Srinagar, India

The National Institute of Technology, Srinagar is a national engineering institute located in Hazratbal, Srinagar, Jammu and Kashmir, India and an engineering institute of Northern India, along with other NITs and IITs of India. It is one of the 30 NITs in India, and as such is directly under the control of the Ministry of Human Resource Development . It is the 7th in the chain of 17 NITs established as a part of the Second Five Year Plan by the Government of India. Refer History of RECs for more information on the Regional Engineering College established during the 2nd five year plan . The institute has recognition as an Institute of National Importance under NIT act of Parliament and has produced more than 8000 graduates. Wikipedia.

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Harmain G.A.,National Institute of Technology Srinagar
Theoretical and Applied Fracture Mechanics | Year: 2010

Many engineering components are subjected to variable amplitude loading history. It is well known that retardation in fatigue crack growth occurs due to application of single overloads in a constant amplitude loading block. Many models have been proposed to capture this counter intuitive phenomenon which has resulted in improved understanding of retardation effect following tensile overloads and consequently resulting in better life prediction models. The proposed study is focused on to evaluation of retardation in fatigue life due to application of a single overload. A model for prediction of crack growth and crack growth rate following single overloads is presented. Several modifications to Wheeler's growth idea are proposed, which incorporate a consideration for effective stress intensity factor, based on Elber's concept of crack closure, relationship between overload ratio and the Wheeler's exponent, and fatigue growth rate calculations. The results presented here show that plastic zone interaction following overload and the consideration of crack closure explain retardation effect following a single overload. Correlation between analysis and experimental data obtained from several sources in literature show that the scheme, is robust and provides an insight into the nonlinear aspect of crack growth results. The model has been tested for 2024-T3 aluminum alloy and 6061-T6 aluminum alloy and thorough calibrations performed, established the fidelity of the program. © 2009 Elsevier Ltd. All rights reserved.

Wani M.F.,National Institute of Technology Srinagar
International Journal of Applied Ceramic Technology | Year: 2010

The mechanical and tribological properties of a nano-Si3N 4/nano-BN composite were studied. The composite was prepared via high-energy mechanical milling and subsequent spark plasma sintering. Y 2O3 and Al2O3 were used as sintering additives. After sintering, the average crystalline size of Si 3N4 and BN was 50 nm. Hardness (Vicker and Knoop) was evaluated under a high load of 0.05-2.0 kg for the nano/nano- and the micro/micro-Si3N4/BN composite with the same composition. The indentation fracture toughness values of both composites were also evaluated. Tribological studies were conducted to study the friction and wear behavior of both composites. A friction coefficient of 0.4-0.7 was obtained for the nano-S3N4/nano-BN composite under a normal load of 20-22 N, whereas, a friction coefficient of 0.37 was obtained for the micro-Si3N4/micro-BN composite. Specific wear coefficients of 0.418 × 10-4 and 0.625 × 10-4 mm 3/N/m were obtained for nano-sized and micro-sized Si 3N4/BN composites, respectively. Higher hardness, higher fracture toughness, and lower wear were observed in the nano-sized composite, as compared with the micro-sized composite. © 2009 The American Ceramic Society.

Nissar A.,National Institute of Technology Srinagar | Mir A.H.,National Institute of Technology Srinagar
Digital Signal Processing: A Review Journal | Year: 2010

Steganography is the art of secret communication and steganalysis is the art of detecting the hidden messages embedded in digital media using steganography. Both steganography and steganalysis have received a great deal of attention from law enforcement and the media. In the past years many powerful and robust methods of steganography and steganalysis have been reported in the literature. In this paper, we classify and give an account of the various approaches that have been proposed for steganalysis. Some promising methods for statistical steganalysis have also been identified. © 2010 Elsevier Inc. All rights reserved.

Khan G.R.,National Institute of Technology Srinagar
Journal of Lightwave Technology | Year: 2013

An exact analytical formulism obtained directly by solving a system of rate and propagation equations in the presence of pump excited-state absorption is presented on the basis of four-band transition scheme in radially symmetric and longitudinally uniform monomode erbium doped silica fiber lasers. The exact analytical expressions are determined for overall gain, small-signal gain, pump intensity threshold, lasing threshold condition, and optimal fiber length in terms of alleviative measurable quantities of photon intensities, transition rates, absorption and emission cross sections, and reflectivity of mirrors. Mutatis mutandis, the formulas bear a verisimilitude to analytical expressions appearing in the literature for these parameters. © 2013 IEEE.

Bhat A.H.,National Institute of Technology Srinagar | Langer N.,National Institute of Technology Srinagar
IEEE Transactions on Power Electronics | Year: 2014

This paper presents a control strategy using optimized switching sequences which results in capacitor voltage balancing of a three-phase neutral-point-clamped rectifier. In front end rectifiers, magnitude and lag angle of reference current vector (w.r.t supply voltage vector) varies depending upon amount of reactive power compensation and load current. Accordingly, the effectiveness of small and medium vectors (using SVPWM) for same switching state varies in each sector and its regions. This observation along with detailed analysis of current pattern for both the capacitors and their effect on neutral point voltage forms the basis of the proposed approach, which is to modify the reference vector for changing the number of sampling periods within each sector and its regions. The rectifier exhibits excellent performance in terms of other critical parameters like unity input power factor, low input current THD, minimum possible switching losses, reduced-rippled, and well-regulated dc-bus voltage, particularly, the capacitor voltage balancing. The proposed control algorithm is tested through exhaustive simulations and validated through experimental results obtained from a laboratory prototype of the rectifier. © 1986-2012 IEEE.

Sultan K.,National Institute of Technology Srinagar | Ikram M.,National Institute of Technology Srinagar | Asokan K.,Inter University Accelerator Center
Vacuum | Year: 2014

Polycrystalline bulk samples of PrFe1-xMnxO 3 (x = 0.0, 0.1, 0.3, 0.5) were synthesized by solid state reaction method to understand their structural, optical and dielectric properties. X-ray diffraction (XRD) and Raman spectroscopy were investigated to confirm chemical phase and the orthorhombic pbnm structure. As the concentration of Mn increases, the lattice parameter b increases while the lattice parameters a and c/√2 decrease but the change of former is less than later. PrFe1-xMn xO3 exhibits O-type (a < c/√2 < b) orthorhombic pbnm structure upto x = 0.5. From XRD it is also evident that the peaks shift towards higher 2θ values with increase in Mn content indicating the development of strain in the crystal structure possibly due to Jahn-Teller distortion after the incorporation of Mn3+ ions in the parent compound PrFeO3. From the Raman study, the modes exhibit a blue shift with broadening of spectral features in the doped samples. The observed shift in wave number with doping clearly indicates change in the bond lengths of Fe-O/Mn-O as well as their impact on FeO6/MnO6 octahedra. The dielectric constant (É′) and dielectric loss (tan δ) are also studied as a function of frequency and temperature. The dielectric constant and ac conductivity increases with Mn doping. The variation of dielectric properties such as ac conductivity, tan δ and É′ suggests that small polarons contribute to the conduction mechanism. Activation energy (Eσ) and optical band gap (E g) decreases with the concentration of Mn. The observed higher values of these quantities reveals that there is hopping between Mn3+ to Mn4+ and Fe3+ to Fe2+ at the octahedral sites of the compound. Possible mechanism contributing to these processes has been discussed. © 2013 Elsevier Ltd. All rights reserved.

Najar M.H.,National Institute of Technology Srinagar | Majid K.,National Institute of Technology Srinagar
Journal of Materials Science: Materials in Electronics | Year: 2013

Materials having high thermal stability and electrical conductivity form potential candidates for electronics. In this study, a thermally stable nanocomposite of nanophotoadduct of pentaamminechlorocobalt(III) chloride with hexamine and polythiophene (PTh) was prepared by oxidative chemical polymerization in the presence of FeCl3 as oxidant and thiophene monomer. Photoadduct was obtained by photoirradiation followed by substitution with hexamine ligand which was then milled in G5 planetary ball mill to obtain nanophotoadduct which is confirmed by X-ray powder diffraction. The formation of nanophotoadduct and its incorporation in PTh structure was endorsed by fourier transform infrared analysis. Empirical formula of the nanophotoadduct was found to be [Co(NH3)2(OH)3C6H 12N4]·2H2O. SEM analysis revealed uniform distribution of nanophotoadduct in PTh matrix. Crystallite size and strain analysis revealed further decrease in size from 34 (nanophotoadduct) to 15 nm (nanocomposite) using different methods of analysis which were well correlated. This size reduction was attributed to the microstrain in the nanocomposite. TG revealed that the nanocomposite and PTh underwent 62 and 80 % weight loss at 1,000 C respectively which clearly indicated the higher thermal stability of nanocomposite compared to pure PTh. Little change in the glass transition temperatures of PTh (170 C) and nanocomposite (167 C) is observed from DSC which indicated smaller plasticizing effect of nanophotoadduct. I-V curves of nanophotoadduct showed its diode like behavior while as nanocomposite depict nearly ohmic behavior. These results illustrate that the nanophotoadduct play two important roles, one that it acts as a Schottky diode material and second that it increases the conductance and thermal stability of PTh. Nanocomposite thus obtained can operate at relatively high temperatures in electrical appliances. © 2013 Springer Science+Business Media New York.

Shah M.A.,National Institute of Technology Srinagar
Materials Science Forum | Year: 2013

Magnesium oxide (MgO) nanoneedles have been prepared by an environmentally benign route. The route is based on a very simple reaction of magnesium powder and double distilled water at very low temperature of 50°C. The formation of nanostructures by the reaction of metals with water is suggested to occur due of decomposition of water by the metal giving hydrogen. The nanoneedles have an average width of 20nm and length up to 1μm. Compared with other methods, the present method is fast, economical, low temperature and free of pollution which will make it suitable for large scale production. © (2013) Trans Tech Publications, Switzerland.

Khan G.R.,National Institute of Technology Srinagar
Optical Fiber Technology | Year: 2012

Analytical solutions to rate and propagation equations describing gain in terms of photon intensities, transition rates, and absorption and emission cross-sections is determined in radially symmetric and longitudinally uniform monomode erbium doped silica fiber in presence of pump excited-state absorption effect for a pumping wavelength of 514.5 nm under the steady-state conditions with the help of a homogenous four-band transition scheme. © 2012 Elsevier Inc. All rights reserved.

Bhat A.H.,National Institute of Technology Srinagar | Langer N.,National Institute of Technology Srinagar
International Journal of Electrical Power and Energy Systems | Year: 2014

In this paper, an improved performance three-phase neutral-point clamped bidirectional rectifier with modified control scheme is proposed. The proposed control strategy takes into consideration the amount/degree of deviation of source voltage from desired rated value during supply perturbation and accordingly modifies the reference current template for each phase individually which is termed as compensated reference current. In other words, magnitude, shape and phase of compensated reference current waveform for each phase are different depending on amount of deviation of that phase. A complete mathematical model of rectifier using PWM technique is developed. The performance of the converter is evaluated in terms of near unity input power factor, low input current THD, reduced ripple factor of the regulated DC output voltage and particularly the neutral point voltage balance under different load conditions both for rectification and inversion modes of operation. It is shown that the three-level ac to dc converter with proposed control scheme displays better performance under source voltage perturbations such as voltage sag, swell, unbalance, harmonics, frequency variations as well as phase angle deviations which are regularly encountered in practical environment. © 2013 Elsevier Ltd. All rights reserved.

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