A Compact and Wideband Coupled-Line Coupler with High Coupling Level Using Shunt Periodic Stubs

A wideband microstrip forward-wave coupled-line coupler with high coupling value is presented. Compared with the conventional edge-coupled microstrip forward-wave coupler, this symmetrical structure, consisting periodic shunt stubs between the two coupled-lines, achieves wider operating bandwidth and larger coupling level. To characterize this structure, the equivalent circuit model is established and verified by measurement and full-wave results. The designed and fabricated prototype is a 0-dB forward-wave coupler with 0.6 mm stub length. This coupler exhibits a coupled amplitude balance of ±2 dB, good matching (15dB) and at least 15dB isolation between adjacent ports over a wide bandwidth of 66% from 2 GHz to 4 GHz centered at 3 GHz. The coupled-line length and width of the proposed structure are approximately λg/2 and λg/13, respectively, which makes it more compact than the conventional forward coupled-line couplers

Wear maps for TiC composite based coatings deposited on 303 stainless steel

Dry sliding wear (pin-on-disc) tests were carried out under ambient conditions at room temperature for TiC coated and uncoated 303 stainless steel, using alumina as a counterface. The composite coating which was developed by Tungsten Inert Gas (TIG) methods increased the surface hardness of the substrate and the sliding wear resistance of the substrate. Wear maps for both uncoated and coated materials were developed on the basis of tests results. The results indicated that the role of oxidative wear differed significantly for both coated and uncoated materials on the wear map. In addition, it was found that TiC composite coatings not only increased the wear resistance but also expanded the mild wear region towards higher loads and sliding speeds

On Bivariate Exponentiated Extended Weibull Family of Distributions

In this paper, we introduce a new class of bivariate distributions called the bivariate exponentiated extended Weibull distributions. The model introduced here is of Marshall-Olkin type. This new class of bivariate distributions contains several bivariate lifetime models. Some mathematical properties of the new class of distributions are studied. We provide the joint and conditional density functions, the joint cumulative distribution function and the joint survival function. Special bivariate distributions are investigated in some detail. The maximum likelihood estimators are obtained using the EM algorithm. We illustrate the usefulness of the new class by means of application to two real data sets.Comment: arXiv admin note: text overlap with arXiv:1501.03528 by other author