Anisotropic finite-size scaling analysis of a two-dimensional driven diffusive system

The standard two-dimensional uniformly driven diffusive model is simulated extensively for much larger systems with a multi-spin coding technique. The nonequilibrium phase transition is analyzed with anisotropic finite-size scaling both at the critical point and off the critical point. The field-theoretic values of critical exponents fit the data well at and aboveT _c . BelowT _c the scaling is rather difficult and the results are not conclusive.     

铝丝阵Z箍缩辐射产生机理初步研究

利用一维非平衡辐射磁流体力学程序研究了铝丝阵内爆过程中的能量转化规律和辐射产生机理.细致讨论了Z箍缩过程中脉冲功率驱动器电磁能馈入等离子体,等离子体动能转化为内能以及通过一系列原子过程电子内能转化为X射线辐射的能量转化机理.结合离子布居信息深入分析了Z箍缩过程中的辐射产生机理.结果表明,在内爆压缩阶段,电离和激发过程占优,线辐射占据总辐射的绝大部分.在滞止时,离子大都处于裸核离化度,连续谱辐射达到峰值.在滞止附近,线辐射出现两个峰值.在膨胀过程中,光电复合过程优于三体复合,线辐射占总辐射的份额逐渐下降.     

端基对分子器件整流性质的影响

利用基于非平衡Green函数加密度泛函理论的第一原理方法,研究了以S(Se)为端基的三并苯环分子夹在两半无限长的Au电极之间构成双探针系统的输运特性,发现体系具有较好的整流效应,最大整流系数达到6;用H取代右端同一位置的一个S（Se）,整流行为明显减弱.分析认为,这种整流是由于分子两端与电极的耦合不对称,使正负偏压下分子能级的移动和空间轨道分布不同所致.比较而言,S端基与电极的耦合导致的整流比Se强. 关键词： 电子输运 整流行为 非平衡Green函数方法     

边界条件局部变化对二维发汗冷却的影响

本文通过对发汗冷却的多孔区域进行二维非热平衡数值模拟,研究了多孔介质区域进口处对流换热系数、冷却剂流量局部降低以及多孔介质受热表面热流密度局部增大对青铜、陶瓷两种不同多孔材料的温度场的影响。计算结果表明,冷却剂在进口处与多孔壁面对流换热系数的增大使多孔介质内部趋向于热平衡;热端壁面对流换热系数、冷却剂流量的局部变化对陶瓷多孔壁面在该局部区域的影响要大于青铜多孔壁面,但青铜多孔壁面受影响的区域更大,而冷却剂流量的局部降低对两种材料固体、流体间温差的影响程度基本一致。     

PRESSURE-VELOCITY EQUILIBRIUM HYDRODYNAMIC MODELS

This article describes mathematical models for phase separated mixtures of materials that are in pressure and velocity equilibrium but not necessarily temperature equilibrium. General conditions for constitutive models for such mixtures that exhibit a single mixture sound speed are discussed and specific examples are described.     

Understanding quantum entanglement by thermo field dynamics

We propose a new method to understand quantum entanglement using the thermo field dynamics (TFD) described by a double Hilbert space. The entanglement states show a quantum-mechanically complicated behavior. Our new method using TFD makes it easy to understand the entanglement states, because the states in the tilde space in TFD play a role of tracer of the initial states. For our new treatment, we define an extended density matrix on the double Hilbert space. From this study, we make a general formulation of this extended density matrix and examine some simple cases using this formulation. Consequently, we have found that we can distinguish intrinsic quantum entanglement from the thermal fluctuations included in the definition of the ordinary quantum entanglement at finite temperatures. Through the above examination, our method using TFD can be applied not only to equilibrium states but also to non-equilibrium states. This is shown using some simple finite systems in the present paper.     

Mesoscopic transport equations and contemporary thermodynamics: an introduction

The local equilibrium hypothesis is a very successful basis for non-equilibrium thermodynamics over a wide range of phenomena and physical situations. However, the increasing interest in small systems in nanotechnology, in rarefied gases in high-altitude aeronautics, in high-frequency behaviour in information processing, or the search for new materials with sophisticated internal microstructures and tailored thermal properties have led one to ask about the limits of validity of this hypothesis, and to go beyond it. Here we do so in a constructive way, i.e. not only pointing out at these limits, but also embedding the local-equilibrium theory in a more general framework which explicitly exhibits these limits and suggests how to go beyond them, in search for a wider range of applications and a deeper understanding of the foundations.     

一维线性非共轭石墨烯基(CH2)n分子链的电子输运

一维非共轭烷烃链虽不具富电子或少电子特征,但常存在于单分子器件或多肽、蛋白质等生物分子中,对电子传输产生重要影响.为理解这类物质的电子输运特征,本研究设计了一维线性非共轭(CH2)n分子结模型,并利用密度泛函理论结合非平衡态格林函数的方法,对(CH2)n(n=1-12)线性分子链与两个石墨烯电极耦合而成的分子结进行了第一性原理计算.结果表明,CH2分子链随着n值的变化,其电导值表现出明显的奇偶振荡现象,并且随着链长的增加呈指数级的衰减,这一结果与实验研究取得了很好的一致性,为理解和设计性能更加优良的单分子器件提供了重要理论依据.     

Seeded Polymerization of an Amide-Functionalized Diketopyrrolopyrrole Dye in Aqueous Media

The self-assembly of an amide-functionalized dithienyldiketopyrrolopyrrole (DPP) dye in aqueous media was achieved through seed-initiated supramolecular polymerization. Temperature- and time-dependent studies showed that the spontaneous polymerization of the DPP derivative was temporally delayed upon cooling the monomer solution in a methanol/water mixture. Theoretical calculations revealed that an amide-functionalized DPP derivative adopts an energetically favorable folded conformation in the presence of water molecules due to hydration. This conformational change is most likely responsible for the trapping of monomers in the initial stage of the cooperative supramolecular polymerization in aqueous media. However, the monomeric species can selectively interact with externally added fragmented aggregates as seeds through concerted π-stacking and hydrogen-bonding interactions. Consequently, the time course of the supramolecular polymerization and the morphology of the aggregated state can be controlled, and one-dimensional fibers that exhibit a J-aggregate-like bathochromically shifted absorption band can be obtained.     

The electronic properties and electron transport of sawtooth penta-graphene nanoribbon under uniaxial strain: ab-initio study

ABSTRACT

The electronic properties and electron transport of a sawtooth penta-graphene nanoribbon (SSPGNR) under uniaxial strains are theoretically studied by density-functional theory (DFT) in combination with the non-equilibrium Green's function formalism. We investigated the electronic structures and the current–voltage (I–V) characteristics of the SSPGNRs under a sequence of uniaxial strains in range from 10% compression to 10% stretch. In this strained range, carbon atoms still keep a pentagon network, but with the changing bond lengths. The C–C bond lengths change almost linearly with the tolerable strain. The value of the band gap of SSPGNRs can be depicted as a parabola under uniaxial strain. Our calculations show that the current is monotonous increase with compressive strain at the same applied bias voltage. In case of tensile strain, the variable rule of the current is different that it increases at first and decrease later. The fundamental physical properties (band structure, I–V characteristic) of SSPGNRs seem to be more sensitive to compressive strain than the stretch strain. The current intensity of the compressive-SSPGNR is by 2 orders of magnitude compared to that of the tensile-SSPGNR at the same strain in range from 6% to 10%. The results obtained from our calculations are beneficial to practical applications of these strained structures in SSPGNRs-based electromechanical devices.