Abstract The famous informed isotropic (IISO) viscosity successfully dominates the broader core structure of fiber orientation distributions for injection-molded long fiber composites, due to the flow-fiber coupling effect of stretching deformation. Recently, the GNF-X (Generalized Newtonian Fluid eXtended) constitutive equation of weighted shear/extensional viscosity has been shown to possess the potential to demonstrate the extension-induced corner vortex in the entry flow of a polymer melt. Using GNF-X, three-dimensional injection-molding flow simulations of a center-gated disk are, therefore, performed for verifying the effect of extensional viscosity on the core structure of fiber orientation, namely, the extension-induced fiber orientation. The equivalent of GNF-X and IISO is demonstrated for predicting fiber orientation distribution, while their primary parameter relationship is particularly found herein. It is significant to visualize dramatic patterns of extensional rate occurring in the center-gated disk simulation.
{"title":"The effect of extensional viscosity on the core structure of fiber orientation for injection-molded fiber composites","authors":"H. Tseng","doi":"10.1515/ipp-2023-4368","DOIUrl":"https://doi.org/10.1515/ipp-2023-4368","url":null,"abstract":"Abstract The famous informed isotropic (IISO) viscosity successfully dominates the broader core structure of fiber orientation distributions for injection-molded long fiber composites, due to the flow-fiber coupling effect of stretching deformation. Recently, the GNF-X (Generalized Newtonian Fluid eXtended) constitutive equation of weighted shear/extensional viscosity has been shown to possess the potential to demonstrate the extension-induced corner vortex in the entry flow of a polymer melt. Using GNF-X, three-dimensional injection-molding flow simulations of a center-gated disk are, therefore, performed for verifying the effect of extensional viscosity on the core structure of fiber orientation, namely, the extension-induced fiber orientation. The equivalent of GNF-X and IISO is demonstrated for predicting fiber orientation distribution, while their primary parameter relationship is particularly found herein. It is significant to visualize dramatic patterns of extensional rate occurring in the center-gated disk simulation.","PeriodicalId":14410,"journal":{"name":"International Polymer Processing","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2023-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48492170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The extrusion of large or heavy technical rubber profiles is usually assisted by a conveying device. Such a device can be a conveyor belt or a series of rollers, and its use is necessary mainly for being able to achieve the process. Within the context of numerical simulation of extrusion flows, a conveying device brings additional downstream constraints to the flow governing equations. In the present paper, we propose a simple engineering approach for modelling a roller conveyor used in rubber tire tread extrusion, and we apply it to the extrusion simulation of a flat tire tread profile as typically encountered in the tire manufacturing industry.
{"title":"Modelling of roller conveyor for the simulation of rubber tire tread extrusion","authors":"B. Debbaut","doi":"10.1515/ipp-2023-4356","DOIUrl":"https://doi.org/10.1515/ipp-2023-4356","url":null,"abstract":"Abstract The extrusion of large or heavy technical rubber profiles is usually assisted by a conveying device. Such a device can be a conveyor belt or a series of rollers, and its use is necessary mainly for being able to achieve the process. Within the context of numerical simulation of extrusion flows, a conveying device brings additional downstream constraints to the flow governing equations. In the present paper, we propose a simple engineering approach for modelling a roller conveyor used in rubber tire tread extrusion, and we apply it to the extrusion simulation of a flat tire tread profile as typically encountered in the tire manufacturing industry.","PeriodicalId":14410,"journal":{"name":"International Polymer Processing","volume":"38 1","pages":"387 - 394"},"PeriodicalIF":1.3,"publicationDate":"2023-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45877185","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zheng Tian, Yilu Zhang, N. Xu, Lisha Pan, Yuhong Feng
Abstract Poly(propylene carbonate) (PPC)/polypropylene (PP) spunbond nonwoven slice has gained more attention, owing to its excellent properties, such as biodegradability, flexibility, biocompatibility, and CO2 utilization. However, the applications of this green material are limited due to the poor thermodynamic incompatibility between PPC and PP. In this paper, PP grafted with maleic anhydride (MAH) and styrene (St) (PP-g-(MAH-co-St)), prepared by a mechanochemical method and having a grafting percentage GMAH = 1.40 %, was used as a compatibilizer to prepare a biodegradable PPC/compatibilizer/PP composite-spunbond nonwoven slice by melt-blending. The effects of compatibilizer content on the tensile strength, elongation at break, melt flow rate, thermal properties, and micro-morphology of PPC/PP-g-(MAH-co-St)/PP were systematically studied. Furthermore, the mechanism of compatibilization of PP-g-(MAH-co-St) in the PPC/PP spunbond nonwoven composite slice is discussed. The results indicated that this green PP-g-(MAH-co-St) exhibited a clear reactive compatibilization effect. Therefore, it can be considered as a good compatibilizer for the biodegradable PPC/PP spunbond nonwoven slice.
{"title":"Reactive compatibilization of polypropylene grafted with maleic anhydride and styrene, prepared by a mechanochemical method, for a blend system of biodegradable poly(propylene carbonate)/polypropylene spunbond nonwoven slice","authors":"Zheng Tian, Yilu Zhang, N. Xu, Lisha Pan, Yuhong Feng","doi":"10.1515/ipp-2023-4345","DOIUrl":"https://doi.org/10.1515/ipp-2023-4345","url":null,"abstract":"Abstract Poly(propylene carbonate) (PPC)/polypropylene (PP) spunbond nonwoven slice has gained more attention, owing to its excellent properties, such as biodegradability, flexibility, biocompatibility, and CO2 utilization. However, the applications of this green material are limited due to the poor thermodynamic incompatibility between PPC and PP. In this paper, PP grafted with maleic anhydride (MAH) and styrene (St) (PP-g-(MAH-co-St)), prepared by a mechanochemical method and having a grafting percentage GMAH = 1.40 %, was used as a compatibilizer to prepare a biodegradable PPC/compatibilizer/PP composite-spunbond nonwoven slice by melt-blending. The effects of compatibilizer content on the tensile strength, elongation at break, melt flow rate, thermal properties, and micro-morphology of PPC/PP-g-(MAH-co-St)/PP were systematically studied. Furthermore, the mechanism of compatibilization of PP-g-(MAH-co-St) in the PPC/PP spunbond nonwoven composite slice is discussed. The results indicated that this green PP-g-(MAH-co-St) exhibited a clear reactive compatibilization effect. Therefore, it can be considered as a good compatibilizer for the biodegradable PPC/PP spunbond nonwoven slice.","PeriodicalId":14410,"journal":{"name":"International Polymer Processing","volume":"38 1","pages":"395 - 403"},"PeriodicalIF":1.3,"publicationDate":"2023-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46292427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hezhi He, Weijie Li, Zong‐ji Huang, Guidong Tian, Z. Zhu
Abstract The rapid development of polymer blends and nanocomposites has put forward new requirements for the mixing performance of extruders. In comparison with shear flow field, extensional flow field has been shown to have unique advantages in improving dispersive mixing performance and reducing energy consumption. However, building an extensional flow field in a conventional single-screw extruder remains challenging. In this work, a new mound-shaped extensional mixing element (M-EME) was designed based on the geometric characteristics of a sine curve. To investigate the effect of this M-EME on the mixing properties of a conventional single-screw extruder, a numerical simulation analysis of this M-EME was performed. The results showed that the proportion of the region with a mixing index greater than 0.55 in the M-EME was higher than 43 %, and that the highest mixing index of the M-EME reached around 0.9, confirming the dominance of the extensional flow field in the M-EME. Moreover, it was observed that the changes in amplitude and period of the sine function have no significant effect on the distribution of the mixing index. The findings from this work provide a viable way to generate extensional flow fields in conventional screw extruders.
{"title":"Numerical analysis of a new mound-shaped extensional mixing element designed based on a sine curve in single-screw extrusion","authors":"Hezhi He, Weijie Li, Zong‐ji Huang, Guidong Tian, Z. Zhu","doi":"10.1515/ipp-2022-4319","DOIUrl":"https://doi.org/10.1515/ipp-2022-4319","url":null,"abstract":"Abstract The rapid development of polymer blends and nanocomposites has put forward new requirements for the mixing performance of extruders. In comparison with shear flow field, extensional flow field has been shown to have unique advantages in improving dispersive mixing performance and reducing energy consumption. However, building an extensional flow field in a conventional single-screw extruder remains challenging. In this work, a new mound-shaped extensional mixing element (M-EME) was designed based on the geometric characteristics of a sine curve. To investigate the effect of this M-EME on the mixing properties of a conventional single-screw extruder, a numerical simulation analysis of this M-EME was performed. The results showed that the proportion of the region with a mixing index greater than 0.55 in the M-EME was higher than 43 %, and that the highest mixing index of the M-EME reached around 0.9, confirming the dominance of the extensional flow field in the M-EME. Moreover, it was observed that the changes in amplitude and period of the sine function have no significant effect on the distribution of the mixing index. The findings from this work provide a viable way to generate extensional flow fields in conventional screw extruders.","PeriodicalId":14410,"journal":{"name":"International Polymer Processing","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2023-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45519847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract In capillary rheometry of a polymer melt, the total pressure drop consists of three primary components: shear viscosity, extensional viscosity, and normal stress differences. Traditionally, viscoelastic constitutive equations have been used to produce accurate predictions regarding the pressure drop. It is difficult to investigate the primary components in past experimental measurements and numerical computations. The useful improvement of the classic White-Metzner viscoelastic constitutive equation coupled with the weighted shear/extension viscosity is performed in isothermal capillary flow simulations. It is significant to analyze the extension-induced pressure drop for a short die and the shear-induced pressure drop for a long die, along with a small contribution of normal stress differences.
{"title":"Numerical investigation of pressure drop within isothermal capillary rheometry for viscous and viscoelastic fluids","authors":"H. Tseng","doi":"10.1515/ipp-2022-4322","DOIUrl":"https://doi.org/10.1515/ipp-2022-4322","url":null,"abstract":"Abstract In capillary rheometry of a polymer melt, the total pressure drop consists of three primary components: shear viscosity, extensional viscosity, and normal stress differences. Traditionally, viscoelastic constitutive equations have been used to produce accurate predictions regarding the pressure drop. It is difficult to investigate the primary components in past experimental measurements and numerical computations. The useful improvement of the classic White-Metzner viscoelastic constitutive equation coupled with the weighted shear/extension viscosity is performed in isothermal capillary flow simulations. It is significant to analyze the extension-induced pressure drop for a short die and the shear-induced pressure drop for a long die, along with a small contribution of normal stress differences.","PeriodicalId":14410,"journal":{"name":"International Polymer Processing","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2023-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44147201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Rajamanickam, Natarajan Ponnusamy, M. Mohanraj, Arockia Julias Arulraj
Abstract An experiential research on mechanical and tribological characteristics of snake grass and sisal fiber reinforced hybrid polymer (epoxy) composites was carried out and reported in this article. The snake grass and sisal fibers were initially treated with 5% sodium hydroxide (NaOH). Hybrid composite samples were fabricated using a compression moulding technique with a total fiber weight ratio of 30% and an epoxy resin weight ratio of 70%. The proportions of snake grass and sisal fibers in the hybrid composites were 70:30, 50:50, and 30:70. The fabricated hybrid composite samples were subjected to flexural, tensile, interlaminar shear strength, Shore D hardness, water absorption, and wear tests as per ASTM international standards, and the outcomes were compared with the results of snake grass and sisal mono fiber composites. The results disclosed that the 30:70 (SG:S) hybrid composite has higher mechanical characteristics than those of other hybrid and mono fiber composites. Also, the 30:70 hybrid sample performed at par with the sisal mono composite in wear and water absorption characteristics. Optical microscopy examination of alkali-treated natural hybrid and mono fiber composites displayed excellent results in terms of interfacial bonding between polymer and fiber.
{"title":"Experimental investigation on mechanical and tribological characteristics of snake grass/sisal fiber reinforced hybrid composites","authors":"S. Rajamanickam, Natarajan Ponnusamy, M. Mohanraj, Arockia Julias Arulraj","doi":"10.1515/ipp-2022-4301","DOIUrl":"https://doi.org/10.1515/ipp-2022-4301","url":null,"abstract":"Abstract An experiential research on mechanical and tribological characteristics of snake grass and sisal fiber reinforced hybrid polymer (epoxy) composites was carried out and reported in this article. The snake grass and sisal fibers were initially treated with 5% sodium hydroxide (NaOH). Hybrid composite samples were fabricated using a compression moulding technique with a total fiber weight ratio of 30% and an epoxy resin weight ratio of 70%. The proportions of snake grass and sisal fibers in the hybrid composites were 70:30, 50:50, and 30:70. The fabricated hybrid composite samples were subjected to flexural, tensile, interlaminar shear strength, Shore D hardness, water absorption, and wear tests as per ASTM international standards, and the outcomes were compared with the results of snake grass and sisal mono fiber composites. The results disclosed that the 30:70 (SG:S) hybrid composite has higher mechanical characteristics than those of other hybrid and mono fiber composites. Also, the 30:70 hybrid sample performed at par with the sisal mono composite in wear and water absorption characteristics. Optical microscopy examination of alkali-treated natural hybrid and mono fiber composites displayed excellent results in terms of interfacial bonding between polymer and fiber.","PeriodicalId":14410,"journal":{"name":"International Polymer Processing","volume":"38 1","pages":"331 - 342"},"PeriodicalIF":1.3,"publicationDate":"2023-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41446587","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract A modified White-Metzner viscoelastic constitutive equation is incorporated into the state-of-the-art Three Dimensional Computational Fluid Dynamics (3D-CFD) framework for performing isothermal and non-isothermal entry flow simulations of a polymer melt. As a result, the corner vortex becomes smaller with increased isothermal temperature, namely, the so-called temperature-induced vortex reduction. In addition, the vortex grows with raising wall temperatures, whereas the vortex reduction is found under high inlet temperatures. Through the visualized flow patterns, it is significant to investigate the dramatic variations of vortex size in relation to fluid temperature, weighted viscosity and extension rate, as well as Weissenberg number and Trouton ratio.
{"title":"Non-isothermal simulation of a corner vortex within entry flow for a viscoelastic fluid","authors":"H. Tseng","doi":"10.1515/ipp-2022-4312","DOIUrl":"https://doi.org/10.1515/ipp-2022-4312","url":null,"abstract":"Abstract A modified White-Metzner viscoelastic constitutive equation is incorporated into the state-of-the-art Three Dimensional Computational Fluid Dynamics (3D-CFD) framework for performing isothermal and non-isothermal entry flow simulations of a polymer melt. As a result, the corner vortex becomes smaller with increased isothermal temperature, namely, the so-called temperature-induced vortex reduction. In addition, the vortex grows with raising wall temperatures, whereas the vortex reduction is found under high inlet temperatures. Through the visualized flow patterns, it is significant to investigate the dramatic variations of vortex size in relation to fluid temperature, weighted viscosity and extension rate, as well as Weissenberg number and Trouton ratio.","PeriodicalId":14410,"journal":{"name":"International Polymer Processing","volume":"38 1","pages":"362 - 374"},"PeriodicalIF":1.3,"publicationDate":"2023-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49456863","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Process monitoring systems are playing an increasingly important role in reducing production capacity losses in injection molding. Process monitoring and optimization systems are mostly based on processing data of injection molding machine control systems. These data consist of scalar data and time series. This paper introduces a novel approach to modelling injection molding processes using only time series data and evaluates the quantitative influences of varying sampling times on calculation of integral values and model quality. On the basis of the first experiment, it is shown that the sampling rates of these time series have a large influence on information which can be derived from this data (e.g. injection work). These findings provide an assessment of whether the effort is justified for the respective requirements on the accuracy of the injection work and other parameters derived from the time series. In the second experiment, a model is presented which uses only the injection flow and injection pressure profile as input and achieves high coefficients of determination for the prediction of the part weight, despite the absence of mold sensor data and scalar data. It is shown that higher sampling rates of time series results in higher prediction quality of these models. This improves the understanding of the data needed for high quality machine learning models of injection molding processes and enable users to estimate a lower bound for the sample rates of time series for their use cases.
{"title":"Time series data for process monitoring in injection molding: a quantitative study of the benefits of a high sampling rate","authors":"Lucas Bogedale, Alexander Schrodt, H. Heim","doi":"10.1515/ipp-2022-4258","DOIUrl":"https://doi.org/10.1515/ipp-2022-4258","url":null,"abstract":"Abstract Process monitoring systems are playing an increasingly important role in reducing production capacity losses in injection molding. Process monitoring and optimization systems are mostly based on processing data of injection molding machine control systems. These data consist of scalar data and time series. This paper introduces a novel approach to modelling injection molding processes using only time series data and evaluates the quantitative influences of varying sampling times on calculation of integral values and model quality. On the basis of the first experiment, it is shown that the sampling rates of these time series have a large influence on information which can be derived from this data (e.g. injection work). These findings provide an assessment of whether the effort is justified for the respective requirements on the accuracy of the injection work and other parameters derived from the time series. In the second experiment, a model is presented which uses only the injection flow and injection pressure profile as input and achieves high coefficients of determination for the prediction of the part weight, despite the absence of mold sensor data and scalar data. It is shown that higher sampling rates of time series results in higher prediction quality of these models. This improves the understanding of the data needed for high quality machine learning models of injection molding processes and enable users to estimate a lower bound for the sample rates of time series for their use cases.","PeriodicalId":14410,"journal":{"name":"International Polymer Processing","volume":"38 1","pages":"167 - 174"},"PeriodicalIF":1.3,"publicationDate":"2023-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47238065","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract A new environmental friendly flame retardant manganese phytate (MnPa) was prepared by a direct precipitation method and the polyurethane foam (PUF) modified with MnPa was obtained by a one-step all-water foaming method. The thermal stability and combustion performance of the MnPa-modified PUF (MnPUF) were investigated by using thermogravimetric (TG), thermal decomposition kinetics, smoke density characterization, limiting oxygen index (LOI) and UL-94 horizontal combustion test. The results indicated that the addition of MnPa significantly improved the thermal stability and combustion performance of the modified PUF. On the basis of the thermogravimetric analysis, Flynn-Wall-Ozawa method, Kissinger method and Coats Redfern method, it could be concluded that PUF with 7.5 wt% MnPa (MnPUF3) had the highest activation energy and the best thermal stability. Smoke density analysis, LOI and horizontal combustion analysis also showed that the addition of MnPa was positively correlated with smoke suppression, LOI value and burning time. The current research results can provide a reference for the subsequent flame retardant modification of PUF.
{"title":"Study on the thermal stability and combustion performance of polyurethane foams modified with manganese phytate","authors":"Xu Zhang, Dehe Yuan, Simiao Sun, Handong Li, Zhi Wang, Hua Xie","doi":"10.1515/ipp-2022-4278","DOIUrl":"https://doi.org/10.1515/ipp-2022-4278","url":null,"abstract":"Abstract A new environmental friendly flame retardant manganese phytate (MnPa) was prepared by a direct precipitation method and the polyurethane foam (PUF) modified with MnPa was obtained by a one-step all-water foaming method. The thermal stability and combustion performance of the MnPa-modified PUF (MnPUF) were investigated by using thermogravimetric (TG), thermal decomposition kinetics, smoke density characterization, limiting oxygen index (LOI) and UL-94 horizontal combustion test. The results indicated that the addition of MnPa significantly improved the thermal stability and combustion performance of the modified PUF. On the basis of the thermogravimetric analysis, Flynn-Wall-Ozawa method, Kissinger method and Coats Redfern method, it could be concluded that PUF with 7.5 wt% MnPa (MnPUF3) had the highest activation energy and the best thermal stability. Smoke density analysis, LOI and horizontal combustion analysis also showed that the addition of MnPa was positively correlated with smoke suppression, LOI value and burning time. The current research results can provide a reference for the subsequent flame retardant modification of PUF.","PeriodicalId":14410,"journal":{"name":"International Polymer Processing","volume":"38 1","pages":"300 - 309"},"PeriodicalIF":1.3,"publicationDate":"2023-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47166621","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","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：