We propose a new flame index for the transported probability density function(PDF) method. The flame index uses mixing flux projections of Lagrangian particles on mixture fraction and progress variable directions as t...We propose a new flame index for the transported probability density function(PDF) method. The flame index uses mixing flux projections of Lagrangian particles on mixture fraction and progress variable directions as the metrics to identify the combustion mode, with the Burke-Schumann solution as a reference. A priori validation of the flame index is conducted with a series of constructed turbulent partially premixed reactors. It indicates that the proposed flame index is able to identify the combustion mode based on the subgrid mixing information. The flame index is then applied the large eddy simulation/PDF datasets of turbulent partially premixed jet flames. Results show that the flame index separate different combustion modes and extinction correctly. The proposed flame index provides a promising tool to analyze and model the partially premixed flames adaptively.展开更多
In present paper, the non-equilibrium Green function(NEGF) method along with the density functional theory(DFT) are used to investigate the effect of width on transport and electronic properties of armchair graphyne(...In present paper, the non-equilibrium Green function(NEGF) method along with the density functional theory(DFT) are used to investigate the effect of width on transport and electronic properties of armchair graphyne(γ-graphyne) nanoribbons. The results show that all the studied nanoribbons are semiconductor and their band gaps decrease as the widths of nanoribbons increase, which will result in increasing current at a certain voltage. Also our results show the promising application of armchair graphyne nanoribbons in nano-electrical devices.展开更多
Predictive simulation of the combustion process in engine is crucial to understand the complex underlying physicochemical processes, improve engine performance, and reduce pollutant emissions. Key issues such as the p...Predictive simulation of the combustion process in engine is crucial to understand the complex underlying physicochemical processes, improve engine performance, and reduce pollutant emissions. Key issues such as the physical modeling of the interaction between turbulence, chemistry and droplets, and the incorporation of the detailed chemistry in high-fidelity simulations of complex flows remain essential though challenging. This paper reviews the transported probability density function method for turbulent dilute spray flames in the dual-Lagrangian framework that shows potential to address some critical modeling issues. An overview is presented for the contributions made within the last decade or so for the three key ingredients for modeling the interaction between turbulence, chemistry and droplets, i.e., micro-mixing, subgrid dispersion and two-phase coupling. Then, various methods for detailed chemistry acceleration are reviewed to address the issue of high computational cost for its use in multidimensional simulations. Finally, some applications of the dual-Lagrangian method in both laboratory-scale and device-scale configurations are provided to demonstrate its capability as well as deficiency at the current stage. Some open modeling challenges are raised and recommended for further investigation.展开更多
Exploring, designing, and synthesizing novel organic field-effect transistor （OFET） materials have kept an important and hot issue in organic electronics. In the current work, the charge transport properties for 2,5...Exploring, designing, and synthesizing novel organic field-effect transistor （OFET） materials have kept an important and hot issue in organic electronics. In the current work, the charge transport properties for 2,5-di（cyanovinyl）thiophene/furan crystal associating two pentafluorophenyl units linked via the azomethine bond, CTE and CFE have been theoretically investigated by means of density functional theory （DFT） calculations coupled with the incoherent charge-hopping mechanism and the kinetic Monte Carlo simulation. Results show that these two compounds possess remarkably low-lying HOMO （-7.0 eV） and LUMO （-4.0 eV） levels, as well as large electron affinities （〉 3.0 eV）, which indicate their high stability exposed to air as promising OFET materials. However, the ph value at room temperature （T = 300 K） is predicted to be 2.058x10^7 cm26Vl·s-1, and the is as low as 9.834^10-8 cm2-V-l.s-1 for CFT crystal. Meanwhile, these two values are 7.561 x 10-8 and 8.437 x 10-8 cm2.V-I.s-1 for the CFE crystal, respectively. Furthermore, the simulation of angle-dependent mobility in the a-b, a-c, and b-c crystal planes shows that the charge transport in CTE and CFE crystals is remarkably anisotropic, which maybe is helpful for the fabrication of high-performance OFET devices.展开更多
The ocean general circulation model for the earth simulator（OFES） products is applied to estimate the transports of the Mindanao Current（MC） and the Mindanao undercurrent（MUC） and explore the relation between th...The ocean general circulation model for the earth simulator（OFES） products is applied to estimate the transports of the Mindanao Current（MC） and the Mindanao undercurrent（MUC） and explore the relation between them on seasonal scale. In general, the MUC is composed of the lower part of the Southern Pacific Tropical Water（SPTW）and Antarctic Intermediate Water（AAIW）. While the deep northward core below 1 500 m is regarded as a portion of MUC. Both salinity and potential density restrictions become more reasonable to estimate the transports of MC/MUC as the properties of water mass having been taken into consideration. The climatological annual mean transport of MC is（37.4±5.81）×10~6 m^3/s while that of MUC is（23.92±6.47）×10~6 m^3/s integrated between 26.5 σ_θ and 27.7 σ_θ, and（17.53±5.45）×10~6 m^3/s integrated between 26.5 σ_θ and 27.5 σ_θ in the OFES. The variations of MC and MUC have good positive correlation with each other on the seasonal scale： The MC is stronger in spring and weaker in fall, which corresponds well with the MUC, and the correlation coefficient of them is 0.67 in the OFES.The same variations are also appeared in hybrid coordinate ocean model（HYCOM） results. Two sensitive experiments based on HYCOM are conducted to explore the relation between MC and MUC. The MUC（26.5〈σ_θ〈27.7） is strengthening as the MC increases with the enhancement of zonal wind field. It is shown,however, that the main part of the increasement is the deeper northward high potential density water（HPDW）,while the AAIW almost remains stable, SPTW decreases, and vice versa.展开更多
By applying nonequilibrium Green's function formalism combined with first-principles density functional theory, we investigate the electronic transport properties of the dihydroazulene optical molecular switch. Th...By applying nonequilibrium Green's function formalism combined with first-principles density functional theory, we investigate the electronic transport properties of the dihydroazulene optical molecular switch. Three kinds of adsorption sites including the hollow, bridge and top sites are studied. The two forms of this molecule, namely the open form and the closed form, can reversibly switch from each other upon photoexcitation. Their transmission spectra are remarkably distinctive. Theoretical results show that the current of the closed form is always significantly larger than that of the open form for all three adsorption sites, which promises this system as possibly one of the good candidates for optical switches due to its unique advantage, and which may have some potential applications in the future molecular circuit.展开更多
基金sponsored by King Abdullah University of Science and Technology(KAUST)the National Natural Science Foundation of China(Grant No.91841302)。
文摘We propose a new flame index for the transported probability density function(PDF) method. The flame index uses mixing flux projections of Lagrangian particles on mixture fraction and progress variable directions as the metrics to identify the combustion mode, with the Burke-Schumann solution as a reference. A priori validation of the flame index is conducted with a series of constructed turbulent partially premixed reactors. It indicates that the proposed flame index is able to identify the combustion mode based on the subgrid mixing information. The flame index is then applied the large eddy simulation/PDF datasets of turbulent partially premixed jet flames. Results show that the flame index separate different combustion modes and extinction correctly. The proposed flame index provides a promising tool to analyze and model the partially premixed flames adaptively.
文摘In present paper, the non-equilibrium Green function(NEGF) method along with the density functional theory(DFT) are used to investigate the effect of width on transport and electronic properties of armchair graphyne(γ-graphyne) nanoribbons. The results show that all the studied nanoribbons are semiconductor and their band gaps decrease as the widths of nanoribbons increase, which will result in increasing current at a certain voltage. Also our results show the promising application of armchair graphyne nanoribbons in nano-electrical devices.
基金This work was supported by the National Natural Science Foundation of China(Grants 91841302 and 52025062).
文摘Predictive simulation of the combustion process in engine is crucial to understand the complex underlying physicochemical processes, improve engine performance, and reduce pollutant emissions. Key issues such as the physical modeling of the interaction between turbulence, chemistry and droplets, and the incorporation of the detailed chemistry in high-fidelity simulations of complex flows remain essential though challenging. This paper reviews the transported probability density function method for turbulent dilute spray flames in the dual-Lagrangian framework that shows potential to address some critical modeling issues. An overview is presented for the contributions made within the last decade or so for the three key ingredients for modeling the interaction between turbulence, chemistry and droplets, i.e., micro-mixing, subgrid dispersion and two-phase coupling. Then, various methods for detailed chemistry acceleration are reviewed to address the issue of high computational cost for its use in multidimensional simulations. Finally, some applications of the dual-Lagrangian method in both laboratory-scale and device-scale configurations are provided to demonstrate its capability as well as deficiency at the current stage. Some open modeling challenges are raised and recommended for further investigation.
基金supported by the National Natural Science Foundation of China(No.21373132,21173138,21502109)the Doctor Research start foundation of Shaanxi University of Technology(No.SLGKYQD2-13,SLGKYQD2-10,SLGQD14-10)
文摘Exploring, designing, and synthesizing novel organic field-effect transistor （OFET） materials have kept an important and hot issue in organic electronics. In the current work, the charge transport properties for 2,5-di（cyanovinyl）thiophene/furan crystal associating two pentafluorophenyl units linked via the azomethine bond, CTE and CFE have been theoretically investigated by means of density functional theory （DFT） calculations coupled with the incoherent charge-hopping mechanism and the kinetic Monte Carlo simulation. Results show that these two compounds possess remarkably low-lying HOMO （-7.0 eV） and LUMO （-4.0 eV） levels, as well as large electron affinities （〉 3.0 eV）, which indicate their high stability exposed to air as promising OFET materials. However, the ph value at room temperature （T = 300 K） is predicted to be 2.058x10^7 cm26Vl·s-1, and the is as low as 9.834^10-8 cm2-V-l.s-1 for CFT crystal. Meanwhile, these two values are 7.561 x 10-8 and 8.437 x 10-8 cm2.V-I.s-1 for the CFE crystal, respectively. Furthermore, the simulation of angle-dependent mobility in the a-b, a-c, and b-c crystal planes shows that the charge transport in CTE and CFE crystals is remarkably anisotropic, which maybe is helpful for the fabrication of high-performance OFET devices.
基金The program of Global Change and Air-Sea Interaction under contract No.GASI-03-01-01-05the National Basic Research Program of China under contract No.2012CB417404+1 种基金the Research Project of Chinese Ministry of Education under contract No.113041Athe National Natural Science Foundation of China under contract Nos 41276011,41521091 and U1406401
文摘The ocean general circulation model for the earth simulator（OFES） products is applied to estimate the transports of the Mindanao Current（MC） and the Mindanao undercurrent（MUC） and explore the relation between them on seasonal scale. In general, the MUC is composed of the lower part of the Southern Pacific Tropical Water（SPTW）and Antarctic Intermediate Water（AAIW）. While the deep northward core below 1 500 m is regarded as a portion of MUC. Both salinity and potential density restrictions become more reasonable to estimate the transports of MC/MUC as the properties of water mass having been taken into consideration. The climatological annual mean transport of MC is（37.4±5.81）×10~6 m^3/s while that of MUC is（23.92±6.47）×10~6 m^3/s integrated between 26.5 σ_θ and 27.7 σ_θ, and（17.53±5.45）×10~6 m^3/s integrated between 26.5 σ_θ and 27.5 σ_θ in the OFES. The variations of MC and MUC have good positive correlation with each other on the seasonal scale： The MC is stronger in spring and weaker in fall, which corresponds well with the MUC, and the correlation coefficient of them is 0.67 in the OFES.The same variations are also appeared in hybrid coordinate ocean model（HYCOM） results. Two sensitive experiments based on HYCOM are conducted to explore the relation between MC and MUC. The MUC（26.5〈σ_θ〈27.7） is strengthening as the MC increases with the enhancement of zonal wind field. It is shown,however, that the main part of the increasement is the deeper northward high potential density water（HPDW）,while the AAIW almost remains stable, SPTW decreases, and vice versa.
基金supported by the National Natural Science Foundation of China (Grant No. 11004156)the National Basic Research Program of China (Grant No. 2009CB929204)+1 种基金the Education Department Foundation of Shaanxi Province, China (Grant No. 09JK461)the Fundament Research of Xi’an Polytechnic University (Grant No. 09XG09)
文摘By applying nonequilibrium Green's function formalism combined with first-principles density functional theory, we investigate the electronic transport properties of the dihydroazulene optical molecular switch. Three kinds of adsorption sites including the hollow, bridge and top sites are studied. The two forms of this molecule, namely the open form and the closed form, can reversibly switch from each other upon photoexcitation. Their transmission spectra are remarkably distinctive. Theoretical results show that the current of the closed form is always significantly larger than that of the open form for all three adsorption sites, which promises this system as possibly one of the good candidates for optical switches due to its unique advantage, and which may have some potential applications in the future molecular circuit.
