Pub Date : 2002-10-08DOI: 10.1109/ULTSYM.2002.1193445
J. Black, R. White, J. Grate
A standing acoustic field excited by an ultrasonic flexural plate wave (FPW) device is shown to trap microspheres and cells suspended in a pressure-driven flowing liquid. Capture is achieved by counteracting the viscous drag forces on a particle with acoustic radiation pressure. The suitability of this technique for biochemical analysis is demonstrated with two experiments: (1) acoustically trapped streptavidin-coated 1 /spl mu/m microspheres conjugated to fluorescent 200 nm biotinylated microspheres; and (2) perfusion of the membrane permeant fluorescein diacetate across acoustically trapped cells. Biochemical interaction was monitored with a fluorescence microscope. Efforts to integrate acoustic traps with on-chip FPW microfluidic pumps are also described.
{"title":"Microsphere capture and perfusion in microchannels using flexural plate wave structures","authors":"J. Black, R. White, J. Grate","doi":"10.1109/ULTSYM.2002.1193445","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193445","url":null,"abstract":"A standing acoustic field excited by an ultrasonic flexural plate wave (FPW) device is shown to trap microspheres and cells suspended in a pressure-driven flowing liquid. Capture is achieved by counteracting the viscous drag forces on a particle with acoustic radiation pressure. The suitability of this technique for biochemical analysis is demonstrated with two experiments: (1) acoustically trapped streptavidin-coated 1 /spl mu/m microspheres conjugated to fluorescent 200 nm biotinylated microspheres; and (2) perfusion of the membrane permeant fluorescein diacetate across acoustically trapped cells. Biochemical interaction was monitored with a fluorescence microscope. Efforts to integrate acoustic traps with on-chip FPW microfluidic pumps are also described.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121988079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-08DOI: 10.1109/ULTSYM.2002.1192671
F. Viola, W. Walker
In the breast, prostate and other organs increased tissue stiffness is often associated with the presence of disease. While palpation remains widely used, it has limited sensitivity which is highly dependent upon the skill of the clinician. To overcome this and other limitations a variety of automated approaches have been developed in recent years. These techniques generate tissue deformation by applying acoustic radiation force internally, shear waves superficially, or axial compression. In this paper we propose an alternate approach for elasticity imaging. A shear deformation is applied to the tissue surface. Ultrasound images obtained before and after shear application are processed to yield images of shear strain. We tested this method experimentally on custom acrylamide gel phantoms using a Philips SONOS 5500 imaging system. The phantoms consisted of a 5% acrylamide background with 15% acrylamide inclusions. 50 /spl mu/m sephadex spheres were used in the background and inclusion to introduce ultrasonic scattering. 4% shear rates were generated by translating the upper surface of the 5 cm thick phantoms by 2.0 mm. The shear strains observed within the inclusions of each phantom were roughly one third those seen in the background region. As anticipated, little axial deformation was observed. Experimentally obtained shear strain images clearly delineate the inclusions with few artifacts, although some noise is visible. This noise undoubtedly arises from jitter in the lateral displacement estimates. Theoretical analysis suggests that signal decorrelation under lateral shear will be very small. This, coupled with the minimal artifacts visible in the shear strain images may make shear elastography an attractive alternative to techniques.
在乳腺、前列腺和其他器官中，组织僵硬度的增加通常与疾病的存在有关。虽然触诊仍然广泛使用，但它的灵敏度有限，这高度依赖于临床医生的技能。为了克服这个和其他限制，近年来开发了各种自动化方法。这些技术通过内部施加声辐射力、表面施加剪切波或轴向压缩来产生组织变形。在本文中，我们提出了弹性成像的另一种方法。对组织表面施加剪切变形。对剪切应用前后获得的超声图像进行处理，得到剪切应变图像。我们使用飞利浦SONOS 5500成像系统对定制丙烯酰胺凝胶模型进行了实验测试。幻影由5%丙烯酰胺背景和15%丙烯酰胺内含物组成。采用50 /spl μ m /m的葡聚糖球作为背景和夹杂物，引入超声散射。将5 cm厚的幻影上表面平移2.0 mm，产生4%的剪切速率。在每个幻影的内含物中观察到的剪切应变大约是背景区域中所见的剪切应变的三分之一。正如预期的那样，观察到很少的轴向变形。实验获得的剪切应变图像清晰地描绘了夹杂物，几乎没有伪影，尽管一些噪声是可见的。这种噪声无疑是由侧向位移估计中的抖动引起的。理论分析表明，侧向剪切作用下的信号去相关很小。这一点，加上在剪切应变图像中可见的最小伪影，可能使剪切弹性成像成为一种有吸引力的替代技术。
{"title":"Shear strain elastography","authors":"F. Viola, W. Walker","doi":"10.1109/ULTSYM.2002.1192671","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1192671","url":null,"abstract":"In the breast, prostate and other organs increased tissue stiffness is often associated with the presence of disease. While palpation remains widely used, it has limited sensitivity which is highly dependent upon the skill of the clinician. To overcome this and other limitations a variety of automated approaches have been developed in recent years. These techniques generate tissue deformation by applying acoustic radiation force internally, shear waves superficially, or axial compression. In this paper we propose an alternate approach for elasticity imaging. A shear deformation is applied to the tissue surface. Ultrasound images obtained before and after shear application are processed to yield images of shear strain. We tested this method experimentally on custom acrylamide gel phantoms using a Philips SONOS 5500 imaging system. The phantoms consisted of a 5% acrylamide background with 15% acrylamide inclusions. 50 /spl mu/m sephadex spheres were used in the background and inclusion to introduce ultrasonic scattering. 4% shear rates were generated by translating the upper surface of the 5 cm thick phantoms by 2.0 mm. The shear strains observed within the inclusions of each phantom were roughly one third those seen in the background region. As anticipated, little axial deformation was observed. Experimentally obtained shear strain images clearly delineate the inclusions with few artifacts, although some noise is visible. This noise undoubtedly arises from jitter in the lateral displacement estimates. Theoretical analysis suggests that signal decorrelation under lateral shear will be very small. This, coupled with the minimal artifacts visible in the shear strain images may make shear elastography an attractive alternative to techniques.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125840108","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-08DOI: 10.1109/ULTSYM.2002.1193487
T. Shigematsu, M.K. Kuroswa, K. Asai
A mechanical model of a surface acoustic wave (SAW) motor's stepping motions ranging under 100 nanometers was constructed. The SAW motor had a compliance structure in its movable part to utilize nanometer vibration of SAW for friction drive. The compliance, however, resulted in the two-degree-of-freedom vibration behavior of the movable part. Based on the mechanical model, the system identification was carried out by means of FFT analyses and decay fittings to experimental data. The simulation with the identified model qualitatively represented the experimental results. For more accurate simulations, additional nonlinear effects should be implied to the model.
{"title":"Stepping motion analysis of surface acoustic wave motor toward nanometer resolution positioning system","authors":"T. Shigematsu, M.K. Kuroswa, K. Asai","doi":"10.1109/ULTSYM.2002.1193487","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193487","url":null,"abstract":"A mechanical model of a surface acoustic wave (SAW) motor's stepping motions ranging under 100 nanometers was constructed. The SAW motor had a compliance structure in its movable part to utilize nanometer vibration of SAW for friction drive. The compliance, however, resulted in the two-degree-of-freedom vibration behavior of the movable part. Based on the mechanical model, the system identification was carried out by means of FFT analyses and decay fittings to experimental data. The simulation with the identified model qualitatively represented the experimental results. For more accurate simulations, additional nonlinear effects should be implied to the model.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124647887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-08DOI: 10.1109/ULTSYM.2002.1192596
S. Nikolov, J. A. Jensen, R. Dufait, Armin Schoisswohl
Current 3D real-time imaging is done either with sparse 2D arrays, or with mechanically moved phased arrays. The former results in a poor resolution and contrast due to a limited amount of elements. The latter has the disadvantage of low frame rates due to the sequential acquisition of the volume line-by-line and plane-by-plane. This paper describes an approach which combines mechanically moved phased array with synthetic transmit aperture imaging, resulting in high volume acquisition rates without a trade-off in image quality. The scan method uses a conventional fully populated 64 element phased array, which is rotated over the volume of interest. The data is acquired using coded signals and synthetic transmit aperture imaging. Only one group of elements transmits at a time. The delays are set such as to form a cylindrical wave. The back-scattered signal carries information not only from the plane located directly below the transducer, but also from neighboring planes. A complete dataset for all elements for the whole rotation is acquired and stored. The volume is then focused from this complete data set in order to obtain dynamic transmit and receive focusing in all directions.
{"title":"Three-dimensional real-time synthetic aperture imaging using a rotating phased array transducer","authors":"S. Nikolov, J. A. Jensen, R. Dufait, Armin Schoisswohl","doi":"10.1109/ULTSYM.2002.1192596","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1192596","url":null,"abstract":"Current 3D real-time imaging is done either with sparse 2D arrays, or with mechanically moved phased arrays. The former results in a poor resolution and contrast due to a limited amount of elements. The latter has the disadvantage of low frame rates due to the sequential acquisition of the volume line-by-line and plane-by-plane. This paper describes an approach which combines mechanically moved phased array with synthetic transmit aperture imaging, resulting in high volume acquisition rates without a trade-off in image quality. The scan method uses a conventional fully populated 64 element phased array, which is rotated over the volume of interest. The data is acquired using coded signals and synthetic transmit aperture imaging. Only one group of elements transmits at a time. The delays are set such as to form a cylindrical wave. The back-scattered signal carries information not only from the plane located directly below the transducer, but also from neighboring planes. A complete dataset for all elements for the whole rotation is acquired and stored. The volume is then focused from this complete data set in order to obtain dynamic transmit and receive focusing in all directions.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125014000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-08DOI: 10.1109/ULTSYM.2002.1193541
T. Fujita, K. Toda
A technique for measuring mechanical vibration displacement is proposed using a liquid-delay-line-oscillator, which is composed of two pairs of arch-shaped interdigital transducers (IDTs) on a double-layered substrate composed of a piezoelectric ceramic plate and an acrylic plate, a polymer-film diaphragm as one wall of a liquid cavity, and a water layer. The diaphragm functions as an ultrasound-beam reflector. The acoustical phase change arises corresponding to the pressure exerted on the central part of the diaphragm. The relationship between the mechanical displacement and the oscillation frequency is evaluated experimentally on the basis of the acoustical delay length linearly dependent on the thickness of the water layer. The static and dynamic displacement measurements are demonstrated. The present technique is promising for sensing sound pressure, which could be regarded as a precise and convenient method.
{"title":"A mechanical vibration sensing technique using a liquid delay line oscillator","authors":"T. Fujita, K. Toda","doi":"10.1109/ULTSYM.2002.1193541","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193541","url":null,"abstract":"A technique for measuring mechanical vibration displacement is proposed using a liquid-delay-line-oscillator, which is composed of two pairs of arch-shaped interdigital transducers (IDTs) on a double-layered substrate composed of a piezoelectric ceramic plate and an acrylic plate, a polymer-film diaphragm as one wall of a liquid cavity, and a water layer. The diaphragm functions as an ultrasound-beam reflector. The acoustical phase change arises corresponding to the pressure exerted on the central part of the diaphragm. The relationship between the mechanical displacement and the oscillation frequency is evaluated experimentally on the basis of the acoustical delay length linearly dependent on the thickness of the water layer. The static and dynamic displacement measurements are demonstrated. The present technique is promising for sensing sound pressure, which could be regarded as a precise and convenient method.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128235094","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-08DOI: 10.1109/ULTSYM.2002.1193351
M. Hofer, N. Finger, G. Kovacs, J. Schoberl, U. Langer, R. Lerch
Though loss parameters in SAW propagation are used as input for fast analysis models for the simulation of SAW devices, the quantitatively correct description of loss mechanisms is still a challenging task. Therefore, it is important to develop exact measurement and simulation methods which are able to determine these loss parameters accurately. By the use of special boundary conditions, the finite element method (FEM) is able to fulfill these requirements. Regarding the periodic substructure of common SAW devices, we have incorporated periodic boundary conditions (PBCs) in our simulation code. The piezoelectric substrate of SAW devices operating at high frequencies can be modeled as a semi-infinite half space. Therefore, we introduce newly evolved absorbing boundary conditions. They allow us to examine effects emerging from bulk acoustic wave (BAW) radiation (e.g. bulk wave onset frequencies) and assess propagation loss due to leakage and bulk wave conversion accurately.
{"title":"Finite element simulation of bulk- and surface acoustic wave (SAW) interaction in SAW devices","authors":"M. Hofer, N. Finger, G. Kovacs, J. Schoberl, U. Langer, R. Lerch","doi":"10.1109/ULTSYM.2002.1193351","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193351","url":null,"abstract":"Though loss parameters in SAW propagation are used as input for fast analysis models for the simulation of SAW devices, the quantitatively correct description of loss mechanisms is still a challenging task. Therefore, it is important to develop exact measurement and simulation methods which are able to determine these loss parameters accurately. By the use of special boundary conditions, the finite element method (FEM) is able to fulfill these requirements. Regarding the periodic substructure of common SAW devices, we have incorporated periodic boundary conditions (PBCs) in our simulation code. The piezoelectric substrate of SAW devices operating at high frequencies can be modeled as a semi-infinite half space. Therefore, we introduce newly evolved absorbing boundary conditions. They allow us to examine effects emerging from bulk acoustic wave (BAW) radiation (e.g. bulk wave onset frequencies) and assess propagation loss due to leakage and bulk wave conversion accurately.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127064018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-08DOI: 10.1109/ULTSYM.2002.1193447
L. Matsiev
Application of quartz tuning fork resonators to high throughput gravimetric measurements is described. It is demonstrated that tuning fork resonators can be successfully used for accurate measurement of mass in the tens-of-micrograms range without incurring restrictions on sample shape, size, mechanical properties or sample adhesion and position on sensor surface. Experimental results on sensor calibration and weighing small samples of materials are presented.
{"title":"Tuning fork QCM. Application to powder and gel technology","authors":"L. Matsiev","doi":"10.1109/ULTSYM.2002.1193447","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193447","url":null,"abstract":"Application of quartz tuning fork resonators to high throughput gravimetric measurements is described. It is demonstrated that tuning fork resonators can be successfully used for accurate measurement of mass in the tens-of-micrograms range without incurring restrictions on sample shape, size, mechanical properties or sample adhesion and position on sensor surface. Experimental results on sensor calibration and weighing small samples of materials are presented.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127022422","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-08DOI: 10.1109/ULTSYM.2002.1193443
M. Rychagov, S. Tereshchenko, Y. Masloboev, M. Simon, L. Lynnworth
Quadrature integration of flow velocity along prescribed parallel paths has been one of the preferred solutions for accurate computation of volumetric flowrate Q for over thirty years. The present work extends the quadrature volumetric flowmetering method to determining from sound speed c/sub 3/ along the same quadrature paths, the fluid temperature T, density /spl rho/ and mass flowrate M/sub F/ in the presence of a density gradient. Quadrature integration of /spl rho//sub i/ /spl times/ V/sub i/ products V/sub i/ obtained from c/sub 3i/ is useful to the extent the fluid is sufficiently pure and defined so that the uncertainty in sound speed c/sub i/ along each path generates only a small uncertainty in density pi along those same paths. Instead of "useful to the extent" one could just as well say "limited to the extent." Recognizing this limitation, it is interesting to compare the density and mass flowrate determined from (a) ultrasonic measurements of propagation across the fluid, as indicated above, with density and mass flowrate determinations based on two other known methods. These two methods are: (b) reflection coefficient measurement of fluid characteristic impedance Z, which would seem capable of leading to /spl rho/ after dividing by c; and determining /spl rho/ based on (c) torsional wavespeed in a waveguide of noncircular cross section.
{"title":"Mass flowmeters for fluids with density gradient","authors":"M. Rychagov, S. Tereshchenko, Y. Masloboev, M. Simon, L. Lynnworth","doi":"10.1109/ULTSYM.2002.1193443","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193443","url":null,"abstract":"Quadrature integration of flow velocity along prescribed parallel paths has been one of the preferred solutions for accurate computation of volumetric flowrate Q for over thirty years. The present work extends the quadrature volumetric flowmetering method to determining from sound speed c/sub 3/ along the same quadrature paths, the fluid temperature T, density /spl rho/ and mass flowrate M/sub F/ in the presence of a density gradient. Quadrature integration of /spl rho//sub i/ /spl times/ V/sub i/ products V/sub i/ obtained from c/sub 3i/ is useful to the extent the fluid is sufficiently pure and defined so that the uncertainty in sound speed c/sub i/ along each path generates only a small uncertainty in density pi along those same paths. Instead of \"useful to the extent\" one could just as well say \"limited to the extent.\" Recognizing this limitation, it is interesting to compare the density and mass flowrate determined from (a) ultrasonic measurements of propagation across the fluid, as indicated above, with density and mass flowrate determinations based on two other known methods. These two methods are: (b) reflection coefficient measurement of fluid characteristic impedance Z, which would seem capable of leading to /spl rho/ after dividing by c; and determining /spl rho/ based on (c) torsional wavespeed in a waveguide of noncircular cross section.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127356276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-08DOI: 10.1109/ULTSYM.2002.1193453
B. Sinha, Qingchen Liu
A finite-difference formulation of equations of motion for elastic waves in prestressed formations has been used to calculate synthetic waveforms at an array of receivers in a liquid-filled borehole. Equations of motion for elastic waves in prestressed materials are derived from rotationally invariant equations of nonlinear elasticity. These equations describe the influence of borehole hydrostatic (mud) pressure as well as formation stresses on acoustic waves produced by either a monopole or dipole transmitter placed on the borehole axis. The synthetic waveforms are processed by a modified matrix pencil algorithm for isolating both dispersive and non-dispersive arrivals in the wavetrain. Computational results show that a difference in the maximum and minimum horizontal stresses causes dipole dispersion crossovers that can be used as an indicator of stress-induced anisotropy dominating the data. On the other hand, an increase in the overburden stress causes both the Stoneley and dipole dispersions to shift toward higher velocities by varying amounts at various frequencies. Any increase in the mud pressure introduces an altered annulus surrounding the borehole surface. This annulus exhibits radial variations in the near-wellbore radial and hoop stresses. Both the Stoneley and dipole dispersions show increasing velocities at higher frequencies. Changes in borehole acoustic wave velocities caused by a change in any one of the formation principal stresses yield frequency-dependent overburden, maximum horizontal, and minimum horizontal stress coefficients of velocities. These stress coefficients of velocities can be used to invert measured changes in borehole dispersions at various depths for corresponding changes in formation stresses.
{"title":"Acoustic waves in pressurized boreholes in formations with triaxial stresses","authors":"B. Sinha, Qingchen Liu","doi":"10.1109/ULTSYM.2002.1193453","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193453","url":null,"abstract":"A finite-difference formulation of equations of motion for elastic waves in prestressed formations has been used to calculate synthetic waveforms at an array of receivers in a liquid-filled borehole. Equations of motion for elastic waves in prestressed materials are derived from rotationally invariant equations of nonlinear elasticity. These equations describe the influence of borehole hydrostatic (mud) pressure as well as formation stresses on acoustic waves produced by either a monopole or dipole transmitter placed on the borehole axis. The synthetic waveforms are processed by a modified matrix pencil algorithm for isolating both dispersive and non-dispersive arrivals in the wavetrain. Computational results show that a difference in the maximum and minimum horizontal stresses causes dipole dispersion crossovers that can be used as an indicator of stress-induced anisotropy dominating the data. On the other hand, an increase in the overburden stress causes both the Stoneley and dipole dispersions to shift toward higher velocities by varying amounts at various frequencies. Any increase in the mud pressure introduces an altered annulus surrounding the borehole surface. This annulus exhibits radial variations in the near-wellbore radial and hoop stresses. Both the Stoneley and dipole dispersions show increasing velocities at higher frequencies. Changes in borehole acoustic wave velocities caused by a change in any one of the formation principal stresses yield frequency-dependent overburden, maximum horizontal, and minimum horizontal stress coefficients of velocities. These stress coefficients of velocities can be used to invert measured changes in borehole dispersions at various depths for corresponding changes in formation stresses.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127499088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-08DOI: 10.1109/ULTSYM.2002.1193515
A. Fiorillo, G. D'Angelo
The sophisticated sonar system of bats is capable of extracting a complete set of information in order to locate and characterize the prey. Curved piezopolymer transducers were already used in the same frequency range to generate ultrasonic waves in air. In this article we investigate the possibility to process echo-signals by using a neural network, similarly to the biological model. We analyse frequency modulated signals, which are only a part of the most complex bat echo signal, in order to measure the target distance through the time of flight evaluation. Chirps are first amplified with a low noise CMOS amplifier, than are properly filtered and rectified in order to obtain a pulse time sequence. Finally the pulse signal is processed by the first level of a neural network to recognize the right pulse time sequence and evaluate the time of flight. Simulated results carried out by using both Matlab and Spice programs, will be presented with reference to piezo-polymer transducers application.
{"title":"Echo signals processing with neural network in bat-like sonars based on PVDF","authors":"A. Fiorillo, G. D'Angelo","doi":"10.1109/ULTSYM.2002.1193515","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193515","url":null,"abstract":"The sophisticated sonar system of bats is capable of extracting a complete set of information in order to locate and characterize the prey. Curved piezopolymer transducers were already used in the same frequency range to generate ultrasonic waves in air. In this article we investigate the possibility to process echo-signals by using a neural network, similarly to the biological model. We analyse frequency modulated signals, which are only a part of the most complex bat echo signal, in order to measure the target distance through the time of flight evaluation. Chirps are first amplified with a low noise CMOS amplifier, than are properly filtered and rectified in order to obtain a pulse time sequence. Finally the pulse signal is processed by the first level of a neural network to recognize the right pulse time sequence and evaluate the time of flight. Simulated results carried out by using both Matlab and Spice programs, will be presented with reference to piezo-polymer transducers application.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129143951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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