Pub Date : 2004-09-27DOI: 10.1109/DEIV.2004.1418589
V. Choulkov
The existence of electron emission at fields some hundreds of times smaller than expected theoretically for an ideal metal surface one explains by emission increase due to local field enhancement at the sharp metallic point protruding from cathode surface. This paper offers a new mechanism explaining anomalous field emission by effect of natural rughness of crystal face of metal surface with atomic sizes (10-8-10-7 cm). It is shown that natural roughness with size about a few period of crystal lattice leads to production of emission sites where work function is significantly less thin work function at a perfectly smooth surface. The Richardson- Dashman thermo-field emission theory with Schottky correction is used for the calculations of current density at the sites. The electrical field change is evoked by natural roughness of crystal face is taken into account. An estimate of emission current in term of emission sites is performed. Then density of emission Sites on metal surface is computed by using the Statistical theory. Total emission current is determined as current averaged over emission sites distribution on metal surface. It is shown that the thermo-field electron emission from such sites play most important role in total emission at average electric field strength on surface 105-106V/cm.
{"title":"Effect of natural surface roughness on electron emission from metal in electric field","authors":"V. Choulkov","doi":"10.1109/DEIV.2004.1418589","DOIUrl":"https://doi.org/10.1109/DEIV.2004.1418589","url":null,"abstract":"The existence of electron emission at fields some hundreds of times smaller than expected theoretically for an ideal metal surface one explains by emission increase due to local field enhancement at the sharp metallic point protruding from cathode surface. This paper offers a new mechanism explaining anomalous field emission by effect of natural rughness of crystal face of metal surface with atomic sizes (10-8-10-7 cm). It is shown that natural roughness with size about a few period of crystal lattice leads to production of emission sites where work function is significantly less thin work function at a perfectly smooth surface. The Richardson- Dashman thermo-field emission theory with Schottky correction is used for the calculations of current density at the sites. The electrical field change is evoked by natural roughness of crystal face is taken into account. An estimate of emission current in term of emission sites is performed. Then density of emission Sites on metal surface is computed by using the Statistical theory. Total emission current is determined as current averaged over emission sites distribution on metal surface. It is shown that the thermo-field electron emission from such sites play most important role in total emission at average electric field strength on surface 105-106V/cm.","PeriodicalId":137370,"journal":{"name":"XXIst International Symposium on Discharges and Electrical Insulation in Vacuum, 2004. Proceedings. ISDEIV.","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131494481","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 : 2004-09-27DOI: 10.1109/DEIV.2004.1418617
K. Usui, Y. Taniguchi, H. Okubo
nb.smn In order to enhance the electrical insulation performance of vacuum circuit breakers (VCBs), the surface charging mechanism on solid dielectrics in vacuum needs to be clarified. We investigated the charging characteristics on various types of alumina dielectrics for the different AIIO, contents, manufacturing conditions and surface roughness. We applied negative dc ramped voltage on the high voltage electrode and measured the surface charging potential. The experimental results revealed that the charging process was not practically influenced by A120, contents but by the surface roughness.
{"title":"Influence of alumina characteristics on charging mechanism in vacuum","authors":"K. Usui, Y. Taniguchi, H. Okubo","doi":"10.1109/DEIV.2004.1418617","DOIUrl":"https://doi.org/10.1109/DEIV.2004.1418617","url":null,"abstract":"nb.smn In order to enhance the electrical insulation performance of vacuum circuit breakers (VCBs), the surface charging mechanism on solid dielectrics in vacuum needs to be clarified. We investigated the charging characteristics on various types of alumina dielectrics for the different AIIO, contents, manufacturing conditions and surface roughness. We applied negative dc ramped voltage on the high voltage electrode and measured the surface charging potential. The experimental results revealed that the charging process was not practically influenced by A120, contents but by the surface roughness.","PeriodicalId":137370,"journal":{"name":"XXIst International Symposium on Discharges and Electrical Insulation in Vacuum, 2004. Proceedings. ISDEIV.","volume":"158 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133942559","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 : 2004-09-27DOI: 10.1109/DEIV.2004.1418593
N. V. Tatarinova, A. Baryshnikov
Studies of processes in pores of electrode surface were defined by two problems: 1) to suppress these processes in order to increase electrical strength of vacuum gap [1]; 2) to develop charged particle source with cold cathode based on these processes [2]. From the above references follows that at electrical field "strength values achieved in contemporary high voltage electron vacuum devices and electrophysical facilities prebreakdown currents, microdischarges and vacuum breakdown are defined by processes in micropores of electrodes (or the like defects). These processes are nothing but various stages of self-sustaining gas discharge development the final one being formation of cathode part over the surface of the pore. Voltage-current characteristics (VCCs) of prebreakdown currents attributed to processes in pores include linear and exponential parts. Line-to-exponent transition is defined, first of all, by vacuum, gap width and pore size, i.e., by degree of sagging of electrical field into the pore volume. More precisely, electrical field pattern depends on pore geometrical size relation, pore-depth-to-vacuum-gap-width ratio. To the greater extent this dependence is observed pore size being close to vacuum gap width. Pore configuration variation for the same pore size on electrode plane also defines voltage-current characteristics' exponential part appearance, i.e., vacuum gap breakdown. Creating special porous surface one can vary the electrical strength of vacuum insulation.
{"title":"Prebreakdown current dependency on size and configuration of electrode pores","authors":"N. V. Tatarinova, A. Baryshnikov","doi":"10.1109/DEIV.2004.1418593","DOIUrl":"https://doi.org/10.1109/DEIV.2004.1418593","url":null,"abstract":"Studies of processes in pores of electrode surface were defined by two problems: 1) to suppress these processes in order to increase electrical strength of vacuum gap [1]; 2) to develop charged particle source with cold cathode based on these processes [2]. From the above references follows that at electrical field \"strength values achieved in contemporary high voltage electron vacuum devices and electrophysical facilities prebreakdown currents, microdischarges and vacuum breakdown are defined by processes in micropores of electrodes (or the like defects). These processes are nothing but various stages of self-sustaining gas discharge development the final one being formation of cathode part over the surface of the pore. Voltage-current characteristics (VCCs) of prebreakdown currents attributed to processes in pores include linear and exponential parts. Line-to-exponent transition is defined, first of all, by vacuum, gap width and pore size, i.e., by degree of sagging of electrical field into the pore volume. More precisely, electrical field pattern depends on pore geometrical size relation, pore-depth-to-vacuum-gap-width ratio. To the greater extent this dependence is observed pore size being close to vacuum gap width. Pore configuration variation for the same pore size on electrode plane also defines voltage-current characteristics' exponential part appearance, i.e., vacuum gap breakdown. Creating special porous surface one can vary the electrical strength of vacuum insulation.","PeriodicalId":137370,"journal":{"name":"XXIst International Symposium on Discharges and Electrical Insulation in Vacuum, 2004. Proceedings. ISDEIV.","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124890520","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 : 2004-09-27DOI: 10.1109/DEIV.2004.1418598
S. Michizono, Y. Saito, Suharyanto, Y. Yamano, S. Kobayashi
Electrical breakdown is one of the most serious problems for developing compact and/or higher-voltage insulation in a vacuum. High secondary electron emission (SEE) yields result in the multipactor effect (electron multiplication on the dielectric surface). Multipactor induces not only discharging, but also excess surface heating, leading to localized surface melting. Thus, SEE at high temperature is important for understanding the actual breakdown process. The SEE yields of sapphire were measured at high temperature by a single-pulsed beam method with a scanning electron microscope (SEM) so as to avoid surface charging. In general, the effective SEE decreases by multipactor due to surface charging. Since the electrical conductivity becomes higher at a high temperature, effective SEE can be larger due to less surface charging. In order to estimate the surface charging, multi-pulse beams were injected to sapphire disks at room and high temperature.
{"title":"Secondary electron emission and surface charging from alumina at high temperature","authors":"S. Michizono, Y. Saito, Suharyanto, Y. Yamano, S. Kobayashi","doi":"10.1109/DEIV.2004.1418598","DOIUrl":"https://doi.org/10.1109/DEIV.2004.1418598","url":null,"abstract":"Electrical breakdown is one of the most serious problems for developing compact and/or higher-voltage insulation in a vacuum. High secondary electron emission (SEE) yields result in the multipactor effect (electron multiplication on the dielectric surface). Multipactor induces not only discharging, but also excess surface heating, leading to localized surface melting. Thus, SEE at high temperature is important for understanding the actual breakdown process. The SEE yields of sapphire were measured at high temperature by a single-pulsed beam method with a scanning electron microscope (SEM) so as to avoid surface charging. In general, the effective SEE decreases by multipactor due to surface charging. Since the electrical conductivity becomes higher at a high temperature, effective SEE can be larger due to less surface charging. In order to estimate the surface charging, multi-pulse beams were injected to sapphire disks at room and high temperature.","PeriodicalId":137370,"journal":{"name":"XXIst International Symposium on Discharges and Electrical Insulation in Vacuum, 2004. Proceedings. ISDEIV.","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127231001","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 : 2004-09-27DOI: 10.1109/DEIV.2004.1418604
Y. Inagawa, F. Miyazaki, K. Kato, M. Sakaki, H. Ichikawa, H. Okubol
Breakdown (BD) characteristics in vacuum are largely dependent on the electrode surface conditions, like the roughness etc. Therefore, in order to develop high voltage vacuum circuit breakers, the research how the electrode surface roughness affects the BD characteristics is important. This paper discussed the influence of the electrode surface roughness on ED conditioning process under non-uniform electric field in vacuum. Experimental results revealed that the difference of electrode surface roughness affected the BD region, the BD voltage, and the BD field strength, as well as the conditioning process.
{"title":"Effect of electrode surface roughness on breakdown conditioning process under non-uniform electric field in vacuum","authors":"Y. Inagawa, F. Miyazaki, K. Kato, M. Sakaki, H. Ichikawa, H. Okubol","doi":"10.1109/DEIV.2004.1418604","DOIUrl":"https://doi.org/10.1109/DEIV.2004.1418604","url":null,"abstract":"Breakdown (BD) characteristics in vacuum are largely dependent on the electrode surface conditions, like the roughness etc. Therefore, in order to develop high voltage vacuum circuit breakers, the research how the electrode surface roughness affects the BD characteristics is important. This paper discussed the influence of the electrode surface roughness on ED conditioning process under non-uniform electric field in vacuum. Experimental results revealed that the difference of electrode surface roughness affected the BD region, the BD voltage, and the BD field strength, as well as the conditioning process.","PeriodicalId":137370,"journal":{"name":"XXIst International Symposium on Discharges and Electrical Insulation in Vacuum, 2004. Proceedings. ISDEIV.","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127900955","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 : 2004-09-27DOI: 10.1109/DEIV.2004.1418654
D. Gentsch, W. Shang
Vacuum interrupter especially with high short-circuit interruption ability are mostly equipped with contact systems based on two different principles. One of them is the widely used radial magnetic field contact (RMF), while the other is the axial magnetic field (AMF) contact system. By using a high speed CMOS digital video camera, different contact systems could be observed during arcing under short-circuit conditions. The investigation was concentrated on arc modes development with different contact systems and different arcing times, and focused on three contact systems such as one improved RMF and two different AMF systems. In case of the AMF systems both an unipolar and a quadrupolar contact system was considered.
{"title":"High-speed observations of arc modes on RMF- and AMF- contacts","authors":"D. Gentsch, W. Shang","doi":"10.1109/DEIV.2004.1418654","DOIUrl":"https://doi.org/10.1109/DEIV.2004.1418654","url":null,"abstract":"Vacuum interrupter especially with high short-circuit interruption ability are mostly equipped with contact systems based on two different principles. One of them is the widely used radial magnetic field contact (RMF), while the other is the axial magnetic field (AMF) contact system. By using a high speed CMOS digital video camera, different contact systems could be observed during arcing under short-circuit conditions. The investigation was concentrated on arc modes development with different contact systems and different arcing times, and focused on three contact systems such as one improved RMF and two different AMF systems. In case of the AMF systems both an unipolar and a quadrupolar contact system was considered.","PeriodicalId":137370,"journal":{"name":"XXIst International Symposium on Discharges and Electrical Insulation in Vacuum, 2004. Proceedings. ISDEIV.","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117305218","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 : 2004-09-27DOI: 10.1109/DEIV.2004.1418616
Gao Youhua, Wang Er-zhi, Liu Yanbin, Cao Yundong
In this paper, a new mathematical model combining electric field and current,field is introduced and finite element method is adopted to calkulate the transient electric field of the external insulation of the outdoor vacuum circuit breaker. Dielectric medium with permittivity E and conductivity y under lightning impulse is taken into account. The response caused by lightning impulse voltage i s expressed by Duhamel integration, which is regarded as the boundary excitation of solved region. Under lightning impulse voltage, the potential distributions of external insulation at representative time are shown. Electric intensity distribution curves on external insulation surface with respect to time are also calculated in this paper. The maximum of intensity on external insulation surface is also given, which are compared with the one in the static field. Some distinguishing features of the transient field arc also discussed. It is essential for vacuum circuit breaker insulation design.
{"title":"Numerical analysis of the external insulation of outdoor vacuum circuit breaker under lightning impulse voltage","authors":"Gao Youhua, Wang Er-zhi, Liu Yanbin, Cao Yundong","doi":"10.1109/DEIV.2004.1418616","DOIUrl":"https://doi.org/10.1109/DEIV.2004.1418616","url":null,"abstract":"In this paper, a new mathematical model combining electric field and current,field is introduced and finite element method is adopted to calkulate the transient electric field of the external insulation of the outdoor vacuum circuit breaker. Dielectric medium with permittivity E and conductivity y under lightning impulse is taken into account. The response caused by lightning impulse voltage i s expressed by Duhamel integration, which is regarded as the boundary excitation of solved region. Under lightning impulse voltage, the potential distributions of external insulation at representative time are shown. Electric intensity distribution curves on external insulation surface with respect to time are also calculated in this paper. The maximum of intensity on external insulation surface is also given, which are compared with the one in the static field. Some distinguishing features of the transient field arc also discussed. It is essential for vacuum circuit breaker insulation design.","PeriodicalId":137370,"journal":{"name":"XXIst International Symposium on Discharges and Electrical Insulation in Vacuum, 2004. Proceedings. ISDEIV.","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133373254","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 : 2004-09-27DOI: 10.1109/DEIV.2004.1418664
Y. Korolev, O. B. Frants, V. G. Geyman, R. V. Ivashov, N. Landl, I. A. Shemyakin, R. Bischoff, K. Frank, I. Petzenhauser
The quenching of a high pulsed current in the pseudospark discharge is accompanied by an inductive voltage kick at the gap and by formation of an electron beam at the discharge axis. The paper deals with the investigation of this phenomenon. The main idea of the proposed physical mechanism is that the electrons are accelerated in a double electric layer, The main electrode gap of the pseudospark discharge forms by which forms during the quenching process between the hollow cathode plasma and the near-anode plasma. Interpretation of the experimental data on this basis is presented.
{"title":"Current quenching in the pseudospark discharge and generation of a fast electron beam","authors":"Y. Korolev, O. B. Frants, V. G. Geyman, R. V. Ivashov, N. Landl, I. A. Shemyakin, R. Bischoff, K. Frank, I. Petzenhauser","doi":"10.1109/DEIV.2004.1418664","DOIUrl":"https://doi.org/10.1109/DEIV.2004.1418664","url":null,"abstract":"The quenching of a high pulsed current in the pseudospark discharge is accompanied by an inductive voltage kick at the gap and by formation of an electron beam at the discharge axis. The paper deals with the investigation of this phenomenon. The main idea of the proposed physical mechanism is that the electrons are accelerated in a double electric layer, The main electrode gap of the pseudospark discharge forms by which forms during the quenching process between the hollow cathode plasma and the near-anode plasma. Interpretation of the experimental data on this basis is presented.","PeriodicalId":137370,"journal":{"name":"XXIst International Symposium on Discharges and Electrical Insulation in Vacuum, 2004. Proceedings. ISDEIV.","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121863617","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 : 2004-09-27DOI: 10.1109/DEIV.2004.1418632
J. Londer, K. Ulyanov
The paper deals with the effect of the anode-spattered atoms on the fast cathode ion stream in the vacuum discharge at relatively low (⩽100 A/cm2) current densities. The problem is considered in terms of an instantaneous ionization model and a model regarding for a finite ionization length. The calculations, define the boundary of the stable current flow as B function of the arc current density, and densities and velocities of sputtered atoms.
{"title":"Effect of the anode-spattered atom stream on the current flow in the vacuum arc","authors":"J. Londer, K. Ulyanov","doi":"10.1109/DEIV.2004.1418632","DOIUrl":"https://doi.org/10.1109/DEIV.2004.1418632","url":null,"abstract":"The paper deals with the effect of the anode-spattered atoms on the fast cathode ion stream in the vacuum discharge at relatively low (⩽100 A/cm2) current densities. The problem is considered in terms of an instantaneous ionization model and a model regarding for a finite ionization length. The calculations, define the boundary of the stable current flow as B function of the arc current density, and densities and velocities of sputtered atoms.","PeriodicalId":137370,"journal":{"name":"XXIst International Symposium on Discharges and Electrical Insulation in Vacuum, 2004. Proceedings. ISDEIV.","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115618928","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 : 2004-09-27DOI: 10.1109/DEIV.2004.1418627
B. Juettner
High speed pictures of arc spots on copper cathodes in vacuum have been taken with high time and space resolution (10 ns and 3 μm, respeetively). They reveal that the spots are located at the rim of large craters, sometimes turning around the crater center with velocities in excess of 1000 d s . On a time scale of milliseconds the spots frequently come hack to their previous locations (memory effect). Supplementary experiments with aolyhdenum and tungsten cathodes show that the appearance of the spots can he controlled by small amounts of oxides and carbides, whereas high temperatures strongly reduce the probability the spot ignition. From these observations it is concluded that cold field electron emission is the base for the spot displacement even if the field appears to he relatively low.
{"title":"The influence of the surface structure on the behavior of arc cathode spots in vacuum","authors":"B. Juettner","doi":"10.1109/DEIV.2004.1418627","DOIUrl":"https://doi.org/10.1109/DEIV.2004.1418627","url":null,"abstract":"High speed pictures of arc spots on copper cathodes in vacuum have been taken with high time and space resolution (10 ns and 3 μm, respeetively). They reveal that the spots are located at the rim of large craters, sometimes turning around the crater center with velocities in excess of 1000 d s . On a time scale of milliseconds the spots frequently come hack to their previous locations (memory effect). Supplementary experiments with aolyhdenum and tungsten cathodes show that the appearance of the spots can he controlled by small amounts of oxides and carbides, whereas high temperatures strongly reduce the probability the spot ignition. From these observations it is concluded that cold field electron emission is the base for the spot displacement even if the field appears to he relatively low.","PeriodicalId":137370,"journal":{"name":"XXIst International Symposium on Discharges and Electrical Insulation in Vacuum, 2004. Proceedings. ISDEIV.","volume":"124 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115639107","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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