气候系统和全球变暖——解读2021年诺贝尔物理奖

2021年诺贝尔物理学奖授予了两位气候学家和一位理论物理学家,以表彰他们在“理解复杂物理系统领域所做出的开创性贡献”.相信很多人会感到惊讶,为什么诺贝尔物理学奖授予了两位气候学家.本文将从以下几方面给予解读:为什么气候系统被称为复杂的物理系统,全球变暖的现状和未来,全球变暖的物理基础和科学简史,两位气候学家是如何基于基础物理理论建立了预测全球变暖的模型,以及检测和归因人类活动导致全球变暖的方法.     

铜氧化物超导体中存在一种内层轨道关联

本文研究了主要的几类铜氧化物超导体系,发现其中铜氧面的最近邻阳离子A有一个很好的规律:对于所有能够发生超导体系的A,其最外层p能级都非常接近,只分布在一个约12eV宽的窄小的区域内,从-22.85eV(Ba)到-34.80eV(Lu)之间,而且O的内层2s能级(-29.16 eV)恰恰正好为这个区域的中线.此外,A与铜氧面上的O之间的距离与该体系拥有的最高临界温度Tc存在一个清晰的规律,间距越小且A离子半径越大,Tc越高.因此,我们认为:铜氧面上的O与其最近邻大离子A内层轨道之间可能存在着一定的关联,而且这一内层关联与高温超导现象是相关的.     

振荡引向自组装

随着电子与机械元件越来越趋于小型化 ,这给科学家和工程师们提出了一个巨大的挑战 ,要求他们努力地生产出毫米和纳米量级的组件 .这个问题的可能出路之一是发展一种能使材料自组装的工艺技术 .现在 ,美国Argonne国家实验室与俄罗斯科学院微结构物理研究所的科学家们 ,正致力于发展一种新的方法 ,来促使微型粒子能自组装成一些复杂的图案结构 .在宏观领域有大量的实验曾证实 :将沙石、轴承滚珠或其他颗粒状的物质装于容器内进行搅拌 ,在重力与粒子间相互碰撞的作用下 ,通过振荡可以出现从八角的蜂窝状到无序的旋涡状等多种式样的和美丽的图…     

PISA测试对以能力立意中考命题的启示

PISA评估理念对我国基础教育产生了一定的影响,本文通过PISA公开的测试题和近年各地市中考的物理试题进行对比,提出了命题应从简单情景入手考查学生的观察与思考能力,从多方面考查学生的分析与综合能力,应注重对他们的创造性思维和创新能力的考查等。     

氘氢混合气体的高频离子源中H2D+与D+2的比例实测研究

分子离子H2D+在天体物理和天体化学研究中有重要意义,但在实验研究中不可避免混入D+2从而对实验结果产生影响.本文采取产物对比与分析的方法,将离子源中两种离子的比例实际测量出来,从而能较为准确地研究H2D+的结构和性质.将实验测量的结果与理论推算进行比较,得到了相对较好的结果.本文所采用的方法将对类似的研究提供有益的借鉴和启发.     

VH2+分子离子的结构与势能函数

本文从VH2 分子离子基态的电子状态及其离解极限出发,采用B3PW91的方法,对V原子采用SVP基组,对H原子采用6-311 G基组优化出VH2 (X3A2)分子离子稳定构型的平衡核间距Re=0 .1631 nm,∠HVH =112 .3858°,同时计算出振动频率,并使用多体项展式理论方法,导出了基态VH2 分子离子的分析势能函数,该势能表面准确地再现了VH2 (C2v)平衡结构,然后根据势能函数等值图讨论了反应势能面的静态特征,并利用杂化轨道理论解释了VH2 分子离子的结构.     

沉积温度对钛硅共掺杂类金刚石薄膜生长、结构和力学性能的影响

采用中频磁控溅射Ti80Si20复合靶在单晶硅表面制备了共掺杂的类金刚石薄膜.研究了沉积温度对薄膜生长速率、化学成分、结构、表面性质和力学性能的影响.结果表明:随沉积温度升高,薄膜生长速率降低,薄膜Ti和Si原子浓度增加,C原子浓度降低;在高温下沉积的薄膜具有低sp3C含量、低表面接触角、低内应力和高的硬度与弹性模量.基于亚表层注入生长模型分析了沉积温度对薄膜生长和键合结构的影响,从薄膜生长机制和微观结构解释了表面性质和力学性能的变化.     

硼化铝团簇Al-B_n(n=2～9)的密度泛函理论研究

基于密度泛函理论(Density Functional Theory,DFT),对中性硼化铝团簇AlBn(n=2～9)的几何结构、稳定性以及红外振动光谱进行了理论研究,讨论了他们的不同点及AlB4、AlB5、AlB6和AlB7的基态构型和相对稳定性.对于中性AlBn(n=2～9)基态构型,对比讨论了其失去[AlBn+(n=2～9)]和得到[AlBn-(n=2～9)]一个电子后化学键强度的变化、掺入铝原子的影响以及团簇几何结构的演化.计算结果表明:虽然掺入Al之后,团簇的稳定性差异变小,但是硼团簇和硼化铝团簇都趋向于形成平面、准平面结构以获得更大的稳定性;硼团簇的构型对硼化铝团簇的结构和稳定性起着决定性的作用;AlB3、AlB5和AlB8更稳定;红外光谱的振动模式倾向于B原子和对称性优先的趋势.     

复杂气候系统和全球变暖

两位气候学家和一位理论物理学家共同荣获2021年诺贝尔物理学奖.诺贝尔物理学奖委员会在背景介绍材料中指出,他们在"理解复杂物理系统领域做出了开创性贡献".相信很多人会对两位气候学家获奖而感到惊讶,物理学奖委员会进一步具体指出,人类活动导致全球变暖这一论断建立在坚实的科学基础之上,两位气候学家获奖是因为他们基于物理原理模...     

e+e－→qqg及γ→3g碎裂的色弦结构

Lund模型对e⁺e^－→qqg及γ→3g→h's的解释,是把Lund弦碎裂用到他们对这两系统假定的色弦结构上.本文直接从这些系统的颜色波函数出发,用QCD全面分析了它们的色弦结构.并揭示了Lund模型采用的色弦结构图象的合理与近似程度.     

Self-assembled pattern formation of block copolymers on the surface of the sphere using self-consistent field theory

The spherical surface is spatially discretized with triangular lattices to numerically calculate the Laplace-Beltrami operator contained in the self-consistent field theory (SCFT) equations using a finite volume method. Based on this method we have developed a spherical alternating-direction implicit (ADI) scheme for the first time to help extend real-space implementation of SCFT in 2D flat space to the surface of the sphere. By using this method, we simulate the equilibrium microphase separation morphology of block copolymers including AB diblocks, ABC linear triblocks and ABC star triblock copolymers occurred on the spherical surface. In general, two classes of microphase separation morphologies such as striped patterns for compositionally symmetric block copolymers and spotted patterns for asymmetric compositions have been found. In contrast to microphase separation morphology in 2D flat space, the geometrical characteristics of a sphere has a large influence on the self-assembled morphology. For striped patterns, several of spiral-form and ring-form patterns are found by changing the ratio of the radius of a sphere to the averaging width of the stripes. The specific pattern such as the striped and spotted pattern with intrinsic dislocations or defects stems from formed periodic patterns due to microphase separation of block copolymers arranged on the curved surface.     

Morphological similarity of road networks and cracks

An investigation was made regarding to what extent road network patterns are reproduced by a crack model from a viewpoint that they seem to resemble crack patterns in morphology. A desiccation model using double-layered cellular meshes was considered with the parameters representing the anisotropy of the material and the coarseness of grains, together with the introduction of singularities in points and in lines. The model can generally reproduce the real crack patterns and the road network patterns of cities with characteristic morphology by appropriately choosing the values of parameters, indicating that the similar mechanism acts on the formation of road networks and cracks of material although the relevant scales of space time differ from each other. Factors which make the road networks more complex and irregular in morphology were also investigated.     

Sequence of morphological transitions in two-dimensional pattern growth from aqueous ascorbic Acid solutions

A sequence of morphological transitions in two-dimensional dehydration patterns of aqueous solutions of ascorbic acid is observed with humidity as a control parameter. Change in morphology occurs due to humidity induced variation in the concentration of the metastable supersaturated solution phase formed after initial solvent evaporation. As percent humidity is varied from 40 to 80, patterns change from compact circular --> radial --> density modulated radial (a new morphology) --> density modulated circular --> density modulated dendritic (a new morphology) --> dense branching.     

Branched crystal morphology of linear polyethylene crystallized in a two-dimensional diffusion-controlled growth field

The branched crystal morphology of linear polyethylene formed at various temperatures from thin films has been studied by atomic-force microscopy (AFM), transmission electron microscopy (TEM), electron diffraction (ED) pattern and polymer decoration technique. Two types of branched patterns, i.e. dendrite and seaweed patterns, have been visualized. The fractal dimension d _f = 1.65 of both dendrite and some of seaweed patterns was obtained by using the box-counting method, although most of the seaweed patterns are compact. Selected-area ED patterns indicate that the fold stems tilt about 34.5^° around the b-axis and polymer decoration patterns show that the chain folding direction and regularity in two (200) regions are quite different from each other. Because of chain tilting, branched crystals show three striking features: 1) the lamella-like branches show two (200) regions with different thickness; 2) the crystals usually bend towards the thin region; 3) the thick region grows faster by developing branches, thus branches usually occur outside the thick region. The branched patterns show a characteristic width w, which gives a linear relationship with the crystallization temperature on a semilogarithmic plot. Received 15 March 2002 and Received in final form 29 April 2002     

On logical gates in precipitating medium: Cellular automaton model

We study a two-dimensional semi-totalistic binary cell-state cellular automaton, which imitates a reversible precipitation in an abstract chemical medium. The systems exhibits a non-trivial growth and nucleation. We demonstrate how basic computational operation can be realized in the system when the propagation of the growing patterns is self-restricted by stationary localizations. We show that precipitating patterns of different morphology compete between each other and thus implement basic logical gates.     

Market volatility modeling for short time window

The gain or loss of an investment can be defined by the movement of the market. This movement can be estimated by the difference between the magnitudes of two stock prices in distinct periods and this difference can be used to calculate the volatility of the markets. The volatility characterizes the sensitivity of a market change in the world economy. Traditionally, the probability density function (pdf) of the movement of the markets is analyzed by using power laws. The contributions of this work is two-fold: (i) an analysis of the volatility dynamic of the world market indexes is performed by using a two-year window time data. In this case, the experiments show that the pdf of the volatility is better fitted by exponential function than power laws, in all range of pdf; (ii) after that, we investigate a relationship between the volatility of the markets and the coefficient of the exponential function based on the Maxwell-Boltzmann ideal gas theory. The results show an inverse relationship between the volatility and the coefficient of the exponential function. This information can be used, for example, to predict the future behavior of the markets or to cluster the markets in order to analyze economic patterns.     

不同衬底和CdCl2退火对磁控溅射CdS薄膜性能的影响

在科宁7059玻璃, FTO, ITO, AZO四种衬底上磁控溅射CdS薄膜, 并在CdCl₂+干燥空气380 ℃退火, 分别研究了不同衬底和退火工艺对CdS薄膜形貌、结构和光学性能的影响. 扫描电子显微镜形貌表明: 不同衬底原位溅射CdS薄膜的形貌不同, 退火后相应CdS薄膜的晶粒度和表面粗糙度明显增大. XRD衍射图谱表明: 不同衬底原位溅射和退火CdS薄膜均为六角相和立方相的混相结构, 退火前后科宁7059玻璃, FTO, AZO衬底上CdS薄膜有 H(002)/C(111) 最强衍射峰, ITO衬底原位溅射CdS薄膜没有明显的最强衍射峰, 退火后出现 H(002)/(111) 最强衍射峰. 紫外-可见分光光度计分析表明: AZO, FTO, ITO, 科宁7059玻璃衬底CdS薄膜的可见光平均透过率依次减小, 退火后相应衬底CdS薄膜的可见光平均透过率增大, 光学吸收系数降低; 退火显著增大了不同衬底CdS薄膜的光学带隙. 分析得出: 上述结果是由于不同衬底类型和退火工艺对CdS多晶薄膜的形貌、结构和带尾态掺杂浓度改变的结果. 关键词： CdS薄膜 磁控溅射 退火再结晶 带尾态     

The effect of high-frequency acoustic wave vibration pattern on HKUST’s multi-level pore structure

The physical properties of materials are critical to their functionality, and the ability to control these properties using external forces is a significant challenge. In this study, we investigate the effect of three high frequency acoustic wave vibration patterns on the structure and morphology of MOF particles. Our results indicate that while regular vibration patterns generated by SAW can alter particle morphology, hybrid waves and Lamb waves with irregular vibration patterns can synthesise MOF crystals with multi-level pores. The vibration pattern of acoustic waves is shown to be a critical factor in controlling the particle morphology process. These results provide new insights into the precise control of crystal structure and the theory of crystallisation by particle attachment (CPA).     

Eden growth model for aggregation of charged particles

The stochastic Eden model of charged particles aggregation in two-dimensional systems is presented. This model is governed by the following two parameters: screening length of electrostatic interaction, , and short-range attraction energy, E. Different patterns of finite and infinite aggregates are observed. They are of the following morphology types: linear or linear with bending, worm-like, DBM (dense-branching morphology), DBM with nucleus, and compact Eden-like. The transition between the different modes of growth is studied and phase diagram of the growth structures is obtained in co-ordinates. The detailed aggregate structure analysis, including analysis of their scaling properties, is presented. The scheme of the internal inhomogeneous structure of aggregates is proposed. Received 2 September 1998 and Received in final form 15 January 1999     

Stock index dynamics worldwide: a comparative analysis

We perform a comparative analysis of twenty-four daily stock indices across the world, encompassing developed and emerging markets. We compute, directly from the return empirical time series, the Kramers-Moyal (KM) expansion coefficients that govern the evolution of the probability density function of returns throughout timelags. Our study discloses universal patterns of the KM coefficients, which can be described in terms of a few microscopic parameters. These parameters allow to quantify features such as deviations from Gaussianity or from efficiency, providing a tool to discriminate market dynamics.