The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Baile Zhang - One of the best experts on this subject based on the ideXlab platform.
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tunable band notched line defect Waveguide in a Surface Wave photonic crystal
arXiv: Optics, 2016Co-Authors: Zhen Gao, Fei Gao, Youming Zhang, Baile ZhangAbstract:We propose and experimentally demonstrate a tunable band-notched line-defect Waveguide in a Surface-Wave photonic crystal, which consists of a straight line-defect Waveguide and side-coupled defect cavities. A tunable narrow stopband can be observed in the broadband transmission spectra. We also demonstrate that both the filtering levels and filtering frequencies of the band-notched line-defect Waveguide can be conveniently tuned through changing the total number and the pillar height of the side-coupled defect cavities. The band-notch function is based on the idea that the propagating Surface modes with the resonance frequencies of the side-coupled defect cavities will be tightly localized around the defect sites, being filtered from the Waveguide output. Transmission spectra measurements and direct near-field profiles imaging are performed at microWave frequencies to verify our idea and design. These results may enable new band-notched devices design and provide routes for the realization of tunable Surface-Wave filters on a single metal Surface.
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guiding bending and splitting of coupled defect Surface modes in a Surface Wave photonic crystal
Applied Physics Letters, 2016Co-Authors: Baile ZhangAbstract:We experimentally demonstrate a type of Waveguiding mechanism for coupled Surface-Wave defect modes in a Surface-Wave photonic crystal. Unlike conventional spoof Surface plasmon Waveguides, Waveguiding of coupled Surface-Wave defect modes is achieved through weak coupling between tightly localized defect cavities in an otherwise gapped Surface-Wave photonic crystal, as a classical Wave analogue of tight-binding electronic Wavefunctions in solid state lattices. Wave patterns associated with the high transmission of coupled defect Surface modes are directly mapped with a near-field microWave scanning probe for various structures including a straight Waveguide, a sharp corner, and a T-shaped splitter. These results may find use in the design of integrated Surface-Wave devices with suppressed crosstalk.
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guiding bending and splitting of coupled defect Surface modes in a Surface Wave photonic crystal
arXiv: Optics, 2016Co-Authors: Zhen Gao, Fei Gao, Baile ZhangAbstract:We experimentally demonstrate a type of Waveguiding mechanism for coupled Surface-Wave defect modes in a Surface-Wave photonic crystal. Unlike conventional spoof Surface plasmon Waveguides, Waveguiding of coupled Surface-Wave defect modes is achieved through weak coupling between tightly localized defect cavities in an otherwise gapped Surface-Wave photonic crystal, as a classical Wave analogue of tight-binding electronic Wavefunctions in solid state lattices.
Xiaoming Zhang - One of the best experts on this subject based on the ideXlab platform.
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an ultrasound Surface Wave elastography technique for non invasive measurement of scar tissue
Journal of the Acoustical Society of America, 2019Co-Authors: Boran Zhou, Saranya P Wyles, Alexander Meves, Steven L Moran, Xiaoming ZhangAbstract:Hypertrophic scars and keloids are characterized by excessive fibrosis and can be functionally problematic. Indeed, hypertrophic scarring is characterized by wide, raised scars that remain within the original borders of injury and have a rapid growth phase. There is a need for quantitative scar measurement modalities to effectively evaluate and monitor treatments. We aim to assess the role of the non-invasive scar-measuring device, ultrasound Surface Wave elastography (USWE), in accurately evaluating scar metrics. Two sites of breast tissue were tested control and scar portions. In USWE, a small, local, and 0.1-s harmonic vibration at three excitation frequencies (100, 150, and 200 Hz) was generated on these sites, and the resulting Surface Wave speed was measured via an ultrasound probe with a central frequency of 6.4 MHz. There was a statistically significant difference in the Wave speed at three frequencies of the scar portion between prior and after treatment, suggesting that the scar portion was softener after treatment. USWE provides an objective assessment of the reaction of the scar to injury and treatment response.Hypertrophic scars and keloids are characterized by excessive fibrosis and can be functionally problematic. Indeed, hypertrophic scarring is characterized by wide, raised scars that remain within the original borders of injury and have a rapid growth phase. There is a need for quantitative scar measurement modalities to effectively evaluate and monitor treatments. We aim to assess the role of the non-invasive scar-measuring device, ultrasound Surface Wave elastography (USWE), in accurately evaluating scar metrics. Two sites of breast tissue were tested control and scar portions. In USWE, a small, local, and 0.1-s harmonic vibration at three excitation frequencies (100, 150, and 200 Hz) was generated on these sites, and the resulting Surface Wave speed was measured via an ultrasound probe with a central frequency of 6.4 MHz. There was a statistically significant difference in the Wave speed at three frequencies of the scar portion between prior and after treatment, suggesting that the scar portion was soft...
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the effect of pleural fluid layers on lung Surface Wave speed measurement experimental and numerical studies on a sponge lung phantom
Journal of The Mechanical Behavior of Biomedical Materials, 2019Co-Authors: Boran Zhou, Xiaoming ZhangAbstract:Abstract Pleural effusion manifests as compression of pleural fluid on the lung parenchyma contributing to hypoxemia. Medical procedures such as drainage of plural fluid releases this compression and increases oxygenation. However, the effect of pleural effusion on the elasticity of lung parenchyma is unknown. By using lung ultrasound Surface Wave elastography (LUSWE) and finite element method (FEM), the effect of pleural effusion on the elasticity of superficial lung parenchyma in terms of Surface Wave speed measurement was evaluated in a sponge phantom study. Different thicknesses of ultrasound transmission gel used to simulated pleural fluid were inserted into a condom, which was placed between the sponge and standoff pad. A mechanical shaker was used to generate vibration on the sponge phantom at different frequencies ranging from 100 to 300 Hz while the ultrasound transducer was used to capture the motion for measurement of Surface Wave speed of the sponge. FEM was conducted based on the experimental setup and numerically assessed the influence of pleural effusion on the Surface Wave speed of the sponge. We found from FEM experiments that the influence of thickness of ultrasound transmission gel was statistically insignificant on the Surface Wave speed of the sponge at 100 and 150 Hz.
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an ultrasound Surface Wave technique for assessing skin and lung diseases
Ultrasound in Medicine and Biology, 2018Co-Authors: Xiaoming Zhang, James F Greenleaf, Boran Zhou, Sanjay Kalra, Brian J Bartholmai, Thomas OsbornAbstract:Abstract Systemic sclerosis (SSc) is a multi-organ connective tissue disease characterized by immune dysregulation and organ fibrosis. Severe organ involvement, especially of the skin and lung, is the cause of morbidity and mortality in SSc. Interstitial lung disease (ILD) includes multiple lung disorders in which the lung tissue is fibrotic and stiffened. The purpose of this study was to translate ultrasound Surface Wave elastography (USWE) for assessing patients with SSc and/or ILD via measuring Surface Wave speeds of both skin and superficial lung tissue. Forty-one patients with both SSc and ILD and 30 healthy patients were enrolled in this study. An external harmonic vibration was used to generate the Wave propagation on the skin or lung. Three excitation frequencies of 100, 150 and 200 Hz were used. An ultrasound probe was used to measure the Wave propagation in the tissue non-invasively. Surface Wave speeds were measured on the forearm and upper arm of both left and right arm, as well as the upper and lower lungs, through six intercostal spaces of patients and healthy patients. Viscoelasticity of the skin was calculated by the Wave speed dispersion with frequency using the Voigt model. The magnitudes of Surface Wave speed and viscoelasticity of patients' skin were significantly higher than those of healthy patients (p
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quantitative assessment of scleroderma by Surface Wave technique
Medical Engineering & Physics, 2011Co-Authors: Xiaoming Zhang, Thomas Osborn, Mark R Pittelkow, Bo Qiang, Randall R Kinnick, James F GreenleafAbstract:Scleroderma is a multisystem disease characterized by cutaneous and visceral fibrosis. Skin disease is both a disabling feature of scleroderma and a predictor of visceral involvement. The established method of skin assessment is the modified Rodnan skin score (MRSS) which uses semi-quantitative manual skin scoring. However, the Rodnan method is subjective. We have developed a technique and system for assessing skin health by producing and analyzing Surface Waves in the skin to determine the skin viscoelastic properties. Viscoelasticity of human skin is measured on 30 healthy volunteers and 10 scleroderma patients at six anatomic sites. A small force, monitored by a force transducer, is applied to the skin using a ball-tipped device attached to a mechanical shaker. The skin motion is measured by a scanning laser vibrometer. The Surface Wave speed is measured by the phase gradient method. The viscoelasticity is inversely estimated by the Wave speed dispersion. A typical measurement of the Surface Wave speed is 3.25±0.19 m/s on the forearm of a volunteer at 200 Hz. With the Wave speed dispersion from 100 Hz to 400 Hz, the shear elasticity μ(1) and shear viscosity μ(2) are estimated, respectively, 7.86±1.86 kPa and 5.03±0.60 Pa on the forearm. Statistical analyses suggest that there are significant differences of viscoelasticity between scleroderma patients and healthy subjects. Scleroderma can be effectively and quantitatively evaluated based on human skin viscoelasticity.
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estimation of tissue s elasticity with Surface Wave speed
Journal of the Acoustical Society of America, 2007Co-Authors: Xiaoming Zhang, James F GreenleafAbstract:The mechanical response of tissues to external forces has gained considerable interest in medical diagnosis. One approach to imaging tissue elastic properties is to apply an external force on the Surface of the body. Another approach is to generate a localized force inside the tissue with the radiation force of ultrasound. In this paper, a new method is developed to estimate tissue’s elasticity based on Surface Wave speed measurement. The theory of Surface Wave speed is developed for estimating tissue’s elasticity. Experiments are carried out on a tissue-mimicking ultrasound phantom. An amplitude modulated ultrasound signal of a few hundred hertz is used to generate a localized force in the phantom. The Surface Wave fields are measured with a laser vibrometer. It shows that the Surface Wave speed can be used for inversely estimating tissue’s elastic properties based on tissue’s Surface measurement.
Sebastiano Foti - One of the best experts on this subject based on the ideXlab platform.
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Guidelines for the good practice of Surface Wave analysis: a product of the InterPACIFIC project
Bulletin of Earthquake Engineering, 2017Co-Authors: Sebastiano Foti, Flora Garofalo, Michael Asten, Brady Cox, Cesare Comina, Fabrice Hollender, Pierre‐yves Bard, Cécile Cornou, Dario Albarello, Giuseppe Di GiulioAbstract:Surface Wave methods gained in the past decades a primary role in many seismic projects. Specifically, they are often used to retrieve a 1D shear Wave velocity model or to estimate the VS,30 at a site. The complexity of the interpretation process and the variety of possible approaches to Surface Wave analysis make it very hard to set a fixed standard to assure quality and reliability of the results. The present guidelines provide practical information on the acquisition and analysis of Surface Wave data by giving some basic principles and specific suggestions related to the most common situations. They are primarily targeted to non-expert users approaching Surface Wave testing, but can be useful to specialists in the field as a general reference. The guidelines are based on the experience gained within the InterPACIFIC project and on the expertise of the participants in acquisition and analysis of Surface Wave data.
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Surface Wave methods for near Surface site characterization
2014Co-Authors: Sebastiano Foti, Claudio StrobbiaAbstract:Overview of Surface Wave methods Seismic Waves Test methodology Historical perspective Challenges of Surface Wave methods Typical applications Advantages and limitations Linear Wave propagation in verticallyinhomogeneous continua Basic notions of Wave propagation Rayleigh Waves in homogeneous elastic half-spaces Existence of Love Waves Surface Waves in vertically inhomogeneouselastic continua Surface Waves in vertically inhomogeneous, inelastic continua Measurement of Surface Waves Seismic data acquisition The Wave field as a signal in time and space Acquisition of digital seismic signals Acquisition of Surface Waves Equipment Dispersion analysis Phase and group velocity Steady-state method Spectral analysis of Surface Waves Multi-offset phase analysis Spatial autocorrelation Transform-based methods Group velocity analysis Errors and uncertainties in dispersion analyses Attenuation analysis Attenuation of Surface Waves Univariate regression of amplitude versus offset data Transfer function technique and complex Wavenumbers Multichannel multimode complex Wavenumber estimation Other simplified approaches Uncertainty in the attenuation measurement Inversion Conceptual issues Forward modeling Surface Wave inversion by empirical methods Surface Wave inversion by analytical methods Uncertainty Case histories Comparison among processing techniques with active-source methods Comparison among inversion strategies Examples for determining Vs and Ds profiles Dealing with higher modes Surface Wave inversion of seismic reflection data Advanced Surface Wave methods Love Waves Offshore and nearshore Surface Wave testing Joint inversion with other geophysical data Passive seismic interferometry Multicomponent Surface Wave analysis, polarization studies, and horizontal-to-vertical spectral ratio References Index
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Surface Wave analysis for building near Surface velocity models established approaches and new perspectives
Geophysics, 2010Co-Authors: Laura Socco, Sebastiano Foti, Daniele BoieroAbstract:Today, Surface-Wave analysis is widely adopted for building near-Surface S-Wave velocity models. The Surface-Wave method is under continuous and rapid evolution, also thanks to the lively scientific debate among different disciplines, and interest in the technique has increased significantly during the last decade. A comprehensive review of the literature in the main scientific journals provides historical perspective, methodological issues, applications, and most-promising recent approaches. Higher modes in the inversion and retrieval of lateral variations are dealt with in great detail, and the current scientific debate on these topics is reported. A best-practices guideline is also outlined.
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non uniqueness in Surface Wave inversion and consequences on seismic site response analyses
Soil Dynamics and Earthquake Engineering, 2009Co-Authors: Sebastiano Foti, Cesare Comina, Daniele Boiero, Laura SoccoAbstract:Surface-Wave tests are based on the solution of an inverse problem for shear-Wave velocity profile identification from the experimentally measured dispersion curve. The main criticisms for these testing methodologies are related to the inverse problem solution and arise from the possible equivalence of different shear-Wave velocity profiles. In this paper, some implications of solution non-uniqueness for seismic response studies are investigated using both numerical simulations and experimental data. A Monte Carlo approach for the inversion problem has been used to obtain a set of equivalent shear-Wave velocity models. This selection is based on a statistical test which takes into account both data uncertainty and model parameterization. This set of solutions (i.e., soil profiles) is then used to evaluate the seismic response with a conventional one-dimensional analysis. It is shown that equivalent profiles with respect to Surface-Wave testing are equivalent also with respect to site amplification, thus countering the criticism related to inversion uncertainty for the engineering use of Surface-Wave tests.
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propagation of data uncertainty in Surface Wave inversion
Journal of Environmental and Engineering Geophysics, 2005Co-Authors: Carlo G Lai, Sebastiano Foti, Glenn J RixAbstract:Although in recent years Surface Wave methods have undergone significant development that has greatly enhanced their capabilities, little effort has been spent to determine the uncertainty associated with Surface Wave measurements. The objective of this study is to determine how the uncertainty of the experimental data is mapped into the uncertainty of the shear Wave velocity profile via the inversion algorithm. The methodology developed in this study for estimating the uncertainty of the shear Wave velocity profile from Surface Wave measurements is based on the assumption that the experimental data are normally distributed. The validity of this hypothesis was experimentally verified using data gathered at two sites in Italy where Surface Wave tests were performed using linear arrays of multiple receivers. The experimental dispersion curve measured at the site was subsequently inverted to obtain the expected shear Wave velocity profile together with an estimate of the associated standard deviation. The final results show that uncorrelated noise has a very little influence on multistation Surface Wave tests, confirming their robustness for applications in noisy environments.
Boran Zhou - One of the best experts on this subject based on the ideXlab platform.
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an ultrasound Surface Wave elastography technique for non invasive measurement of scar tissue
Journal of the Acoustical Society of America, 2019Co-Authors: Boran Zhou, Saranya P Wyles, Alexander Meves, Steven L Moran, Xiaoming ZhangAbstract:Hypertrophic scars and keloids are characterized by excessive fibrosis and can be functionally problematic. Indeed, hypertrophic scarring is characterized by wide, raised scars that remain within the original borders of injury and have a rapid growth phase. There is a need for quantitative scar measurement modalities to effectively evaluate and monitor treatments. We aim to assess the role of the non-invasive scar-measuring device, ultrasound Surface Wave elastography (USWE), in accurately evaluating scar metrics. Two sites of breast tissue were tested control and scar portions. In USWE, a small, local, and 0.1-s harmonic vibration at three excitation frequencies (100, 150, and 200 Hz) was generated on these sites, and the resulting Surface Wave speed was measured via an ultrasound probe with a central frequency of 6.4 MHz. There was a statistically significant difference in the Wave speed at three frequencies of the scar portion between prior and after treatment, suggesting that the scar portion was softener after treatment. USWE provides an objective assessment of the reaction of the scar to injury and treatment response.Hypertrophic scars and keloids are characterized by excessive fibrosis and can be functionally problematic. Indeed, hypertrophic scarring is characterized by wide, raised scars that remain within the original borders of injury and have a rapid growth phase. There is a need for quantitative scar measurement modalities to effectively evaluate and monitor treatments. We aim to assess the role of the non-invasive scar-measuring device, ultrasound Surface Wave elastography (USWE), in accurately evaluating scar metrics. Two sites of breast tissue were tested control and scar portions. In USWE, a small, local, and 0.1-s harmonic vibration at three excitation frequencies (100, 150, and 200 Hz) was generated on these sites, and the resulting Surface Wave speed was measured via an ultrasound probe with a central frequency of 6.4 MHz. There was a statistically significant difference in the Wave speed at three frequencies of the scar portion between prior and after treatment, suggesting that the scar portion was soft...
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the effect of pleural fluid layers on lung Surface Wave speed measurement experimental and numerical studies on a sponge lung phantom
Journal of The Mechanical Behavior of Biomedical Materials, 2019Co-Authors: Boran Zhou, Xiaoming ZhangAbstract:Abstract Pleural effusion manifests as compression of pleural fluid on the lung parenchyma contributing to hypoxemia. Medical procedures such as drainage of plural fluid releases this compression and increases oxygenation. However, the effect of pleural effusion on the elasticity of lung parenchyma is unknown. By using lung ultrasound Surface Wave elastography (LUSWE) and finite element method (FEM), the effect of pleural effusion on the elasticity of superficial lung parenchyma in terms of Surface Wave speed measurement was evaluated in a sponge phantom study. Different thicknesses of ultrasound transmission gel used to simulated pleural fluid were inserted into a condom, which was placed between the sponge and standoff pad. A mechanical shaker was used to generate vibration on the sponge phantom at different frequencies ranging from 100 to 300 Hz while the ultrasound transducer was used to capture the motion for measurement of Surface Wave speed of the sponge. FEM was conducted based on the experimental setup and numerically assessed the influence of pleural effusion on the Surface Wave speed of the sponge. We found from FEM experiments that the influence of thickness of ultrasound transmission gel was statistically insignificant on the Surface Wave speed of the sponge at 100 and 150 Hz.
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an ultrasound Surface Wave technique for assessing skin and lung diseases
Ultrasound in Medicine and Biology, 2018Co-Authors: Xiaoming Zhang, James F Greenleaf, Boran Zhou, Sanjay Kalra, Brian J Bartholmai, Thomas OsbornAbstract:Abstract Systemic sclerosis (SSc) is a multi-organ connective tissue disease characterized by immune dysregulation and organ fibrosis. Severe organ involvement, especially of the skin and lung, is the cause of morbidity and mortality in SSc. Interstitial lung disease (ILD) includes multiple lung disorders in which the lung tissue is fibrotic and stiffened. The purpose of this study was to translate ultrasound Surface Wave elastography (USWE) for assessing patients with SSc and/or ILD via measuring Surface Wave speeds of both skin and superficial lung tissue. Forty-one patients with both SSc and ILD and 30 healthy patients were enrolled in this study. An external harmonic vibration was used to generate the Wave propagation on the skin or lung. Three excitation frequencies of 100, 150 and 200 Hz were used. An ultrasound probe was used to measure the Wave propagation in the tissue non-invasively. Surface Wave speeds were measured on the forearm and upper arm of both left and right arm, as well as the upper and lower lungs, through six intercostal spaces of patients and healthy patients. Viscoelasticity of the skin was calculated by the Wave speed dispersion with frequency using the Voigt model. The magnitudes of Surface Wave speed and viscoelasticity of patients' skin were significantly higher than those of healthy patients (p
X Jian - One of the best experts on this subject based on the ideXlab platform.
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ultrasonic Surface Wave propagation and interaction with Surface defects on rail track head
Ndt & E International, 2007Co-Authors: Yichao Fan, S Dixon, R S Edwards, X JianAbstract:Abstract Electromagnetic acoustic transducers (EMATs) are non-contact ultrasonic transducers capable of generating wide band ultrasonic Surface Waves on metallic samples. A lab-based laser-EMAT system has been developed to observe the ultrasonic Surface Wave propagation and interaction with Surface breaking defects on the sample rail head Surface. A wide band EMAT generating Surface Waves with a frequency content between approximately 50 and 500 kHz is used to propagate ultrasonic Waves on the Surface of a rail head down the length of the sample. A stabilised Michelson interferometer is used to measure the out-of-plane displacement of the Surface Wave. A complete picture of the ultrasonic Surface Wave on the sample Surface over time is reconstructed using this technique, with exceptionally high spatial and temporal resolution. Despite the curvature of the rail head, the ultrasonic Surface Wave propagating down the rail is found to have similar properties to Rayleigh Waves by direct comparison to those observed on flat samples using the same technique.
