N. Denisenko, G. Scarano, M. Matteucci, M. Pappalardo
Abstmct-A new monodomensional approximate solution of the transient acoustic field is presented, which can be easily implemented on small minicomputers. The acoustic field generated by a monodimensional source is simply expressed by a sum of a small number of terms, reducing significantly the complexity of the operations involved. The numerical results obtained with this method are remarkably in agreement with those obained through the exact convolutional method. It is shown that the proposed approximate monodimensional method can be usefully employed for the design and optimization of both linear- and sector-scanning visualization systems.
{"title":"An Approximate Solution of the Transient Acoustic Field","authors":"N. Denisenko, G. Scarano, M. Matteucci, M. Pappalardo","doi":"10.1109/T-SU.1985.31671","DOIUrl":"https://doi.org/10.1109/T-SU.1985.31671","url":null,"abstract":"Abstmct-A new monodomensional approximate solution of the transient acoustic field is presented, which can be easily implemented on small minicomputers. The acoustic field generated by a monodimensional source is simply expressed by a sum of a small number of terms, reducing significantly the complexity of the operations involved. The numerical results obtained with this method are remarkably in agreement with those obained through the exact convolutional method. It is shown that the proposed approximate monodimensional method can be usefully employed for the design and optimization of both linear- and sector-scanning visualization systems.","PeriodicalId":371797,"journal":{"name":"IEEE Transactions on Sonics and Ultrasonics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1985-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128671759","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}
Abstmet-Using a theoretical model, we establish an analytical result giving the average pressure emitted by an ultrasonic piezoelectric transmitter, the wearplate of which has a lack of parallelism between its two faces. Verification of the model’s validity is carried out hy recording the simulated and experimental responses of piezoelectric transmitters with different degrees of parallelism defect for the wearplate. This study is carried out for a quarter-wave wearplate at the resonance frequency of the piezoelectric element.
{"title":"Theoretical and Experimental Investigation of a Piezoelectric Transducer with a Nonparallel-Faced Wearplate","authors":"Y. Jayet, J. Baboux, F. Lakestani, M. Perdrix","doi":"10.1109/T-SU.1985.31673","DOIUrl":"https://doi.org/10.1109/T-SU.1985.31673","url":null,"abstract":"Abstmet-Using a theoretical model, we establish an analytical result giving the average pressure emitted by an ultrasonic piezoelectric transmitter, the wearplate of which has a lack of parallelism between its two faces. Verification of the model’s validity is carried out hy recording the simulated and experimental responses of piezoelectric transmitters with different degrees of parallelism defect for the wearplate. This study is carried out for a quarter-wave wearplate at the resonance frequency of the piezoelectric element.","PeriodicalId":371797,"journal":{"name":"IEEE Transactions on Sonics and Ultrasonics","volume":"18 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1985-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134375254","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}
{"title":"A Change at the Helm","authors":"S. Wanuga","doi":"10.1109/T-SU.1985.31667","DOIUrl":"https://doi.org/10.1109/T-SU.1985.31667","url":null,"abstract":"","PeriodicalId":371797,"journal":{"name":"IEEE Transactions on Sonics and Ultrasonics","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1985-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133784333","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}
M. Nakazawa, T. Takemae, A. Miyahara, K. Matsuyama
Abstmct-Theoretical and experimental research work on quartz temperalure sensors with doubly rotated cuts characterized by ultralinear frequency-temperature responses has been conducted. According to the experimental results, it is found that the new quartz temperature sensor has a linear frequency-temperature response and a larger frequencpsensitivity lo temperature than the ones of the previously reported. This sensor also has fast thermal time constants for the low temperature transients. NUSUAL climatic phenomena have recently had a most baffling effect on the agriculture, forestry, fishery, and industry all the world over. Therefore, it will be of much importance to make these phenomena well understood and try to present basic ideas that would hopefully lead to world-wide cooperation in coping with the problems. In meteorology, we take an interest in the three-dimensional precision and remote-sensing systems for the global temperature with respect to seawater and the atmosphere. We think that our study will be able to help establish part of those systems, for we have recently discovered a new quartz temperature sensor which exhibits a higher degree of frequency linearity over a wide temperature range compared with the previous types. What is more, it has to be pointed out that the electronic system around the temperature sensor will be much simplified without any device for linearization of frequencytemperature characteristics. The purpose of our research is to help design a sensor characterized by ultralinear frequency-temperature responses. In this paper some features of such sensors will be discussed in detail according to theoretical and experimental results. 11. THEORY Suppose a thin quartz crystal plate whose electrical, mechanical, and optical axes are defined as in the directions of x,, x?, and x3 axes, respectively, as shown in Fig. 1. We denote the direction normal to the main plane by polar
{"title":"A Study of Quartz Temperature Sensors Characterized by Ultralinear Frequency-Temperature Responses","authors":"M. Nakazawa, T. Takemae, A. Miyahara, K. Matsuyama","doi":"10.1109/T-SU.1985.31672","DOIUrl":"https://doi.org/10.1109/T-SU.1985.31672","url":null,"abstract":"Abstmct-Theoretical and experimental research work on quartz temperalure sensors with doubly rotated cuts characterized by ultralinear frequency-temperature responses has been conducted. According to the experimental results, it is found that the new quartz temperature sensor has a linear frequency-temperature response and a larger frequencpsensitivity lo temperature than the ones of the previously reported. This sensor also has fast thermal time constants for the low temperature transients. NUSUAL climatic phenomena have recently had a most baffling effect on the agriculture, forestry, fishery, and industry all the world over. Therefore, it will be of much importance to make these phenomena well understood and try to present basic ideas that would hopefully lead to world-wide cooperation in coping with the problems. In meteorology, we take an interest in the three-dimensional precision and remote-sensing systems for the global temperature with respect to seawater and the atmosphere. We think that our study will be able to help establish part of those systems, for we have recently discovered a new quartz temperature sensor which exhibits a higher degree of frequency linearity over a wide temperature range compared with the previous types. What is more, it has to be pointed out that the electronic system around the temperature sensor will be much simplified without any device for linearization of frequencytemperature characteristics. The purpose of our research is to help design a sensor characterized by ultralinear frequency-temperature responses. In this paper some features of such sensors will be discussed in detail according to theoretical and experimental results. 11. THEORY Suppose a thin quartz crystal plate whose electrical, mechanical, and optical axes are defined as in the directions of x,, x?, and x3 axes, respectively, as shown in Fig. 1. We denote the direction normal to the main plane by polar","PeriodicalId":371797,"journal":{"name":"IEEE Transactions on Sonics and Ultrasonics","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1985-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129064669","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}
The transient response of a focused array in echographic systems for imaging in medical and nondestructive evaluation applica- tions is obtained in an analytic form. The results constitute an extension of the response to a monochromatic excitation. The actual shapes of the pulses used are explicitly accounted for by means of suitable parame- ters, as the resonance frequency and the damping factor of the trans- ducers. The one- and two-way responses are evaluated through the use of the linear system theory and complex envelopes for the involved sig- nals. Gaussian-shaped envelopes, which fit most practical situations at a satisfactory amount, are considered for the pulses. Simple expres- sions in a closed form directly relate the response to the system param- eters.
{"title":"Pulsed Response of Focused Arrays in Echographic B-Mode Systems","authors":"G. Jacovitti, A. Neri, G. Scarano","doi":"10.1109/T-SU.1985.31676","DOIUrl":"https://doi.org/10.1109/T-SU.1985.31676","url":null,"abstract":"The transient response of a focused array in echographic systems for imaging in medical and nondestructive evaluation applica- tions is obtained in an analytic form. The results constitute an extension of the response to a monochromatic excitation. The actual shapes of the pulses used are explicitly accounted for by means of suitable parame- ters, as the resonance frequency and the damping factor of the trans- ducers. The one- and two-way responses are evaluated through the use of the linear system theory and complex envelopes for the involved sig- nals. Gaussian-shaped envelopes, which fit most practical situations at a satisfactory amount, are considered for the pulses. Simple expres- sions in a closed form directly relate the response to the system param- eters.","PeriodicalId":371797,"journal":{"name":"IEEE Transactions on Sonics and Ultrasonics","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1985-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115197139","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}
near-field plane-wave pulses can he used to produce a complementary uncertainty also can introduce in measurement of response pattern; i.e., response vs. frequency at a constant angle, as opposed to response vs. angle at a constant frequency. Directional am- the phase response, particularly in the megahertz freplitude and phase responses in the 1-10 MHz range have been obtained quency range [31, [51. Another possible inaccuracy is reusing this method for miniature ultrasonic hydrophones (sl mm di- lated to the effect of the temperature variations on the ameter). The pulsed waveforms measured by the hydrophone were dig- measurement of the directional phase response. More will itized and Fourier-transformed. Normalization with respect to the hydrophone’s on-axis response was accomplished by a simple spectral subtraction procedure. The angular and frequency resolutions of the technique are typically 0.25” and 100 kHz, respectively. From these data of measuring the plane-wave directivity pattern has been be said on these potential phase errors later. To eliminate these potential errors, an alternate method an effective hydrophone radius as a function of frequency can be computed more quickly and efficiently than would be possible using present practices.
{"title":"A Pulsed Near-Field Technique for Measuring the Directional Characteristics of Acoustic Receivers","authors":"G. D. Harris, D. G. Shombert","doi":"10.1109/T-SU.1985.31668","DOIUrl":"https://doi.org/10.1109/T-SU.1985.31668","url":null,"abstract":"near-field plane-wave pulses can he used to produce a complementary uncertainty also can introduce in measurement of response pattern; i.e., response vs. frequency at a constant angle, as opposed to response vs. angle at a constant frequency. Directional am- the phase response, particularly in the megahertz freplitude and phase responses in the 1-10 MHz range have been obtained quency range [31, [51. Another possible inaccuracy is reusing this method for miniature ultrasonic hydrophones (sl mm di- lated to the effect of the temperature variations on the ameter). The pulsed waveforms measured by the hydrophone were dig- measurement of the directional phase response. More will itized and Fourier-transformed. Normalization with respect to the hydrophone’s on-axis response was accomplished by a simple spectral subtraction procedure. The angular and frequency resolutions of the technique are typically 0.25” and 100 kHz, respectively. From these data of measuring the plane-wave directivity pattern has been be said on these potential phase errors later. To eliminate these potential errors, an alternate method an effective hydrophone radius as a function of frequency can be computed more quickly and efficiently than would be possible using present practices.","PeriodicalId":371797,"journal":{"name":"IEEE Transactions on Sonics and Ultrasonics","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1985-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133461221","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}
Abstmct-A surface-acoustic-wave (SAW) variable-controlled delay line (VCDL), based on two chirp filters, is discussed and a unified analysis of all such VCDL configurations is presented. The system transfer function and delay formula are derived. Although the most general SAW-VCDL configuration consists of three controlling signals, it is shown that the delay introduced by the system depends only on the frequency of the signal that serves as an input to the mixer between the two chirp filters. The other two controlling signals affect the center frequency of the output spectrum and the system bandwidth, but not the delay. A new configuration of a SAW-VCDL, which uses two identical chirp filters, is then proposed and analyzed for two types of controlling signals. Laboratory experimental results are provided to support the analysis.
{"title":"A Unified Approach to the Design of Voltage-Controlled SAW Delay Lines","authors":"H. Messer, Y. Bar-Ness","doi":"10.1109/T-SU.1985.31670","DOIUrl":"https://doi.org/10.1109/T-SU.1985.31670","url":null,"abstract":"Abstmct-A surface-acoustic-wave (SAW) variable-controlled delay line (VCDL), based on two chirp filters, is discussed and a unified analysis of all such VCDL configurations is presented. The system transfer function and delay formula are derived. Although the most general SAW-VCDL configuration consists of three controlling signals, it is shown that the delay introduced by the system depends only on the frequency of the signal that serves as an input to the mixer between the two chirp filters. The other two controlling signals affect the center frequency of the output spectrum and the system bandwidth, but not the delay. A new configuration of a SAW-VCDL, which uses two identical chirp filters, is then proposed and analyzed for two types of controlling signals. Laboratory experimental results are provided to support the analysis.","PeriodicalId":371797,"journal":{"name":"IEEE Transactions on Sonics and Ultrasonics","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1985-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126222388","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 : 1985-11-01DOI: 10.1109/ULTSYM.1984.198447
E. Chow, J. Brown
Thermal transient behavior of quartz resonators has been the subject of various experimental and theoretical studies. In this paper, we present a combined theoretical-experimental approach to modeling thermal transient response of quartz resonators. The essential steps of this approach consists of first deriving a versatile model stmcture based on physical principles, and then fully specifying the model by identifying the model parameters using data collected from thermal transient experiments. Results of applying this modeling approach to a quartz resonator is also discussed.
{"title":"Dynamic Models for Quartz-Resonator Thermal Transient Response","authors":"E. Chow, J. Brown","doi":"10.1109/ULTSYM.1984.198447","DOIUrl":"https://doi.org/10.1109/ULTSYM.1984.198447","url":null,"abstract":"Thermal transient behavior of quartz resonators has been the subject of various experimental and theoretical studies. In this paper, we present a combined theoretical-experimental approach to modeling thermal transient response of quartz resonators. The essential steps of this approach consists of first deriving a versatile model stmcture based on physical principles, and then fully specifying the model by identifying the model parameters using data collected from thermal transient experiments. Results of applying this modeling approach to a quartz resonator is also discussed.","PeriodicalId":371797,"journal":{"name":"IEEE Transactions on Sonics and Ultrasonics","volume":"54 3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1985-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116609494","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}
Scanning electron microscopy (SEM) observations of mode shapes of flexural, anharmonic and thickness-shear modes of vibrations in rectangular and circular disk quartz resonators have been pre- sented. Flexural vibrations haw been observed propagatng both along and perpendicular to the x-axis of the crystal. In only high-frequency (30-MHz, third overtone) thin unbeveled circular disk resonators, evi- dence of circular flexural waves is found for the first time. Beveling of these resonators makes the flexural waves linear, and they propagate only along the x-axis. The studies suggest the immediate application in time and frequency standardization in using thicker quartz crystal res- onators for obtaining purer thickness vibrations relatively free from flexural components and ewcitng resonators in higher overtones to achieve high frequencies and higher stabilit) index. Crystal resonators (plates or disks) are capable of vibrating in different modes. Primarily, these modes can cause extensional. flexural, or shear (thickness or face) motions. In the actual practice of using bonded resonators, due to finite dimensions and reflection from boundaries, there results a complex elastic coupling of these different modes which gives rise to a host of frequencies that a crys- tal resonator is capable of vibrating at. A variety of experimental techniques (l) have been used for mode identification and also to suppress the undesired modes due to the underlying urge and the associated requirement of using a crystal resonator in the purest possible mode of vibration in frequency-control instrumentation. Among the new sophisticated experimental techniques. scanning electron microscopy (SEM) has been used for about a decade to study vibrations in quartz crystals (2)-(4). In the technique, an electron beam (usually accelerated to about 2 kV) is used to monitor the electrical potential distribution onto the resonator surface, which is due to its piezoelectric effect. The SEM micrographs thus exhibit a particular mode of vibrations of the crystal in operation. At high magnification (2000-5000X), where only a very small area of the surface is examined, the micrographs represent an uniform electric potential and the smearing in the patterns can be used either to measure the displacement or track the direction of vibrations. The SEM has been used in the recent past by Bahadur er d., (5)-(7) and Bahadur and Parshad (3), (4) to monitor the energy trapping and its absence in some resonator disks. Also, some com- plex SEM micrographs were reported occurring both for rectangu- lar plates and circular disks. In some cases of rectangular plates. a regular periodic band structure was attributed (l), 181 to represent appropriate overtones of flexural vibrations having their resonance frequency close to the fundamental thickness-shear vibrations. It was observed that the propagation of flexural vibrations was parallel to the x-axis of the crystal. In the measurements (l). (g) for t
{"title":"SEM Observations of Mode Shapes of Flexural, Anharmonic, and Thickness-Shear Vibrations in Quartz Resonators","authors":"H. Bahadur, R. Parshad","doi":"10.1109/T-SU.1985.31677","DOIUrl":"https://doi.org/10.1109/T-SU.1985.31677","url":null,"abstract":"Scanning electron microscopy (SEM) observations of mode shapes of flexural, anharmonic and thickness-shear modes of vibrations in rectangular and circular disk quartz resonators have been pre- sented. Flexural vibrations haw been observed propagatng both along and perpendicular to the x-axis of the crystal. In only high-frequency (30-MHz, third overtone) thin unbeveled circular disk resonators, evi- dence of circular flexural waves is found for the first time. Beveling of these resonators makes the flexural waves linear, and they propagate only along the x-axis. The studies suggest the immediate application in time and frequency standardization in using thicker quartz crystal res- onators for obtaining purer thickness vibrations relatively free from flexural components and ewcitng resonators in higher overtones to achieve high frequencies and higher stabilit) index. Crystal resonators (plates or disks) are capable of vibrating in different modes. Primarily, these modes can cause extensional. flexural, or shear (thickness or face) motions. In the actual practice of using bonded resonators, due to finite dimensions and reflection from boundaries, there results a complex elastic coupling of these different modes which gives rise to a host of frequencies that a crys- tal resonator is capable of vibrating at. A variety of experimental techniques (l) have been used for mode identification and also to suppress the undesired modes due to the underlying urge and the associated requirement of using a crystal resonator in the purest possible mode of vibration in frequency-control instrumentation. Among the new sophisticated experimental techniques. scanning electron microscopy (SEM) has been used for about a decade to study vibrations in quartz crystals (2)-(4). In the technique, an electron beam (usually accelerated to about 2 kV) is used to monitor the electrical potential distribution onto the resonator surface, which is due to its piezoelectric effect. The SEM micrographs thus exhibit a particular mode of vibrations of the crystal in operation. At high magnification (2000-5000X), where only a very small area of the surface is examined, the micrographs represent an uniform electric potential and the smearing in the patterns can be used either to measure the displacement or track the direction of vibrations. The SEM has been used in the recent past by Bahadur er d., (5)-(7) and Bahadur and Parshad (3), (4) to monitor the energy trapping and its absence in some resonator disks. Also, some com- plex SEM micrographs were reported occurring both for rectangu- lar plates and circular disks. In some cases of rectangular plates. a regular periodic band structure was attributed (l), 181 to represent appropriate overtones of flexural vibrations having their resonance frequency close to the fundamental thickness-shear vibrations. It was observed that the propagation of flexural vibrations was parallel to the x-axis of the crystal. In the measurements (l). (g) for t","PeriodicalId":371797,"journal":{"name":"IEEE Transactions on Sonics and Ultrasonics","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1985-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129902779","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}
Definition d'une trentaine de termes se rapportant aux filtres a ondes acoustiques de surface
与表面声波滤波器有关的约30个术语的定义
{"title":"International Electrotechnical Commission Standard - SAW Devices","authors":"E. Kently","doi":"10.1109/T-SU.1985.31678","DOIUrl":"https://doi.org/10.1109/T-SU.1985.31678","url":null,"abstract":"Definition d'une trentaine de termes se rapportant aux filtres a ondes acoustiques de surface","PeriodicalId":371797,"journal":{"name":"IEEE Transactions on Sonics and Ultrasonics","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1985-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131740095","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：