Shrinkage testimation of the shape parameter of an inverse Gaussian distribution using a (α + β)min test

In this paper, we propose a shrinkage testimator for the shape parameter λ of an Inverse Gaussian distribution when the estimated value of λ is available in such a way that either λ = λ₁ or λ = λ₂(>;λ₁) is expected. The (α + β)_min test for testing the hypothesis H₀: λ = λ₁ against H₁: λ = λ₂ is derived. The shrinkage factors are chosen to be the function of the (α + β)_min test. The shrinkage testimator is found to be more efficient (in the sense of the MSE) than the UMVUE in certain parametric space.     

Distribution of the carbide phase in the viscoplastic layer during the rotational friction-welding of various steels

The paper presents the viscoplastic phenomena observed during the rotational friction-welding process of high-speed steel M2 (AISI SAE) with carbon steel 1060 (AISI SAE). The structure, phase composition and distribution of the carbide phase in the friction plane and adjoining zones are examined by using optical microscopy (OM) with a system for quantitative analysis, and scanning electron microscopy (SEM) in addition to EDS analysis. The experimentally-checked mathematical relationship is suggested for the calculation of the radial movements of the carbide phase, immediately next to the friction plane. On the basis of qualitative and quantitative evaluation of the microstructural and rheological appearances, a model of carbide phase distribution is also established in the viscoplastic and viscous layers in the area of the friction plane.     

Development of pitch-based carbon–copper composites

Carbon–copper composites with varying copper to carbon ratio of 0.66–1.5 (by weight) were developed from coal-tar-pitch-derived green coke (as such or modified with natural graphite) as carbon source and electrolytic grade copper powder at different heat treatment temperatures (HTTs) of 1000–1400 °C. The physical, mechanical, and electrical properties differ depending upon the HTT and also on copper to carbon ratio (Cu/C). The composites prepared at HTT of 1100 °C having Cu/C ratio of 0.66 and 0.9 exhibited a high bending strength of 150 and 140 MPa, bulk density of 2.63 and 2.81 gm/cm³, electrical resistivity of 1.6 and 0.96 m Ω cm and shore hardness of 88 and 84, respectively, in spite of well-known inadequate wettability between copper and carbon. Increasing the temperature from 1100 °C for processing of the composites deteriorated the properties mainly due to the loss of copper through melting above 1100 °C as revealed by X-ray, scanning electron microscopy, thermal analysis and EDAX studies.     

Oxidation of polycyclic aromatic hydrocarbons with hydrogen peroxide catalyzed by Iron(III)porphyrins

A variety of iron-metallated functional porphyrins have been synthesized and their catalytic activity to oxidize polycyclic aromatic hydrocarbons, (PAHs) using hydrogen peroxide as oxidant was investigated. It was found that iron-metallated porphyrins bearing strong electronegative groups at β-pyrrolic positions show an exceptionally high catalytic efficiency.     

Image-guided endoscopic surgery: results of accuracy and performance in a multicenter clinical study using an electromagnetic tracking system

Image-guided surgery has recently been described in the literature as a useful technology for improved functional endoscopic sinus surgery localization. Image-guided surgery yields accurate knowledge of the surgical field boundaries, allowing safer and more thorough sinus surgery. We have previously reviewed our initial experience with The InstaTrak System. This article presents a multicenter clinical study (n=55) that assesses the system's capability for localizing structures in critical surgical sites. The purpose of this paper is to present quantitative data on accuracy and performance. We describe several new advances including an automated registration technique that eliminates the redundant computed tomography scan, compensation for head movement, and the ability to use interchangeable instruments.     

Lateral protrusions of ohmic contacts to AlGaAs/GaAs MODFET material

Cross-sectional transmission electron microscopy is used to determine the structure of Au-, Ge- and Ni-based ohmic contacts at the interface with AlGaAs/GaAs modulation-doped field-effect-transistor material. Significant lateral diffusion (?0.12?m) is found to occur at the edge of the contact during alloying. The observed contact structure places a limit on minimum geometries and must be taken into account if accurate device modelling is to be carried out.     

Microstructural Analysis and Transport Properties of Thermally Sprayed Multiple-Layer Ceramic Coatings

Multilayer, graded ceramic/metal coatings were prepared by an air plasma spray method on Ti-6Al-4V, 4140 steel and graphite substrates. The coatings were designed to provide thermal barriers for diesel engine pistons to operate at higher temperatures with improved thermal efficiency and cleaner emissions. A systematic, progressive variation in the mixture of yttria-stabilized zirconia and bondcoat alloys (NiCoCrAlYHfSi) was designed to provide better thermal expansion match with the substrate and to improve thermal shock resistance and cycle life. Heat transfer through the layers was evaluated by a flash diffusivity technique based on a model of one-dimensional heat flow. The aging effect of the as-sprayed coatings was captured during diffusivity measurements, which included one heating and cooling cycle. The hysteresis of thermal diffusivity due to aging was not observed after 100-h annealing at 800 °C. The measurements of coatings on substrate and freestanding coatings allowed the influence of interface resistance to be evaluated. The microstructure of the multilayer coating was examined using scanning electron microscope and electron probe microanalysis.     

A slow wave structure and its application in bandpass filter design

This paper presents a new slow wave open-loop resonator filters with reduced size and improved stopband characteristics. A comprehensive treatment of different kind of coupling in this structure is demonstrated. Two and four resonator band pass filters at center frequency 2.15 and 2.30 GHz with different bandwidth are designed. The simulated results are verified with the help of two different software packages (IE3D and Sonnet Lite).     

Studies on the effect of epoxide equivalent weight of epoxy resins on thermal,mechanical, and chemical characteristics of vinyl ester resins

Three samples of vinyl ester resins (VERs) were synthesized using bisphenol‐A‐based epoxy resins of varying epoxide equivalent weights (EEW) and acrylic acid in presence of triphenylphosphine as a catalyst at 80 ± 2°C. The cresyl glycidyl ether was used as reactive diluent during the synthesis of VERs. A suitable reaction mechanism was proposed and discussed for the reactions involving epoxide group and acid groups. This was further confirmed by infrared spectroscopic analysis. The maximum peak temperature from DSC were at 106.05°C, 114.20°C, and 128.86°C for benzoyl peroxide initiated VERs viz. samples V₁C_V, V₂C_V, and V₃C_V, respectively, increased with the increase of EEW of the parent epoxy resin. It has also been found that the films of VER having highest EEW of bisphenol‐A epoxy resin showed best chemical resistance amongst all other VERs in this study. The mechanical properties such as hardness and flexibility also showed a similar trend. The thermal stability was found to decrease with the increase of EEW of bisphenol‐A epoxy resin in the VERs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010