A novel implementation of multilevel fast multipole algorithm for higher order Galerkin's method

A new approach is proposed to reduce the memory requirements of the multilevel fast multipole algorithm (MLFMA) when applied to the higher order Galerkin's method. This approach represents higher order basis functions by a set of point sources such that a matrix-vector multiply is equivalent to calculating the fields at a number of points from given current sources at these points. The MLFMA is then applied to calculate the point-to-point interactions. This permits the use of more levels in MLFMA than applying MLFMA to basis-to-basis interactions directly and, thus, reduces the memory requirements significantly.     

Studies on the determination of surface deuterium in AISI 1062, 4037, and 4140 steels by secondary ion mass spectrometry

The concentration of deuterium at the surface of cathodically charged high strength steels AISI 1062, 4037, and 4140 has been determined by secondary ion mass spectrometry (SIMS). The beneficial effects of pickling in NAP (a mixture of nitric, acetic, and phosphoric acids) to remove surfacebound deuterium have been observed. formerly with AMCA International Limited, Kanata, ON, Canada     

Adaptive position/force control of robot manipulators withoutvelocity measurements: theory and experimentation

In this paper, we design an adaptive position/force controller for robot manipulators during constrained motion. The proposed controller can compensate for parametric uncertainty while only requiring measurements of link position and end-effector force. A filtering technique is utilized to produce a pseudo-velocity error signal and thus, eliminate the need for link velocity measurements. The control strategy provides semiglobal asymptotic tracking performance for the end-effector position and the interaction force between the constraint and the end-effector. An experimental implementation of the proposed controller on a two-link planar robot is also presented.     

Preparation and characterization of partially substituted LiMyMn2−yO4 (M=Ni, Co, Fe) spinel cathodes for Li-ion batteries

The electrochemical and thermal behaviors of the spinels-LiMn₂O₄, LiCo_1/6Mn_11/6O₄, LiFe_1/6Mn_11/6O₄, and LiNi_1/6Mn_11/6O₄ were studied using electrochemical and thermochemical techniques. The electrochemical techniques included cyclic voltammetry, charge-discharge cycling of 2016 coin cells and diffusion coefficient measurements using Galvanostatic Intermittent Titration Technique. Better capacity retention was observed for the substituted spinels (0.11% loss per cycle for LiCo_1/6Mn_11/6O₄; 0.3% loss per cycle for LiFe_1/6Mn_11/6O₄; and 0.2% loss per cycle for LiNi_1/6Mn_11/6O₄) than for the lithium manganese dioxide spinel (1.6% loss per cycle for first ten cycles, 0.9% loss per cycle for 33 cycles) during 33 cycles. The Differential Scanning Calorimetry results showed that the cobalt substituted spinel has better thermal stability than the lithium manganese oxide and other substituted spinels.     

A novel grid-robust higher order vector basis function for themethod of moments

A set of novel, grid-robust, higher order vector basis functions is proposed for the method-of-moments (MoM) solution of integral equations for three-dimensional (3-D) electromagnetic (EM) problems. These basis functions are defined over curvilinear triangular patches and represent the unknown electric current density within each patch using the Lagrange interpolation polynomials. The highlight of these basis functions is that the Lagrange interpolation points are chosen to be the same as the nodes of the well-developed Gaussian quadratures. As a result, the evaluation of the integrals in the MoM is greatly simplified. Additionally, the surface of an object to be analyzed can be easily meshed because the new basis functions do not require the side of a triangular patch to be entirely shared by another triangular patch, which is a very stringent requirement for traditional vector basis functions. The proposed basis functions are implemented with point matching for the MoM solution of the electric-field integral equation, the magnetic-field integral equation, and the combined-field integral equation. Numerical examples are presented to demonstrate the higher order convergence and the grid robustness for defective meshes using the new basis functions     

A spectral Lanczos decomposition method for solving 3-Dlow-frequency electromagnetic diffusion by the finite-elementmethod

A very efficient three-dimensional (3-D) solver for the diffusion of the electromagnetic fields in an inhomogeneous medium is described. The proposed method employs either the node-based or the edge-based finite-element method (FEM) to discretize Maxwell's equations. The resultant matrix equation is solved by the spectral Lanczos decomposition method (SLDM), which is based on the Krylov subspace (Lanczos) approximation of the solution in the frequency domain. By analyzing some practical geophysical problems, it is shown that the SLDM is extremely fast and, furthermore, the electromagnetic fields at many frequencies can be evaluated by performing the SLDM iteration only at the lowest frequency     

Metal location and thickness in a multilayered sheet by measuring Kα/Kβ, Lα/Lβ and Lα/Lγ X-ray ratios

When a multilayered material is analyzed by means of energy-dispersive X-ray fluorescence analysis, then the X-ray ratios of Kα/Kβ, or Lα/Lβ and Lα/Lγ, for an element in the multilayered material, depend on the composition and thickness of the layer in which the element is situated, and on the composition and thickness of the superimposed layer (or layers).Multilayered samples are common in archaeometry, for example, in the case of pigment layers in paintings, or in the case of gilded or silvered alloys. The latter situation is examined in detail in the present paper, with a specific reference to pre-Columbian alloys from various museums in the north of Peru.     

Synchrotron-induced X-ray fluorescence from rat bone and lumber vertebra of different age groups

The fluorescence spectra from rat bones of different age groups (8, 56 and 78 weeks) and lumber vertebra were measured with 8, 10 and 12 keV synchrotron X-rays. We have utilized the new hard X-ray micro-spectroscopy beamline facility, X27A, available at NSLS with a primary beam spot size of the order of ∼10 μm. With this spatial resolution and high flux throughput, X-ray fluorescent intensities for Ca and other trace elements were measured using a liquid-nitrogen-cooled 13-element energy-dispersive high-purity germanium detector. Regarding the lumber vertebra, we acquired the fluorescence spectra from the left, right and middle portions and calcium accumulation was evaluated and compared with the other samples. We have identified the major trace elements of Ca, Ni, Fe and Zn and minor trace elements of Ti, Cr and Mn in the sample. The percentage of scattered radiation and trace element contributions from these samples were highlighted at different energies.     

Cork Embedded Internal Features and Contrast Mechanisms with Dei Using 18, 20, 30, 36, and 40 keV Synchrotron X-Rays

Images of the cork used for wine and other bottles are visualized with the use of diffraction-enhanced imaging (DEI) technique. Present experimental studies allowed us to identify the cracks, holes, porosity, and importance of soft-matter (soft-material) and associated biology by visualization of the embedded internal complex features of the biological material such as cork and its microstructure. Highlighted the contrast mechanisms above and below the K-absorption edge of iodine and studied the attenuation through a combination of weakly and strongly attenuating materials.     

Efficient time-domain and frequency-domain finite-element solutionof Maxwell's equations using spectral Lanczos decomposition method

An efficient three-dimensional solver for the solution of the electromagnetic fields in both time and frequency domains is described. The proposed method employs the edge-based finite-element method (FEM) to discretize Maxwell's equations. The resultant matrix equation after applying the mass-lumping procedure is solved by the spectral Lanczos decomposition method (SLDM), which is based on the Krylov subspace (Lanczos) approximation of the solution. This technique is, therefore, an implicit unconditionally stable finite-element time and frequency-domain scheme, which requires the implementation of the Lanczos process only at the largest time or frequency of interest. Consequently, a multiple time- and frequency-domain analysis of the electromagnetic fields is achieved in a negligible amount of extra computing time. The efficiency and effectiveness of this new technique are illustrated by using numerical examples of three-dimensional cavity resonators