Dynamic modelling of power plant turbines for controller design

A nonlinear dynamic model of a steam turbine is formulated from approximation of fundamental equations, and does not rely on empirical relations. The model can be used as a part of an integrated power system model for dynamic simulation and control system design.     

Combustion process in a spark ignition engine: analysis of cyclic peak pressure and peak pressure angle oscillations

In this paper we analyze the cycle-to-cycle variations of peak pressure p _max and peak pressure angle α _pmax in a four-cylinder spark ignition engine. We examine the experimental time series of p _max and α _pmax for three different spark advance angles. Using standard statistical techniques such as return maps and histograms we show that depending on the spark advance angle, there are significant differences in the fluctuations of p _max and α _pmax . We also calculate the multiscale entropy of the various time series to estimate the effect of randomness in these fluctuations. Finally, we explain how the information on both p _max and α _pmax can be used to develop optimal strategies for controlling the combustion process and improving engine performance.     

Synthesis of flavanones by use of anhydrous potassium carbonate as an inexpensive, safe, and efficient basic catalyst

Anhydrous potassium carbonate has been utilized as an inexpensive, safe, and efficient basic catalyst for the synthesis of flavanones starting either from 2′-hydroxychalcones or from 2′-hydroxyacetophenones. In both the cases the favored reaction condition was either refluxing in a solvent with added catalyst or microwave irradiation on the catalyst.     

Spectroscopic and thermodynamic study of charge transfer interaction between vitamin B6 and p-chloranil in aqueous ethanol mixtures of varying composition

Charge transfer complexes of 1:1 stoichiometry have been found to form between vitamin B(6) (pyridoxine hydrochloride) and a series of electron acceptors including p-chloranil. Since vitamin B(6) is soluble in water while the electron acceptors are insoluble in water but soluble in ethanol, the medium chosen for study is water-ethanol mixture. From the trends in the CT absorption bands the vertical ionization potential of vitamin B(6) has been determined to be 8.12 eV. The enthalpy and entropy of formation of the complex between p-chloranil and vitamin B(6) have been determined by estimating the formation constant (K) spectroscopically at four different temperatures in 75% ethanol-water mixture. Again, the magnitude of K has been found to decrease noticeably with decrease in dielectric constant of the medium (as the percentage of ethanol in the aqueous-ethanol mixture is increased). A plausible explanation for this has been given in terms of hydrolysis of pyridoxine hydrochloride.     

Dielectric properties near the isotropic-smectic-C* phase transition

The dielectric properties in the vicinity of the isotropic-smectic-C* phase transition in ferroelectric liquid crystals are discussed. The temperature and frequency dependence of the complex dielectric permittivity in both the phases of the transition are calculated. The theoretical phase diagram of the dielectric permittivity is studied.     

Absorption spectra of nitroanilines in micellar solution--II

The absorption spectra of nitroanilines (o-, m- and p-) in aqueous and nonaqueous solution of neutral surfactant-Triton X-100 (TX-100) reveal many interesting phenomena. Nitroanilines and TX-100 behave as electron acceptor and donor, respectively, in both media during charge-transfer (CT) complex formation though water plays an important role in aqueous media. The thermodynamic and spectrophotometric parameters of nitroanilines-TX-100 interactions in two media have been determined and the electron accepting capability among the nitroanilines have been also established. In addition to this, role of surface in CT interaction, the site of CT interaction, intensity and stability of CT interaction between nitroanilines and TX-100 have been pointed out.     

Absorption spectrometric study of molecular complex formation between [60]fullerene and a series of methylated pyridines

[60]fullerene has been shown to form 1:1 molecular complexes with pyridine and some methylated pyridines such as 2-picoline, 3-picoline, 4-picoline, 2,6-lutidine and 2,4,6-collidine in CCl4 medium by absorption spectrometric method. Well defined charge transfer (CT) bands have been observed for complexes of C60 with all the pyridines studied except 4-picoline. From an analysis of the trends in the CT absorption bands the ionisation potentials of the methylpyridines have been determined. The electron affinity of C60 has also been determined from the spectral data. The formation constants of the complexes exhibit a very good linear free energy relationship from which the Hammett p parameter for the complexation process is found to be -2.96.     

Studies on the molecular interaction of phenazine dyes with Triton X-100

The absorption spectra of phenazine dyes such as phenosafranin (PSF), safranin-O (Saf-O), and safranin-T (Saf-T) in aqueous solution of Triton X-100 (TX-100) show that phenazine dyes form 1:1 charge-transfer (CT) or electron-donor-acceptor (EDA) complex with TX-100. The photogalvanic and photoconductivity studies also support the above interaction. From the thermodynamic, spectrophotometric and photophysical parameters of these complexes, the abilities of dyes to accept electron are found to be in the order: PSF > Saf-O > Saf-T. There is a good correlation among the spectral and thermodynamic properties of these complexes.     

Spectrophotometric and thermodynamic studies of [60]fullerene/methylbenzene charge transfer complexes

The absorption spectra of charge-transfer (CT) complexes of [60]fullerene with liquid methylbenzenes, viz. toluene, o-xylene, m-xylene, p-xylene and mesitylene have been investigated in CCl(4) medium. An absorption band due to CT transition is observed in each case in the visible region. The experimental CT transition energies are well correlated (through Mulliken's equation) with the ionisation potentials (I(D)) of the series of methylbenzenes studied. From an analysis of this variation the electron affinity of [60]fullerene has been found to be 2.32 eV. The degrees of charge transfer in the ground state of the complexes have been found to be very low (0.66-0.775%). It has been found that these methylbenzenes form stable 1:1 complexes with [60]fullerene. Formation constants of the complexes have been determined at four different temperatures from which the enthalpies and entropies of formation of the complexes have been obtained. The experimentally determined formation constants of the complexes of [60]fullerene with methylbenzenes exhibit a very good linear free energy relationship (Chem. Rev. 53 (1953) 191).     

Stochastic orders of the Marshall-Olkin extended distribution

A general method of introducing a parameter, called tilt parameter, has been discussed by Marshall and Olkin (1997) to give more flexibility in modelling. In this paper, we take the tilt parameter of the Marshall-Olkin extended family as a random variable. The closure of this model under different stochastic orders viz. ageing intensity order, likelihood ratio order, shifted likelihood ratio orders and shifted hazard rate orders is discussed.