Compact fiber Bragg grating dynamic strain sensor cum broadband thermometer for thermally unstable ambience

An instrument for simultaneous measurement of dynamic strain and temperature in a thermally unstable ambience has been proposed, based on fiber Bragg grating technology. The instrument can function as a compact and stand-alone broadband thermometer and a dynamic strain gauge. It employs a source wavelength tracking procedure for linear dependence of the output on the measurand, offering high dynamic range. Two schemes have been demonstrated with their relative merits. As a thermometer, the present instrumental configuration can offer a linear response in excess of 500 degrees C that can be easily extended by adding a suitable grating and source without any alteration in the procedure. Temperature sensitivity is about 0.06 degrees C for a bandwidth of 1 Hz. For the current grating, the upper limit of strain measurement is about 150 mu epsilon with a sensitivity of about 80 n epsilon Hz(-1/2). The major source of uncertainty associated with dynamic strain measurement is the laser source intensity noise, which is of broad spectral band. A low noise source device or the use of optical power regulators can offer improved performance. The total harmonic distortion is less than 0.5% up to about 50 mu epsilon, 1.2% at 100 mu epsilon and about 2.3% at 150 mu epsilon. Calibrated results of temperature and strain measurement with the instrument have been presented. Traces of ultrasound signals recorded by the system at 200 kHz, in an ambience of 100-200 degrees C temperature fluctuation, have been included. Also, the vibration spectrum and engine temperature of a running internal combustion engine has been recorded as a realistic application of the system.

Application of z-COSY experiment and its variant for accurate chiral discrimination by H-1 NMR

We report the application of z-COSY experiment and a band selected version of it by employing a selective 90 degrees pulse entitled BASE-z-COSY for precise chiral discrimination, quantification of enantiomeric excess and the analyses of the H-1 NMR spectra of chiral molecules aligned in the chiral liquid crystalline solvent poly-gamma-benzyl-L-glutamate (PBLG). We have demonstrated their applicability for obtaining very high resolution in the H-1 NMR spectra of small organic molecules. It is well known that the commonly employed z-COSY experiment disentangles the spectral complexity, provides pure phase spectra with high resolution, aids in the complete spectral analyses, in addition to yielding information on relative signs of the Couplings. The BASE-z-COSY experiment possesses all these properties, permits the measure of enantiomeric excess, in addition to large saving of instrument time.

A multistep transversal linearization (MTL) method in non-linear dynamics through a Magnus characterization

A new form of a multi-step transversal linearization (MTL) method is developed and numerically explored in this study for a numeric-analytical integration of non-linear dynamical systems under deterministic excitations. As with other transversal linearization methods, the present version also requires that the linearized solution manifold transversally intersects the non-linear solution manifold at a chosen set of points or cross-section in the state space. However, a major point of departure of the present method is that it has the flexibility of treating non-linear damping and stiffness terms of the original system as damping and stiffness terms in the transversally linearized system, even though these linearized terms become explicit functions of time. From this perspective, the present development is closely related to the popular practice of tangent-space linearization adopted in finite element (FE) based solutions of non-linear problems in structural dynamics. The only difference is that the MTL method would require construction of transversal system matrices in lieu of the tangent system matrices needed within an FE framework. The resulting time-varying linearized system matrix is then treated as a Lie element using Magnus’ characterization [W. Magnus, On the exponential solution of differential equations for a linear operator, Commun. Pure Appl. Math., VII (1954) 649–673] and the associated fundamental solution matrix (FSM) is obtained through repeated Lie-bracket operations (or nested commutators). An advantage of this approach is that the underlying exponential transformation could preserve certain intrinsic structural properties of the solution of the non-linear problem. Yet another advantage of the transversal linearization lies in the non-unique representation of the linearized vector field – an aspect that has been specifically exploited in this study to enhance the spectral stability of the proposed family of methods and thus contain the temporal propagation of local errors. A simple analysis of the formal orders of accuracy is provided within a finite dimensional framework. Only a limited numerical exploration of the method is presently provided for a couple of popularly known non-linear oscillators, viz. a hardening Duffing oscillator, which has a non-linear stiffness term, and the van der Pol oscillator, which is self-excited and has a non-linear damping term.

Implantation Induced Hardening of Nanocrystalline Titanium Thin Films

Formation of nanocrystalline TiN at low temperatures was demonstrated by combining Pulsed Laser Deposition (PLD) and ion implantation techniques. The Ti films of nominal thickness similar to 250 nm were deposited at a substrate temperature of 200 degrees C by ablating a high pure titanium target in UHV conditions using a nanosecond pulsed Nd:YAG laser operating at 1064 nm. These films were implanted with 100 keV N+ ions with fluence ranging from 1.0 x 10(16) ions/cm(2) to 1.0 x 10(17) ions/cm(2). The structural, compositional and morphological evolutions were tracked using Transmission Electron Microscopy (TEM), Secondary Ion Mass Spectrometry (SIMS) and Atomic Force Microscopy (AFM), respectively. TEM analysis revealed that the as-deposited titanium film is an fcc phase. With increasing ion fluence, its structure becomes amorphous phase before precipitation of nanocrystalline fcc TiN phase. Compositional depth profiles obtained from SIMS have shown the extent of nitrogen concentration gradient in the implantation zone. Both as-deposited and ion implanted films showed much higher hardness as compared to the bulk titanium. AFM studies revealed a gradual increase in surface roughness leading to surface patterning with increase in ion fluence.

Composite scheme using localized relaxation with non-standard finite difference method for hyperbolic conservation laws

Non-standard finite difference methods (NSFDM) introduced by Mickens [Non-standard Finite Difference Models of Differential Equations, World Scientific, Singapore, 1994] are interesting alternatives to the traditional finite difference and finite volume methods. When applied to linear hyperbolic conservation laws, these methods reproduce exact solutions. In this paper, the NSFDM is first extended to hyperbolic systems of conservation laws, by a novel utilization of the decoupled equations using characteristic variables. In the second part of this paper, the NSFDM is studied for its efficacy in application to nonlinear scalar hyperbolic conservation laws. The original NSFDMs introduced by Mickens (1994) were not in conservation form, which is an important feature in capturing discontinuities at the right locations. Mickens [Construction and analysis of a non-standard finite difference scheme for the Burgers–Fisher equations, Journal of Sound and Vibration 257 (4) (2002) 791–797] recently introduced a NSFDM in conservative form. This method captures the shock waves exactly, without any numerical dissipation. In this paper, this algorithm is tested for the case of expansion waves with sonic points and is found to generate unphysical expansion shocks. As a remedy to this defect, we use the strategy of composite schemes [R. Liska, B. Wendroff, Composite schemes for conservation laws, SIAM Journal of Numerical Analysis 35 (6) (1998) 2250–2271] in which the accurate NSFDM is used as the basic scheme and localized relaxation NSFDM is used as the supporting scheme which acts like a filter. Relaxation schemes introduced by Jin and Xin [The relaxation schemes for systems of conservation laws in arbitrary space dimensions, Communications in Pure and Applied Mathematics 48 (1995) 235–276] are based on relaxation systems which replace the nonlinear hyperbolic conservation laws by a semi-linear system with a stiff relaxation term. The relaxation parameter (λ) is chosen locally on the three point stencil of grid which makes the proposed method more efficient. This composite scheme overcomes the problem of unphysical expansion shocks and captures the shock waves with an accuracy better than the upwind relaxation scheme, as demonstrated by the test cases, together with comparisons with popular numerical methods like Roe scheme and ENO schemes.

Electron paramagnetic resonance studies on multiferroic DyMnO3 and Dy0.5Sr0.5MnO3

Electron paramagnetic resonance (EPR) studies and magnetic measurements were carried out on single crystals of multiferroic DyMnO3 in hexagonal as well as orthorhombic structures. The interesting effect of strontium dilution on the frustrated antiferromagnetism of DyMnO3 is also probed using EPR. The line shapes are fitted to broad Lorentzian in the case of pure DyMnO3 and to modified Dysonian in the case of Dy0.5Sr0.5MnO3. The linewidth, integrated intensity, and geff derived from the signals are analyzed as a function of temperature. The results of magnetization measurements corroborate with EPR results. Our study clearly reveals the signature of frustrated magnetism in pure DyMnO3 systems. It is found that antiferromagnetic correlations in these systems persist even above the transition. Moreover, a spin-glass-like behavior in Dy0.5Sr0.5MnO3 is indicated by a steplike feature in the EPR signals at low fields.

Enhanced dielectric response of ZrO2 upon Ti doping and introduction of O vacancies

We determine the electronic properties and dielectric response of zirconia (ZrO2) with oxygen vacancies (O vacancies) and Ti doping using first-principles density functional theory calculations based on pseudopotentials and a plane wave basis. We find significantly enhanced static dielectric response in zirconia with Ti doping and introduction of oxygen vacancies. Softening of phonon modes are responsible for the enhanced dielectric response of doped samples compared to pure zirconia.

Do inventory management practices affect economic performance? An empirical evaluation of the machine tool SMEs in Bangalore

Inventory management (IM) has a decisive role in the enhancement of manufacturing industry's competitiveness. Therefore, major manufacturing industries are following IM practices with the intention of improving their performance. However, the effort to introduce IM in SMEs is very limited due to lack of initiation, expertise, and financial constraints. This paper aims to provide a guideline for entrepreneurs in enhancing their IM performance, as it presents the results of a survey based study carried out for machine tool Small and Medium Enterprises (SMEs) in Bangalore. Having established the significance of inventory as an input, we probed the relationship between IM performance and economic performance of these SMEs. To the extent possible all the factors of production and performance indicators were deliberately considered in pure economic terms. All economic performance indicators adopted seem to have a positive and significant association with IM performance in SMEs. On the whole, we found that SMEs which are IM efficient are likely to perform better on the economic front also and experience higher returns to scale.

Global lopsided instability in a purely stellar galactic disc

It is shown that pure exponential discs in spiral galaxies are capable of supporting slowly varying discrete global lopsided modes, which can explain the observed features of lopsidedness in the stellar discs. Using linearized fluid dynamical equations with the softened self-gravity and pressure of the perturbation as the collective effect, we derive self-consistently a quadratic eigenvalue equation for the lopsided perturbation in the galactic disc. On solving this, we find that the ground-state mode shows the observed characteristics of the lopsidedness in a galactic disc, namely the fractional Fourier amplitude A(1), increases smoothly with the radius. These lopsided patterns precess in the disc with a very slow pattern speed with no preferred sense of precession. We show that the lopsided modes in the stellar disc are long-lived because of a substantial reduction (approximately a factor of 10 compared to the local free precession rate) in the differential precession. The numerical solution of the equations shows that the groundstate lopsided modes are either very slowly precessing stationary normal mode oscillations of the disc or growing modes with a slow growth rate depending on the relative importance of the collective effect of the self-gravity. N-body simulations are performed to test the spontaneous growth of lopsidedness in a pure stellar disc. Both approaches are then compared and interpreted in terms of long-lived global m = 1 instabilities, with almost zero pattern speed.

Formation of ω-Al7Cu2Fe phase during laser processing of quasicrystal-forming Al-Cu-Fe alloy

The formation of an ω-Al7Cu2Fe phase during laser cladding of quasicrystal-forming Al65Cu23.3Fe11.7 alloy on a pure aluminium substrate is reported. This phase is found to nucleate at the periphery of primary icosahedral-phase particles. A large number of ω-phase particles form an envelope around the icosahedral phase. On the outer side, they form an interface with an agr-Al solid solution. Detailed transmission electron microscopic observations show that the ω phase exhibits an orientation relationship with the icosahedral phase. Analysis of experimental results suggests that the ω phase forms by precipitation on an icosahedral phase by heterogeneous nucleation and grows into the aluminium-rich melt until supersaturation is exhausted. The microstructural observations are explained in terms of available models of phase transformations.

On the PAPR of cosets of linear codes

Employing an error control code is one of the techniques to reduce the Peak-to-Average Power Ratio (PAPR) in a Orthogonal Frequency Division Multiplexing system, a well known class of such codes being the cosets of Reed-Muller codes. In this paper, we consider the class of such coset-codes of arbitrary linear codes and present a method of doubling the size of such a code without increasing the PAPR, by combining two such binary coset-codes. We identify the conditions under which we can employ this doubling more than once with no marginal increase in the PAPR value. Given a PAPR and length, our method has enabled to get the best coset-code (in terms of the size). Also, we show that the PAPR information of the coset-codes of the extended codes is obtainable from the PAPR of the corresponding coset-codes of the parent code. We have also shown a special type of lengthening is useful in PAPR studies.

Influence of surfactant and annealing temperature on optical properties of sol-gel derived nano-crystalline TiO2 thin films

Titanium dioxide thin films have been synthesized by sol-gel spin coating technique on glass and silicon substrates with and without surfactant polyethylene glycol (PEG). XRD and SEM results confirm the presence of nano-crystalline (anatase) phase at an annealing temperature of 300 degrees C. The influence of surfactant and annealing temperature on optical properties of TiO2 thin films has been studied. Optical constants and film thickness were estimated by Swanepoel's (envelope) method and by ellipsometric measurements in the visible spectral range. The optical transmittance and reflectance were found to decrease with an increase in PEG percentage. Refractive index of the films decreased and film thickness increased with the increase in percentage of surfactant. The refractive index of the un-doped TiO2 films was estimated at different annealing temperatures and it has increased with the increasing annealing temperature. The optical band gap of pure TiO2 films was estimated by Tauc's method at different annealing temperature. (C) 2010 Elsevier B.V. All rights reserved.

THE BERGMAN KERNEL FUNCTION

In this note, we point out that a large family of n x n matrix valued kernel functions defined on the unit disc D subset of C, which were constructed recently in [9], behave like the familiar Bergman kernel function on ID in several different ways. We show that a number of questions involving the multiplication operator on the corresponding Hilbert space of holomorphic functions on D can be answered using this likeness.

Slim P‐E hysteresis loop and anomalous dielectric response in sol-gel derived antiferroelectric PbZrO3 thin films

Sol-gel derived PbZrO3 (PZ) thin films have been deposited on Pt(111)/Ti/SiO2/Si substrate and according to the pseudotetragonal symmetry of PZ, the relatively preferred (110)t oriented phase formation has been noticed. The room temperature P‐E hysteresis loops have been observed to be slim by nature. The slim hysteresis loops are attributed to the [110]t directional antiparallel lattice motion of Pb ions and by the directionality of the applied electric field. Pure PZ formation has been characterized by the dielectric phase transition at 235 °C and antiferroelectric P‐E hysteresis loops at room temperature. Dielectric response has been characterized within a frequency domain of 100 Hz–1 MHz at various temperatures ranging from 40 to 350 °C. Though frequency dispersion of dielectric behaves like a Maxwell–Wagner type of relaxation, ω2 dependency of ac conductivity indicates that there must be G‐C equivalent circuit dominance at high frequency. The presence of trap charges in PZ has been determined by Arrhenius plots of ac conductivity. The temperature dependent n (calculated from the universal power law of ac conductivity) values indicate an anomalous behavior of the trapped charges. This anomaly has been explained by strongly and weakly correlated potential wells of trapped charges and their behavior on thermal activation. The dominance of circuit∕circuits resembling Maxwell–Wagner type has been investigated by logarithmic Nyquist plots at various temperatures and it has been justified that the dielectric dispersion is not from the actual Maxwell–Wagner-type response.

A quantum stochastic Lie-Trotter product formula

A Trotter product formula is established for unitary quantum stochastic processes governed by quantum stochastic differential equations with constant bounded coefficients.