This study presents the interaction between konjac glucanmannan（KGM） and cationic surfactant dodecyl trimethylammonium chloride（DTAC） to provide theoretical guidance and prediction for the experimental design and ...This study presents the interaction between konjac glucanmannan（KGM） and cationic surfactant dodecyl trimethylammonium chloride（DTAC） to provide theoretical guidance and prediction for the experimental design and application of this composite system. Dissipative particle dynamics（DPD） method was used to simulate the interaction between KGM and the cationic surfactant. Influences of concentration, temperature and shear process on the structure and properties of aggregates were mainly examined. The results revealed that the density peak increased with the increase of concentration of KGM. With increasing the temperature, density peak moved to the right and increased, and then decreased when the temperature rose to a certain value. The density peak moved to the right at the low shear rate while decreased at the high one. During simulation, the high viscosity related to the low diffusion rate, which made it difficult to form a large continuous phase.展开更多
In this study, the flow characteristics of Geldart A particles in a bobbling fluidized bed with and without perforated plates were simulated by the multiphase particle-in-cell （MP-PlC）-based Eolerian-Lagrangian meth...In this study, the flow characteristics of Geldart A particles in a bobbling fluidized bed with and without perforated plates were simulated by the multiphase particle-in-cell （MP-PlC）-based Eolerian-Lagrangian method. A modified structure-based drag model was developed based on our previous work. Other drag models including the Parker and Wen-Yo-Ergon drag models were also employed to investigate the effects of drag models on the simulation results. Although the modified structure-based drag model better predicts the gas-solid flow dynamics of a baffle-free bubbling fluidized bed in comparison with the experimental data, none of these drag models predict the gas-solid flow in a baffled bobbling floidized bed sufficiently well because of the treatment of baffles in the Barracuda software. To improve the simulation accuracy, future versions of Barracuda should address the challenges of incorporating the bed height and the baffles.展开更多
A series of completely sealed standing-wave (SW) accelerator guides was developed and installed on 3,4, 6, 9 and 14 MeV home-made electron linacs for medical and industrial uses. In the development of these SW guides,...A series of completely sealed standing-wave (SW) accelerator guides was developed and installed on 3,4, 6, 9 and 14 MeV home-made electron linacs for medical and industrial uses. In the development of these SW guides, various subjects, including particle dynamics, microwave properties etc, were studied. The fsctors influencing the transverse motion were considered analytically and using a simulation code, TRSV. The problem of electron backbombardment in SW linac was analyzed by a 3-dimensional trace code, SB. Simultaneously decreasing the length of the first cavity and the injection voltage can reduced the electron backbombarding power. The code PPDW based on equivalent circuit theory was developed to analyze many microwave characteristics of arbitrarily composed coupled cavity chains. This research contributed to the successful development of the 3, 4, 6, 9 and 14MeV SW accelerator guides. For example, in the recently developed 14MeV SW guide, the beam passes smoothly through a 1.45 m long guide with a beamhole (diameter of 7 mm) without using a focusing solenoid.展开更多
Layered double hydroxides （LDHs） are effective molecular carriers in cytological research, gene therapy, and transgenic applications. Herein, we investigated the internalization behavior of the LDH-DNA biocon- jugat...Layered double hydroxides （LDHs） are effective molecular carriers in cytological research, gene therapy, and transgenic applications. Herein, we investigated the internalization behavior of the LDH-DNA biocon- jugates via a microscopic approach and analyzed the internalization pathway by dissipative particle dynamics （DPD） simulations. We experimentally found that LDH can efficiently carry DNA into the nucleus of cell in BY-2 suspension cells. Furthermore, atomic force microscopy and X-ray diffraction anal- ysis demonstrated that the LDH-DNA bioconjugates mainly exist as a DNA-LDH-DNA sandwich complex, while the LDH-DNA-LDH sandwich complex and DNA-LDH complex cannot be excluded. The DPD simu- lations further indicated that only the DNA-LDH-DNA sandwich structure could penetrate the plasma membrane （PM）, while PM is impermeable to the LDH-DNA-LDH sandwich complex and the DNA-LDH complex. This work provides novel perspective for understanding the membrane penetration mechanism of LDH nano-sheets and new insights into the design of novel molecular delivery systems.展开更多
In this paper,the mechanisms of particle movement on an electric curtain are examined.Intermittent bursts in which particles leaping from a surface of an electric curtain are demonstrated both by numerical simulation ...In this paper,the mechanisms of particle movement on an electric curtain are examined.Intermittent bursts in which particles leaping from a surface of an electric curtain are demonstrated both by numerical simulation and experimental observation.The hopping and surfing modes during particle removal are shown to depend on the particle electric charge and its initial position.The particles initially located on the top of electrode have a large electric charge tend to assume a hopping mode.Transverse movement of the particle initially located between the electrodes is analyzed,and the particle traps along the electric curtain surface are also observed.展开更多
A cold flow model of an 8 MW dual fluidized bed （DFB） system is simulated using the commercial compu- tational particle fluid dynamics （CPFD） software package Barracuda. The DFB system comprises a bubbling bed con...A cold flow model of an 8 MW dual fluidized bed （DFB） system is simulated using the commercial compu- tational particle fluid dynamics （CPFD） software package Barracuda. The DFB system comprises a bubbling bed connected to a fast fluidized bed with the bed material circulating between them. As the hydrodynam- ics in hot DFB plants are complex because of high temperatures and many chemical reaction processes, cold flow models are used. Performing numerical simulations of cold flows enables a focus on the hydro- dynamics as the chemistry and heat and mass transfer processes can be put aside. The drag law has a major influence on the hydrodynamics, and therefore its influence on pressure, particle distribution, and bed material recirculation rate is calculated using Barracuda and its results are compared with experimental results. The drag laws used were energy-minimization multiscale （EMMS）, Ganser, Turton-Levenspiel, and a combination of Wen-Yu]Ergun. Eleven operating points were chosen for that study and each was calculated with the aforementioned drag laws. The EMMS drag law best predicted the pressure and dis- tribution of the bed material in the different parts of the DFB system. For predicting the bed material recirculation rate, the Ganser drag law showed the best results. However, the drag laws often were not able to predict the experimentally found trends of the bed material recirculation rate. Indeed, the drag law significantly influences the hydrodynamic outcomes in a DFB system and must be chosen carefully to obtain meaningful simulation results. More research may enable recommendations as to which drag law is useful in simulations ofa DFB system with CPFD.展开更多
Rectification phenomena and the phase locking in a two-dimensional overdamped Frenkel-Kontorova model with a graphite periodic substrate were studied. The presence of dc and ac forces in the longitudinal direction cau...Rectification phenomena and the phase locking in a two-dimensional overdamped Frenkel-Kontorova model with a graphite periodic substrate were studied. The presence of dc and ac forces in the longitudinal direction causes the appearance of dynamicalmode locking and the steps in the response function of the system. On the other hand, the presence of an ac force in the transverse direction causes the appearance of rectification,even though there is no net dc force in the transverse direction. It is found that whereas the longitudinal velocity increases in a series of steps, rectification in the transverse direction can occur only between two neighbor steps. The amplitude and phase of the external ac driving force affect the depinning force,rectification of the system and particles trajectories.展开更多
基金supported by the National Natural Science Foundation of China(31471704 and 31271837)
文摘This study presents the interaction between konjac glucanmannan（KGM） and cationic surfactant dodecyl trimethylammonium chloride（DTAC） to provide theoretical guidance and prediction for the experimental design and application of this composite system. Dissipative particle dynamics（DPD） method was used to simulate the interaction between KGM and the cationic surfactant. Influences of concentration, temperature and shear process on the structure and properties of aggregates were mainly examined. The results revealed that the density peak increased with the increase of concentration of KGM. With increasing the temperature, density peak moved to the right and increased, and then decreased when the temperature rose to a certain value. The density peak moved to the right at the low shear rate while decreased at the high one. During simulation, the high viscosity related to the low diffusion rate, which made it difficult to form a large continuous phase.
文摘In this study, the flow characteristics of Geldart A particles in a bobbling fluidized bed with and without perforated plates were simulated by the multiphase particle-in-cell （MP-PlC）-based Eolerian-Lagrangian method. A modified structure-based drag model was developed based on our previous work. Other drag models including the Parker and Wen-Yo-Ergon drag models were also employed to investigate the effects of drag models on the simulation results. Although the modified structure-based drag model better predicts the gas-solid flow dynamics of a baffle-free bubbling fluidized bed in comparison with the experimental data, none of these drag models predict the gas-solid flow in a baffled bobbling floidized bed sufficiently well because of the treatment of baffles in the Barracuda software. To improve the simulation accuracy, future versions of Barracuda should address the challenges of incorporating the bed height and the baffles.
文摘A series of completely sealed standing-wave (SW) accelerator guides was developed and installed on 3,4, 6, 9 and 14 MeV home-made electron linacs for medical and industrial uses. In the development of these SW guides, various subjects, including particle dynamics, microwave properties etc, were studied. The fsctors influencing the transverse motion were considered analytically and using a simulation code, TRSV. The problem of electron backbombardment in SW linac was analyzed by a 3-dimensional trace code, SB. Simultaneously decreasing the length of the first cavity and the injection voltage can reduced the electron backbombarding power. The code PPDW based on equivalent circuit theory was developed to analyze many microwave characteristics of arbitrarily composed coupled cavity chains. This research contributed to the successful development of the 3, 4, 6, 9 and 14MeV SW accelerator guides. For example, in the recently developed 14MeV SW guide, the beam passes smoothly through a 1.45 m long guide with a beamhole (diameter of 7 mm) without using a focusing solenoid.
基金supported by the Fundamental Research Funds for the Central Universities (2016JX01, BLX2015-01)the National Natural Science Foundation of China (31671489, 31601149 and 31271433)+2 种基金the Beijing Nova Programme (Z131109000413013)the Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fundthe Chemical Grid Program and Excellent Talent of Beijing University of Chemical Technology
文摘Layered double hydroxides （LDHs） are effective molecular carriers in cytological research, gene therapy, and transgenic applications. Herein, we investigated the internalization behavior of the LDH-DNA biocon- jugates via a microscopic approach and analyzed the internalization pathway by dissipative particle dynamics （DPD） simulations. We experimentally found that LDH can efficiently carry DNA into the nucleus of cell in BY-2 suspension cells. Furthermore, atomic force microscopy and X-ray diffraction anal- ysis demonstrated that the LDH-DNA bioconjugates mainly exist as a DNA-LDH-DNA sandwich complex, while the LDH-DNA-LDH sandwich complex and DNA-LDH complex cannot be excluded. The DPD simu- lations further indicated that only the DNA-LDH-DNA sandwich structure could penetrate the plasma membrane （PM）, while PM is impermeable to the LDH-DNA-LDH sandwich complex and the DNA-LDH complex. This work provides novel perspective for understanding the membrane penetration mechanism of LDH nano-sheets and new insights into the design of novel molecular delivery systems.
基金supported by the National Natural Science Foundation of China (Grant No.11002023)the Doctoral Fund of Ministry of Education of China (Grant No. 20091101120004) Beijing Institute of Technology Science Foundation (Grant No. 20090142011)
文摘In this paper,the mechanisms of particle movement on an electric curtain are examined.Intermittent bursts in which particles leaping from a surface of an electric curtain are demonstrated both by numerical simulation and experimental observation.The hopping and surfing modes during particle removal are shown to depend on the particle electric charge and its initial position.The particles initially located on the top of electrode have a large electric charge tend to assume a hopping mode.Transverse movement of the particle initially located between the electrodes is analyzed,and the particle traps along the electric curtain surface are also observed.
文摘A cold flow model of an 8 MW dual fluidized bed （DFB） system is simulated using the commercial compu- tational particle fluid dynamics （CPFD） software package Barracuda. The DFB system comprises a bubbling bed connected to a fast fluidized bed with the bed material circulating between them. As the hydrodynam- ics in hot DFB plants are complex because of high temperatures and many chemical reaction processes, cold flow models are used. Performing numerical simulations of cold flows enables a focus on the hydro- dynamics as the chemistry and heat and mass transfer processes can be put aside. The drag law has a major influence on the hydrodynamics, and therefore its influence on pressure, particle distribution, and bed material recirculation rate is calculated using Barracuda and its results are compared with experimental results. The drag laws used were energy-minimization multiscale （EMMS）, Ganser, Turton-Levenspiel, and a combination of Wen-Yu]Ergun. Eleven operating points were chosen for that study and each was calculated with the aforementioned drag laws. The EMMS drag law best predicted the pressure and dis- tribution of the bed material in the different parts of the DFB system. For predicting the bed material recirculation rate, the Ganser drag law showed the best results. However, the drag laws often were not able to predict the experimentally found trends of the bed material recirculation rate. Indeed, the drag law significantly influences the hydrodynamic outcomes in a DFB system and must be chosen carefully to obtain meaningful simulation results. More research may enable recommendations as to which drag law is useful in simulations ofa DFB system with CPFD.
文摘Rectification phenomena and the phase locking in a two-dimensional overdamped Frenkel-Kontorova model with a graphite periodic substrate were studied. The presence of dc and ac forces in the longitudinal direction causes the appearance of dynamicalmode locking and the steps in the response function of the system. On the other hand, the presence of an ac force in the transverse direction causes the appearance of rectification,even though there is no net dc force in the transverse direction. It is found that whereas the longitudinal velocity increases in a series of steps, rectification in the transverse direction can occur only between two neighbor steps. The amplitude and phase of the external ac driving force affect the depinning force,rectification of the system and particles trajectories.
