Growth Mechanism of Microcrystalline Silicon Films by Scaling Theory and Monte Carlo Simulation

Hydrogenated microcrystalline silicon （~c-Si：H） films with a high deposition rate of 1.2nm/s were prepared by hot-wire chemical vapor deposition （HWCVD）. The growth-front roughening processes of the μc-Si..H films were investi- gated by atomic force microscopy. According to the scaling theory, the growth exponent β≈0.67, the roughness exponent α≈0.80,and the dynamic exponent 1/z = 0.40 are obtained. These scaling exponents cannot be explained well by the known growth models. An attempt at Monte Carlo simulation has been made to describe the growth process of μc-Si： H film using a particle reemission model where the incident flux distribution,the type and concentration of growth radical, and sticking,reemission,shadowing mechanisms all contributed to the growing morphology.

Effects of climate,biotic factors,and phylogeny on allometric relationships:testing the metabolic scaling theory in plantations and natural forests across China

Background:Metabolic scaling theory(MST)is still in debate because observed allometric exponents often deviate from MST predictions,and can change significantly depending on environment,phylogeny,and disturbance.We assembled published scaling exponents from literatures for three allometric relationships linked to biomass allocation:leaf biomassdiameter(LD),stem biomassdiameter(SD),and root biomassdiameter(RD).We used data from natural forests and plantations across China to test the following hypotheses:1)the allometric relationships of trees support the predictions of MST on a broad scale;2)the observed deviations from MST predictions are caused by climate,biotic factors,and/or phylogeny;3)abiotic and biotic factors influence allometric relationships in plantations and natural forests differently,and different allometric relationships(i.e.LD,SD,and RD)are affected differently.We related these scaling exponents to geographic climate gradient,successional stage,stand density,leaf form and phenology,and phylogeny.We used mixedeffect models to examine the major factors affecting tree allometries.Results:In natural forests,SD and RD scaling exponents were consistent with MST predictions in primary forests,but were significantly lower in secondary forests.Both SD and RD scaling exponents in plantations had a medium value that fell between those of the secondary and primary forests,despite plantations being similar in species characteristics and age to secondary forests.The SD and RD exponents were significantly affected by factors that are not yet considered in MST,including winter coldness which explained 2.76%–3.24%of variations,successional stage(7.91%–8.20%of variations),density(a surrogate for competition,5.86%–8.54%of variations),and especially phylogeny(45.86%–56.64%of variations explained).However,the LD scaling exponents conformed to MST predictions in primary,secondary,and plantation forests,and was not strongly explained by most factors.Conclusion:MST is only applicable to primary(steadystate)forests,and climate,biotic factors and phylogeny are causes of the observed deviations of allometric relationships from MST predictions.Forest management practices in plantations have a strong influence on tree allometries.LD allometry is more strongly controlled by biophysical constraints than SD and RD allometries,however,the mechanisms behind this difference still need further examinations.

Scaling Theory of Polyelectrolyte Nanogels

The present paper develops the scaling theory of polyelectrolyte nanogels in dilute and semidilute solutions. The dependencies of the nanogel dimension on branching topology, charge fraction, subchain length, segment number, solution concentration are obtained. For a single polyeleetrolyte nanogel in salt free solution, the nanogel may be swelled by the Coulombie repulsion （the so-called polyelectrolyte regime） or the osmotic eounterion pressure （the so-called osmotic regime）. Characteristics and boundaries between different regimes of a single polyelectrolyte nanogel are summarized. In dilute solution, the nanogels in polyeleetrolyte regime will distribute orderly with the increase of concentration. While the nanogels in osmotic regime will always distribute randomly. Different concentration dependencies of the size of a nanogel in polyeleetrolyte regime and in osmotic regime are also explored.

Scaling Theory of Strongly Charged Cylindrical Polyelectrolyte Brushes

Scaling theory of charged cylindrical polyelectrolyte brushes is developed. The dependence of brush thickness on the grafting density, charge fraction, and chain length is analyzed. A full phase diagram is established. Characteristics and boundaries between different regimes of cylindrical polyelectrolyte brushes are summarized. Special attentions are paid to electrostatic interaction induced stiffening and counterion condensation effects. If the Bjerrum length of the solution is larger than the Kuhn length of the polyelectrolyte chains, counterion condensation occurs in the strongly charged polyeleetrolyte brushes. On the contrary, the electrostatic interaction stretches the strongly charged grafted polyelectrolyte chains to their contour length.

Study on Excess Thermodynamic Parameters and Theoretical Estimation of Ultrasonic Velocity Using Scaled Particle Theory in Binary Liquid Mixtures of 2-Methyl-2-propanol and Nitriles at Different Temperatures

Density, ρ, ultrasonic speed, u, and viscosity, η, of binary mixtures of 2-methyl-2-propanol (2M2P) with acetonitrile (AN), propionitrile (PN) and butyronitrile (BN) including those of pure liquids are measured over the entire composition range at temperatures 298.15, 303.15 and 308.15 K. From these experimental data, the excess available volume, E a V , excess free volume, E f V , excess isothermal compressibility, E T β , excess thermal expansion coefficient, E α , and excess internal pressure, E i π , are calculated. The variation of these properties with composition and temperature are discussed in terms of molecular interactions between unlike molecules of the mixtures. It is found that the values of E a V , E f V , E T β and E α are positive and those of E i π are negative for all the mixtures at each temperature studied, indicating the presence of weak interactions between 2M2P and AN/PN/BN molecules. The variations of E a V , E f V , E T β , E α and E i π values with composition indicate that the interactions in these mixtures follow the order: AN<PN<BN, i.e., the 2M2P-nitrile interaction decreases with the increase of alkyl chain length in these nitrile molecules. In addition, the theoretical ultrasonic velocity is calculated using the scaled particle theory and compared with the experimental values.

A Closure for Isotropic Turbulence Based on Extended Scale Similarity Theory in Physical Space

The closure of a turbulence field is a longstanding fundamental problem, while most closure models are introduced in spectral space. Inspired by Chou＇s quasi-normal closure method in spectral space, we propose an analytical closure model for isotropic turbulence based on the extended scale similarity theory of the velocity structure function in physical space. The assumptions and certain approximations are justified with direct numerical simulation. The asymptotic scaling properties are reproduced by this new closure method, in comparison to the classical Batchelor model.

Structural and robustness properties of smart-city transportation networks

The concept of smart city gives an excellent resolution to construct and develop modern cities, and also demands infrastructure construction. How to build a safe, stable, and highly efficient public transportation system becomes an important topic in the process of city construction. In this work, we study the structural and robustness properties of transportation networks and their sub-networks. We introduce a complementary network model to study the relevance and complementarity between bus network and subway network. Our numerical results show that the mutual supplement of networks can improve the network robustness. This conclusion provides a theoretical basis for the construction of public traffic networks, and it also supports reasonable operation of managing smart cities.

Subthreshold behavior of AlInSb/InSb high electron mobility transistors

We propose a scaling theory for single gate Al In Sb/In Sb high electron mobility transistors（HEMTs） by solving the two-dimensional（2D） Poisson equation. In our model, the effective conductive path effect（ECPE） is taken into account to overcome the problems arising from the device scaling. The potential in the effective conducting path is developed and a simple scaling equation is derived. This equation is solved to obtain the minimum channel potential Φdeff,minand the new scaling factor α to model the subthreshold behavior of the HEMTs. The developed model minimizes the leakage current and improves the subthreshold swing degradation of the HEMTs. The results of the analytical model are verified by numerical simulation with a Sentaurus TCAD device simulator.

Modeling of Surface Tension and Viscosity for Non-electrolyte Systems by Means of the Equation of State for Square-well Chain Fluids with Variable Interaction Range

The equation of state(EOS)for square-well chain fluid with variable range(SWCF-VR) developed in our previous work based on statistical mechanical theory for chemical association is employed for the correlations of surface tension and viscosity of common fluids and ionic liquids(ILs).A model of surface tension for multi-component mixtures is presented by combining the SWCF-VR EOS and the scaled particle theory and used to produce the surface tension of binary and ternary mixtures.The predicted surface tensions are in excellent agreement with the experimental data with an overall average absolute relative deviation(AAD)of 0.36%.A method for the calculation of dynamic viscosity of common fluids and ILs at high pressure is presented by combining Eyring’s rate theory of viscosity and the SWCF-VR EOS.The calculated viscosities are in good agreement with the experimental data with the overall AAD of 1.44% for 14 fluids in 84 cases.The salient feature is that the molecular parameters used in these models are self-consistent and can be applied to calculate different thermodynamic properties such as pVT,vapor-liquid equilibrium,caloric properties,surface tension,and viscosity.

A Paradoxical Consistency Between Dynamic and Conventional Derivatives on Hybrid Grids

It has been evident that the theory and methods of dynamic derivatives are playing an increasingly important role in hybrid modeling and computations. Being constructed on various kinds of hybrid grids, that is, time scales, dynamic derivatives offer superior accuracy and flexibility in approximating mathematically important natural processes with hard-to-predict singularities, such as the epidemic growth with unpredictable jump sizes and option market changes with high uncertainties, as compared with conventional derivatives. In this article, we shall review the novel new concepts, explore delicate relations between the most frequently used second-order dynamic derivatives and conventional derivatives. We shall investigate necessary conditions for guaranteeing the consistency between the two derivatives. We will show that such a consistency may never exist in general. This implies that the dynamic derivatives provide entirely different new tools for sensitive modeling and approximations on hybrid grids. Rigorous error analysis will be given via asymptotic expansions for further modeling and computational applications. Numerical experiments will also be given.

A study of the logical model of capital market complexity theories

Analyzes the shortcomings of the classic capital market theories based on EMH and discloses the complexity essence of the capital market. Considering the capital market a complicated, interactive and adaptable dynamic system, with complexity science as the method for researching the operation law of the capital market, this paper constructs a nonlinear logical model to analyze the applied realm, focal point and interrelationship of such theories as dissipative structure theory, chaos theory, fractal theory, synergetics theory, catastrophe theory and scale theory, and summarizes and discusses the achievements and problems of each theory. Based on the research, the paper foretells the developing direction of eomplexity science in a capital market.

Gauge Gravitational Field in a Fractal Space-Time

Considering the fractal structure of space-time, the scale relativity theory in the topological dimension DT = 2 is built. In such a conjecture, the geodesics of this space-time imply the hydrodynamic model of the quantum mechanics. Subsequently, the gauge gravitational field on a fractal space-time is given. Then, the gauge group, the gauge-covariant derivative, the strength tensor of the gauge field, the gauge-invariant Lagrangean, the field equations of the gauge potentials and the gauge energy-momentum tensor are determined. Finally, using this model, a Reissner- Nordstrom type metric is obtained.

Probing the Missing Baryons via kSZ Stacking

Kinetic Sunyaev-Zel＇dovich （kSZ） stacking has great potential to become a powerful probe of missing baryons, due to advances in CMB experiments and galaxy surveys. In this paper, we study kSZ stacking in hydrodynamic simulations with different gastrophysics. We quantify the kSZ stacking signal as a function of halo mass, redshift and projection depth. We compare between different simulations to estimate the impact of gastrophysics such as cooling and supernova feedback. Furthermore, we measure the contribution from warm-hot intergalactic medium （WHIM）, which is believed to be the reservoir for most, if not all, missing baryons. We find that the WHIM contribution is significant, at the level of ~ 10%-70%, depending on the angular separation from the stacked halos and other factors. However, contribution from the intracluster medium along the line of sight is in general non-negligible. This complexity requires more detailed and comprehensive analysis on probing the missing baryons with kSZ stacking.

The distance duality relation test from the ACT cluster and type Ia supernova data

The validity of the cosmic distance-duality （DD） relation is investigated by using 91 measure- ments of the gas mass fraction of galaxy clusters recently reported by the Atacama Cosmology Telescope （ACT） and the luminosity distance from the Union2.1 type Ia supernova （SNIa） sample independent of any cosmological models and the value of the Hubble constant. We consider four different approaches to derive the gas mass function and two different parameterizations of the DD relation, and find that they have very slight influences on the DD relation test and the relation is valid at the la confidence level. We also discuss the constraints on a andβ, which represent the effects of the shapes and colors of the light curves of SNIa, respectively. Our results on a and β are different from those obtained from the ACDM model and the galaxy cluster plus SNIa data.

The application of nonlocal theory method in the coarse-grained molecular dynamics simulations of long-chain polylactic acid

The micro-capsules used for drug delivery are fabricated using polylactic acid（PLA）,which is a biomedical material approved by the FDA.A coarse-grained model of long-chain PLA was built,and molecular dynamics（MD）simulations of the model were performed using a MARTINI force field.Based on the nonlocal theory,the formula for the initial elastic modulus of polymers considering the nonlocal effect was derived,and the scaling law of internal characteristic length of polymers was proposed,which was used to adjust the cut-off radius in the MD simulations of PLA.The results show that the elastic modulus should be computed using nonlinear regression.The nonlocal effect has a certain influence on the simulation results of PLA.According to the scaling law,the cut-off radius was determined and applied to the MD simulations,the results of which reflect the influence of the molecular weight change on the elastic moduli of PLA,and are in agreement with the experimental outcome.

Scaled particle theory for bulk and confined fluids： A review

More than half a century after its first formulation by Reiss, Frisch and Lebowitz in 1959, scaled particle theory(SPT) has proven its immense usefulness and has become one of the most successful theories in liquid physics. In recent years, we have strived to extend SPT to fluids confined in a variety of random porous matrices. In this article, we present a timely review of these developments. We have endeavored to present a formulation that is pedagogically more accessible than those presented in various original papers, and we hope this benefits newcomers in their research work. We also use more consistent notations for different cases. In addition, we discuss issues that have been scarcely considered in the literature, e.g., the one-fluid structure of SPT due to the isomorphism between the equation of state for a multicomponent fluid and that for a one-component fluid or the pure-confinement scaling relation that provides a connection between a confined and a bulk fluid.

Asymmetric competition for light varies across functional groups

Aims Asymmetric competition for light may depress the growth rates(GRs)to different extents for different-sized tree individuals.Various responses of different functional groups to light availability result that tree individuals of different functional groups may experience different competition intensities,e.g.canopy and deciduous species grow faster and demand more light than understory and evergreen species.In this study,we estimated the effects of asymmetric competition for light using individual GRs and explored the effects of asymmetric competition on growth among different functional groups(e.g.canopy vs.understory species and deciduous vs.evergreen species).Methods We measured growth in circumference to determine the radial increments of a total of 2233 stems with diameter at breast height≥5.0 cm in a permanent plot(140×80 m^(2))located in a typical evergreen and deciduous broadleaved mixed forest on Mt Shennongjia,China.All of the measurements were carried out at~6-month intervals every April and October from 2012 to 2014,and biomass of each individual was calculated based on its diameter and species-specific allometry.We then calculated GRs of annual biomass growth(growth between October and the next October).Considering the hypothesis that asymmetric competition for light among trees of different sizes may result in a steeper allometric growth curve with increasing tree size,we further divided the sampled trees into different subsets according to their height,at intervals of 1 m,and then fitted the scaling relationship between the logarithm of the biomass GR(logGR)and the logarithm of diameter(logD)for each height class using standardized major axis regression.Finally,we used simple linear regression to test whether the scaling exponent was related to tree height.The above analyses were conducted for the annual growth of all tree species,canopy species,understory vs.treelets species and deciduous vs.evergreen species.Important findings We observed a concave curve for the relationship between logGR and logD with an increase in the scaling exponent between logGR and logD with increasing tree height.This pattern held for the annual growth of canopy species and deciduous species but not for the annual growth of understory species,treelets or evergreen species.These results suggest that asymmetric competition for light is more important in regulating the GRs of the fast-growing species,such as canopy species and deciduous species,than those of shade-tolerant species,such as understory species,treelets and evergreen species.

Structures and Surface States of Polymer Brushes in Good Solvents:Effects of Surface Interactions

The influence of the surface interaction on the mesoscopic structure of grafted polymers in good solvents has been examined. At high surface coverage, tethered polymers are in the brush state and the parabolic segment density profile is confirmed by self-consistent field theory （SCFT） calculations. It is found that this is a universal behavior for a whole range of surface interactions from complete repulsion to strong attraction. More interestingly, finite surface repulsion may lead to the maximum in the proximal layer of its segment density profile, which is significantly different from both the depletion layer of pure repulsion and the adsorbing layer of attraction. In addition to the brush state on both repulsive and attractive surfaces, three additional surface states were identified by analyzing the scaling behavior of the layer thickness of polymer brushes： the mushroom state on repulsive substrates, the dilute and the semidilute surface states on attractive substrates.