D.K. Deshpande

Reduced memory listless speck image compression

Abstract In this paper a variant of the set partitioned embedded block coder (SPECK) image compression called listless SPECK (LSK) is presented. LSK operates without lists and is suitable for a fast, simple hardware implementation. LSK has a fixed predetermined memory requirement about 50% larger than needed for the independent image. Instead of lists, a state table with two bits per coefficient is used to keep track of the block coding and the information that has been encoded. LSK sparsely marks selected block nodes of insignificant blocks in the state table, in such a way that large groups of predictably insignificant pixels are easily identified and skipped during the coding process. The image data is stored as a one-dimensional recursive zigzag array for computational efficiency and algorithmic simplicity. Performance of the proposed algorithm on standard test images is nearly same as SPECK.

On the effect of temperature on the dielectric relaxation time of some benzene derivatives and certain of their binary mixtures

Dielectric relaxation behaviour of polar molecules in a non-polar solvent, or mixtures of these substances at different microwave frequencies and over a range of temperatures and concentrations give an idea about inter- and intra-molecular forces. Also such studies enable one to calculate thermodynamic parameters such as, the change of activation energy for dipole orientation (Δ G*), the enthalpy (Δ H*) and entropy (Δ S*) of activation. Such studies in the case of binary, ternary, etc. mixtures of polar molecules in pure liquid phase or in dilute solution phase of them in a non-polar solvent help in drawing certain quantitative conclusions regarding their relaxation behaviour as to whether a single component is responsible for observed microwave absorption, or a cooperative phenomenon (average) by all the dipoles of the mixture contribute to it. An experimental investigation is here performed on typical systems. With this in view, systematic dielectric measurements in a range of temperatures are carried out at a single microwave frequency on a single weight fraction in benzene of the four substituted phenols, namely, p-fluorophenylacetonitrile, p-bromonitrobenzene, m-bromonitrobenzene and 2-chloro-6-fluoro-benzaldehyde and on binary (1 : 1) mixtures of [p-2-chloro-6-fluoro-benzaldehyde + o-ethylphenol] and [p-fluorophenylacetonitrile + 2-n-butyl phenol] in benzene as solvent at different temperatures. The results are presented and discussed.

A new method for estimating excited state dipole moments of molecules from the solvent effect on their electronic spectra

Abstract Some comments are made on the paper entitled “Excited state dipole moments of some monosubstituted benzenes from the solvent effect on electronic absorption spectra” by Prabhumirashi et al . ( Spectrochim. Acta 39A , 663,1983) and a new method, which has been tested on some molecules and found satisfactory, is suggested for estimating the excited state dipole moment of molecules from the solvent effect on their electronic spectra.

Characterization of Some Liquid Crystals through Sound and Thermodynamic Parameters

The structural changes arising from transition between the mesophases of liquid crystalline materials can be better understood by ultrasound in conjunction with specific volume properties. In particular, ultrasonic studies are found to give clear information regarding the nature of the phase transition, pretransitional effects, and molecular ordering. For example, temperature corresponding to the maximum value of acoustic impedance, adiabatic compressibility, and temperature corresponding to the minimum value of ultrasonic velocity, Raos number, order parameter, and molar compressibility, in thermotropic liquid crystals are very useful in understanding their structural behavior. In view of these facts, it was thought worthwhile to study ultrasonic velocity with data available for density measurements on pure samples of nematics, namely, 4,4′-azoxy anisole and 4,4′-dibutoxy azoxy benzene. The results of this work, are presented in this article and discussed.

A study on thermodynamic and sound parameters of some nematics

Measurements of ultrasonic velocity and density of solutes in dilute solutions as a function of concentration and temperature can be used to obtain several thermodynamic and acoustical parameters and their excess adiabatic compressibility. The physical parameters that can be determined through these are: molar sound velocity or Raos number (R), molar compressibility or Wadas constant (B), characteristic acoustic impedance (Z), intermolecular or free length (L f), free volume (V f), available volume (V a) and adiabatic compressibility (β). These parameters play an important role in the phenomenon associated with intermolecular interaction and hence in sound transmission. For example, the parameter Z that is determined by the product of density (d) and ultrasonic velocity (c) has a greater significance as a characteristic property of the medium than does either the density or velocity individually so also in case of sound transmission the parameter of more concern is the molar sound volume (V m) rather than molar sound velocity or Rao’ number. Such studies on liquid crystals around phase transition temperature in their pure state yield important information and so also in their dilute solutions. In view of above facts, the ultrasonic velocity with density measurement studies on pure samples of nematics, namely, Butyl-p-(p-ethoxy phenoxy carbonyl)phenyl carbonate, p-(p-ethoxy phenyl azo)phenyl undecylenate and p-[N-(p-methoxy benzylidene)amino]phenyl benzoate in dilute solutions was taken up both as a function of mole fraction (in benzene) and temperature. The results of the above work is presented in this article and discussed.

Viscoelastic studies of some phenols from dielectric measurements

The variation of dielectric relaxation time with the viscosity of the medium is being exploited in drawing certain quantitative conclusions regarding molecular motion and intermolecular forces in liquids, liquid mixtures, dilute solutions and multi-component polar solutes in dilute solution. With no perfect empirical or theoretical equation in place for the variation of dielectric relaxation time with viscosity, the experimental investigations on different systems only can give an insight. In the present study the results of dielectric measurements carried out on pure samples of o-ethyl phenol, 2-n-butylphenol, 4-n-butylphenol, and 2,6-butylphenol in dilute solutions in different mixed solvents (benzene + paraffin) and on binary mixtures (1 : 1) of p-2-n-butylphenol + 4-n-butylphenol and p-bromonitrobenzene + 2,6-butylphenol, are reported. For comparison, the results on p-bromonitrobenzene + m-bromonitrobenzene as an example of mixture of non-associative liquids was also carried out and the results are presented. Different parameters determined using these dielectric measurements are also presented using different models and these studies indicate that the dielectric behavior at microwave frequencies favor the concept of dynamic viscosity and a single viscoelastic relaxation time for the system under study.

Determination of excited state electric dipole moment of a molecule from solvatochromic shift measurements—a new approach

Abstract A new approach to the determination of the electric dipole moment of a molecule in an excited electronic state from the method of solvent-shifts is indicated.

On the visco-elastic and dielectric behaviour of two alcohols and their binary mixture

Inter-molecular and intra-molecular interactions in liquids determine the physical properties of the systems. These interactions are understood through the measurement of these physical properties. These become especially important in the case of alcohols in view of the specific type of interactions involved. Study of the variation of dielectric relaxation time with the viscosity of the medium is relevant in drawing certain quantitative conclusions regarding molecular motion and the inter-molecular forces in liquids, liquid mixtures, dilute solutions and multi-component polar solutes in dilute solution. In the absence of a perfect empirical or theoretical equation for the variation of dielectric relaxation time with viscosity, the experimental investigations on different systems can only give an insight. In the present study, the results of dielectric measurements carried out on pure samples of methyl alcohol and propyl alcohol in dilute solutions in different mixed solvents (benzene + paraffin) and on binary mixture (1 : 1) of methyl alcohol + propyl alcohol are reported. Different parameters determined are presented and these studies indicate that the dielectric behaviour at microwave frequencies favour the concept of dynamic viscosity and a single visco-elastic relaxation time for the systems under study.

On the Viscoelastic and Dielectric Behavior of Some Organic Compounds and Their Binary Mixtures

The dependence of dielectric relaxation time on the viscosity of the medium is being extensively used to draw certain quantitative conclusions regarding molecular motion and inter-molecular forces in liquids, liquid mixtures, dilute solutions, and multi-component polar solutes in dilute solution. In the absence of proper empirical or theoretical equations for the variation of dielectric relaxation time with viscosity, only the experimental investigations on different systems can give an insight. In the present study, the results of dielectric measurements carried out on pure samples of bromohexane, bromooctane and bromodecane in dilute solutions in different mixed solvents (benzene + paraffin) and on binary mixtures (1 : 1) of (bromohexane + bromodecane); (bromodecane + propyl alcohol) and (propyl alcohol + methyl alcohol) are reported. For comparison, the results of bromodecane + propyl alcohol and propyl alcohol + methyl alcohol are chosen as they form examples of mixture of non-associative + associative and associative + associative liquids, respectively. Different parameters determined using these dielectric measurements are also presented using different models. These studies indicate that the dielectric behavior at microwave frequencies favor the concept of dynamic viscosity and a single viscoelastic relaxation time for the systems under study.

Temperature Dependence Studies on Dielectric Relaxation and Electric Dipole Moment of Poly (Ethylene Glycol)

Temperature dependant studies of dielectric relaxation time τ and electric dipole moment μ of poly (ethylene glycol) (PEG) with molecular weight 400 in dilute solution in benzene was carried out at 9.59 GHz at different temperatures using an X-band microwave bench. GopalaKrishnas single frequency and concentration variation method were adopted to determine τ and μ. Results are reported and discussed. On the basis of these parameters, the dielectric behavior of PEG-400 in a nonpolar solvent is discussed.