The activation law for one-dimensional maps

The activation dynamics of one-dimensional maps is considered. It is shown that the activation law describing the average time required for attaining a given boundary has the form of the error function (erfc), whereas approximation using the exponential law gives much worse results. In addition, it is demonstrated that linear analysis can be applied to a substantially nonlinear problem.     

The exact theory of one-dimensional quasicrystal deep beams

Without employing ad hoc assumptions, various equations and solutions for quasicrystal beams are deduced systematically and directly from the plane problem of one-dimensional quasicrystals. These equations and solutions can be used to construct the exact theory of deep beams for extension or compression and bending deformation forms. A method for the solution of two-dimensional equations is presented, and with the method the exact theory can now be explicitly established from the general solution of quasicrystals and the Lur’e method. The exact governing equations for beams under transverse loadings are derived directly from the exact beam theory. In three illustrative examples of quasicrystal beams it is shown that the exact or accurate solutions can be obtained by use of the exact theory.     

Estimation of the parameters of one-dimensional maps from chaotic time series

The problem of constructing model maps based on the experimental chaotic time series is considered. A new method of estimation of the model parameters for one-dimensional maps is proposed, which employs a least squares procedure and calculations of the objective function using iterations of the model map in the reverse time. The results of a numerical experiment show that the proposed method provides much more accurate estimates than does the traditional approach at a moderate noise level below a certain threshold. The greater the number of parameters to be evaluated, the higher the threshold and, hence, the broader the domain of high efficiency of the new method.     

Optimization of ergodic averages along squares

We study the question of maximization of non-conventional ergodic averages along square iterates of the doubling map for a characteristic function centred at 1/2, when varying the initial state from the set in which the operator has good asymptotic behaviour.     

Synthesis and applications of one-dimensional semiconductors

Nanoscale inorganic materials such as quantum dots (0-dimensional) and one-dimensional (1D) structures, such as nanowires, nanobelts and nanotubes, have gained tremendous attention within the last decade. Among the huge variety of 1D nanostructures, semiconducting nanowires have gained particular interest due to their potential applications in optoelectronic and electronic devices. Despite the huge efforts to control and understand the growth mechanisms underlying the formation of these highly anisotropic structures, some fundamental phenomena are still not well understood. For example, high aspect-ratio semiconductors exhibit unexpected growth phenomena, e.g. diameter-dependent and temperature-dependent growth directions, and unusual high doping levels or compositions, which are not known for their macroscopic crystals or thin-film counterparts.This article reviews viable synthetic approaches for growing high aspect-ratio semiconductors from bottom-up techniques, such as crystal structure governed nucleation, metal-promoted vapour phase and solution growth, formation in non-metal seeded gas-phase processes, structure directing templates and electrospinning. In particular new experimental findings and theoretical models relating to the frequently applied vapour-liquid-solid (VLS) growth are highlighted. In addition, the top-down application of controlled chemical etching, using novel masking techniques, is described as a viable approach for generating certain 1D structures. The review highlights the controlled synthesis of semiconducting nanostructures and heterostructures of silicon, germanium, gallium nitride, gallium arsenide, cadmium sulphide, zinc oxide and tin oxide. The alignment of 1D nanostructures will be reviewed briefly. Whilst specific and reliable contact procedures are still a major challenge for the integration of 1D nanostructures as active building blocks, this issue will not be the focus of this paper. However, the promising applications of 1D semiconductors will be highlighted, particularly with reference to surface dependent electronic transduction (gas and biological sensors), energy generation (nanomechanical and photovoltaic) devices, energy storage (lithium storage in battery anodes) as well as nanowire photonics.     

ZnO一维纳米材料的制备与表征

首先以乙醇为溶剂,乙酸锌为前驱体,油酸钠为表面修饰剂,采用溶液化学法,制得ZnO纳米粒子。以自制ZnO纳米粒子为基体,通过煅烧方法制备针状ZnO纳米线束。通过紫外-可见吸收光谱(UVVis)、荧光光谱(FL)、透射电子显微镜(TEM)、X射线衍射(XRD)和扫描电子显微镜(SEM)等方法对合成的样品进行表征。结果表明,所合成ZnO纳米粒子样品UV-Vis吸收光谱在355nm给出ZnO纳米粒子的特征吸收峰,FL光谱显示在400和550nm处产生荧光发射。ZnO纳米粒子尺寸约为5nm且粒径分布较窄。自制ZnO纳米粒子样品经500℃煅烧后可得到针状ZnO纳米线束。纳米线为六方晶系纤锌矿结构ZnO单晶纳米线,长度约为10μm,直径约为100nm,长径比约为100,且具有良好的紫外发光性能。     

Synthesis and characterization of one-dimensional MgO nanostructures

Magnesium oxide (MgO) nanowire arrays, nanoribbons, two- and three-dimensional network like nanostructures were prepared by the simple thermal evaporation of Mg powder with and without using catalyst at a relatively low temperature. The non-catalytic approaches favor the formation of network like nanoforms whereas the catalytic approaches favors the formation of one-dimensional nanowire arrays and quasi one-dimensional nanoribbons depending on the temperature and vapor concentrations of the growth site. The diameter and length of the MgO network like columns varied within 40-50 nm and approximately 200 nm respectively. The MgO nanowires produced by the catalytic approach had diameter within 20-30 nm and length approximately 2 microm. Whereas the widths of the nanoribbons varied within 50-100 nm and their length were of the order of a few hundred micrometers. The nanoforms were single crystalline and cubic in phase. The products were characterized by the X-ray diffraction study, energy dispersive analysis of X-ray study, scanning and transmission electron microscopy, and photoluminescence measurements to explore the structural, compositional, morphological, and physical properties of the MgO nanoforms.     

Nanoscale friction and wear maps

Friction and wear are part and parcel of all walks of life, and for interfaces that are in close or near contact, tribology and mechanics are supremely important. They can critically influence the efficient functioning of devices and components. Nanoscale friction force follows a complex nonlinear dependence on multiple, often interdependent, interfacial and material properties. Various studies indicate that nanoscale devices may behave in ways that cannot be predicted from their larger counterparts. Nanoscale friction and wear mapping can help identify some 'sweet spots' that would give ultralow friction and near-zero wear. Mapping nanoscale friction and wear as a function of operating conditions and interface properties is a valuable tool and has the potential to impact the very way in which we design and select materials for nanotechnology applications.     

Computer protocol and torus maps

We investigate the dynamics of maps and flows which arise from a class of models of closed queueing networks in computer science theory. The network consists of n+/ servers, one of which is a central server with a queue of size n-1. A protocol or scheduling discipline must be specified in this server to define the queueing network. The standard model gives rise to a flow on an n-torus. We consider the service protocols first in-first out (FIFO) and last in-first out (LIFO) in dimension three, for which the state spaces are modifications of a 3-torus. We present a sufficient condition on the time it takes each call to complete one cycle for the FIFO protocol which guarantees that the set of periodic orbits which involve no waiting in the queue is a global attractorfor the associated semi-flow. We also investigate the dynamics for the LIFO service protocol via a return map derived from the associated area preserving flow.     

Constrained dynamics of geometrically exact beams

 Geometrically exact beams are regarded from the outset as constrained mechanical systems. This viewpoint facilitates the discretization in space and time of the underlying continuous beam formulation without using rotational variables. The present semi-discrete beam equations assume the form of differential–algebraic equations which are discretized in time. The resulting energy–momentum scheme satisfies the algebraic constraint equations on both configuration and momentum level. Dedicated to the memory of Prof. Mike Crisfield, for his cheerfulness and cooperation as a colleague and friend over many years.     

Magnetothermo-emf of a one-dimensional superlattice

The longitudinal magnetothermo-emf of a one-dimensional semiconductor superlattice has been studied in the quasi-classical limit (τ⁻¹ ≪ Ω ≪ μ, where τ is the charge carrier relaxation time, Ω is the cyclotron frequency, and μ is the chemical potential). It is established that oscillations caused by the Landau quantization are modulated by oscillations related to a finite width of the conduction band. Conditions under which such a modulation is especially clearly manifested are determined.     

准一维纳米材料的研究现状

自从碳纳米管被发现以后,一维纳米材料作为纳电子器件的重要组成部分,其合成、材料物性以及应用已经引起了人们的广泛重视.本文从一维纳米材料的制备入手,讨论了一维纳米材料的的制备方法及其各自特点,分析了一维纳米材料形成机制,并对其表征方法做了简单的介绍,根据其特殊性能分析其潜在应用.     

Numerical approximation of one-dimensional consolidation

A generalized finite difference scheme is developed to represent the one-dimensional consolidation process. The difference equations are derived from integral balance equations which represent the soil as a mixture of two constituents. No restrictions are placed on the soil constitutive properties or stratigraphy. An approach to stability analysis for the scheme is outlined, and an example problem is presented.     

An efficient ergodic simulation of multivariate stochastic processes with spectral representation

A simulation formula to generate stationary multivariate stochastic processes is derived from the Fourier-Stieltjes integral of spectral representation. It is proved that the proposed algorithm generates ergodic sample functions in the mean value and in the correlation when the sample length is equal to one period (the generated sample functions are periodic). The algorithm is very efficient computationally since it takes advantage of the fast Fourier transform technique. The simulation of longitudinal wind velocity fluctuations and the simulation of longitudinal and vertical wind fluctuating components on a bridge deck are performed. It has been noted that there are good agreements between the temporal and target auto-/cross-correlation functions of simulated wind velocities.     

Analysis of Families of Curves

A systematic approach is presented for fitting empirical expressions to data depending on two variables. The problem can also be described as the simultaneous fitting of a family of curves depending on a parameter.The proposed method reduces a surface fitting problem to that of fitting a few functions of one variable each. First, the surface is expressed in terms of these one-variable functions, and using an extension of two-way analysis of variance, the accuracy of this fit is assessed without having to determine, at this point, the nature of the one-variable functions. Then, the one-variable functions are fitted by customary curve-fitting procedures.For illustration, the method is applied to two sets of experimental data.