The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Jingkui Zhang - One of the best experts on this subject based on the ideXlab platform.
-
concrete condition assessment using impact Echo Method and extreme learning machines
Sensors, 2016Co-Authors: Jingkui ZhangAbstract:The impact-Echo (IE) Method is a popular non-destructive testing (NDT) technique widely used for measuring the thickness of plate-like structures and for detecting certain defects inside concrete elements or structures. However, the IE Method is not effective for full condition assessment (i.e., defect detection, defect diagnosis, defect sizing and location), because the simple frequency spectrum analysis involved in the existing IE Method is not sufficient to capture the IE signal patterns associated with different conditions. In this paper, we attempt to enhance the IE technique and enable it for full condition assessment of concrete elements by introducing advanced machine learning techniques for performing comprehensive analysis and pattern recognition of IE signals. Specifically, we use wavelet decomposition for extracting signatures or features out of the raw IE signals and apply extreme learning machine, one of the recently developed machine learning techniques, as classification models for full condition assessment. To validate the capabilities of the proposed Method, we build a number of specimens with various types, sizes, and locations of defects and perform IE testing on these specimens in a lab environment. Based on analysis of the collected IE signals using the proposed machine learning based IE Method, we demonstrate that the proposed Method is effective in performing full condition assessment of concrete elements or structures.
-
concrete condition assessment using impact Echo Method and extreme learning machines
Sensors, 2016Co-Authors: Jingkui ZhangAbstract:The impact-Echo (IE) Method is a popular non-destructive testing (NDT) technique widely used for measuring the thickness of plate-like structures and for detecting certain defects inside concrete elements or structures. However, the IE Method is not effective for full condition assessment (i.e., defect detection, defect diagnosis, defect sizing and location), because the simple frequency spectrum analysis involved in the existing IE Method is not sufficient to capture the IE signal patterns associated with different conditions. In this paper, we attempt to enhance the IE technique and enable it for full condition assessment of concrete elements by introducing advanced machine learning techniques for performing comprehensive analysis and pattern recognition of IE signals. Specifically, we use wavelet decomposition for extracting signatures or features out of the raw IE signals and apply extreme learning machine, one of the recently developed machine learning techniques, as classification models for full condition assessment. To validate the capabilities of the proposed Method, we build a number of specimens with various types, sizes, and locations of defects and perform IE testing on these specimens in a lab environment. Based on analysis of the collected IE signals using the proposed machine learning based IE Method, we demonstrate that the proposed Method is effective in performing full condition assessment of concrete elements or structures.
Yoiti Suzuki - One of the best experts on this subject based on the ideXlab platform.
-
time spread Echo Method for digital audio watermarking
IEEE Transactions on Multimedia, 2005Co-Authors: Byeong-seob Ko, Ryouichi Nishimura, Yoiti SuzukiAbstract:Conventional watermarking techniques based on Echo hiding provide many benefits, but also have several disadvantages, for example, a lenient decoding process, weakness against multiple encoding attacks, etc. In this paper, to improve the weak points of conventional Echo hiding, we propose a time-spread Echo as an alternative to the single Echo in conventional Echo hiding. Spreading an Echo in the time domain is achieved by using pseudonoise (PN) sequences. By spreading the Echo, the amplitude of each Echo can be reduced, i.e., the energy of each Echo becomes small, so that the distortion induced by watermarking is imperceptible to humans while the decoding performance of the embedded watermarks is better maintained as compared with the case of conventional Echo hiding, as shown by computer simulations, in which several parameters, such as the amplitude and length of PN sequences and analysis window length, were varied. Robustness against typical signal processing was also evaluated in these simulations and showed fair performance. Results of a listening test using some pieces of music showed good imperceptibility.
-
time spread Echo Method for digital audio watermarking using pn sequences
International Conference on Acoustics Speech and Signal Processing, 2002Co-Authors: Byeong-seob Ko, Ryouichi Nishimura, Yoiti SuzukiAbstract:Conventional watermarking techniques based on Echo hiding provide many benefits, but with several weak points, for example, a lenient decoding process, weakness against multiple encoding attack, etc. In this paper, to improve the weak points of conventional Echo hiding, we propose a time-spread Echo as an alternative to the conventional Echo in the Echo hiding. Spreading an Echo is performed in the impulse response domain using PN sequences. We also evaluate the characteristics of the proposed Method as a function of two parameters: gain and length of PN sequences used in spreading an Echo. The proposed Method is expected to provide more natural and colorless sounds as well as better imperceptibility of distortion as compared with conventional Echo hiding.
Roger Pynn - One of the best experts on this subject based on the ideXlab platform.
-
a novel neutron spin Echo technique for measuring phonon linewidths using magnetic wollaston prisms
Journal of Applied Crystallography, 2014Co-Authors: Roger PynnAbstract:A new Method of implementing neutron spin Echo measurement of phonon linewidths on a triple-axis neutron spectrometer is introduced, based on recently developed superconducting magnetic Wollaston prisms. Each arm of the spectrometer is composed of two Wollaston prisms with a rectangular field region between them. By introducing triangular and rectangular field regions, loci of constant spin Echo phase can be manipulated easily to achieve the so-called phonon focusing condition. Unlike the neutron resonance spin Echo Method, which is tuned by physically tilting the field boundaries, the new device can be tuned electromagnetically to achieve the phonon focusing condition. By adjusting the field configurations, the linewidths of phonon excitations with high energy and large group velocity can be measured. By employing superconducting films to define the various field regions, high neutron transmission and good neutron polarization efficiency can be obtained.
-
enhancing the resolution and intensity of neutron scattering experiments using neutron spin Echo
International Symposium on Optical Science and Technology, 2002Co-Authors: M R Fitzsimmons, H Fritzsche, J Major, Roger Pynn, Theo M RekveldtAbstract:We discuss a Method, based on the neutron spin Echo technique, which can be used to enhance a variety of neutron scattering experiments. In the Method, precession of the neutron's spin in a magnetic field is used to code a particular component of the neutron's incident or scattered wavevector. The Method allows good resolution to be obtained along any chosen direction in wavevector-and-energy-transfer (Q,E) space and is independent of other resolution elements such as collimators or monochromators. Such components can thus be chosen to maximize signal intensity. The equipment we describe uses thin, magnetic films deposited on silicon substrates to manipulate neutron spins in the manner required to implement the spin Echo Method. These films and their mounts are inexpensive, easy to build and adjust, and can be added as a "bolt-on" option to any constant-wavelength neutron spectrometer that already provides polarized neutrons. Resolutions comparable with the best achievable with tight collimation or monochromatization should be easily attainable. The gains in intensity achievable for reflectometry and SANS are discussed.
Shui Yu - One of the best experts on this subject based on the ideXlab platform.
-
A dual-channel time-spread Echo Method for audio watermarking
IEEE Transactions on Information Forensics and Security, 2012Co-Authors: Y Xiang, Iynkaran Natgunanathan, Dezhong Peng, W Zhou, Shui YuAbstract:This work proposes a novel dual-channel time-spread Echo Method for audio watermarking, aiming to improve robustness and perceptual quality. At the embedding stage, the host audio signal is divided into two subsignals, which are considered to be signals obtained from two virtual audio channels. The watermarks are implanted into the two subsignals simultaneously. Then the subsignals embedded with watermarks are combined to form the watermarked signal. At the decoding stage, the watermarked signal is split up into two watermarked subsignals. The similarity of the cepstra corresponding to the watermarked subsignals is exploited to extract the embedded watermarks. Moreover, if a properly designed colored pseudonoise sequence is used, the large peaks of its auto-correlation function can be utilized to further enhance the performance of watermark extraction. Compared with the existing time-spread Echo-based schemes, the proposed Method is more robust to attacks and has higher imperceptibility. The effectiveness of our Method is demonstrated by simulation results.
Geir Humborstad Sørland - One of the best experts on this subject based on the ideXlab platform.
-
A Pulsed Field Gradient Spin-Echo Method for Diffusion Measurements in the Presence of Internal Gradients.
Journal of Magnetic Resonance, 1999Co-Authors: Geir Humborstad Sørland, Dagfinn W. Aksnes, Lars GjerdåkerAbstract:Abstract Over the past decade several pulsed field gradient stimulated-Echo Methods have been presented for diffusion measurements in heterogeneous media. These Methods have reduced or eliminated the coupling between the applied magnetic field gradient and a constant internal magnetic field gradient caused by susceptibility changes throughout the sample. For many research purposes thez-storage delay between the second and third π/2 RF pulse has been included in order to increase the decay of the Echo attenuation to an appropriate level and to increase the signal-to-noise ratio by avoidingT2relaxation of the magnetization in parts of the pulse sequence. For these reasons a stimulated-Echo Method has been applied instead of a spin-Echo Method. When studying systems where it is necessary to keep the duration of the pulse sequence at a minimum, and one is not dependent on usingz-storage time to increase the Echo attenuation or to study diffusion as a function of observation time, a spin-Echo Method should be chosen. Here we propose a bipolar pulsed field gradient spin-Echo Method which is well suited to this purpose, and preliminary diffusion measurements are presented as illustration.
-
a stimulated Echo Method for diffusion measurements in heterogeneous media using pulsed field gradients
Journal of Magnetic Resonance, 1997Co-Authors: Geir Humborstad Sørland, Bjorn Hafskjold, Oddvin HerstadAbstract:Abstract The pulsed-field-gradient stimulated-Echo Method is a well-established technique for studying molecular motion without disturbing the system under investigation. In porous media, the effects from internal magnetic field gradients make it necessary to perform compensatory sequences. Short relaxation times make it necessary to use as short pulse a sequence as possible. Here a pulse sequence which gives reliable diffusion measurements without the need for orthogonal spoiler gradients is presented, and the number of π/2 and π pulses is kept at a minimum. Experimental verification for the removal of unwanted Echoes using the proposed PFGSTE sequence is provided, and preliminary diffusion measurements for ethane in a saturated H-ZSM5 zeolite are presented.
