A kinetic Monte Carlo method on super-lattices for the study of the defect formation in the growth of close packed structures

A modified Kinetic Lattice Monte Carlo model has been developed to predict growth rate regimes and defect formation in the case of the homo-epitaxial growth of close packed crystalline structures. The model is an improvement over standard Monte Carlo algorithms, which usually retain fixed atom positions and bond partners indicative of perfect crystal lattices. Indeed, we extend the concepts of Monte Carlo growth simulations on super-lattices containing additional sites (defect sites) with respect to those of the reference material. This extension implies a reconsideration of the energetic mapping, which is extensively presented, and allows to describe a complex phenomenology that is out of accessibility of standard stochastic approaches. Results obtained using the Kawasaki and the Bond-Counting rules for the transition probability of the Monte Carlo event are discussed in details. These results demonstrate how the defect types (local or extended), the formation mechanisms and the defect generation regimes can be characterized using our approach.     

Spatiotemporal model for the progression of transgressive dunes

Transgressive dune fields, which are active sand areas surrounded by vegetation, exist on many coasts. In some regions like in Fraser Island in Australia, small dunes shrink while large ones grow, although both experience the same climatic conditions. We propose a general mathematical model for the spatiotemporal dynamics of vegetation cover on sand dunes and focus on the dynamics of transgressive dunes. Among other possibilities, the model predicts growth parallel to the wind with shrinkage perpendicular to the wind, where, depending on geometry and size, a transgressive dune can initially grow although eventually shrink. The larger is the initial area the slower its stabilization process. The model’s predictions are supported by field observations from Fraser Island in Australia.     

The use of relative residues in fitting experimental data: an example from fluid mechanics

A curve fitting model is presented which minimizes the sum of squares of relative residues and expressions for the fit coefficients and their respective errors are derived. The new model is compared to the normal least squares model, using as an example the Reynolds number-drag coefficient data for a sphere. The results show that the best fit was obtained with the new model, indicating it may provide a useful tool for data analysis.     

片段化森林中檵木幼苗种内叶经济性状变异及其驱动因子

在异质性生境中,种内功能性状变异有助于植物对环境的适应,进而影响种群更新、群落构建和生态系统过程。探讨了种内叶经济性状的变异及受生境异质性的塑造情况。以千岛湖片段化生境中的常见种檵木（Loropetalum chinense）的幼苗为研究对象,测定了200株檵木幼苗个体水平的7个叶经济性状（比叶面积SLA、叶全碳量C、叶全氮量N等）及其对应的生境因子（郁闭度、土壤全碳量、土壤全氮量等）,采用相关性检验、主成分分析和线性混合效应模型等方法探讨片段化森林中檵木幼苗的种内叶经济性状变异及生境异质性对该变异的驱动作用。结果显示：（1） 在7个叶经济性状所构成的21对相关性分析中,有12对显著相关。经主成分分析降维后,主成分1（PC1）占性状总变异的43.02%,主要与比叶面积、叶绿素浓度、叶全氮量呈正相关,与叶干物质质量分数和叶碳氮比呈负相关,体现了檵木的种内叶经济谱,可反映叶片的最大光合效率。（2）片段化对生境条件和叶经济性状均有影响。岛屿森林群落的郁闭度显著低于大陆。相对于大陆,岛屿中的檵木幼苗趋向于更小的PC1值（缓慢投资-收益策略）;大岛边缘较大岛内部偏向于更小的PC1值。（3）生境因子中,郁闭度对PC1具有显著正效应。研究表明,片段化生境中的檵木在幼苗阶段存在叶经济谱,生境片段化可通过影响生境条件进而改变檵木幼苗的叶经济性状。随着生境片段化程度的加剧,檵木幼苗的叶经济性状逐渐向缓慢投资-收益策略靠拢。     

Multiple domain dynamics simulated with coupled level sets

We adapt the level-set method to simulate epitaxial growth of thin films on a surface that consists of different reconstruction domains. Both the island boundaries and the boundaries of the reconstruction domains are described by different level-set functions. A formalism of coupled level-set functions that describe entirely different physical properties is introduced, where the velocity of each level-set function is determined by the value of the other level-set functions.     

上海市崇明岛浅层砂土、粉土分布探讨

通过对崇明岛内大量勘探资料的分析研究,本文分析了岛内浅层砂土、粉土的分布特征,并根据岩性及静力触探指 标对其进行详细分类,找出了每类土的典型静力触探曲线,最后探讨了各类土的液化问题。     

Fluorine and chlorine behavior in chlorine-rich volcanic rocks from White Island, New Zealand

Extraordinarily high chlorine-bearing volcanic bombs were erupted from White Island volcano on January 25, 1987. The concentrations of fluorine and chlorine were measured in these paralava bombs and their likely parent rocks. The paralavas contain glass with over 1.0 wt.% and up to 1.7% of chlorine. The F/Cl ratios and their relationship with other constituents show that the fluorine and chlorine in the bombs were derived from hydrothermal fluid, most likely concentrated brine in an active Crater Pool.     

A Direct Experimental Evidence of Collective Electron Resonance Mechanism of Surface Enhanced Infrared Spectroscopy (Seirs)

Abstract

We report here the preliminary results of the surface enhanced transmission infrared spectra of CH₃(CH₂)₇Azo(CH₂)₃COOH monolayers on CaF₂ substrate which was coated by silver island films with different size and distribution. The larger enhancement of absorbance of v(C=O) in COOH residing between silver island gap and small enhancement of absorbance of vibration mode of COO^? located on the silver islands are observed. It give us a direct experimental evidence of the collective electron resonance mechanism of surface enhance infrared spectroscopy (SEIRS), i.e. the decrease of the electromagnetic (EM) coupling reduces the enhancement factor of SEIRS.     

Non-monotonous dependence of surface roughness on factors influencing energy of adatoms during thin island film growth

Many experimental results show that surface roughness of thin films can increase, decrease, stay constant or pass through the minimum with the change in substrate temperature, energy of arriving atoms or assisted beam (electrons, photons, ions), depending on material and interval of variation of those parameters. The aim of this paper is to explain and analyze this non-monotonous behavior of surface roughness by proposed kinetic model. The model is based on rate equations and includes processes of surface diffusion of adatoms, nucleation, growth and coalescence of islands in the case of thin films growth in Volmer-Weber mode. It is shown by modeling that non-monotonous dependence of surface roughness on the factors influencing energy of adatoms (e.g. temperature, assisted beam irradiation, accelerating voltage) occurs as a result of interplay between diffusion length of adatoms and size of islands, because both parameters depend on energy of adatoms. Variation of island size and diffusion length results in atomic jumps from islands forming rougher or smoother surface. The functions of surface roughness, island size, island density on diffusion length of adatoms and on other parameters are calculated and analyzed in this work.     

浙江梅山岛附近海域大型底栖动物和游泳动物的群落组成及其与环境因子的关系

2020年9月对梅山岛附近海域的大型底栖动物和游泳动物进行了定量调查,分析了梅山岛附近海域大型底栖动物和游泳动物的群落组成和数量特征,包括群落种类组成、丰度、生物量和优势种,并对大型底栖动物和游泳动物的群落组成、数量特征与水深、悬浮物、营养盐等重要环境因子进行了相关性分析.结果表明:梅山岛附近海域共有大型底栖动物5门16种,其中环节动物门5种、软体动物和节肢动物门各4种、棘皮动物门2种、脊索动物门1种;梅山岛附近海域大型底栖动物平均丰度为12.73 ind·m^-2,平均生物量为2.87 g·m^-2,其中纵肋织纹螺(Nassarius variciferus)为研究海域唯一的优势种.游泳动物共有55种,其中鱼类29种、甲壳动物23种、软体动物门中头足纲动物2种、腔肠动物1种;游泳动物在整个研究海域的尾数密度为24.77×10³ind·km^-2,重量密度为144.53 kg·km^-2;游泳动物优势种共9种,其中龙头鱼(Harpadon nehereus)的优势度最高,口虾蛄(Ora...