X-ray diffraction, optical microscopy, and microhardness studies of gas nitrided titanium alloys and titanium aluminide

Thermochemical surface gas nitriding of ß21s, Timetal 205 and a Ti–Al alloy was conducted using differential scanning calorimeter equipment, in nominally pure nitrogen at 850 °C and 950 °C (ß21s), 730 °C and 830 °C (Timetal 205), and 950 °C and 1050 °C (Ti–Al) for 1 h, 3 h and 5 h. X-ray diffraction analyses showed new phases formed in the nitrided layer, depending on the alloy and the time and the temperature of nitriding. Microstructures were analyzed using optical microscopy. Cross-sectional microhardness profiles of cross-sectional samples after nitriding were obtained using a Knoop indenter.

Image segmentation based on multi-scan constraint satisfaction neural network

A novel image segmentation method based on a constraint satisfaction neural network (CSNN) is presented. The new method uses CSNN-based relaxation but with a modified scanning scheme of the image. The pixels are visited with more distant intervals and wider neighborhoods in the first level of the algorithm. The intervals between pixels and their neighborhoods are reduced in the following stages of the algorithm. This method contributes to the formation of more regular segments rapidly and consistently. A cluster validity index to determine the number of segments is also added to complete the proposed method into a fully automatic unsupervised segmentation scheme. The results are compared quantitatively by means of a novel segmentation evaluation criterion. The results are promising.

Solving the problem of diffraction of an optical-band electromagnetic wave by metal nanostructured aperture arrays with the use of the method of impedance boundary conditions

The problem of diffraction of an optical wave by a 2D periodic metal aperture array with square, circular, and ring apertures is solved with allowance for the finite permittivity of a metal in the optical band. The correctness of the obtained results is verified through comparison with experimental data. It is shown that the transmission coefficient can be substantially greater than the corresponding value reached in the case of diffraction by a grating in a perfectly conducting screen.

Electromagnetic wave diffraction from an infinite array of complex-shaped microstrip reflectors

A numerical-analytical method is developed for solving surface integral equations (IEs) describing electromagnetic wave diffraction from arrays of complex-shaped planar reflectors. Solutions to these equations are regularized via analytical transformation of the separated singular part of the matrix kernel. Basis functions satisfying the metal-edge condition are determined on the entire surface of the complex region. The amplitude and phase responses of arrays consisting of polygonal reflectors are numerically investigated.