Epoch Extraction by Phase Modelling of Speech Signals

Epochs are instants of significant excitation of vocal-tract system in speech production process. In this paper, we attempt to extract information about epochs from phase spectra of speech signals. The phase spectrum of speech is modelled as the response of an allpass (AP) filter, and the resulting error signal is used for epoch extraction. The parameters of AP model are estimated by imposing sparsity constraints on the error signal. The error signal, thus obtained, exhibits prominent peaks at epoch locations. The epochal candidates obtained from the error signal are refined using a dynamic programming algorithm. The performance of the proposed method is consistent across genders and is comparable with the state-of-the-art methods.     

Evaluation of the Binding Mechanism of Human Defensin 5 in a Bacterial Membrane: A Simulation Study

Human α-defensin 5 (HD5) is a host-defense peptide exhibiting broad-spectrum antimicrobial activity. The lipopolysaccharide (LPS) layer on the Gram-negative bacterial membrane acts as a barrier to HD5 insertion. Therefore, the pore formation and binding mechanism remain unclear. Here, the binding mechanisms at five positions along the bacterial membrane axis were investigated using Molecular Dynamics. (MD) simulations. We found that HD5 initially placed at positions 1 to 3 moved up to the surface, while HD5 positioned at 4 and 5 remained within the membrane interacting with the middle and inner leaflet of the membrane, respectively. The arginines were key components for tighter binding with 3-deoxy-d-manno-octulosonic acid (KDO), phosphates of the outer and inner leaflets. KDO appeared to retard the HD5 penetration.     

Influence of machining parameters and new nano-coated tool on drilling performance of CFRP/Aluminium sandwich

Drilling and fastening of hybrid materials in one-shot operation reduces cycle time of assembly of aerospace structures. One of the most common problems encountered in automatic drilling and riveting of multimaterial is that the continuous chips curl up on the body of the tool. Drilling of carbon fiber reinforced plastic (CFRP) is manageable, but when the minute drill hits the aluminium (Al) or titanium (Ti), the hot and continuous chips produced during machining considerably damage the CFRP hole. This study aims to solve this problem by employing nano-coated drills on multimaterial made of CFRP and aluminium alloy. The influence of cutting parameters on the quality of the holes, chip formation and tool wear were also analyzed. Two types of tungsten carbide drills were used for the present study, one with nano-coating and the other, without nano coating. The experimental results indicated that the shape and the size of the chips are strongly influenced by feed rate. The thrust force generated during drilling of the composite plate with coated drills was 10–15% lesser when compared to that generated during drilling with uncoated drills; similarly, the thrust force in the aluminium alloy was 50% lesser with coated drills when compared to thrust force generated without coated drills. Thus, the use of nano-coated drills significantly reduced the surface roughness and thrust force when compared with uncoated tools.     

Investigation on structural,optical, thermal,mechanical and dielectric properties of l-proline cadmium chloride monohydrate single crystals: An efficient NLO material

In the present work, we have grown single crystals of l-proline cadmium chloride monohydrate (LPCCM) by slow evaporation solution technique (SEST) at room temperature and recorded their live growth kinetics with the help of inverted microscope. Crystal size at various stages of growth and its corresponding morphology was also recorded. Powder X-ray diffraction (PXRD) analysis of LPCCM single crystals confirmed the orthorhombic structure. Respective values of crystallite size, strain and dislocation density have been calculated using PXRD data. Metal complex coordination of the single crystal is studied by FTIR spectroscopic. The optical properties of the grown crystals were investigated through UV–VIS spectroscopic studies and shows that the crystals have very low absorption in entire characterized wavelength range 200–800 nm. The optical band gap was calculated and found to be ∼5.6 eV. Optical constants of the material is determined by theoretical calculations. The chemical etching study was also carried out to study the density of defects in the grown crystals. The photoluminous excitation and emission spectra and thermal property by TGA/DTA curve were recorded. Further, the mechanical properties have been studied using Vicker's microhardness tester as well as many parameters such as fracture toughness (K_c), Brittleness index (B_i) and yield strength (σ_ν) are presented. Dielectric studies have been carried out with varying frequency and temperatures.     

Complex impedance studies of low temperature synthesized fine grain PZT/CeO2 nanocomposites

Fine grain nanocomposites of (100 ? x) PbZr_0.52Ti_0.48O₃ ? (x) CeO₂ with x = 0.5, 1 and 2 wt%, were prepared and characterized for structural and microstructural changes. Addition of ceria nanoparticles resulted into a fine grain microstructure with average grain size ranging from 600 nm to 440 nm and a significant decrease in sintering temperature (～200 °C). Size distribution profile, as analyzed by lognormal distribution function suggests a very narrow size distribution. X-ray diffraction analyses of sintered samples reveal that fine grain PZT/CeO₂ nanocomposite could retain distorted tetragonal structure even with grain size as low as 440 nm. Further, complex impedance spectroscopy studies were performed to illustrate the electrical properties of bulk and grain boundary phases in fine grain ceramics. Two electrical processes in the impedance spectra at temperatures above 350 °C were attributed to bulk and grain boundary phase. Magnitude of grain boundary capacitance and corresponding transition was found to be strongly dependent on grain size of the system. Both bulk and grain boundary relaxation processes follows Arrhenius law.     

Hydrolysis of SnCl2 on polyaniline: Formation of conducting PAni‐SnO2 composite with enhanced electrochemical properties

First time in the literature, we report that polyaniline‐EB can be doped by SnCl₂ to give conducting SnO₂ doped polyaniline novel material. The composite is characterized by Fourier transform infrared, ultraviolet‐visible, X‐ray diffraction, scanning electron micrograph, transmission electron microscopy, and electrochemical methods. The new composite exhibited improved electrochemical properties compared with the virgin polymer. The composite is also expected for its high sensitivity for recognizing volatile organic compounds. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Two phase natural convection: CFD simulations and PIV measurement

Buoyancy induced flow and heat transfer are important phenomena in a wide range of engineering systems e.g. electronics and photovoltaics cooling, thermosiphon heat exchangers, solar-thermal heat absorbers, passive decay heat removal systems, etc. Such systems are subject to thermal stratification. The objective of the present work is to study the single phase and two phase (boiling) natural convection accompanied by thermal stratification. We carried out velocity and temperature measurements in a rectangular tank (0.8×0.6×0.6 m³) fitted with (a) a central tube, and (b) a 10 tube assembly; which form the heat transfer surface. Flows were measured using Particle Image Velocimetry (PIV). Additionally, computational fluid dynamic (CFD) simulations of these systems were performed: first with an assumption of no-boiling (i.e. no phase change) near the heat transfer surfaces; for which we used the open source CFD code OpenFOAM-1.6. For two phase simulations, we used the boiling model of Ganguli et al. (2010) and carried out simulations using the commercial software FLUENT 6.3. The extent of stratification and mixing has been investigated for a range of Rayleigh numbers from 4.34×10¹¹ to 2.59×10¹⁴. The flow information obtained from PIV was analyzed for insights into the dynamics of turbulent flow structures. We used the signal processing technique of discrete wavelet transform (DWT) for this purpose. From the analysis, we were able to estimate the size, velocity and energy distribution of turbulent structures in our flows. This information was used to estimate wall heat transfer coefficients. A good agreement was observed between the predicted and the experimental values of heat transfer coefficients.     

Optimization of plasma treatment variables to improve the hydrophilicity of polylinen® fabrics

Polylinen^® fabrics are obtained as a result of modification in the physical structure of polyester yarns to replicate the linen fabric. The scanning electron microscope analysis and Fourier transform infrared results reveal that the plasma treated fabric surface is effectively modified to enhance the wettability of the fabrics. In the present study, response surface methodology was employed to investigate the effects of different plasma treatment variables on the wetting behavior of polylinen fabrics. Box–Behnken design was used for the optimization of plasma treatment process and to evaluate the effects and interactions of the process variables, i.e. treatment time, power, and distance between the electrodes on the wettability of polylinen fabrics. The optimum conditions for maximum wicking height (4.3?cm) and spreading rate (86?s) of polylinen fabrics were established at 75?s treatment time, 460 watt power, and 2.5?cm distance between the electrodes. The plasma treated polylinen fabrics showed much better wettability in terms of wicking and spreading rate compared to untreated fabrics, which confirms that the modified structure of polylinen fabric and the plasma treatment influences the wettability of fabrics.     

Dispersion and Setting of Powder Suspensions in Concentrated Aqueous Urea Solutions for the Preparation of Porous Alumina Ceramics with Aligned Pores

Highly concentrated alumina powder suspensions have been prepared in aqueous urea solutions of concentrations in the range 200–360 g/100 mL using an ammonium poly(acrylate) dispersant at 80°C. The dispersant concentration for the suspension viscosity minimum in the urea solutions is higher than that in water due to the higher processing temperature. The urea solutions having higher dielectric constant than that of water offer higher interparticle potential that resulted in better dispersion of the powder as evidenced from the lower viscosity and yield stress of the suspensions. The decrease in temperature increased the suspension viscosity and the suspension formed a strong gel when cooled to room temperature due to the crystallization of urea. The minimum urea solution concentration for a 55 vol% alumina suspension to form a dimensionally stable gel is 240 g/100 mL. The compressive strength and Young's modulus of the gels increased with the increase in urea solution concentration. The alumina ceramics prepared by the urea removal followed by sintering at 1500°C had porosity in the range 28–36 vol% with the rectangular rod‐shaped aligned pores.