Pub Date : 1991-07-08DOI: 10.1109/ICPADM.1991.172065
B. Vahidi, M. Abedi, S. H. Hosseinian
The Iranian isokeraunic map developed by the authors is presented. A statistical analysis of tower footing resistances of 400 kV lines in the Iranian national grid is also presented. An attempt has been made to evaluate lightning fifty-percent breakdown voltage (V/sub 50/) across 400 kV insulators in Iran, according to obtained keraunic levels and probabilistic results of tower footing resistances. A comparison between calculated V/sub 50/ and V/sub 50/ of presently installed insulators of 400 kV lines in the Iranian transmission system is also presented.<>
{"title":"The evaluation of fifty percent breakdown voltage across Iranian 400 kV transmission line insulators","authors":"B. Vahidi, M. Abedi, S. H. Hosseinian","doi":"10.1109/ICPADM.1991.172065","DOIUrl":"https://doi.org/10.1109/ICPADM.1991.172065","url":null,"abstract":"The Iranian isokeraunic map developed by the authors is presented. A statistical analysis of tower footing resistances of 400 kV lines in the Iranian national grid is also presented. An attempt has been made to evaluate lightning fifty-percent breakdown voltage (V/sub 50/) across 400 kV insulators in Iran, according to obtained keraunic levels and probabilistic results of tower footing resistances. A comparison between calculated V/sub 50/ and V/sub 50/ of presently installed insulators of 400 kV lines in the Iranian transmission system is also presented.<<ETX>>","PeriodicalId":6450,"journal":{"name":"[1991] Proceedings of the 3rd International Conference on Properties and Applications of Dielectric Materials","volume":"15 1","pages":"331-334 vol.1"},"PeriodicalIF":0.0,"publicationDate":"1991-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83916734","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 : 1991-07-08DOI: 10.1109/ICPADM.1991.172141
H. Mosicka-Grzesiak, Z. Banaszak
Metal evaporated on a nonideally smooth surface of ceramic insulators constitutes a discontinuous layer. Thus, the dielectric properties of the ceramic material are preserved, but at the same time one can observe a great change in these properties. The authors present a comparative analysis of some selected surface dielectric properties of alumina insulators on which a copper layer is deposited. The following relations were investigated in air and in vacuum: the dependence of surface resistivity on the amount of deposited copper, the dependence of surface resistivity on voltage, and flashover voltage as a function of surface resistivity. Coating the insulator with copper may cause both an increase (176%) and a decrease (59%) of flashover voltage in vacuum, whereas in air the influence of surface resistivity within the range of 10/sup 8/-10/sup 20/ Omega -cm/cm was not observed.<>
{"title":"Surface dielectric properties of Cu-evaporated alumina insulators in vacuum and air","authors":"H. Mosicka-Grzesiak, Z. Banaszak","doi":"10.1109/ICPADM.1991.172141","DOIUrl":"https://doi.org/10.1109/ICPADM.1991.172141","url":null,"abstract":"Metal evaporated on a nonideally smooth surface of ceramic insulators constitutes a discontinuous layer. Thus, the dielectric properties of the ceramic material are preserved, but at the same time one can observe a great change in these properties. The authors present a comparative analysis of some selected surface dielectric properties of alumina insulators on which a copper layer is deposited. The following relations were investigated in air and in vacuum: the dependence of surface resistivity on the amount of deposited copper, the dependence of surface resistivity on voltage, and flashover voltage as a function of surface resistivity. Coating the insulator with copper may cause both an increase (176%) and a decrease (59%) of flashover voltage in vacuum, whereas in air the influence of surface resistivity within the range of 10/sup 8/-10/sup 20/ Omega -cm/cm was not observed.<<ETX>>","PeriodicalId":6450,"journal":{"name":"[1991] Proceedings of the 3rd International Conference on Properties and Applications of Dielectric Materials","volume":"69 1","pages":"627-630 vol.1"},"PeriodicalIF":0.0,"publicationDate":"1991-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88454302","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 : 1991-07-08DOI: 10.1109/ICPADM.1991.172223
T. Fujiwara, H. Yamada, T. Shimada, K. Sugita
The induced toroidal electric field in water was optically measured by means of a Pockels device. For induction of the electric field based on the transformer principle, multiple primary coils have been used in order to avoid the increase in the primary voltage. A Bi/sub 12/SiO/sub 20/ crystal with a relative permittivity of 56 is used as the Pockels device. Since the electric field inside the crystal becomes much smaller than that in air due to the large permittivity, the electric field measurement has been performed in water in order to increase the sensitivity. The retardations by Pockels effect are on the order of 10/sup -3/ approximately 10/sup -2/, and V/cm, which agrees with those calculated from one-turn voltage within about 20%.<>
{"title":"Optical measurement of induced electric field in water using Pockels device","authors":"T. Fujiwara, H. Yamada, T. Shimada, K. Sugita","doi":"10.1109/ICPADM.1991.172223","DOIUrl":"https://doi.org/10.1109/ICPADM.1991.172223","url":null,"abstract":"The induced toroidal electric field in water was optically measured by means of a Pockels device. For induction of the electric field based on the transformer principle, multiple primary coils have been used in order to avoid the increase in the primary voltage. A Bi/sub 12/SiO/sub 20/ crystal with a relative permittivity of 56 is used as the Pockels device. Since the electric field inside the crystal becomes much smaller than that in air due to the large permittivity, the electric field measurement has been performed in water in order to increase the sensitivity. The retardations by Pockels effect are on the order of 10/sup -3/ approximately 10/sup -2/, and V/cm, which agrees with those calculated from one-turn voltage within about 20%.<<ETX>>","PeriodicalId":6450,"journal":{"name":"[1991] Proceedings of the 3rd International Conference on Properties and Applications of Dielectric Materials","volume":"139 1","pages":"924-927 vol.2"},"PeriodicalIF":0.0,"publicationDate":"1991-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88541886","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 : 1991-07-08DOI: 10.1109/ICPADM.1991.172042
K. Imai, A. Kanematsu, M. Nawata, M. Zahn
Kerr electro-optic field mapping measurements using the sensitive AC modulation method were made in liquid nitrogen. The steady-state electric fields between parallel stainless steel electrodes that had a gap of 7 mm are shown to be essentially uniform for voltages up to 70 kV with no significant space charge distortion. The Kerr constant B of liquid nitrogen is constant over the AC modulation frequency range of 1-20 kHz, while increasing above 20 kHz. This change of B with the modulation frequency coincides with the frequency-amplitude gain characteristic of the lock-in amplifier used, so that B is independent of the AC modulation frequency within the range of this study. B monotonically decreases with increasing temperature, T, thus decreasing liquid nitrogen density, rho , so that B is related linearly to rho /T. The polarizability anisotropy of liquid nitrogen is evaluated to be 8.3*10/sup -41/ F-m/sup 2/ from the slope of the B-( rho /T) characteristic, obtained from a simple physical model.<>
{"title":"Kerr constant frequency dependence in liquid nitrogen","authors":"K. Imai, A. Kanematsu, M. Nawata, M. Zahn","doi":"10.1109/ICPADM.1991.172042","DOIUrl":"https://doi.org/10.1109/ICPADM.1991.172042","url":null,"abstract":"Kerr electro-optic field mapping measurements using the sensitive AC modulation method were made in liquid nitrogen. The steady-state electric fields between parallel stainless steel electrodes that had a gap of 7 mm are shown to be essentially uniform for voltages up to 70 kV with no significant space charge distortion. The Kerr constant B of liquid nitrogen is constant over the AC modulation frequency range of 1-20 kHz, while increasing above 20 kHz. This change of B with the modulation frequency coincides with the frequency-amplitude gain characteristic of the lock-in amplifier used, so that B is independent of the AC modulation frequency within the range of this study. B monotonically decreases with increasing temperature, T, thus decreasing liquid nitrogen density, rho , so that B is related linearly to rho /T. The polarizability anisotropy of liquid nitrogen is evaluated to be 8.3*10/sup -41/ F-m/sup 2/ from the slope of the B-( rho /T) characteristic, obtained from a simple physical model.<<ETX>>","PeriodicalId":6450,"journal":{"name":"[1991] Proceedings of the 3rd International Conference on Properties and Applications of Dielectric Materials","volume":"322 1","pages":"280-283 vol.1"},"PeriodicalIF":0.0,"publicationDate":"1991-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80269078","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 : 1991-07-08DOI: 10.1109/ICPADM.1991.172039
K. Kojima, A. Maeda, M. Ieda
Electroluminescence and electrical conduction in TCNQ (tetracyanoquinodimethane) thin films prepared by the vacuum-evaporation technique were investigated. The electrical properties depended strongly on the thin film deposition conditions, such as deposition rate and/or temperature and substrate temperature. The conduction currents were also affected by the electrode materials. Higher conductivity was observed in the specimen with a Cu anode than in that with Au or Al. The thermally stimulated current showed two peaks, at -120 and -20 degrees C. The trap depths were estimated as 0.10 and 0.22 eV, respectively. X-ray diffraction studies showed that the specimen prepared at 280 degrees C was crystalline, but the one prepared at 180 degrees C was amorphous. An infrared absorption analysis showed that the main chemical composition of TCNQ has been largely preserved in the vacuum-evaporated films.<>
{"title":"Electrical properties of TCNQ evaporated thin films","authors":"K. Kojima, A. Maeda, M. Ieda","doi":"10.1109/ICPADM.1991.172039","DOIUrl":"https://doi.org/10.1109/ICPADM.1991.172039","url":null,"abstract":"Electroluminescence and electrical conduction in TCNQ (tetracyanoquinodimethane) thin films prepared by the vacuum-evaporation technique were investigated. The electrical properties depended strongly on the thin film deposition conditions, such as deposition rate and/or temperature and substrate temperature. The conduction currents were also affected by the electrode materials. Higher conductivity was observed in the specimen with a Cu anode than in that with Au or Al. The thermally stimulated current showed two peaks, at -120 and -20 degrees C. The trap depths were estimated as 0.10 and 0.22 eV, respectively. X-ray diffraction studies showed that the specimen prepared at 280 degrees C was crystalline, but the one prepared at 180 degrees C was amorphous. An infrared absorption analysis showed that the main chemical composition of TCNQ has been largely preserved in the vacuum-evaporated films.<<ETX>>","PeriodicalId":6450,"journal":{"name":"[1991] Proceedings of the 3rd International Conference on Properties and Applications of Dielectric Materials","volume":"25 1","pages":"185-188 vol.1"},"PeriodicalIF":0.0,"publicationDate":"1991-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84003404","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 : 1991-07-08DOI: 10.1109/ICPADM.1991.172048
C. Mazzetti, M. Pompili, E. Forster
Some studies have suggested that there may exist a relationship between conduction and electrical breakdown. Before such a correlation between these phenomena and partial discharges (PDs) can be investigated, it is necessary to produce reproducible PD data. For this reason an investigation was undertaken to study the behavior of some well-defined dielectric fluids such as phenyl xylene ethane, ditolyl ether, mono and dibenzyl toluene, and perfluoro polyether in the pure state. Some preliminary results of this study are presented, and their significance is discussed in detail.<>
{"title":"Electric conduction breakdown and partial discharges in dielectric fluids. I. Partial discharges","authors":"C. Mazzetti, M. Pompili, E. Forster","doi":"10.1109/ICPADM.1991.172048","DOIUrl":"https://doi.org/10.1109/ICPADM.1991.172048","url":null,"abstract":"Some studies have suggested that there may exist a relationship between conduction and electrical breakdown. Before such a correlation between these phenomena and partial discharges (PDs) can be investigated, it is necessary to produce reproducible PD data. For this reason an investigation was undertaken to study the behavior of some well-defined dielectric fluids such as phenyl xylene ethane, ditolyl ether, mono and dibenzyl toluene, and perfluoro polyether in the pure state. Some preliminary results of this study are presented, and their significance is discussed in detail.<<ETX>>","PeriodicalId":6450,"journal":{"name":"[1991] Proceedings of the 3rd International Conference on Properties and Applications of Dielectric Materials","volume":"45 9 1","pages":"261-263 vol.1"},"PeriodicalIF":0.0,"publicationDate":"1991-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82742734","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 : 1991-07-08DOI: 10.1109/ICPADM.1991.172352
S. Bamji, A. Bulinski, Y. Chen, R. Densley
A mechanism of degradation in polymeric insulation at fields lower than required for hot-electron transport is shown. Cable grade low-density polyethylene was aged under divergent and uniform fields, using needle-plane and dimple-plane geometries, respectively. It is shown that, at points of electric stress enhancement in the polymer, the light emitted during the initiation phase of electrical treeing is not due to hot-electron impact but is due to the recombination of electrons and holes injected into the material. The spectra of the emitted light are in the visible and ultraviolet ranges. The ultraviolet light can photodegrade the polymer and lead to electrical treeing. Long-term aging of polyethylene, under divergent and uniform fields, indicates that treeing does not occur at fields below the light inception level. However, above this level an electrical tree always develops and the time to treeing depends on the voltage applied to the polymer.<>
{"title":"Photodegradation versus hot-electron impact for electrical tree inception at low electric fields","authors":"S. Bamji, A. Bulinski, Y. Chen, R. Densley","doi":"10.1109/ICPADM.1991.172352","DOIUrl":"https://doi.org/10.1109/ICPADM.1991.172352","url":null,"abstract":"A mechanism of degradation in polymeric insulation at fields lower than required for hot-electron transport is shown. Cable grade low-density polyethylene was aged under divergent and uniform fields, using needle-plane and dimple-plane geometries, respectively. It is shown that, at points of electric stress enhancement in the polymer, the light emitted during the initiation phase of electrical treeing is not due to hot-electron impact but is due to the recombination of electrons and holes injected into the material. The spectra of the emitted light are in the visible and ultraviolet ranges. The ultraviolet light can photodegrade the polymer and lead to electrical treeing. Long-term aging of polyethylene, under divergent and uniform fields, indicates that treeing does not occur at fields below the light inception level. However, above this level an electrical tree always develops and the time to treeing depends on the voltage applied to the polymer.<<ETX>>","PeriodicalId":6450,"journal":{"name":"[1991] Proceedings of the 3rd International Conference on Properties and Applications of Dielectric Materials","volume":"1 1","pages":"51-54 vol.1"},"PeriodicalIF":0.0,"publicationDate":"1991-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82965759","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 : 1991-07-08DOI: 10.1109/ICPADM.1991.172267
H. Ogura, A. Chiba, K. Kase
The ferroelectric properties of polyvinylidene fluoride (PVDF) and vinylidene fluoride/trifluoroethylene (VDF/TrFE) copolymers were investigated, with special emphasis on their local electric field and phase transition behavior. The objective of this work was (1) to find the theoretical values of the spontaneous polarization of PVDF and VDF/TrFE copolymers; (2) to evaluate experimentally the Lorentz factor for PVDF beta -phase crystal, which relates the local electric field to the spontaneous polarization; and (3) to investigate the influence of the electrostatic interactions on ferroelectric-to-paraelectric phase transition of VDF/TrFE copolymers.<>
{"title":"Study of the local electric field and the Curie transition of ferroelectric polymers","authors":"H. Ogura, A. Chiba, K. Kase","doi":"10.1109/ICPADM.1991.172267","DOIUrl":"https://doi.org/10.1109/ICPADM.1991.172267","url":null,"abstract":"The ferroelectric properties of polyvinylidene fluoride (PVDF) and vinylidene fluoride/trifluoroethylene (VDF/TrFE) copolymers were investigated, with special emphasis on their local electric field and phase transition behavior. The objective of this work was (1) to find the theoretical values of the spontaneous polarization of PVDF and VDF/TrFE copolymers; (2) to evaluate experimentally the Lorentz factor for PVDF beta -phase crystal, which relates the local electric field to the spontaneous polarization; and (3) to investigate the influence of the electrostatic interactions on ferroelectric-to-paraelectric phase transition of VDF/TrFE copolymers.<<ETX>>","PeriodicalId":6450,"journal":{"name":"[1991] Proceedings of the 3rd International Conference on Properties and Applications of Dielectric Materials","volume":"54 6","pages":"1097-1100 vol.2"},"PeriodicalIF":0.0,"publicationDate":"1991-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91464949","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 : 1991-07-08DOI: 10.1109/ICPADM.1991.172098
C. Nucci, S. Pirani, M. Rinaldi
An explanation of the disconnection of 'sprayed ends' from the electrode edges of metallized polypropylene capacitors is given. Experimental observations using transparent cells and post-test analyses of the end-edge contacts show that the disconnection is due to erosion caused by electric sparks. The sparks are a consequence of the irregular nature of the contacts and of high intensities of the current flowing through them. Results of laboratory tests show that the degradation of the contacts is related to the peak value of the current pulses, in agreement with the above explanation. In addition, the results confirm that the degradation is not related to the energy content of the applied pulses.<>
{"title":"Electrode-end contact degradation of metallized polypropylene capacitors in power applications","authors":"C. Nucci, S. Pirani, M. Rinaldi","doi":"10.1109/ICPADM.1991.172098","DOIUrl":"https://doi.org/10.1109/ICPADM.1991.172098","url":null,"abstract":"An explanation of the disconnection of 'sprayed ends' from the electrode edges of metallized polypropylene capacitors is given. Experimental observations using transparent cells and post-test analyses of the end-edge contacts show that the disconnection is due to erosion caused by electric sparks. The sparks are a consequence of the irregular nature of the contacts and of high intensities of the current flowing through them. Results of laboratory tests show that the degradation of the contacts is related to the peak value of the current pulses, in agreement with the above explanation. In addition, the results confirm that the degradation is not related to the energy content of the applied pulses.<<ETX>>","PeriodicalId":6450,"journal":{"name":"[1991] Proceedings of the 3rd International Conference on Properties and Applications of Dielectric Materials","volume":"60 1","pages":"466-469 vol.1"},"PeriodicalIF":0.0,"publicationDate":"1991-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91237903","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 : 1991-07-08DOI: 10.1109/ICPADM.1991.172254
Yang Baitun, Liufu De, T. Demin, Liu Yaonan
The phenomenon of PET (polyethylene terephthalate) breakdown during short circuit discharge is studied. A theoretical model for detrapping by collisional ionization is proposed for interpretation of the breakdown mechanism. The coefficient for detrapping by collisional ionization and the relation between it and the velocity of the discharging are obtained. A critical electric field of the short circuit breakdown by space charges due to collisional ionization by detrapping is also suggested for solid dielectrics, and confirmed experimentally. The critical field is directly proportional to the thickness of the dielectric and inversely proportional to the detrapping coefficient of the collisional ionization, the time constant of the discharging circuit, and the dielectric constant.<>
{"title":"Breakdown mechanism of the charged solid dielectric during short circuit discharge","authors":"Yang Baitun, Liufu De, T. Demin, Liu Yaonan","doi":"10.1109/ICPADM.1991.172254","DOIUrl":"https://doi.org/10.1109/ICPADM.1991.172254","url":null,"abstract":"The phenomenon of PET (polyethylene terephthalate) breakdown during short circuit discharge is studied. A theoretical model for detrapping by collisional ionization is proposed for interpretation of the breakdown mechanism. The coefficient for detrapping by collisional ionization and the relation between it and the velocity of the discharging are obtained. A critical electric field of the short circuit breakdown by space charges due to collisional ionization by detrapping is also suggested for solid dielectrics, and confirmed experimentally. The critical field is directly proportional to the thickness of the dielectric and inversely proportional to the detrapping coefficient of the collisional ionization, the time constant of the discharging circuit, and the dielectric constant.<<ETX>>","PeriodicalId":6450,"journal":{"name":"[1991] Proceedings of the 3rd International Conference on Properties and Applications of Dielectric Materials","volume":"62 1","pages":"1048-1051 vol.2"},"PeriodicalIF":0.0,"publicationDate":"1991-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76952452","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：