Rarefied gas dynamics: fundamentals, simulations and micro flows

Mesoscopic Fano effect modulated by Rashba spin-orbit coupling and external magnetic field

By employing non-equilibrium Green's function method, the mesoscopic Fano effect modulated by Rashba spin-orbit (SO) coupling and external magnetic field has been elucidated for electron transport through a hybrid system composed of a quantum dot (QD) and an Aharonov-Bohm (AB) ring. The results show that the orientation of the Fano line shape is modulated by the Rashba spin-orbit interaction k(R)L variation, which reveals that the Fano parameter q will be extended to a complex number, although the system maintains time-reversal symmetry (TRS) under the Rashba SO interaction. Furthermore, it is shown that the modulation of the external magnetic field, which is applied not only inside the frame, but also on the QD, leads to the Fano resonance split due to Zeeman effect, which indicates that the hybrid is an ideal candidate for the spin readout device. (C) 2007 Elsevier B.V All rights reserved.

Quantum transport from the perspective of quantum open systems

By viewing the non-equilibrium transport setup as a quantum open system, we propose a reduced-density-matrix based quantum transport formalism. At the level of self-consistent Born approximation, it can precisely account for the correlation between tunneling and the system internal many-body interaction, leading to certain novel behavior such as the non-equilibrium Kondo effect. It also opens a new way to construct time-dependent density functional theory for transport through large-scale complex systems. (c) 2006 Elsevier B.V. All rights reserved.

Theoretical Analysis of Gain and Threshold Current Density for Long Wavelength GaAs-Based Quantum-Dot Lasers

Quantum dot gain spectra based on harmonic oscillator model are calculated including and excluding excitons. The effects of non-equilibrium distributions are considered at low temperatures. The variations of threshold current density in a wide temperature range are analyzed and the negative characteristic temperature and oscillatory characteristic temperature appearing in that temperature range are discussed. Also,the improvement of quantum dot lasers＇ performance is investigated through vertical stacking and p-type doping and the optimal dot density, which corresponds to minimal threshold current density,is calculated.

The generalized second law of thermodynamics in generalized gravity theories

We investigate the generalized second law of thermodynamics (GSL) in generalized theories of gravity. We examine the total entropy evolution with time including the horizon entropy, the non-equilibrium entropy production, and the entropy of all matter, field and energy components. We derive a universal condition to protect the generalized second law and study its validity in different gravity theories. In Einstein gravity (even in the phantom-dominated universe with a Schwarzschild black hole), Lovelock gravity and braneworld gravity, we show that the condition to keep the GSL can always be satisfied. In f ( R) gravity and scalar-tensor gravity, the condition to protect the GSL can also hold because the temperature should be positive, gravity is always attractive and the effective Newton constant should be an approximate constant satisfying the experimental bounds.

东北亚构造-盆地演化及油气资源控制作用

The oil and gas potential of Northeast Asia is enormous, but the degree of exploration is very low in Northeast Asia (the degree is below 3%-10%).The reasons are as follows: First, it is relatively difficult to study the oil and gas bearing basins(OGB), which are of multiple types, in different tectonic settings, with complex geologic frameworks and with long-term geologic evolution. Secondly, because of the non-equilibrium in development of economy and regional market, application of theories and techniques and the research levels in different countries, the conclusions are not conformable, and even contradictory. Thirdly, most of the former researches were limited to one territory or one basin, and lack of systematical and in-depth study on geotectonic evolution, classification of basins, and the evaluation of hydrocarbon resources. In this thesis, integrated study of the regional tectonic feature and basin features of Northeast Asia was done, to understand the basin evolution history and the controlling action on oil and gas. Then, new conclusions are and exploration proposals are as following: 1. Geotectonic evolution in Northeast Asia: The main structural motion system in Paleozoic Era was longitudinal, and in Meso-cenozoic was latitudinal with the Pacific Ocean. The whole evolution history was just the one of pulling-apart, cutting-out, underthrusting and collision of the Central Asia- Mongolia Ocean and the Pacific Ocean. 2. The evolution characteristics of basins in Northeast Asia: mainly developed from longitudinal paste-up, collision and relaxation rifting motion in Paleozoic-Early Mesozoic Era and from underthrust, accretion, and receding of subducted zone of the Pacific Ocean in Late Mesozoic Era-Cenozoic Era. 3. The research in basin classification of Northeast Asia: According to geotectonic system, the basins can be classified into three types: intracratonic, pericratonic and active zone basin. And they can be further classified into 18 different types according to genetic mechanism and dynamic features. 4. The master control factors of oil and gas accumulation in Northeast Asia: high quality cap-rock for craton and pericrationic basin, the effective source rock and high quality cap-rock for Mesozoic rifted basins, intra-arc, fore-arc and back-arc basins. Graded exploration potential of oil and gas for basin in Northeast Asia according to 7 factor, hereby, divided the oil and gas potential of basins into 5 levels. 5. Evaluation of hydrocarbon resources: The difference of resource potential among these basins is huge in Northeast Asia. The evaluation of Mesozoic rifted basin and Pacific Ocean basin showed that the large scale rifted basin and retroarc basin(including backarc marginal sea basin) have great resource potential. 6. The writer believes that the next step should pay more attention to the evaluation of petroleum resource in Far East part of Russia and trace them. On the other hand, according to integrated analysis of oil/gas resource potential and the operation difficulty in this area, suggests that East-Siberia basin, East-Gobi-Tamchag basin, Sakhalin basin, North-Okhotck basin, West-Kamchatka basin could be as cooperation priority basins in future.

Non-axisymmetric magnetostatic equilibrium with strong twisted component of magnetic field

The perturbation theory is applied further to the discussion of the equilibrium properties of a sunspot-like magnetic field with a strong twisted component. The basic state reduces to the usual one discussed extensively for the axisymmetric magnetostatic equilibrium with twisted component of magnetic field, and the perturbed state is described by two coupled equations. As the magnetic force-line is twisted, there is a magnetic tension in the azimuthal direction. In this case, the perturbed total pressure is no longer independent of the azimuthal variable θ, and the magnetic field in the dark penumbal fibril may be either stronger or weaker relatively.

Chemical equilibrium analysis and CFD simulation of coal combustion and NOx formation

A full two-fluid model of reacting gas-particle flows with an algebraic unified second-order moment (AUSM) turbulence-chemistry model is used to simulate Beijing coal combustion and NOx formation. The sub-models are the k-epsilon-kp two-phase turbulence model, the EBU-Arrhenius volatile and CO combustion model, the six-flux radiation model, coal devolatilization model and char combustion model. The blocking effect on NOx formation is discussed. In addition, the chemical equilibrium analysis is used to predict NOx concentration at different temperature. Results of CID simulation and chemical equilibrium analysis show that, optimizing air dynamic parameters can delay the NOx formation and decrease NOx emission, but it is effective only in a restricted range. In order to decrease NOx emission near to zero, the re-burning or other chemical methods must be used.

Topology of toroidal helical fields in non-circular cross-sectional tokamaks

The ordinary differential magnetic field line equations are solved numerically; the tokamak magnetic structure is studied on Hefei Tokamak-7 Upgrade (HT-7U) when the equilibrium field with a monotonic q-profile is perturbed by a helical magnetic field. We find that a single mode (m, n) helical perturbation can cause the formation of islands on rational surfaces with q = m/n and q = (m +/- 1, +/- 2, +/- 3,...)/n due to the toroidicity and plasma shape (i.e. elongation and triangularity), while there are many undestroyed magnetic surfaces called Kolmogorov-Arnold-Moser (KAM) barriers on irrational surfaces. The islands on the same rational surface do not have the same size. When the ratio between the perturbing magnetic field B-r(r) and the toroidal magnetic field amplitude B(phi)0 is large enough, the magnetic island chains on different rational surfaces will overlap and chaotic orbits appear in the overlapping area, and the magnetic field becomes stochastic. It is remarkable that the stochastic layer appears first in the plasma edge region.

A new method of measuring alcohol clusters in polyimide membrane: combination of inverse gas chromatography with equilibrium swelling

A new method of measuring the mean size of solvent clusters in swollen polymer membrane is presented in this paper. This method is based on a combination of inverse gas chromatography (IGC) and equilibrium swelling. The mechanism is that weight fraction activity coefficient of solvent in swollen polymer is influenced by its clusters size. The mean clusters size of solvent in swollen polymer can be calculated as the quotient of the weight fraction activity coefficient of clustering system dividing the weigh fraction activity coefficient of non-clustering system. In this experiment, the weigh fraction activity coefficient of non-clustering system was measured with IGC. Methanol, ethanol and polyimide systems were tested with the new method at three temperatures, 20, 40, and 60degreesC. The mean clusters size of methanol in polyimide was five, four, and three at each temperature condition, respectively. Ethanol did not form clusters (the mean clusters size was one). In contrast to the inherent narrow temperature range in DSC, XRD, and FTIR methods, the temperature range in IGC and equilibrium swelling is broad. Compared with DSC. XRD. and FTIR, this new method can detect the clusters of solvent-polymer system at higher temperature.

Surface-enhanced resonance Raman spectroscopy and spectroscopy study of redox-induced conformational equilibrium of cytochrome c adsorbed on DNA-modified metal electrode

The redox-induced conformational equilibrium of cytochrome c (cyt c) adsorbed on DNA-modified metal electrode and the interaction mechanism of DNA with cyt c have been studied by electrochemical, spectroscopic and spectroelectrochemical techniques. The results indicate that the external electric field induces potential-dependent coordination equilibrium of the adsorbed cyt c between its oxidized state (with native six-coordinate low-spin and non-native five-coordinate high-spin heme configuration) and its reduced state (with native six-coordinate low-spin heme configuration) on DNA-modified metal electrode. The strong interactions between DNA and cyt c induce the self-aggregation of cyt c adsorbed on DNA. The orientational distribution of cyt c adsorbed on DNA-modified metal electrode is potential-dependent, which results in the deviation from an ideal Nernstian behavior of the adsorbed cyt c at high electrode potentials. The electric-field-induced increase in the activation barrier of proton-transfer steps attributed to the rearrangement of the hydrogen bond network and the self-aggregation of cyt c upon adsorption on DNA-modified electrode strongly decrease the interfacial electron transfer rate.

Isothermal and non-isothermal crystallization kinetics of syndiotactic polypropelene

Isothermal and non-isothermal crystallization kinetics of a syndiotactic polypropylene(sPP) sample synthesized by new metallocene catalyst at different annealing temperatures and different cooling rates have been investigated by using differential scanning calorimetry(DSC) and density analysis. The equilibrium melting temperature( T-m(0)) is 158 degrees C by Hoffman-Weeks method. The equilibrium heat of fusion(Delta H-m(0)) is 88J/g in terms of the density analysis and DSC methods. The lateral and end surface free energies derived from the Lauritzen-Hoffman spherulitic growth rate equation are sigma = 5.2erg/cm(2) and sigma(e) = 69erg/cm(2), respectively. The work of chain folding is determined to be q = 33.75kJ/mol. Modified Avrami equation and Ozawa equation can be used to describe the non-isothermal crystallization behavior. And a new and convenient approach by combining the Avrami equation and Ozawa equation in a same crystallinity is used to describe the non-isothermal behavior as well. The crystallization activation energies are evaluated to be 73.7kJ/mol and 73.1kJ/mol for isothermal crystallization and non-isothermal crystallization, respectively. The Avrami exponent n is 1.5 similar to 1.6 for isothermal crystallization procedure, while the Avrami exponent n,is 2.5 similar to 3.5 for non-isothermal crystallization procedure. This indicated the difference of nucleation and growth between the two procedures.