Phase Correction of Vibrational Circular Dichroic Features

1988 ◽  
Vol 42 (2) ◽  
pp. 336-341 ◽  
Author(s):  
Colleen A. McCoy ◽  
James A. De Haseth
Keyword(s):  
Phase Error ◽  
Absorption Spectrometry ◽  
Phase Correction ◽  
Phase Curve ◽  
Phase Retardation ◽  
Normal Absorption ◽  
Ft Ir ◽  
Arctangent Function ◽  
Circular Dichroic ◽  
Zero Phase

Several sources of phase-correction-induced spectral anomalies in FT-IR vibrational circular dichroism (VCD) spectra have been investigated. Misidentification of the zero-phase retardation position in dichroic interferograms that exhibit no optical or electronic bias can produce spectral errors. Production of such errors is from the introduction of linear phase error into the phase curve. When the zero-phase retardation position is correctly identified, other spectral anomalies, such as “reflected peaks,” can appear in VCD spectra. These peaks are readily observed in quarterwave plate reference spectra. The anomalies are directly correlated to the arctangent function used to define the phase curve and result only from the nature of the VCD signal. VCD spectra can exhibit negative, as well as positive, peaks; consequently the phase correction must be designed to accommodate negative features. Both Mertz and Forman phase-correction algorithms have been modified to correct the phase of VCD interferograms without error. Such corrections are not necessary, or even desirable, for normal absorption spectrometry.

Tracking Control of Non-Minimum Phase Systems Using Filtered Basis Functions: A NURBS-Based Approach

2015 ◽  
Author(s):  
Molong Duan ◽  
Keval S. Ramani ◽  
Chinedum E. Okwudire
Keyword(s):  
Tracking Control ◽  
Phase Error ◽  
Approximate Model ◽  
Basis Functions ◽  
Minimum Phase ◽  
Tracking Errors ◽  
Model Inversion ◽  
B Spline ◽  
Phase Systems ◽  
Zero Phase

This paper proposes an approach for minimizing tracking errors in systems with non-minimum phase (NMP) zeros by using filtered basis functions. The output of the tracking controller is represented as a linear combination of basis functions having unknown coefficients. The basis functions are forward filtered using the dynamics of the NMP system and their coefficients selected to minimize the errors in tracking a given trajectory. The control designer is free to choose any suitable set of basis functions but, in this paper, a set of basis functions derived from the widely-used non uniform rational B-spline (NURBS) curve is employed. Analyses and illustrative examples are presented to demonstrate the effectiveness of the proposed approach in comparison to popular approximate model inversion methods like zero phase error tracking control.

scholarly journals Preparation of a New Cd(II)-Imprinted Polymer and Its Application to Preconcentration and Determination of Cd(II) Ion from Aqueous Solution by SPE-FAAS

2019 ◽  
Vol 19 (1) ◽  
pp. 97
Author(s):  
Teguh Wirawan ◽  
Ganden Supriyanto ◽  
Agoes Soegianto
Keyword(s):  
Nitric Acid ◽  
Loading Rate ◽  
Solid Phase ◽  
Absorption Spectrometry ◽  
Imprinted Polymer ◽  
Flame Atomic Absorption ◽  
Ion Imprinted ◽  
Ft Ir ◽  
Polymerization Method

A novel ion Imprinted polymer (IIP) material with 8-hydroxyquinoline (8HQ) (the complexing ligands), methacrylic acid (MAA) (the monomers), ethylene glycol dimethacrylate (EGDMA) (the crosslinker agent), benzoyl peroxide (the initiator), and ethanol-acetonitrile (2:1) (the porogen) as adsorbent for the determination of cadmium by solid phase extraction–flame atomic absorption spectrometry (SPE-FAAS) has been synthesized. Synthesis of IIP was done by precipitation polymerization method. The imprinted Cd(II) ions were removed by leaching method using 1 mol L-1 nitric acid. The IIP was characterized by fourier transform infra-red (FT-IR) spectroscopy and scanning electron microscopy (SEM) to ensure successful synthesis of IIP. The experimental parameters for SPE extraction, such as pH of the sample, loading rate, and elution rate, have been optimized. The optimum pH for quantitative Cd(II) retention was 6, and the elution was completed with 2 mL of 1.0 mol L-1 nitric acid. The optimum loading rate was 0.5 mL min-1. Under optimum conditions, the proposed method with theoretical enrichment factor 50 times has a detection limit of 0.5 µg L-1 and the recovery of 97.75%.

Adaptive Zero-Phase Error-Tracking Controllers with Advance Learning

2004 ◽  
Vol 32 (2) ◽  
Author(s):  
M.M. Mustafa ◽  
N.R. Yaacob ◽  
N.A. Nik Mohamed
Keyword(s):  
Phase Error ◽  
Tracking Controllers ◽  
Zero Phase

Polarization Modulation Fourier Transform Infrared Ellipsometry of Thin Polymer Films

1986 ◽  
Vol 40 (4) ◽  
pp. 498-503 ◽  
Author(s):  
R. T. Graf ◽  
F. Eng ◽  
J. L. Koenig ◽  
H. Ishida
Keyword(s):  
Optical Constants ◽  
Relative Phase ◽  
Polarization Modulation ◽  
Thin Polymer Films ◽  
Phase Retardation ◽  
Photoelastic Modulator ◽  
Infrared Ellipsometry ◽  
Thin Polymer ◽  
Gold Substrates ◽  
Ft Ir

Polarization modulation infrared ellipsometric spectra were collected on an FT-IR spectrometer, with the use of two linear polarizers and a photoelastic modulator. Samples consisted of thin poly(vinyl acetate) and poly(methyl methacrylate) films on gold substrates. The relative phase retardation (delta) and relative amplitude (psi) were derived from these measurements. These spectra were superior to those from static infrared ellipsometry measurements on the same samples. The thickness and optical constants of the films were calculated from the ellipsometric measurements and compared with reference optical constant spectra.

Predictive deconvolution and the zero‐phase source

Geophysics ◽  
1984 ◽  
Vol 49 (4) ◽  
pp. 379-397 ◽  
Author(s):  
Bruce Gibson ◽  
Ken Larner
Keyword(s):  
White Noise ◽  
Field Data ◽  
Synthetic Data ◽  
Phase Correction ◽  
Phase Spectrum ◽  
Signal Spectrum ◽  
Minimum Phase ◽  
Predictive Deconvolution ◽  
Different Levels ◽  
Zero Phase

Predictive deconvolution is commonly applied to seismic data generated with a Vibroseisr® source. Unfortunately, when this process invokes a minimum‐phase assumption, the phase of the resulting trace will not be correct. Nonetheless, spiking deconvolution is an attractive process because it restores attenuated higher frequencies, thus increasing resolution. For detailed stratigraphic analyses, however, it is desirable that the phase of the data be treated properly as well. The most common solution is to apply a phase‐shifting filter that corrects for errors attributable to a zero‐phase source. The phase correction is given by the minimum‐phase spectrum of the correlated Vibroseis wavelet. Because no minimum‐phase spectrum truly exists for this bandlimited wavelet, white noise is added to its amplitude spectrum in order to design the phase‐correction filter. Different levels of white noise, however, produce markedly different results when field data sections are filtered. A simple argument suggests that the amount of white noise used should match that added in designing the (minimum‐phase) spiking deconvolution operator. This choice, however, also produces inconsistent results; field data again show that the phase treatment is sensitive to the amount of added white noise. Synthetic data tests show that the standard phase‐correction procedure breaks down when earth attenuation is severe. Deterministically reducing the earth‐filter effects before deconvolution improved the resulting phase treatment for the synthetic data. After application of the inverse attenuation filter to the field data, however, phase differences again remain for different levels of added white noise. These inconsistencies are attributable to the phase action of spiking deconvolution. This action is dependent upon the shape of the signal spectrum as well as the spectral shape and level of contaminating noise. Thus, in practice the proper treatment of phase in data-dependent processing requires extensive knowledge of the spectral characteristics of both signal and noise. With such knowledge, one could apply deterministic techniques that either eliminate the need for statistical deconvolution or condition the data so as to satisfy better the statistical model assumed in data‐dependent processing.

Automatic phase correction of common‐midpoint stacked data

Geophysics ◽  
1987 ◽  
Vol 52 (1) ◽  
pp. 51-59 ◽  
Author(s):  
S. Levy ◽  
D. W. Oldenburg
Keyword(s):  
Phase Correction ◽  
Well Logs ◽  
Seismic Section ◽  
Measured Velocity ◽  
Residual Phase ◽  
Automatic Phase ◽  
Frequency Independent ◽  
Independent Constant ◽  
Non Gaussian ◽  
Zero Phase

The residual wavelet on a processed seismic section is often not zero phase despite all efforts to make it so. In this paper we adopt the convolutional model for the processed seismogram, assume that the residual phase shift can be approximated by a frequency‐independent constant, and use the varimax norm to generate an algorithm to estimate the residual phase directly. Application of our algorithm to reflectivities from well logs suggests that it should work in the majority of cases so long as the reflectivity is non‐Gaussian. An application of our algorithm to stacked data enhances the interpretability of the seismic section and leads to an improved match between the recovered relative acoustic impedance and a measured velocity log.

scholarly journals Determination of gold, palladium and copper by flame atomic absorption spectrometry after preconcentration on silica gel modified with 3-(2-aminoethylamino)propyl group

2005 ◽  
Vol 3 (2) ◽  
pp. 252-262 ◽  
Author(s):  
Mustafa Imamoglu ◽  
Ali Aydin ◽  
Mustafa Dundar
Keyword(s):  
Silica Gel ◽  
Volume Flow Rate ◽  
Absorption Spectrometry ◽  
Rate Matrix ◽  
Modified Silica ◽  
Modified Silica Gel ◽  
Flame Atomic Absorption ◽  
Ft Ir ◽  
Preconcentration Method

AbstractA preconcentration method of gold, palladium and copper based on the sorption of Au (III), Pd (II) and Cu (II) ions on a column packed with 3-(2-aminoethylamino)propyl bonded silica gel is described. The modified silica gel was synthesized and characterized by FT-IR and C, H, N elemental analysis. At column preconcentration, the effects of parameters such as pH, volume, flow rate, matrix constituents of solutions and type of eluent on preconcentration of gold, palladium and copper were studied. The recoveries of Au (III), Pd (II) and Cu (II) were 98.93±0.51, 98.81±0.36 and 99.21±0.42 % at 95 % confidence level, respectively. The detection limits (δ) of the elements were 0.032, 0.016 and 0.012 μg ml−1, respectively. The preconcentration method was applied for determination of gold and palladium in certified reference material SARM 7B and copper in river and synthetic seawater by FAAS. Gold, palladium and copper were determined with relative error lower than 10 %.

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