Pub Date : 2021-09-15DOI: 10.37394/232011.2021.16.16
A. B. Kostrichenko, Kyaw Ye Ko
In this work, devoted to the preparation and study of the properties of copper-containing nanocomposites based on linear low density polyethylene, it is shown that the composition of the resulting nanocomposite is not complicated by phase transformations during its synthesis. Varying the concentration of copper (II) formate (1.2÷50.8 wt%) makes it possible to control the size of the formed nanoparticles (10.2±2.0÷ 21.3±1,5 nm). It has been shown that the presence of Cu nanoparticles in a polymer matrix leads to a decrease in its degree of crystallinity - the value decreases from 42% for polyethylene to 37% for 3Cu / LLDPE, which is due to the restriction of the free movement of polymer chain segments by metal nanoparticles and, accordingly, the formation of a less ordered crystal structure.
{"title":"Preparation of Low-Density Polyethylene Composite with Copper Nanoparticles","authors":"A. B. Kostrichenko, Kyaw Ye Ko","doi":"10.37394/232011.2021.16.16","DOIUrl":"https://doi.org/10.37394/232011.2021.16.16","url":null,"abstract":"In this work, devoted to the preparation and study of the properties of copper-containing nanocomposites based on linear low density polyethylene, it is shown that the composition of the resulting nanocomposite is not complicated by phase transformations during its synthesis. Varying the concentration of copper (II) formate (1.2÷50.8 wt%) makes it possible to control the size of the formed nanoparticles (10.2±2.0÷ 21.3±1,5 nm). It has been shown that the presence of Cu nanoparticles in a polymer matrix leads to a decrease in its degree of crystallinity - the value decreases from 42% for polyethylene to 37% for 3Cu / LLDPE, which is due to the restriction of the free movement of polymer chain segments by metal nanoparticles and, accordingly, the formation of a less ordered crystal structure.","PeriodicalId":53603,"journal":{"name":"WSEAS Transactions on Applied and Theoretical Mechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41957459","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 : 2021-09-15DOI: 10.37394/232011.2021.16.15
S. Radaev
The article provides an algorithm for calculating the limiting characteristics of heat pipes for cooling active phased antenna arrays at a given saturation temperature. The maximum transmitted power is determined taking into account the limitations of the heat pipes operation by the capillary limit, by boiling (transition to film boiling, boiling limit), by the sonic limit at which the speed of steam reaches the speed of sound (sonic limit), by the entrainment of droplets liquid coolant from the surface of the wick with a counter flow of steam (entertainment limit) and viscous limit, which is realized at low temperatures (viscous limit). It is shown that an increase in the thickness of the wick and its porosity may be necessary to increase the capillary limit of heat pipes, while an increase in the thickness of the wick increases the thermal resistance of the tube and, accordingly, can lead to overheating of the cooled elements. Based on the above algorithm, design calculations for two types of heat pipes have been carried out. The dependences of various limits of the heat pipe on the operating temperature are plotted. Based on the above algorithm, calculations were performed for two types of heat pipes.
{"title":"Design Calculations of the Limiting Characteristics of Heat Pipes for Cooling Active Phased Antenna Arrays","authors":"S. Radaev","doi":"10.37394/232011.2021.16.15","DOIUrl":"https://doi.org/10.37394/232011.2021.16.15","url":null,"abstract":"The article provides an algorithm for calculating the limiting characteristics of heat pipes for cooling active phased antenna arrays at a given saturation temperature. The maximum transmitted power is determined taking into account the limitations of the heat pipes operation by the capillary limit, by boiling (transition to film boiling, boiling limit), by the sonic limit at which the speed of steam reaches the speed of sound (sonic limit), by the entrainment of droplets liquid coolant from the surface of the wick with a counter flow of steam (entertainment limit) and viscous limit, which is realized at low temperatures (viscous limit). It is shown that an increase in the thickness of the wick and its porosity may be necessary to increase the capillary limit of heat pipes, while an increase in the thickness of the wick increases the thermal resistance of the tube and, accordingly, can lead to overheating of the cooled elements. Based on the above algorithm, design calculations for two types of heat pipes have been carried out. The dependences of various limits of the heat pipe on the operating temperature are plotted. Based on the above algorithm, calculations were performed for two types of heat pipes.","PeriodicalId":53603,"journal":{"name":"WSEAS Transactions on Applied and Theoretical Mechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43426745","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 : 2021-09-15DOI: 10.37394/232011.2021.16.17
G. Kriven, Ying Sun
In this work, we studied the Mössbauer spectra of magnetite samples of various compositions. To protect magnetite from oxidation, the resulting particles are coated with protective shells, among which silanes are promising, which polymerize on the surface of magnetite nanoparticles, forming strong covalent bonds. The coating of nanoparticles protects them from aggressive environmental influences, evens out their size distribution, and also protects the environment from the possible toxic effects of the particles themselves. It was shown that the magnetite phase predominates in the sample of native particles, the coating of native particles with alkoxysilane does not lead to fundamental changes in the phase state of the sample particles, and oxidation with nitric acid leads to the complete transformation of magnetite into maghemite. It is obvious that the reason for the distortions of the relaxation nature in the Mössbauer spectra of the samples is the small sizes of the iron-containing domains, which allows us to consider the description of the spectra within the framework of the model of multilevel superparamagnetic relaxation.
{"title":"Study of Magnetite Nanoparticles by the Method of Mössbauer Spectroscopy","authors":"G. Kriven, Ying Sun","doi":"10.37394/232011.2021.16.17","DOIUrl":"https://doi.org/10.37394/232011.2021.16.17","url":null,"abstract":"In this work, we studied the Mössbauer spectra of magnetite samples of various compositions. To protect magnetite from oxidation, the resulting particles are coated with protective shells, among which silanes are promising, which polymerize on the surface of magnetite nanoparticles, forming strong covalent bonds. The coating of nanoparticles protects them from aggressive environmental influences, evens out their size distribution, and also protects the environment from the possible toxic effects of the particles themselves. It was shown that the magnetite phase predominates in the sample of native particles, the coating of native particles with alkoxysilane does not lead to fundamental changes in the phase state of the sample particles, and oxidation with nitric acid leads to the complete transformation of magnetite into maghemite. It is obvious that the reason for the distortions of the relaxation nature in the Mössbauer spectra of the samples is the small sizes of the iron-containing domains, which allows us to consider the description of the spectra within the framework of the model of multilevel superparamagnetic relaxation.","PeriodicalId":53603,"journal":{"name":"WSEAS Transactions on Applied and Theoretical Mechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47597696","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 : 2021-09-09DOI: 10.37394/232011.2021.16.14
O. Egorova, T. Hein
As a result of the experiments, epoxy nanocomposites based on titanium dioxide nanoparticles in the form of opaque blue-gray films were obtained. The composition and structure of epoxy nanocomposites were studied by scanning electron microscopy and infrared spectroscopy. The properties of the obtained film nanocomposites were investigated to determine the glass transition temperature, and the mechanical properties of the films were tested in tension, where the tensile strength, elastic modulus, and relative deformation were determined
{"title":"Improvement of Mechanical Properties of Polymer Materials by the Nanosized Ceramic Particles","authors":"O. Egorova, T. Hein","doi":"10.37394/232011.2021.16.14","DOIUrl":"https://doi.org/10.37394/232011.2021.16.14","url":null,"abstract":"As a result of the experiments, epoxy nanocomposites based on titanium dioxide nanoparticles in the form of opaque blue-gray films were obtained. The composition and structure of epoxy nanocomposites were studied by scanning electron microscopy and infrared spectroscopy. The properties of the obtained film nanocomposites were investigated to determine the glass transition temperature, and the mechanical properties of the films were tested in tension, where the tensile strength, elastic modulus, and relative deformation were determined","PeriodicalId":53603,"journal":{"name":"WSEAS Transactions on Applied and Theoretical Mechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43269885","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 : 2021-09-06DOI: 10.37394/232011.2021.16.13
A. Perchenok, E. Suvorova, A. Farmakovskaya, V. Kohlert
The stability of aqueous dispersed systems of TiO2 and Fe2O3 microparticles in the presence of a water-soluble polymer - ethylhydroxyethylcellulose (EHEC) - has been studied under the condition of using two methods of mechanoactivation of the pigment surface - processing them in a disintegrator and in an ultrasonic field. It is shown that in the absence of a polymer stabilizer, an intense effect on aqueous dispersed systems of pigments leads to rapid coagulation of particles. In the presence of EHEC, a small stabilizing effect is observed, which is significantly enhanced when processing dispersed systems in a disintegrator and in an ultrasonic field. In this case, the stability of dispersed systems depends little on the method of mechanoactivation of their surface, but significantly depends on the duration of the intense exposure.
{"title":"Stabilization of Aqueous Dispersions of Inorganic Microparticles Under Mechanical Activation","authors":"A. Perchenok, E. Suvorova, A. Farmakovskaya, V. Kohlert","doi":"10.37394/232011.2021.16.13","DOIUrl":"https://doi.org/10.37394/232011.2021.16.13","url":null,"abstract":"The stability of aqueous dispersed systems of TiO2 and Fe2O3 microparticles in the presence of a water-soluble polymer - ethylhydroxyethylcellulose (EHEC) - has been studied under the condition of using two methods of mechanoactivation of the pigment surface - processing them in a disintegrator and in an ultrasonic field. It is shown that in the absence of a polymer stabilizer, an intense effect on aqueous dispersed systems of pigments leads to rapid coagulation of particles. In the presence of EHEC, a small stabilizing effect is observed, which is significantly enhanced when processing dispersed systems in a disintegrator and in an ultrasonic field. In this case, the stability of dispersed systems depends little on the method of mechanoactivation of their surface, but significantly depends on the duration of the intense exposure.","PeriodicalId":53603,"journal":{"name":"WSEAS Transactions on Applied and Theoretical Mechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43247441","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 : 2021-09-01DOI: 10.37394/232011.2021.16.12
A. Orekhov, E. Shemetova, Y. Min
For the first time, using the technology of selective laser sintering, prototypes of rocket engine compressor blades were manufactured with subsequent analysis of the strength, technological, physical and mechanical characteristics of the product. The physical and mechanical properties of the manufactured blades were investigated, it was found that the short-term strength limit at 20 °C is 1450 MPa, and at 300 °C the ultimate strength is 1300 MPa, thus thermal losses in deformation resistance are no more than 12%, which allows the material to be used in aircraft construction, including for supersonic aircraft
{"title":"Fabrication and Testing of Rocket Engine Construction Elements by Addictive Production Approach","authors":"A. Orekhov, E. Shemetova, Y. Min","doi":"10.37394/232011.2021.16.12","DOIUrl":"https://doi.org/10.37394/232011.2021.16.12","url":null,"abstract":"For the first time, using the technology of selective laser sintering, prototypes of rocket engine compressor blades were manufactured with subsequent analysis of the strength, technological, physical and mechanical characteristics of the product. The physical and mechanical properties of the manufactured blades were investigated, it was found that the short-term strength limit at 20 °C is 1450 MPa, and at 300 °C the ultimate strength is 1300 MPa, thus thermal losses in deformation resistance are no more than 12%, which allows the material to be used in aircraft construction, including for supersonic aircraft","PeriodicalId":53603,"journal":{"name":"WSEAS Transactions on Applied and Theoretical Mechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42791492","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 : 2021-08-31DOI: 10.37394/232011.2021.16.11
Pardeep Kumar, Suversha Gupta
The effect of finite Larmor radius of the ions on thermal convection of a plasma is investigated. The case with vertical magnetic field is discussed. Following linear stability theory and normal mode analysis method, the dispersion relation is obtained. It is found that the presence of finite Larmor radius and magnetic field introduces oscillatory modes in the system which were, otherwise, non-existent in their absence. When the instability sets in as stationary convection, finite Larmor radius is found to have a stabilizing effect. Medium permeability has a destabilizing (or stabilizing) effect and the magnetic field has a stabilizing (or destabilizing) effect under certain conditions in the presence of finite Larmor radius effect whereas in the absence of finite Larmor radius effect, the medium permeability and the magnetic field have destabilizing and stabilizing effects, respectively. The sufficient conditions for the non-existence of overstability are also obtained.
{"title":"On Thermal Convection of a Plasma in Porous Medium","authors":"Pardeep Kumar, Suversha Gupta","doi":"10.37394/232011.2021.16.11","DOIUrl":"https://doi.org/10.37394/232011.2021.16.11","url":null,"abstract":"The effect of finite Larmor radius of the ions on thermal convection of a plasma is investigated. The case with vertical magnetic field is discussed. Following linear stability theory and normal mode analysis method, the dispersion relation is obtained. It is found that the presence of finite Larmor radius and magnetic field introduces oscillatory modes in the system which were, otherwise, non-existent in their absence. When the instability sets in as stationary convection, finite Larmor radius is found to have a stabilizing effect. Medium permeability has a destabilizing (or stabilizing) effect and the magnetic field has a stabilizing (or destabilizing) effect under certain conditions in the presence of finite Larmor radius effect whereas in the absence of finite Larmor radius effect, the medium permeability and the magnetic field have destabilizing and stabilizing effects, respectively. The sufficient conditions for the non-existence of overstability are also obtained.","PeriodicalId":53603,"journal":{"name":"WSEAS Transactions on Applied and Theoretical Mechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45388906","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 : 2021-08-30DOI: 10.37394/232011.2021.16.10
Naima Bouhabza, Kamel Kara, M. Hadjili
Optimized Proportional Integral Derivative controllers are designed to control the translational and rotational motions of a quadrotor system with six degrees of freedom. The teaching learning based optimization algorithm is used to obtain the proportional, integral and derivative gains of six PID controllers so that the integral time absolute error criterion is minimized. The control objective, is to enforce the horizontal position, altitude and yaw angle of the quadrotor to track their desired reference trajectories while stabilizing its roll and pitch angles. The efficiency and the control performance of the proposed scheme are demonstrated through numerical simulation and compared with those of the PID controllers designed using genetic algorithm, the sliding mode control and other control techniques proposed in the literature. The simulation study shows the good performance of the proposed control scheme in terms of transient response characteristics, tracking accuracy and disturbance rejection.
{"title":"PID Controllers Design for a Quadrotor System Using Teaching Learning Based Optimization","authors":"Naima Bouhabza, Kamel Kara, M. Hadjili","doi":"10.37394/232011.2021.16.10","DOIUrl":"https://doi.org/10.37394/232011.2021.16.10","url":null,"abstract":"Optimized Proportional Integral Derivative controllers are designed to control the translational and rotational motions of a quadrotor system with six degrees of freedom. The teaching learning based optimization algorithm is used to obtain the proportional, integral and derivative gains of six PID controllers so that the integral time absolute error criterion is minimized. The control objective, is to enforce the horizontal position, altitude and yaw angle of the quadrotor to track their desired reference trajectories while stabilizing its roll and pitch angles. The efficiency and the control performance of the proposed scheme are demonstrated through numerical simulation and compared with those of the PID controllers designed using genetic algorithm, the sliding mode control and other control techniques proposed in the literature. The simulation study shows the good performance of the proposed control scheme in terms of transient response characteristics, tracking accuracy and disturbance rejection.","PeriodicalId":53603,"journal":{"name":"WSEAS Transactions on Applied and Theoretical Mechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43112321","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 : 2021-08-11DOI: 10.37394/232011.2021.16.9
S. Dajani, M. A. Zaytoon, M. Hamdan
Equations governing the flow of a fluid-particle mixture with variable viscosity through a porous structure are developed. Method of intrinsic volume averaging is used to average Saffman’s dusty gas equations. A modelling flexibility is offered in this work by introducing a dust-phase partial pressure in the governing equations, interpreted as the pressure necessary to maintain a uniform particle distribution in the flow field. Viscosity of the fluid-particle mixture is assumed to be variable, with variations in viscosity being due to fluid pressure. Particles are assumed spherical and Stokes’ coefficient of resistance is expressed in terms of the pressure-dependent fluid viscosity. Both Darcy resistance and the Forchheimer micro-inertial effects are accounted for in the developed model
{"title":"Two-Pressure Model of Particle-Fluid Mixture Flow with Pressure-Dependent Viscosity in a Porous Medium","authors":"S. Dajani, M. A. Zaytoon, M. Hamdan","doi":"10.37394/232011.2021.16.9","DOIUrl":"https://doi.org/10.37394/232011.2021.16.9","url":null,"abstract":"Equations governing the flow of a fluid-particle mixture with variable viscosity through a porous structure are developed. Method of intrinsic volume averaging is used to average Saffman’s dusty gas equations. A modelling flexibility is offered in this work by introducing a dust-phase partial pressure in the governing equations, interpreted as the pressure necessary to maintain a uniform particle distribution in the flow field. Viscosity of the fluid-particle mixture is assumed to be variable, with variations in viscosity being due to fluid pressure. Particles are assumed spherical and Stokes’ coefficient of resistance is expressed in terms of the pressure-dependent fluid viscosity. Both Darcy resistance and the Forchheimer micro-inertial effects are accounted for in the developed model","PeriodicalId":53603,"journal":{"name":"WSEAS Transactions on Applied and Theoretical Mechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44276172","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 : 2021-08-10DOI: 10.37394/232011.2021.16.7
Ivan Kazachkov
Based on the earlier developed mathematical model of the complex flow due to the double rotations in two perpendicular directions, the stability analysis is performed in the paper. The Navier-Stokes equations are derived in the coordinate system rotating around the two perpendicular different axes, the vertical one of them is arranged on some distance from the other axis of rotation, the horizontal axis is directed along the tangential line to the circle of the vertical rotation. The two centrifugal and Coriolis forces create the unique features in high oscillating flow, with localities of the stretched liquid, due to their action varying by the circumferential cylindrical coordinate in the channel flow. Stability analysis for the complex rotational flow under double rotations creating strongly varying mass forces and stretching of the liquid is considered at first
{"title":"Stability Analysis for Complex Rotational Flow","authors":"Ivan Kazachkov","doi":"10.37394/232011.2021.16.7","DOIUrl":"https://doi.org/10.37394/232011.2021.16.7","url":null,"abstract":"Based on the earlier developed mathematical model of the complex flow due to the double rotations in two perpendicular directions, the stability analysis is performed in the paper. The Navier-Stokes equations are derived in the coordinate system rotating around the two perpendicular different axes, the vertical one of them is arranged on some distance from the other axis of rotation, the horizontal axis is directed along the tangential line to the circle of the vertical rotation. The two centrifugal and Coriolis forces create the unique features in high oscillating flow, with localities of the stretched liquid, due to their action varying by the circumferential cylindrical coordinate in the channel flow. Stability analysis for the complex rotational flow under double rotations creating strongly varying mass forces and stretching of the liquid is considered at first","PeriodicalId":53603,"journal":{"name":"WSEAS Transactions on Applied and Theoretical Mechanics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48352154","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：