Formation of a diamond-like carbon film by magnetron sputtering of a graphite target under radiation flux from a black-body model

A method of depositing a film (under a radiation flux from a high-temperature black-body model) by magnetron sputtering of a graphite target has been implemented. The elemental composition and structure of deposited films have been analyzed by X-ray photoelectron spectroscopy and characteristic electron-energy-loss spectroscopy. The investigations have shown that chemically pure diamond-like films can be formed at a radiation-flux density no less than 1.5 × 10^?4 W/m² in the spectral range of 170–255 nm.     

Reflection electron-energy-loss spectroscopy of Fe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Si<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript> thin films

The values of the product of the inelastic mean free path and the differential cross section for inelastic scattering of electrons have been determined from the reflection electron-energy-loss spectra of thin films of the Fe _x Si_{1 − x} system (0 ≤ x ≤ 1). A new approach to the quantitative analysis of components in such composite media is proposed.     

Fabrication and characterization of nanopore-based electrodes with radii down to 2 nm

We report on the fabrication and characterization of gold nanoelectrodes with carefully controlled nanometer dimensions in a matrix of insulating silicon nitride. A focused electron beam was employed to drill nanopores in a thin silicon nitride membrane. The size and shape of the nanopores were studied with high-resolution transmission electron microscopy and electron-energy-loss two-dimensional maps. The pores were subsequently filled with gold, yielding conically shaped nanoelectrodes. The nanoelectrodes were examined by atomic and electrostatic force microscopy. Their applicability in electrochemistry was demonstrated by steady-state cyclic voltammetry. Pores with a radii down to 0.4 nm and electrodes with radii down to 2 nm are demonstrated.     

Production and characterization of single-crystal FeCo nanowires inside carbon nanotubes

We describe the synthesis of novel monocrystalline FeCo nanowires encapsulated inside multiwalled carbon nanotubes (MWNTs). These FeCo nanowires exhibit homogeneous Fe and Co concentrations and do not contain an external oxide layer due to the presence of insulating nanotube layers. The method involves the aerosol thermolysis of toluene-ferrocene-cobaltocene solutions in inert atmospheres. The materials have been carefully characterized using state-of-the-art high-resolution transmission electron microscopy (HRTEM), electron-energy-loss spectroscopy (EELS), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), electron diffraction, HREELS-STM elemental mapping, X-ray powder diffraction, and SQUID magnetometry. We noted that the formation of FeCo alloys occurs at relatively low pyrolytic temperatures (e.g., 650-750 degrees C). These single-crystal nanowires, which have not been reported hitherto, always exhibit the FeCo (110) plane parallel to the carbon nanotube axis. The FeCo nanomaterials have shown large coercive fields at room temperature (e.g., 900 Oe). We envisage that these aligned ferromagnetic nanowires could be used in the fabrication of high-density magnetic storage devices and magnetic composites.     

Surface Dielectric Response of Collective Plasmon Excitations in C60 Fullerite

The paper begins with a review of available observations from electron-energy-loss spectroscopy (EELS) on the excitation of multipolar plasmons in C₆₀. With these observations in the background, an electrodynamic formalism is developed for computing the response of collective plasma oscillations in a fullerite film subject to an external electric field. This formalism allows us to construct the dielectric response function relevant for applications to EELS in specular-reflection geometry. The only input required by the theory is a set of dynamical multipolar polarizabilities of an isolated molecule, which could be provided by a separate theory but which we simulate here by an empirical model consisting of a dielectric spherical shell. The surface loss function is computed for an fcc (111) film composed of such dielectric shells. Comparison with the few available experimental data indicates that quadrupole and higher-multipolar plasmons in fullerites contribute significantly to the long-range inelastic scattering mechanisms that lead to the reflection EELS spectrum.     

Surface Dielectric Response of Collective Plasmon Excitations in C60 Fullerite

The paper begins with a review of available observations from electron-energy-loss spectroscopy (EELS) on the excitation of multipolar plasmons in C₆₀. With these observations in the background, an electrodynamic formalism is developed for computing the response of collective plasma oscillations in a fullerite film subject to an external electric field. This formalism allows us to construct the dielectric response function relevant for applications to EELS in specular-reflection geometry. The only input required by the theory is a set of dynamical multipolar polarizabilities of an isolated molecule, which could be provided by a separate theory but which we simulate here by an empirical model consisting of a dielectric spherical shell. The surface loss function is computed for an fcc (111) film composed of such dielectric shells. Comparison with the few available experimental data indicates that quadrupole and higher-multipolar plasmons in fullerites contribute significantly to the long-range inelastic scattering mechanisms that lead to the reflection EELS spectrum.     

Far-ultraviolet reflectance measurements and optical constants of unoxidized aluminum films

The far-UV reflectance of thin unoxidized aluminum films prepared and maintained in ultra-highvacuum conditions was measured versus the angle of incidence, and the complex refractive index was obtained from those measurements on several wavelengths from 82.6 to 113.5 nm. Measurements were made on two perpendicular planes of incidence to deal with the unknown of the polarization state of the radiation beam. The surface roughness was characterized by atomic force microscopy. The refractive index is obtained for the first time, to our knowledge, from direct optical measurements in this spectral range. Current results match well the former values in the literature that were calculated through the Kramers-Kronig analysis by using in the above interval reflectances estimated from electron-energy-loss spectra and from optical measurements on surfaces of unstated roughness.     

Aluminum. I. Measurement of the relative enthalpy from 273 to 929 K and derivation of thermodynamic functions for Al(s) from 0 K to Its melting point

The relative enthalpy of pure, polycrystalline aluminum (NBS Standard Reference Material 44f, for the freezing point of aluminum on IPTS-68) has been measured over the temperature range 273 to 929 K. The enthalpy measurements were made in a precision isothermal phase-change calorimeter and are believed to have an inaccuracy not exceeding 0.2%. Pt-10Rh alloy and quartz glass were used as the encapsulating materials. The enthalpy data for Al(s) and SiO₂(l) have been fitted by the method of least squares with cubic polynomial functions of temperature. Heat capacity data for Al(s), derived from these polynomials, have been smoothly merged using a spline technique to the most reliable low-temperature heat capacity data for Al(s) below 273 K. The merged data are compared with corresponding data from the literature as well as with published critical compilations of heat capacity data for Al(s). A new table of thermodynamic functions for Al(s) has been derived. A theoretical interpretation of the results apears in the following paper.     

Uniform rational approximation of functions of several variables

We present a program which has given excellent results for uniform approximation of functions by polynomials, rational functions, generalized polynomials, and generalized rational functions. The algorithm is described in detail and several examples are discussed. The approximation is done over a finite point set, which is commonly a set of real numbers or points in the plane (in the latter case we are doing what is often known as surface fitting). Input to and output from the program is in tabular form. The method used is a linear programming approach known as the differential correction algorithm, which has been shown by several authors to always converge in theory (quadratically in some situations). In practice, we have obtained convergence in nearly every case, and quadratic convergence in most cases. The program can also be used for simultaneous approximation of several functions.     

Argon+carbon dioxide gaseous mixture viscosities and anisotropic pair potential energy functions

The viscosities of pure gaseous carbon dioxide and argon+carbon dioxide mixtures have been measured with a capillary flow viscometer. The viscosities are relative to those of argon, in the temperature range 213 to 353 K, and considered accurate to ±0.7%. The pure-component viscosities agree closely with previous measurements. The mixture viscosities are used to calculate interaction viscosities and binary diffusion coefficients, which are compared with previous measurements. Interaction viscosities have been calculated, by use of the Mason-Monchick approximation, from the anisotropic pair potential energy functions for the unlike interaction proposed by Pack and his co-workers and by Hough and Howard. Comparison of these calculated interaction viscosities with those derived from our experiments and the higher-temperature measurements of Hobley, Matthews, and Townsend proves to be a powerful discriminant for the proposed anisotropic potential functions.Paper dedicated to Professor Joseph Kestin.     

Temperature distributions in semi-infinite and finite-thickness media as a result of absorption of laser light

A time-domain method is used to derive simple expressions for temperature distributions within media heated by a moving laser beam with a Gaussian power density profile. Various medium-absorption functions are considered. The solutions are given as single integrals with respect to time of simple functions. The expressions can be applied to multilayer media consisting of layers with different optical (light-absorbing) properties, provided that the layers have similar thermal properties. A number of optical recording examples have been examined in detail, and the results compared with those obtained by use of a more general (fast-Fourier-transform-based) approach.     

Theory and Applications of Dynamic Laser Speckles Due to In-plane Object Motion

The dynamic behaviour of laser speckle caused by uniform in-plane motion of a diffuse object has been studied by deriving the cross-correlation functions of the complex disturbance and the intensity in a field where the speckle is observed. The expressions for the diffraction and the image fields are calculated from general formulae for a linear coherent system. On the basis of these functions two characters in the dynamic behaviour of speckle, a bodily translation and a gradual change in structure, are discussed quantitatively. The velocity of the translation and the rate of the structure change have been derived. As applications of the relations obtained several new methods have been proposed for measuring pattern correlations, MTF of imaging systems, in-plane velocity of diffuse objects, and eye accommodation state.     

Numerical simulation of bi-material interfacial cracks using EFGM and XFEM

In this paper, bi-material interfacial cracks have been simulated using element free Galerkin method (EFGM) and extended finite element method (XFEM) under mode-I and mixed mode loading conditions. Few crack interaction problems of dissimilar layered materials are also simulated using extrinsic partition of unity enriched approach. Material discontinuity has been modeled by a signed distance function whereas strong discontinuity has been modeled by two functions i.e. Heaviside and asymptotic crack tip enrichment functions. The stress intensity factors for bi-material interface cracks are numerically evaluated using the modified domain form of interaction integral. The results obtained by EFGM and XFEM for bi-material edge and center cracks are compared with those available in literature. In order to check the validity of simulations, the results have been obtained for two different ratio of Young’s modulus.     

Development of high-order manifold method

The Manifold Method of Material Analysis (MM) with high-order displacement functions has been derived based on triangular meshes for the requirement of high accurate calculations from practical applications. The matrices of equilibrium equations for the second-order MM have been given in detail for program coding. The derivation of the method is made by means of approximation theory and very few new mathematical concepts are used in this paper. So, it may be understood by most engineering researchers. By close comparison with widely used Finite Element Method, the advantages of MM can be seen very clearly in the following aspects: (1) the capability of processing large deformation and handing discontinuities like block oriented Discontinuous Deformation Analysis method; (2) making element meshes easily and (3) using high-order displacement functions easily. The C program codes for the second-order MM has been developed, and it has been applied to the example of a beam bending under a central point loading. The calculated results are quite good in agreement with theoretical solutions. By contrast, the results calculated for the same model by use of the original first-order MM are far from the theoretical solutions. Therefore, it is important and necessary to develop high-order Manifold Method for the complicated deformation problems. © 1998 John Wiley & Sons, Ltd.     

CLASSICAL SOLUTION SHAPE FUNCTIONS IN THE FINITE ELEMENT ANALYSIS OF CIRCULAR AND ANNULAR PLATES

The objective of this work is to present a new method for the dynamic and static analysis of thin, elastic, isotropic, non-uniform circular and annular plates. The method is a combination of plate theory and finite element analysis. The plate is divided into one circular and many annular finite elements. The displacement functions are derived from Sanders' classical plate theory. These displacement functions satisfy the convergence criteria of the finite element method. The matrices for mass and stiffness are determined by precise analytical integration. A computer programme has been developed, the convergence criteria have been established, and the natural frequencies and vibration modes have been computed for different cases. The results obtained reveal that the frequencies calculated by this method are in good agreement with those obtained by other authors. © 1997 by John Wiley & Sons, Ltd.     

Elastic and inelastic scattering of 59.54 keV gamma rays

Cross sections for the elastic scattering of 59.54 keV gamma rays through 141° by Al, Cu, Mo, Yb, Ta, Au and Pb have been accurately determined using a Si(Li) detector. The values of the cross sections have been obtained by a normalization technique based on a comparison with the Compton scattering from the essentially free electrons from an Al scatterer. For the lower-Z elements Al, Cu and Mo the experimental cross sections are more or less in agreement with the form-factor predictions as well as the S-matrix calculations. For the heavier elements Ta, Au and Pb the experimental results deviate strongly from the form-factor values but agree favourably with the S-matrix values. As a by-product, incoherent scattering functions have been evaluated for Cu, Mo and Yb. Also, a clear indication has been obtained for resonant Raman scattering in the case of Yb.     

Genetic algorithm with adaptive and dynamic penalty functions for the selection of cleaner production measures: a constrained optimization problem

This paper presents a new approach of genetic algorithm (GA) to solve the constrained optimization problem. In a constrained optimization problem, feasible and infeasible regions occupy the search space. The infeasible regions consist of the solutions that violate the constraint. Oftentimes classical genetic operators generate infeasible or invalid chromosomes. This situation takes a turn for the worse when infeasible chromosomes alone occupy the whole population. To address this problem, dynamic and adaptive penalty functions are proposed for the GA search process. This is a novel strategy because it will attempt to transform the constrained problem into an unconstrained problem by penalizing the GA fitness function dynamically and adaptively. New equations describing these functions are presented and tested. The effects of the proposed functions developed have been investigated and tested using different GA parameters such as mutation and crossover. Comparisons of the performance of the proposed adaptive and dynamic penalty functions with traditional static penalty functions are presented. The result from the experiments show that the proposed functions developed are more accurate, efficient, robust and easy to implement. The algorithms developed in this research can be applied to evaluate environmental impacts from process operations.     

An investigation of the possible interaction mechanisms for Si(Li) and Ge detector response functions by Monte Carlo simulation

Simple physical mechanisms implemented by either analog Monte Carlo simulations or analytical models have been used to investigate the Si(Li) and Ge detector response functions for X- and gamma rays, respectively. The mechanisms investigated include the various possible combinations of partial losses of photoelectric and Auger electrons from the detector surfaces and complete losses of the various photons involved such as the Si K X-ray, the 0.511 MeV annihilation photons, and single or multiple Compton scattered photons. The most probable interaction mechanisms for each detector response function feature are identified and the simple analytical functions that have been used in the past are justified.     

The prediction of the excess functions of liquid mixtures using a modified hard-sphere equation of state

The two parameter hard-sphere equation of state used by Snider and Herrington to calculate excess functions for mixtures of condensed gases near their boiling points has been modified to take account of the fact that over a range of temperature the parameters are not constant. The parameter which represents the size of the molecules has been treated as a function of volume, while that associated with the intermolecular energy of attraction has been treated as a function of temperature. Excess functions calculated using the modified equation in general show improved agreement with the experimental values. Moreover the new equation has been used to predict the excess functions of binary mixtures of condensed gases over wide ranges of temperature and pressure, both for systems which have already been partially studied experimentally and for others (for example, fluorine + argon) for which no data yet exist.     

A concurrent model reduction approach on spatial and random domains for the solution of stochastic PDEs

A methodology is introduced for rapid reduced‐order solution of stochastic partial differential equations. On the random domain, a generalized polynomial chaos expansion (GPCE) is used to generate a reduced subspace. GPCE involves expansion of the random variable as a linear combination of basis functions defined using orthogonal polynomials from the Askey series. A proper orthogonal decomposition (POD) approach coupled with the method of snapshots is used to generate a reduced solution space from the space spanned by the finite element basis functions on the spatial domain. POD methods have been extremely popular in fluid mechanics applications and have subsequently been applied to other interesting areas. They have been shown to be capable of representing complicated phenomena with a handful of degrees of freedom. This concurrent model reduction on the random and spatial domains is applied to stochastic partial differential equations (PDEs) in natural convection processes involving randomness in the porosity of the medium and the Rayleigh number. The results indicate that owing to the multiplicative nature of the concurrent model reduction, extremely large computational gains are realized without significant loss of accuracy. Copyright © 2005 John Wiley & Sons, Ltd.