Application of FT-IR Step-Scan Photoacoustic Phase Modulation Methods to Keratin Fibers

1995 ◽  
Vol 49 (3) ◽  
pp. 361-366 ◽  
Author(s):  
Lucia E. Jurdana ◽  
Kenneth P. Ghiggino ◽  
Ian H. Leaver ◽  
Peter Cole-Clarke
Keyword(s):  
Phase Modulation ◽  
Depth Profiling ◽  
Protein Composition ◽  
Modulation Method ◽  
Ft Ir ◽  
Keratin Fibers ◽  
Saturation Effects ◽  
Modulation Methods ◽  
Lock In ◽  
Optical Velocity

Step-scan FT-IR/PAS is shown to be a powerful tool for the nondestructive analysis of keratin fibers. Depth profiling studies were performed either by varying the optical velocity of the interferometer (scanning FT-IR/PAS depth profiling) or by a phase modulation method, utilizing a lock-in amplifier to separate the surface and bulk components of the signal phase. Both methods were shown to be capable of distinguishing spectroscopically between the cuticle and cortex of wool and hair fibers, the different spectral features being consistent with the differences in protein composition between these components. Phase-modulated spectra exhibited improved signal-to-noise ratios, with relatively little interference from saturation effects, compared with scanning FT-IR/PAS depth profile spectra.

scholarly journals Experimental Study of a Signal Modulation Method to Improve eLORAN Data Channel Communications

Sensors ◽  
2020 ◽  
Vol 20 (22) ◽  
pp. 6504
Author(s):  
Chaozhong Yang ◽  
Yulin Wang ◽  
Shifeng Li ◽  
Wenhe Yan
Keyword(s):  
Phase Modulation ◽  
Service System ◽  
Modulation Method ◽  
Pulse Modulation ◽  
Digital Modulation ◽  
Typical Application ◽  
Time Service ◽  
Data Channel ◽  
Modulation Coding ◽  
Modulation Methods

There are mainly two types of data modulation methods used for enhanced LOng-RAnge Navigation (eLORAN) systems: pulse position modulation (PPM) and supernumerary interpulse modulation (SIM). The typical application for PPM is tri-state PPM (3S-PPM), also known as Eurofix. The typical application for SIM is ninth pulse modulation. Both of these methods are phase modulation methods. Phase modulation coding, a very mature technology, is used at present. To achieve a better demodulation success rate of eLORAN digital modulation signals at longer distances, a method of using the transmitting station duplex mode to transmit a digital modulation pulse group after LORAN-C transmitting a pulse group is proposed to realize modulation pulse on–off modulation. In this method, a broadcasting experiment was performed on the BPL (The call sign of eLORAN time service system in China) broadcaster station. After monitoring, a good receiving demodulation effect was initially obtained.

Depth Profile Analysis of Keratin Fibers by FT-IR Photoacoustic Spectroscopy

1994 ◽  
Vol 48 (1) ◽  
pp. 44-49 ◽  
Author(s):  
Lucia E. Jurdana ◽  
Kenneth P. Ghiggino ◽  
Ian H. Leaver ◽  
Colin G. Barraclough ◽  
Peter Cole-Clarke
Keyword(s):  
Photoacoustic Spectroscopy ◽  
Profile Analysis ◽  
Depth Profiling ◽  
Fiber Surface ◽  
Depth Resolution ◽  
Scanning Velocity ◽  
Optical Scanning ◽  
Ft Ir ◽  
Infrared Photoacoustic Spectroscopy ◽  
Keratin Fibers

The depth profiling capability of Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) has been used to distinguish spectroscopically between the surface layer (cuticle) and the interior (cortex) of intact keratin fibers. The thermal diffusion lengths of wool and hair fibers, calculated as a function of the wavenumber and optical scanning velocity of the interferometer, indicate a depth resolution of the order of a micrometer. Shifts in the amide I and II bands to lower wavenumbers were observed with increasing velocity of the interferometer, consistent with differences in protein structure between the bulk and surface regions of the fiber. On the basis of these spectral changes, the location of the cuticle/cortex interface below the fiber surface can be determined.

Overcoming of a Resonance Stall and the Minimization of Amplitudes in the Transient Resonance of a Vibratory Machine by the Phase Modulation Method

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
J. Michalczyk ◽  
Ł. Bednarski
Keyword(s):  
Angular Velocity ◽  
General Model ◽  
Phase Modulation ◽  
Modulation Method ◽  
Practical Implementation ◽  
Control Value ◽  
Unbalanced Rotor ◽  
Transient Resonance ◽  
Modulation Methods ◽  
The Impact

The present paper elucidates the difficulties faced in the practical implementation of phase modulation methods in the form that was presented by Wang et al. and in the actual systems where the motor driving moment is the control value. A more general model, which takes into consideration the impact of machine vibrations on the rotor angular velocity, was developed. The modification of the phase modulation method is also proposed. The usefulness of such an approach for shaping the transient resonance of the machines with an unbalanced rotor is proven by means of a simulation and an experiment.

Time-Resolved Impulse Photoacoustic Measurements by Step-Scan FT-IR Spectrometry

1996 ◽  
Vol 50 (7) ◽  
pp. 939-947 ◽  
Author(s):  
Boiana O. Budevska ◽  
Christopher J. Manning
Keyword(s):  
Phase Modulation ◽  
Depth Profiling ◽  
Photoacoustic Signal ◽  
Time Dependent ◽  
Solid Samples ◽  
Time Resolved ◽  
Ir Spectrometry ◽  
Photoacoustic Spectra ◽  
Interferometric Phase ◽  
Ft Ir

An impulse/response approach for measuring photoacoustic spectra is described. Instead of the usual modulation from either a chopper or an interferometric phase modulation, a radiation pulse is used to generate the photoacoustic (PA) signal at each step of a step-scan FT-IR spectrometer. The signal from the PA cell is recorded as a time-resolved sequence. The time-dependent photoacoustic signal reveals depth-profiling information for solid samples. Examples of time-resolved impulse photoacoustic spectra (TRIPAS) of gas and solid samples are presented.

scholarly journals Quantitative Depth Profiling of Layered Samples Using Phase-Modulation FT-IR Photoacoustic Spectroscopy

1996 ◽  
Vol 50 (10) ◽  
pp. 1258-1263 ◽  
Author(s):  
Roger W. Jones ◽  
John F. McClelland
Keyword(s):  
Layer Thickness ◽  
Phase Modulation ◽  
Surface Film ◽  
Depth Profiling ◽  
Single Pair ◽  
Rapid Scan ◽  
Thin Polymer ◽  
Ft Ir ◽  
Phase Data ◽  
Ft Ir Spectroscopy

In phase-modulation FT-IR spectroscopy, all wavelengths in a spectrum are modulated at the same frequency and in phase. This factor makes the use of photoacoustic phase data for depth profiling samples much easier in phase modulation than in rapid scan. A method to quantitatively measure layer thickness by using the phase of a substrate spectrum peak is demonstrated with a series of samples consisting of thin polymer Alms on substrates. Additions to the basic method are demonstrated that extend its application to cases where the substrate peak is overlapped by a spectrum peak of the surface film. A linear relationship between phase angle and layer thickness extending to thicknesses greater than twice the thermal diffusion length is demonstrated. Representations of phase modulation data as a family of angle-specific spectra, as magnitude vs. phase curves, and as a power spectrum and phase spectrum pair, each of which is useful for different aspects of depth profiling, are discussed. Calculating these representations from a single pair of orthogonal interferograms is described.

Step-Scanning Interferometer with Digital Signal Processing

1993 ◽  
Vol 47 (9) ◽  
pp. 1345-1349 ◽  
Author(s):  
Christopher J. Manning ◽  
Peter R. Griffiths
Keyword(s):  
Signal Processing ◽  
Digital Signal Processing ◽  
Digital Signal Processor ◽  
Modulation Frequency ◽  
Depth Profiling ◽  
Digital Signal ◽  
Scanning Interferometer ◽  
Ft Ir ◽  
Lock In ◽  
Signal Processor

A novel step-scan FT-IR spectrometer incorporating a digital signal processor for demodulation of the detector signal is described. The potential advantages of this method of signal processing are discussed and illustrated. The instrument is based on a commercial cube-corner interferometer which has been modified by replacement of the drive motor with a stepper motor-micrometer and piezoelectric transducer combination. The interferometer retardation is feedback controlled by a 486–50 personal computer, which also controls the digital signal processor and collects spectral data. More than one phase modulation frequency can be imposed simultaneously, allowing for a multiplex advantage in photoacoustic depth profiling. Digital signal processing allows for simultaneous demodulation of multiple frequencies which would normally require several lock-in amplifiers. Data that illustrate the feasibility of these concepts are presented. The suitability of this instrument for double-modulation step-scan FT-IR measurements such as polymer stretching and electrochemically modulated step-scan FT-IR is also discussed.

scholarly journals Application of Ultra Narrow Band Modulation in Enhanced Loran System

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4347
Author(s):  
Boyun Lyu ◽  
Yu Hua ◽  
Jiangbin Yuan ◽  
Shifeng Li
Keyword(s):  
Narrow Band ◽  
Data Rate ◽  
Modulation Method ◽  
Phase Shift Keying ◽  
Spectrum Utilization ◽  
Frequency Domains ◽  
Shift Keying ◽  
Modulation Methods ◽  
Binary Phase Shift Keying ◽  
Signal Time

The Enhanced Loran (eLoran) system is valued for its important role in the positioning, navigation, and timing fields; however, with its current modulation methods, low data rate restricts its development. Ultra narrow band (UNB) modulation is a modulation method with extremely high spectrum utilization. If UNB modulation can be applied to the eLoran system, it will be very helpful. The extended binary phase shift keying modulation in UNB modulation is selected for a detailed study, parameters and application model are designed according to its unique characteristics of signal time and frequency domains, and it is verified through simulation that the application of this modulation not only meets the design constraints of the eLoran system but also does not affect the reception of the respective signals of both parties. Several feasible schemes are compared, analyzed, and selected. Studies have revealed that application of UNB modulation in the eLoran system is feasible, and it will increase the data rate of the system by dozens of times.

Photoacoustic FT-IR Spectroscopy of Natural Copper Patina

1995 ◽  
Vol 49 (10) ◽  
pp. 1516-1524 ◽  
Author(s):  
Alex O. Salnick ◽  
Werner Faubel
Keyword(s):  
Depth Distribution ◽  
Depth Profiling ◽  
Beam Deflection ◽  
City Hall ◽  
Spectral Bands ◽  
Special Sample Preparation ◽  
Ft Ir ◽  
Infrared Photoacoustic Spectroscopy ◽  
Ft Ir Spectroscopy

Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) has proved to be a useful tool for nondestructive testing of copper corrosion layer (patina) formed in the atmosphere. The samples cut from a piece of the roof of the Stockholm City Hall were examined without any additional pretreatment. The components of the patina—brochantite Cu4(OH)6SO4, antlerite Cu3(OH)4SO4, and basic cupric carbonate Cu2CO3(OH)6 · H2O—as well as some other minerals were identified. The photothermal beam deflection (PBD) method was used for independent photoacoustic characterization of the samples. The depth profiling capability of FT-IR/PAS was used to determine the degree of photoacoustic saturation of the spectral bands and to evaluate the depth distribution of the main patina components. The technique thus compares favorably with more common approaches of patina examination which are more expensive and require special sample preparation.

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