Pub Date : 1995-11-07DOI: 10.1109/ULTSYM.1995.495868
Y. Yong
A storage algorithm for solving a large piezoelectric eigenvalue problem is presented. The storage algorithm could reduce memory requirements and computational time by more than an order of magnitude over a current storage scheme, which separates the mechanical stiffness matrix elements from the dielectric matrix elements in the finite element matrix equations. Details of the proposed algorithm is presented with regards to using a Lanczos eigenvalue solver. Finite element solutions for the free vibrations of a piezoelectric cube and bar are shown to illustrate the economy of the proposed storage scheme. Graphs of memory usage and computational time versus the size of the finite element model are presented to compare the results of the current storage scheme with those of the proposed storage scheme.
{"title":"A new storage scheme for the Lanczos solution of large scale finite element models of piezoelectric resonators","authors":"Y. Yong","doi":"10.1109/ULTSYM.1995.495868","DOIUrl":"https://doi.org/10.1109/ULTSYM.1995.495868","url":null,"abstract":"A storage algorithm for solving a large piezoelectric eigenvalue problem is presented. The storage algorithm could reduce memory requirements and computational time by more than an order of magnitude over a current storage scheme, which separates the mechanical stiffness matrix elements from the dielectric matrix elements in the finite element matrix equations. Details of the proposed algorithm is presented with regards to using a Lanczos eigenvalue solver. Finite element solutions for the free vibrations of a piezoelectric cube and bar are shown to illustrate the economy of the proposed storage scheme. Graphs of memory usage and computational time versus the size of the finite element model are presented to compare the results of the current storage scheme with those of the proposed storage scheme.","PeriodicalId":268177,"journal":{"name":"1995 IEEE Ultrasonics Symposium. Proceedings. An International Symposium","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126536132","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 : 1995-11-07DOI: 10.1109/ULTSYM.1995.495867
K. Fujimoto, Y. Ishibashi, M. Shibata, T. Suzuki, S. Aida, N. Ioritani, S. Shirai, S. Orikasa
When soft tissues are coagulated instantaneously during a high temperature local heating therapy for cancer using high-intensity focused ultrasound, it is extremely important to have good control over the heated area. However, scattering of the ultrasonic energy by cavitation bubbles generated by sonication degrades the heating performance at the focal spot, and there is an undesirable rise in temperature along the ultrasonic path due to the absorption of ultrasonic energy. To overcome this problem, the authors developed a new method called Cavitation Suppression Technique (CAST) to promote cavitation collapse and remove gas bubbles by sweeping the driving frequency rapidly. In this study, best conditions for CAST were obtained by comparing the effect of cavitation suppression on various driving parameters. The cavitation suppression effect and control of the heating due to field overlap (near-field heating) during focus scanning were confirmed in in vitro and in vivo experiments.
{"title":"A new cavitation suppression technique for local ablation using high-intensity focused ultrasound","authors":"K. Fujimoto, Y. Ishibashi, M. Shibata, T. Suzuki, S. Aida, N. Ioritani, S. Shirai, S. Orikasa","doi":"10.1109/ULTSYM.1995.495867","DOIUrl":"https://doi.org/10.1109/ULTSYM.1995.495867","url":null,"abstract":"When soft tissues are coagulated instantaneously during a high temperature local heating therapy for cancer using high-intensity focused ultrasound, it is extremely important to have good control over the heated area. However, scattering of the ultrasonic energy by cavitation bubbles generated by sonication degrades the heating performance at the focal spot, and there is an undesirable rise in temperature along the ultrasonic path due to the absorption of ultrasonic energy. To overcome this problem, the authors developed a new method called Cavitation Suppression Technique (CAST) to promote cavitation collapse and remove gas bubbles by sweeping the driving frequency rapidly. In this study, best conditions for CAST were obtained by comparing the effect of cavitation suppression on various driving parameters. The cavitation suppression effect and control of the heating due to field overlap (near-field heating) during focus scanning were confirmed in in vitro and in vivo experiments.","PeriodicalId":268177,"journal":{"name":"1995 IEEE Ultrasonics Symposium. Proceedings. An International Symposium","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126921282","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 : 1995-11-07DOI: 10.1109/ULTSYM.1995.495719
Q.M. Zhang, X. Geng
We address the problems of the vibration of a periodic piezocomposite plate (2-2 composite) under external electric fields and the reflection and transmission of a plane wave incident on the fluid-composite interface based on an analytical method developed recently, which takes into account explicitly the heterogeneous nature of the piezocomposites. It is shown that due to the finite thickness of the composite plate, a series of piezo-active modes at frequencies near and above the stop band edge mode frequency may be excited. It is also shown that, as a result of the heterogeneous structure of the composite, the reflection coefficient from the fluid-composite interface is a complex number, which should have important implication on the design of the quarter wave matching layer in composite transducers.
{"title":"Electric field forced vibration of a periodic piezocomposite plate with laminated structure and reflection and transmission of a plane wave at the fluid-composite interface","authors":"Q.M. Zhang, X. Geng","doi":"10.1109/ULTSYM.1995.495719","DOIUrl":"https://doi.org/10.1109/ULTSYM.1995.495719","url":null,"abstract":"We address the problems of the vibration of a periodic piezocomposite plate (2-2 composite) under external electric fields and the reflection and transmission of a plane wave incident on the fluid-composite interface based on an analytical method developed recently, which takes into account explicitly the heterogeneous nature of the piezocomposites. It is shown that due to the finite thickness of the composite plate, a series of piezo-active modes at frequencies near and above the stop band edge mode frequency may be excited. It is also shown that, as a result of the heterogeneous structure of the composite, the reflection coefficient from the fluid-composite interface is a complex number, which should have important implication on the design of the quarter wave matching layer in composite transducers.","PeriodicalId":268177,"journal":{"name":"1995 IEEE Ultrasonics Symposium. Proceedings. An International Symposium","volume":"66 1-2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114122496","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 : 1995-11-07DOI: 10.1109/ULTSYM.1995.495707
Wei Li, J. Achenbach
The determination of elastic constants of bulk specimens and anisotropic films deposited on anisotropic substrates from V(z) measurements obtained by using a line-focus acoustic microscope is discussed. The procedure has three essential components: (1) V(z) curve measurement as a function of direction of wave mode propagation in the sample at fixed frequency and/or as a function of the frequency or film thickness for a fixed direction, (2) use of a measurement model for parametric studies of V(z) curves, and (3) determination of elastic constants by systematically comparing wave-mode velocities obtained from the measurement model and the V(z) measurement. Some examples are presented for transition metal nitride films used as hard protective coatings of softer surfaces. Attention is also directed to certain advantages of using multiple modes. It is shown that multiple-mode results reduce the region in a plane of material constants for which a deviation function between theoretical and experimental results has prescribed small values. Finally a brief discussion is presented of some recent results obtained at much lower frequencies by time resolved acoustic microscopy.
{"title":"Measuring thin-film elastic constants by line-focus acoustic microscopy","authors":"Wei Li, J. Achenbach","doi":"10.1109/ULTSYM.1995.495707","DOIUrl":"https://doi.org/10.1109/ULTSYM.1995.495707","url":null,"abstract":"The determination of elastic constants of bulk specimens and anisotropic films deposited on anisotropic substrates from V(z) measurements obtained by using a line-focus acoustic microscope is discussed. The procedure has three essential components: (1) V(z) curve measurement as a function of direction of wave mode propagation in the sample at fixed frequency and/or as a function of the frequency or film thickness for a fixed direction, (2) use of a measurement model for parametric studies of V(z) curves, and (3) determination of elastic constants by systematically comparing wave-mode velocities obtained from the measurement model and the V(z) measurement. Some examples are presented for transition metal nitride films used as hard protective coatings of softer surfaces. Attention is also directed to certain advantages of using multiple modes. It is shown that multiple-mode results reduce the region in a plane of material constants for which a deviation function between theoretical and experimental results has prescribed small values. Finally a brief discussion is presented of some recent results obtained at much lower frequencies by time resolved acoustic microscopy.","PeriodicalId":268177,"journal":{"name":"1995 IEEE Ultrasonics Symposium. Proceedings. An International Symposium","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121122576","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 : 1995-11-07DOI: 10.1109/ULTSYM.1995.495596
T. Cameron, W. Hunt
The SAW amplifier was a topic of considerable interest twenty years ago and in light of numerous material advances in compound semiconductors since that time, perhaps should be revisited. One of the limitations of this device was the excessive power consumption due to the inability to grow very high resistivity semiconductor films with high electron mobility. In addition, the high drift voltages on the order of hundreds of volts made the devices impractical for commercial system applications. In this paper we implement a SAW amplifier on a multilayer GaAs substrate. Fabricating the device on a thin (<1 /spl mu/m), lightly doped n-type (n/sub 0//spl sim/10/sup 14/) epitaxial layer of GaAs enables a very high sheet resistance to be obtained while maintaining the high electron mobility of GaAs.
{"title":"SAW amplifiers on multilayer GaAs substrates","authors":"T. Cameron, W. Hunt","doi":"10.1109/ULTSYM.1995.495596","DOIUrl":"https://doi.org/10.1109/ULTSYM.1995.495596","url":null,"abstract":"The SAW amplifier was a topic of considerable interest twenty years ago and in light of numerous material advances in compound semiconductors since that time, perhaps should be revisited. One of the limitations of this device was the excessive power consumption due to the inability to grow very high resistivity semiconductor films with high electron mobility. In addition, the high drift voltages on the order of hundreds of volts made the devices impractical for commercial system applications. In this paper we implement a SAW amplifier on a multilayer GaAs substrate. Fabricating the device on a thin (<1 /spl mu/m), lightly doped n-type (n/sub 0//spl sim/10/sup 14/) epitaxial layer of GaAs enables a very high sheet resistance to be obtained while maintaining the high electron mobility of GaAs.","PeriodicalId":268177,"journal":{"name":"1995 IEEE Ultrasonics Symposium. Proceedings. An International Symposium","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116253526","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 : 1995-11-07DOI: 10.1109/ULTSYM.1995.495817
M. Bilgen, M. Insana
Accurate and precise displacement estimates are the key to obtaining high-quality elastograms. In elastographic imaging, echo-signals acquired before and after tissue compression are cross-correlated and the location of the cross-correlation maximum is used for determining the local tissue displacement and deformation. A stochastic strain model under static compression is discussed, and an inverse coordinate transformation relating the post-compression coordinate to the pre-compressed coordinate is introduced. Analytic formulas for the cross-correlation are provided and used to analyse stochastic strain-induced effects. Displacement causes decorrelation of the pre- and post-compression signals and consequently results in a nonstationary cross-correlation function. Adjusting experimental and signal processing variables, such as stretching the post-compression echo-signal and/or shaping the ultrasonic pulse are shown to significantly increase the accuracy of the displacement estimates.
{"title":"Statistical properties of elastograms","authors":"M. Bilgen, M. Insana","doi":"10.1109/ULTSYM.1995.495817","DOIUrl":"https://doi.org/10.1109/ULTSYM.1995.495817","url":null,"abstract":"Accurate and precise displacement estimates are the key to obtaining high-quality elastograms. In elastographic imaging, echo-signals acquired before and after tissue compression are cross-correlated and the location of the cross-correlation maximum is used for determining the local tissue displacement and deformation. A stochastic strain model under static compression is discussed, and an inverse coordinate transformation relating the post-compression coordinate to the pre-compressed coordinate is introduced. Analytic formulas for the cross-correlation are provided and used to analyse stochastic strain-induced effects. Displacement causes decorrelation of the pre- and post-compression signals and consequently results in a nonstationary cross-correlation function. Adjusting experimental and signal processing variables, such as stretching the post-compression echo-signal and/or shaping the ultrasonic pulse are shown to significantly increase the accuracy of the displacement estimates.","PeriodicalId":268177,"journal":{"name":"1995 IEEE Ultrasonics Symposium. Proceedings. An International Symposium","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116754863","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 : 1995-11-07DOI: 10.1109/ULTSYM.1995.495842
W. Li, A. V. D. van der Steen, C. Lancée, J. Honkoop, E. Gussenhoven, N. Bom
The time-varying characteristics of blood scattering on high frequency intravascular ultrasound were investigated in vivo in 5 pig experiments. The RF correlation time T/sub c/ was measured on an M-mode sequence acquired at a high pulse repetition rate. Results showed that T/sub c/ measured in blood was approximately 1 ms which was significantly shorter than that measured in wall (T/sub c//spl Gt/6 ms). Using the correlation output as a weighting function, most of the blood scattering echoes can be removed for contrast enhancement of the lumen interface.
{"title":"Temporal correlation of blood scattering signals from intravascular ultrasound","authors":"W. Li, A. V. D. van der Steen, C. Lancée, J. Honkoop, E. Gussenhoven, N. Bom","doi":"10.1109/ULTSYM.1995.495842","DOIUrl":"https://doi.org/10.1109/ULTSYM.1995.495842","url":null,"abstract":"The time-varying characteristics of blood scattering on high frequency intravascular ultrasound were investigated in vivo in 5 pig experiments. The RF correlation time T/sub c/ was measured on an M-mode sequence acquired at a high pulse repetition rate. Results showed that T/sub c/ measured in blood was approximately 1 ms which was significantly shorter than that measured in wall (T/sub c//spl Gt/6 ms). Using the correlation output as a weighting function, most of the blood scattering echoes can be removed for contrast enhancement of the lumen interface.","PeriodicalId":268177,"journal":{"name":"1995 IEEE Ultrasonics Symposium. Proceedings. An International Symposium","volume":"65 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114005191","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 : 1995-11-07DOI: 10.1109/ULTSYM.1995.495580
Y. Shui, Y. Lu,
In this paper, we propose a Complex Impedance Model (CIM) for SAW and Leaky SAW (LSAW) propagating under periodic gratings. CIM starts with the postulation of impedance discontinuity, based on which a reflective grating is equivalent to a transmission line with complex impedance and complex propagation phase shift. As a result, the reflection and transmission of SAW and LSAW can be expressed in simple, analytical formulae. The model is compared with COM analysis and entire equivalence proved. Also a method is developed to extract CIM parameters such as center frequency, impedance mismatch coefficient, propagation attenuation coefficient and shunt susceptance element. As an example, numerical results for LSAW under gratings on 36-YX-LiTaO/sub 3/ substrate are presented.
{"title":"A complex impedance model for SAW and LSAW propagation in periodic grating","authors":"Y. Shui, Y. Lu,","doi":"10.1109/ULTSYM.1995.495580","DOIUrl":"https://doi.org/10.1109/ULTSYM.1995.495580","url":null,"abstract":"In this paper, we propose a Complex Impedance Model (CIM) for SAW and Leaky SAW (LSAW) propagating under periodic gratings. CIM starts with the postulation of impedance discontinuity, based on which a reflective grating is equivalent to a transmission line with complex impedance and complex propagation phase shift. As a result, the reflection and transmission of SAW and LSAW can be expressed in simple, analytical formulae. The model is compared with COM analysis and entire equivalence proved. Also a method is developed to extract CIM parameters such as center frequency, impedance mismatch coefficient, propagation attenuation coefficient and shunt susceptance element. As an example, numerical results for LSAW under gratings on 36-YX-LiTaO/sub 3/ substrate are presented.","PeriodicalId":268177,"journal":{"name":"1995 IEEE Ultrasonics Symposium. Proceedings. An International Symposium","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122757312","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 : 1995-11-07DOI: 10.1109/ULTSYM.1995.495701
Z.S. Wu, S. Fu, K.J. Cheng, C. Gan, S.Y. Zhang
Acoustoelectric signals in semiconductors induced by a pulsed laser beam are analyzed theoretically and measured experimentally. These signals result from two interactions: photoacoustic in a piezoelectric material illuminated by the laser beam and acoustoelectric in a semiconductor coupled with the piezoelectric body through an air gap.
{"title":"Acoustoelectric signals in semiconductors generated by laser beams","authors":"Z.S. Wu, S. Fu, K.J. Cheng, C. Gan, S.Y. Zhang","doi":"10.1109/ULTSYM.1995.495701","DOIUrl":"https://doi.org/10.1109/ULTSYM.1995.495701","url":null,"abstract":"Acoustoelectric signals in semiconductors induced by a pulsed laser beam are analyzed theoretically and measured experimentally. These signals result from two interactions: photoacoustic in a piezoelectric material illuminated by the laser beam and acoustoelectric in a semiconductor coupled with the piezoelectric body through an air gap.","PeriodicalId":268177,"journal":{"name":"1995 IEEE Ultrasonics Symposium. Proceedings. An International Symposium","volume":"7 11","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131574541","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 : 1995-11-07DOI: 10.1109/ULTSYM.1995.495815
R. Murthy, N. Bilgutay
In previous work, multiresolution representations that provide a hierarchical framework for analyzing the information content of images were used to obtain contrast enhancement in medical sonograms. Image decomposition and reconstruction was implemented using the two dimensional wavelet transform with a computationally efficient quadrature mirror filter bank architecture. The images were reconstructed at scales likely to exhibit high target energy localization indicating the presence of a tumor. The concepts were applied to B-scan images from in vivo liver images. It was observed that the reconstructed images at scale 1 provided the most enhancement but did not achieve sufficient image contrast. In order to utilize the information present in the adjacent scales, the reconstructed signals are nonlinearly combined using algorithms which exploit the observation that the abnormalities are less echogenic and less sensitive to frequency shifts than the surrounding healthy tissue. It was observed that the frequency diversity techniques outperform the reconstructed images.
{"title":"Scaling techniques for medical image enhancement","authors":"R. Murthy, N. Bilgutay","doi":"10.1109/ULTSYM.1995.495815","DOIUrl":"https://doi.org/10.1109/ULTSYM.1995.495815","url":null,"abstract":"In previous work, multiresolution representations that provide a hierarchical framework for analyzing the information content of images were used to obtain contrast enhancement in medical sonograms. Image decomposition and reconstruction was implemented using the two dimensional wavelet transform with a computationally efficient quadrature mirror filter bank architecture. The images were reconstructed at scales likely to exhibit high target energy localization indicating the presence of a tumor. The concepts were applied to B-scan images from in vivo liver images. It was observed that the reconstructed images at scale 1 provided the most enhancement but did not achieve sufficient image contrast. In order to utilize the information present in the adjacent scales, the reconstructed signals are nonlinearly combined using algorithms which exploit the observation that the abnormalities are less echogenic and less sensitive to frequency shifts than the surrounding healthy tissue. It was observed that the frequency diversity techniques outperform the reconstructed images.","PeriodicalId":268177,"journal":{"name":"1995 IEEE Ultrasonics Symposium. Proceedings. An International Symposium","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128100295","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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