Economic and exergoeconomic investigation of 660 MW coal-fired power plant

Journal of Thermal Analysis and Calorimetry - Photocatalytically active titania thin films and powders were prepared via sol–gel route from TiCl4 precursor. Organic polymer hydroxypropyl...     

Low-dimensional chaotic response of axially accelerating continuum in the supercritical regime

Summary Nonlinear dynamics of one-mode approximation of an axially moving continuum such as a moving magnetic tape is studied. The system is modeled as a beam moving with varying speed, and the transverse vibration of the beam is considered. The cubic stiffness term, arising out of finite stretching of the neutral axis during vibration, is included in the analysis while deriving the equations of motion by Hamilton's principle. One-mode approximation of the governing equation is obtained by the Galerkin's method, as the objective in this work is to examine the low-dimensional chaotic response. The velocity of the beam is assumed to have sinusoidal fluctuations superposed on a mean value. This approximation leads to a parametrically excited Duffing's oscillator. It exhibits a symmetric pitchfork bifurcation as the axial velocity of the beam is varied beyond a critical value. In the supercritical regime, the system is described by a parametrically excited double-well potential oscillator. It is shown by numerical simulation that the oscillator has both period-doubling and intermittent routes to chaos. Melnikov's criterion is employed to find out the parameter regime in which chaos occurs. Further, it is shown that in the linear case, when the operating speed is supercritical, the oscillator considered is isomorphic to the case of an inverted pendulum with an oscillating support. It is also shown that supercritical motion can be stabilised by imposing a suitable velocity variation. Received 13 February 1997; accepted for publication 29 July 1997     

Proton and Gamma Ray Induced Gain Degradation in Bipolar Transistor

This paper describes the results of the effect of 24 MeV proton and ⁶⁰Co γ-irradiation on the collector characteristics and forward current gain of commercial bipolar transistor (npn 2N2219A). The transistor has been exposed to these radiations in the biased condition and the collector characteristics and forward current gain have been measured as a function of proton fluence and γ-dose. The observation is that both the proton and γ-irradiation induce significant gain degradation in the transistor. The results are discussed in terms of displacement damage produced by energetic protons and γ-radiation in the bulk of the semiconductor.     

Synthesis, spectral characterization and antihaemostatic activity of 1,2,4-triazoles incorporating 1,2,4-triazine rings

A simple and high yielding method for the integration of a 1,2,4-triazole ring with 1,2,4-triazine-5-one (4a-j) has been developed starting from 3-arylsydnones (1a-d). The structures were proved by their spectral data and screened for antihaemostatic activity.     

An unusual diterpene glycoside from the nuts of almond (Prunus amygdalus Batsch)

A new unusual kauranoid diterpene glycoside, named amygdaloside, was isolated from the nuts of almond (Prunus amygdalus). It's structure was established as 17-O-β-D-glucopyranoside ent-6,7-epoxy-6-hydroxyl-6,7-secokaur-19-oic acid, 6,19-lactone 16β17-diol on the basis of high-resolution 1D and 2D NMR spectral studies.     

Perturbation of eigenvalues of matrix pencils and the optimal assignment problem

We extend the perturbation theory of Vi?ik, Ljusternik and Lidski?? to the case of eigenvalues of matrix pencils. This extension allows us to solve certain degenerate cases of this theory. We show that the first order asymptotics of the eigenvalues of a perturbed matrix pencil can be computed generically by methods of min-plus algebra and optimal assignment algorithms. We illustrate this result by discussing a singular perturbation problem considered by Najman. To cite this article: M. Akian et al., C. R. Acad. Sci. Paris, Ser. I 339 (2004).     

Topological estimator of block entanglement for Heisenberg antiferromagnets

We introduce a computable estimator of block entanglement entropy for many-body spin systems admitting total singlet ground states. Building on a simple geometrical interpretation of entanglement entropy of the so-called valence bond states, this estimator is defined as the average number of common singlets to two subsystems of spins. We show that our estimator possesses the characteristic scaling properties of the block entanglement entropy in critical and noncritical one-dimensional Heisenberg systems. We invoke this new measure to examine entanglement scaling in the two-dimensional Heisenberg model on a square lattice revealing an "area law" for the gapped phase and a logarithmic correction to this law in the gapless phase.     

Stabilized parametric cooper-pair pumping in a linear array of coupled Josephson junctions

We present an experimentally realizable stabilized charge pumping scheme in a linear array of Cooper-pair boxes. The system design intrinsically protects the pumping mechanism from severe errors, especially current reversal and spontaneous charge excitation. The quantum Zeno effect is implemented to further diminish pumping errors. The characteristics of this scheme are considered from the perspective of improving the current standard. Such an improvement bears relevance to the closure of the so-called measurement triangle (see [D. Averin, Nature (London) 434, 285 (2005)).     

Surface roughness-aided hard X-ray emission from carbon nanotubes

Efficient low debris hard X-ray source based on multiwalled carbon nanotubes (MWNT) irradiated by intense, femtosecond laser over an intensity range of 10¹⁵–10¹⁷ W cm⁻² μm² is reported. The MWNT targets yield two orders of magnitude higher X-rays (indicating significant enhancement of laser coupling) and three orders of magnitude lower debris compared to conventional metallic targets under identical experimental conditions. The simple analytical model explains the basic experimental observations and also serves as a guide to design efficient targets to achieve low-debris laser plasma-based hard X-ray sources at low laser intensities suitable for multi-kHz operation.