Study on the quality of interference fringes from a pulsed UV source for application in a biprism based fiber Bragg grating writing

This paper presents a study on the quality of interference fringes formed from a pulsed UV (255 nm, 5.6 kHz, and 40 ns) source for an application in writing fiber Bragg gratings (FBGs). The interference fringes of separation of about 8 microm, formed by a biprism of apex angle 2 degrees , were studied for their contrast, evolution of contrast, and positional and intensity stability over a period of 5 min (over 10(6) pulses). Second harmonic UV (255 nm) sources of different spatial coherence and pointing stability characteristics were employed as the inputs. It is established that the UV fringes contrast and interference pattern stability with time is largely controlled by the optical resonator geometry of the fundamental wavelength (510 nm) copper vapor laser (CVL) oscillator. In particular, the generalized diffraction filtered resonator (GDFR) CVL produced the highest quality second harmonic beam with the highest fringes contrast and stability. The implications of these results were studied by employing these UV sources for the fabrication of the C-band FBGs by a 24 degrees apex angle biprism.     

Grafted hydroxypropyl guargum: Development, characterization and application as flocculating agent

Synthesis of hydroxypropyl guargum-g-polyacrylamide was carried out by ceric ion induced redox polymerization technique at 28±1°C. The graft copolymer was characterized by IR and thermal analysis. The flocculation performance of graft copolymer was tested in 1 wt% coal suspension.     

Thermo-optical parameters measured in ytterbium-doped potassium gadolinium tungstate

Oriented absorption and fluorescence spectra, refractive indices, thermal expansion, and thermal conductivities are reported for the anisotropic laser material ytterbium-doped potassium gadolinium tungstate, Yb3+:KGd(WO4)2. Measurements of negative values for dn/dT lead to the report of several useful athermal orientations for laser propagation.     

Inertia effects in a conical porous bearing with a viscoelastic lubricant

The effects of the inertia and porosity of the bearing material were investigated for conical and squeeze film bearings with a viscoelastic lubricant by the method of averaged inertia. The inertia forces reduce the loadbearing capacity. The porosity of the material decreases the pressure and the load capacity. The effect of the elasticity of the lubricant is to increase the pressure and the load-bearing capacity at any point. The effects of the characteristics of the bearing on the pressure and the load-bearing capacity are presented graphically.     

Non-stationary power signal processing for pattern recognition using HS-transform

A new approach to time-frequency transform and pattern recognition of non-stationary power signals is presented in this paper. In the proposed work visual localization, detection and classification of non-stationary power signals are achieved using hyperbolic S-transform known as HS-transform and automatic pattern recognition is carried out using GA based Fuzzy C-means algorithm. Time-frequency analysis and feature extraction from the non-stationary power signals are done by HS-transform. Various non-stationary power signal waveforms are processed through HS-transform with hyperbolic window to generate time-frequency contours for extracting relevant features for pattern classification. The extracted features are clustered using Fuzzy C-means algorithm and finally the algorithm is optimized using genetic algorithm to refine the cluster centers. The average classification accuracy of the disturbances is 93.25% and 95.75% using Fuzzy C-means and genetic based Fuzzy C-means algorithm, respectively.     

Applicability of Cavity Modeling Technique to Analyze Complex Waveguide Structures Involving Cavity Cross Couplings

Wireless Personal Communications - In this paper, we propose modulation and coding scheme level drop scheme for LTE evolved multimedia broadcast/multicast service (eMBMS) by transmitting additional...     

The flocculation and rheological characteristics of hydrolyzed and unhydrolyzed grafted sodium alginate in aqueous solutions

Sodium alginate is a natural anionic polysaccharide obtained from natural and microbial resources. It is also used as a flocculating agent and thickener. It is grafted with polyacrylamide, in the presence of ceric ammonium nitrate (CAN) as an initiator. The graft copolymer (SAG‐g‐PAM) is again hydrolyzed with some amount of alkali. The flocculation characteristics of hydrolyzed graft copolymer (Hyd SAG‐g‐PAM) are compared with that of the unhydrolyzed ones, in 5 wt % kaolin and 10 wt % iron ore suspensions. The flocculation characteristics of the hydrolyzed graft copolymer are also compared with those of some of the commercial flocculants. The SAG‐g‐PAM and Hyd SAG‐g‐PAM are characterized by IR and intrinsic viscosity measurements. The rheological properties of aqueous solutions of hydrolyzed and unhydrolyzed graft copolymers are measured by Advanced AR‐1000 Rheometer. There is drastic enhancement in flocculation and viscosifying characteristics on hydrolysis of the graft copolymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1480–1488, 2004     

Development of non-leaching antibacterial coatings through quaternary ammonium salts of styrene based copolymers

Non-leaching antibacterial coatings through quaternary ammonium salts containing polymers were successfully produced in a facile way to provide infection resistant surfaces against multi drug resistant bacteria such as B. licheniformis. In order to do so, a series of random copolymers of styrene (S) and vinyl benzyl chloride (VBC) were synthesized by free radical polymerization technique and subsequently, VBC (V) was functionalized with N,N-dimethylhexadecylamine to introduce quaternary ammonium (QA) salts in the backbone of the copolymers. The copolymers showed an excellent film forming ability, thereby providing an ultrathin coating on various substrates such as metal (stainless steel), glass, polyethylene and polystyrene, as observed by SEM.The coatings were found to be uniform, non leachable in aqueous medium and exhibit good adhesion to various substrates. The antibacterial and antibiofilm activity of the non-leachable coating of random copolymers were screened against B. licheniformis. Among, the copolymer containing 75% quaternized VBC (75VSQA) having 16-C long alkyl chain was found to show maximum antibacterial and antibiofilm activity owing to an appropriate hydrophobic /hydrophilic balance. Their non-leachable antibacterial and antibiofim activity make these coatings suitable for many applications, e.g. marine paints, textile/hospital coatings etc.