Pub Date : 1996-08-19DOI: 10.1109/ISEMC.1996.561267
W. Schaefer
Preliminary field strength measurements, also known as prescans, are an integral part of most radiated EMI measurements and serve a number of different purposes. In almost all applications, these type of tests are used to quickly obtain information about the frequency spectrum emitted by the equipment under test (EUT). In order to minimize measurement time, peak detection is usually used instead of quasi-peak or average detection which is called out in most commercial EMI regulations. A measurement system consisting of a swept EMI receiver with a real-time display, dedicated control software, and necessary accessories is best suited for this task. It rapidly acquires spectral information, provides both graphical and tabular representation of test results and gives an insight to characteristics of emissions from the EUT. Achieving the highest measurement speed is one of the most important goals when executing prescans. However, there are tradeoffs to be made which might affect frequency uncertainty, receiver display frequency resolution, display detection mode, antenna tower and turntable movement. This paper discusses the significance of these test parameters for prescan and their impact on measurement time and efficiency.
{"title":"Measurement parameter evaluation for prescans as part of radiated EMI measurements","authors":"W. Schaefer","doi":"10.1109/ISEMC.1996.561267","DOIUrl":"https://doi.org/10.1109/ISEMC.1996.561267","url":null,"abstract":"Preliminary field strength measurements, also known as prescans, are an integral part of most radiated EMI measurements and serve a number of different purposes. In almost all applications, these type of tests are used to quickly obtain information about the frequency spectrum emitted by the equipment under test (EUT). In order to minimize measurement time, peak detection is usually used instead of quasi-peak or average detection which is called out in most commercial EMI regulations. A measurement system consisting of a swept EMI receiver with a real-time display, dedicated control software, and necessary accessories is best suited for this task. It rapidly acquires spectral information, provides both graphical and tabular representation of test results and gives an insight to characteristics of emissions from the EUT. Achieving the highest measurement speed is one of the most important goals when executing prescans. However, there are tradeoffs to be made which might affect frequency uncertainty, receiver display frequency resolution, display detection mode, antenna tower and turntable movement. This paper discusses the significance of these test parameters for prescan and their impact on measurement time and efficiency.","PeriodicalId":296175,"journal":{"name":"Proceedings of Symposium on Electromagnetic Compatibility","volume":"112 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124320018","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 : 1996-08-19DOI: 10.1109/ISEMC.1996.561419
Ya-ping Du, J. Burnett
Magnetic field shielding of cylindrical shields has been studied for a long time, and analytical solution has been derived at power-frequency. This paper, based on previous work, presents an analysis of the shielding principles of a linear cylindrical shield at power-frequency. The shielding principles are developed from simplified shielding formulas under a single-shell and inside-source configuration. Partition of parameter space is introduced, and four regions (linear induced-current, nonlinear induced-current, flux-shunting and induced-current/flux-shunting shielding) are identified geometrically. It reveals the inherent relationship between the shield parameters and shielding effectiveness. A sensitivity study of the shield parameters is conducted too. It discloses the inherent patterns of the parameter impact on the shielding effectiveness. Convenient design curves are presented in the 2D space. These shielding principles and design curves will alleviate the shielding design burden.
{"title":"Magnetic shielding principles of linear cylindrical shield at power-frequency","authors":"Ya-ping Du, J. Burnett","doi":"10.1109/ISEMC.1996.561419","DOIUrl":"https://doi.org/10.1109/ISEMC.1996.561419","url":null,"abstract":"Magnetic field shielding of cylindrical shields has been studied for a long time, and analytical solution has been derived at power-frequency. This paper, based on previous work, presents an analysis of the shielding principles of a linear cylindrical shield at power-frequency. The shielding principles are developed from simplified shielding formulas under a single-shell and inside-source configuration. Partition of parameter space is introduced, and four regions (linear induced-current, nonlinear induced-current, flux-shunting and induced-current/flux-shunting shielding) are identified geometrically. It reveals the inherent relationship between the shield parameters and shielding effectiveness. A sensitivity study of the shield parameters is conducted too. It discloses the inherent patterns of the parameter impact on the shielding effectiveness. Convenient design curves are presented in the 2D space. These shielding principles and design curves will alleviate the shielding design burden.","PeriodicalId":296175,"journal":{"name":"Proceedings of Symposium on Electromagnetic Compatibility","volume":"460 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134063898","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 : 1996-08-19DOI: 10.1109/ISEMC.1996.561224
C.E. Goldblum, D. Lane, J. Press, L. Rayadurga, L. Cohen
Mode-stirred (tuned reverberating) chambers are used for performing EMC measurements. These chambers have several advantages over traditional EMC test facilities. These advantages include the ability to simulate high intensity radiated field (HIRF) levels by using low power amplifiers to produce a statistically isotropic electromagnetic environment. The major disadvantage of the mode-stirred chambers has been the inability to produce an electromagnetic environment near the cutoff frequency of the chamber. Typically, a mode-stirred chamber begins to operate at six times the cutoff frequency or approximately 200 MHz for an average-sized chamber. This limitation has a detrimental impact on electronic equipment assessment within the high frequency (HF) spectrum (2-30 MHz) where a vast majority of electromagnetic interference (EMI) events occur. This paper describes a unique chamber which combines the mode-stirred technique with a method which enables test personnel to perform HIRF testing into the HF spectrum. The Advanced Technology Chamber (ATC) can be used as a standard mode-stirred chamber above 200 MHz and HIRF testing can be continued into the HF spectrum without reinstalling the equipment under test into a different test cell. HF susceptibility testing is usually performed on subsystems utilizing the test techniques described in MIL-SID-462D, Test Method RS103. The wave impedance associated with a parallel plate antenna is 377 ohms. This impedance has little relevance to the wave impedance of an environment containing HF transmitting antennas located within 100 meters of electronic equipment. This environment is of particular interest to the US Navy with its extremely harsh HF topside EM environments. The major advantage of the ATC over parallel plate antennas and hybrid chambers is the ability to produce a true HF wave impedance. The majority of HF disruptions occur close (with respect to the electrical wavelength) to the HF source. Since the wave mode is not TEM in the near field of the antenna, the present plane-wave test techniques can lead to erroneous results.
{"title":"Evanescent modes in a unique mode-stirred chamber the Advanced Technology Chamber (ATC)-design, construction, operation and data","authors":"C.E. Goldblum, D. Lane, J. Press, L. Rayadurga, L. Cohen","doi":"10.1109/ISEMC.1996.561224","DOIUrl":"https://doi.org/10.1109/ISEMC.1996.561224","url":null,"abstract":"Mode-stirred (tuned reverberating) chambers are used for performing EMC measurements. These chambers have several advantages over traditional EMC test facilities. These advantages include the ability to simulate high intensity radiated field (HIRF) levels by using low power amplifiers to produce a statistically isotropic electromagnetic environment. The major disadvantage of the mode-stirred chambers has been the inability to produce an electromagnetic environment near the cutoff frequency of the chamber. Typically, a mode-stirred chamber begins to operate at six times the cutoff frequency or approximately 200 MHz for an average-sized chamber. This limitation has a detrimental impact on electronic equipment assessment within the high frequency (HF) spectrum (2-30 MHz) where a vast majority of electromagnetic interference (EMI) events occur. This paper describes a unique chamber which combines the mode-stirred technique with a method which enables test personnel to perform HIRF testing into the HF spectrum. The Advanced Technology Chamber (ATC) can be used as a standard mode-stirred chamber above 200 MHz and HIRF testing can be continued into the HF spectrum without reinstalling the equipment under test into a different test cell. HF susceptibility testing is usually performed on subsystems utilizing the test techniques described in MIL-SID-462D, Test Method RS103. The wave impedance associated with a parallel plate antenna is 377 ohms. This impedance has little relevance to the wave impedance of an environment containing HF transmitting antennas located within 100 meters of electronic equipment. This environment is of particular interest to the US Navy with its extremely harsh HF topside EM environments. The major advantage of the ATC over parallel plate antennas and hybrid chambers is the ability to produce a true HF wave impedance. The majority of HF disruptions occur close (with respect to the electrical wavelength) to the HF source. Since the wave mode is not TEM in the near field of the antenna, the present plane-wave test techniques can lead to erroneous results.","PeriodicalId":296175,"journal":{"name":"Proceedings of Symposium on Electromagnetic Compatibility","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134533345","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 : 1996-08-19DOI: 10.1109/ISEMC.1996.561273
H. Shi, F. Yuan, F. Sha, J. Drewniak, T. Hubing, T. van Doren
DC power bus decoupling of a multi-layer PCB is modeled by a combination of a lumped circuit model at low frequencies (<200 MHz), and a mixed-potential integral equation approach at high frequencies. In order to determine the lumped parameters of via interconnects, an effective procedure using a network analyzer has been developed to characterize the trace/via inductances/resistances. For an 8"/spl times/10" ten-layer test board used in this study, the simulations show good agreement with the measurement. This method can lead to new design strategies of decoupling for multilayer PCB power buses.
{"title":"Simulation and measurement for decoupling on multilayer PCB DC power buses","authors":"H. Shi, F. Yuan, F. Sha, J. Drewniak, T. Hubing, T. van Doren","doi":"10.1109/ISEMC.1996.561273","DOIUrl":"https://doi.org/10.1109/ISEMC.1996.561273","url":null,"abstract":"DC power bus decoupling of a multi-layer PCB is modeled by a combination of a lumped circuit model at low frequencies (<200 MHz), and a mixed-potential integral equation approach at high frequencies. In order to determine the lumped parameters of via interconnects, an effective procedure using a network analyzer has been developed to characterize the trace/via inductances/resistances. For an 8\"/spl times/10\" ten-layer test board used in this study, the simulations show good agreement with the measurement. This method can lead to new design strategies of decoupling for multilayer PCB power buses.","PeriodicalId":296175,"journal":{"name":"Proceedings of Symposium on Electromagnetic Compatibility","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131624953","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 : 1996-08-19DOI: 10.1109/ISEMC.1996.561245
R. Perez
The Magellan spacecraft synthetic aperture radar experienced a failure when the receiver protect circuitry in the PRF/Timing subsystem failed. The receiver protect circuitry failed due to electromagnetic coupling from the ultra stable oscillator/clock generator circuit located on an adjacent board. Some ICs in this ultra stable oscillator/clock generator circuit had previously become detached from their traces when a thermal test caused the conformal coating to expand. The ICs were re-attached to the PCB traces using "smallwire loops" which apparently radiated significantly to cause the failure of the receiver protect circuits. The analysis which discovered the above failure mechanism is discussed. The analysis also includes the use of the method of moments to model the radiation from a portion of the noisy board and coupling into the susceptible circuits of another board. The analysis also derives expressions for the near field coupling between the radiating structure and the susceptible circuit. Only one of such models is discussed herein for brevity. The simple solution to the electromagnetic coupling problems is discussed in the conclusion of this work.
{"title":"Electromagnetic induced timing defects in the synthetic aperture radar of the Magellan spacecraft","authors":"R. Perez","doi":"10.1109/ISEMC.1996.561245","DOIUrl":"https://doi.org/10.1109/ISEMC.1996.561245","url":null,"abstract":"The Magellan spacecraft synthetic aperture radar experienced a failure when the receiver protect circuitry in the PRF/Timing subsystem failed. The receiver protect circuitry failed due to electromagnetic coupling from the ultra stable oscillator/clock generator circuit located on an adjacent board. Some ICs in this ultra stable oscillator/clock generator circuit had previously become detached from their traces when a thermal test caused the conformal coating to expand. The ICs were re-attached to the PCB traces using \"smallwire loops\" which apparently radiated significantly to cause the failure of the receiver protect circuits. The analysis which discovered the above failure mechanism is discussed. The analysis also includes the use of the method of moments to model the radiation from a portion of the noisy board and coupling into the susceptible circuits of another board. The analysis also derives expressions for the near field coupling between the radiating structure and the susceptible circuit. Only one of such models is discussed herein for brevity. The simple solution to the electromagnetic coupling problems is discussed in the conclusion of this work.","PeriodicalId":296175,"journal":{"name":"Proceedings of Symposium on Electromagnetic Compatibility","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115708460","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 : 1996-08-19DOI: 10.1109/ISEMC.1996.561190
J. Knapp, A. Wall
Telecommunications equipment and certain electronic products require approval by the Federal Communications Commission (FCC) before they may be imported and marketed in the United States. There is growing worldwide interest in streamlining equipment approval processes for a number of reasons. The FCC has established an equipment authorization program to ensure that telecommunications and electronic products meet standards that are designed to control radio frequency interference. This paper describes the current FCC equipment authorization requirements and the forces at work seeking to streamline equipment approval processes. Special attention is devoted to international developments. The paper goes on to discuss a major FCC action to deregulate the equipment authorization process for personal computer equipment, that is perhaps a first step towards an equipment approval process that will be consistent with these international developments.
{"title":"Streamlining the FCC equipment authorization process in response to changing global markets","authors":"J. Knapp, A. Wall","doi":"10.1109/ISEMC.1996.561190","DOIUrl":"https://doi.org/10.1109/ISEMC.1996.561190","url":null,"abstract":"Telecommunications equipment and certain electronic products require approval by the Federal Communications Commission (FCC) before they may be imported and marketed in the United States. There is growing worldwide interest in streamlining equipment approval processes for a number of reasons. The FCC has established an equipment authorization program to ensure that telecommunications and electronic products meet standards that are designed to control radio frequency interference. This paper describes the current FCC equipment authorization requirements and the forces at work seeking to streamline equipment approval processes. Special attention is devoted to international developments. The paper goes on to discuss a major FCC action to deregulate the equipment authorization process for personal computer equipment, that is perhaps a first step towards an equipment approval process that will be consistent with these international developments.","PeriodicalId":296175,"journal":{"name":"Proceedings of Symposium on Electromagnetic Compatibility","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124830823","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 : 1996-08-19DOI: 10.1109/ISEMC.1996.561272
W. Croisant, C. A. Feickert, M. McInerney
Previously, an analytical procedure was developed to characterize the nonlinear electric field transients induced at the inner surface of long, thin-walled, cylindrical, electrically conductive, ferromagnetic shields by short-duration, surface current pulses directed axially along the outer surface. The analytical procedure uses mathematical analysis supplemented with numerical calculations. Previous papers emphasized the mathematical aspects of the problem. This paper considers the computational aspects. Some practical aspects associated with the implementation of a finite difference time-domain (FDTD) formulation are discussed. The effects of spatial and time increments on numerical results are investigated. A method for estimating the residual error in benchmark calculations is proposed and demonstrated, and results of example calculations are presented.
{"title":"Computational aspects of a nonlinear problem involving electromagnetic transients in ferromagnetic shields","authors":"W. Croisant, C. A. Feickert, M. McInerney","doi":"10.1109/ISEMC.1996.561272","DOIUrl":"https://doi.org/10.1109/ISEMC.1996.561272","url":null,"abstract":"Previously, an analytical procedure was developed to characterize the nonlinear electric field transients induced at the inner surface of long, thin-walled, cylindrical, electrically conductive, ferromagnetic shields by short-duration, surface current pulses directed axially along the outer surface. The analytical procedure uses mathematical analysis supplemented with numerical calculations. Previous papers emphasized the mathematical aspects of the problem. This paper considers the computational aspects. Some practical aspects associated with the implementation of a finite difference time-domain (FDTD) formulation are discussed. The effects of spatial and time increments on numerical results are investigated. A method for estimating the residual error in benchmark calculations is proposed and demonstrated, and results of example calculations are presented.","PeriodicalId":296175,"journal":{"name":"Proceedings of Symposium on Electromagnetic Compatibility","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121677335","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 : 1996-08-19DOI: 10.1109/ISEMC.1996.561425
H. Benitez
The European Union EMC compliance process is more complex than it may first appear. This paper helps the manufacturer understand product standards and the available routes to compliance that support the EMC Directive. In addition, a cradle-to-grave process is reviewed that has proven to be effective in assuring manufacturer's product compliance goals are achieved.
{"title":"Routes to EMC compliance: a manufacturer has choices","authors":"H. Benitez","doi":"10.1109/ISEMC.1996.561425","DOIUrl":"https://doi.org/10.1109/ISEMC.1996.561425","url":null,"abstract":"The European Union EMC compliance process is more complex than it may first appear. This paper helps the manufacturer understand product standards and the available routes to compliance that support the EMC Directive. In addition, a cradle-to-grave process is reviewed that has proven to be effective in assuring manufacturer's product compliance goals are achieved.","PeriodicalId":296175,"journal":{"name":"Proceedings of Symposium on Electromagnetic Compatibility","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122922950","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 : 1996-08-19DOI: 10.1109/ISEMC.1996.561209
S. Celozzi, M. D'amore
The analysis of shielding performance of ferromagnetic cylindrical cans is presented. The near field loop source is described introducing wave impedances which depend upon the orientation of the source. Hysteresis is taken into account accurately by means of a nonlinear implicit differential equation. The time domain solution procedure is based on the finite element time domain method. Results are presented considering two relevant source configurations.
{"title":"Shielding performance of ferromagnetic cylindrical cans","authors":"S. Celozzi, M. D'amore","doi":"10.1109/ISEMC.1996.561209","DOIUrl":"https://doi.org/10.1109/ISEMC.1996.561209","url":null,"abstract":"The analysis of shielding performance of ferromagnetic cylindrical cans is presented. The near field loop source is described introducing wave impedances which depend upon the orientation of the source. Hysteresis is taken into account accurately by means of a nonlinear implicit differential equation. The time domain solution procedure is based on the finite element time domain method. Results are presented considering two relevant source configurations.","PeriodicalId":296175,"journal":{"name":"Proceedings of Symposium on Electromagnetic Compatibility","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116882788","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 : 1996-08-19DOI: 10.1109/ISEMC.1996.561427
D. Sawdon
A review is given of standards and guidelines dealing with low frequency emissions from visual display units. It is followed by a description of a new formal Swedish standard and a report of progress towards the development of it into a formal, pragmatic, world-wide standard. Finally, it is suggested that the IEEE adopt the new Swedish standard in place of the existing P1140 document or any update of it. The documents discussed include SS 436 14 90 (edition 2), MPR 1990:8 and MPR 1990:10 (together known colloquially as MPR2), IEEE P-1140, TCO-91 and JEIDA G-15-1993.
{"title":"Low frequency display emissions-a new standard","authors":"D. Sawdon","doi":"10.1109/ISEMC.1996.561427","DOIUrl":"https://doi.org/10.1109/ISEMC.1996.561427","url":null,"abstract":"A review is given of standards and guidelines dealing with low frequency emissions from visual display units. It is followed by a description of a new formal Swedish standard and a report of progress towards the development of it into a formal, pragmatic, world-wide standard. Finally, it is suggested that the IEEE adopt the new Swedish standard in place of the existing P1140 document or any update of it. The documents discussed include SS 436 14 90 (edition 2), MPR 1990:8 and MPR 1990:10 (together known colloquially as MPR2), IEEE P-1140, TCO-91 and JEIDA G-15-1993.","PeriodicalId":296175,"journal":{"name":"Proceedings of Symposium on Electromagnetic Compatibility","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126724784","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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