The Experts below are selected from a list of 254793 Experts worldwide ranked by ideXlab platform
Amir Mansourizadeh - One of the best experts on this subject based on the ideXlab platform.
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a developed asymmetric pvdf hollow fiber Membrane Structure for co2 absorption
International Journal of Greenhouse Gas Control, 2011Co-Authors: Amir Mansourizadeh, Ahmad Fauzi IsmailAbstract:Abstract Carbon dioxide (CO 2 ), the main greenhouse gas, has been associated with global climate change. Therefore, it is important to develop technologies to mitigate this issue. In present study, porous hydrophobic polyvinylidene fluoride (PVDF) hollow fiber Membranes with developed Structure for CO 2 absorption were prepared via a wet spinning process. The prepared Membranes were characterized in terms of morphology examination, gas permeability, critical water entry pressure (CEP w ) and mass transfer resistance. From the morphology examination, the Membrane showed an almost sponge-like Structure with inner skinless layer and ultra-thin outer skin layer. Results of gas permeation test indicated that the Membrane possess very small mean pore size (3.96 nm) with high surface porosity. The CO 2 absorption experiment demonstrated a significant improvement in the CO 2 flux of the prepared PVDF Membrane compared to the commercial porous polytetrafluoroethylene (PTFE) hollow fiber Membrane. At the absorbent flow rate of 200 ml/min, CO 2 flux of the PVDF Membrane (4.10 × 10 −4 mol/m 2 s) was approximately 68% higher than the CO 2 flux of the PTFE Membrane. In addition, the results indicated that an approximate 25% CO 2 flux reduction was gradually occurred at initial 26 h, then the CO 2 flux maintained constant over 140 h of the operation.
Zhoulian Zheng - One of the best experts on this subject based on the ideXlab platform.
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impact induced nonlinear damped vibration of fabric Membrane Structure theory analysis experiment and parametric study
Composites Part B-engineering, 2019Co-Authors: Xiaowei Deng, Zhoulian ZhengAbstract:Abstract Fabric Membrane, a typical composite material, is widely applied in building Structures, agricultural facilities, packaging engineering, and aeronautical engineering, etc. However, it may fail subject to large-amplitude vibration induced by impact due to its lightweight and small stiffness properties. Herein, the nonlinear damped vibration of a pretensioned rectangular orthotropic Membrane Structure under impact loading is studied by analytical, numerical and experimental methods. The governing equation is derived based on the von Karman large deflection theory, and the analytical solution is obtained by the Bubnov-Galerkin method and the Krylov-Bogolubov-Mitropolsky (KBM) perturbation method. Meanwhile, the numerical and experimental analysis are carried out for validation of analytical model and good agreement is achieved. Furthermore, parametric study is also performed to find the sensitivity of the design parameters to the vibration response. The results obtained in the paper lay solid foundation for the vibration control and dynamic design of orthotropic Membrane Structures.
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study of dynamic response of orthotropic Membrane Structure under impact load based on multiple scale perturbation method
Latin American Journal of Solids and Structures, 2017Co-Authors: Zhoulian Zheng, Caoyu Liu, Ting ZhangAbstract:THIS PAPER INVESTIGATES THE DYNAMIC RESPONSE OF RECTANGULAR PRESTRESSED Membrane SUBJECTED TO CONCENTRATED IMPACT LOAD BASED ON MULTIPLE SCALE PERTURBATION METHOD. THE GOVERNING EQUATIONS OF MOTION OF NONLINEAR VIBRATION ARE DERIVED BASED ON THE FOPPL LARGE DEFLECTION THEORY, AND UNCOUPLED BY MEANS OF GALERKIN METHOD.BY INTRODUCING DIFFERENT TIME SCALES TO CONSIDER THE PROCESS OF VIBRATION, THE RESULTS OF DYNAMIC RESPONSE ARE OBTAINED BY APPLYING THE MULTIPLE SCALE PERTURBATION METHOD. ADDITIONALLY, THE THEORETICAL RESULTS ARE COMPARED WITH THE EXPERIMENTAL DATA IN LITERATURE TO IDENTIFY THE RELIABILITY OF THEORY MODEL. FURTHERMORE, THE EFFECTS OF PRETENSION FORCE, VELOCITY OF LOAD AND DIMENSION OF Membrane ON THE DYNAMIC RESPONSE OF Membrane ARE DISCUSSED. THE PRESENT WORK STUDIES THE PROBLEM OF THE DYNAMIC RESPONSE OF PRESTRESSED Membrane SUBJECTED TO CONCENTRATED IMPACT LOAD IN DIFFERENT TIME SCALES, AND PROVIDES A MORE ACCURATE THEORETICAL MODEL FOR DESIGN OF Membrane Structure.
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nonlinear damped vibration of pre stressed orthotropic Membrane Structure under impact loading
International Journal of Structural Stability and Dynamics, 2014Co-Authors: Zhoulian Zheng, Xiaoyan Yang, Hua ZhaoAbstract:This paper is concerned with the nonlinear damped forced vibration problem of pre-stressed orthotropic Membrane Structure under impact loading. The governing equations of motion were derived based on the von Karman large deflection theory and D'Alembert's principle, and solved by using the Bubnov–Galerkin method and the Krylov–Bogolubov–Mitropolsky (KBM) perturbation method. The asymptotic analytical solutions of the frequency and lateral displacement of rectangular orthotropic Membrane with fixed edges were obtained. In the computational example, the frequency results were compared and analyzed. Meanwhile, the vibration mode of the Membrane and the displacement and time curves of each feature point on the Membrane surface were analyzed. The results obtained herein provide a simple and convenient approach to calculate the frequency and lateral displacement of the nonlinear forced vibration of rectangular orthotropic Membranes with low viscous damping under impact loading. In addition, the results provide some computational basis for the vibration control and dynamic design of Membrane Structures.
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Aerodynamic Stability Analysis of Geometrically Nonlinear Orthotropic Membrane Structure with Hyperbolic Paraboloid
Journal of Engineering Mechanics, 2011Co-Authors: Zhoulian Zheng, Changjiang Liu, Weiju Song, Jun LongAbstract:This paper studies the aerodynamic stability of a tensioned, geometrically nonlinear orthotropic Membrane Structure with hyperbolic paraboloid. The aerodynamic force acting on the Membrane surface is determined by the potential flow theory in fluid mechanics and the thin airfoil theory in aerodynamics. The interaction governing the equation of wind-Structure is established on the basis of large-amplitude theory and the D’Alembert principle. Then, under the circumstance of single-mode response, the Bubnov-Galerkin approximate method is applied to transform the complicated interaction equation into a system of second-order nonlinear differential equations with constant coefficients. Through judging the stability of the system characteristic equation, the critical velocity of divergence instability is determined. Different parameter analysis shows that the orthotropy and geometrical nonlinearity is significant for preventing destructive aerodynamic instability in Membrane Structures. Compared to the planar model, there is a little inconsistency about the divergence instability regularities in the hyperbolic paraboloid model.
Ahmad Fauzi Ismail - One of the best experts on this subject based on the ideXlab platform.
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a developed asymmetric pvdf hollow fiber Membrane Structure for co2 absorption
International Journal of Greenhouse Gas Control, 2011Co-Authors: Amir Mansourizadeh, Ahmad Fauzi IsmailAbstract:Abstract Carbon dioxide (CO 2 ), the main greenhouse gas, has been associated with global climate change. Therefore, it is important to develop technologies to mitigate this issue. In present study, porous hydrophobic polyvinylidene fluoride (PVDF) hollow fiber Membranes with developed Structure for CO 2 absorption were prepared via a wet spinning process. The prepared Membranes were characterized in terms of morphology examination, gas permeability, critical water entry pressure (CEP w ) and mass transfer resistance. From the morphology examination, the Membrane showed an almost sponge-like Structure with inner skinless layer and ultra-thin outer skin layer. Results of gas permeation test indicated that the Membrane possess very small mean pore size (3.96 nm) with high surface porosity. The CO 2 absorption experiment demonstrated a significant improvement in the CO 2 flux of the prepared PVDF Membrane compared to the commercial porous polytetrafluoroethylene (PTFE) hollow fiber Membrane. At the absorbent flow rate of 200 ml/min, CO 2 flux of the PVDF Membrane (4.10 × 10 −4 mol/m 2 s) was approximately 68% higher than the CO 2 flux of the PTFE Membrane. In addition, the results indicated that an approximate 25% CO 2 flux reduction was gradually occurred at initial 26 h, then the CO 2 flux maintained constant over 140 h of the operation.
Garth L. Nicolson - One of the best experts on this subject based on the ideXlab platform.
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the fluid mosaic model of Membrane Structure still relevant to understanding the Structure function and dynamics of biological Membranes after more than 40 years
Biochimica et Biophysica Acta, 2014Co-Authors: Garth L. NicolsonAbstract:Abstract In 1972 the Fluid—Mosaic Membrane Model of Membrane Structure was proposed based on thermodynamic principals of organization of Membrane lipids and proteins and available evidence of asymmetry and lateral mobility within the Membrane matrix [S. J. Singer and G. L. Nicolson, Science 175 (1972) 720–731]. After over 40 years, this basic model of the cell Membrane remains relevant for describing the basic nano-Structures of a variety of intracellular and cellular Membranes of plant and animal cells and lower forms of life. In the intervening years, however, new information has documented the importance and roles of specialized Membrane domains, such as lipid rafts and protein/glycoprotein complexes, in describing the macroStructure, dynamics and functions of cellular Membranes as well as the roles of Membrane-associated cytoskeletal fences and extracellular matrix Structures in limiting the lateral diffusion and range of motion of Membrane components. These newer data build on the foundation of the original model and add new layers of complexity and hierarchy, but the concepts described in the original model are still applicable today. In updated versions of the model more emphasis has been placed on the mosaic nature of the macroStructure of cellular Membranes where many protein and lipid components are limited in their rotational and lateral motilities in the Membrane plane, especially in their natural states where lipid–lipid, protein–protein and lipid–protein interactions as well as cell–matrix, cell–cell and intracellular Membrane-associated protein and cytoskeletal interactions are important in restraining the lateral motility and range of motion of particular Membrane components. The formation of specialized Membrane domains and the presence of tightly packed integral Membrane protein complexes due to Membrane-associated fences, fenceposts and other Structures are considered very important in describing Membrane dynamics and architecture. These Structures along with Membrane-associated cytoskeletal and extracellular Structures maintain the long-range, non-random mosaic macro-organization of Membranes, while smaller Membrane nano- and submicro-sized domains, such as lipid rafts and protein complexes, are important in maintaining specialized Membrane Structures that are in cooperative dynamic flux in a crowded Membrane plane. This Article is Part of a Special Issue Entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy.
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update of the 1972 singer nicolson fluid mosaic model of Membrane Structure
Discoveries (Craiova Romania), 2013Co-Authors: Garth L. NicolsonAbstract:The Fluid-Mosaic Membrane Model of cell Membrane Structure was based on thermodynamic principals and the available data on component lateral mobility within the Membrane plane [Singer SJ, Nicolson GL. The Fluid Mosaic Model of the Structure of cell Membranes. Science 1972; 175: 720-731]. After more than forty years the model remains relevant for describing the basic nano-scale Structures of a variety of biological Membranes. More recent information, however, has shown the importance of specialized Membrane domains, such as lipid rafts and protein complexes, in describing the macroStructure and dynamics of biological Membranes. In addition, Membrane-associated cytoskeletal Structures and extracellular matrix also play roles in limiting the mobility and range of motion of Membrane components and add new layers of complexity and hierarchy to the original model. An updated Fluid-Mosaic Membrane Model is described, where more emphasis has been placed on the mosaic nature of cellular Membranes where protein and lipid components are more crowded and limited in their movements in the Membrane plane by lipid-lipid, protein-protein and lipid-protein interactions as well as cell-matrix, cellcell and cytoskeletal interactions. These interactions are important in restraining Membrane components and maintaining the unique mosaic organization of cell Membranes into functional, dynamic domains.
David Tee Liang - One of the best experts on this subject based on the ideXlab platform.
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effect of Membrane Structure on mass transfer in the Membrane gas liquid contacting process using microporous pvdf hollow fibers
Journal of Membrane Science, 2006Co-Authors: Supakorn Atchariyawut, Chunsheng Feng, Ratana Jiraratananon, Rong Wang, David Tee LiangAbstract:Abstract In order to gain a better understanding of the Membrane's role in the whole process of mass-transfer in Membrane gas–liquid contacting systems, PVDF microporous hollow fiber Membranes have been fabricated using three different dope solutions containing N -methyl-2-pyrrolidone (NMP) and different additives. The resultant hollow fibers with different Structures were used to make Membrane modules, which were then applied as gas–liquid Membrane contactors for CO 2 absorption in water. The Membranes were characterized and the effect of Membrane Structure on the mass-transfer was analysed accordingly. It was found that the additives used imposed a significant effect on the final Membrane Structure under the same spinning conditions. Compared with distilled water, phosphorous acid and glycerol showed a stronger pore-inducing ability. As a result, the Membrane #1 or #2 made by the dope with phosphorous acid or glycerol as an additive had a larger pore size and a higher value of MWCO. The finger-like pores also occupied a larger portion on the Membranes #1 and #2 than on the Membrane #3, which used distilled water as an additive. Moreover, the Membranes #1 and #2 presented a much wider pore size distribution than the Membrane #3. The different Membrane Structures turned out to affect CO 2 absorption performance when used as contactors. Since the ratio of the Membrane resistance over the overall mass-transfer resistance was increased in the order of #1 2 absorption performance was in the sequence of #1 > #2 > #3. In addition, it was noticed that all the Membranes exhibited considerable Membrane resistances from 22% to 36% though the model system used was pure CO 2 absorption in distilled water. The partial wetting was probably caused by the capillary condensation of water vapour in the Membrane pores instead of water penetration, as the experiment shows that the CO 2 flux of three PVDF Membranes was kept almost unchanged over 15 days of operation. In comparison with a commercial double skin layer PVDF Membrane, it was found that the Membrane with an inner skin-free Structure plus a porous substrate is favourable to be used in the Membrane gas–liquid contacting process.