Pub Date : 2000-10-22DOI: 10.1109/ULTSYM.2000.921552
T. Ritter, K. Shung, J. Cannata, T. Shrout
30 MHz composite linear arrays with 48 elements were designed, fabricated, and tested. Bandwidths of 60%, low crosstalk and insertion loss, and electrical impedance matching to 50 ohms were achieved. Images of a phantom and a human eye were acquired, with the phantom image demonstrating lateral and axial resolutions of 100 microns. A simpler, non-composite array incorporating lead-titanate elements was also fabricated. Test results demonstrated that the more complicated composite design is superior, a result attributed primarily to the low permittivity of the lead-titanate elements.
{"title":"High frequency ultrasound arrays for medical imaging","authors":"T. Ritter, K. Shung, J. Cannata, T. Shrout","doi":"10.1109/ULTSYM.2000.921552","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.921552","url":null,"abstract":"30 MHz composite linear arrays with 48 elements were designed, fabricated, and tested. Bandwidths of 60%, low crosstalk and insertion loss, and electrical impedance matching to 50 ohms were achieved. Images of a phantom and a human eye were acquired, with the phantom image demonstrating lateral and axial resolutions of 100 microns. A simpler, non-composite array incorporating lead-titanate elements was also fabricated. Test results demonstrated that the more complicated composite design is superior, a result attributed primarily to the low permittivity of the lead-titanate elements.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117097511","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 : 2000-10-22DOI: 10.1109/ULTSYM.2000.922682
R. Pastore, A. Ballato, J. Kosinski, H. Cui
This paper discusses a new technique to characterize lossy piezoelectric materials. This new method uses a complex frequency to stimulate a resonator's true resonant point. Parameters that are acquired from the characterization are the material attenuation constant, the impedance at the resonant frequency, an equivalent resistance for circuit modeling and an acoustic viscosity. Knowledge of this information can be very useful to circuit designers and material manufacturers. A nice feature of this technique is that it is easily implemented using and arbitrary waveform generator, a PC with data analysis/acquisition software and an oscilloscope.
{"title":"Characterizing piezoceramic material using complex frequency excitation","authors":"R. Pastore, A. Ballato, J. Kosinski, H. Cui","doi":"10.1109/ULTSYM.2000.922682","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.922682","url":null,"abstract":"This paper discusses a new technique to characterize lossy piezoelectric materials. This new method uses a complex frequency to stimulate a resonator's true resonant point. Parameters that are acquired from the characterization are the material attenuation constant, the impedance at the resonant frequency, an equivalent resistance for circuit modeling and an acoustic viscosity. Knowledge of this information can be very useful to circuit designers and material manufacturers. A nice feature of this technique is that it is easily implemented using and arbitrary waveform generator, a PC with data analysis/acquisition software and an oscilloscope.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129500077","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 : 2000-10-22DOI: 10.1109/ULTSYM.2000.922642
J. Tsujino, T. Ueoka, T. Sano, S. Tanaka
Complex vibration ultrasonic lap spot welding systems of 100 kHz are studied. The complex vibration welding tip vibrates in elliptical locus. Welding characteristics of 100 kHz, 60 kHz, 40 kHz and 27 kHz complex vibration systems with a longitudinal-torsional vibration converter were compared using aluminum plate specimens. Aluminum plates were welded independent to the directions between welding tip vibration direction and specimens. The vibration amplitudes of the welding systems required for obtaining sufficient weld strength become smaller, as the vibration frequencies become higher. The required vibration amplitude of aluminum plate specimens the 100 kHz system was smallest among them.
{"title":"Ultrasonic complex vibration welding system using 100 kHz one-dimensional longitudinal-torsional vibration converter","authors":"J. Tsujino, T. Ueoka, T. Sano, S. Tanaka","doi":"10.1109/ULTSYM.2000.922642","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.922642","url":null,"abstract":"Complex vibration ultrasonic lap spot welding systems of 100 kHz are studied. The complex vibration welding tip vibrates in elliptical locus. Welding characteristics of 100 kHz, 60 kHz, 40 kHz and 27 kHz complex vibration systems with a longitudinal-torsional vibration converter were compared using aluminum plate specimens. Aluminum plates were welded independent to the directions between welding tip vibration direction and specimens. The vibration amplitudes of the welding systems required for obtaining sufficient weld strength become smaller, as the vibration frequencies become higher. The required vibration amplitude of aluminum plate specimens the 100 kHz system was smallest among them.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128319506","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 : 2000-10-22DOI: 10.1109/ULTSYM.2000.922576
L. Maurer, W. Schelmbauer, H. Pretl, Z. Boos, R. Weigel, A. Springer
This paper presents the influence of signal filtering on the performance of a W-CDMA receiver suitable for the 3/sup rd/ Generation Partnership Project (3GPP) Frequency Division Duplex (FDD) mode. The impact of adjacent channel selectivity and inchannel distortions introduced by the filter is investigated. An evaluation of these parameters is especially important for IF-SAW filter design.
{"title":"Impact of IF-SAW filtering on the performance of a W-CDMA receiver","authors":"L. Maurer, W. Schelmbauer, H. Pretl, Z. Boos, R. Weigel, A. Springer","doi":"10.1109/ULTSYM.2000.922576","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.922576","url":null,"abstract":"This paper presents the influence of signal filtering on the performance of a W-CDMA receiver suitable for the 3/sup rd/ Generation Partnership Project (3GPP) Frequency Division Duplex (FDD) mode. The impact of adjacent channel selectivity and inchannel distortions introduced by the filter is investigated. An evaluation of these parameters is especially important for IF-SAW filter design.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129017916","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 : 2000-10-22DOI: 10.1109/ULTSYM.2000.921608
Y. Takeuchi
There are at least 2 reasons why the author begins with the per-pixel CW-Doppler receiver array for focal plane array (FPA) architecture, One is that, in FPA for real time echo-orthography (means camera-like picture taking, not an echo-tomography (cross-section image) we are familiar with), illumination (transmission) must be non- or omni-directional, receive-only directivity determines desired-to-clutter ratio which in the case of B-mode estimated is relatively poor, however in the Doppler domain no stronger clutter than flowing fluid is expected which will cause the receive-only directivity image to be reasonable or acceptable. The other is that CW-Doppler per-channel electronics can be so simple as we experienced in the fetal heart beat detector even for personal use. The philosophy of the FPA essentially is to have no "beam-forming" business at all, which can be done either by lens or element directivity, the simplicity of channel (per pixel) electronics is inevitable and essential.
{"title":"Focal plane array Doppler imaging with per-pixel CW-Doppler receiver array","authors":"Y. Takeuchi","doi":"10.1109/ULTSYM.2000.921608","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.921608","url":null,"abstract":"There are at least 2 reasons why the author begins with the per-pixel CW-Doppler receiver array for focal plane array (FPA) architecture, One is that, in FPA for real time echo-orthography (means camera-like picture taking, not an echo-tomography (cross-section image) we are familiar with), illumination (transmission) must be non- or omni-directional, receive-only directivity determines desired-to-clutter ratio which in the case of B-mode estimated is relatively poor, however in the Doppler domain no stronger clutter than flowing fluid is expected which will cause the receive-only directivity image to be reasonable or acceptable. The other is that CW-Doppler per-channel electronics can be so simple as we experienced in the fetal heart beat detector even for personal use. The philosophy of the FPA essentially is to have no \"beam-forming\" business at all, which can be done either by lens or element directivity, the simplicity of channel (per pixel) electronics is inevitable and essential.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130325987","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 : 2000-10-22DOI: 10.1109/ULTSYM.2000.921576
C. Fournier, S. Lori Bridal, P. Laugier, G. Berger
Measurements of ultrasound integrated backscatter (IBS) and frequency dependence of backscatter (n) can be used to characterize tissue composition and structure. Their high resolution estimation and presentation in quantitative images could further help evaluate local variations in tissue composition. In this work, local estimates of IBS and n are made using 20-MHz radio frequency (RF) data acquired in skin in vivo, and used to construct parametric images. Comparison is made between global estimates (made directly from a block of RF data) and the average of the local estimates over matched regions of interest in parametric images. IBS estimated by the local technique presents a mean bias of -1.05 dB in comparison with global estimates whereas local estimates of n did not demonstrate bias. Sensitivity to measurement depths in the dermis and pressure of the probe against the skin identified with global estimates was maintained with local estimates.
{"title":"Comparison of global and local estimations of ultrasonic parameters at 20 MHz: in vivo normal skin","authors":"C. Fournier, S. Lori Bridal, P. Laugier, G. Berger","doi":"10.1109/ULTSYM.2000.921576","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.921576","url":null,"abstract":"Measurements of ultrasound integrated backscatter (IBS) and frequency dependence of backscatter (n) can be used to characterize tissue composition and structure. Their high resolution estimation and presentation in quantitative images could further help evaluate local variations in tissue composition. In this work, local estimates of IBS and n are made using 20-MHz radio frequency (RF) data acquired in skin in vivo, and used to construct parametric images. Comparison is made between global estimates (made directly from a block of RF data) and the average of the local estimates over matched regions of interest in parametric images. IBS estimated by the local technique presents a mean bias of -1.05 dB in comparison with global estimates whereas local estimates of n did not demonstrate bias. Sensitivity to measurement depths in the dermis and pressure of the probe against the skin identified with global estimates was maintained with local estimates.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126689402","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 : 2000-10-22DOI: 10.1109/ULTSYM.2000.921502
S. Sherrit, S. Leary, Y. Bar-Cohen, B. Dolgin, R. Tasker
Inversion techniques to determine the complex material constants from the impedance data of a zero bond-length stack resonator are studied. The impedance equation examined in this paper is based on the derivation by Martin [G.E. Martin, JASA, 36, pp. 1496-1506, 1964]. The asymptotic solutions for the case where the number of layers n is large (n>8) and n small (n/spl les/2) are presented in terms of the complex material constants of the piezoelectric. When n =1 or 2, it is shown that the wave speed in the stack is determined by the open circuit elastic constant S/sup D//sub 33/. In the limit of large n, the wave speed is determined by the short circuit elastic constant S/sup E//sub 33/. Techniques to invert the impedance data to determine complex material constants are presented for all values of n. The error associated with using the impedance equations derived from fully short and fully open electrical boundary conditions is investigated. Since the model is based on material properties rather than circuit constants, it allows for the direct evaluation of specific aging or degradation mechanisms.
{"title":"Analysis of the impedance resonance of piezoelectric stacks","authors":"S. Sherrit, S. Leary, Y. Bar-Cohen, B. Dolgin, R. Tasker","doi":"10.1109/ULTSYM.2000.921502","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.921502","url":null,"abstract":"Inversion techniques to determine the complex material constants from the impedance data of a zero bond-length stack resonator are studied. The impedance equation examined in this paper is based on the derivation by Martin [G.E. Martin, JASA, 36, pp. 1496-1506, 1964]. The asymptotic solutions for the case where the number of layers n is large (n>8) and n small (n/spl les/2) are presented in terms of the complex material constants of the piezoelectric. When n =1 or 2, it is shown that the wave speed in the stack is determined by the open circuit elastic constant S/sup D//sub 33/. In the limit of large n, the wave speed is determined by the short circuit elastic constant S/sup E//sub 33/. Techniques to invert the impedance data to determine complex material constants are presented for all values of n. The error associated with using the impedance equations derived from fully short and fully open electrical boundary conditions is investigated. Since the model is based on material properties rather than circuit constants, it allows for the direct evaluation of specific aging or degradation mechanisms.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129283469","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 : 2000-10-22DOI: 10.1109/ULTSYM.2000.922669
Tat-Hean Gan, David A. Hutchins, D. Billson, F. C. Wong
Ultrasonic tomographic imaging has been performed on a highly-attenuating filled hydroxyl-terminated polybutadiene, cast into a steel case. Extremely low signal levels due to the attenuation and scattering properties of the polymer were present. Complications also arose from high amplitude guided waves within the steel case, which tended to mask directly-transmitted signals through the propellant. These were solved using specially-designed and pulse-compression signal processing. Images will be presented to demonstrate the technique.
{"title":"Ultrasonic tomographic imaging of an encased highly-attenuating solid media","authors":"Tat-Hean Gan, David A. Hutchins, D. Billson, F. C. Wong","doi":"10.1109/ULTSYM.2000.922669","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.922669","url":null,"abstract":"Ultrasonic tomographic imaging has been performed on a highly-attenuating filled hydroxyl-terminated polybutadiene, cast into a steel case. Extremely low signal levels due to the attenuation and scattering properties of the polymer were present. Complications also arose from high amplitude guided waves within the steel case, which tended to mask directly-transmitted signals through the propellant. These were solved using specially-designed and pulse-compression signal processing. Images will be presented to demonstrate the technique.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123860109","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 : 2000-10-22DOI: 10.1109/ULTSYM.2000.921668
F. R. Pereira, J. C. Machado, F. Foster
Temperature induced time shift of backscattered ultrasound is used to probe the temperature dependence of the speed of sound, /spl part/c//spl part/T. An Ultrasound Biomicroscope (UBM), with a PVDF transducer (center frequency=50.0 MHz), and a temperature controlled micropositioning sample cell was used. RF-backscattered signals were collected at 5 fixed temperatures of the bath, starting with 36/spl deg/C and in steps of 1/spl deg/C. The experimental results for the mean (/spl plusmn/ one standard deviation) of /spl part/c//spl part/T, in m/s/spl middot//spl deg/C, from the wall of human coronary arteries obtained at autopsy of 8 different samples from 4 individuals, were 2.20 (/spl plusmn/1.95), 4.32 (/spl plusmn/0.84) and -2.26 (/spl plusmn/1.33) for intima, media and adventitia layers, respectively. At the intima layer, /spl part/c//spl part/T appeared to decrease, from 4.29 to -0.05 m/s/spl middot//spl deg/C, as the disease progressed from mild intimal thickening to a more atherosclerotic state.
{"title":"In vitro ultrasound characterization of coronary arteries using temperature dependent wave speed","authors":"F. R. Pereira, J. C. Machado, F. Foster","doi":"10.1109/ULTSYM.2000.921668","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.921668","url":null,"abstract":"Temperature induced time shift of backscattered ultrasound is used to probe the temperature dependence of the speed of sound, /spl part/c//spl part/T. An Ultrasound Biomicroscope (UBM), with a PVDF transducer (center frequency=50.0 MHz), and a temperature controlled micropositioning sample cell was used. RF-backscattered signals were collected at 5 fixed temperatures of the bath, starting with 36/spl deg/C and in steps of 1/spl deg/C. The experimental results for the mean (/spl plusmn/ one standard deviation) of /spl part/c//spl part/T, in m/s/spl middot//spl deg/C, from the wall of human coronary arteries obtained at autopsy of 8 different samples from 4 individuals, were 2.20 (/spl plusmn/1.95), 4.32 (/spl plusmn/0.84) and -2.26 (/spl plusmn/1.33) for intima, media and adventitia layers, respectively. At the intima layer, /spl part/c//spl part/T appeared to decrease, from 4.29 to -0.05 m/s/spl middot//spl deg/C, as the disease progressed from mild intimal thickening to a more atherosclerotic state.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123910769","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 : 2000-10-22DOI: 10.1109/ULTSYM.2000.922498
Xueding Wang, D. Zhang, Gang Qiu
With unidirectional reflections distributed among the transducer, transduction efficiencies of cells in a SPUDT are not equal. So classical source strength function is not suitable for SPUDT design, because they will cause the distortion of the spectrum and phase near the center frequency of the transducer. In this paper a novel weighting method, Effective Transduction Weighting (ETW) for SPUDT are presented that could remedy the drawbacks of classical weighting functions well. Both theoretical and experimental results shows ETW method is able to improve the filter characters and the design flexibility. For an simulation example, the SPUDT filter made up of 380 DART cells with ETW processed Hamming and Sinc weighting on ST-X cut quartz, the shape factor (-40 dB: -3 dB) is 1.8:1, and the shapes of spectrum are symmetry with the center frequency (200 MHz), including sidelobes and ripples in passband.
{"title":"Effective transduction weighting (ETW) method for SPUDT","authors":"Xueding Wang, D. Zhang, Gang Qiu","doi":"10.1109/ULTSYM.2000.922498","DOIUrl":"https://doi.org/10.1109/ULTSYM.2000.922498","url":null,"abstract":"With unidirectional reflections distributed among the transducer, transduction efficiencies of cells in a SPUDT are not equal. So classical source strength function is not suitable for SPUDT design, because they will cause the distortion of the spectrum and phase near the center frequency of the transducer. In this paper a novel weighting method, Effective Transduction Weighting (ETW) for SPUDT are presented that could remedy the drawbacks of classical weighting functions well. Both theoretical and experimental results shows ETW method is able to improve the filter characters and the design flexibility. For an simulation example, the SPUDT filter made up of 380 DART cells with ETW processed Hamming and Sinc weighting on ST-X cut quartz, the shape factor (-40 dB: -3 dB) is 1.8:1, and the shapes of spectrum are symmetry with the center frequency (200 MHz), including sidelobes and ripples in passband.","PeriodicalId":350384,"journal":{"name":"2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123200769","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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