Pub Date : 1997-10-05DOI: 10.1109/ULTSYM.1997.663113
R. Leblanc, A. Maslouhi, D. Forsyth, A. Fahr, A. Moreau
The effect of exposure of 7050 aluminum alloy to heat damage has been studied using ultrasonic techniques. Contact, immersion, and laser ultrasonic techniques were used. The relationships of ultrasonic attenuation with static material properties and material microstructure were evaluated. It was shown that attenuation measurements at high frequencies (>20 MHz) can provide an indication of material microstructure and thus mechanical properties of 7050 aluminum.
{"title":"Ultrasonic assessment of heat-damage in 7050 aluminum alloy","authors":"R. Leblanc, A. Maslouhi, D. Forsyth, A. Fahr, A. Moreau","doi":"10.1109/ULTSYM.1997.663113","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.663113","url":null,"abstract":"The effect of exposure of 7050 aluminum alloy to heat damage has been studied using ultrasonic techniques. Contact, immersion, and laser ultrasonic techniques were used. The relationships of ultrasonic attenuation with static material properties and material microstructure were evaluated. It was shown that attenuation measurements at high frequencies (>20 MHz) can provide an indication of material microstructure and thus mechanical properties of 7050 aluminum.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73343498","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 : 1997-10-05DOI: 10.1109/ULTSYM.1997.663336
D. Vilkomerson, D. Lyons, T. Chilipka, P. Lopath, K. Shung
Diffraction grating transducers, like optical diffraction gratings, produce beams at different angles for different frequencies. They transmit and receive what would be considered the grating lobe for conventional array transducers. Diffraction-grating transducers were developed to produce multiple beams at known angles so that angle-independent Doppler measurements could be made. The theory of operation of first and higher-order diffraction-grating transducers is presented, including the parameters that affect beam resolution and operating distance. A method to fabricate these transducers like composite transducers is outlined, and experimental results presented.
{"title":"Diffraction-grating transducers","authors":"D. Vilkomerson, D. Lyons, T. Chilipka, P. Lopath, K. Shung","doi":"10.1109/ULTSYM.1997.663336","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.663336","url":null,"abstract":"Diffraction grating transducers, like optical diffraction gratings, produce beams at different angles for different frequencies. They transmit and receive what would be considered the grating lobe for conventional array transducers. Diffraction-grating transducers were developed to produce multiple beams at known angles so that angle-independent Doppler measurements could be made. The theory of operation of first and higher-order diffraction-grating transducers is presented, including the parameters that affect beam resolution and operating distance. A method to fabricate these transducers like composite transducers is outlined, and experimental results presented.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75263146","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 : 1997-10-05DOI: 10.1109/ULTSYM.1997.663337
Y. Lin, J. M. Dodson, J. D. Hamilton, J. Kluiwstra, C. Cain, K. Grosh
In this paper, combined finite element simulations and experimental measurements are used to study the dynamic response of fluid-loaded piezoelectric element for phased array design. An efficient and robust numerical methodology for 3D coupled structural acoustic model is developed. A confocal Fabry-Perot laser interferometer is used to measure the surface response. Comparisons are made between numerical results and experimental results. Important features in the transducer design such as radiation patterns in the fluid domain, as well as the electromechanical behavior of the transducer, are evaluated.
{"title":"Theory and experiment for the design of piezoelectric element for phased arrays","authors":"Y. Lin, J. M. Dodson, J. D. Hamilton, J. Kluiwstra, C. Cain, K. Grosh","doi":"10.1109/ULTSYM.1997.663337","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.663337","url":null,"abstract":"In this paper, combined finite element simulations and experimental measurements are used to study the dynamic response of fluid-loaded piezoelectric element for phased array design. An efficient and robust numerical methodology for 3D coupled structural acoustic model is developed. A confocal Fabry-Perot laser interferometer is used to measure the surface response. Comparisons are made between numerical results and experimental results. Important features in the transducer design such as radiation patterns in the fluid domain, as well as the electromechanical behavior of the transducer, are evaluated.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75523321","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 : 1997-10-05DOI: 10.1109/ULTSYM.1997.661758
D. Huang, S. Boucher, R. Tancrell, A. Rougeau
In recent years, multi-beam systems have gained widespread acceptance as the hydrographic surveyor's tool of choice for many reconnaissance as well as survey applications. In this discussion, we present the design and performance of a multi-beam receiver and broad beam projector for a bathymetry system which can collect data 30 times faster than a typical single beam system. Performance requirements of the receiver at 200 kHz realized with PVDF elements which produce a 3 degree beamwidth and sidelobe level of -30 dB by shading the element electrode pattern. These light weight receiving element are mounted in a precision-molded housing to create 30 contiguous beams separated 3 degrees in elevation. Data from all 30 beams are collected simultaneously, and the well-controlled beam shape and low sidelobe minimize interference between the beams. The projector, required to insonify a fan beam 2.5 degrees by 127 degrees, was constructed from 330 PZT elements to achieve a source level of 228 dB re 1 /spl mu/Pa at 1 meter at 5 kW pulse power. With this design approach, artifacts common to electronically formed beams are eliminated. This simplifies signal processing, improves system accuracy, and lowers the overall system cost. Both theoretical simulations and experimental data for the Mills' Cross configuration of the projecting and receiving elements, the system design principles, theoretical prediction, laboratory test and field measurements on various underwater topologies are presented.
近年来，多波束系统作为水文测量员在许多勘测和测量应用中的首选工具得到了广泛的认可。在这篇讨论中，我们提出了一个测深系统的多波束接收器和宽波束投影仪的设计和性能，它的数据收集速度比典型的单波束系统快30倍。使用PVDF元件实现200 kHz时的接收机性能要求，通过遮蔽元件电极图案，产生3度波束宽度和-30 dB的副瓣电平。这些重量轻的接收元件安装在一个精密模制的外壳中，形成30个连续的梁，在3度的仰角上分开。同时采集30个波束的数据，良好的波束形状控制和低旁瓣最大限度地减少了波束之间的干扰。投影仪需要对2.5度乘127度的风扇光束进行消谐，由330 PZT元件构成，在5 kW脉冲功率下，在1米处达到228 dB re /spl mu/Pa的源电平。采用这种设计方法，消除了电子成形光束常见的伪影。这简化了信号处理，提高了系统精度，降低了整体系统成本。介绍了发射和接收单元的米尔斯交叉构型的理论模拟和实验数据，系统设计原则，理论预测，实验室测试和各种水下拓扑的现场测量。
{"title":"The design of sidelobe suppressed PVDF beamforming elements for high performance underwater multi-beam swath transducers","authors":"D. Huang, S. Boucher, R. Tancrell, A. Rougeau","doi":"10.1109/ULTSYM.1997.661758","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.661758","url":null,"abstract":"In recent years, multi-beam systems have gained widespread acceptance as the hydrographic surveyor's tool of choice for many reconnaissance as well as survey applications. In this discussion, we present the design and performance of a multi-beam receiver and broad beam projector for a bathymetry system which can collect data 30 times faster than a typical single beam system. Performance requirements of the receiver at 200 kHz realized with PVDF elements which produce a 3 degree beamwidth and sidelobe level of -30 dB by shading the element electrode pattern. These light weight receiving element are mounted in a precision-molded housing to create 30 contiguous beams separated 3 degrees in elevation. Data from all 30 beams are collected simultaneously, and the well-controlled beam shape and low sidelobe minimize interference between the beams. The projector, required to insonify a fan beam 2.5 degrees by 127 degrees, was constructed from 330 PZT elements to achieve a source level of 228 dB re 1 /spl mu/Pa at 1 meter at 5 kW pulse power. With this design approach, artifacts common to electronically formed beams are eliminated. This simplifies signal processing, improves system accuracy, and lowers the overall system cost. Both theoretical simulations and experimental data for the Mills' Cross configuration of the projecting and receiving elements, the system design principles, theoretical prediction, laboratory test and field measurements on various underwater topologies are presented.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74330574","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 : 1997-10-05DOI: 10.1109/ULTSYM.1997.661741
E. Kuhnicke
For ultrasonic problems, an optimized approximation method based on a separation approach in connection with integral transform methods and a point source synthesis, was developed to calculate the transducer generated sound field in layered media with curved interfaces. The results are compared with calculation results obtained from an exact method.
{"title":"Optimized calculation of transient wave fields for transducer design","authors":"E. Kuhnicke","doi":"10.1109/ULTSYM.1997.661741","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.661741","url":null,"abstract":"For ultrasonic problems, an optimized approximation method based on a separation approach in connection with integral transform methods and a point source synthesis, was developed to calculate the transducer generated sound field in layered media with curved interfaces. The results are compared with calculation results obtained from an exact method.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78727794","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 : 1997-10-05DOI: 10.1109/ULTSYM.1997.661782
S. Hakim, K. Watkin, M. Elahi, L. Lessard
There is significant variation in the thickness of cranio-maxillofacial bone. Bone thickness is essential information that enhances the success and safety of operations in this area. Complications can result from inaccurate predictions of bone thickness including: haemorrhage, infection and brain injury. Current assessments of bone thickness with plain X-rays and CT scans are expensive, not accurate, not portable nor of use in the operating room. Acoustic measurements of skull bone thickness were determined and compared to direct measurements using digital callipers. Comparisons between these data showed no statistical difference (t-test, P=.576; Pearson correlation, r>.998) and suggested that A-mode ultrasound could be a reliable tool for assessing the thickness of the calvarium for preoperative and intraoperative use.
{"title":"A new predictive ultrasound modality of cranial bone thickness","authors":"S. Hakim, K. Watkin, M. Elahi, L. Lessard","doi":"10.1109/ULTSYM.1997.661782","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.661782","url":null,"abstract":"There is significant variation in the thickness of cranio-maxillofacial bone. Bone thickness is essential information that enhances the success and safety of operations in this area. Complications can result from inaccurate predictions of bone thickness including: haemorrhage, infection and brain injury. Current assessments of bone thickness with plain X-rays and CT scans are expensive, not accurate, not portable nor of use in the operating room. Acoustic measurements of skull bone thickness were determined and compared to direct measurements using digital callipers. Comparisons between these data showed no statistical difference (t-test, P=.576; Pearson correlation, r>.998) and suggested that A-mode ultrasound could be a reliable tool for assessing the thickness of the calvarium for preoperative and intraoperative use.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78395701","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 : 1997-10-05DOI: 10.1109/ULTSYM.1997.661817
K. Hynynen
The development of modern imaging techniques has made it possible to use focused ultrasound for the accurate destruction of deep tissues. In addition to targeting, imaging techniques allow the temperature elevation and cavitation events to be detected and potentially quantified. These techniques have made treatment control possible to a degree such it may soon be possible to perform noninvasive tissue destruction with at least the same precision as open surgery. In addition, new experimental evidence has expanded the potential use of ultrasound to vascular occlusions, targeting and activating chemicals, providing access to the brain by opening the blood brain barrier, targeting gene therapy, etc. Overall, the potential number of therapeutic uses of ultrasound is expanding rapidly beyond the tissue destruction that has been investigated so far. Here, some of this progress is reviewed. In addition, new results are shown that demonstrate the potential for the transskull ultrasound therapy.
{"title":"Review of ultrasound therapy","authors":"K. Hynynen","doi":"10.1109/ULTSYM.1997.661817","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.661817","url":null,"abstract":"The development of modern imaging techniques has made it possible to use focused ultrasound for the accurate destruction of deep tissues. In addition to targeting, imaging techniques allow the temperature elevation and cavitation events to be detected and potentially quantified. These techniques have made treatment control possible to a degree such it may soon be possible to perform noninvasive tissue destruction with at least the same precision as open surgery. In addition, new experimental evidence has expanded the potential use of ultrasound to vascular occlusions, targeting and activating chemicals, providing access to the brain by opening the blood brain barrier, targeting gene therapy, etc. Overall, the potential number of therapeutic uses of ultrasound is expanding rapidly beyond the tissue destruction that has been investigated so far. Here, some of this progress is reviewed. In addition, new results are shown that demonstrate the potential for the transskull ultrasound therapy.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78136010","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 : 1997-10-05DOI: 10.1109/ULTSYM.1997.661824
J. Spoo, J. Jenne, K. Jochle, P. Huber, W. Lorenz, M. Wannenmacher, J. Debus
The object of the authors' investigations is the in vivo-activation of photosensitizing agents by high energy ultrasound (HIFU) in order to minimize side effects and to increase penetration depth of photodynamic treatments. Animal experiments were carried out using the Dunning rat prostrate adenocarcinoma R3327-AT1 in Copenhagen rats. Macroscopic treatment response was evaluated and biologically graded. The authors were able to assess a synergistic tissue interaction of HIFU (f=1.18 MHz, I=3530 W/cm/sup 2/) and hematoporphyrin-derivative.
{"title":"In vivo-activation of photodynamic hematoporphyrin-derivative (HPD) by HIFU","authors":"J. Spoo, J. Jenne, K. Jochle, P. Huber, W. Lorenz, M. Wannenmacher, J. Debus","doi":"10.1109/ULTSYM.1997.661824","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.661824","url":null,"abstract":"The object of the authors' investigations is the in vivo-activation of photosensitizing agents by high energy ultrasound (HIFU) in order to minimize side effects and to increase penetration depth of photodynamic treatments. Animal experiments were carried out using the Dunning rat prostrate adenocarcinoma R3327-AT1 in Copenhagen rats. Macroscopic treatment response was evaluated and biologically graded. The authors were able to assess a synergistic tissue interaction of HIFU (f=1.18 MHz, I=3530 W/cm/sup 2/) and hematoporphyrin-derivative.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79379683","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 : 1997-10-05DOI: 10.1109/ULTSYM.1997.662990
B. Jakoby, M. Vellekoop
Periodic structures utilized as transducer or reflector elements play an important role in microacoustic wave devices. Such structures can be described using approximate analytical models. However, to obtain the accuracy required for reliable device simulation, numerical methods have to be employed. In this contribution we present an efficient numerical approach to calculate the dispersion curves associated with microacoustic modes propagating in periodic structures. The computational efficiency is related to the utilization of the Fast Fourier Transform (FFT) algorithm in a hybrid Method of Moments (MoM)/Mode Matching analysis. From the obtained dispersion curves characteristic parameters such as the stopband width can be obtained which can be used in a coupling-of-modes model of the structure.
{"title":"Efficient analysis of periodic structures in microacoustic devices","authors":"B. Jakoby, M. Vellekoop","doi":"10.1109/ULTSYM.1997.662990","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.662990","url":null,"abstract":"Periodic structures utilized as transducer or reflector elements play an important role in microacoustic wave devices. Such structures can be described using approximate analytical models. However, to obtain the accuracy required for reliable device simulation, numerical methods have to be employed. In this contribution we present an efficient numerical approach to calculate the dispersion curves associated with microacoustic modes propagating in periodic structures. The computational efficiency is related to the utilization of the Fast Fourier Transform (FFT) algorithm in a hybrid Method of Moments (MoM)/Mode Matching analysis. From the obtained dispersion curves characteristic parameters such as the stopband width can be obtained which can be used in a coupling-of-modes model of the structure.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81575811","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 : 1997-10-05DOI: 10.1109/ULTSYM.1997.663013
M. Weihnacht, Kurt Dr. Franke, K. Kammer, R. Kunze, Hagen Schmidt
Three original methods, developed and used for the characterization of SAW materials and devices, are presented: an electric scanning force microscope, a laser induced SAW pulse propagation method, and an optical glass fibre interferometer. The electric scanning force microscope enables to map dielectric and piezoelectric properties in nanoscale. Two examples of its use in developing SAW thin film solutions are shown: PZT layers on Si and laser deposited LiNbO/sub 3/ layers on sapphire. The laser induced SAW pulse technique is shown to be a useful method to evaluate the mechanical properties of thin coatings in SAW preparation techniques and to determine unknown material constants of new substrate materials. The optical interferometer has been developed in such a way that the SAW velocity can be determined with an accuracy of 10/sup -5/ within transducer and reflector grating structures. This property has been used to determine the key parameters of potential materials for SAW waveguide resonator filters.
{"title":"High precision characterization of SAW materials and devices","authors":"M. Weihnacht, Kurt Dr. Franke, K. Kammer, R. Kunze, Hagen Schmidt","doi":"10.1109/ULTSYM.1997.663013","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.663013","url":null,"abstract":"Three original methods, developed and used for the characterization of SAW materials and devices, are presented: an electric scanning force microscope, a laser induced SAW pulse propagation method, and an optical glass fibre interferometer. The electric scanning force microscope enables to map dielectric and piezoelectric properties in nanoscale. Two examples of its use in developing SAW thin film solutions are shown: PZT layers on Si and laser deposited LiNbO/sub 3/ layers on sapphire. The laser induced SAW pulse technique is shown to be a useful method to evaluate the mechanical properties of thin coatings in SAW preparation techniques and to determine unknown material constants of new substrate materials. The optical interferometer has been developed in such a way that the SAW velocity can be determined with an accuracy of 10/sup -5/ within transducer and reflector grating structures. This property has been used to determine the key parameters of potential materials for SAW waveguide resonator filters.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84274446","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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