Preparation and characterisation of electrophoretically deposited hydroxyapatite coatings on type 316L stainless steel

Hydroxyapatite (HAP) coatings were developed on type 316L stainless steel (SS) by electrophoretic deposition at various deposition potentials from 30 to 90 V using the stoichiometric HAP (Ca/P ratio 1.67) powder in a suspension of isopropyl alcohol. The optimum coating parameters were established at 60 V and 3 min, after vacuum sintering at 800 °C. The phase purity of the coated surface was confirmed by XRD and secondary ion mass spectrometry confirmed the presence of both Ca and P on the coated layers. The electrochemical corrosion parameters E_corr (open circuit potential) and pitting potentials, evaluated in Hank’s solution shifted towards noble direction for the HAP coated specimens in comparison with uncoated type 316L SS. Electrochemical impedance spectroscopic investigations revealed higher polarisation resistance and lower capacitance values after immersing the coated specimens in Hanks solution for 200 h. This indicates the stable nature of the coatings formed.     

Evaluation of the coupled multielectrode array sensor as a real-time corrosion monitor

Coupled multielectrode array sensors made of carbon steel and stainless steels were evaluated and compared with electrochemical noise (EN) sensors. Good correlations between sensor signals and solution corrosivity were observed for all multielectrode array sensors. Some correlation between the average pit index and solution corrosivity was observed for the carbon steel EN sensors, but not for the stainless steel EN sensors. The time-average noise resistances from the stainless steel EN sensors correlate well with solution corrosivity. There were, however, large random fluctuations and drifting for all EN signals, which make the EN sensors unreliable as real-time monitors.     

Design considerations for highly efficient edge‐lit quantum dot displays

Quantum dots (QDs) are increasingly the technology of choice for wide color gamut displays. Two popular options to incorporate QDs into displays include on‐edge and on‐surface solutions. The opto‐mechanical design for an on‐edge QD solution including a LED light bar (“on‐edge QD light bar”) is more complex than the design for a standard white phosphor LED light bar. In this paper, we identify and investigate a range of design parameters for an on‐edge QD light bar, and we show that these parameters have significant influence on system efficiency and color uniformity. The effects of varying these parameters are explored through the use of a custom adjustable testbed and optical raytracing methods. Our testbed data demonstrate the inherent trade‐offs between efficiency and color uniformity and provide guidance for the design of high‐performing displays. The optical raytracing data demonstrate a good predictive capability and support the use of optical modeling methods for a detailed exploration of a wider range of design parameters.     

Fast Parallel Reordering and Isomorphism Testing of k -Trees

Abstract. In this paper two problems on the class of k -trees, a subclass of the class of chordal graphs, are considered: the fast reordering problem and the isomorphism problem. An O(log ² n) time parallel algorithm for the fast reordering problem is described that uses O(nk(n-k)/\kern -1ptlog n) processors on a CRCW PRAM proving membership in the class NC for fixed k . An O(nk(k+1)!) time sequential algorithm for the isomorphism problem is obtained representing an improvement over the O(n ² k(k+1)!) algorithm of Sekharan (the second author) [10]. A parallel version of this sequential algorithm is presented that runs in O(log ² n) time using O((nk((k+1)!+n-k))/log n) processors improving on a parallel algorithm of Sekharan for the isomorphism problem [10]. Both the sequential and parallel algorithms use a concept introduced in this paper called the kernel of a k -tree.     

A nano-plasmonic HMIM waveguide based concurrent dual-band BPF using circular ring resonator

This article analyzes the transmission line characteristics of plasmonic hybrid metal insulator metal (HMIM) waveguide, circular ring resonator (CRR) based dual-band band-pass filters with two transmission poles in both pass-bands in the optical regime using coupled line feed. The transmission line characteristics of an HMIM waveguide, such as characteristic impedance (ZPV), effective refractive index (neff) and propagation length (Lspp), have been obtained by using full wave simulation. Using basic HMIM slot waveguide, a CRR with periodic loading of double- and triple-ring CRR is numerically analyzed. Two input ports have been used for excitation, which are located at the separation of 180° positions along the CRR, and are coupled with the ring by parallel coupled lines, producing the dual pass-bands with the synchronous excitation of two transmission poles. The proposed double-ring dual-band band-pass filter (DR-DB-BPF) offers 35 dB extinction ratio (ER), 299.69 nm free spectral range (FSR) and narrow band full width half maximum (FWHM) of 78.057—112.43 nm. The triple-ring DB-BPF (TR-DB-BPF) has 22.5 dB ER, FSR of 292.18 nm and FWHM of 42.751—59.58 nm. The proposed filters are very useful in the development of dual-band filters for electronic photonic integrated circuits (EPICs), as the optical signals are filtered at two wavelengths simultaneously.     

Effect of shot peening on the fatigue and fracture behaviour of two titanium alloys

The fatigue and fracture behaviour of two titanium alloys, the near-alpha IMI-685 and alpha-beta IMI-318, were studied in the machined and polished (MP) as well as the machined, polished and shot (glass-bead) peened (MPS) conditions. Glass-bead peening reduced the room-temperature as well as the high-temperature (450°C) fatigue life of alloy IMI-685 at high stress amplitudes, _a, approaching the proof stress, _ps, of the material (LCF region). When the applied stress amplitude (0–770 MPa, HCF region) was comparable to the peen-induced peak longitudinal residual stress, _LP, i.e. (_LP/a)=0.92, an improvement in the room-temperature fatigue life of IMI-685 was observed. When the (_LP/a) ratio was less than this value, decreases in the fatigue life were seen. The room-temperature fatigue behaviour of IMI-318 at high stress amplitudes was similar to that of IMI-685. The decrease in the fatigue life of this alloy, at a stress amplitude (770 MPa) where improvement was observed for IMI-685, could be attributed to the higher relaxation of peen-induced residual stresses in IMI-318 compared with IMI-685. Glass-bead peening improved the hightemperature (450°C) fatigue life of IMI-685 at a low stress amplitude (465 MPa; (_a/PS)=0.87). The crack-initiation sites in the MP and the MPS conditions were at the surface for both the alloys. However, fracture in the surface layers of the alloys appeared more brittle in the peened (MPS) rather than in the unpeened (MP) condition.     

Effects of cyclic stressing,heat treatment and shot-peening pressure on the residual stress distribution in two titanium alloys

Using the method of drilling holes, the residual stress distributions were determined in two titanium alloys, IMI-685 and IMI-318, in the machined, polished, shot-peened and cyclically stressed (MPSC) as well as the heat-treated and quenched (HTQ) conditions. In IMI-318, the effect of shot-peening pressure on the residual stress distribution was also studied. Tensile cyclic stressing relaxed the shot-peen induced residual stresses in the longitudinal direction and the extent of relaxation depended on the degree of cyclic softening present in the material. In both alloys, in the post- heat-treated and quenched condition, the residual stresses were tensile in nature. In IMI-318, a decrease in the shot-peening pressure led to residual stresses of lower magnitudes. The peak residual stress was present closer to the surface when the shot-peening pressure was increased.     

Architectural design and FPGA implementation of radix-4 CORDIC processor

A new scaled radix-4 CORDIC architecture that incorporates pipelining and parallelism is presented. The latency of the architecture is n/2 clock cycles and throughput rate is one valid result per n/2 clocks for n bit precision. A 16 bit radix-4 CORDIC architecture is implemented on the available FPGA platform. The corresponding latency of the architecture is eight clock cycles and throughput rate is one valid result per eight clock cycles. The entire scaled architecture operates at 56.96 MHz of clock rate with a power consumption of 380 mW. The speed can be enhanced with the upgraded version of FPGA device. A speed-area optimized processor is obtained through this architecture and is suitable for real time applications.     

Vehicle license plate tilt correction based on the straight line fitting method and minimizing variance of coordinates of projection points

Tilt correction is a very crucial and inevitable task in the automatic recognition of the vehicle license plate (VLP). In this paper, according to the least square fitting with perpendicular offsets (LSFPO), the VLP region is fitted to a straight line. After the line slope is obtained, rotation angle of the VLP is estimated. Then the whole image is rotated for tilt correction in horizontal direction by this angle. Tilt correction in vertical direction by minimizing the variance of coordinates of the projection points is proposed. Character segmentation is performed after horizontal correction and character points are projected along the vertical direction after shear transform. Despite the success of VLP detection approaches in the past decades, a few of them can effectively locate license plate (LP), even when vehicle bodies and LPs have similar color. A common drawback of color-based VLP detection is the failure to detect the boundaries or border of LPs. In this paper, we propose a modified recursive labeling algorithm for solving this problem and detecting candidate regions. According to different colored LP, these candidate regions may include LP regions. Geometrical properties of the LP such as area, bounding box and aspect-ratio are then used for classification. Various LP images were used with a variety of conditions to test the proposed method and results are presented to prove its effectiveness.     

Towards nonideal iris recognition based on level set method, genetic algorithms and adaptive asymmetrical SVMs

We present algorithms for iris segmentation, feature extraction and selection, and iris pattern matching. To segment the inner boundary from a nonideal iris image, we apply a level set based curve evolution approach using the edge stopping function, and to detect the outer boundary, we employ the curve evolution approach using the regularized Mumford-Shah segmentation model with an energy minimization algorithm. Daubechies wavelet transform (DBWT) is used to extract the textural features, and genetic algorithms (GAs) are deployed to select the subset of informative features by combining the valuable outcomes from the multiple feature selection criteria without compromising the recognition accuracy. To speed up the matching process and to control the misclassification error, we apply a combined approach called the adaptive asymmetrical support vector machines (AASVMs). The parameter values of SVMs are also optimized in order to improve the overall generalization performance. The verification and identification performance of the proposed scheme is validated using the UBIRIS Version 2, the ICE 2005, and the WVU datasets.