even in electrochemical cells [32]. 

S.R. stands for spectral ratio, i.e., the a-particle count ratio between 212 Po and 212Bi. ... 

The spectral ratios (S.R.) given in Tables II and III show that Nuclepore filters and copper discs have the highest S.R., indicating that less degradation of the spectra, and hence, highest energy resolution, occurs. It should be noted, that except for cotton cloth (Table II), there seems to be a correlation between the S.R. and the activity plated-out on the material. 

During the first five sampling cruises on the Mississippi River near its mouth below Belle Chasse, Louisiana, the correlations among peak spectral ratios, discharge, and suspended sediment concentrations were measured... 

Table VI. Correlations (r2) of Peak Spectral Ratio, Discharge, and Suspended Sediment Concentrations...

H-NMR Peak Spectral Ratio Discharge (r2) Sediment Concentration (r2)... 

For each Al-Al pair, there are two Al s with an Al neighbor. Thus all the Al s in the sample have a total of 2n. Al neighbors. Since the total number of all the neighbors of Al atoms is 4n, we have 4n-2n. Si-Al bonds. Thus, the total number of Al neighbors of all Si s is also 4n-2n.. The ratio of this number to the total number of Si atoms, N-n, should be equal to the spectral ratio (I,j + 21+ 3Ij + 4I )/It0t. This directly leads to the above expression for x Q.E.D. 

Hilf et al.50 used the paper chromatography method by Algeri and Walker49 using descending chromatography. After development and detection of the barbiturate spot, the silver-barbiturate salt spot was cut out of the paper, shredded and extracted in order to obtain confirmation of identity by ultraviolet spectral ratios. 

The resulting value (A(fjj, x)) is related to that part of the frequency band which predominantly contributes to the spectral sum, i.e. to the arithmetic mean frequency (f j) of the spectral amplitude distribution within the i band. Subsequently, for a continuously moving window a series of attenuation coefficients (ot(f j)) is computed from the natural logarithm of the spectral ratio of the attenuated and reference signal... 

Fig. 2.14 Attenuation analysis by the smoothed spectral ratio method, (a) Definition of a moving window of bandwidth in which the spectral amplitudes are summed, (b) Seven attenuation curves analyzed from the...

Another method of site response, which does not depend on the reference site, is based on horizontal to vertical spectral ratio (HVSR). In this method the horizontal component ofthe response spectra is normalized using the vertical component of the spectra for the site under consideration. This method can be applied for both the noise recordings (Nakamura, 1989 Field and Jacob, 1993) and the earthquake recordings. 

The site specific elastic design spectra was developed compatible to Indian standard IS 1893 -2002 design spectra (Type 1 soil) by RRS analysis and it indicates that the spectral ratio (Sa/g) at the short and mid period ranges up to about 0.6s is 20% higher than the IS spectral ratio values. 

Mprkrid, L., Ohm, O.-J., Hammer, E., 1980. Signal source impedance of implanted pacemaker electrodes estimated from spectral ratio between loaded and unloaded electrograms in man. Med. Biol. Eng. Comput. 18, 223—232. 

Stabile TA, Peirone A, Gallipoli MR, Ditommaso R, Ponzo FC (2013) Dynamic survey of the Musmeci bridge by joint application of ground-based micro-wave radar interferometry and ambient noise standard spectral ratio techniques. IEEE GRSL 10(4) 870-874. doi 10.1109/LGRS.2012.2226428... 

Acceleration FAS are often analyzed to decompose the observed ground motion into the spectral functions describing the source of the event, the propagation from the source to the site, and the site effect (Castro et al. 1990 Bindi et al. 2009). Acceleration FAS are also used to estimate the empirical site response, through the Standard Spectral Ratio (SSR Tucker and King 1984), based on the ratio between the FAS between the horizontal (or vertical) components of the selected site and a reference site or the Horizontal to Vertical Spectral Ratio (HVSR Lermo and Chavez-Garcia 1993) based on the ratio of the FAS between the horizontal and vertical component of a single station, that provides reliable estimates of the fundamental frequency when the site effects are mainly controlled by resonance phenomena. 

Finally, standard spectral ratio (SSR) and horizontal-to-vertical spectral ratio (HVSR) methods for the determination of the deposit fundamental frequencies are becoming increasingly popular not only in the research field but also in professional practice (i.e., for microzonation studies). Site amplification factors can, in fact, be inferred, at least in the linear strain range, using the SSR technique described by Field and Jacob (1993). HVSR amplifications obtained experimentally can, instead, be used to validate numerical model results (e.g., SESAME 2004 Lanzo et al. 2011). 

SESAME (2004) Guidelines for the implementation of the HA spectral ratio technique on ambient vibrations measurements, processing and interpretation. SESAME European Research Project. WP12 - Deliverable D23.12... 

---