基于平稳小波和相空间重构的激光混沌预测

提出了一种激光混沌时间序列预测算法.该算法通过平稳小波分解，将原始数据序列分解为与原序列等长的尺度系数和小波系数，利用坐标延迟理论，重建各级尺度系数和各级小波系数的相空间,再根据混沌吸引子的稳定性和分形性,在相空间中对尺度系数和小波系数进行预测,进而通过平稳小波重构算法,实现了时间序列的非线性预测.该算法对数据可以进行更平滑的处理，比无小波算法预测的时间范围更长.通过仿真试验说明，原始时间数据序列被成功的重建，说明算法能够有效的对非线性动态系统的时间序列进行建模和预测.     

The onset of the tetrabonded structure in liquid water

Water properties are dominated by the hydrogen bond interaction that gives rise in the stable liquid phase to the formation of a dynamical network. The latter drives the water thermodynamics and is at the origin of its well known anomalies. The HB structural geometry and its changes remain uncertain and still are challenging research subjects. A key question is the role and effects of the HB tetrahedral structure on the local arrangement of neighboring molecules in water. Here the hydrogen dynamics in bulk water is studied through the combined use of Neutron Compton Scattering and NMR techniques. Results are discussed in the framework of previous studies performed in a wide temperature range, in the liquid, solid, and amorphous states. For the first time this combined studies provide an experimental evidence of the onset of the water tetrahedral network at T~315 K, originally proposed in previous studies of transport coefficients and thermodynamical data; below this temperature the local order in water changes and the lifetime of local hydrogen bond network becomes long enough to gradually develop the characteristic tetrahedral network of water.     

Ion hydration and hydrogen bond structure in NaCl solutions at temperatures and pressures for carbon dioxide sequestration: the effects of solvated CO2 molecules

In the present study, we focus on the phase properties of CO₂–brine systems in geologic media. Molecular dynamics simulation methods were used to investigate the ion hydration and hydrogen bond structure in CO₂–brine and brine solutions at temperatures and pressures for CO₂ sequestration. By comparing the results of CO₂–brine solutions with those of brine solutions, the effects of solvated CO₂ were analysed and discussed.     

Fluctuations and stability of stationary non-equilibrium systems in detailed balance

A generalized thermodynamic potential for Markoffian systems with detailed balance and far from thermal equilibrium has been derived in a previous paper. It was shown that the principle of detailed balance is equivalent to a set of conditions fulfilled by this potential (“potential conditions”). The properties of this potential allow us to extend the validity of a number of thermodynamic concepts well known for systems in or near thermal equilibrium to stationary states far from thermal equilibrium. The concept of symmetry breaking phase transitions for these systems is introduced in analogy to thermal equilibrium systems by considering the dependence of the stationary probability density of the system on a set of externally controlled parameters {λ}. A functional of the time dependent probability density of the system is defined in close analogy to the Gibb's definition of entropy. This functional has the properties of a Ljapunov functional of the governing Fokker-Planck equation showing the stability of the stationary probability density. The Langevin equations connected with the Fokker-Planck equation are considered. It is shown that, by means of the potential conditions, generalized “thermodynamic” fluxes and forces may be defined in such a way that the smoothly varying part of the Langevin equations (kinetic equations) constitutes a linear relation between fluxes and forces. The matrix of coefficients is given by the diffusion matrix of the Fokker-Planck equation. The symmetry relations which hold for this matrix due to the potential conditions then lead to the Onsager-Casimir symmetry relations extended to systems with detailed balance near stationary states far from thermal equilibrium. Finally it is shown that under certain additional assumptions the generalized thermodynamic potential may be used as a Ljapunov function of the kinetic equations.     

InOOH压致氢键对称化及其弹性性质

利用第一性原理研究了InOOH在高压下的氢键对称化行为及其对InOOH弹性等性质的影响.结果表明约在18 GPa时InOOH中的氢键发生了对称化转变,导致轴比率b/c对压力的斜率由负值变为正值;压缩弹性常数、非对角弹性常数、体积模量和纵波波速出现异常增加,如体积模量增加了20%—40%.高压下InOOH弹性性质呈现出更加明显的各向异性.常压下InOOH呈现韧性,且伴随着氢键对称化韧性异常增加.对畸变金红石型MOOH(M=Al,In,Ga,Fe,Cr)化合物在高压下的弹性性质转变与氢键性质转变的耦合规律进行了初探.     

利用拉曼光谱分析冰Ih相的表面薄层的氢键结构

水是生活中一种最基本且最重要的物质,由于它的一些奇特性质和反常物性,得到了广泛的研究,而拉曼光谱是研究水分子结构的一种非常合适的方法,它通过获得分子的振动和转动信息来理解分子结构和分子间的相互作用。在常压下测量了-20～-190 ℃温度范围内冰Ih相的表面薄层的拉曼光谱,实验结果发现随温度降低,冰Ih相的O∶H范德瓦尔斯键向高波数方向移动,而O-H极性共价键向低波数方向移动;且拉曼频移与温度呈线性关系,通过对不同振动模式的斜率进行比较,判断其键长的伸缩变化关系,从而证明了冰Ih相密度随温度的减小而增大,采用氢键理论(结构)给予了解释。同时,发现在-150 ℃时,O-H键反对称伸缩振动模式和O∶H键振动模式的拉曼峰强发生了突变,这表明冰Ih相发生了相变--冰Ⅺ相(冰Ih的质子有序相)。     

乙二醇分子间氢键结构与溶剂效应

采用密度泛函理论在B3LYP/6-311++G** (范德华校正)水平上研究乙二醇在气相中分别与乙腈、丙酮、四氢呋喃、水、乙二醇形成氢键二聚体的结构性质,根据PCM 极化统一场模型讨论氢键溶剂效应。结果表明,五种氢键二聚体分子中的氢键属于红移氢键,溶剂使氢键二聚体分子的偶极矩变大,并对OH振动频率的影响不大。     

乙二醇分子间氢键结构与溶剂效应

采用密度泛函理论在B3LYP/6-311++G~(**)水平上研究乙二醇在气相中分别与乙腈、丙酮、四氢呋喃、水、乙二醇形成氢键二聚体的结构性质,根据PCM(polarized continuum model)极化统一场模型讨论氢键溶剂效应.结果表明,五种氢键二聚体分子中的氢键属于红移氢键,溶剂使氢键二聚体分子的偶极矩变大,并对OH振动频率的影响不大.     

Note on the Kaplan–Yorke Dimension and Linear Transport Coefficients

A number of new relations between the Kaplan–Yorke dimension, phase space contraction, transport coefficients and the maximal Lyapunov exponents are given for dissipative thermostatted systems, subject to a small but non-zero external field in a nonequilibrium stationary state. A condition for the extensivity of phase space dimension reduction is given. A new expression for the linear transport coefficients in terms of the Kaplan–Yorke dimension is derived. Alternatively, the Kaplan–Yorke dimension for a dissipative macroscopic system can be expressed in terms of the linear transport coefficients of the system. The agreement with computer simulations for an atomic fluid at small shear rates is very good.     

Water behavior in the neighborhood of hydrophilic and hydrophobic membranes: Lessons from molecular dynamics simulations

The study of properties of water in the vicinity of surfaces poses a fascinating challenge. In this article we studied the behavior of water molecules in the neighborhood of membranes. We addressed the question of how these water molecules are influenced by the membranes’ hydrophilicity. Three systems were studied through molecular dynamics simulations: water in the presence of a hydrophilic membrane (PL), water in the presence of a hydrophobic (PB) one and water in the absence of membranes (BULK). Additionally, in order to study the dependence of the effect of the membrane on the behavior of neighboring water molecules with temperature, each system was simulated at three different temperatures (K): 250, 300 and 350. For each condition, kinetic and structural features were studied. The first feature involved the calculation of diffusion coefficients and activation energy. The second feature was evaluated through the study of water density and hydrogen bond distribution. From the present study we concluded that: (1) density studies underestimate the influence of both hydrophilic and hydrophobic membranes on the neighboring water molecules; (2) the hydrophilic and hydrophobic membranes disturb the hydrogen bond network within distances ranging from 1 to 8 nm, depending on the nature of the membrane and the temperature conditions; (3) the presence of a hydrophobic surface results in an enhancement of the natural hydrogen bond network present in liquid water, to a greater extent than what even an ordered Ih ice structure is able to achieve (i.e. PL membrane); (4) the structural enhancement due to the presence of a hydrophobic surface involves roughly 18 to 24 water hydration layers, for ambient and above temperature conditions.     

Defects,phase transitions and dynamical disorder in superionic protonic conductors H3OUO2PO4 · 3H2O and CsHSO4

Specific properties of the hydrogen bond and protons appear to be responsible for the formation of the quasi-liquid state of conducting ions and the resulting superionic behaviour. This state is reached by successive phase transitions involving the mobile species and their interactions with a more or less rigid framework. H₃OUO₂PO₄ · 3H₂O (HUP) and CsHSO₄ can be considered as models of wet and dry superionic conduction, respectively. Interactions between static effects and dynamical disorder as well as the coupling between sublattices are discussed in relation to results obtained by calorimetry, impedance spectroscopy (up to 10 GHz), vibrational spectroscopy and quasi-elastic neutron scattering.     

铵水间质子交换的再研究:不受扩散约束的化学交换

对铵盐水溶液中铵离子与水分子间的质子交换进行了再研究. 以核磁共振(NMR) 波谱学方法测定了不同pH值, 不同温度和含不同共存盐浓度的氯化铵水溶液中质子交换速率, 组分自扩散系数及NMR自旋晶格弛豫时间. 结果显示铵水间的质子交换并不受交换主体分子或离子自扩散的约束. 交换机理包括化学键和氢键的交换. 在溶液中, 水分子以氢键为桥 梁连接铵和其因水解而产生的碱性部分--氨. 在氢交换的过程中, 氨从水分子接受一个氢 成为铵, 同时另外一端的铵提供一个氢给水分子而变成氨, 或者一个氢从水分子转移到氨而同 时另外一个氢从铵转移到水. 在铵水质子交换的过程中没有净的电荷转移. 在低pH条件下, 由水解产生的氨的浓度降低, 亦即铵-水-氨复合物减少, 结果氢交换的可能性降低. 这解释了生物氢交换体系中的一种常见的在低pH值条件下氢交换变慢的现象.     

从常温常压到超临界乙醇的分子动力学模拟

采用分子动力学方法系统地研究了从常温常压到超临界状态乙醇的热力学性质、结构性质和动力学性质.模拟发现随着温度的升高,体系焓值增大,乙醇分子间的氢键作用减弱,自扩散系数增大;随着压强的增大,乙醇分子间的氢键作用增强,自扩散系数减小;乙醇自扩散系数在液相区随温度变化不明显,在气相区随压强增大很快减小,超临界区乙醇的自扩散系数比液相区大十几倍.温度和压强对乙醇自扩散系数的影响可通过密度来体现.与常温常压相比,超临界条件下的乙醇体系因密度涨落存在分子聚集现象,且在低密度区域更显著;乙醇分子间的氢键作用明显减弱,结     

Synthesis,properties, and solvatochromism of 1,3‐dimethyl‐5‐{(thien‐2‐yl)‐[4‐(1‐piperidyl) phenyl]methylidene}‐(1H,3H)‐pyrimidine‐2,4,6‐trione

A new merocyanine dye, 1,3‐Dimethyl‐5‐{(thien‐2‐yl)‐[4‐(1‐piperidyl)phenyl]methylidene}‐ (1H, 3H)‐pyrimidine‐2,4,6‐trione 3 , has been synthesized by condensation of 2‐[4‐(piperidyl)benzoyl]thiophene 1 with N,N′‐dimethyl barbituric acid 2 . The solvatochromic response of 3 dissolved in 26 solvents of different polarity has been measured. The solvent‐dependent long‐wavelength UV/Vis spectroscopic absorption maxima, v_max, are analyzed using the empirical Kamlet–Taft solvent parameters π* (dipolarity/polarizability), α (hydrogen‐bond donating capacity), and β (hydrogen‐bond accepting ability) in terms of the well‐established linear solvation energy relationship (LSER): (1) The solvent independent coefficients s , a , and b and (v_max)₀ have been determined. The McRae equation and the empirical solvent polarity index, E_T(30) have been also used to study the solvatochromism of 3 . Copyright © 2007 John Wiley & Sons, Ltd.     

Lattice dynamics and phase diagrams for hydrogen bonded systems

Abstract

A variational correlated ground state wave-function theory is applied to investigate the high-pressure deformation of hydrogen-bond potential described by a double Morse potential functions. The evolution of the hydrogen bond potential with increasing pressure and the effects of deuterium isotope substitution on the quantum-fluctuation-driven phenomena are discussed. The theory was employed for predicting and interpreting the pressure dependence of the phase transition temperatue for KDP-like ferroelectrics and NQR-frequency coefficients for several deuterated and undeuterated crystals.