Pub Date : 1988-10-02DOI: 10.1109/ULTSYM.1988.49424
M. F. Leach, G. A. Rubin
A total of 25 granites, 20 greenstones, and three norite nominal 1-in. cores were cut into approximately 10-in. lengths which were glued to the amplifying horn of a 10-kHz transducers. Each specimen was subjected to a maximum load of a few hundred watts of ultrasound. Tests were terminated at fracture, at pronounced detuning accompanied by abrupt changes in the strain and load power signals, or after approximately five minutes if the specimen did not fail. The generation of ultrasonic resonances in the rocks was shown to lead to local stress exceeding their tensile strength and hence has caused failure at kerfing energies which are significantly lower than by several other techniques for fracturing rock. Cyclic loading under high-frequency ultrasound has produced significant weakening of rock whereby the compressive strength has been decreased by up to 70%. Fractures occur preferentially along ore veins at low input power. In samples of softer rock, large temperature increases are induced while harder rock undergoes small or no temperature change.<>
{"title":"Fragmentation of rocks under ultrasonic loading","authors":"M. F. Leach, G. A. Rubin","doi":"10.1109/ULTSYM.1988.49424","DOIUrl":"https://doi.org/10.1109/ULTSYM.1988.49424","url":null,"abstract":"A total of 25 granites, 20 greenstones, and three norite nominal 1-in. cores were cut into approximately 10-in. lengths which were glued to the amplifying horn of a 10-kHz transducers. Each specimen was subjected to a maximum load of a few hundred watts of ultrasound. Tests were terminated at fracture, at pronounced detuning accompanied by abrupt changes in the strain and load power signals, or after approximately five minutes if the specimen did not fail. The generation of ultrasonic resonances in the rocks was shown to lead to local stress exceeding their tensile strength and hence has caused failure at kerfing energies which are significantly lower than by several other techniques for fracturing rock. Cyclic loading under high-frequency ultrasound has produced significant weakening of rock whereby the compressive strength has been decreased by up to 70%. Fractures occur preferentially along ore veins at low input power. In samples of softer rock, large temperature increases are induced while harder rock undergoes small or no temperature change.<<ETX>>","PeriodicalId":263198,"journal":{"name":"IEEE 1988 Ultrasonics Symposium Proceedings.","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1988-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127838889","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 : 1988-10-02DOI: 10.1109/ULTSYM.1988.49356
H. Robinson, Y. Hahn, J. N. Gau
A study of perturbative and variational approaches is carried out for SAW (surface acoustic wave) reflections. It is shown that the perturbation treatment and variational formulation are mutually consistent. These two approaches yield nearly identical results for the reflection coefficients and velocity shifts due to metal finger and groove overlays. The on- and off-resonance behavior of the reflection coefficient can be described correctly using either one of these theories, with inclusion of the overlay shape dependence to account for off-resonance effects. The variational approach lends itself more readily to analysis of arbitrary grating structures since no complicated boundary terms appear, and it also can include higher-order effects neglected in first-order perturbation theory by a judicious choice of the trial function. But the utility of the variational principle is limited in calculating physically meaningful results by the accuracy of the trial functions used.<>
{"title":"Analysis of SAW reflection","authors":"H. Robinson, Y. Hahn, J. N. Gau","doi":"10.1109/ULTSYM.1988.49356","DOIUrl":"https://doi.org/10.1109/ULTSYM.1988.49356","url":null,"abstract":"A study of perturbative and variational approaches is carried out for SAW (surface acoustic wave) reflections. It is shown that the perturbation treatment and variational formulation are mutually consistent. These two approaches yield nearly identical results for the reflection coefficients and velocity shifts due to metal finger and groove overlays. The on- and off-resonance behavior of the reflection coefficient can be described correctly using either one of these theories, with inclusion of the overlay shape dependence to account for off-resonance effects. The variational approach lends itself more readily to analysis of arbitrary grating structures since no complicated boundary terms appear, and it also can include higher-order effects neglected in first-order perturbation theory by a judicious choice of the trial function. But the utility of the variational principle is limited in calculating physically meaningful results by the accuracy of the trial functions used.<<ETX>>","PeriodicalId":263198,"journal":{"name":"IEEE 1988 Ultrasonics Symposium Proceedings.","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1988-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121329051","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 : 1988-10-02DOI: 10.1109/ULTSYM.1988.49539
J. Sandhu, R. Thomas
The authors discuss some of the basic principles underlying acoustography and its use as a nondestructive evaluation methodology. Acoustography is a process of forming ultrasonic images in a manner analogous to radiography and fluoroscopy. A sound source insonifies the test object with a uniform field of ultrasound. As the ultrasonic waves pass through the test object, they are differentially attenuated. The existing ultrasound casts a shadow that is converted into a visual image using an 'acousto-optical' display. It is concluded that acoustography can detect typical flaws, e.g., delaminations, inclusions, impact damage porosity, encountered in graphite/epoxy composite laminates. Since a direct full-field image is obtained within seconds, acoustography offers the potential for high-speed testing of large areas. Acoustography can inspect complex geometry parts with relative ease compared with conventional ultrasonic methods.<>
{"title":"Acoustographic nondestructive evaluation","authors":"J. Sandhu, R. Thomas","doi":"10.1109/ULTSYM.1988.49539","DOIUrl":"https://doi.org/10.1109/ULTSYM.1988.49539","url":null,"abstract":"The authors discuss some of the basic principles underlying acoustography and its use as a nondestructive evaluation methodology. Acoustography is a process of forming ultrasonic images in a manner analogous to radiography and fluoroscopy. A sound source insonifies the test object with a uniform field of ultrasound. As the ultrasonic waves pass through the test object, they are differentially attenuated. The existing ultrasound casts a shadow that is converted into a visual image using an 'acousto-optical' display. It is concluded that acoustography can detect typical flaws, e.g., delaminations, inclusions, impact damage porosity, encountered in graphite/epoxy composite laminates. Since a direct full-field image is obtained within seconds, acoustography offers the potential for high-speed testing of large areas. Acoustography can inspect complex geometry parts with relative ease compared with conventional ultrasonic methods.<<ETX>>","PeriodicalId":263198,"journal":{"name":"IEEE 1988 Ultrasonics Symposium Proceedings.","volume":"478 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1988-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128830903","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 : 1988-10-02DOI: 10.1109/ULTSYM.1988.49393
P. Kielczynski, W. Pajewski
A method is proposed for determining the shear impedance of viscoelastic liquids. To this end, SH (shear) surface waves of the Love and Bleustein-Culyaev types have been used. Preliminary measurements performed for typical mineral oils agree very well with theoretical predictions. It is concluded that the proposed method can be a few orders of magnitude more sensitive than the classical Mason method using SH bulk waves.<>
{"title":"A new method for the determination of the shear impedance of viscoelastic liquids","authors":"P. Kielczynski, W. Pajewski","doi":"10.1109/ULTSYM.1988.49393","DOIUrl":"https://doi.org/10.1109/ULTSYM.1988.49393","url":null,"abstract":"A method is proposed for determining the shear impedance of viscoelastic liquids. To this end, SH (shear) surface waves of the Love and Bleustein-Culyaev types have been used. Preliminary measurements performed for typical mineral oils agree very well with theoretical predictions. It is concluded that the proposed method can be a few orders of magnitude more sensitive than the classical Mason method using SH bulk waves.<<ETX>>","PeriodicalId":263198,"journal":{"name":"IEEE 1988 Ultrasonics Symposium Proceedings.","volume":"106 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1988-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116110243","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 : 1988-10-02DOI: 10.1109/ULTSYM.1988.49342
M. Takeuchi, K. Yamanouchi
A coupled-mode analysis is presented of the performance of a single-phase unidirectional transducer utilizing the internal reflections of floating electrodes of electrically open circuited and shorted metal strips within an interdigital electrode. All four independent parameters (self- and mutual-coupling coefficients, transduction coefficient, and static capacitance) governing the coupled-mode equation with an electrical transduction term are analytically derived using extended Legendre polynomial expansions of electrical fields and a perturbation analysis. The frequency response of the radiation admittance and the insertion loss, and the growing surface acoustic wave (SAW) field distributions are calculated from simple closed-form solutions of the coupled-mode equation. The shift effect of reflection and transduction centers due to the asymmetric electrode structure is clarified. Experimental results are given for test devices fabricated on a 128 degrees YX LiNbO/sub 3/ substrate, and compared with the theory. The theoretical results are in good agreement with experiments.<>
{"title":"Field analysis o SAW single-phase unidirectional transducers using internal floating electrodes","authors":"M. Takeuchi, K. Yamanouchi","doi":"10.1109/ULTSYM.1988.49342","DOIUrl":"https://doi.org/10.1109/ULTSYM.1988.49342","url":null,"abstract":"A coupled-mode analysis is presented of the performance of a single-phase unidirectional transducer utilizing the internal reflections of floating electrodes of electrically open circuited and shorted metal strips within an interdigital electrode. All four independent parameters (self- and mutual-coupling coefficients, transduction coefficient, and static capacitance) governing the coupled-mode equation with an electrical transduction term are analytically derived using extended Legendre polynomial expansions of electrical fields and a perturbation analysis. The frequency response of the radiation admittance and the insertion loss, and the growing surface acoustic wave (SAW) field distributions are calculated from simple closed-form solutions of the coupled-mode equation. The shift effect of reflection and transduction centers due to the asymmetric electrode structure is clarified. Experimental results are given for test devices fabricated on a 128 degrees YX LiNbO/sub 3/ substrate, and compared with the theory. The theoretical results are in good agreement with experiments.<<ETX>>","PeriodicalId":263198,"journal":{"name":"IEEE 1988 Ultrasonics Symposium Proceedings.","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1988-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117078297","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 : 1988-10-02DOI: 10.1109/ULTSYM.1988.49525
V. Suorsa, W. O’Brien
It is shown that time domain correlation can be used to estimate the volumetric flow in a vessel accurately without deteriorating effects due to the frequency-dependent attenuation of ultrasound. When the transmitted pulses are separated by a certain time and are reflected by the moving scatterers within the ultrasound beam, the time difference between the pulses changes. The observed time shift is directly related to the radial speed (relative to the beam axis) of the scatterers. If the flow velocity is sampled at different positions across the vessel, then the volume flow rate can be calculated. The time domain technique has been verified in a blood flow phantom using a blood mimicking substance and natural sponge as the attenuating medium between the transducer and the vessel. For hydrodynamically determined flow rates from 50 to 560 ml/min, the continuous volumetric flow has been ultrasonically assessed with an accuracy better than 21%.<>
{"title":"Effects of ultrasonic attenuation on the accuracy of the blood flow measurement technique utilizing time domain correlation","authors":"V. Suorsa, W. O’Brien","doi":"10.1109/ULTSYM.1988.49525","DOIUrl":"https://doi.org/10.1109/ULTSYM.1988.49525","url":null,"abstract":"It is shown that time domain correlation can be used to estimate the volumetric flow in a vessel accurately without deteriorating effects due to the frequency-dependent attenuation of ultrasound. When the transmitted pulses are separated by a certain time and are reflected by the moving scatterers within the ultrasound beam, the time difference between the pulses changes. The observed time shift is directly related to the radial speed (relative to the beam axis) of the scatterers. If the flow velocity is sampled at different positions across the vessel, then the volume flow rate can be calculated. The time domain technique has been verified in a blood flow phantom using a blood mimicking substance and natural sponge as the attenuating medium between the transducer and the vessel. For hydrodynamically determined flow rates from 50 to 560 ml/min, the continuous volumetric flow has been ultrasonically assessed with an accuracy better than 21%.<<ETX>>","PeriodicalId":263198,"journal":{"name":"IEEE 1988 Ultrasonics Symposium Proceedings.","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1988-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116138739","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 : 1988-10-02DOI: 10.1109/ULTSYM.1988.49447
H. Chan, K. Chiang, J. Gardner
A polarimetric fiber-optic sensor using a polarization-maintaining fiber is described. The principle of the sensor is based on the detection of ultrasonically induced birefringence in the fiber. Its response to continuous and pulsed ultrasound at different frequencies and different power levels is investigated. The beam profiles measured by this sensor are compared with those measured using a PVDF (polyvinylidene fluoride) hydrophone. The sensor output is observed to be a linear function of the square root of the total acoustic power measured using a radiation force balance. The application of this sensor to the characterization of medical ultrasonic transducers is also discussed.<>
{"title":"Polarimetric optical fiber sensor for ultrasonic power measurement","authors":"H. Chan, K. Chiang, J. Gardner","doi":"10.1109/ULTSYM.1988.49447","DOIUrl":"https://doi.org/10.1109/ULTSYM.1988.49447","url":null,"abstract":"A polarimetric fiber-optic sensor using a polarization-maintaining fiber is described. The principle of the sensor is based on the detection of ultrasonically induced birefringence in the fiber. Its response to continuous and pulsed ultrasound at different frequencies and different power levels is investigated. The beam profiles measured by this sensor are compared with those measured using a PVDF (polyvinylidene fluoride) hydrophone. The sensor output is observed to be a linear function of the square root of the total acoustic power measured using a radiation force balance. The application of this sensor to the characterization of medical ultrasonic transducers is also discussed.<<ETX>>","PeriodicalId":263198,"journal":{"name":"IEEE 1988 Ultrasonics Symposium Proceedings.","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1988-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125400194","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 : 1988-10-02DOI: 10.1109/ULTSYM.1988.49405
Henrik Jensen
It is noted that the finite-element method is a valuable supplement to the traditional methods for design of novel transducer types because it can determine the vibrational pattern of piezoelectric transducers and is applicable to any geometry. Computer programs for analysis of axisymmetric transducers, which include the complete set of piezoelectric equations, have been included. They can find eigenfrequencies for undamped transducers and perform forced-response analysis for transducers with internal and radiation damping. The superelement technique is used to model the transducer backing in an efficient way. Examples ranging from a freely vibrating disk to a real focused transducer with a conical backing are presented.<>
{"title":"Analysis of eigenfrequencies in piezoelectric transducers using the finite element method","authors":"Henrik Jensen","doi":"10.1109/ULTSYM.1988.49405","DOIUrl":"https://doi.org/10.1109/ULTSYM.1988.49405","url":null,"abstract":"It is noted that the finite-element method is a valuable supplement to the traditional methods for design of novel transducer types because it can determine the vibrational pattern of piezoelectric transducers and is applicable to any geometry. Computer programs for analysis of axisymmetric transducers, which include the complete set of piezoelectric equations, have been included. They can find eigenfrequencies for undamped transducers and perform forced-response analysis for transducers with internal and radiation damping. The superelement technique is used to model the transducer backing in an efficient way. Examples ranging from a freely vibrating disk to a real focused transducer with a conical backing are presented.<<ETX>>","PeriodicalId":263198,"journal":{"name":"IEEE 1988 Ultrasonics Symposium Proceedings.","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1988-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127063561","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 : 1988-10-02DOI: 10.1109/ULTSYM.1988.49478
Yasuhiro Sugawara, J. Kushibiki, N. Chubachi
The performance of a scanning reflection acoustic microscope system using concave transducers has been investigated numerically and experimentally. V(z) characteristics that contain information about leaky surface acoustic waves (LSAWs) at the water/sample boundary can be used to analyze the performance of the system. Numerical analyses of V(z) curves are made via the transfer function of the system using a concave transducer based on field theory, taking a fused quartz as a typical sample. The experiments are performed at a frequency of 375 MHz. It is revealed that the amplitude response of the V(z) curve contains a rapid periodic variation in the defocus region that is not directly related to the propagation properties of LSAW, whereas the phase response of the V(z) curve depends strongly on the propagation properties of LSAW.<>
{"title":"Performance of concave transducers in acoustic microscopy","authors":"Yasuhiro Sugawara, J. Kushibiki, N. Chubachi","doi":"10.1109/ULTSYM.1988.49478","DOIUrl":"https://doi.org/10.1109/ULTSYM.1988.49478","url":null,"abstract":"The performance of a scanning reflection acoustic microscope system using concave transducers has been investigated numerically and experimentally. V(z) characteristics that contain information about leaky surface acoustic waves (LSAWs) at the water/sample boundary can be used to analyze the performance of the system. Numerical analyses of V(z) curves are made via the transfer function of the system using a concave transducer based on field theory, taking a fused quartz as a typical sample. The experiments are performed at a frequency of 375 MHz. It is revealed that the amplitude response of the V(z) curve contains a rapid periodic variation in the defocus region that is not directly related to the propagation properties of LSAW, whereas the phase response of the V(z) curve depends strongly on the propagation properties of LSAW.<<ETX>>","PeriodicalId":263198,"journal":{"name":"IEEE 1988 Ultrasonics Symposium Proceedings.","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1988-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125933063","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 : 1988-10-02DOI: 10.1109/ULTSYM.1988.49360
J. Haartsen, A. Venema
A method to detect surface acoustic waves (SAW) in a ZnO-SiO/sub 2/Si layered structure is proposed. The detector consists of two p/sup +/ electrodes implanted in an n-type epilayer, thus forming a lateral p/sup +/-n-p/sup +/ structure. The p/sup +/ electrodes are reverse-biased to deplete the gap between the electrodes. When the depletion regions of the two p/sup +/-n junctions meet, a lateral current flows. Its magnitude is determined by the potential barrier in the gap. The electric field accompanying a traveling SAW penetrates into the depleted gap and modulates the potential barrier and therefore the biased detector current. The output current signal depends on the bias conditions of the detector current. This novel detector can be used to realize current-controlled taps in programmable filters. Monolithic test devices operating at a frequency of 80 MHz were realized in a ZnO-SiO/sub 2/-Si layered structure with a 9- mu m-thick epilayer of 20 Omega cm, a 0.1- mu m-thick oxide layer, and a 10- mu m-thick ZnO layer.<>
{"title":"The barrier-modulated tap: a new SAW detection method in silicon","authors":"J. Haartsen, A. Venema","doi":"10.1109/ULTSYM.1988.49360","DOIUrl":"https://doi.org/10.1109/ULTSYM.1988.49360","url":null,"abstract":"A method to detect surface acoustic waves (SAW) in a ZnO-SiO/sub 2/Si layered structure is proposed. The detector consists of two p/sup +/ electrodes implanted in an n-type epilayer, thus forming a lateral p/sup +/-n-p/sup +/ structure. The p/sup +/ electrodes are reverse-biased to deplete the gap between the electrodes. When the depletion regions of the two p/sup +/-n junctions meet, a lateral current flows. Its magnitude is determined by the potential barrier in the gap. The electric field accompanying a traveling SAW penetrates into the depleted gap and modulates the potential barrier and therefore the biased detector current. The output current signal depends on the bias conditions of the detector current. This novel detector can be used to realize current-controlled taps in programmable filters. Monolithic test devices operating at a frequency of 80 MHz were realized in a ZnO-SiO/sub 2/-Si layered structure with a 9- mu m-thick epilayer of 20 Omega cm, a 0.1- mu m-thick oxide layer, and a 10- mu m-thick ZnO layer.<<ETX>>","PeriodicalId":263198,"journal":{"name":"IEEE 1988 Ultrasonics Symposium Proceedings.","volume":"181 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1988-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122789143","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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