A topological molecular lattice (TML) is a pair (L, r), where L is a completely distributive lattice and T is a subframe of L. There is an obvious forgetful functor from the category TML of TML’s to the category Loc ...A topological molecular lattice (TML) is a pair (L, r), where L is a completely distributive lattice and T is a subframe of L. There is an obvious forgetful functor from the category TML of TML’s to the category Loc of locales. In this note, it is showed that this forgetful functor has a right adjoint. Then, by this adjunction, a special kind of topological molecular lattices called sober topological molecular lattices is introduced and investigated.展开更多
Most current lattice Boltzmann (LBM) models suffer from the deficiency that their parameters have to be obtained by fitting experimental results. In this paper, we propose a new method that integrates the molecular ...Most current lattice Boltzmann (LBM) models suffer from the deficiency that their parameters have to be obtained by fitting experimental results. In this paper, we propose a new method that integrates the molecular dynamics (MD) simulation and LBM to avoid such defect. The basic idea is to first construct a molecular model based on the actual components of the rock-fluid system, then to compute the interaction force between the rock and the fluid of different densities through the MD simulation. This calculated rock-fluid interaction force, combined with the fluid-fluid force determined from the equation of state, is then used in LBM modeling. Without parameter fitting, this study presents a new systematic approach for pore-scale modeling of multi-phase flow. We have validated this ap- proach by simulating a two-phase separation process and gas-liquid-solid three-phase contact angle. Based on an actual X-ray CT image of a reservoir core, we applied our workflow to calculate the absolute permeability of the core, vapor-liquid H20 relative permeability, and capillary pressure curves.展开更多
High lattice match growth of InAsSb based materials on GaSb substrates is demonstrated. The present results indicate that a stable substrate temperature and the optimal flux ratios are of critical importance in achiev...High lattice match growth of InAsSb based materials on GaSb substrates is demonstrated. The present results indicate that a stable substrate temperature and the optimal flux ratios are of critical importance in achieving a homogeneous InAsSb based material composition throughout the growth period. The quality of these epilayers is assessed using a high-resolution x-ray diffraction and atomic force microscope. The mismatch between the GaSb substrate and InAsSb alloy achieves almost zero, and the rms surface roughness of InAsSb alloy achieves around 1.7A over an area of 28μm × 28μm. At the same time, the mismatches between GaSb and InAs/InAs0.73Sb0.27 superlattices (SLs) achieve approximately 100 arcsec (75 periods) and zero (300 periods), with the surface rms roughnesses of InAs/InAs0.73Sb0.27 SLs around 1.8 A (75 periods) and 2.1A (300 periods) over an area of 20 μm×20 μm, respectively. After fabrication and characterization of the devices, the dynamic resistance of the n-barrier-n InAsSb photodetector near zero bias is of the order of 10^6Ω·cm^2. At 77K, the positive-intrinsic-negative photodetectors are demonstrated in InAsSb and InAs/InAsSb SL (75 periods) materials, exhibiting fifty-percent cutoff wavelengths of 3.8μm and 5.1μm, respectively.展开更多
We investigate the interactions of lattice pbonons with Wannier-Mott exciton, the exciton that has a large radius in two-dimensional molecular lattice, by the method of continuum limit approximation, and obtain that t...We investigate the interactions of lattice pbonons with Wannier-Mott exciton, the exciton that has a large radius in two-dimensional molecular lattice, by the method of continuum limit approximation, and obtain that the self-trapping can also appear in two-dimensional molecular lattice with a harmonic and nonlinear potential. The exciton effect on molecular lattice does not distort the molecular lattice but only makes it localized and the localization can also react, again through phonon coupling, to trap the energy and prevents its dispersion.展开更多
We investigate the interactions of lattice phonons with Frenkel exciton, which has a small radius in a twodimensional discrete molecular lattice, by the virtue of the quasi-discreteness approximation and the method of...We investigate the interactions of lattice phonons with Frenkel exciton, which has a small radius in a twodimensional discrete molecular lattice, by the virtue of the quasi-discreteness approximation and the method of multiplescale, and obtain that the self-trapping can also appear in the two-dimensional discrete molecular lattice with harmonic and nonlinear potential. The excitons' effect on the molecular lattice does not distort it but only causes it to localize which enables it to react again through phonon coupling to trap the energy and prevent its dispersion.展开更多
This article reports recent developments and advances in the simulation of the CO2-formation fluid displacement behaviour at the pore scale of subsurface porous media. Roughly, there are three effective visualization ...This article reports recent developments and advances in the simulation of the CO2-formation fluid displacement behaviour at the pore scale of subsurface porous media. Roughly, there are three effective visualization approaches to detect and observe the CO2-formation fluid displacement mechanism at the micro-scale, namely, magnetic resonance imaging, X-ray computed tomography and fabricated micromodels, but they are not capable of investigating the dis- placement process at the nano-scale. Though a lab-on-chip approach for the direct visualization of the fluid flow behaviour in nanoscale channels has been developed using an advanced epi-fluorescence microscopy method combined with a nanofluidic chip, it is still a qualitative analysis method. The lattice Boltzmann method (LBM) can simulate the CO2 displacement processes in a two-dimensional or three-dimensional (3D) pore structure, but until now, the CO2 displace- ment mechanisms had not been thoroughly investigated and the 3D pore structure of real rock had not been directly taken into account in the simulation of the CO2 displacement process. The status of research on the applications of CO2 displacement to enhance shale gas recovery is also analyzed in this paper. The coupling of molecular dynamics and LBM in tandem is proposed to simulate the CO2-shale gas displacement process based on the 3D digital model of shale obtained from focused ion beams and scanning electron microscopy.展开更多
In [6,11], A theory of pointwise pseudo-quasi-metrics was based on completely distributive lattices. In this paper a product pointwise p.q. metric function is constructed on the product of countably many molecular lat...In [6,11], A theory of pointwise pseudo-quasi-metrics was based on completely distributive lattices. In this paper a product pointwise p.q. metric function is constructed on the product of countably many molecular lattices by distance functions. Hence it is proved that countable product of pointwise pseudo-quasi-metric molecular lattices is pointwise pseudo-quasi-metrizable.展开更多
We study the size dependency of heat conduction in one-dimensional diatomic FPU-β lattices and establish that for low dimensional material,contribution from optical phonons is found more effective to the thermal cond...We study the size dependency of heat conduction in one-dimensional diatomic FPU-β lattices and establish that for low dimensional material,contribution from optical phonons is found more effective to the thermal conductivity and enhance heat transport in the thermodynamic limit N →∞.For the finite size,thermal conductivity of 1D diatomic lattice is found to be lower than 1D monoatomic chain of the same size made up of the constituent particle of the diatomic chain.For the present 1D diatomic chain,obtained value of power divergent exponent of thermal conductivity0.428±0.001 and diffusion exponent 1.2723 lead to the conclusions that increase in the system size,increases the thermal conductivity and existence of anomalous energy diffusion.Existing numerical data supports our findings.展开更多
The lattice thermal conductivity of boron nitride nanoribbon(BNNR) is calculated by using equilibrium molecular dynamics(EMD) simulation method. The Green–Kubo relation derived from linear response theory is used...The lattice thermal conductivity of boron nitride nanoribbon(BNNR) is calculated by using equilibrium molecular dynamics(EMD) simulation method. The Green–Kubo relation derived from linear response theory is used to acquire the thermal conductivity from heat current auto-correlation function(HCACF). HCACF of the selected BNNR system shows a tendency of a very fast decay and then be followed by a very slow decay process,finally,approaching zero approximately within 3 ps. The convergence of lattice thermal conductivity demonstrates that the thermal conductivity of BNNR can be simulated by EMD simulation using several thousands of atoms with periodic boundary conditions. The results show that BNNR exhibit lower thermal conductivity than that of boron nitride(BN) monolayer,which indicates that phonons boundary scatting significantly suppresses the phonons transport in BNNR. Vacancies in BNNR greatly affect the lattice thermal conductivity,in detail,only 1% concentration of vacancies in BNNR induce a 60% reduction of the lattice thermal conductivity at room temperature.展开更多
OMS-2 nanorod catalysts were synthesized by a hydrothermal redox reaction method using Mn SO4(OMS-2-SO4) and Mn(CH3COO)2(OMS-2-AC) as precursors. SO4^2--doped OMS-2-AC catalysts with different SO4^2-concentratio...OMS-2 nanorod catalysts were synthesized by a hydrothermal redox reaction method using Mn SO4(OMS-2-SO4) and Mn(CH3COO)2(OMS-2-AC) as precursors. SO4^2--doped OMS-2-AC catalysts with different SO4^2-concentrations were prepared next by adding(NH4)2SO4solution into OMS-2-AC samples to investigate the effect of the anion SO4^2-on the OMS-2-AC catalyst. All catalysts were then tested for the catalytic oxidation of ethanol. The OMS-2-SO4 catalyst synthesized demonstrated much better activity than OMS-2-AC. The SO4^2-doping greatly influenced the activity of the OMS-2-AC catalyst, with a dramatic promotion of activity for suitable concentration of SO4^2-(SO4/catalyst = 0.5% W/W). The samples were characterized by X-ray diffraction(XRD), field emission scanning electron microscopy(FE-SEM), transmission electron microscopy(TEM), X-ray photoelectron spectroscopy(XPS),inductively coupled plasma optical emission spectroscopy(ICP-OES), NH3-TPD and H2-TPR techniques. The results showed that the presence of a suitable amount of SO4^2-species in the OMS-2-AC catalyst could decrease the Mn–O bond strength and also enhance the lattice oxygen and acid site concentrations, which then effectively promoted the catalytic activity of OMS-2-AC toward ethanol oxidation. Thus it was confirmed that the better catalytic performance of OMS-2-SO4 compared to OMS-2-AC is due to the presence of some residual SO4^2-species in OMS-2-SO4 samples.展开更多
基金973 Programs (2002cb312200) Huo Yingdong Education Foundation and TRAPOYT.
文摘A topological molecular lattice (TML) is a pair (L, r), where L is a completely distributive lattice and T is a subframe of L. There is an obvious forgetful functor from the category TML of TML’s to the category Loc of locales. In this note, it is showed that this forgetful functor has a right adjoint. Then, by this adjunction, a special kind of topological molecular lattices called sober topological molecular lattices is introduced and investigated.
文摘Most current lattice Boltzmann (LBM) models suffer from the deficiency that their parameters have to be obtained by fitting experimental results. In this paper, we propose a new method that integrates the molecular dynamics (MD) simulation and LBM to avoid such defect. The basic idea is to first construct a molecular model based on the actual components of the rock-fluid system, then to compute the interaction force between the rock and the fluid of different densities through the MD simulation. This calculated rock-fluid interaction force, combined with the fluid-fluid force determined from the equation of state, is then used in LBM modeling. Without parameter fitting, this study presents a new systematic approach for pore-scale modeling of multi-phase flow. We have validated this ap- proach by simulating a two-phase separation process and gas-liquid-solid three-phase contact angle. Based on an actual X-ray CT image of a reservoir core, we applied our workflow to calculate the absolute permeability of the core, vapor-liquid H20 relative permeability, and capillary pressure curves.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11474248,61176127,61006085,61274013 and 61306013the Key Program for International S&T Cooperation Projects of China under Grant No 2011DFA62380the Ph.D. Programs Foundation of the Ministry of Education of China under Grant No 20105303120002
文摘High lattice match growth of InAsSb based materials on GaSb substrates is demonstrated. The present results indicate that a stable substrate temperature and the optimal flux ratios are of critical importance in achieving a homogeneous InAsSb based material composition throughout the growth period. The quality of these epilayers is assessed using a high-resolution x-ray diffraction and atomic force microscope. The mismatch between the GaSb substrate and InAsSb alloy achieves almost zero, and the rms surface roughness of InAsSb alloy achieves around 1.7A over an area of 28μm × 28μm. At the same time, the mismatches between GaSb and InAs/InAs0.73Sb0.27 superlattices (SLs) achieve approximately 100 arcsec (75 periods) and zero (300 periods), with the surface rms roughnesses of InAs/InAs0.73Sb0.27 SLs around 1.8 A (75 periods) and 2.1A (300 periods) over an area of 20 μm×20 μm, respectively. After fabrication and characterization of the devices, the dynamic resistance of the n-barrier-n InAsSb photodetector near zero bias is of the order of 10^6Ω·cm^2. At 77K, the positive-intrinsic-negative photodetectors are demonstrated in InAsSb and InAs/InAsSb SL (75 periods) materials, exhibiting fifty-percent cutoff wavelengths of 3.8μm and 5.1μm, respectively.
基金supported by the National Natural Science Foundation of China (Grant No.1057400)the Natural Science Foundation of Heilongjiang Province,China (Grant No.A200506)
文摘We investigate the interactions of lattice pbonons with Wannier-Mott exciton, the exciton that has a large radius in two-dimensional molecular lattice, by the method of continuum limit approximation, and obtain that the self-trapping can also appear in two-dimensional molecular lattice with a harmonic and nonlinear potential. The exciton effect on molecular lattice does not distort the molecular lattice but only makes it localized and the localization can also react, again through phonon coupling, to trap the energy and prevents its dispersion.
基金supported by the National Natural Science Foundation of China (Grant No 1057400)the Natural Science Foundation of Heilongjiang Province of China (Grant No A200506)
文摘We investigate the interactions of lattice phonons with Frenkel exciton, which has a small radius in a twodimensional discrete molecular lattice, by the virtue of the quasi-discreteness approximation and the method of multiplescale, and obtain that the self-trapping can also appear in the two-dimensional discrete molecular lattice with harmonic and nonlinear potential. The excitons' effect on the molecular lattice does not distort it but only causes it to localize which enables it to react again through phonon coupling to trap the energy and prevent its dispersion.
基金The authors gratefully acknowledge the financial support of the National Natural Science Foundation of China (Grant Nos. 51374213 and 51674251), the State Key Research Development Program of China (Grant No. 2016YFC0600705), the National Natural Science Fund for Distinguished Young Scholars of China (Grant No. 51125017), the Fund for Innovative Research and Development Group Program of Jiangsu Province (Grant No. 2014- 27), the Science Fund for Creative Research Groups of the National Natural Science Foundation of China (Grant No. 51421003), and the Priority Academic Program Development of the Jiangsu Higher Education Institutions (PAPD 2014).
文摘This article reports recent developments and advances in the simulation of the CO2-formation fluid displacement behaviour at the pore scale of subsurface porous media. Roughly, there are three effective visualization approaches to detect and observe the CO2-formation fluid displacement mechanism at the micro-scale, namely, magnetic resonance imaging, X-ray computed tomography and fabricated micromodels, but they are not capable of investigating the dis- placement process at the nano-scale. Though a lab-on-chip approach for the direct visualization of the fluid flow behaviour in nanoscale channels has been developed using an advanced epi-fluorescence microscopy method combined with a nanofluidic chip, it is still a qualitative analysis method. The lattice Boltzmann method (LBM) can simulate the CO2 displacement processes in a two-dimensional or three-dimensional (3D) pore structure, but until now, the CO2 displace- ment mechanisms had not been thoroughly investigated and the 3D pore structure of real rock had not been directly taken into account in the simulation of the CO2 displacement process. The status of research on the applications of CO2 displacement to enhance shale gas recovery is also analyzed in this paper. The coupling of molecular dynamics and LBM in tandem is proposed to simulate the CO2-shale gas displacement process based on the 3D digital model of shale obtained from focused ion beams and scanning electron microscopy.
基金Supported by the National Natural Science Foundation of China (19971059)
文摘In [6,11], A theory of pointwise pseudo-quasi-metrics was based on completely distributive lattices. In this paper a product pointwise p.q. metric function is constructed on the product of countably many molecular lattices by distance functions. Hence it is proved that countable product of pointwise pseudo-quasi-metric molecular lattices is pointwise pseudo-quasi-metrizable.
基金Computer facility developed under DST-FIST Level–I programme,Department of Science and Technology,Government of India,New Delhi and financial assistance under DRS-SAP-I from University Grants Commission,New Delhi
文摘We study the size dependency of heat conduction in one-dimensional diatomic FPU-β lattices and establish that for low dimensional material,contribution from optical phonons is found more effective to the thermal conductivity and enhance heat transport in the thermodynamic limit N →∞.For the finite size,thermal conductivity of 1D diatomic lattice is found to be lower than 1D monoatomic chain of the same size made up of the constituent particle of the diatomic chain.For the present 1D diatomic chain,obtained value of power divergent exponent of thermal conductivity0.428±0.001 and diffusion exponent 1.2723 lead to the conclusions that increase in the system size,increases the thermal conductivity and existence of anomalous energy diffusion.Existing numerical data supports our findings.
基金Supported by the Natural Science Foundation of Hubei Province(2014CFB610)the Excellent Young Innovation Team Project of Hubei Province(T201429)
文摘The lattice thermal conductivity of boron nitride nanoribbon(BNNR) is calculated by using equilibrium molecular dynamics(EMD) simulation method. The Green–Kubo relation derived from linear response theory is used to acquire the thermal conductivity from heat current auto-correlation function(HCACF). HCACF of the selected BNNR system shows a tendency of a very fast decay and then be followed by a very slow decay process,finally,approaching zero approximately within 3 ps. The convergence of lattice thermal conductivity demonstrates that the thermal conductivity of BNNR can be simulated by EMD simulation using several thousands of atoms with periodic boundary conditions. The results show that BNNR exhibit lower thermal conductivity than that of boron nitride(BN) monolayer,which indicates that phonons boundary scatting significantly suppresses the phonons transport in BNNR. Vacancies in BNNR greatly affect the lattice thermal conductivity,in detail,only 1% concentration of vacancies in BNNR induce a 60% reduction of the lattice thermal conductivity at room temperature.
基金financially supported by the National Natural Science Foundation of China (No. 21422706)the Program of the Ministry of Science and Technology of China (No. 2012AA062702)
文摘OMS-2 nanorod catalysts were synthesized by a hydrothermal redox reaction method using Mn SO4(OMS-2-SO4) and Mn(CH3COO)2(OMS-2-AC) as precursors. SO4^2--doped OMS-2-AC catalysts with different SO4^2-concentrations were prepared next by adding(NH4)2SO4solution into OMS-2-AC samples to investigate the effect of the anion SO4^2-on the OMS-2-AC catalyst. All catalysts were then tested for the catalytic oxidation of ethanol. The OMS-2-SO4 catalyst synthesized demonstrated much better activity than OMS-2-AC. The SO4^2-doping greatly influenced the activity of the OMS-2-AC catalyst, with a dramatic promotion of activity for suitable concentration of SO4^2-(SO4/catalyst = 0.5% W/W). The samples were characterized by X-ray diffraction(XRD), field emission scanning electron microscopy(FE-SEM), transmission electron microscopy(TEM), X-ray photoelectron spectroscopy(XPS),inductively coupled plasma optical emission spectroscopy(ICP-OES), NH3-TPD and H2-TPR techniques. The results showed that the presence of a suitable amount of SO4^2-species in the OMS-2-AC catalyst could decrease the Mn–O bond strength and also enhance the lattice oxygen and acid site concentrations, which then effectively promoted the catalytic activity of OMS-2-AC toward ethanol oxidation. Thus it was confirmed that the better catalytic performance of OMS-2-SO4 compared to OMS-2-AC is due to the presence of some residual SO4^2-species in OMS-2-SO4 samples.