Quantitative Depth Profiling of Biporous Nickel Electrodes by Frequency-Domain Laser-Induced Photoacoustic Spectroscopy

1985 ◽  
Vol 39 (3) ◽  
pp. 473-480 ◽  
Author(s):  
Andreas Mandelis ◽  
John D. Lymer
Keyword(s):  
Frequency Domain ◽  
Photoacoustic Spectroscopy ◽  
Composite Layer ◽  
Depth Profiling ◽  
Continuous System ◽  
Quantitative Information ◽  
Analytical Technique ◽  
Nickel Electrodes ◽  
Exciting Beam ◽  
Energy Conversion Devices

Frequency-domain Photoacoustic Spectroscopy (PAS) was used with a He-Ne laser exciting beam to probe commercially available, powdered and pressed nickel electrodes with dual-porosity profiles. The frequency response of the electrodes was shown to be capable of providing quantitative information about the thermal conductivity and diffusivity of each of the two porous layers, provided the depth of the porosity junction in the electrode bulk is known. The reasonable agreement of the experimental data with a one-dimensional mathematical model of the photoacoustic response from a two-layer, photoacoustically saturated, continuous system indicates that powdered and pressed nickel electrodes behave photoacoustically approximately like a simple continuous composite-layer solid. This conclusion, together with experimental PAS results from uniporous electrodes, emphasizes the high potential of photoacoustic spectroscopy as a nondestructive, depth profiling, analytical technique for the determination of complex porosity profiles in electrodes manufactured for use in electrochemical energy conversion devices, such as fuel cells.

CHARACTERIZATION OF NUCLEAR IMAGES BASED ON ANALYSIS OF FRACTIONAL SUMMATION SYSTEMS

Fractals ◽  
2004 ◽  
Vol 12 (02) ◽  
pp. 157-169 ◽  
Author(s):  
HAI-SHAN WU ◽  
ANDREW J. EINSTEIN ◽  
LIANE DELIGDISCH ◽  
TAMARA KALIR ◽  
JOAN GIL
Keyword(s):  
White Noise ◽  
Frequency Domain ◽  
Discrete System ◽  
Fractional Integral ◽  
Continuous System ◽  
Time Range ◽  
System Function ◽  
Autocovariance Function ◽  
Frequency Domain Methods

While frequency-based methods for the characterization of fractals are popular and effective in many applications, they have limitations when applied to irregularly shaped images, such as nuclear images. The irregularity renders texture characterization by frequency domain methods, based upon Fourier transform, problematic. To address this situation, this paper presents an algorithm based upon the signal analysis in the spatial domain. An autocovariance function can be estimated regardless of the shape and size of regions where the image is defined. As in the continuous fractional Brownian motion (FBM) that results from inputting white noise into a specific fractional integral system, a discrete FBM can be related to white noise by a specific fractional summation system (FSS) that is linear, causal and shift-invariant. Although the method of direct sampling is not valid for converting a continuous fractional integral to a discrete fractional summation, discrete fractional summations similar to the sampled system functions can be obtained through an iterative process. While the continuous system function of a fractional integral is linear in the frequency domain when plotted in log-log scales, unfortunately, it is not true for the comparable discrete system function. The discrete system function is actually approximately linear in the log-log scales over a very limited range. The slope of the straight line that approximates the function curve in the mean-square-error (MSE) sense in a specific time range provides a description of the autocovariance function that reveals the statistical relations among the local textures. Applications to characterization of ovary nuclear images in groups of normal, atypical and cancer cases are studied and presented.

Depth Profiling by FT-IR Photoacoustic Spectroscopy

1997 ◽  
pp. 613-614
Author(s):  
John F. McClelland ◽  
Roger W. Jones ◽  
Stanley J. Bajic ◽  
Joan F. Power
Keyword(s):  
Photoacoustic Spectroscopy ◽  
Depth Profiling ◽  
Ft Ir

Depth profiling of clay–xanthan complexes using step-scan mid-infrared photoacoustic spectroscopy

2010 ◽  
Vol 10 (5) ◽  
pp. 855-862 ◽  
Author(s):  
Changwen Du ◽  
Guiqin Zhou ◽  
Huoyan Wang ◽  
Xiaoqin Chen ◽  
Jianmin Zhou
Keyword(s):  
Photoacoustic Spectroscopy ◽  
Depth Profiling ◽  
Mid Infrared ◽  
Infrared Photoacoustic Spectroscopy

Application of photoacoustics to biology: some specific systems and methods

1986 ◽  
Vol 64 (9) ◽  
pp. 1132-1135 ◽  
Author(s):  
D. Balasubramanian ◽  
Ch. Mohan Rao
Keyword(s):  
Fourier Transform ◽  
Photoacoustic Spectroscopy ◽  
Biological Systems ◽  
Depth Profiling ◽  
Photoacoustic Signal ◽  
Mirage Effect ◽  
Photoacoustic Spectra ◽  
New Methods

A recent review of applications of photoacoustic spectroscopy to biological systems is presented. Examples of chromophore studies by photoacoustic spectroscopy show that a good correlation is possible between their presence or interactions and the photoacoustic spectra. Emphasis is placed on new interpretations of the photoacoustic signal as well as new methods such as depth profiling, the mirage effect, and Fourier-transform photoacoustic spectroscopy.

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