Abstract Understanding the effect of powder feedstock alterations during multicycle additive manufacturing on the quality of built components is crucial to meet the requirements on critical parts for aerospace engine applications. In this study, powder recycling of Alloy 718 during electron beam melting was studied to understand its influence on fracture behavior of Charpy impact test bars. High resolution scanning electron microscopy was employed for fracture surface analysis on test bars produced from virgin and recycled powder. For all investigated samples, an intergranular type of fracture, initiated by non-metallic phases and bonding defects, was typically observed in the regions close to or within the contour zone. The fracture mode in the bulk of the samples was mainly moderately ductile dimple fracture. The results show a clear correlation between powder degradation during multi-cycle powder reuse and the amount of damage relevant defects observed on the fracture surfaces. In particular, samples produced from recycled powder show a significant amount of aluminum-rich oxide defects, originating from aluminum-rich oxide particulates on the surface of the recycled powder.
{"title":"Effect of Powder Recycling on the Fracture Behavior of Electron Beam Melted Alloy 718","authors":"H. Gruber, P. Karimi, E. Hryha, L. Nyborg","doi":"10.1515/pmp-2018-0005","DOIUrl":"https://doi.org/10.1515/pmp-2018-0005","url":null,"abstract":"Abstract Understanding the effect of powder feedstock alterations during multicycle additive manufacturing on the quality of built components is crucial to meet the requirements on critical parts for aerospace engine applications. In this study, powder recycling of Alloy 718 during electron beam melting was studied to understand its influence on fracture behavior of Charpy impact test bars. High resolution scanning electron microscopy was employed for fracture surface analysis on test bars produced from virgin and recycled powder. For all investigated samples, an intergranular type of fracture, initiated by non-metallic phases and bonding defects, was typically observed in the regions close to or within the contour zone. The fracture mode in the bulk of the samples was mainly moderately ductile dimple fracture. The results show a clear correlation between powder degradation during multi-cycle powder reuse and the amount of damage relevant defects observed on the fracture surfaces. In particular, samples produced from recycled powder show a significant amount of aluminum-rich oxide defects, originating from aluminum-rich oxide particulates on the surface of the recycled powder.","PeriodicalId":52175,"journal":{"name":"Powder Metallurgy Progress","volume":"18 1","pages":"40 - 48"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1515/pmp-2018-0005","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44488104","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}
P. M. Kumar, G. Gergely, Dániel Koncz Horváth, Z. Gácsi
Abstract The Sn–Ag–Cu (SAC) solders with low Ag or Cu content have been identified as promising candidates to replace the traditional Sn–Pb solder. In this study, an extensive discussion was presented on two major area of mechanical properties and microstructural investigation of SAC305 and SAC405. In this chapter, we study the composition, mechanical properties of SAC solder alloys and microstructure were examined by optical microscope and SEM and mechanical properties such as tensile tests, hardness test and density test of the lead solder alloys were explored. SAC305 and SAC405 alloys with different Ag content and constant Cu content under investigation and compare the value of SAC305 and SAC405. From this investigation, it was reported that tensile strength is increased, with an increase of Ag content and hardness and density were also increases in the same manner.
{"title":"Investigating the Microstructural and Mechanical Properties of Pure Lead-Free Soldering Materials (SAC305 & SAC405)","authors":"P. M. Kumar, G. Gergely, Dániel Koncz Horváth, Z. Gácsi","doi":"10.1515/pmp-2018-0006","DOIUrl":"https://doi.org/10.1515/pmp-2018-0006","url":null,"abstract":"Abstract The Sn–Ag–Cu (SAC) solders with low Ag or Cu content have been identified as promising candidates to replace the traditional Sn–Pb solder. In this study, an extensive discussion was presented on two major area of mechanical properties and microstructural investigation of SAC305 and SAC405. In this chapter, we study the composition, mechanical properties of SAC solder alloys and microstructure were examined by optical microscope and SEM and mechanical properties such as tensile tests, hardness test and density test of the lead solder alloys were explored. SAC305 and SAC405 alloys with different Ag content and constant Cu content under investigation and compare the value of SAC305 and SAC405. From this investigation, it was reported that tensile strength is increased, with an increase of Ag content and hardness and density were also increases in the same manner.","PeriodicalId":52175,"journal":{"name":"Powder Metallurgy Progress","volume":"18 1","pages":"49 - 57"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47456543","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}
R. Shvab, M. V. Sundaram, H. Karlsson, D. Chasoglou, S. Berg, E. Hryha, L. Nyborg
Abstract Increasing the application area of powder metallurgy (PM) steels for manufacturing of high-performance structural components results in material saving, reduction in energy consumption, etc. In this study, feasibility of the manufacturing of valve bridge component for heavy duty engine utilizing lean alloyed powders and novel vacuum sintering approach, followed by low pressure carburizing, is studied. Three low alloyed steel powders were processed by conventional uniaxial pressing and sintering at 1120 and 1250°C in industrial vacuum furnace. The components were tested under high cycle fatigue testing, simulating real conditions of operation. Fatigue properties did not show significant dependence on the sintering temperature and were comparable to currently used reference cast material. Fracture surfaces of broken samples were analyzed to detect crack initiations and fracture mechanisms as well as quality of sintering. Results showed preferentially ductile failure, well developed sintering necks and clean pore surfaces, indicating good sintering. Tested material in combination with novel vacuum sintering process show to be an attractive alternative for manufacturing of this type of components for heavy duty engine applications.
{"title":"Manufacturing of Valve Bridge Component Utilizing Lean Alloyed Powders and Vacuum Sintering","authors":"R. Shvab, M. V. Sundaram, H. Karlsson, D. Chasoglou, S. Berg, E. Hryha, L. Nyborg","doi":"10.1515/pmp-2018-0004","DOIUrl":"https://doi.org/10.1515/pmp-2018-0004","url":null,"abstract":"Abstract Increasing the application area of powder metallurgy (PM) steels for manufacturing of high-performance structural components results in material saving, reduction in energy consumption, etc. In this study, feasibility of the manufacturing of valve bridge component for heavy duty engine utilizing lean alloyed powders and novel vacuum sintering approach, followed by low pressure carburizing, is studied. Three low alloyed steel powders were processed by conventional uniaxial pressing and sintering at 1120 and 1250°C in industrial vacuum furnace. The components were tested under high cycle fatigue testing, simulating real conditions of operation. Fatigue properties did not show significant dependence on the sintering temperature and were comparable to currently used reference cast material. Fracture surfaces of broken samples were analyzed to detect crack initiations and fracture mechanisms as well as quality of sintering. Results showed preferentially ductile failure, well developed sintering necks and clean pore surfaces, indicating good sintering. Tested material in combination with novel vacuum sintering process show to be an attractive alternative for manufacturing of this type of components for heavy duty engine applications.","PeriodicalId":52175,"journal":{"name":"Powder Metallurgy Progress","volume":"18 1","pages":"31 - 39"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44466916","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}
V. Vassileva, H. Danninger, S. Strobl, C. Gierl-Mayer, R. de Oro Calderon, H. Hutter
Abstract Boron has been known to activate densification during sintering of ferrous powder compacts, though with risk of embrittlement. In the present study, specimens Fe-B and Fe-C-B prepared from standard atomized iron powder with addition of ferroboron Fe-21%B were sintered in different atmospheres, and the resulting microstructures and properties were studied. It showed that the activating effect of boron is observed during sintering in argon and in hydrogen while sintering in N2 containing atmospheres results in rapid deactivation of boron, through formation of stable BN. In hydrogen atmosphere, surface deboronizing was observed to considerable depth. Ar is chemically inert, but Ar trapped inside closed pores tends to inhibit further densification. The impact energy data indicated that the embrittling effect of boron is enhanced significantly by presence of carbon. In the fracture surfaces, transgranular cleavage fracture can be observed both at very low and high impact energy values.
{"title":"The Role of the Atmosphere on Boron-Activated Sintering of Ferrous Powder Compacts","authors":"V. Vassileva, H. Danninger, S. Strobl, C. Gierl-Mayer, R. de Oro Calderon, H. Hutter","doi":"10.1515/pmp-2018-0002","DOIUrl":"https://doi.org/10.1515/pmp-2018-0002","url":null,"abstract":"Abstract Boron has been known to activate densification during sintering of ferrous powder compacts, though with risk of embrittlement. In the present study, specimens Fe-B and Fe-C-B prepared from standard atomized iron powder with addition of ferroboron Fe-21%B were sintered in different atmospheres, and the resulting microstructures and properties were studied. It showed that the activating effect of boron is observed during sintering in argon and in hydrogen while sintering in N2 containing atmospheres results in rapid deactivation of boron, through formation of stable BN. In hydrogen atmosphere, surface deboronizing was observed to considerable depth. Ar is chemically inert, but Ar trapped inside closed pores tends to inhibit further densification. The impact energy data indicated that the embrittling effect of boron is enhanced significantly by presence of carbon. In the fracture surfaces, transgranular cleavage fracture can be observed both at very low and high impact energy values.","PeriodicalId":52175,"journal":{"name":"Powder Metallurgy Progress","volume":"18 1","pages":"20 - 6"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45259920","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}
Ľ. Medvecký, R. Stulajterova, M. Giretová, J. Mincik, M. Vojtko, J. Balko, E. Petrovová
Abstract The aim was to investigate the enamel health benefits of a novel toothpaste with active tetracalcium phosphate/monetite mixtures under de/remineralization cycling. The enamel de/remineralization cycling protocol was consisted of demineralization in 1% aqueous solution of citric acid at pH 3.6 with following treatment with toothpastes and soaking in remineralization storage solution. Effectiveness of toothpastes to promote remineralization was evaluated by surface microhardness measurements, enamel erosion depth, analysis of surface roughness and fluorescent optical method. The novel tetracalcium phosphate/monetite toothpaste had the same remineralization potential as commercial calcium silicate/phosphate toothpaste and significantly higher than control storage solution group (p<0.05). Surface roughness was significantly lower after addition of fluorides to dentifrice (p<0.05). The enamel erosion depth was significantly reduced by applying toothpastes as compared to negative control (p<0.05) and did not differ from calcium silicate/phosphate toothpaste (p>0.66). The results showed that dentifrice formulations containing active tetracalcium phosphate/monetite mixture with or without fluoride addition had excellent enamel remineralization potential under de/remineralization cycling and successfully promote remineralization of enamel with daily using in the form of toothpaste.
{"title":"Enamel Remineralization Potential of Novel Dentifrice with Tetracalcium Phosphate/Monetite Powder Component","authors":"Ľ. Medvecký, R. Stulajterova, M. Giretová, J. Mincik, M. Vojtko, J. Balko, E. Petrovová","doi":"10.1515/pmp-2018-0007","DOIUrl":"https://doi.org/10.1515/pmp-2018-0007","url":null,"abstract":"Abstract The aim was to investigate the enamel health benefits of a novel toothpaste with active tetracalcium phosphate/monetite mixtures under de/remineralization cycling. The enamel de/remineralization cycling protocol was consisted of demineralization in 1% aqueous solution of citric acid at pH 3.6 with following treatment with toothpastes and soaking in remineralization storage solution. Effectiveness of toothpastes to promote remineralization was evaluated by surface microhardness measurements, enamel erosion depth, analysis of surface roughness and fluorescent optical method. The novel tetracalcium phosphate/monetite toothpaste had the same remineralization potential as commercial calcium silicate/phosphate toothpaste and significantly higher than control storage solution group (p<0.05). Surface roughness was significantly lower after addition of fluorides to dentifrice (p<0.05). The enamel erosion depth was significantly reduced by applying toothpastes as compared to negative control (p<0.05) and did not differ from calcium silicate/phosphate toothpaste (p>0.66). The results showed that dentifrice formulations containing active tetracalcium phosphate/monetite mixture with or without fluoride addition had excellent enamel remineralization potential under de/remineralization cycling and successfully promote remineralization of enamel with daily using in the form of toothpaste.","PeriodicalId":52175,"journal":{"name":"Powder Metallurgy Progress","volume":"18 1","pages":"58 - 69"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1515/pmp-2018-0007","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46826994","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}
Abstract The aim of the study was to evaluate the effect of chemical composition on the structure and mechanical properties of Mn-Ni-Mo and Ni-Mo-Cu PM steels. Pre-alloyed powder Astaloy 85Mo, diffusion alloyed powders Distaloy AQ and Distaloy AB produced by Höganäs, low carbon ferromanganese, carbonyl nickel powder T255 with three-dimensional filamentary structure and graphite CU-F have been used as the basic powders. Three mixtures with compositions of Fe-1%Mn-(0.5/1.75)%Ni-(0.5/0.85)%Mo-0.8%C and Fe-1.75%Ni-0.5%Mo-1.5%Cu-0.8%C were prepared in a Turbula mixer. Green compacts were single pressed in a steel die at 660 MPa according to PN-EN ISO 2740 standard. Sinterhardening was carried out at 1250°C in a mixture of 95% N2+5% H2 for 60 minutes. Mechanical tests (tensile, bend, hardness) and microstructural investigations were performed. Additionally, XRD and EDS analysis, fractographic investigations were carried out. The microstructures of steels investigated were mainly bainitic or bainitic-martensitic. Addition 1% Mn to Distaloy AQ based steel caused increase of tensile properties (YS from 422 to 489 MPa, UTS from 522 to 638 MPa, TRS from 901 to 1096 MPa) and decrease of plasticity (elongation from 3.65 to 2.84%).
{"title":"The Structure and Mechanical Properties of Ni-Mo PM Steels with Addition of Mn And Cu","authors":"E. Lichańska, P. Kulecki, K. Pańcikiewicz","doi":"10.1515/pmp-2017-0005","DOIUrl":"https://doi.org/10.1515/pmp-2017-0005","url":null,"abstract":"Abstract The aim of the study was to evaluate the effect of chemical composition on the structure and mechanical properties of Mn-Ni-Mo and Ni-Mo-Cu PM steels. Pre-alloyed powder Astaloy 85Mo, diffusion alloyed powders Distaloy AQ and Distaloy AB produced by Höganäs, low carbon ferromanganese, carbonyl nickel powder T255 with three-dimensional filamentary structure and graphite CU-F have been used as the basic powders. Three mixtures with compositions of Fe-1%Mn-(0.5/1.75)%Ni-(0.5/0.85)%Mo-0.8%C and Fe-1.75%Ni-0.5%Mo-1.5%Cu-0.8%C were prepared in a Turbula mixer. Green compacts were single pressed in a steel die at 660 MPa according to PN-EN ISO 2740 standard. Sinterhardening was carried out at 1250°C in a mixture of 95% N2+5% H2 for 60 minutes. Mechanical tests (tensile, bend, hardness) and microstructural investigations were performed. Additionally, XRD and EDS analysis, fractographic investigations were carried out. The microstructures of steels investigated were mainly bainitic or bainitic-martensitic. Addition 1% Mn to Distaloy AQ based steel caused increase of tensile properties (YS from 422 to 489 MPa, UTS from 522 to 638 MPa, TRS from 901 to 1096 MPa) and decrease of plasticity (elongation from 3.65 to 2.84%).","PeriodicalId":52175,"journal":{"name":"Powder Metallurgy Progress","volume":"17 1","pages":"37 - 46"},"PeriodicalIF":0.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47888170","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}
K. Sülleiová, B. Ballóková, M. Besterci,, T. Kvačkaj
Abstract The development of the nanostructure in commercial pure copper and the strength and ductility after severe plastic deformation (SPD) with the technology of equal channel angular pressing (ECAP) are analysed. Experimental results and analyses showed that both strength and ductility can be increased simultaneously by SPD. The final grain size decreased from the initial 50μm by SPD to 100-300 nm after 10 passes. An increase of the ductility together with an increase of strength caused by SPD are explained by a strong grain refinement and by a dynamic equilibrium of weakening and strengthening, and it is visible on the final static tensile test stress-strain charts.
{"title":"Mechanical Properties of Copper Processed by Equal Channel Angular Pressing","authors":"K. Sülleiová, B. Ballóková, M. Besterci,, T. Kvačkaj","doi":"10.1515/pmp-2017-0013","DOIUrl":"https://doi.org/10.1515/pmp-2017-0013","url":null,"abstract":"Abstract The development of the nanostructure in commercial pure copper and the strength and ductility after severe plastic deformation (SPD) with the technology of equal channel angular pressing (ECAP) are analysed. Experimental results and analyses showed that both strength and ductility can be increased simultaneously by SPD. The final grain size decreased from the initial 50μm by SPD to 100-300 nm after 10 passes. An increase of the ductility together with an increase of strength caused by SPD are explained by a strong grain refinement and by a dynamic equilibrium of weakening and strengthening, and it is visible on the final static tensile test stress-strain charts.","PeriodicalId":52175,"journal":{"name":"Powder Metallurgy Progress","volume":"17 1","pages":"124 - 129"},"PeriodicalIF":0.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47015706","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}
Abstract A new inert gas fusion method has been developed for determining oxygen and nitrogen in Al and Mg powders. The approach, the methods and some results are discussed. Dissociation of AlSi10Mg powder, 99.9 % Mg powder, Mg alloy powder and MgO p.a. are presented.
{"title":"Pecularities of Gas Analysis in Al and Mg Powders","authors":"P. Oslanec, M. Škrobian","doi":"10.1515/pmp-2017-0007","DOIUrl":"https://doi.org/10.1515/pmp-2017-0007","url":null,"abstract":"Abstract A new inert gas fusion method has been developed for determining oxygen and nitrogen in Al and Mg powders. The approach, the methods and some results are discussed. Dissociation of AlSi10Mg powder, 99.9 % Mg powder, Mg alloy powder and MgO p.a. are presented.","PeriodicalId":52175,"journal":{"name":"Powder Metallurgy Progress","volume":"17 1","pages":"65 - 71"},"PeriodicalIF":0.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48213411","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}
Abstract The article deals with the effect of porosity on the contact fatigue of sintered material type Astaloy CrL with 0.3 and 0.4% C. Sets of samples were used with densities beginning from the value of 7000 kg.m−3 to the value of almost 7859 kg.m−3 which represents almost zero porosity (compact material). It has been found out that the increase of compacting pressure applied simultaneously with temperature results in the reduction of porosity from the value of 9.10% to 0.0005% and increase in hardness from 145 to 193 HV10, depending on the carbon content. Logically there is also an increase in the fatigue life by the contact fatigue tests for the value of 50×106 cycles from the value of 900 MPa to 1150 MPa for samples with 0.3% of C and from 900 MPa to 1300 MPa for samples with 0.4% C. These investigations were also carried out in the past, but to achieve the reduction of porosity, different technonologies were used at each level such as double pressing, hot pressing, saturation, hot forging, etc. In this case, the single technology of “spark plasma sintering” making use of compacting at high temperatures is capable to continuously reduce porosity to zero.
{"title":"Applying “Spark Plasma Sintering” Technology to Enhance the Resistance to Contact Fatigue of Sintered Steel Based on Astaloy CRL","authors":"D. Rodziňák, J. Čerňan, V. Puchý","doi":"10.1515/pmp-2017-0003","DOIUrl":"https://doi.org/10.1515/pmp-2017-0003","url":null,"abstract":"Abstract The article deals with the effect of porosity on the contact fatigue of sintered material type Astaloy CrL with 0.3 and 0.4% C. Sets of samples were used with densities beginning from the value of 7000 kg.m−3 to the value of almost 7859 kg.m−3 which represents almost zero porosity (compact material). It has been found out that the increase of compacting pressure applied simultaneously with temperature results in the reduction of porosity from the value of 9.10% to 0.0005% and increase in hardness from 145 to 193 HV10, depending on the carbon content. Logically there is also an increase in the fatigue life by the contact fatigue tests for the value of 50×106 cycles from the value of 900 MPa to 1150 MPa for samples with 0.3% of C and from 900 MPa to 1300 MPa for samples with 0.4% C. These investigations were also carried out in the past, but to achieve the reduction of porosity, different technonologies were used at each level such as double pressing, hot pressing, saturation, hot forging, etc. In this case, the single technology of “spark plasma sintering” making use of compacting at high temperatures is capable to continuously reduce porosity to zero.","PeriodicalId":52175,"journal":{"name":"Powder Metallurgy Progress","volume":"17 1","pages":"21 - 28"},"PeriodicalIF":0.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43376425","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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