Low frequency acoustic microscopy and pattern recognition for studying damaged and anisotropic composites and material defects

1992 ◽  
Vol 11 (1) ◽  
pp. 19-28 ◽  
Author(s):  
M. A. Awal ◽  
A. Mahalanobis ◽  
T. Kundu
Keyword(s):  
Pattern Recognition ◽  
Low Frequency ◽  
Acoustic Microscopy ◽  
Material Defects

scholarly journals Damage evolution in wood – pattern recognition based on acoustic emission (AE) frequency spectra

Holzforschung ◽  
2015 ◽  
Vol 69 (3) ◽  
pp. 357-365 ◽  
Author(s):  
Franziska Baensch ◽  
Markus G.R. Sause ◽  
Andreas J. Brunner ◽  
Peter Niemz
Keyword(s):  
Pattern Recognition ◽  
Acoustic Emission ◽  
Cluster Formation ◽  
Low Frequency ◽  
Tensile Tests ◽  
Most Probable Number ◽  
Frequency Spectra ◽  
Probable Number ◽  
Ae Signal ◽  
Ae Signals

Abstract Tensile tests on miniature spruce specimens have been performed by means of acoustic emission (AE) analysis. Stress was applied perpendicular (radial direction) and parallel to the grain. Nine features were selected from the AE frequency spectra. The signals were classified by means of an unsupervised pattern recognition approach, and natural classes of AE signals were identified based on the selected features. The algorithm calculates the numerically best partition based on subset combinations of the features provided for the analysis and leads to the most significant partition including the respective feature combination and the most probable number of clusters. For both specimen types investigated, the pattern recognition technique indicates two AE signal clusters. Cluster A comprises AE signals with a relatively high share of low-frequency components, and the opposite is true for cluster B. It is hypothesized that the signature of rapid and slow crack growths might be the origin for this cluster formation.

LOW FREQUENCY ACOUSTIC RESPONSE OF SURFACE CRACKS BY ATOM FORCE ACOUSTIC MICROSCOPY

2009 ◽  
Vol 16 (03) ◽  
pp. 449-453 ◽  
Author(s):  
WEI-TAO SU ◽  
BIN LI ◽  
DING-QUAN LIU ◽  
FENG-SHAN ZHANG
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Thermal Stress ◽  
Elastic Properties ◽  
Surface Crack ◽  
Low Frequency ◽  
Acoustic Microscopy ◽  
Surface Cracks ◽  
Acoustic Response ◽  
Scanning Electron

Surface crack of CeF 3 films generated by thermal stress were characterized by scanning electron microscopy and atom force acoustic microscopy (AFAM). Low frequency (8–18 kHz) acoustic response of films and cracks was measured by AFAM. The low frequency acoustic response is similar to what had been got at several MHz or even higher frequency. It was found that surface elastic properties of CeF 3 films can be easily qualitatively measured by low frequency AFAM.

Intelligent Control Circuit Integral with Pattern Recognition Techniques for High-Pressure Sodium Lamps

2017 ◽  
Vol 26 (07) ◽  
pp. 1750108
Author(s):  
Yuzhuo Pan ◽  
Chen Lv ◽  
Shanhe Su ◽  
Jincan Chen
Keyword(s):  
Pattern Recognition ◽  
High Pressure ◽  
Intelligent Control ◽  
High Frequency ◽  
Pulse Width Modulation ◽  
Smart Cities ◽  
Control Strategies ◽  
Low Frequency ◽  
Acoustic Resonance ◽  
Working Device

The paper presents the analysis, simulation, and experimental methods to eliminate acoustic resonance in high-frequency high-pressure sodium (HPS) lamps and integrate intelligent control strategies in the working device. Based on the pulse-width modulation (PWM) output generated by the microcontroller, the acoustic resonance in the high-frequency lamp can be successfully eliminated by modulating the high-frequency driving current via a low-frequency signal. Particularly, by implementing the pattern recognition, the control system enables the lamp to have the abilities of accurate timing, gradient dimming, automatic protection, and intellisense. The proposed model will provide useful information for designing intelligent lighting system towards smart cities.

Search Time as a Function of Context Letter Frequency

Perception ◽  
1972 ◽  
Vol 1 (1) ◽  
pp. 57-71 ◽  
Author(s):  
C R Latimer
Keyword(s):  
Pattern Recognition ◽  
Reaction Time ◽  
High Frequency ◽  
Relative Frequency ◽  
Search Time ◽  
Low Frequency ◽  
Frequency Of Occurrence ◽  
Template Model ◽  
Letter Frequency ◽  
Feature Frequency

Neisser (1967) posits the operation of purely feature analytic processes in the scanning of context letters in search lists. This contention was tested by varying the relative frequency of occurrence in English of the context letters in alphanumeric search lists, while holding their feature content constant. It was hypothesized that faster search time on lists of high-frequency context letters would indicate letter-level processing. Equality of search time would indicate the purely feature-level processing required by Neisser's theory. Context letters were segregated into high- and low-frequency sets and their features defined and held constant according to two feature analyses. This yielded a 2 × 2 design with 22 subjects per condition. Attention was given to the control of feature frequency, size of the context-letter set, and approximation of English at the level of bigram, trigram, and word. Results supported a letter level or template model of processing but were shown also to be explainable in terms of some feature-testing models of pattern recognition. Apparatus which allowed for the removal of reaction time in search lists is described.

scholarly journals Micro- and nano-structural details of a spider's filter for substrate vibrations: relevance for low-frequency signal transmission

2015 ◽  
Vol 12 (104) ◽  
pp. 20141111 ◽  
Author(s):  
Maxim Erko ◽  
Osnat Younes-Metzler ◽  
Alexander Rack ◽  
Paul Zaslansky ◽  
Seth L. Young ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Signal Transmission ◽  
Three Dimensional ◽  
Low Frequency ◽  
Acoustic Microscopy ◽  
Micro Computed Tomography ◽  
Cupiennius Salei ◽  
X Ray ◽  
Wide Range ◽  
40 Hz

The metatarsal lyriform organ of the Central American wandering spider Cupiennius salei is its most sensitive vibration detector. It is able to sense a wide range of vibration stimuli over four orders of magnitude in frequency between at least as low as 0.1 Hz and several kilohertz. Transmission of the vibrations to the slit organ is controlled by a cuticular pad in front of it. While the mechanism of high-frequency stimulus transfer (above ca 40 Hz) is well understood and related to the viscoelastic properties of the pad's epicuticle, it is not yet clear how low-frequency stimuli (less than 40 Hz) are transmitted. Here, we study how the pad material affects the pad's mechanical properties and thus its role in the transfer of the stimulus, using a variety of experimental techniques, such as X-ray micro-computed tomography for three-dimensional imaging, X-ray scattering for structural analysis, and atomic force microscopy and scanning electron microscopy for surface imaging. The mechanical properties were investigated using scanning acoustic microscopy and nanoindentation. We show that large tarsal deflections cause large deformation in the distal highly hydrated part of the pad. Beyond this region, a sclerotized region serves as a supporting frame which resists the deformation and is displaced to push against the slits, with displacement values considerably scaled down to only a few micrometres. Unravelling the structural arrangement in such specialized structures may provide conceptual ideas for the design of new materials capable of controlling a technical sensor's specificity and selectivity, which is so typical of biological sensors.

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