A Lagrangian-based flame index for the transported probability density function method

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.

Theoretical Investigation on the Charge Transport Properties of 2,5-Di(cyanovinyl)-thiophene/furan with the Kinetic Monte Carlo Method

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.

The relation between the Mindanao Current and Mindanao Undercurrent on seasonal scale

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.

Theoretical investigations of transport properties of organic solvents in cation-functionalized graphene oxide membranes： Implications for drug delivery

We perform detailed quantum chemical calculations to elucidate the origin and mechanism of the selective permeability of alkali and alkaline earth cation- decorated graphene oxide （M-GO） membranes to organic solvents. The results show that the selectivity is associated mainly with the transport properties of solvents in the membranes, which depends on two regions of the flow path： the sp3 C-O matrix of the GO sheets and the cation at the center of the hexagon rather than the sp~ region. According to the delocalization of ~ states in sp2 regions, we propose a design guide for high-quality M-GO membranes. The solvent-cation interaction essentially causes directional transport of molecules in the M-GO membranes under the transmembrane pressure, indicating a site-to-site mech- anism. The solvent-sp3 C-O matrix interaction may inhibit molecular transport between two fixed cations by consuming energy. The competition between energy consumption by the solvent-cation interaction and energy expenditure by the solvent-sp3 C-O matrix interaction leads to various transport properties of solvents and thus allows for the selective permeability of the M-GO membranes. Findings from the study are helpful for the future design of multifunctional M-GO macro-membranes as cost-effective solution nanofilters in chemical, biological, and medical applications

Review of Lagrangian stochastic models for turbulent combustion

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.

Electrical contacts in monolayer blue phosphorene devices

Semiconducting monolayer （ML） blue phosphorene （BlueP） shares similar stability with ML black phosphorene （BP）, and it has recently been grown on an Au surface. Potential ML BlueP devices often require direct contact with metal to enable the injection of carriers. Using ab initio electronic structure calculations and quantum transport simulations, for the first time, we perform a systematic study of the interfacial properties of ML BlueP in contact with metals spanning a wide work function range in a field effect transistor （FET） configuration. ML BlueP has undergone metallization owing to strong interaction with five metals. There is a strong Fermi level pinning （FLP） in the ML BlueP FETs due to the metal-induced gap states （MIGS） with a pinning factor of 0.42. ML BlueP forms n-type Schottky contact with Sc, Ag, and Pt electrodes with electron Schottky barrier heights （SBHs） of 0.22, 0.22, and 0.80 eV, respectively, and p-type Schottky contact with Au and Pd electrodes with hole SBHs of 0.61 and 0.79 eV, respectively. The MIGS are eliminated by inserting graphene between ML BlueP and the metal electrode, accompanied by a transition from a strong FLP to a weak FLP. Our study not only provides insight into the ML BlueP-metal interfaces, but also helps in the design of ML BlueP devices.