A Simple Proof of the Alternation Theorem

A simple proof of the alternation theorem for minimax FIR filter design is presented in this paper. It requires no background on mathematical optimization theory, and is based on easily understood properties of filters with equiripple behavior. The method is similar to the classical counting argument used in early mathematics literature. The contribution here is a simplified presentation which directly uses filter design language

Composite Filler Characterization by Scanning Electron Microscopy, Image Analysis and Thermogravimetry

The morphological and compositional characterization of the filler particles in selected dental composites has been accomplished by a combination of backscattered electron imaging, digital imaging , energy dispersive X-ray analysis and thermogravimetry. Backscattered electron images provide excellent composition contrast between the filler and the matrix in this analysis . Qualitative energy dispersive spectroscopy was used to classify the filler composition in the composites studied. The digital imaging technique of feature analysis was utilized to quantitatively characterize the particle morphological parameters and their distributions. Several parameters were determined of which the particle area, breadth, height and Waddel diameter are emphasized. Particle size distribution histograms were also obtained. The filler contents in commercial composites were also determined by thermogravimetry. Thus a comprehensive method has been developed and applied to characterize filler morphology in particulate dental composites, which include both commercial and experimental systems. The commercial systems show variations in filler composition, filler size and distribution as well as filler loading levels. The experimental systems confirm variations in particle size and size distributions as a function of filler processing time

Properties of a New Dental Porcelain

A high strength dental porcelain OPTEC, HSP™ has recently been introduced for use in the fabrication of crowns, three-unit anterior bridges with a single pontic, inlays, on lays, veneers, etc., without a metal substrate. This investigation reports the results of our research involving the characterization of the structure properties and thermally induced transformations of this porcelain. It has been found that the material possesses superior strength and other properties relative to conventional porcelains. The improved properties appear to result from the presence of a very fine and relatively dense distribution of leucite crystals. Scanning electron microscopy indicates, however, that the new product needs additional optimization to improve uniformity of crystallite distribution. Scanning electron microscopy and X-ray diffraction studies also reveal well defined structural and crystallographic transformations during thermal treatment at selected temperature ranges. The primary transformation appears to be crystallization of metastable sanidine from the glass matrix. The crystallization of sanidine leads to a translucent to opaque transition. The transformations appear to follow the phase transitions expected from the phase diagrams

Eigenfilters for the design of special transfer functions with applications in multirate signal processing

Based on the multistage approach, a design procedure is presented for finding a spectral factor of an mth-band filter and for designing multistage decimation filters. The proposed design method finds spectral factors of mth-band FIR (finite-impulse response) filters without direct computation, and yields filters with much higher attenuation than would be possible by conventional methods. Such mth-band filters are used in filter-bank designs, including perfect-reconstruction systems

Improved approach for design of perfect reconstruction FIR QMF banks, with lossless lattice structures

A property of FIR (finite-impulse response) lossless systems is introduced, leading to substantial improvement in the sign procedure for perfect-reconstruction QMF (quadrature mirror filter) banks. The property enables the designer to initialize the coefficients of a lattice structure (which characterizes the analysis bank), in such a way as to speed up to the convergence. A design example is provided. Compared to other methods, the proposed method is shown to converge faster, and always leads to much improved attenuation characteristics for a given filter length

Magnetic Barkhausen emission analysis for assessment of microstructures and damage

Application of magnetic Barkhausen emission (MBE) analysis for assessment of microstructures and damage in various materials including carbon steel, Cr-Mo ferritic steels, 17-4 PH steel and metastable austenitic stainless steel. Thermally-induced microstructural changes in Cr-Mo steels have been correlated with MBE, based on a two-stage magnetisation process model. The MBE parameters have also been used to characterise different stages of tensile deformation and to assess tensile strength. Charpy impact energy, quality of induction hardening process, progress of carburisation in reformer tubes and fatigue damage

Theory and design of perfect reconstruction transmultiplexers and their relation to perfect reconstruction QMF banks

The theory of transmultiplexers involves the design of filters for interconversion between Time Domain Multiplexing (TDM) and Frequency Division Multiplexing (FDM), such that the undesirable Crosstalk is minimized. In TDM → FDM → TDM conversion, the perfect reconstruction trans-multiplexer (PR-TMUX) achieves complete Crosstalk Cancellation (CC) and is distortion-free. In this paper, we present an analysis of the PR-TMUX based on the polyphase component matrices of the filter banks used in TDM → FDM and FDM → TDM conversion respectively. Using that, a necessary and sufficient condition for complete CC is obtained. The close relation between PR-TMUX filters and PR-QMF banks is used to obtain a direct design procedure for PR-TMUX filters

Evaluation of Erbium:YAG Laser Radiation of Hard Dental Tissues: Analysis of Temperature Changes, Depth of Cuts and Structural Effects

Temperature elevations, depths of cuts and structural changes produced by 2.94 micron pulsed Erbium:YAG laser radiation of hard dental tissues, at different power levels and exposure times of the laser, were studied. The depth of cut produced was found to vary significantly as a function of power level and exposure time on dry teeth. The mean temperature rise with laser radiation was also influenced both by power level and time of exposure. The effect of water flow on the teeth during laser exposure was evaluated; the results indicate that the ablation efficiency was better, temperature elevations lower and structural changes minimal to absent in the presence of water as compared to teeth that were dry during laser radiation