[en] Attenuation of electromagnetic waves by a random distribution of pair-correlated dielectric spheres is studied as a function of frequency and volume concentration of spheres. The main aim of this paper is to compare theoretical results obtained using a self-consistent multiple-scattering formulation and measured values of attenuation for latex spheres in water. The agreement between theory and experiment is very good

[en] In electromagnetic heating of ceramic materials like Al₂O₃, ZrO₂, and MgO, the heating rate depends on their ion migration losses, which tend to increase at low frequencies and as the temperature is raised. The frequency and temperature-dependent loss factors of these materials can be qualitatively described using the Maxwell-Boltzmann or the Bose-Einstein distribution function in conjunction with the Debye relaxation theory. Quantitatively, some proposed modeling constant can be determined by curve-fitting various measurements of ceramic materials on loss tangent versus a wide range of temperature at different frequencies reported by Westphal and Sils

[en] A rigorous treatment of the scattering of atoms by a stationary periodic hard wall in (n+1) dimensions is presented using the T-matrix approach. The normalized Fourier expansion of the surface field used in this formalism is shown to be computationally superior to the GR method of Garcia and the technique used by Goodman. This improvement comes because the surface field representation used here allows one to bypass the restrictions of the Rayleigh hypothesis

[en] This paper is concerned with a theoretical study of a near surface flaw in an immersion tank experiment. The formulation is based on the use of the T-matrix to characterize the scatter response and transmission and reflection matrices to characterize the effect of the interface. Expressions are derived for the pressure field in the fluid at distances far from the solid-fluid interface. The numerical procedure is described and results are presented for spherical cavities and inclusions embedded at various depths below the interface. The frequency spectra are compared with one term expansion of multiple scattering process, and with the single scattering approximation. Calculations for normal and oblique incidence are in general agreement with the experimental observations. These conclusions will be of use in the design of experiments for NDE of subsurface flaws

[en] This article briefly describes the T-matrix method and the MOOT (method of optimal truncation) of elastic wave scattering as they apply to A-D, SH- wave problems as well as 3-D elastic wave problems. Two methods are compared for scattering by elliptical cylinders as well as oblate spheroids of various eccentricity as a function of frequency. Convergence, and symmetry of the scattering cross section are also compared for ellipses and spheroidal cavities of different aspect ratios. Both the T-matrix approach and the MOOT were programmed on an AMDHL 470 computer using double precision arithmetic. Although the T-matrix method and MOOT are not always in agreement, it is in no way implied that any of the published results using MOOT are in error

[en] The scattering of waves by a flaw (cavity or inclusion) that is embedded in an elastic half space at a finite depth below the interface with a fluid half space is studied using the T-matrix approach. Expressions are derived for the scattered fields generated in the fluid and solid half spaces as well as the asymptotic form of the field in the fluid at a large distance from the interface. Numerical results are presented for spherical voids and steel inclusions embedded in epoxy as well as oblate spheroidal voids in a metal for various flaw depths, scattering geometries, and frequency of the incident wave. The results obtained by keeping different orders of multiple scattering between the flaw and the interface are critically discussed

[en] Based on the finite element-eigenmode expansion analysis, a PZT/polymer composite probe can be evaluated for different design parameters. The fluid loading effect, the internal damping, the driving impedance and the microstructure variation of the composite are all taken into account in the formulation. In addition, experimental studies were conducted for verificational purposes. Based on the analysis, it is concluded that the method is capable of evaluating and designing an array probe. The numerical results provide that the width to thickness ratio which equals 1/4.5 to 1/5 is an optimum value for 25% volume fraction of PZT with Spurrs epoxy as a filling material

[en] Multiwalled carbon nanotube (CNT) arrays were grown by catalytic thermal decomposition of acetylene, over Fe-catalyst deposited on Si-wafer in the temperature range 700-750 deg. C. The growth parameters were optimized to obtain dense arrays of multiwalled CNTs of uniform diameter. The vertical cross-section of the grown nanotube arrays reveals a quasi-vertical alignment of the nanotubes. The effect of varying the thickness of the catalyst layer and the effect of increasing the growth duration on the morphology and distribution of the grown nanotubes were studied. A scotch-tape test to check the strength of adhesion of the grown CNTs to the Si-substrate surface reveals a strong adhesion between the grown nanotubes and the substrate surface. Transmission electron microscopy analysis of the grown CNTs shows that the grown CNTs are multiwalled nanotubes with a bamboo structure, and follow the base-growth mechanism.

[en] Continuum mechanics models for the torsional buckling of carbon nanotubes (CNTs) are developed in the Letter. The applicability of these models is investigated for CNTs with different aspect ratios. In particular, molecular dynamics simulations are conducted to verify the feasibility of the models for moderately long CNTs

[en] Nonlocal elastic beam and shell models are developed and applied to investigate the small scale effect on buckling analysis of carbon nanotubes (CNTs) under compression. General and explicit solutions are derived and expressed in terms of the solutions via local or classical elastic models, in which the scale effect is not accounted, to reveal the small scale effect on CNTs buckling results. The dependence of the scale effect with respect to the length, radius, and buckling modes of CNTs is clearly established and observed from the universal solutions derived in the manuscript. It is clearly seen from the results that the buckling solutions for CNTs via local continuum mechanics are overestimated and hence the scale effect is indispensable in providing more accurate results for mechanical behaviors of CNTs via continuum mechanics