Pub Date : 1997-11-01DOI: 10.1109/PVSC.1997.653915
T. Krygowski, A. Rohaigi, D. Ruby
A technique is presented to simultaneously diffuse boron and phosphorus in silicon, and grow an in-situ passivating oxide in a single furnace step. It is shown that limited solid doping sources made from P and B spin-on-dopant (SOD) films can produce optimal n/sup +/ and p/sup +/ profiles simultaneously without the deleterious effects of cross doping. A high quality passivating oxide is grown in-situ beneath the thin (/spl sim/60 /spl Aring/) diffusion glass, resulting in low J/sub 0/ values below 100 fA/cm/sup 2/ for transparent (/spl sim/100 /spl Omega///spl square/) phosphorus and boron diffusions. For the first time it is shown that impurities present in the boron SOD film can be effectively filtered out by employing separate source wafers, resulting in bulk lifetimes in excess of 1 ms for the sample wafers. The degree of lifetime degradation in the sources is related to the gettering efficiency of boron in silicon. This novel simultaneous diffusion, in-situ oxidation, impurity filtering and gettering technique was successfully used to produce 20.3% Fz, and 19.1% Cz solar cells, in one furnace step.
{"title":"Simultaneous P and B diffusion, in-situ surface passivation, impurity filtering and gettering for high-efficiency silicon solar cells","authors":"T. Krygowski, A. Rohaigi, D. Ruby","doi":"10.1109/PVSC.1997.653915","DOIUrl":"https://doi.org/10.1109/PVSC.1997.653915","url":null,"abstract":"A technique is presented to simultaneously diffuse boron and phosphorus in silicon, and grow an in-situ passivating oxide in a single furnace step. It is shown that limited solid doping sources made from P and B spin-on-dopant (SOD) films can produce optimal n/sup +/ and p/sup +/ profiles simultaneously without the deleterious effects of cross doping. A high quality passivating oxide is grown in-situ beneath the thin (/spl sim/60 /spl Aring/) diffusion glass, resulting in low J/sub 0/ values below 100 fA/cm/sup 2/ for transparent (/spl sim/100 /spl Omega///spl square/) phosphorus and boron diffusions. For the first time it is shown that impurities present in the boron SOD film can be effectively filtered out by employing separate source wafers, resulting in bulk lifetimes in excess of 1 ms for the sample wafers. The degree of lifetime degradation in the sources is related to the gettering efficiency of boron in silicon. This novel simultaneous diffusion, in-situ oxidation, impurity filtering and gettering technique was successfully used to produce 20.3% Fz, and 19.1% Cz solar cells, in one furnace step.","PeriodicalId":251166,"journal":{"name":"Conference Record of the Twenty Sixth IEEE Photovoltaic Specialists Conference - 1997","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124424602","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 : 1997-11-01DOI: 10.1109/PVSC.1997.654276
J. Gee, S. E. Garrett, W. P. Morgan
The authors are developing new module concepts that encapsulate and electrically connect all the crystalline-silicon (c-Si) photovoltaic (PV) cells in a module in a single step. The new assembly process: (1) uses back-contact c-Si cells; (2) uses a module backplane that has both the electrical circuit, encapsulant and backsheet in a single piece; and (3) uses a single-step process for assembly of these components into a module. This new process reduces module assembly cost by using planar processes that are easy to automate, by reducing the number of steps, and by eliminating low-throughput (e.g., individual cell tabbing, cell stringing, etc.) steps. They refer to this process as "monolithic module assembly" since it translates many of the advantages of monolithic module construction of thin-film PV modules to wafered c-Si PV modules. Preliminary development of the new module assembly process, and some estimations of the cost potential of the new process, are presented.
{"title":"Simplified module assembly using back-contact crystalline-silicon solar cells","authors":"J. Gee, S. E. Garrett, W. P. Morgan","doi":"10.1109/PVSC.1997.654276","DOIUrl":"https://doi.org/10.1109/PVSC.1997.654276","url":null,"abstract":"The authors are developing new module concepts that encapsulate and electrically connect all the crystalline-silicon (c-Si) photovoltaic (PV) cells in a module in a single step. The new assembly process: (1) uses back-contact c-Si cells; (2) uses a module backplane that has both the electrical circuit, encapsulant and backsheet in a single piece; and (3) uses a single-step process for assembly of these components into a module. This new process reduces module assembly cost by using planar processes that are easy to automate, by reducing the number of steps, and by eliminating low-throughput (e.g., individual cell tabbing, cell stringing, etc.) steps. They refer to this process as \"monolithic module assembly\" since it translates many of the advantages of monolithic module construction of thin-film PV modules to wafered c-Si PV modules. Preliminary development of the new module assembly process, and some estimations of the cost potential of the new process, are presented.","PeriodicalId":251166,"journal":{"name":"Conference Record of the Twenty Sixth IEEE Photovoltaic Specialists Conference - 1997","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116346619","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 : 1997-11-01DOI: 10.1109/PVSC.1997.654281
J. Wiles, D. King
Instructions and labels supplied with listed PV modules and the requirements of the National Electrical Code (NEC) dictate that a series fuse shall be used to protect the module against backfeed currents. Few of the hundreds of thousands of low-voltage (12, 24, and 48-volt) stand-alone photovoltaic (PV) power systems use series fuses on each module or string of modules. Tests and simulations at the Southwest Technology Development Institute (TDI) and at Sandia National Laboratories (SNL) have established that the absence of these fuses can pose significant fire and safety hazards even on 12-volt PV systems. If the system has sufficient backfeed voltage and current, it is possible that a ground fault in the wiring or inside a module can result in the destruction of a PV module.
{"title":"Blocking diodes and fuses in low-voltage PV systems","authors":"J. Wiles, D. King","doi":"10.1109/PVSC.1997.654281","DOIUrl":"https://doi.org/10.1109/PVSC.1997.654281","url":null,"abstract":"Instructions and labels supplied with listed PV modules and the requirements of the National Electrical Code (NEC) dictate that a series fuse shall be used to protect the module against backfeed currents. Few of the hundreds of thousands of low-voltage (12, 24, and 48-volt) stand-alone photovoltaic (PV) power systems use series fuses on each module or string of modules. Tests and simulations at the Southwest Technology Development Institute (TDI) and at Sandia National Laboratories (SNL) have established that the absence of these fuses can pose significant fire and safety hazards even on 12-volt PV systems. If the system has sufficient backfeed voltage and current, it is possible that a ground fault in the wiring or inside a module can result in the destruction of a PV module.","PeriodicalId":251166,"journal":{"name":"Conference Record of the Twenty Sixth IEEE Photovoltaic Specialists Conference - 1997","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130983402","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 : 1997-11-01DOI: 10.1109/PVSC.1997.654323
D. King, D. R. Myers
Small, low-cost, silicon-photodiode pyranometers are now widely used for solar irradiance measurements associated with solar thermal and photovoltaic power systems, as well as for agricultural applications. Without correction, the irradiance values indicated by these pyranometers may differ from the "true" broadband solar irradiance by over 10%. This paper identifies the time-of-day dependent factors responsible for these systematic errors and describes new procedures that effectively compensate for the systematic influences. Application of the procedures should improve calibration methods and the accuracy of field measurements.
{"title":"Silicon-photodiode pyranometers: operational characteristics, historical experiences, and new calibration procedures","authors":"D. King, D. R. Myers","doi":"10.1109/PVSC.1997.654323","DOIUrl":"https://doi.org/10.1109/PVSC.1997.654323","url":null,"abstract":"Small, low-cost, silicon-photodiode pyranometers are now widely used for solar irradiance measurements associated with solar thermal and photovoltaic power systems, as well as for agricultural applications. Without correction, the irradiance values indicated by these pyranometers may differ from the \"true\" broadband solar irradiance by over 10%. This paper identifies the time-of-day dependent factors responsible for these systematic errors and describes new procedures that effectively compensate for the systematic influences. Application of the procedures should improve calibration methods and the accuracy of field measurements.","PeriodicalId":251166,"journal":{"name":"Conference Record of the Twenty Sixth IEEE Photovoltaic Specialists Conference - 1997","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131363986","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 : 1997-11-01DOI: 10.1109/PVSC.1997.654347
G. Palomino, J. Wiles, J. Stevens, F. Goodman
In 1995, Salt River Project (SRP), a public power utility located in Phoenix, Arizona, USA, collaborated with the Electric Power Research Institute (EPRI) and Sandia National Laboratories (Sandia) to initiate a research project to evaluate the feasibility of using a photovoltaic (PV) power system with battery energy storage to match PV output with residential customer peak energy demand periods. The PV power system, a 2.4 kW PV array with 25.2 kWh of energy storage, was designed and installed by the Southwest Technology Development Institute (SWTDI) at an SRP-owned facility, known as the Chandler Research House during August 1995. This paper presents an overview of the system design, operation and performance.
{"title":"Performance of a grid connected residential photovoltaic system with energy storage","authors":"G. Palomino, J. Wiles, J. Stevens, F. Goodman","doi":"10.1109/PVSC.1997.654347","DOIUrl":"https://doi.org/10.1109/PVSC.1997.654347","url":null,"abstract":"In 1995, Salt River Project (SRP), a public power utility located in Phoenix, Arizona, USA, collaborated with the Electric Power Research Institute (EPRI) and Sandia National Laboratories (Sandia) to initiate a research project to evaluate the feasibility of using a photovoltaic (PV) power system with battery energy storage to match PV output with residential customer peak energy demand periods. The PV power system, a 2.4 kW PV array with 25.2 kWh of energy storage, was designed and installed by the Southwest Technology Development Institute (SWTDI) at an SRP-owned facility, known as the Chandler Research House during August 1995. This paper presents an overview of the system design, operation and performance.","PeriodicalId":251166,"journal":{"name":"Conference Record of the Twenty Sixth IEEE Photovoltaic Specialists Conference - 1997","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132801552","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 : 1997-10-01DOI: 10.1109/PVSC.1997.654269
A. Maish, C. Atcitty, S. Hester, D. Greenberg, D. Osborn, D. Collier, M. Brine
This paper discusses the reliability of photovoltaic projects including SMUD's PV Pioneer project, various projects monitored by Ascension Technology, and the Colorado Parks project. System times-to-failure range from 1 to 16 years, and maintenance costs range from 1 to 16 cents per kilowatt-hour. Factors contributing to the reliability of these systems are discussed, and practices are recommended that can be applied to future projects. This paper also discusses the methodology used to collect and analyze PV system reliability data.
{"title":"Photovoltaic system reliability","authors":"A. Maish, C. Atcitty, S. Hester, D. Greenberg, D. Osborn, D. Collier, M. Brine","doi":"10.1109/PVSC.1997.654269","DOIUrl":"https://doi.org/10.1109/PVSC.1997.654269","url":null,"abstract":"This paper discusses the reliability of photovoltaic projects including SMUD's PV Pioneer project, various projects monitored by Ascension Technology, and the Colorado Parks project. System times-to-failure range from 1 to 16 years, and maintenance costs range from 1 to 16 cents per kilowatt-hour. Factors contributing to the reliability of these systems are discussed, and practices are recommended that can be applied to future projects. This paper also discusses the methodology used to collect and analyze PV system reliability data.","PeriodicalId":251166,"journal":{"name":"Conference Record of the Twenty Sixth IEEE Photovoltaic Specialists Conference - 1997","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114693246","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 : 1997-10-01DOI: 10.1109/PVSC.1997.654322
T. Hund, B. Thompson
An amp-hour counting battery charge control algorithm has been defined and tested using the Digital Solar Technologies MPR-9400 microprocessor based photovoltaic hybrid charge controller. This work included extensive laboratory and field testing of the charge algorithm on vented lead-antimony and valve regulated lead-acid batteries. The test results have shown that with proper setup, amp-hour counting charge control is more effective than conventional voltage regulated sub-array shedding in returning the lead-acid battery to a high state of charge.
{"title":"Amp-hour counting charge control for photovoltaic hybrid power systems","authors":"T. Hund, B. Thompson","doi":"10.1109/PVSC.1997.654322","DOIUrl":"https://doi.org/10.1109/PVSC.1997.654322","url":null,"abstract":"An amp-hour counting battery charge control algorithm has been defined and tested using the Digital Solar Technologies MPR-9400 microprocessor based photovoltaic hybrid charge controller. This work included extensive laboratory and field testing of the charge algorithm on vented lead-antimony and valve regulated lead-acid batteries. The test results have shown that with proper setup, amp-hour counting charge control is more effective than conventional voltage regulated sub-array shedding in returning the lead-acid battery to a high state of charge.","PeriodicalId":251166,"journal":{"name":"Conference Record of the Twenty Sixth IEEE Photovoltaic Specialists Conference - 1997","volume":"9 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131894006","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 : 1997-10-01DOI: 10.1109/PVSC.1997.654052
J. Gee, B. Sopori
Multicrystalline-silicon (mc-Si) materials and cells feature large areal variations in material and junction quality. The regions with poor device quality have been predicted to have more recombination current at forward bias than a simple area-weighted average due to the parallel interconnection of the good and bad regions by the front junction. The authors have examined the effect of gettering on areal inhomogeneities in large-area mc-Si cells. Cells with large areal inhomogeneities were found to have increased nonideal recombination current, which is in line with theoretical predictions. Phosphorus-diffusion and aluminum-alloy gettering of mc-Si was found to reduce the areal inhomogeneities and improve large-area mc-Si device performance.
{"title":"The effect of gettering on areal inhomogeneities in large-area multicrystalline-silicon solar cells","authors":"J. Gee, B. Sopori","doi":"10.1109/PVSC.1997.654052","DOIUrl":"https://doi.org/10.1109/PVSC.1997.654052","url":null,"abstract":"Multicrystalline-silicon (mc-Si) materials and cells feature large areal variations in material and junction quality. The regions with poor device quality have been predicted to have more recombination current at forward bias than a simple area-weighted average due to the parallel interconnection of the good and bad regions by the front junction. The authors have examined the effect of gettering on areal inhomogeneities in large-area mc-Si cells. Cells with large areal inhomogeneities were found to have increased nonideal recombination current, which is in line with theoretical predictions. Phosphorus-diffusion and aluminum-alloy gettering of mc-Si was found to reduce the areal inhomogeneities and improve large-area mc-Si device performance.","PeriodicalId":251166,"journal":{"name":"Conference Record of the Twenty Sixth IEEE Photovoltaic Specialists Conference - 1997","volume":"110 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132819975","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 : 1997-10-01DOI: 10.1109/PVSC.1997.653919
D. Ruby, P. Yang, M. Roy, S. Narayanan
We developed a self-aligned emitter etchback technique that requires only a single emitter diffusion and no alignments to form self-aligned, patterned-emitter profiles. Standard, commercial, screen-printed gridlines mask a plasma-etchback of the emitter. A subsequent PECVD-nitride deposition provides good surface and bulk passivation and an antireflection coating. We succeeded in finding a set of parameters which resulted in good emitter uniformity and improved cell performance. We used full-size multicrystalline silicon (mc-Si) cells processed in a commercial production line and performed a statistically designed, multiparameter experiment to optimize the use of a hydrogenation treatment to increase performance. Our initial results found a statistically significant improvement of half an absolute percentage point in cell efficiency when the self-aligned emitter etchback was combined with a 3-step PECVD-nitride surface passivation and hydrogenation treatment.
{"title":"Recent progress on the self-aligned, selective-emitter silicon solar cell","authors":"D. Ruby, P. Yang, M. Roy, S. Narayanan","doi":"10.1109/PVSC.1997.653919","DOIUrl":"https://doi.org/10.1109/PVSC.1997.653919","url":null,"abstract":"We developed a self-aligned emitter etchback technique that requires only a single emitter diffusion and no alignments to form self-aligned, patterned-emitter profiles. Standard, commercial, screen-printed gridlines mask a plasma-etchback of the emitter. A subsequent PECVD-nitride deposition provides good surface and bulk passivation and an antireflection coating. We succeeded in finding a set of parameters which resulted in good emitter uniformity and improved cell performance. We used full-size multicrystalline silicon (mc-Si) cells processed in a commercial production line and performed a statistically designed, multiparameter experiment to optimize the use of a hydrogenation treatment to increase performance. Our initial results found a statistically significant improvement of half an absolute percentage point in cell efficiency when the self-aligned emitter etchback was combined with a 3-step PECVD-nitride surface passivation and hydrogenation treatment.","PeriodicalId":251166,"journal":{"name":"Conference Record of the Twenty Sixth IEEE Photovoltaic Specialists Conference - 1997","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132631679","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 : 1997-10-01DOI: 10.1109/PVSC.1997.654273
R. Mitchell, C. Witt, H. Thomas, D. Ruby, R. King, C.C. Aldrich
The Photovoltaic Manufacturing Technology (PVMaT) project is helping the US photovoltaic (PV) industry extend its world leadership role in manufacturing and stimulate the commercial development of PV modules and systems. Initiated in 1990, PVMaT is being carried out in several directed and staggered phases to support industry's continued progress. Thirteen subcontracts awarded in FY 1996 under Phase 4A emphasize improvement and cost reduction in the manufacture of full-system PV products. Areas of work in Phase 4A included, but were not limited to, issues such as improving module-manufacturing processes; system and system-component packaging, integration, manufacturing and assembly; product manufacturing flexibility; and balance-of-system development with the goal of product manufacturing improvements. These Phase 4A, product-driven manufacturing research and development (R&D) activities are now completing their second phase. Progress under these Phase 4A and remaining Phase 2B subcontracts from the earlier PVMaT solicitation are summarized in this paper. Evaluations of the success of this project have been carried out in FY 1995 and late FY 1996. This paper examines the 1997 cost/capacity data that have been collected from active PVMaT manufacturers.
{"title":"Progress update on the US Photovoltaic Manufacturing Technology project","authors":"R. Mitchell, C. Witt, H. Thomas, D. Ruby, R. King, C.C. Aldrich","doi":"10.1109/PVSC.1997.654273","DOIUrl":"https://doi.org/10.1109/PVSC.1997.654273","url":null,"abstract":"The Photovoltaic Manufacturing Technology (PVMaT) project is helping the US photovoltaic (PV) industry extend its world leadership role in manufacturing and stimulate the commercial development of PV modules and systems. Initiated in 1990, PVMaT is being carried out in several directed and staggered phases to support industry's continued progress. Thirteen subcontracts awarded in FY 1996 under Phase 4A emphasize improvement and cost reduction in the manufacture of full-system PV products. Areas of work in Phase 4A included, but were not limited to, issues such as improving module-manufacturing processes; system and system-component packaging, integration, manufacturing and assembly; product manufacturing flexibility; and balance-of-system development with the goal of product manufacturing improvements. These Phase 4A, product-driven manufacturing research and development (R&D) activities are now completing their second phase. Progress under these Phase 4A and remaining Phase 2B subcontracts from the earlier PVMaT solicitation are summarized in this paper. Evaluations of the success of this project have been carried out in FY 1995 and late FY 1996. This paper examines the 1997 cost/capacity data that have been collected from active PVMaT manufacturers.","PeriodicalId":251166,"journal":{"name":"Conference Record of the Twenty Sixth IEEE Photovoltaic Specialists Conference - 1997","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114477708","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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