Transient response of coupled non-linear non-conservative systems

This paper deals with an approximate method of analysis of non-linear, non-conservative systems of two degrees of freedom. The approximate equations for amplitude and phase are obtained by a generalized averaging technique based on the ultraspherical polynomial approximation. The method is illustrated by an example of a spring-mass-damper system.

Non-linear response of a gyrostabilized platform to transient input

In this paper the response of a gyrostabilized platform subjected to a transient torque has been analyzed by deliberately introducing non-linearity into the command of the servomotor. The resulting third-order non-linear differential equation has been solved by using a transformation technique involving the displacement variable. The condition under which platform oscillations may grow with time or die with time are important from the point of view of platform stabilization. The effect of deliberate addition of non-linearity with a view to achieving the ideal response—that is, to bring the platform back to its equilibrium position with as few oscillations as possible—has been investigated. The conditions under which instability may set in on account of the small transient input and small non-linearity has also been discussed. The analysis is illustrated by means of a numerical example. The results of analysis are compared with numerical solutions obtained on a digital computer.

Harmonic response of a shock mount employing dual-phase damping

In this note, the application of dual-phase damping to a simple shock mount experiencing a harmonic input is described. The damping ratio is a function of the relative displacement between the foundation and the mounted mass. The purpose of employing such a damping is to reduce the absolute transmissibility over the whole frequency range.

Dielectric and Electron Spin Resonance Spectroscopic Studies of Glassy Crystalline States of Organic Compounds

Dielectric studies of the glassy crystalline states of cyclohexanol, cyclohexanone, and camphor obtained by upercooling the plastic crystalline phase demonstrate the presence of characteristic a- and p-relaxations. The parameters of the a-relaxation fit the Vogel-Tammann-Fulcher (VTF) equation. ESR spin-probe studies of the glassy crystalline phase of cyclohexanol show that there is a marked decrease in the correlation time above the glasslike transition temperature. The present studies suggest the similarity between glassy crystals having long-range orientational disorder and glasses which are known to betra nslationally disordered.

Enhancement of immune response by the proteinaceous crystal of Bacillus thuringiensis Var thuringiensis

The proteinaceous crystal of Bacillus thuringiensis Var thuringiensis was found to enhance humoral immune response in rats and guinea pigs immunised with sheep red blood cells. The enhancement was due to the increased levels of both 19S and 7S antibodies in the sera of the treated animals. A novel synthesis of 7S haemolytic antibodies was observed in case of crystal treated animals.

Dielectric properties of Li2O-3B(2)O(3) glasses

The frequency and temperature dependences of the dielectric constant and the electrical conductivity of the transparent glasses in the composition Li2O-3B(2)O(3) were investigated in the 100 Hz-10 MHz frequency range. The dielectric constant and the loss in the low frequency regime were electrode material dependent. Dielectric and electrical relaxations were, respectively, analyzed using the Cole-Cole and electric modulus formalisms. The dielectric relaxation mechanism was discussed in the framework of electrode and charge carrier (hopping of the ions) related polarization using generalized Cole-Cole expression. The frequency dependent electrical conductivity was rationalized using Jonscher's power law. The activation energy associated with the dc conductivity was 0.80 +/- 0.02 eV, which was ascribed to the motion of Li+ ions in the glass matrix. The activation energy associated with dielectric relaxation was almost equal to that of the dc conductivity, indicating that the same species took part in both the processes. Temperature dependent behavior of the frequency exponent (n) suggested that the correlated barrier hopping model was the most apposite to rationalize the electrical transport phenomenon in Li2O-3B(2)O(3) glasses. These glasses on heating at 933 K/10 h resulted in the known nonlinear optical phase LiB3O5.

Response of a turbulent boundary layer to a step change in surface heat flux

Measurements of both the velocity and the temperature field have been made in the thermal layer that grows inside a turbulent boundary layer which is subjected to a small step change in surface heat flux. Upstream of the step, the wall heat flux is zero and the velocity boundary layer is nearly self-preserving. The thermal-layer measurements are discussed in the context of a self-preserving analysis for the temperature disturbance which grows underneath a thick external turbulent boundary layer. A logarithmic mean temperature profile is established downstream of the step but the budget for the mean-square temperature fluctuations shows that, in the inner region of the thermal layer, the production and dissipation of temperature fluctuations are not quite equal at the furthest downstream measurement station. The measurements for both the mean and the fluctuating temperature field indicate that the relaxation distance for the thermal layer is quite large, of the order of 1000θ0, where θ0 is the momentum thickness of the boundary layer at the step. Statistics of the thermal-layer interface and conditionally sampled measurements with respect to this interface are presented. Measurements of the temperature intermittency factor indicate that the interface is normally distributed with respect to its mean position. Near the step, the passive heat contaminant acts as an effective marker of the organized turbulence structure that has been observed in the wall region of a boundary layer. Accordingly, conditional averages of Reynolds stresses and heat fluxes measured in the heated part of the flow are considerably larger than the conventional averages when the temperature intermittency factor is small.

Effects of environment on surface-wave characteristics of a dielectric-coated conductor .4.

The problem of excitation of 11zultilayercd-graded-dielectric-coatedc onductor by a magnetic ring source is fornzulated in the ,form of a contour integrul which is rolved by using the method of steepest descent. Numerical evaluation of launching efiiency shows that high value of about 90 percent can be attained by choosing proper dimensions of the launcher with respect to the dimension of the surface wave line.

The dielectric coated conducting sphere - modal and near field characteristics.

A modal analysis and near-field study for a dielectric-coated conducting sphere excited by a delta function electric field source has been made. The structure can support an infinite number of modes theoretically. For equatorial excitation only odd order modes are excited, whereas for non-equatorial excitation both even and odd order modes are excited. The variation of the amplitude coefficients both internal and external exhibit a different nature of variation with respect to the various structure parameters for different modes. The field distributions both in the r and theta directions for non-equatorial excitation show good agreement between theory and experiment for the strongest mode.

Dielectric-lined rectangular metal waveguide

The propagation characteristics of electromagnetic waves in a dielectric-lined rectangular metal waveguide have been studied. The lining on the two side walls (E-plane) together with the air space in between them is considered as a homogeneous equivalent dielectric medium whose equivalent dielectric constant is derived by using electrostatic theory. The theoretical work is based on the fact that LSE and LSM modes can be propagated in a rectangular metal waveguide lined in the two longer sides (H-plane) by dielectric lining. Experimental verification of the guide wavelength at 'X', 'ku' and 'Ka' bands and cut-off frequency are reported.

Effect of mechanical cycling on the stress-strain response of a martensitic Nitinol shape memory alloy

An experimental investigation into the ambient temperature, load-controlled tension�tension fatigue behavior of a martensitic Nitinol shape memory alloy (SMA) was conducted. Fatigue life for several stress levels spanning the critical stress for detwinning was determined and compared with that obtained on an alloy similar in composition but in the austenitic state at room temperature. Results show that the fatigue life of the pseudo-plastic alloy is superior to superelastic shape memory alloy. The stress�strain hysteretic response, monitored throughout the fatigue loading, reveals progressive strain accumulation with the cyclic loading. In addition, the area of hysteresis and recoverable and frictional energies were found to decrease with increasing number of fatigue cycles. Post-mortem characterization of the fatigued specimens through calorimetry and fractography was conducted in order to get further insight into the fatigue micromechanisms. These results are discussed in terms of reversible and irreversible microstructural changes that take place during cyclic loading. Aspects associated with self-heating of martensitic alloy undergoing high frequency stress cycling are discussed.

The non-linear response of a gyrostabilized platform: Effects of correction torque time delay and of random inputs

First, the non-linear response of a gyrostabilized platform to a small constant input torque is analyzed in respect to the effect of the time delay (inherent or deliberately introduced) in the correction torque supplied by the servomotor, which itself may be non-linear to a certain extent. The equation of motion of the platform system is a third order nonlinear non-homogeneous differential equation. An approximate analytical method of solution of this equation is utilized. The value of the delay at which the platform response becomes unstable has been calculated by using this approximate analytical method. The procedure is illustrated by means of a numerical example. Second, the non-linear response of the platform to a random input has been obtained. The effects of several types of non-linearity on reducing the level of the mean square response have been investigated, by applying the technique of equivalent linearization and solving the resulting integral equations by using laguerre or Gaussian integration techniques. The mean square responses to white noise and band limited white noise, for various values of the non-linear parameter and for different types of non-linearity function, have been obtained. For positive values of the non-linear parameter the levels of the non-linear mean square responses to both white noise and band-limited white noise are low as compared to the linear mean square response. For negative values of the non-linear parameter the level of the non-linear mean square response at first increases slowly with increasing values of the non-linear parameter and then suddenly jumps to a high level, at a certain value of the non-linearity parameter.

Structural, dielectric, impedance and optical properties of CaBi2B2O7 glasses and glass-nanocrystal composites

Optically clear glasses were fabricated by quenching the melt of CaCO3-Bi2O3-B2O3 (in equimolecular ratio). The amorphous and glassy characteristics of the as-quenched samples were confirmed via the X-ray powder diffraction (XRD) and differential scanning calorimetric (DSC) studies These glasses were found to. have high thermal stability parameter (S). The optical transmission studies carried out in the 200-2500 nm wavelength range confirmed both the as-quenched and heat-treated samples to be transparent between 400 nm and 2500 nm. The glass-plates that were heat-treated just above the glass transition temperature (723 K) for 6 h retained approximate to 60% transparency despite having nano-crystallites (approximate to 50-100 nm) of CaBi2B2O7 (CBBO) as confirmed by both the XRD and transmission electron microscopy (TEM) studies. The dielectric properties and impedance characteristics of the as-quenched and heat-treated (723 K/6 h) samples were studied as a function of frequency at different temperatures. Cole-Cole equation was employed to rationalize the impedance data.

The pulse response of non-linear third order systems

The response of a third order non-linear system subjected to a pulse excitation is analysed. A transformation of the displacement variable is effected. The transformation function chosen is the solution of the linear problem subjected to the same pulse. With this transformation the equation of motion is brought into a form in which the method of variation of parameters is applicable for the solution of the problem. The method is applied to a single axis gyrostabilized platform subjected to an exponentially decaying pulse. The analytical results are compared with digital and analog computer solutions.

Optical, dielectric and morphological studies of sol-gel derived nanocrystalline TiO2 films

Nanocrystalline TiO2 films have been synthesized on glass and silicon substrates by sol-gel technique. The films have been characterized with optical reflectance/transmittance in the wavelength range 300-1000nm and the optical constants (n, k) were estimated by using envelope technique as well as spectroscopic ellipsometry. Morphological studies have been carried Out using atomic force microscope (AFM). Metal-Oxide-Silicon (MOS) capacitor was fabricated using conducting coating on TiO2 film deposited on silicon. The C-V measurements show that the film annealed at 300 degrees C has a dielectric constant of 19.80. The high percentage of transmittance, low surface roughness and high dielectric constant suggests that it can be used as an efficient anti-reflection coating on silicon and other optical coating applications and also as a MOS capacitor.