The effects of nitrogen bonding on hardness of AIN/CrN multilayer hard coatings

AIN/CrN multilayer hard coatings with various bilayer thicknesses were fabricated by a reactive sputtering process. The microstructural and mechanical characterizations of multilayer coatings were investigated through transmission electron microscope (TEM) observations and the hardness measurements by nano indentation. In particular, the variation of chemical bonding states of the bilayer nitrides was elucidated by near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Many broken nitrogen bonds were formed by decreasing the bilayer thickness of AIN/CrN multilayer coatings. Existence of optimum AIN/CrN multilayer coatings thickness for maximum hardness could be explained by the competition of softening by the formation of broken nitrogen bonds and strengthening induced by decreasing bilayer thickness.     

Volume rendering in the presence of partial volume effects

In tomographic imagery, partial volume effects (PVEs) cause several artifacts in volume renditions. In X-ray computed tomography (CT), for example, soft-tissue-like pseudo structures appear in bone-to-air and bone-to-fat interfaces. Further, skin, which is identical to soft tissue in terms of CT number, obscures the rendition of the latter. The purpose of this paper is to demonstrate these phenomena and to provide effective solutions that yield significantly improved renditions. We introduce two methods that detect and classify voxels with PVE in X-ray CT. Further, a method is described to automatically peel skin so that PVE-resolved renditions of bone and soft tissue reveal considerably more detail. In the first method to address PVE, called the fraction measure (FM) method, the fraction of each tissue material in each voxel v is estimated by taking into account the intensities of the voxels neighboring v. The second method, called uncertainty principle (UP) method, is based on the following postulate (Saha and Udupa, 2001): In any acquired image, voxels with the highest uncertainty occur in the vicinity of object boundaries. The removal of skin is achieved by means of mathematical morphology. Volume renditions have been created before and after applying the methods for several patient CT datasets. A mathematical phantom experiment involving different levels of PVE has been conducted by adding different degrees of noise and blurring. A quantitative evaluation is done utilizing the mathematical phantom and clinical CT data wherein an operator carefully masked out voxels with PVE in the segmented images. All results have demonstrated the enhanced quality of display of bone and soft tissue after applying the proposed methods. The quantitative evaluations indicate that more than 98% of the voxels with PVE are removed by the two methods and the second method performs slightly better than the first. Further, skin peeling vividly reveals fine details in the soft tissue structures.     

A novel technique to evaluate the erosion resistance of silicone rubber composites for high voltage outdoor insulation using infrared laser erosion

The standard methods available to test tracking and erosion resistance of filled silicone rubber do not allow to delineate the fundamentals of the thermal degradation, although the heat from the dry band arcing is the main degradation factor. In this work a thermal imaging camera is used to investigate the performance of filled silicone rubber in an inclined plane test, and a scheme is established to relate the temperature and the electrical discharge energy. Further, an infrared laser technique, based on constant energy approach, is developed to study the material performance under laser heating. The technique consists of applying a certain amount of infrared laser energy during a set time period, in order to produce erosion in the silicone rubber samples. Through correlation studies the applicability of the proposed laser technique to rank silicone rubber samples with various fillers has been validated. The laser tests show identical ranking of samples when compared to samples ranked using inclined plane tests, yet offering significant advantages of being faster, simpler, and reproducible.     

Aging Characteristics of RTV Silicone Rubber Insulator Coatings

The paper reports on tests done on four commercial room temperature vulcanized (RTV) silicone rubber high voltage insulator coatings aimed at achieving information on the relative performance of the coatings with respect to aging. The initial characterization of the coatings includes the identification of the primary filler type, concentration of filler, the amount of free fluid, and the molecular species of the free fluid. Soxhlet extraction and gas chromatography tests show considerable depletion of fluid after accelerated aging tests in acid-water and the associated changes to the physical properties is assessed by standard mechanical tests on coupon size specimens. The effect of acid-water aging on the hydrophobicity is assessed by measurements of the static contact angle and the onset of leakage current in an incline plane test. Several field aged coatings are assessed for residual LMW fluid which is compared to accelerated aging tests.     

Evaluation of medium voltage enameled wire exposed to fast repetitive voltage pulses

The paper describes the investigation of the failure mechanisms of medium voltage inter-turn insulation, as a consequence of pulse aging. To study the performance and failure behaviour of enameled wires, models of inter-turn insulation are prepared with enameled wires having polyimide and nano-filled coatings. The aging of such bar samples is attained by sinusoidal (60Hz), fast repetitive unipolar voltage pulses, and high frequency AC waveforms. To establish the residual strength of the bar samples, DC breakdown voltages are determined before and after the aging. In addition, the thermally stimulated depolarization current (TSDC) is used to provide information about the relaxation processes, such as the disorientation of the dipoles and the release of charges from the trapping sites in enameled wires. The various trapping levels, which have discrete energy differences with distinct peaks in the thermograms, are discussed in terms of space charge polarization     

Effect of Rapid Solidification on Microstructural Evolution in MgO–MgAl2O4

The response of the MgO–20 and 30 mol% Al₂O₃ compositions to rapid solidification has been studied. The oxides were twin-roller quenched and the resulting flakes were characterized by X-ray diffraction and transmission electron microscopy. The results indicate that metastable extensions of spinel and periclase occurred and the microstructural pathway was determined from the final microstructure. The flakes having MgO–20 mol% Al₂O₃ show a dendritic structure consisting of periclase and spinel. In the MgO–30 mol% Al₂O₃ composition, the liquid transforms to spinel partitionlessly. The spinel is believed to undergo decomposition by a modulation in composition, and the resulting microstructure consists of spinel and periclase. Kinetic and thermodynamic aspects of phase selection have been rationalized based on the metastable extensions of the different phase fields in the phase diagram. It has been proposed that composition fluctuations in spinel are stabilized because of the formation of disordered phases with a continuous range of order parameter on the tetrahedral sublattice.     

On the Law of Importation $(x wedge y) longrightarrow z equiv (x longrightarrow (y longrightarrow z))$ in Fuzzy Logic

The law of importation, given by the equivalence (x Lambda y) rarr z equiv (xrarr (y rarr z)), is a tautology in classical logic. In A-implications defined by Turksen et aL, the above equivalence is taken as an axiom. In this paper, we investigate the general form of the law of importation J(T(x, y), z) = J(x, J(y, z)), where T is a t-norm and J is a fuzzy implication, for the three main classes of fuzzy implications, i.e., R-, S- and QL-implications and also for the recently proposed Yager's classes of fuzzy implications, i.e., f- and g-implications. We give necessary and sufficient conditions under which the law of importation holds for R-, S-, f- and g-implications. In the case of QL-implications, we investigate some specific families of QL-implications. Also, we investigate the general form of the law of importation in the more general setting of uninorms and t-operators for the above classes of fuzzy implications. Following this, we propose a novel modified scheme of compositional rule of inference (CRI) inferencing called the hierarchical CRI, which has some advantages over the classical CRI. Following this, we give some sufficient conditions on the operators employed under which the inference obtained from the classical CRI and the hierarchical CRI become identical, highlighting the significant role played by the law of importation.     

Al-SiC ELECTRONIC PACKAGES WITH CONTROLLED THERMAL EXPANSION COEFFICIENT BY A NEW METHOD OF PRESSURELESS INFILTRATION

A method is described whereby SiC preforms may be infiltrated in air by a molten aluminum alloy to yield a metal matrix composite with thermal expansion coefficients that are suitable for electronic packaging, such as in microwave integrated circuits. Crucible geometries and infiltration conditions may be designed to provide inexpensive and reusable containers and useful section thicknesses in ∼1 hr. Intricate geometries may be fabricated in the green state of the ceramic, prior to infiltration, thereby minimizing final machining of the composite.     

Medical image reconstruction,processing, visualization,and analysis: the MIPG perspective. Medical Image Processing Group

In this paper, we identify and describe the key ideas, concepts and software related to Medical Imaging that emerged from our research group, which is commonly known by the acronym MIPG, denoting Medical Image Processing Group. For the purpose of our presentation, we consider the entire discipline of Medical Imaging to consist of the areas of acquisition, postprocessing, evaluation, and application. We are indeed fortunate to be able to discuss seminal research from our group in each of these areas. In Section II, we identify relevant moments of inception and describe our past contributions. Our achievements, current activities, and future directions are summarized in Section III, Section IV, and Section V, respectively; the keys to our success are listed in Section V