Pub Date : 1990-05-06DOI: 10.1109/VETEC.1990.110306
L. Ailes, M. D. Keitz, S.L. McCulley, S. Seidel, M. Deisenroth, T. Rappaport
At Virginia Tech, an autonomous guided vehicle (AGV) has been developed for use in indoor propagation measurements and for a research/teaching tool in the Computer Integrated Manufacturing Laboratory. The AGV design strategy, navigation methodology, and a calibration technique used to minimize path errors caused by unequal wheel radii in dead-reckoning navigation are described. The basic geometry of dead-reckoning navigation is developed, with a particular emphasis on the use of a calibration run to yield exact wheel radii and steering correction factors for use in navigation. These techniques were used on an actual AGV, and measurements were taken under operating conditions to determine navigation accuracy. The major limitation in dead reckoning comes from improper estimates of wheel radii. This can be compensated for with a calibration run, but the tire radius may still change due to dynamic conditions such as redistribution of vehicle weight during cornering, and inexact manufacturing of the tires themselves. Measurements of vehicle position through use of calibrated dead reckoning show accurate vehicle position to within a few cm along a 10 m path.<>
{"title":"Development of an autonomous guided vehicle for indoor propagation measurements","authors":"L. Ailes, M. D. Keitz, S.L. McCulley, S. Seidel, M. Deisenroth, T. Rappaport","doi":"10.1109/VETEC.1990.110306","DOIUrl":"https://doi.org/10.1109/VETEC.1990.110306","url":null,"abstract":"At Virginia Tech, an autonomous guided vehicle (AGV) has been developed for use in indoor propagation measurements and for a research/teaching tool in the Computer Integrated Manufacturing Laboratory. The AGV design strategy, navigation methodology, and a calibration technique used to minimize path errors caused by unequal wheel radii in dead-reckoning navigation are described. The basic geometry of dead-reckoning navigation is developed, with a particular emphasis on the use of a calibration run to yield exact wheel radii and steering correction factors for use in navigation. These techniques were used on an actual AGV, and measurements were taken under operating conditions to determine navigation accuracy. The major limitation in dead reckoning comes from improper estimates of wheel radii. This can be compensated for with a calibration run, but the tire radius may still change due to dynamic conditions such as redistribution of vehicle weight during cornering, and inexact manufacturing of the tires themselves. Measurements of vehicle position through use of calibrated dead reckoning show accurate vehicle position to within a few cm along a 10 m path.<<ETX>>","PeriodicalId":366352,"journal":{"name":"40th IEEE Conference on Vehicular Technology","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130809433","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 : 1990-05-06DOI: 10.1109/VETEC.1990.110298
L. Nagurney
The development of mobile and portable multi-emission transceivers for analog and digital transmission over a wide frequency range requires the development of integrated modulator and demodulator systems. An experimental multi-emission frequency domain modulator that operates in the frequency range from approximately 5 MHz to 1 GHz is described. Using passive integrated components such as splitters, hybrids, and double-balanced mixers, as well as monolithic broadband amplifiers, the modulator modulates a carrier with a baseband signal in AM, SSB, DSB, FM, PM, or a variety of n-phase-shift keying (PSK)-modes. The analog modulations are generated using frequency domain techniques, i.e., the carrier and each sideband pair are independently generated. The n-PSK modes are developed by combining inphase, +or-90 degrees , and 180 degrees components using amplifiers/attenuators and an in-phase combiner. The performance of this modulator is discussed, as well as extensions to this technique to wideband FM, spread spectrum, and demodulation. Suitable architectures for a transceiver that incorporates this circuit, including integration of this modulator into a monolithic package, are considered.<>
{"title":"A multi-emission frequency domain modulator","authors":"L. Nagurney","doi":"10.1109/VETEC.1990.110298","DOIUrl":"https://doi.org/10.1109/VETEC.1990.110298","url":null,"abstract":"The development of mobile and portable multi-emission transceivers for analog and digital transmission over a wide frequency range requires the development of integrated modulator and demodulator systems. An experimental multi-emission frequency domain modulator that operates in the frequency range from approximately 5 MHz to 1 GHz is described. Using passive integrated components such as splitters, hybrids, and double-balanced mixers, as well as monolithic broadband amplifiers, the modulator modulates a carrier with a baseband signal in AM, SSB, DSB, FM, PM, or a variety of n-phase-shift keying (PSK)-modes. The analog modulations are generated using frequency domain techniques, i.e., the carrier and each sideband pair are independently generated. The n-PSK modes are developed by combining inphase, +or-90 degrees , and 180 degrees components using amplifiers/attenuators and an in-phase combiner. The performance of this modulator is discussed, as well as extensions to this technique to wideband FM, spread spectrum, and demodulation. Suitable architectures for a transceiver that incorporates this circuit, including integration of this modulator into a monolithic package, are considered.<<ETX>>","PeriodicalId":366352,"journal":{"name":"40th IEEE Conference on Vehicular Technology","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130755181","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 : 1990-05-06DOI: 10.1109/VETEC.1990.110378
S. Yoshida, T. Takeuchi, M. Nakamura, F. Ikegami
Return-to-zero phase shift keying (PSK-RZ) is an anti-multipath modulation technique showing much improved bit error rate when the multipath delay difference is smaller than a symbol duration. Major results of high-rate transmission of an anti-multipath modulation technique PSK-RZ experiment in an urban area of Kyoto at 400 MHz band are described. The field test has proven the superior performance of PSK-RZ when the multipath delay time is smaller than a symbol duration. Measurement results are presented and compared with those of another anti-multipath modulation technique, double phase shift keying (DSK). It is confirmed that PSK-RZ shows an anti-multipath feature as long as the multipath delay time is shorter than a symbol duration, whereas DSK shows an anti-multipath feature only when multipath delay time is less than a half-bit duration.<>
{"title":"High bit-rate field transmission of an anti-multipath modulation technique PSK-RZ","authors":"S. Yoshida, T. Takeuchi, M. Nakamura, F. Ikegami","doi":"10.1109/VETEC.1990.110378","DOIUrl":"https://doi.org/10.1109/VETEC.1990.110378","url":null,"abstract":"Return-to-zero phase shift keying (PSK-RZ) is an anti-multipath modulation technique showing much improved bit error rate when the multipath delay difference is smaller than a symbol duration. Major results of high-rate transmission of an anti-multipath modulation technique PSK-RZ experiment in an urban area of Kyoto at 400 MHz band are described. The field test has proven the superior performance of PSK-RZ when the multipath delay time is smaller than a symbol duration. Measurement results are presented and compared with those of another anti-multipath modulation technique, double phase shift keying (DSK). It is confirmed that PSK-RZ shows an anti-multipath feature as long as the multipath delay time is shorter than a symbol duration, whereas DSK shows an anti-multipath feature only when multipath delay time is less than a half-bit duration.<<ETX>>","PeriodicalId":366352,"journal":{"name":"40th IEEE Conference on Vehicular Technology","volume":"119 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132094657","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 : 1990-05-06DOI: 10.1109/VETEC.1990.110302
H. Sharif, E. Furman
A computer model designed to analyze the data communications network of the advanced train control system (ATCS) is discussed. The model was developed using Network II.5, which includes the hardware components and communication protocol of the ATCS data communications network. The model includes the RF channel access mechanism with busy bits. The effect of RF propagation on the system is modeled by assuming a message success rate and adjusting the traffic load accordingly. RF collisions resulting from operation of the busy bit channel access mechanism add to the load when they occur during the simulation. Typical results for the model based on an assumed traffic load are presented to illustrate how the model displays systems performance. A time-stamped record of message traffic over an operating ATCS communication system is compared to the model simulation for the same traffic. For this benchmark, the accuracy of the model is 80% to 91%.<>
{"title":"ATCS RF channel modeling using computer aided engineering","authors":"H. Sharif, E. Furman","doi":"10.1109/VETEC.1990.110302","DOIUrl":"https://doi.org/10.1109/VETEC.1990.110302","url":null,"abstract":"A computer model designed to analyze the data communications network of the advanced train control system (ATCS) is discussed. The model was developed using Network II.5, which includes the hardware components and communication protocol of the ATCS data communications network. The model includes the RF channel access mechanism with busy bits. The effect of RF propagation on the system is modeled by assuming a message success rate and adjusting the traffic load accordingly. RF collisions resulting from operation of the busy bit channel access mechanism add to the load when they occur during the simulation. Typical results for the model based on an assumed traffic load are presented to illustrate how the model displays systems performance. A time-stamped record of message traffic over an operating ATCS communication system is compared to the model simulation for the same traffic. For this benchmark, the accuracy of the model is 80% to 91%.<<ETX>>","PeriodicalId":366352,"journal":{"name":"40th IEEE Conference on Vehicular Technology","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114156952","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 : 1990-05-06DOI: 10.1109/VETEC.1990.110288
A. Kumar
A review of three classes of antennas for data and voice terminals is presented. The first one is a conically shaped beam low-gain antenna for data terminals. Drooping dipoles, quadrifilar helices, and microstrip antennas are described. These antennas can be simple and inexpensive . The second type of mobile terminal antennas are medium gain: microstrip mechanically steered arrays, microstrip electronically steered arrays, and adaptive arrays with a simple beam-steering system. The third type is a high-gain fixed terminal antenna. The noise temperature and G/T values of some antennas are discussed. The results of the vehicle terminal antennas program at AK Electromagnetique in support of developing North American mobile and fixed satellite services are summarized.<>
{"title":"Vehicle terminal antennas for mobile satellite applications","authors":"A. Kumar","doi":"10.1109/VETEC.1990.110288","DOIUrl":"https://doi.org/10.1109/VETEC.1990.110288","url":null,"abstract":"A review of three classes of antennas for data and voice terminals is presented. The first one is a conically shaped beam low-gain antenna for data terminals. Drooping dipoles, quadrifilar helices, and microstrip antennas are described. These antennas can be simple and inexpensive . The second type of mobile terminal antennas are medium gain: microstrip mechanically steered arrays, microstrip electronically steered arrays, and adaptive arrays with a simple beam-steering system. The third type is a high-gain fixed terminal antenna. The noise temperature and G/T values of some antennas are discussed. The results of the vehicle terminal antennas program at AK Electromagnetique in support of developing North American mobile and fixed satellite services are summarized.<<ETX>>","PeriodicalId":366352,"journal":{"name":"40th IEEE Conference on Vehicular Technology","volume":"37 11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116569581","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 : 1990-05-06DOI: 10.1109/VETEC.1990.110397
H. Panzer, R. Beck
It is shown that microcellular structures which will be found in future high-density traffic metropolitan areas require the application of adaptive methods for efficiently allocating the radio resource. Different dimensions of adaptation-adaptive base station allocation, dynamic channel allocation, and adaptive power control-are considered in an integrated manner. To answer if and how the proposed methods can work together, a generic algorithm comprising the different adaptive approaches is introduced. This was complemented by the derivation and definition of a comprehensive set of evaluation criteria. For the evaluation a simulation environment is developed, based on a Manhattan-like road grid structure, and comprising corresponding traffic and propagation models. First results indicate that the combined application of the different adaptation approaches yields the best performance.<>
{"title":"Adaptive resource allocation in metropolitan area cellular mobile radio systems","authors":"H. Panzer, R. Beck","doi":"10.1109/VETEC.1990.110397","DOIUrl":"https://doi.org/10.1109/VETEC.1990.110397","url":null,"abstract":"It is shown that microcellular structures which will be found in future high-density traffic metropolitan areas require the application of adaptive methods for efficiently allocating the radio resource. Different dimensions of adaptation-adaptive base station allocation, dynamic channel allocation, and adaptive power control-are considered in an integrated manner. To answer if and how the proposed methods can work together, a generic algorithm comprising the different adaptive approaches is introduced. This was complemented by the derivation and definition of a comprehensive set of evaluation criteria. For the evaluation a simulation environment is developed, based on a Manhattan-like road grid structure, and comprising corresponding traffic and propagation models. First results indicate that the combined application of the different adaptation approaches yields the best performance.<<ETX>>","PeriodicalId":366352,"journal":{"name":"40th IEEE Conference on Vehicular Technology","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133091679","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 : 1990-05-06DOI: 10.1109/VETEC.1990.110289
J. Badenes, Q. Garcia, M. Hernanz, C. Martin, J. Vassal'lo
An improved and compact design of an antenna system for full coverage of up to 15 degrees of elevation is presented. This system consists of a pair of antennas in microstrip technology (patch and ring), photoetched concentrically in the same substrate. A microstrip circuit is placed on the rear face. Its bandwidth, typical of microstrip radiators, makes it suitable for land-mobile communications. An interesting characteristic of this compact design is its versatility in supplying different coverage requirements including a positioning receiving output, if desired. The design problems and the experimental results both for the circuit elements and for the radiation pattern are discussed.<>
{"title":"A multipurpose flush-mounted antenna system for satellite-land mobile communications and positioning","authors":"J. Badenes, Q. Garcia, M. Hernanz, C. Martin, J. Vassal'lo","doi":"10.1109/VETEC.1990.110289","DOIUrl":"https://doi.org/10.1109/VETEC.1990.110289","url":null,"abstract":"An improved and compact design of an antenna system for full coverage of up to 15 degrees of elevation is presented. This system consists of a pair of antennas in microstrip technology (patch and ring), photoetched concentrically in the same substrate. A microstrip circuit is placed on the rear face. Its bandwidth, typical of microstrip radiators, makes it suitable for land-mobile communications. An interesting characteristic of this compact design is its versatility in supplying different coverage requirements including a positioning receiving output, if desired. The design problems and the experimental results both for the circuit elements and for the radiation pattern are discussed.<<ETX>>","PeriodicalId":366352,"journal":{"name":"40th IEEE Conference on Vehicular Technology","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124882889","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 : 1990-05-06DOI: 10.1109/VETEC.1990.110300
S. McKay, V. I. John, G. Dawson
The enhancement of the Carnegie Mellon software package to incorporate fixed and moving-block signaling schemes is described. The train performance simulator (TPS) component of the module calculates the train dynamics for each train set in the simulation. For fixed-block signaling systems, the TPS monitors the preceding signal for each train and bases the train's calculations on that particular aspect, the type of signal, and whether a crossover is in the next block. Essentially, the aspects determine the local speed restrictions for each train. The aspects themselves are linked together, providing three and four block protection. Conversely, moving-block signaling systems would have train calculations based on the preceding train's dynamics, as opposed to fixed locations along the track. The TPS becomes interactive if signaling is invoked. A communications window is displayed at the bottom of the screen indicating the next aspect which the train is approaching.<>
{"title":"An interactive train operations simulator for integrated applications in transit systems","authors":"S. McKay, V. I. John, G. Dawson","doi":"10.1109/VETEC.1990.110300","DOIUrl":"https://doi.org/10.1109/VETEC.1990.110300","url":null,"abstract":"The enhancement of the Carnegie Mellon software package to incorporate fixed and moving-block signaling schemes is described. The train performance simulator (TPS) component of the module calculates the train dynamics for each train set in the simulation. For fixed-block signaling systems, the TPS monitors the preceding signal for each train and bases the train's calculations on that particular aspect, the type of signal, and whether a crossover is in the next block. Essentially, the aspects determine the local speed restrictions for each train. The aspects themselves are linked together, providing three and four block protection. Conversely, moving-block signaling systems would have train calculations based on the preceding train's dynamics, as opposed to fixed locations along the track. The TPS becomes interactive if signaling is invoked. A communications window is displayed at the bottom of the screen indicating the next aspect which the train is approaching.<<ETX>>","PeriodicalId":366352,"journal":{"name":"40th IEEE Conference on Vehicular Technology","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129438539","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 : 1990-05-06DOI: 10.1109/VETEC.1990.110339
H. Stern
Design improvements for the integrated voice/data mobile radio system proposed by H.P. Stern (1989) are suggested. Time-division multiplexing techniques are used to provide two voice paths on each 25 kHz radio channel, thereby reducing the number of channels needed to carry voice by 50%. Packetized data, voice dedicated (PDVD) burst switching is used to transmit data during the silent periods in the speech. Data capability is thereby added to the system without requiring additional radio channels. System performance is analyzed via computer simulations, which show that for public safety applications a half-duplex voice-only mobile radio system can be upgraded to an integrated voice/data system using only half as many radio channels. The data traffic is minimally delayed, and a constant, 200 ms delay is added to the voice, which is acceptable in a half-duplex environment. The integrated voice/data system can also accommodate significant growth in data traffic.<>
{"title":"An improved integrated voice/data mobile radio system","authors":"H. Stern","doi":"10.1109/VETEC.1990.110339","DOIUrl":"https://doi.org/10.1109/VETEC.1990.110339","url":null,"abstract":"Design improvements for the integrated voice/data mobile radio system proposed by H.P. Stern (1989) are suggested. Time-division multiplexing techniques are used to provide two voice paths on each 25 kHz radio channel, thereby reducing the number of channels needed to carry voice by 50%. Packetized data, voice dedicated (PDVD) burst switching is used to transmit data during the silent periods in the speech. Data capability is thereby added to the system without requiring additional radio channels. System performance is analyzed via computer simulations, which show that for public safety applications a half-duplex voice-only mobile radio system can be upgraded to an integrated voice/data system using only half as many radio channels. The data traffic is minimally delayed, and a constant, 200 ms delay is added to the voice, which is acceptable in a half-duplex environment. The integrated voice/data system can also accommodate significant growth in data traffic.<<ETX>>","PeriodicalId":366352,"journal":{"name":"40th IEEE Conference on Vehicular Technology","volume":"7 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120843410","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 : 1990-05-06DOI: 10.1109/VETEC.1990.110383
T. Ueda, H. Suzuki
To improve the transmission performance of high bit-rate digital mobile radio communications in frequency-selective fading environments, a retraining recursive least squares (RT-RLS) algorithm for a decision feedback equalizer (DFE) is proposed. Performance evaluation experiments were carried out with a real-time experimental system that includes a DFE implemented by a single-chip digital signal processor (DSP). Experiments were performed by transmitting 250 kbit/s quadrature phase shift keying (QPSK) at a maximum Doppler frequency up to 160 Hz. The experiment assumes a two-wave model, in which waves have the same power and fluctuate independently with Rayleigh distribution. A bit error ratio (BER) performance below 10/sup -2/ was realized.<>
{"title":"Performance of equalizers employing a re-training RLS algorithm for digital mobile radio communications","authors":"T. Ueda, H. Suzuki","doi":"10.1109/VETEC.1990.110383","DOIUrl":"https://doi.org/10.1109/VETEC.1990.110383","url":null,"abstract":"To improve the transmission performance of high bit-rate digital mobile radio communications in frequency-selective fading environments, a retraining recursive least squares (RT-RLS) algorithm for a decision feedback equalizer (DFE) is proposed. Performance evaluation experiments were carried out with a real-time experimental system that includes a DFE implemented by a single-chip digital signal processor (DSP). Experiments were performed by transmitting 250 kbit/s quadrature phase shift keying (QPSK) at a maximum Doppler frequency up to 160 Hz. The experiment assumes a two-wave model, in which waves have the same power and fluctuate independently with Rayleigh distribution. A bit error ratio (BER) performance below 10/sup -2/ was realized.<<ETX>>","PeriodicalId":366352,"journal":{"name":"40th IEEE Conference on Vehicular Technology","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131600152","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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