The Experts below are selected from a list of 35619 Experts worldwide ranked by ideXlab platform
Daijiro Yoshioka - One of the best experts on this subject based on the ideXlab platform.
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ground state Phase diagram of 2d electrons in a high landau level a density matrix renormalization group study
Physical Review Letters, 2001Co-Authors: Naokazu Shibata, Daijiro YoshiokaAbstract:The ground-state Phase diagram of 2D electrons in a high Landau level (index N=2 ) is studied by the density-matrix renormalization group method. Pair correlation functions are systematically calculated for various filling factors from {nu}=1/8 to 1/2 . It is shown that the ground-state Phase diagram consists of three different charge density wave states called stripe Phase, Bubble Phase, and Wigner crystal. The boundary between the stripe and the Bubble Phases is determined to be {nu}{sup s-b}{sub c}{similar_to}0.38 , and that for the Bubble Phase and Wigner crystal is {nu}{sup b-W}{sub c}{similar_to}0.24 . Each transition is of first order.
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ground state Phase diagram of 2d electrons in a high landau level a density matrix renormalization group study
Physical Review Letters, 2001Co-Authors: Naokazu Shibata, Daijiro YoshiokaAbstract:The ground-state Phase diagram of 2D electrons in a high Landau level (index $N\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2$) is studied by the density-matrix renormalization group method. Pair correlation functions are systematically calculated for various filling factors from $\ensuremath{\nu}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1/8$ to $1/2$. It is shown that the ground-state Phase diagram consists of three different charge density wave states called stripe Phase, Bubble Phase, and Wigner crystal. The boundary between the stripe and the Bubble Phases is determined to be ${\ensuremath{\nu}}_{c}^{\mathrm{s}\mathrm{\ensuremath{-}}\mathrm{b}}\ensuremath{\sim}0.38$, and that for the Bubble Phase and Wigner crystal is ${\ensuremath{\nu}}_{c}^{\mathrm{b}\mathrm{\ensuremath{-}}\mathrm{W}}\ensuremath{\sim}0.24$. Each transition is of first order.
Naokazu Shibata - One of the best experts on this subject based on the ideXlab platform.
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ground state Phase diagram of 2d electrons in a high landau level a density matrix renormalization group study
Physical Review Letters, 2001Co-Authors: Naokazu Shibata, Daijiro YoshiokaAbstract:The ground-state Phase diagram of 2D electrons in a high Landau level (index N=2 ) is studied by the density-matrix renormalization group method. Pair correlation functions are systematically calculated for various filling factors from {nu}=1/8 to 1/2 . It is shown that the ground-state Phase diagram consists of three different charge density wave states called stripe Phase, Bubble Phase, and Wigner crystal. The boundary between the stripe and the Bubble Phases is determined to be {nu}{sup s-b}{sub c}{similar_to}0.38 , and that for the Bubble Phase and Wigner crystal is {nu}{sup b-W}{sub c}{similar_to}0.24 . Each transition is of first order.
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ground state Phase diagram of 2d electrons in a high landau level a density matrix renormalization group study
Physical Review Letters, 2001Co-Authors: Naokazu Shibata, Daijiro YoshiokaAbstract:The ground-state Phase diagram of 2D electrons in a high Landau level (index $N\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2$) is studied by the density-matrix renormalization group method. Pair correlation functions are systematically calculated for various filling factors from $\ensuremath{\nu}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1/8$ to $1/2$. It is shown that the ground-state Phase diagram consists of three different charge density wave states called stripe Phase, Bubble Phase, and Wigner crystal. The boundary between the stripe and the Bubble Phases is determined to be ${\ensuremath{\nu}}_{c}^{\mathrm{s}\mathrm{\ensuremath{-}}\mathrm{b}}\ensuremath{\sim}0.38$, and that for the Bubble Phase and Wigner crystal is ${\ensuremath{\nu}}_{c}^{\mathrm{b}\mathrm{\ensuremath{-}}\mathrm{W}}\ensuremath{\sim}0.24$. Each transition is of first order.
Dongke Zhang - One of the best experts on this subject based on the ideXlab platform.
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mathematical modelling of a bubbling fluidised bed coal gasifier and the significance of net flow
Fuel, 1998Co-Authors: Dongke Zhang, Hongming Yan, Craig HeidenreichAbstract:Abstract An isothermal model, incorporating the two-Phase theory, has been developed to evaluate the performance of a bubbling fluidised-bed coal gasifier. A distinctive feature of this model is the consideration of a net flow term from the emulsion Phase to the Bubble Phase in the conservation equations. Simulations with consideration of the net flow term indicate that the overall results compare favourably with available experimental data from an industrial fluidised-bed gasifier reported in the literature. The net flow is significant, in the range 71–87% relative to the feed gas rate, strongly depending on the coal rank, heterogeneous reaction rates and volatile matter released in the bed. The higher the coal rank, the lower the net flow and total excess gas flow. The large volume of net flow generated can significantly change the fluidisation conditions in the bed and thus alter the reaction rates and mass transfer properties. Simulations without the net flow deviate significantly from the experimental results.
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the significance of net flow terms in the conservation equations for fluidised bed coal gasifier modelling
Chemeca 96: Excellence in Chemical Engineering; 24th Australian and New Zealand Chemical Engineering Conference and Exhibition; Proceedings, 1996Co-Authors: Hongming Yan, Craig Heidenreich, Dongke ZhangAbstract:An isothermal mathematical model, incorporating the two-Phase theory, has been developed to evaluate performance of a bubbling fluidised-bed coal gasifier. One distinctive feature of this model is the consideration of a net flow term from the emulsion Phase to the Bubble Phase in the conservation equations. Simulations with consideration of the net flow indicate that the results compare favourably with available experimental data from the Winkler process in the literature. The higher the coal rank, the lower the net flow and total excess gas flow. Total net generation of gas in the bed is significant and up-to 147 % depending on coal rank, reaction rate and volatile released in the bed. The contribution of volatile products to the net flow is significant and decreases with an increase in coal rank. Simulations without the net flow deviate significantly from experimental results.
Qingxia Liu - One of the best experts on this subject based on the ideXlab platform.
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flow pattern transition and coal beneficiation in gas solid fluidized bed with novel secondary distributor
Advanced Powder Technology, 2018Co-Authors: Xuchen Fan, Yuemin Zhao, Chenlong Duan, Chenyang Zhou, Qingxia LiuAbstract:Abstract Gas solid fluidized bed (GSFB) is an effective method of dry coal separation. In this study, porous sponge was introduced into a typical gas solid fluidized bed as secondary air distribution layer (PSFB) to stabilize the fluidized bed layer. The difference between PSFB and GSFB in flow pattern transition process was studied. Compared with GSFB, the minimum gas velocity and bed density fluctuation decreased while bed expansion ratio increased in PSFB. Furthermore, the distribution of Bubble Phase and emulsion Phase were more homogeneous in PSFB. Under the operational conditions, the results of coal preparation in a PSFB showed that the ash content of clean coal was 10.25% .The probable error (E) was 0.095 g/cm3, indicating that PSFB could provide a novel way for a good performance of dry coking coal beneficiation.
Navid Mostoufi - One of the best experts on this subject based on the ideXlab platform.
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dynamic modeling of gas Phase propylene homopolymerization in fluidized bed reactors
Chemical Engineering Science, 2011Co-Authors: Ahmad Shamiri, Navid Mostoufi, Mohamed Azlan Hussain, Farouq S Mjalli, Mohammad Saleh ShafeeyanAbstract:A new model with comprehensive kinetics for propylene homopolymerization in fluidized bed reactors was developed to investigate the effect of mixing, operating conditions, kinetic and hydrodynamic parameters on the reactor performance as well as polymer properties. Presence of the particles in the Bubbles and the excess gas in the emulsion Phase was considered to improve the two-Phase model, thus, considering the polymerization reaction to take place in both the Bubble and emulsion Phases. It was shown that in the practical range of superficial gas velocity and catalyst feed rate, the ratio of produced polymer in the Bubble Phase to the total production rate is roughly between 10% and 13%, which is a substantial amount and cannot be ignored. Simulation studies were carried out to compare the results of the improved two-Phase, conventional well-mixed and constant Bubble size models. The improved two-Phase and well mixed models predicted a narrower and safer window at the same running conditions compared with the constant Bubble size model. The improved two-Phase model showed close dynamic behavior to the conventional models at the beginning of polymerization, but starts to diverge with the evolution of time.
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kinetic modeling of propylene homopolymerization in a gas Phase fluidized bed reactor
Chemical Engineering Journal, 2010Co-Authors: Ahmad Shamiri, Mohamed Azlan Hussain, Farouq S Mjalli, Navid MostoufiAbstract:A comprehensive mechanistic model describing gas-Phase propylene polymerization is developed. The kinetics of polymerization is based on a multiple active site for Ziegler–Natta catalyst. The model considers the polymerization reaction to take place in both Bubble and emulsion Phases. The developed model was used to predict polymer production rate, number and weight average molecular weights, polydispersity index (PDI) and melt flow index (MFI). Results showed that by increasing the superficial gas velocity from 0.1 to 0.7 m/s the proportion of the polymer produced in the Bubble Phase increases from 7.92% to 13.14% which highlights the importance of considering the existence of catalyst in the Bubble Phase. Comparing the developed model with published models of the same reactor revealed that the polymer productivity will be higher using the new model at high catalyst feed rate.
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characterization of dynamic gas solid distribution in fluidized beds
Chemical Engineering Journal, 2000Co-Authors: Navid Mostoufi, Jamal ChaoukiAbstract:Abstract A probability distribution model of the local voidage was proposed to describe and simulate dynamic gas–solid distribution in the bubbling and turbulent fluidized bed reactors. Experiments were carried out in an air-fluidized bed. The bed materials were FCC particles (Geldart A) and irregular sand particles (Geldart B). A cross-optical fiber probe was employed to measure dynamic voidage. The minimum probability method was introduced to identify the division between the emulsion Phase and the Bubble Phase. The statistical analysis indicated that the two particle types employed have extremely different dynamic behaviors corresponding to different gas–solid distributions and the interaction between the Bubble and emulsion Phases. For the FCC particles, the voidage of the emulsion Phase is very close to that at the minimum fluidization with little effect from the formation and motion of Bubbles in bubbling regime, and deviates a little from emf in turbulent regime. For the sand particles, the voidage of the emulsion Phase differs far from that at the minimum fluidization, and the Bubble Phase gradually becomes more dilute from bubbling to turbulent regime. However, for both particles the dynamic voidage fluctuations in the emulsion Phase and the Bubble Phase followed beta distribution under various operating conditions. The probability density functions of the local voidage from emf to 1 showed the continuous double-peak phenomena, one peak for the emulsion Phase and another for the Bubble Phase, and evolved with changing operating conditions and bed position. A particular distribution, called coupled beta distribution, was developed to describe and simulate such probability density function with double peaks and its complex evolution from bubbling to turbulent regime. The quantification of the probability density function then statistically introduced the spatiotemporal two-Phase flow structure.
