Thermo-optical response of layered Bi nanostructures produced by pulsed laser deposition

This work reports optical transmission changes in layered Bi nanostructures (NSs) upon heating-cooling cycles up to temperatures above the melting temperature. The nanostructured films prepared by pulsed laser deposition consist of Bi NSs with different characteristic sizes that are organised in layers and embedded in an amorphous Al₂O₃ host. The spectral dependence of the optical transmission as well as its changes upon heating are reported. The combination of Bi NSs layers with more than one characteristic size allows controlling the width of the melting-solidification transition. Eventually, it is shown how a multiple temperature thermo-optical film can be designed and prepared.     

Elemental surface enrichment in flame synthesis: A mechanism associated with particle melting-solidification

Elemental surface enrichment is important for functionalities of flame-synthesized particle materials, but its mechanism is poorly understood. In this paper, a mechanism associated with particle melting-solidification is proposed based on an experimental study. Y₂O₃:Eu particles were generated by flame assisted spray pyrolysis (FASP), using H₂/O₂ flames or H₂/air flames. The particles were analyzed by transmission electron microscopy (TEM), X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), and X-ray photoelectron spectroscopy (XPS). H₂/O₂ flames resulted in particles with Eu surface enrichment, i.e. the surface Eu concentration was several times higher than the overall Eu concentration; there was no elemental surface enrichment in particles from H₂/air flames. The Eu surface enrichment in H₂/O₂ flames was attributed to elemental partitioning during solidification of molten Y₂O₃:Eu particles; in H₂/air flames the particles did not melt and hence there was no elemental surface enrichment. The findings of this study suggest that elemental surface enrichment may be a common phenomenon for binary metal oxide particles that experience melting-solidification. Such particles should be examined for elemental surface enrichment, both for understanding their functionality and for their potential biological effects.     

Reentrant layering in rare gas adsorption: preroughening or premelting?

The reentrant layering transition found in rare gas adsorption on solid substrates has conflictually been explained in terms either of preroughening (PR) or of top layer melting-solidification phenomena. We obtain adsorption isotherms of Lennard-Jones particles on an attractive substrate by off lattice grand canonical Monte Carlo simulation, and reproduce reentrant layering. Microscopic analysis confirms a transformation of the top surface layer from solid to quasiliquid across the transition. At the same time, however, the surface coverage is found to switch from close to one to close to half, the latter indicating a disordered flat surface and establishing PR as the underlying mechanism. We conclude that top layer melting can trigger PR. In turn, PR appears to act as the threshold transition for surface melting in rare gas solids.     

Optical contrast by laser-induced phase changes: Real time optical measurement of fast transformation times

Real time optical measurements are used to analyse two different kinds of phase changes which generate optical contrast in (In₄₃Sb₅₇)₈₇Ge₁₃ thin films. Amorphous to crystalline and amorphous to amorphous structural transformations are induced by pulsed laser irradiation in micron-sized regions. A two beam configuration is used to follow the evolution of the optical properties of the films in real time. It is shown that real time optical measurements provide a unique tool to analyse laser-induced fast structural transformations leading to optical contrast. Processes occurring via relaxation, solid state crystallization or melting-solidification are clearly distinguished. From the analysis of the optical transients the minimum transformation times are directly determined.On Sabbatical leave from IBM Almaden Research Center, San Jose, CA, USA     

Enhanced triple-quantum excitation in 13C magic-angle spinning NMR

We describe a new method for exciting triple-quantum coherences in 13C-labelled powder samples under MAS. The proposed method combines selective double-quantum excitation with rotational resonance and frequency-selective composite pulses. The spin dynamics of this new method are described theoretically. Numerical calculations of the spin dynamics are compared to experimental results on fully 13C-labelled L-alanine. The observed triple-quantum filtering efficiency is around 10% for the most intense spectral peak. The method is also demonstrated on other fully 13C-labelled compounds, including a uniformly 13C-labelled amino acid.     

The study of fractal correlation method in the displacement measurement and its application

The classical digital speckle, or digital image, correlation method of deformation measurement is based on gray level correlation between unformed and deformed digital images. The pattern of artificial random speckles and the natural textures on some object's surfaces have fractal characteristics, and their fractal dimensions represent both gray and morph information. Furthermore, the fractal dimensions are stable feature parameters of the patterns. The digitized images of the patterns are confirmed to be also fractals. By this fact, a new method of displacement measurement is developed in the paper, based on the fractal dimensions correlation. The in-plane displacement fields of a body can be acquired. In order to verify the validity of the new method, an experiment has been designed and the results have been compared with those obtained from the classical digital image correlation method. The validity of the new method is not less than that of classical method. Further discussions about the traits and the developing vista of the method are given at the end.     

Extraction current transients: new method of study of charge transport in microcrystalline silicon

The transport properties of microcrystalline silicon, namely, mobility and conductivity, are investigated by a new method, for which the simple theory as well as numerical modeling is presented. The basic idea of the new method is verified on amorphous hydrogenated silicon by comparison with the widely used time-of-flight method. Contrary to time of flight, the new method can be used even for relatively conductive materials. Preliminary results on microcrystalline silicon clearly indicate the critical role of amorphouslike tissue in transport in microcrystalline silicon.     

A new integral equation method for direct electromagnetic scattering in homogeneous media and its numerical confirmation

In this paper, we derive a new integral equation method for direct electromagnetic scattering in homogeneous media and present a numerical confirmation of the new method via a computer simulation. The new integral equation method is based on a paper written by DeSanto [1], originally for scattering from an infinite rough surface separating homogeneous dielectric half-spaces. Here, it is applied to a bounded scatterer, which can be an ohmic conductor or a dielectric, with some simplification of the continuity conditions for the fields. The new integral equation method is developed by choosing the electric field and its normal derivative as boundary unknowns, which are not the usual boundary unknowns. The new integral equation method may provide significant computational advantages over the standard Stratton-Chu method [2] because it leads to a 50% sparse, rather than 100% dense, impedance (collocation) matrix. Our theoretical development of the new integral equation method is exact.     

A new volume-of-fluid method with a constructed distance function on general structured grids

A second-order volume-of-fluid method (VOF) is presented for interface tracking and sharp interface treatment on general structured grids. Central to the new method is a second-order distance function construction scheme on a general structured grid based on the reconstructed interface. A novel technique is developed for evaluating the interface normal vector using the distance function. With the normal vector, the interface is reconstructed from the volume fraction function via a piecewise linear interface calculation (PLIC) scheme on the computational domain. Several numerical tests are conducted to demonstrate the accuracy and efficiency of the present method. In general, the new VOF method is more efficient than both the high-order level set and the coupled level set and volume-of-fluid (CLSVOF) methods. The results from the new method are better than those from the benchmark VOF method, particularly in the under-resolved regions, and are comparable to those from the CLSVOF method. Breaking waves over a submerged bump and around a wedge-shaped bow are simulated to demonstrate the application of the new method and sharp interface treatment in a two-phase flow solver on curvilinear grids. The computational results are in good agreement with the available experimental measurements.     

New Method for 3D Transient Eddy Current Field Calculation and Its Application in Magneto-Acoustic Tomography

A new method of 3 D transient eddy current field calculation is proposed. The Maxwell equations with time component elimination(METCE) are derived under the assumption of magnetic quasi static approximation, especially for the sample of low conductivity. Based on METCE, we deduce a more efficient reconstruction algorithm of a3 D transient eddy current field. The computational burden is greatly reduced through the new algorithm, and the computational efficiency is improved. This new algorithm decompounds the space-time variables into two individual variables. The idea is to solve the spatial vector component firstly, and then multiply it by the corresponded time component. The iterative methods based on METCE are introduced to recover the distribution of conductivity in magneto-acoustic tomography. The reconstructed images of conductivity are consistent with the original distribution, which validate the new method.     

A new method of aperture synthetizing in digital holography

This paper proposes a new method of aperture synthetizing in digital holography based on the principle of holography. In the new method aperture synthetizing is achieved by reconstructing each sub-hologram respectively, firstly, moving each reconstructed wave field referred to the benchmark reconstructed wave field according to the relationship between spacial motion and frequency shift, and finally splicing them by using superposition. Two different recording ways, using plane wave to record and using spherical wave to record, are analyzed, and their moving formula is deduced, too. Simulation and experiment are done. The results show that in comparison with the traditional method of aperture synthetizing in digital holography, the new method can decrease calculation and save reconstructed time obviously which has better applicability.     

Density of states of grain boundaries in silicon

A new spectroscopic method for the evaluation of the density of states in semiconductor grain boundaries is presented. The method is based on a measurement of the intensity and wavelength dependence of the zero-bias photo capacitance of grain boundaries under sub-bandgap illumination. Experiments are performed on p-type silicon bicrystals. Bandtails and states close to midgap are observed.     

Symmetry of Chaos and Order in Systems with Continuously Varying Structure of Dynamic Elements

The Fibonacci method is considered for stationary distributions. The initial postulates of this method are opposite to the postulates of statistical mechanics. The inapplicability of the hypothesis on identical dynamic particles is demonstrated on the example of the stationary state of a macromolecule in a thermostat. A new model of the stationary state of a substance is constructed based on the equality of chaos and order measures specified in terms of variables of three classes. The limiting transition from the new model to the well-known models is given. The law of evolution is expressed in terms of the symmetry of chaos and order.     

Controlling projective synchronization in coupled chaotic systems

In this paper, a new method for controlling projective synchronization in coupled chaotic systems is presented. The control method is based on a partially linear decomposition and negative feedback of state errors. Firstly, the synchronizability of the proposed projective synchronization control method is proved mathematically. Then, three different representative examples are discussed to verify the correctness and effectiveness of the proposed control method.     

Rendering moving sound with the doppler effect in sound space

In this report, a new rendering method of a moving sound with the Doppler effect is proposed. In the conventional rendering method of moving sound, Head Related Impulse Responses (HRIRs) are simply changed according to a sound position. However, the Doppler effect cannot be added to a sound in this method. The pitch of a sound object must be controlled using some other rendering method when a sound object moves at high speed. In our method, each HRIR is divided into two components, such as an initial delay and a main wave form. Two initial delays of both right and left ears are recalculated, respectively, based on relative speeds and a propagation path. These new initial delays are used in rendering. Therefore, the Doppler effect is added to a sound automatically only when a sound position is set in this algorithm. Details related to this algorithm are discussed in this report.     

Multipole-based modal analysis of gate-defined quantum dots in graphene

A new numerical method based on the multipoles of the Dirac equation is presented for rigorous and fast analysis of electron scattering from gate-defined structures in graphene. The new method is used to study the strongly bound states and the weakly bound states of a circular quantum dot. The accuracy of the obtained results is then verified by the T-matrix method. Furthermore, we characterize the resonances of elliptical gate-defined quantum dots and compare these resonances with the strongly bound states of circular dots. The effects of coupling between two quantum dots are also investigated.     

RF腔光阴极注入器中热发射度的测量研究

论文介绍RF腔光阴极注入器中热发射度的测量方法，在注入器中有三个因素影响热发射度的测量，它们是：射频场效应、空间电荷效应和发射度测量误差. 在注入器出口处，电子束发射度由：热发射度、射频场效应引起的发射度增长和空间电荷效应的发射度增长三部分组成. 论文从注入器中发射度增长理论和模拟出发，给出了一个能够消除射频场效应和空间电荷效应的热发射度测量方法.     

A multivariate data analysis approach towards vibration analysis and vibration-based damage assessment:: Application for delamination detection in a composite beam

This paper introduces a novel methodology for structural vibration analysis and vibration-based monitoring which utilises a special type of Principal Components Analysis (PCA), known as Singular Spectrum Analysis (SSA). In this study the methodology is introduced and demonstrated for the purposes of damage assessment in structures using their free decay response. The method?s damage assessment properties are first demonstrated on a numerical example for a two degree-of-freedom (2DoF) spring–mass and damper system with nonlinear stiffness. The method is then applied to an experimental case study of a composite laminate beam. The method is based on the decomposition of the frequency domain structural variation response using new variables, the Principal Components (PCs). Only a certain number of new variables are used to approximate the original vibration signal with very good accuracy. The presented results demonstrate the potential of the method for vibration based signal reconstruction and damage diagnosis. The healthy and the different damaged scenarios are clearly distinguishable in the new space of only two reconstructed components where a strong clustering effect is observed.     

Fluctuations in the Bose Gas with Attractive Boundary Conditions

In this paper limiting distribution functions of field and density fluctuations are explicitly and rigorously computed for the different phases of the Bose gas. Several Gaussian and non-Gaussian distribution functions are obtained and the dependence on boundary conditions is explicitly derived. The model under consideration is the free Bose gas subjected to attractive boundary conditions, such boundary conditions yield a gap in the spectrum. The presence of a spectral gap and the method of the coupled thermodynamic limits are the new aspects of this work, leading to new scaling exponents and new fluctuation distribution functions.     

A High-Order Immersed Boundary Method for Acoustic Wave Scattering and Low-Mach Number Flow-Induced Sound in Complex Geometries

A new sharp-interface immersed boundary method based approach for the computation of low-Mach number flow-induced sound around complex geometries is described. The underlying approach is based on a hydrodynamic/acoustic splitting technique where the incompressible flow is first computed using a second-order accurate immersed boundary solver. This is followed by the computation of sound using the linearized perturbed compressible equations (LPCE). The primary contribution of the current work is the development of a versatile, high-order accurate immersed boundary method for solving the LPCE in complex domains. This new method applies the boundary condition on the immersed boundary to a high-order by combining the ghost-cell approach with a weighted least-squares error method based on a high-order approximating polynomial. The method is validated for canonical acoustic wave scattering and flow-induced noise problems. Applications of this technique to relatively complex cases of practical interest are also presented.