Pub Date : 2014-01-01DOI: 10.1007/978-3-319-06145-0_1
Y. Komizo, Xinfang Zhang, H. Terasaki
{"title":"Hybrid System for In Situ Observation of Microstructure Evolution in Steel Materials","authors":"Y. Komizo, Xinfang Zhang, H. Terasaki","doi":"10.1007/978-3-319-06145-0_1","DOIUrl":"https://doi.org/10.1007/978-3-319-06145-0_1","url":null,"abstract":"","PeriodicalId":23197,"journal":{"name":"Transactions of JWRI","volume":"47 1","pages":"1-27"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81022216","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}
Drilling is widely applied in materials processing. Novel drilling methods, including electrical discharge machining, laser drilling, and plasma arc drilling, have emerged in recent years to overcome such problems as tool wear and low efficiency in the drilling of thick plates or difficult-to-machine materials. Plasma arc drilling is an effective and high-speed drilling method for thick plates. However, the mechanisms of plasma arc drilling, such as the hole formation and dross formation processes, have not yet been fully elucidated. In this study, a number of experiments under different drilling conditions were conducted to investigate the hole formation process in mild steel plate of 12 mm in thickness, using a high-speed video camera. Hole formation in plasma arc drilling is a highly complex process since both melting and vaporization are involved. The mechanisms of molten metal ejection as a material removal process were verified. The formation and removal of dross at the entrance and exit sides were elucidated by our observations of molten metal ejection. Further experiments were carried out to investigate the effect of the anode motion peculiar to plasma arc drilling. The results clarified the hole formation process and some specific related phenomena. The insights gained into the hole formation process will be useful in improving hole quality and reducing dross around the hole.
{"title":"Observation of hole formation process in plasma arc drilling","authors":"K. Kusumoto, S. Hao, S. Ishikawa","doi":"10.2207/QJJWS.29.66S","DOIUrl":"https://doi.org/10.2207/QJJWS.29.66S","url":null,"abstract":"Drilling is widely applied in materials processing. Novel drilling methods, including electrical discharge machining, laser drilling, and plasma arc drilling, have emerged in recent years to overcome such problems as tool wear and low efficiency in the drilling of thick plates or difficult-to-machine materials. Plasma arc drilling is an effective and high-speed drilling method for thick plates. However, the mechanisms of plasma arc drilling, such as the hole formation and dross formation processes, have not yet been fully elucidated. In this study, a number of experiments under different drilling conditions were conducted to investigate the hole formation process in mild steel plate of 12 mm in thickness, using a high-speed video camera. Hole formation in plasma arc drilling is a highly complex process since both melting and vaporization are involved. The mechanisms of molten metal ejection as a material removal process were verified. The formation and removal of dross at the entrance and exit sides were elucidated by our observations of molten metal ejection. Further experiments were carried out to investigate the effect of the anode motion peculiar to plasma arc drilling. The results clarified the hole formation process and some specific related phenomena. The insights gained into the hole formation process will be useful in improving hole quality and reducing dross around the hole.","PeriodicalId":23197,"journal":{"name":"Transactions of JWRI","volume":"134 1","pages":"253-255"},"PeriodicalIF":0.0,"publicationDate":"2010-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86308666","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}
T. Naoi, H. Nishikawa, T. Takemoto, H. Abe, M. Fukuhara, A. Inoue
To extend the engineering applications of bulk metallic glasses (BMGs), it is necessary to create process to form appropriate BMG/BMG and BMG/crystalline metal joint. In this study, hydrofluoric acid (HF) solution treatment and a laser soldering process were employed to enhance the solderability of Cu60Zr30Ti10 BMG. The surface treatment in HF solution successfully dissolved surface Zr and Ti, resulting in concentration of Cu at the surface. A reflow soldering process using Sn-3.0 mass% Ag-0.5 mass% Cu (SAC) solder on this surface showed obvious dewetting because the thin Cu-rich layer dissolved into the molten solder. Laser soldering with a 0.01 s irradiation time, which produces rapid heating and cooling rates, offered good wettability of SAC solder and Sn-57 mass% Bi (SB) solder. At the interface between the SB solder and the HF-treated BMG foil, an intermetallic compound (IMC) layer was observed by scanning electron microscopy (SEM).
为了扩大大块金属玻璃的工程应用，有必要创造形成合适的大块金属玻璃/大块金属玻璃和大块金属玻璃/晶体金属玻璃接头的工艺。采用氢氟酸(HF)固溶处理和激光焊接工艺提高Cu60Zr30Ti10 BMG的可焊性。在HF溶液中进行表面处理，成功地溶解了表面Zr和Ti，导致表面Cu浓度升高。采用Sn-3.0质量% Ag-0.5质量% Cu (SAC)焊料在该表面进行回流焊，由于薄的富Cu层溶解在焊料中，导致明显的脱湿。激光焊接时，辐照时间为0.01 s，加热和冷却速度快，SAC焊料和Sn-57质量% Bi (SB)焊料的润湿性好。扫描电镜(SEM)观察到，在SB焊料与经hf处理的BMG箔的界面处，存在一层金属间化合物(IMC)层。
{"title":"Enhancement of solderability of Cu60Zr30Ti10 bulk metallic glass by dealloying in hydrofluoric acid solution","authors":"T. Naoi, H. Nishikawa, T. Takemoto, H. Abe, M. Fukuhara, A. Inoue","doi":"10.2207/QJJWS.29.147S","DOIUrl":"https://doi.org/10.2207/QJJWS.29.147S","url":null,"abstract":"To extend the engineering applications of bulk metallic glasses (BMGs), it is necessary to create process to form appropriate BMG/BMG and BMG/crystalline metal joint. In this study, hydrofluoric acid (HF) solution treatment and a laser soldering process were employed to enhance the solderability of Cu60Zr30Ti10 BMG. The surface treatment in HF solution successfully dissolved surface Zr and Ti, resulting in concentration of Cu at the surface. A reflow soldering process using Sn-3.0 mass% Ag-0.5 mass% Cu (SAC) solder on this surface showed obvious dewetting because the thin Cu-rich layer dissolved into the molten solder. Laser soldering with a 0.01 s irradiation time, which produces rapid heating and cooling rates, offered good wettability of SAC solder and Sn-57 mass% Bi (SB) solder. At the interface between the SB solder and the HF-treated BMG foil, an intermetallic compound (IMC) layer was observed by scanning electron microscopy (SEM).","PeriodicalId":23197,"journal":{"name":"Transactions of JWRI","volume":"1 1","pages":"293-295"},"PeriodicalIF":0.0,"publicationDate":"2010-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91208952","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}
S. Koyama, I. Oya, Toshihiro Isaka, I. Shohji, M. Nishimuro, K. Hiramoto, Hironaga Miyamoto
Equipment for evaluating the wettability of solder paste has been developed using a laser displacement method. Using the equipment, the descent behavior of an electronic part in reflow soldering can be measured with a laser displacement meter. From the measured height displacement curve, the wetting time and spread rate of the solder paste onto the electrodes of an electronic part and a substrate can be investigated. The developed equipment can detect the difference in the wettability of solder paste which depends on the solder paste type, the electrode type, and the degradation of the solder paste over time.
{"title":"Development of wettability evaluation equipment for solder paste using laser displacement method","authors":"S. Koyama, I. Oya, Toshihiro Isaka, I. Shohji, M. Nishimuro, K. Hiramoto, Hironaga Miyamoto","doi":"10.5104/JIEP.14.390","DOIUrl":"https://doi.org/10.5104/JIEP.14.390","url":null,"abstract":"Equipment for evaluating the wettability of solder paste has been developed using a laser displacement method. Using the equipment, the descent behavior of an electronic part in reflow soldering can be measured with a laser displacement meter. From the measured height displacement curve, the wetting time and spread rate of the solder paste onto the electrodes of an electronic part and a substrate can be investigated. The developed equipment can detect the difference in the wettability of solder paste which depends on the solder paste type, the electrode type, and the degradation of the solder paste over time.","PeriodicalId":23197,"journal":{"name":"Transactions of JWRI","volume":"4 1","pages":"169-171"},"PeriodicalIF":0.0,"publicationDate":"2010-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80982135","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 : 2010-12-01DOI: 10.2355/TETSUTOHAGANE.96.691
Shuoyuan Zhang, H. Terasaki, Y. Komizo
Martensite transformation of supermartensitic stainless steel during cooling was in-situ observed by using high temperature laser scanning confocal microscopy and X-ray diffraction by Synchrotron radiation. The crystallography of martensite and austenite structure were analyzed which X-ray diffraction spots and electron back scattered diffraction patterns (EBSD). From the test results it could be concluded that the austenite phase is accommodated by rotation less that 3 degree of the crystallite when the martensite transformation is occurred. X-Ray diffraction integration strength of austenite was influenced by the transformation stress immediately after the martensite transformation. We consider that the diffracting power of parent phase of austenite increase during martensitie transformation, because the compression stress is accommodated, and the defect is introduced, resulting in the mosaic structure.
{"title":"In-situ Observation of martensite transformation and retained austenite in supermartensitic stainless steel","authors":"Shuoyuan Zhang, H. Terasaki, Y. Komizo","doi":"10.2355/TETSUTOHAGANE.96.691","DOIUrl":"https://doi.org/10.2355/TETSUTOHAGANE.96.691","url":null,"abstract":"Martensite transformation of supermartensitic stainless steel during cooling was in-situ observed by using high temperature laser scanning confocal microscopy and X-ray diffraction by Synchrotron radiation. The crystallography of martensite and austenite structure were analyzed which X-ray diffraction spots and electron back scattered diffraction patterns (EBSD). From the test results it could be concluded that the austenite phase is accommodated by rotation less that 3 degree of the crystallite when the martensite transformation is occurred. X-Ray diffraction integration strength of austenite was influenced by the transformation stress immediately after the martensite transformation. We consider that the diffracting power of parent phase of austenite increase during martensitie transformation, because the compression stress is accommodated, and the defect is introduced, resulting in the mosaic structure.","PeriodicalId":23197,"journal":{"name":"Transactions of JWRI","volume":"8 1","pages":"115-117"},"PeriodicalIF":0.0,"publicationDate":"2010-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78755181","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}
S. Yamane, T. Yamazaki, Tomoaki Kaneta, Toru Nakajima, H. Yamamoto
{"title":"Experiment and numerical simulation in temperature distribution and welding distortion in GMA welding","authors":"S. Yamane, T. Yamazaki, Tomoaki Kaneta, Toru Nakajima, H. Yamamoto","doi":"10.2207/QJJWS.29.31S","DOIUrl":"https://doi.org/10.2207/QJJWS.29.31S","url":null,"abstract":"","PeriodicalId":23197,"journal":{"name":"Transactions of JWRI","volume":"50 11","pages":"190-192"},"PeriodicalIF":0.0,"publicationDate":"2010-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72547679","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}
Tasuku Zeniya, S. Tashiro, Manabu Tanaka, E. Yamamoto, K. Yamazaki, Keiichi Suzuki
Generally, ThO2 or La2O3 are added to a tungsten cathode for prompting electron emission from the cathode and preventing the cathode from consumption. In this study, influence of adding 2%ThO to the tungsten cathode as emitter material on arc properties and weld pool formation mechanism in TIG welding was investigated by employing numerical simulation model considering heat and mass transfers among the cathode, the arc and the weld pool. As a result, it was found that although the maximum cathode jet velocity in case of 2%ThO2-W cathode was 497 m/s, that in case of pure W cathode was only 156 m/s because of low current density caused by flatten surface of the melting cathode tip. In case of 2%ThO2-W cathode, the depth and the width of the weld pool became shallow wide than those in case of pure W cathode. For a reason, it is considered that because shearing force from the arc to the weld pool was larger than that of pure W cathode due to higher cathode jet velocity, the heat transport in the weld pool near the surface in radial outward direction increased
{"title":"Numerical analysis of weld pool formation mechanism in TIG welding in consideration of the influence of emitter material adding to the tungsten cathode","authors":"Tasuku Zeniya, S. Tashiro, Manabu Tanaka, E. Yamamoto, K. Yamazaki, Keiichi Suzuki","doi":"10.2207/QJJWS.29.14S","DOIUrl":"https://doi.org/10.2207/QJJWS.29.14S","url":null,"abstract":"Generally, ThO2 or La2O3 are added to a tungsten cathode for prompting electron emission from the cathode and preventing the cathode from consumption. In this study, influence of adding 2%ThO to the tungsten cathode as emitter material on arc properties and weld pool formation mechanism in TIG welding was investigated by employing numerical simulation model considering heat and mass transfers among the cathode, the arc and the weld pool. As a result, it was found that although the maximum cathode jet velocity in case of 2%ThO2-W cathode was 497 m/s, that in case of pure W cathode was only 156 m/s because of low current density caused by flatten surface of the melting cathode tip. In case of 2%ThO2-W cathode, the depth and the width of the weld pool became shallow wide than those in case of pure W cathode. For a reason, it is considered that because shearing force from the arc to the weld pool was larger than that of pure W cathode due to higher cathode jet velocity, the heat transport in the weld pool near the surface in radial outward direction increased","PeriodicalId":23197,"journal":{"name":"Transactions of JWRI","volume":"41 1","pages":"184-186"},"PeriodicalIF":0.0,"publicationDate":"2010-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80059093","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}
Since it is indispensable to remove oxide layer on aluminum for realizing high quality weld joint in arc welding of aluminum plates, AC TIG welding is generally employed. In periods of EP (Electrode Positive) of AC TIG welding, the oxide layer is removed by cleaning action of cathode spots. In this paper, results on experimental observations of the cleaning action of the oxide layer by cathode spots in AC TIG welding of the aluminum plate with a high speed video camera will be reported. As a result, it was found that cathode spots moved slowly on the oxide layer and their averaged velocity was 26.1m/s. On the other hand, cathode spots near the center of the weld pool, where the oxide layer had been mostly removed, moved at high speed and their averaged velocity reached 121.9 m/s. Furthermore, the velocity greatly changed depending on the position of the cathode spot and exceeded 1 km/s at the maximum.
{"title":"Experimental observation of cleaning action of cathode spots in AC TIG welding of aluminum plates","authors":"S. Tashiro, H. Sawato, Manabu Tanaka","doi":"10.2207/QJJWS.29.5S","DOIUrl":"https://doi.org/10.2207/QJJWS.29.5S","url":null,"abstract":"Since it is indispensable to remove oxide layer on aluminum for realizing high quality weld joint in arc welding of aluminum plates, AC TIG welding is generally employed. In periods of EP (Electrode Positive) of AC TIG welding, the oxide layer is removed by cleaning action of cathode spots. In this paper, results on experimental observations of the cleaning action of the oxide layer by cathode spots in AC TIG welding of the aluminum plate with a high speed video camera will be reported. As a result, it was found that cathode spots moved slowly on the oxide layer and their averaged velocity was 26.1m/s. On the other hand, cathode spots near the center of the weld pool, where the oxide layer had been mostly removed, moved at high speed and their averaged velocity reached 121.9 m/s. Furthermore, the velocity greatly changed depending on the position of the cathode spot and exceeded 1 km/s at the maximum.","PeriodicalId":23197,"journal":{"name":"Transactions of JWRI","volume":"205 1","pages":"180-181"},"PeriodicalIF":0.0,"publicationDate":"2010-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74464469","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}
S. Horie, K. Shinozaki, Motomichi Yamamoto, K. Kadoi, Hiroki Nakashin, T. North
In this study, the theoretical tool design was proposed based on the material flow during friction stir spot welding (FSSW). At first, the fracture mode in a cross tensile test and a tensile shear test was investigated in detail. Then, the ideal profile of the welded joint was proposed to accomplish the high joint strength. The high joint strength can be acquired when the tip of the partially bonded interface is located at distance from the periphery of the keyhole and the surface of the top sheet. Based on the material flow model, it became clear that the strong inwards flow produced by the shoulder or the increase of the heat input to soften material around the stir zone leaded to producing the ideal joint. Thus four types of tools with different shoulder profiles were investigated. The investigation of the material flow and tensile tests were carried out. 15mm-spiral tool, which was designed to facilitate the material flow beneath the shoulder efficiently, attained the high joint strength in both a cross tensile and a tensile shear test.
{"title":"Effects of tool geometry and process conditions on material flow and strength of friction stir spot welded joints","authors":"S. Horie, K. Shinozaki, Motomichi Yamamoto, K. Kadoi, Hiroki Nakashin, T. North","doi":"10.2207/QJJWS.29.119S","DOIUrl":"https://doi.org/10.2207/QJJWS.29.119S","url":null,"abstract":"In this study, the theoretical tool design was proposed based on the material flow during friction stir spot welding (FSSW). At first, the fracture mode in a cross tensile test and a tensile shear test was investigated in detail. Then, the ideal profile of the welded joint was proposed to accomplish the high joint strength. The high joint strength can be acquired when the tip of the partially bonded interface is located at distance from the periphery of the keyhole and the surface of the top sheet. Based on the material flow model, it became clear that the strong inwards flow produced by the shoulder or the increase of the heat input to soften material around the stir zone leaded to producing the ideal joint. Thus four types of tools with different shoulder profiles were investigated. The investigation of the material flow and tensile tests were carried out. 15mm-spiral tool, which was designed to facilitate the material flow beneath the shoulder efficiently, attained the high joint strength in both a cross tensile and a tensile shear test.","PeriodicalId":23197,"journal":{"name":"Transactions of JWRI","volume":"12 1","pages":"28-30"},"PeriodicalIF":0.0,"publicationDate":"2010-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81700363","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}
The heat source properties of TIG arc strongly depend on composition of shielding gas. For example, since the arc column is constricted due to low electrical conductivity of the helium arc, heat flux onto a base metal in case of helium TIG arc is higher than that of argon TIG arc. The heat source properties can be controlled also by current waveform. Pulsed TIG welding is suitable for back-bead welding and thin plate welding, because the heat flux onto the base metal can be controlled by adjusting peak / base current ratio and frequency. A number of results on experimental and theoretical investigations of the heat source properties of DC TIG arc have been reported. However, those of pulsed TIG arc are still not fully understood because of the complexity of the phenomenon. In this paper, numerical simulation result of the heat source properties of pulsed TIG arc for various shielding gas composition will be reported. As a result, it was found that the heat flux increased immediately after transition from base current to peak current because of the thermal pinch effect. Furthermore, temperature distribution of helium arc changes following change in current immediately due to high thermal conductivity
{"title":"Numerical simulation of heat source properties of pulsed tungsten inert gas arc","authors":"Kuniyoshi Ito, S. Tashiro, Manabu Tanaka","doi":"10.2207/QJJWS.29.9S","DOIUrl":"https://doi.org/10.2207/QJJWS.29.9S","url":null,"abstract":"The heat source properties of TIG arc strongly depend on composition of shielding gas. For example, since the arc column is constricted due to low electrical conductivity of the helium arc, heat flux onto a base metal in case of helium TIG arc is higher than that of argon TIG arc. The heat source properties can be controlled also by current waveform. Pulsed TIG welding is suitable for back-bead welding and thin plate welding, because the heat flux onto the base metal can be controlled by adjusting peak / base current ratio and frequency. A number of results on experimental and theoretical investigations of the heat source properties of DC TIG arc have been reported. However, those of pulsed TIG arc are still not fully understood because of the complexity of the phenomenon. In this paper, numerical simulation result of the heat source properties of pulsed TIG arc for various shielding gas composition will be reported. As a result, it was found that the heat flux increased immediately after transition from base current to peak current because of the thermal pinch effect. Furthermore, temperature distribution of helium arc changes following change in current immediately due to high thermal conductivity","PeriodicalId":23197,"journal":{"name":"Transactions of JWRI","volume":"10 1","pages":"182-183"},"PeriodicalIF":0.0,"publicationDate":"2010-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79443925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：