Yongting Yang, Kay Bischoff, Dominik Mücke, C. Esen, Ralf Hellmann
The authors report on ultraviolet ultrashort pulsed laser ablation of fused silica and compare the achievable micromachining results to those obtained by using the fundamental emission wavelength in infrared. Ablation in ultraviolet reveals a stable efficiency for increasing fluences, whereas using an infrared beam exhibits a decreasing trend of the ablation efficiency at higher and increasing fluences. In addition, a significant improvement in the surface quality is found by using an ultraviolet wavelength in a fluence range up to 20 J/cm2 compared to infrared, e.g., revealing an Ra of down to 0.45 μm on using the ultraviolet wavelength compared to Ra = 0.56 μm on using infrared at fluences up 15 J/cm2. Moreover, taking advantage of the high available pulse energy, the authors compare the achievable ablation efficiency and surface roughness using a conventionally focused ultraviolet beam and a defocused ultraviolet beam, finding that the defocused ultraviolet beam possesses a processing quality comparable to that of the focused beam. Finally, the authors exemplify the potential of ultraviolet ultrashort pulsed laser ablation by using a Tesla mixer for microfluidic integration of fused silica.
{"title":"UV-ultrashort pulsed laser ablation of fused silica","authors":"Yongting Yang, Kay Bischoff, Dominik Mücke, C. Esen, Ralf Hellmann","doi":"10.2351/7.0001197","DOIUrl":"https://doi.org/10.2351/7.0001197","url":null,"abstract":"The authors report on ultraviolet ultrashort pulsed laser ablation of fused silica and compare the achievable micromachining results to those obtained by using the fundamental emission wavelength in infrared. Ablation in ultraviolet reveals a stable efficiency for increasing fluences, whereas using an infrared beam exhibits a decreasing trend of the ablation efficiency at higher and increasing fluences. In addition, a significant improvement in the surface quality is found by using an ultraviolet wavelength in a fluence range up to 20 J/cm2 compared to infrared, e.g., revealing an Ra of down to 0.45 μm on using the ultraviolet wavelength compared to Ra = 0.56 μm on using infrared at fluences up 15 J/cm2. Moreover, taking advantage of the high available pulse energy, the authors compare the achievable ablation efficiency and surface roughness using a conventionally focused ultraviolet beam and a defocused ultraviolet beam, finding that the defocused ultraviolet beam possesses a processing quality comparable to that of the focused beam. Finally, the authors exemplify the potential of ultraviolet ultrashort pulsed laser ablation by using a Tesla mixer for microfluidic integration of fused silica.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":"32 16","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139442816","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}
Laser metal deposition (LMD) is a blown powder process used for the additive manufacturing of large and/or complex parts. The laser spot size is determined by the fiber optic cable and the imaging ratio of the process optics. Spot sizes typically used in LMD can range from 200 μm to several millimeters, whereby zoom optics can be employed to change the laser spot focus within seconds during the process. However, industrial powder nozzles are still static in terms of powder spot size. Changing the powder spot size in line with the laser spot size could ensure the favorable dual outcome of time savings when printing large volumes while also generating fine near-net-shape features. To help overcome the current limitations in the LMD process, this work examines an adaptive powder nozzle setup. In this discrete coaxial layout of three single lateral powder injectors, the individual powder injectors can be adjusted closer to or further from the process to, respectively, dilate or shrink the powder stream focus. Different inner diameters of powder injectors are hereby examined. The resulting powder propagation behavior is characterized for different setups of the single powder nozzles. Single beads are welded with different nozzle setups for fine and coarse powder spots, while the laser spot size is changed accordingly using zoom optics. The laser power is a closed-loop controlled by a two-color pyrometer to achieve comparative process temperatures. The single beads are evaluated with regard to their geometry. High-speed imaging provides supplementary information on weld bead generation.
{"title":"Adaptive powder nozzle setup for enhanced efficiency in laser metal deposition","authors":"A. Bohlen, T. Seefeld","doi":"10.2351/7.0001183","DOIUrl":"https://doi.org/10.2351/7.0001183","url":null,"abstract":"Laser metal deposition (LMD) is a blown powder process used for the additive manufacturing of large and/or complex parts. The laser spot size is determined by the fiber optic cable and the imaging ratio of the process optics. Spot sizes typically used in LMD can range from 200 μm to several millimeters, whereby zoom optics can be employed to change the laser spot focus within seconds during the process. However, industrial powder nozzles are still static in terms of powder spot size. Changing the powder spot size in line with the laser spot size could ensure the favorable dual outcome of time savings when printing large volumes while also generating fine near-net-shape features. To help overcome the current limitations in the LMD process, this work examines an adaptive powder nozzle setup. In this discrete coaxial layout of three single lateral powder injectors, the individual powder injectors can be adjusted closer to or further from the process to, respectively, dilate or shrink the powder stream focus. Different inner diameters of powder injectors are hereby examined. The resulting powder propagation behavior is characterized for different setups of the single powder nozzles. Single beads are welded with different nozzle setups for fine and coarse powder spots, while the laser spot size is changed accordingly using zoom optics. The laser power is a closed-loop controlled by a two-color pyrometer to achieve comparative process temperatures. The single beads are evaluated with regard to their geometry. High-speed imaging provides supplementary information on weld bead generation.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":"2 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139446829","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}
Gunjan Kulkarni, Yahya Bougdid, C. Sugrim, Ranganathan Kumar, Aravinda Kar
Laser doping of n-type 4H-silicon carbide (SiC) semiconductor substrates with boron (B) using a pulsed Nd:YAG laser (λ = 1064 nm) is reported. An aqueous boric acid solution was used as a boron precursor. A simple theoretical heat transfer model was employed to select the laser processing parameters, i.e., laser power and laser-substrate interaction time, and determine the appropriate temperature to dope 4H-SiC substrates. The selected processing parameters ensured that the temperature at the laser-substrate interaction zone was below the SiC peritectic temperature to prevent any crystalline phase transformations in SiC. Fourier-transform infrared spectrometry was conducted to determine the optical properties of both undoped and boron-doped 4H-SiC substrates within the mid-wave infrared (MWIR) wavelength range (3–5 μm). Boron atoms create an acceptor energy level at 0.29 eV above the valence band in the 4H-SiC bandgap, which corresponds to λ = 4.3 μm. Boron-doped 4H-SiC substrate exhibited reduced reflectance and increased absorptance for the MWIR range. An absorption peak at λ = 4.3 μm was detected for the doped substrate. This confirmed the creation of the acceptor energy level in the 4H-SiC bandgap and, thus, doping of 4H-SiC with boron. A notable decrease in the refractive index, i.e., from 2.87 to 2.52, after laser doping of n-type 4H-SiC with boron was achieved.
{"title":"Laser doping of n-type 4H-SiC with boron using solution precursor for mid-wave infrared optical properties","authors":"Gunjan Kulkarni, Yahya Bougdid, C. Sugrim, Ranganathan Kumar, Aravinda Kar","doi":"10.2351/7.0001186","DOIUrl":"https://doi.org/10.2351/7.0001186","url":null,"abstract":"Laser doping of n-type 4H-silicon carbide (SiC) semiconductor substrates with boron (B) using a pulsed Nd:YAG laser (λ = 1064 nm) is reported. An aqueous boric acid solution was used as a boron precursor. A simple theoretical heat transfer model was employed to select the laser processing parameters, i.e., laser power and laser-substrate interaction time, and determine the appropriate temperature to dope 4H-SiC substrates. The selected processing parameters ensured that the temperature at the laser-substrate interaction zone was below the SiC peritectic temperature to prevent any crystalline phase transformations in SiC. Fourier-transform infrared spectrometry was conducted to determine the optical properties of both undoped and boron-doped 4H-SiC substrates within the mid-wave infrared (MWIR) wavelength range (3–5 μm). Boron atoms create an acceptor energy level at 0.29 eV above the valence band in the 4H-SiC bandgap, which corresponds to λ = 4.3 μm. Boron-doped 4H-SiC substrate exhibited reduced reflectance and increased absorptance for the MWIR range. An absorption peak at λ = 4.3 μm was detected for the doped substrate. This confirmed the creation of the acceptor energy level in the 4H-SiC bandgap and, thus, doping of 4H-SiC with boron. A notable decrease in the refractive index, i.e., from 2.87 to 2.52, after laser doping of n-type 4H-SiC with boron was achieved.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":"51 46","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139447056","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}
Hannes Panzer, J. Diller, Fabian Ehrenfels, Jonathan Brandt, Michael F. Zäh
Conventional manufacturing technologies, such as milling or casting, are limited in terms of the manufacturable complexity of the parts to be produced. They are also restricted in terms of the local modifiability of the mechanical properties. Additive manufacturing, specifically the Powder Bed Fusion of Metals using a Laser Beam (PBF-LB/M), is a novel method, which is capable of addressing both limitations. However, the resulting parts are often prone to cracking during PBF-LB/M and in the service afterward because of high thermally induced local stress intensities. Selectively modifying the process parameters during the fabrication can be a suitable strategy to locally reduce the failure susceptibility. Over the course of this study, samples made from the nickel-based superalloy Inconel 718 were manufactured with varying laser powers, hatch distances, and scan speeds. The samples were divided into stress crack specimens as well as static and dynamic tensile test specimens. The grain structure was investigated, and correlations between the microstructure and the cracking susceptibility were determined. It was found out that variations in the laser power had the most pronounced effect on the grain structure and the failure behavior. An increasing grain size enhanced the fracture resistance in the stress crack samples while the static and dynamic mechanical properties deteriorated. Based on these results, the application area of PBF-LB/M could potentially be widened due to the manufacturability of parts otherwise susceptible to stress-induced cracking. The mechanical properties of as-built parts can remain unchanged utilizing a local process parameter adaption.
{"title":"Experimental investigation of process parameter variations on the microstructure and failure behavior of IN718 structures in PBF-LB/M","authors":"Hannes Panzer, J. Diller, Fabian Ehrenfels, Jonathan Brandt, Michael F. Zäh","doi":"10.2351/7.0001232","DOIUrl":"https://doi.org/10.2351/7.0001232","url":null,"abstract":"Conventional manufacturing technologies, such as milling or casting, are limited in terms of the manufacturable complexity of the parts to be produced. They are also restricted in terms of the local modifiability of the mechanical properties. Additive manufacturing, specifically the Powder Bed Fusion of Metals using a Laser Beam (PBF-LB/M), is a novel method, which is capable of addressing both limitations. However, the resulting parts are often prone to cracking during PBF-LB/M and in the service afterward because of high thermally induced local stress intensities. Selectively modifying the process parameters during the fabrication can be a suitable strategy to locally reduce the failure susceptibility. Over the course of this study, samples made from the nickel-based superalloy Inconel 718 were manufactured with varying laser powers, hatch distances, and scan speeds. The samples were divided into stress crack specimens as well as static and dynamic tensile test specimens. The grain structure was investigated, and correlations between the microstructure and the cracking susceptibility were determined. It was found out that variations in the laser power had the most pronounced effect on the grain structure and the failure behavior. An increasing grain size enhanced the fracture resistance in the stress crack samples while the static and dynamic mechanical properties deteriorated. Based on these results, the application area of PBF-LB/M could potentially be widened due to the manufacturability of parts otherwise susceptible to stress-induced cracking. The mechanical properties of as-built parts can remain unchanged utilizing a local process parameter adaption.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":"44 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139452507","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}
Yasmine Bouraoui, L. Rathmann, Claudia Niehaves, M. Mikulewitsch, A. Fischer, T. Radel
Laser chemical machining (LCM) is a method of laser processing based on gentle material removal by means of thermal induced chemical dissolution. Since LCM depends predominantly on the surface temperature of the workpiece, the process window is restricted by the appearance of gas bubbles at higher laser powers and their associated shielding effect. In order to extend the process understanding, the influence of the laser power modulation on the removal behavior is investigated in the present work. The experiments were conducted on titanium grade 1 and with phosphoric acid. Based on the response time in experiments with a single step function of the laser power, a spatial frequency threshold was determined above which a constant removal depth could be expected. Afterward, the laser power was modulated rectangularly in time, resulting in combination with the process velocity in different spatial modulation frequencies varying from 1 to 20 mm−1. The investigations showed that the removal cavity exhibited sinusoidal oscillation in depth along the machining direction with a spatial frequency corresponding to the spatial frequency of the laser power. When the spatial frequency exceeds the determined threshold frequency, the cavity depth is constant. This established the basis for generating complex removal profiles by varying the power in the range below the threshold frequency.
{"title":"Material removal in laser chemical processing with modulated laser power","authors":"Yasmine Bouraoui, L. Rathmann, Claudia Niehaves, M. Mikulewitsch, A. Fischer, T. Radel","doi":"10.2351/7.0001109","DOIUrl":"https://doi.org/10.2351/7.0001109","url":null,"abstract":"Laser chemical machining (LCM) is a method of laser processing based on gentle material removal by means of thermal induced chemical dissolution. Since LCM depends predominantly on the surface temperature of the workpiece, the process window is restricted by the appearance of gas bubbles at higher laser powers and their associated shielding effect. In order to extend the process understanding, the influence of the laser power modulation on the removal behavior is investigated in the present work. The experiments were conducted on titanium grade 1 and with phosphoric acid. Based on the response time in experiments with a single step function of the laser power, a spatial frequency threshold was determined above which a constant removal depth could be expected. Afterward, the laser power was modulated rectangularly in time, resulting in combination with the process velocity in different spatial modulation frequencies varying from 1 to 20 mm−1. The investigations showed that the removal cavity exhibited sinusoidal oscillation in depth along the machining direction with a spatial frequency corresponding to the spatial frequency of the laser power. When the spatial frequency exceeds the determined threshold frequency, the cavity depth is constant. This established the basis for generating complex removal profiles by varying the power in the range below the threshold frequency.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":"6 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139389879","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}
In the present work, laser-induced breakdown spectroscopy (LIBS) is used to examine the hazardous constituents present in the residues of six types of normal and six types of green firecracker samples. The residue of the normal firecracker’s samples contains the spectral lines of toxic chemicals such as Al, Ba, Sr, Mg, and Ti in a similar way as the fresh powder of normal crackers. The residues of the green firecracker’s samples contain toxic elements such as Al and Ba, and the intensities of these toxic elements are so high that these samples also contain the electronic bands of AlO and SrO. The UV-vis spectra of residues of normal and green firecracker samples contain the molecules of KNO3, CaO, Al2O3, and SrO in a similar way as the fresh powder of these firecrackers does. This reflects that the toxicity of the powder of firecracker samples remains similar after the burning of these firecrackers’ samples. Therefore, these toxic residues are mixed in the soil, where they burn and contaminate it. For the assessment of the contamination of the soil, the concentration of micronutrients such as Fe, Cu, Mn, Zn, and P is calculated using atomic absorption spectroscopy (AAS) techniques and found to increase in all the contaminated soil compared to blank soil. This reflects that the soil is contaminated. For the classification of the residues and soil contaminated with residues, the principal component analysis (PCA) and hierarchical clustering analysis (HCA) are applied to the LIBS data set.
本研究采用激光诱导击穿光谱法（LIBS）来检测六种普通爆竹和六种绿色爆竹样品残留物中的有害成分。普通爆竹样品残留物中含有 Al、Ba、Sr、Mg 和 Ti 等有毒化学物质的光谱线，与普通爆竹的新鲜粉末相似。绿色爆竹残留样品中含有 Al 和 Ba 等有毒元素，而且这些有毒元素的强度非常高，以至于这些样品还含有 AlO 和 SrO 的电子带。普通爆竹样品和绿色爆竹样品残留物的紫外可见光谱中含有 KNO3、CaO、Al2O3 和 SrO 分子，与这些爆竹的新鲜粉末相似。这反映出爆竹样品燃烧后，其粉末的毒性仍然相似。因此，这些有毒残留物混合在土壤中，燃烧后污染了土壤。为了评估土壤的污染情况，我们使用原子吸收光谱（AAS）技术计算了铁、铜、锰、锌和磷等微量营养元素的浓度，发现与空白土壤相比，所有受污染土壤中的微量营养元素浓度都有所增加。这反映出土壤受到了污染。为了对残留物和受残留物污染的土壤进行分类，对 LIBS 数据集采用了主成分分析 (PCA) 和分层聚类分析 (HCA)。
{"title":"Assessment of toxicity of residues of normal/green cracker and their impact on soil","authors":"Darpan Dubey, Awadhesh Kumar Rai","doi":"10.2351/7.0001266","DOIUrl":"https://doi.org/10.2351/7.0001266","url":null,"abstract":"In the present work, laser-induced breakdown spectroscopy (LIBS) is used to examine the hazardous constituents present in the residues of six types of normal and six types of green firecracker samples. The residue of the normal firecracker’s samples contains the spectral lines of toxic chemicals such as Al, Ba, Sr, Mg, and Ti in a similar way as the fresh powder of normal crackers. The residues of the green firecracker’s samples contain toxic elements such as Al and Ba, and the intensities of these toxic elements are so high that these samples also contain the electronic bands of AlO and SrO. The UV-vis spectra of residues of normal and green firecracker samples contain the molecules of KNO3, CaO, Al2O3, and SrO in a similar way as the fresh powder of these firecrackers does. This reflects that the toxicity of the powder of firecracker samples remains similar after the burning of these firecrackers’ samples. Therefore, these toxic residues are mixed in the soil, where they burn and contaminate it. For the assessment of the contamination of the soil, the concentration of micronutrients such as Fe, Cu, Mn, Zn, and P is calculated using atomic absorption spectroscopy (AAS) techniques and found to increase in all the contaminated soil compared to blank soil. This reflects that the soil is contaminated. For the classification of the residues and soil contaminated with residues, the principal component analysis (PCA) and hierarchical clustering analysis (HCA) are applied to the LIBS data set.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":"31 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139452076","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. Biester, A. Barroi, Nick Schwarz, J. Hermsdorf, S. Kaierle
Laser-assisted double wire welding with nontransferred arc uses an electric arc to melt two welding wires fed toward each other. The molten material drips onto the substrate, where it is joined to the substrate without undercuts by means of oscillated laser radiation. The process offers possibility of creating structures with high deposition rates (8.4 kg/h), but faces challenges in fulfilling the requirements for surface properties and geometric accuracy. One approach to meet the requirements is to confine the final seam geometry by applying the melt into a mold. Such a confinement can be a wall previously applied by a process with higher geometric accuracy. An investigation of this approach was carried out by studying the deposition of mild steel weld beads within two confining structures, in this case, a groove. A particular interest in the evaluation is connection of the weld bead to the base material in the corners, the bottom surface, and the side surface of the groove. In the first step, weld beads are deposited in 12 mm wide grooves in a mild steel substrate with variable laser beam oscillation amplitudes of 10–13 mm. In the second step, several layers are deposited with variable welding speeds. The oscillation amplitude that generates the best connection in the corners is 13 mm. Bonding on the bottom and side surfaces could be achieved with all parameter sets. When applying several layers, the best lateral connection in the groove was produced with a welding speed of 200 mm/min.
{"title":"Welding between confinements as a new approach for high deposition rate additive manufacturing with laser-assisted double wire welding with nontransferred arc","authors":"K. Biester, A. Barroi, Nick Schwarz, J. Hermsdorf, S. Kaierle","doi":"10.2351/7.0001114","DOIUrl":"https://doi.org/10.2351/7.0001114","url":null,"abstract":"Laser-assisted double wire welding with nontransferred arc uses an electric arc to melt two welding wires fed toward each other. The molten material drips onto the substrate, where it is joined to the substrate without undercuts by means of oscillated laser radiation. The process offers possibility of creating structures with high deposition rates (8.4 kg/h), but faces challenges in fulfilling the requirements for surface properties and geometric accuracy. One approach to meet the requirements is to confine the final seam geometry by applying the melt into a mold. Such a confinement can be a wall previously applied by a process with higher geometric accuracy. An investigation of this approach was carried out by studying the deposition of mild steel weld beads within two confining structures, in this case, a groove. A particular interest in the evaluation is connection of the weld bead to the base material in the corners, the bottom surface, and the side surface of the groove. In the first step, weld beads are deposited in 12 mm wide grooves in a mild steel substrate with variable laser beam oscillation amplitudes of 10–13 mm. In the second step, several layers are deposited with variable welding speeds. The oscillation amplitude that generates the best connection in the corners is 13 mm. Bonding on the bottom and side surfaces could be achieved with all parameter sets. When applying several layers, the best lateral connection in the groove was produced with a welding speed of 200 mm/min.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":"10 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139390759","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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