An important aspect in electronic packaging is the heat dissipation. Flip-chip technology is widely being used to increase the rate of heat transfer from the chip. A method to further enhance the thermal conductivity is by the use of a thermal interface material between the device and the heat sink attached to it in the flip-chip technology. Percolation theory holds a key to understanding the behavior of thermal interface materials. Percolation, used widely in electrical engineering, is a physical phenomenon in which the highly conducting particles distributed randomly in the matrix form at least one continuous chain connecting the opposite faces of the matrix. This phenomenon was simulated using the matrix method, to study the effect of different shapes and size of the filler particles. The different shapes considered were spherical, vertical or horizontal rods, and flakes in horizontal or vertical orientation. The effect of the size of these particles was also examined. The results indicate that the composites with particles having the largest side in the direction of heat flow will always have a better conductivity than the particles oriented normal to it. Also, from the results, we can choose the best filler size in the composite if we know the filler concentration we are aiming at.
{"title":"Percolation Theory Applied to Study the Effect of Shape and Size of the Filler Particles in Thermal Interface Materials","authors":"A. Devpura, P. Phelan, R. Prasher","doi":"10.1115/imece2000-1541","DOIUrl":"https://doi.org/10.1115/imece2000-1541","url":null,"abstract":"\u0000 An important aspect in electronic packaging is the heat dissipation. Flip-chip technology is widely being used to increase the rate of heat transfer from the chip. A method to further enhance the thermal conductivity is by the use of a thermal interface material between the device and the heat sink attached to it in the flip-chip technology. Percolation theory holds a key to understanding the behavior of thermal interface materials. Percolation, used widely in electrical engineering, is a physical phenomenon in which the highly conducting particles distributed randomly in the matrix form at least one continuous chain connecting the opposite faces of the matrix. This phenomenon was simulated using the matrix method, to study the effect of different shapes and size of the filler particles. The different shapes considered were spherical, vertical or horizontal rods, and flakes in horizontal or vertical orientation. The effect of the size of these particles was also examined. The results indicate that the composites with particles having the largest side in the direction of heat flow will always have a better conductivity than the particles oriented normal to it. Also, from the results, we can choose the best filler size in the composite if we know the filler concentration we are aiming at.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128689960","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}
This paper addresses the examination of heat transfer in parallel-plate channels using a combination of two passive schemes: (1) the insertion of an auxiliary plate at the mouth and (2) the appendage of colinear insulated plates at the exit. The investigation is made by numerically solving the full elliptic Navier-Stokes and energy equation in a I-type computational domain. The channel is symmetrically heated by uniform heat flux. The working fluid is air. The results are reported in terms of induced mass flow rate and maximum wall temperatures. Further, the local Nusselt number, the mean Nusselt number and pressure profiles are presented. The analyzed Grashof numbers based on the heated plate height are 103 and 106.
{"title":"Aggregate Intensification of Natural Convection Between Air and a Vertical Parallel-Plate Channel by Inserting an Auxiliary Plate at the Mouth and Appending Colinear Insulated Plates at the Exit","authors":"A. Andreozzi, O. Manca, A. Campo","doi":"10.1115/imece2000-1547","DOIUrl":"https://doi.org/10.1115/imece2000-1547","url":null,"abstract":"\u0000 This paper addresses the examination of heat transfer in parallel-plate channels using a combination of two passive schemes: (1) the insertion of an auxiliary plate at the mouth and (2) the appendage of colinear insulated plates at the exit. The investigation is made by numerically solving the full elliptic Navier-Stokes and energy equation in a I-type computational domain. The channel is symmetrically heated by uniform heat flux. The working fluid is air. The results are reported in terms of induced mass flow rate and maximum wall temperatures. Further, the local Nusselt number, the mean Nusselt number and pressure profiles are presented. The analyzed Grashof numbers based on the heated plate height are 103 and 106.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124538589","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 effect of heat transfer on the performance of the EHD induction pumping of a liquid/vapor stratified medium is theoretically investigated. The analytical domain considered is represented by a two-dimensional developing plane channel flow of a liquid separated from a vapor by a horizontal interface in a channel bound from below and above by two infinite rigid boundaries. The electrodes generating the electric traveling wave are placed at the bottom of the liquid film. The liquid temperature is assumed constant at the interface of liquid/vapor media while the liquid is cooled or heated at the lower boundary. The dimensionless numerical results are obtained for three different dimensionless wall heat fluxes representing no heat transfer, cooling, and heating at the lower boundary. The controlling parameters include: vapor height, liquid height, voltage, wavelength, and frequency. For the selected operating conditions, the performance of the pump increases with increasing wall heat flux.
{"title":"Electrohydrodynamic Induction Pumping of a Stratified Liquid/Vapor Medium in the Presence of Heat Transfer","authors":"K. Brand, J. Seyed-Yagoobi","doi":"10.1115/imece2000-1516","DOIUrl":"https://doi.org/10.1115/imece2000-1516","url":null,"abstract":"\u0000 The effect of heat transfer on the performance of the EHD induction pumping of a liquid/vapor stratified medium is theoretically investigated. The analytical domain considered is represented by a two-dimensional developing plane channel flow of a liquid separated from a vapor by a horizontal interface in a channel bound from below and above by two infinite rigid boundaries. The electrodes generating the electric traveling wave are placed at the bottom of the liquid film. The liquid temperature is assumed constant at the interface of liquid/vapor media while the liquid is cooled or heated at the lower boundary. The dimensionless numerical results are obtained for three different dimensionless wall heat fluxes representing no heat transfer, cooling, and heating at the lower boundary. The controlling parameters include: vapor height, liquid height, voltage, wavelength, and frequency. For the selected operating conditions, the performance of the pump increases with increasing wall heat flux.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127756397","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}
For safety analyses of nuclear reactor cores, a correct prediction of the thermal-hydraulic characteristics is crucial. These predictions are all the more difficult as the flows generally involve liquid and vapor phases simultaneously. Moreover, the geometry of nuclear cores is often quite complex. The typical situation is that of a rod bundle, the characteristic length of the gap between two rods being much smaller than the size of the bundle. The traditional approach to the simulation of such flows is called the sub-channel analysis. The flow is assumed to have a privileged direction, and the cross-flow inertia effects are neglected. Moreover, a lumped-geometry approach is generally adopted, whereby a single discretization cell is used to represent the volume between several rods. This leads to efficient solution methods but forbids a precise description of local or global three-dimensional effects. As the computational power of modem computers steadily increases, a finer description of the flows in nuclear reactor cores becomes possible. Indeed, there is a current trend in the nuclear industry toward a CFD-like description of these flows as shown by Paillère, et al., (1998) and Rautaheimo, et al., (1999). However, the numerical method used for the simulation must satisfy some specific requirements: • The use of unstructured meshes must be possible to allow an easy description of the geometry between the rods. • The numerical method must be suitable for variable density (thermally expandable) flows. Cavendish, Hall, and Porsching (1994) present a covolume method designed to meet these requirements. This method relies on the construction of a dual or Voronoi mesh. The pressure and the thermodynamic variables are computed at the vertices of the primal mesh. Additionally, the velocities are computed in the normal direction to each face of the primal mesh, or, equivalently, along each edge of the dual mesh. The continuity equation is integrated by parts on the dual polytopes, while the momentum equations are discretized by finite differences on the primal mesh. This Cavendish, Hall, and Porsching covolume numerical method has been used to solve typical problems of nuclear reactor thermal-hydraulics analysis. The physical models are those of the CORETRAN code (1999). The first numerical results demonstrate the efficiency of the method and validate the new approach.
{"title":"From Sub-Channel Analysis to Two-Phase Flow CFD: Improving Thermal-Hydraulics Analysis of Nuclear Reactor Cores","authors":"Sebastien Clerc, L. Agee, J. Harrison","doi":"10.1115/imece2000-1528","DOIUrl":"https://doi.org/10.1115/imece2000-1528","url":null,"abstract":"\u0000 For safety analyses of nuclear reactor cores, a correct prediction of the thermal-hydraulic characteristics is crucial. These predictions are all the more difficult as the flows generally involve liquid and vapor phases simultaneously. Moreover, the geometry of nuclear cores is often quite complex. The typical situation is that of a rod bundle, the characteristic length of the gap between two rods being much smaller than the size of the bundle.\u0000 The traditional approach to the simulation of such flows is called the sub-channel analysis. The flow is assumed to have a privileged direction, and the cross-flow inertia effects are neglected. Moreover, a lumped-geometry approach is generally adopted, whereby a single discretization cell is used to represent the volume between several rods. This leads to efficient solution methods but forbids a precise description of local or global three-dimensional effects.\u0000 As the computational power of modem computers steadily increases, a finer description of the flows in nuclear reactor cores becomes possible. Indeed, there is a current trend in the nuclear industry toward a CFD-like description of these flows as shown by Paillère, et al., (1998) and Rautaheimo, et al., (1999). However, the numerical method used for the simulation must satisfy some specific requirements:\u0000 • The use of unstructured meshes must be possible to allow an easy description of the geometry between the rods.\u0000 • The numerical method must be suitable for variable density (thermally expandable) flows.\u0000 Cavendish, Hall, and Porsching (1994) present a covolume method designed to meet these requirements. This method relies on the construction of a dual or Voronoi mesh. The pressure and the thermodynamic variables are computed at the vertices of the primal mesh. Additionally, the velocities are computed in the normal direction to each face of the primal mesh, or, equivalently, along each edge of the dual mesh. The continuity equation is integrated by parts on the dual polytopes, while the momentum equations are discretized by finite differences on the primal mesh.\u0000 This Cavendish, Hall, and Porsching covolume numerical method has been used to solve typical problems of nuclear reactor thermal-hydraulics analysis. The physical models are those of the CORETRAN code (1999). The first numerical results demonstrate the efficiency of the method and validate the new approach.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129287044","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}
A thermal response model for designing a hybrid thermal energy storage (TES) heat sink is developed. The stabilization time and maximum operating (hot side) temperature-to-transition temperature difference are used to characterize the performance of the heat sink. The thermal properties of the PCM employed in the design are investigated. Integration of a design optimization algorithm into a thermal performance model of the TES-hybrid heat sink results in determination of a best design subject to geometric and heat loading constraints. A prototype based on this best design is build and used to benchmark the performance model. The performance measured is consistent with the simulation model predictions of performance.
{"title":"Methodology for Designing a Hybrid Thermal Energy Storage Heat Sink","authors":"N. Zheng, R. Wirtz","doi":"10.1115/imece2000-1538","DOIUrl":"https://doi.org/10.1115/imece2000-1538","url":null,"abstract":"\u0000 A thermal response model for designing a hybrid thermal energy storage (TES) heat sink is developed. The stabilization time and maximum operating (hot side) temperature-to-transition temperature difference are used to characterize the performance of the heat sink. The thermal properties of the PCM employed in the design are investigated. Integration of a design optimization algorithm into a thermal performance model of the TES-hybrid heat sink results in determination of a best design subject to geometric and heat loading constraints. A prototype based on this best design is build and used to benchmark the performance model. The performance measured is consistent with the simulation model predictions of performance.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"21 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127561542","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}
This paper reports a numerical study of buoyancy-induced flow and heat transfer in an enclosure with vents. The geometry closely resembles a “set-top-box” application frequently encountered in electronics cooling applications. The heat generating module is modeled as a planar heat source placed on a conducting printed circuit board (PCB). Full 3D and simplified 2D conjugate heat transfer models accounting for conduction and radiation in the solids and conduction and convection in the fluid were used Experiments performed to validate the 3D model have shown excellent comparisons with numerical results. A parametric study involving vent size, power dissipation, number of high conductivity power planes in the PCB has been performed with both the 3D and the 2D models. Although the quantitative results obtained from both types of analyses are similar only under certain conditions, qualitatively, the 2D analysis can be used to obtain useful insights into the complex overall transport mechanisms.
{"title":"Numerical Analysis of Buoyancy-Induced Flow and Heat Transfer in an Enclosure With Vents","authors":"V. Calmidi, S. Sathe","doi":"10.1115/imece2000-1546","DOIUrl":"https://doi.org/10.1115/imece2000-1546","url":null,"abstract":"\u0000 This paper reports a numerical study of buoyancy-induced flow and heat transfer in an enclosure with vents. The geometry closely resembles a “set-top-box” application frequently encountered in electronics cooling applications. The heat generating module is modeled as a planar heat source placed on a conducting printed circuit board (PCB). Full 3D and simplified 2D conjugate heat transfer models accounting for conduction and radiation in the solids and conduction and convection in the fluid were used Experiments performed to validate the 3D model have shown excellent comparisons with numerical results. A parametric study involving vent size, power dissipation, number of high conductivity power planes in the PCB has been performed with both the 3D and the 2D models. Although the quantitative results obtained from both types of analyses are similar only under certain conditions, qualitatively, the 2D analysis can be used to obtain useful insights into the complex overall transport mechanisms.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123187365","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 effect of surfactant concentration on the Marangoni convection around vapor bubbles has been numerically investigated. The model consists of an adiabatic, hemispherical bubble on a downward facing constant temperature heated wall, in a fluid pool with an initial uniform temperature gradient. The time-dependent liquid mass, momentum, energy, surfactant bulk and surface transport, and adsorption kinetic rate equations are solved simultaneously. Conditions for bubble sizes varying from boiling nuclei to growing bubbles, and different surfactant bulk concentrations and wall heat flux levels are represented by a range of Marangoni and Rayleigh numbers: 100 ≤ MaT ≤ 6000, 0 ≤ MaS ≤ 2.2×106, 0 ≤ Ra ≤ 2.2. In the early transients, liquid motion is found to be induced by the temperature non-uniformity over the bubble surface, which along with self-diffusion, transports surfactant molecules from the bulk liquid towards the bubble surface. Consequently, the surface excess concentration is higher at the bubble base and decreases along the interface towards the bubble crown. The resulting concentration gradients promote diffusocapillary flows, which act in the same direction as the temperature-gradient induced thermocapillary flows, thereby enhancing the convection significantly. Also, for conditions representing boiling nuclei (in both partially and fully developed boiling regimes), the initial time transients appear to be heat flux independent.
{"title":"Numerical Investigation of Marangoni Convection Around a Vapor Bubble in Aqueous Surfactant Solutions","authors":"V. Wasekar, R. M. Manglik, M. Jog","doi":"10.1115/imece2000-1533","DOIUrl":"https://doi.org/10.1115/imece2000-1533","url":null,"abstract":"\u0000 The effect of surfactant concentration on the Marangoni convection around vapor bubbles has been numerically investigated. The model consists of an adiabatic, hemispherical bubble on a downward facing constant temperature heated wall, in a fluid pool with an initial uniform temperature gradient. The time-dependent liquid mass, momentum, energy, surfactant bulk and surface transport, and adsorption kinetic rate equations are solved simultaneously. Conditions for bubble sizes varying from boiling nuclei to growing bubbles, and different surfactant bulk concentrations and wall heat flux levels are represented by a range of Marangoni and Rayleigh numbers: 100 ≤ MaT ≤ 6000, 0 ≤ MaS ≤ 2.2×106, 0 ≤ Ra ≤ 2.2. In the early transients, liquid motion is found to be induced by the temperature non-uniformity over the bubble surface, which along with self-diffusion, transports surfactant molecules from the bulk liquid towards the bubble surface. Consequently, the surface excess concentration is higher at the bubble base and decreases along the interface towards the bubble crown. The resulting concentration gradients promote diffusocapillary flows, which act in the same direction as the temperature-gradient induced thermocapillary flows, thereby enhancing the convection significantly. Also, for conditions representing boiling nuclei (in both partially and fully developed boiling regimes), the initial time transients appear to be heat flux independent.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128822593","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 paper the experiments for subcooled water flow and steam-water two-phase flow were conducted to investigate the effects of pulsation upon transient heat transfer characteristics in a closed-circulation helical-coiled tube steam generator. The non-uniform property of local heat transfer with steady flow was also examined. The secondary flow mechanism and the effect of interaction between the flow oscillation and secondary flow were analyzed on the basis of the experimental data. Some new phenomena were observed and explained. A series of correlations were proposed for the average and local heat transfer coefficients both under steady and oscillatory flow conditions. The results showed that there were considerable variations in local and peripherally time-averaged Nusselt numbers for pulsating flow in a wide range of parameters. Systematic investigations of pressure drop type oscillations and their thresholds for steam-water two-phase flow in a uniformly heated helical tube were also reported.
{"title":"Transient Convective Heat Transfer in a Helical Tube With Steam-Water Two-Phase Flow Under Pressure Drop Type Oscillations","authors":"Lie-Jin Guo, Ziyuan Feng","doi":"10.1115/imece2000-1512","DOIUrl":"https://doi.org/10.1115/imece2000-1512","url":null,"abstract":"\u0000 In the present paper the experiments for subcooled water flow and steam-water two-phase flow were conducted to investigate the effects of pulsation upon transient heat transfer characteristics in a closed-circulation helical-coiled tube steam generator. The non-uniform property of local heat transfer with steady flow was also examined. The secondary flow mechanism and the effect of interaction between the flow oscillation and secondary flow were analyzed on the basis of the experimental data. Some new phenomena were observed and explained. A series of correlations were proposed for the average and local heat transfer coefficients both under steady and oscillatory flow conditions. The results showed that there were considerable variations in local and peripherally time-averaged Nusselt numbers for pulsating flow in a wide range of parameters. Systematic investigations of pressure drop type oscillations and their thresholds for steam-water two-phase flow in a uniformly heated helical tube were also reported.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128023966","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}
A study of single bubbles growing on a microscale heater array kept at nominally constant temperature was performed. The behavior of bubbles nucleating at a single site at two different temperatures (22.5 K and 27.5 K superheat) is compared for saturated pool boiling of FC-72 at 1 atm. It is concluded that energy is transferred from the surface through similar heat transfer mechanisms at both superheats. Microlayer evaporation was observed to play a minor role in the overall heat transfer, with microconvection/transient conduction being the dominant mechanism. Evaluation of various heat transfer models are made.
{"title":"Saturated Pool Boiling Mechanisms During Single Bubble Heat Transfer: Comparison at Two Wall Superheats","authors":"Jungho Kim, Fatih Demiray, N. Yaddanapudi","doi":"10.1115/imece2000-1504","DOIUrl":"https://doi.org/10.1115/imece2000-1504","url":null,"abstract":"\u0000 A study of single bubbles growing on a microscale heater array kept at nominally constant temperature was performed. The behavior of bubbles nucleating at a single site at two different temperatures (22.5 K and 27.5 K superheat) is compared for saturated pool boiling of FC-72 at 1 atm. It is concluded that energy is transferred from the surface through similar heat transfer mechanisms at both superheats. Microlayer evaporation was observed to play a minor role in the overall heat transfer, with microconvection/transient conduction being the dominant mechanism. Evaluation of various heat transfer models are made.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124095208","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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