Pub Date : 1994-07-03DOI: 10.1109/ICPADM.1994.414102
T. Kawasaki, T. Terashima, T. Takada, T. Maeno
A visualization and a quantification technique of a latent electric charge image on a dielectric material has been developed by using Pockels effect and a computer image processing. An optical phase modulation technique and computer image lock-in amplifier processing were used to improve the signal to noise ratio. The measurement system has several improved performances: a sensitivity of surface charge of 1 nC cm/sup -2/; a spatial resolution of 200 /spl mu/m; and discrimination of the charge polarity. The basic principle of advanced electrooptic surface charge measurement is described and the typical surface charge distribution of a positive discharge streamer produced by an impulse high voltage (5 kV/sub peak/) is demonstrated. A comparison is also made between the modulation method and the nonmodulation method.<>
{"title":"Visualization of surface charge distribution on insulating films using spatial optical phase modulation system","authors":"T. Kawasaki, T. Terashima, T. Takada, T. Maeno","doi":"10.1109/ICPADM.1994.414102","DOIUrl":"https://doi.org/10.1109/ICPADM.1994.414102","url":null,"abstract":"A visualization and a quantification technique of a latent electric charge image on a dielectric material has been developed by using Pockels effect and a computer image processing. An optical phase modulation technique and computer image lock-in amplifier processing were used to improve the signal to noise ratio. The measurement system has several improved performances: a sensitivity of surface charge of 1 nC cm/sup -2/; a spatial resolution of 200 /spl mu/m; and discrimination of the charge polarity. The basic principle of advanced electrooptic surface charge measurement is described and the typical surface charge distribution of a positive discharge streamer produced by an impulse high voltage (5 kV/sub peak/) is demonstrated. A comparison is also made between the modulation method and the nonmodulation method.<<ETX>>","PeriodicalId":331058,"journal":{"name":"Proceedings of 1994 4th International Conference on Properties and Applications of Dielectric Materials (ICPADM)","volume":"341 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122996215","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 : 1994-07-03DOI: 10.1109/ICPADM.1994.414080
H. J. van der Merwe, J. Drommi, A. Wolmarans
The Electricity Supply Commission of South Africa (Eskom) and Electricite de France (EDF) are involved in a technical exchange agreement whereby the effectiveness of the EDF method for stator winding insulation condition assessment, specifically on turbogenerators, will be investigated. This method basically entails off-line electrical quadratic rate partial discharge measurements, using relatively low center-frequency narrow band filters. Initial experience gained through measurements on two turbogenerators of Eskom in South Africa, has shown the ability of this method to accurately indicate the insulation condition of stator windings. On one of the generators tested, excellent correlation was found between the indications of test results and the findings of a stator bar visual inspection and dissection. Dissipation factor and conventional peak-value partial discharge measurements have in the past failed to indicate the extend of insulation damage (discovered through visual inspections) of this specific winding.<>
{"title":"Initial experience with quadratic rate partial discharge tests on the stator winding insulation of power generators in South Africa","authors":"H. J. van der Merwe, J. Drommi, A. Wolmarans","doi":"10.1109/ICPADM.1994.414080","DOIUrl":"https://doi.org/10.1109/ICPADM.1994.414080","url":null,"abstract":"The Electricity Supply Commission of South Africa (Eskom) and Electricite de France (EDF) are involved in a technical exchange agreement whereby the effectiveness of the EDF method for stator winding insulation condition assessment, specifically on turbogenerators, will be investigated. This method basically entails off-line electrical quadratic rate partial discharge measurements, using relatively low center-frequency narrow band filters. Initial experience gained through measurements on two turbogenerators of Eskom in South Africa, has shown the ability of this method to accurately indicate the insulation condition of stator windings. On one of the generators tested, excellent correlation was found between the indications of test results and the findings of a stator bar visual inspection and dissection. Dissipation factor and conventional peak-value partial discharge measurements have in the past failed to indicate the extend of insulation damage (discovered through visual inspections) of this specific winding.<<ETX>>","PeriodicalId":331058,"journal":{"name":"Proceedings of 1994 4th International Conference on Properties and Applications of Dielectric Materials (ICPADM)","volume":"127 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122493645","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 : 1994-07-03DOI: 10.1109/ICPADM.1994.414149
P. G. Lang, D. Allan, Y. Zhou
This paper examines the possibility of remote detection of defective disc insulators on overhead transmission lines. Application of infrared thermal imaging systems is studied in relation to the very small temperature differentials between sound and faulty discs, and the many influencing factors that significantly reduce sensitivity. The application of corona detection techniques appears to present a complementary approach. The objective is to understand the mechanisms involved in order to develop more cost-effective diagnostic techniques for this class of equipment.<>
{"title":"The investigation of insulation defects in transmission line disc insulators using remote detection techniques","authors":"P. G. Lang, D. Allan, Y. Zhou","doi":"10.1109/ICPADM.1994.414149","DOIUrl":"https://doi.org/10.1109/ICPADM.1994.414149","url":null,"abstract":"This paper examines the possibility of remote detection of defective disc insulators on overhead transmission lines. Application of infrared thermal imaging systems is studied in relation to the very small temperature differentials between sound and faulty discs, and the many influencing factors that significantly reduce sensitivity. The application of corona detection techniques appears to present a complementary approach. The objective is to understand the mechanisms involved in order to develop more cost-effective diagnostic techniques for this class of equipment.<<ETX>>","PeriodicalId":331058,"journal":{"name":"Proceedings of 1994 4th International Conference on Properties and Applications of Dielectric Materials (ICPADM)","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123860881","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 : 1994-07-03DOI: 10.1109/ICPADM.1994.414030
H. Kawamura, M. Nawata
The space charge in water tree degraded LDPE has been measured by the thermally stimulated current (TSC) method. The shape of the TSC spectra does not change with the degradation of polymeric insulation containing water trees, but the TSC peak increases linearly with the increase of the length of the water tree. It is shown that the TSC measuring method can adapt to evaluate the degradation caused by water treeing.<>
{"title":"Space charge accumulation in water tree degraded LDPE and its evaluation by TSC method","authors":"H. Kawamura, M. Nawata","doi":"10.1109/ICPADM.1994.414030","DOIUrl":"https://doi.org/10.1109/ICPADM.1994.414030","url":null,"abstract":"The space charge in water tree degraded LDPE has been measured by the thermally stimulated current (TSC) method. The shape of the TSC spectra does not change with the degradation of polymeric insulation containing water trees, but the TSC peak increases linearly with the increase of the length of the water tree. It is shown that the TSC measuring method can adapt to evaluate the degradation caused by water treeing.<<ETX>>","PeriodicalId":331058,"journal":{"name":"Proceedings of 1994 4th International Conference on Properties and Applications of Dielectric Materials (ICPADM)","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125749656","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 : 1994-07-03DOI: 10.1109/ICPADM.1994.414123
A. Kuitunen, J. Partanen
The effect of the lifetime of medium voltage underground cable networks on the network costs is studied. The cable manufacturer has estimated how much the cost of manufacturing the medium voltage XLPE power cable changes as a function of the cable lifetime. The shorter the lifetime, the cheaper the cable is, but a short lifetime leads to higher construction costs because the cable network must be rebuilt more frequently. The costs due to the cable network are represented by a simplified cost function, where the lifetime of the cable is a variable. The optimal lifetime of the medium voltage cable network is determined by minimizing the cost function over a long period of time. Besides the economic dimensioning of the underground cable network, the technical constraints and the effect of the lifetime of the cable network on the network configuration should be taken into account when minimizing the cost function. No real optimization method appears to exist for the problem. A network design program written at Tampere University of Technology (TUT) and a test network were therefore utilized in solving the problem.<>
{"title":"The optimal lifetime of the medium voltage underground cable networks of utilities","authors":"A. Kuitunen, J. Partanen","doi":"10.1109/ICPADM.1994.414123","DOIUrl":"https://doi.org/10.1109/ICPADM.1994.414123","url":null,"abstract":"The effect of the lifetime of medium voltage underground cable networks on the network costs is studied. The cable manufacturer has estimated how much the cost of manufacturing the medium voltage XLPE power cable changes as a function of the cable lifetime. The shorter the lifetime, the cheaper the cable is, but a short lifetime leads to higher construction costs because the cable network must be rebuilt more frequently. The costs due to the cable network are represented by a simplified cost function, where the lifetime of the cable is a variable. The optimal lifetime of the medium voltage cable network is determined by minimizing the cost function over a long period of time. Besides the economic dimensioning of the underground cable network, the technical constraints and the effect of the lifetime of the cable network on the network configuration should be taken into account when minimizing the cost function. No real optimization method appears to exist for the problem. A network design program written at Tampere University of Technology (TUT) and a test network were therefore utilized in solving the problem.<<ETX>>","PeriodicalId":331058,"journal":{"name":"Proceedings of 1994 4th International Conference on Properties and Applications of Dielectric Materials (ICPADM)","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129739517","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 : 1994-07-03DOI: 10.1109/ICPADM.1994.414074
M. Hikita, H. Yamashita, T. Kato, N. Hayakawa, T. Ueda, H. Okubo
The authors measured electromagnetic spectrum radiated from partial discharge with a magnitude from 80 to 50,000 pC occurring in needle-plane electrodes. Experimental results showed that the gain of the electromagnetic wave decreased with increasing the distance from PD source in the frequency range from 35 to 50 MHz. The results were discussed in terms of a model assuming that electromagnetic wave radiation from a small dipole antenna simulates that from the PD source. Consequently, the distance characteristics of the signal gain proved to agree well with the theoretical calculation. An attempt was also made to measure separately the electromagnetic spectrum caused by positive and negative PD pulses. At the same time, PD pulses were measured with a computer-aided measuring system. The authors discussed the relationship between the PD statistical characteristics and the electromagnetic spectrum.<>
{"title":"Electromagnetic spectrum caused by partial discharge in air under AC and DC voltage application","authors":"M. Hikita, H. Yamashita, T. Kato, N. Hayakawa, T. Ueda, H. Okubo","doi":"10.1109/ICPADM.1994.414074","DOIUrl":"https://doi.org/10.1109/ICPADM.1994.414074","url":null,"abstract":"The authors measured electromagnetic spectrum radiated from partial discharge with a magnitude from 80 to 50,000 pC occurring in needle-plane electrodes. Experimental results showed that the gain of the electromagnetic wave decreased with increasing the distance from PD source in the frequency range from 35 to 50 MHz. The results were discussed in terms of a model assuming that electromagnetic wave radiation from a small dipole antenna simulates that from the PD source. Consequently, the distance characteristics of the signal gain proved to agree well with the theoretical calculation. An attempt was also made to measure separately the electromagnetic spectrum caused by positive and negative PD pulses. At the same time, PD pulses were measured with a computer-aided measuring system. The authors discussed the relationship between the PD statistical characteristics and the electromagnetic spectrum.<<ETX>>","PeriodicalId":331058,"journal":{"name":"Proceedings of 1994 4th International Conference on Properties and Applications of Dielectric Materials (ICPADM)","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129572594","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 : 1994-07-03DOI: 10.1109/ICPADM.1994.414037
T. Czaszejko
A laboratory experiment was performed in order to determine the influence of a short exposure to DC voltage on the growth of water trees in XLPE cable insulation. The results are of some practical importance, for a DC test voltage is commonly used by utilities when re-commissioning polymeric cable systems which have been previously energised. An accelerated water tree growth from a needle electrode was induced on the surface of samples of cable insulation. At various stages of water tree growth the DC voltage of 4U/sub 0/ (where U/sub 0/ is the rms rated voltage of the cable) was applied for duration of 15 minutes. After the DC exposure, water tree aging continued under AC conditions, and amounted to a total of 296 hours for each sample. The results have shown that there is an increase in the length of water trees grown in samples subjected to a DC voltage compared with the control sample aged, for the same period of time, without the DC exposure.<>
{"title":"Growth of water trees exposed to DC voltage","authors":"T. Czaszejko","doi":"10.1109/ICPADM.1994.414037","DOIUrl":"https://doi.org/10.1109/ICPADM.1994.414037","url":null,"abstract":"A laboratory experiment was performed in order to determine the influence of a short exposure to DC voltage on the growth of water trees in XLPE cable insulation. The results are of some practical importance, for a DC test voltage is commonly used by utilities when re-commissioning polymeric cable systems which have been previously energised. An accelerated water tree growth from a needle electrode was induced on the surface of samples of cable insulation. At various stages of water tree growth the DC voltage of 4U/sub 0/ (where U/sub 0/ is the rms rated voltage of the cable) was applied for duration of 15 minutes. After the DC exposure, water tree aging continued under AC conditions, and amounted to a total of 296 hours for each sample. The results have shown that there is an increase in the length of water trees grown in samples subjected to a DC voltage compared with the control sample aged, for the same period of time, without the DC exposure.<<ETX>>","PeriodicalId":331058,"journal":{"name":"Proceedings of 1994 4th International Conference on Properties and Applications of Dielectric Materials (ICPADM)","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124628343","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 : 1994-07-03DOI: 10.1109/ICPADM.1994.414076
B. Fruth, D. Gross
The 'partial discharge pattern recording technique' is applicable to electrical insulation field measurements, particularly if combined with disturbance rejection and nonconventional pick-ups. Electromagnetic disturbances are eliminated by filtering in the time domain (impulse noise gating) and/or in the frequency domain (down-mixing). PD patterns not only help to identify the defect type but also serve to evaluate the efficiency of a disturbance rejection procedure.<>
{"title":"Phase resolving partial discharge pattern acquisition and frequency spectrum analysis","authors":"B. Fruth, D. Gross","doi":"10.1109/ICPADM.1994.414076","DOIUrl":"https://doi.org/10.1109/ICPADM.1994.414076","url":null,"abstract":"The 'partial discharge pattern recording technique' is applicable to electrical insulation field measurements, particularly if combined with disturbance rejection and nonconventional pick-ups. Electromagnetic disturbances are eliminated by filtering in the time domain (impulse noise gating) and/or in the frequency domain (down-mixing). PD patterns not only help to identify the defect type but also serve to evaluate the efficiency of a disturbance rejection procedure.<<ETX>>","PeriodicalId":331058,"journal":{"name":"Proceedings of 1994 4th International Conference on Properties and Applications of Dielectric Materials (ICPADM)","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122154522","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 : 1994-07-03DOI: 10.1109/ICPADM.1994.413989
L. Audouin, J. Verdu
Initial weight loss kinetics of industrial extruded samples of poly(vinyl chloride) (PVC) plasticized respectively by 15, 20, 25 and 30 weight % of di(2-ethyl hexyl)phthalate, dinonylphthalate, didecylphthalate and diundecylphthalate were studied at 85, 95, 105 and 120/spl deg/C. Principally two distinct kinetic regimes of weight loss were observed: Regime 1 characterized by weight loss proportional to time and corresponding to a process controlled by evaporation. This regime predominates for high molecular weight plasticizers especially at high plasticizer concentrations (/spl ges/20 weight %). Regime 2, in which the weight loss is proportional to a square root of time, is typical for kinetic control by diffusion according to Fickian law. It was observed for low molecular weight plasticizers at low concentrations (/spl les/20 weight %). The depth distribution of plasticizer in the bulk sample depends also of the principal kinetic regime. In all samples in which evaporation controlled weight loss was observed, the plasticizer concentration was rather homogeneously distributed into the sample depth. On the contrary, the important decrease of plasticizer concentration in the superficial layers was observed in all cases of diffusion controlled of plasticizer loss.<>
{"title":"Thermal ageing of plasticized PVC: effect of loss kinetics on plasticizer depth distribution","authors":"L. Audouin, J. Verdu","doi":"10.1109/ICPADM.1994.413989","DOIUrl":"https://doi.org/10.1109/ICPADM.1994.413989","url":null,"abstract":"Initial weight loss kinetics of industrial extruded samples of poly(vinyl chloride) (PVC) plasticized respectively by 15, 20, 25 and 30 weight % of di(2-ethyl hexyl)phthalate, dinonylphthalate, didecylphthalate and diundecylphthalate were studied at 85, 95, 105 and 120/spl deg/C. Principally two distinct kinetic regimes of weight loss were observed: Regime 1 characterized by weight loss proportional to time and corresponding to a process controlled by evaporation. This regime predominates for high molecular weight plasticizers especially at high plasticizer concentrations (/spl ges/20 weight %). Regime 2, in which the weight loss is proportional to a square root of time, is typical for kinetic control by diffusion according to Fickian law. It was observed for low molecular weight plasticizers at low concentrations (/spl les/20 weight %). The depth distribution of plasticizer in the bulk sample depends also of the principal kinetic regime. In all samples in which evaporation controlled weight loss was observed, the plasticizer concentration was rather homogeneously distributed into the sample depth. On the contrary, the important decrease of plasticizer concentration in the superficial layers was observed in all cases of diffusion controlled of plasticizer loss.<<ETX>>","PeriodicalId":331058,"journal":{"name":"Proceedings of 1994 4th International Conference on Properties and Applications of Dielectric Materials (ICPADM)","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122383239","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 : 1994-07-03DOI: 10.1109/ICPADM.1994.414148
L. Lamarre, D. Fournier, R. Morin
Underground power distribution cable joints, which showed detectable levels of partial discharges (PD) in service, were removed and submitted to an accelerated ageing test in a laboratory. Prior to, and after ageing, the joints were examined by X-rays to check for any cavity or air gap that could be the site of PD generation. During ageing, the joints were simultaneously monitored with an infrared camera to locate any hot spot, and with a portable partial discharge detector, to locate precisely the areas of PD generation. The ageing test comprises overstressing at 3 p.u. and thermal cycling at 130/spl deg/C and lasts until joint failure. The aim is to attempt to define a critical PD threshold (as measured by the portable instrument) at which failure is imminent.<>
{"title":"Early detection of faults in underground distribution cable joints by partial discharge measurements","authors":"L. Lamarre, D. Fournier, R. Morin","doi":"10.1109/ICPADM.1994.414148","DOIUrl":"https://doi.org/10.1109/ICPADM.1994.414148","url":null,"abstract":"Underground power distribution cable joints, which showed detectable levels of partial discharges (PD) in service, were removed and submitted to an accelerated ageing test in a laboratory. Prior to, and after ageing, the joints were examined by X-rays to check for any cavity or air gap that could be the site of PD generation. During ageing, the joints were simultaneously monitored with an infrared camera to locate any hot spot, and with a portable partial discharge detector, to locate precisely the areas of PD generation. The ageing test comprises overstressing at 3 p.u. and thermal cycling at 130/spl deg/C and lasts until joint failure. The aim is to attempt to define a critical PD threshold (as measured by the portable instrument) at which failure is imminent.<<ETX>>","PeriodicalId":331058,"journal":{"name":"Proceedings of 1994 4th International Conference on Properties and Applications of Dielectric Materials (ICPADM)","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121153235","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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