Showing papers by "Indian Institute of Technology Bombay published in 1985"

Augmentation of Laminar Flow Heat Transfer in Tubes by Means of Wire Coil Inserts

Abstract: Etude experimentale de la chute de pression isotherme et du transfert de chaleur par convection vers une huile en ecoulement laminaire dans un tube lisse et sept tubes munis de bobines de fil metallique de differents diametres et placees de differentes manieres. Evaluation des performances de ces tubes a bobines

Model for Piping‐Plugging in Earthen Structures

Abstract: A capillary model was developed to predict under what conditions piping vs. plugging is likely to occur as a result of clay particle dispersion in soils. In the intermediate size range, i.e., particles too small per se to clog pore constrictions and too large to wash through unimpeded, the outcome depends strongly on the concentration of dispersed particles in the seepage stream. This concentration in turn depends upon the rate at which the particles are eroded from the pore walls. The capillary model was used to ascertain the relationship between key variables at the onset of piping. This relationship involved the initial permeability and porosity of the soil, the critical tractive stress, and the hydraulic gradient. The model was also used to predict under what circumstances clay particle concentrations in a seepage stream will buildup suddenly to very high values, a condition favorable to clogging or particle holdup. Results of the analysis showed that very large particle concentration buildups tend to occur at permeabilities of less than 10\u-\u9 cm² (10\u-\u4 cm/s for water at 20°C). This prediction is consistent with previous findings reported in the geotechnical literature.

Chemical and magnetic stratigraphy of parts of Narmada Region, Deccan Basalt Province

Abstract: Field investigations of a 666 m thick Deccan volcanic sequence north of the River Narmada (Khalghat-Mhow traverse; 60 km) showed the presence of 21 flows, while a 549 m thick southern section comprises of 28 flows (Mandaleswar-Pipaljopa traverse: 110 km). The lava sequences essentially consist of PI and/or Pyx phyric to aphyric basalts with glassy vesicular - amygdular tops/flow breccia. On the basis of selected major and trace elements (Si, K, Ti, P, Ba, Sr, Zr), the Khalghat section is divided into three formations. The lowermost Narmada Formation is characterized by lower K, Ba, Sr, Ba/Ti, Ba/Sr and Ba/Zr than the succeeding Manpur Formation . The uppermost Mhow Formation is highly depleted in K, Ba, Sr compared to the two lower formations. Chemically, a four-unit informal stratigraphy has been adopted for the Mandaleswar section. The lower three may be correlated with the Narmada, Manpur and Mhow Fms of the Khalghat section and the upper one is labelled the Satpura Formatio n. Each formation is defined as a set of flows characterized by one or more chemical types such as 'primitive' and' evolved' ones. The palaeomagnetic results of the Khalghat section demonstrate that the lower 254m pile of flows belongs to normal polarity (N) (' Narmada Normal Epoch ') overlain by 412 m thick flows with reversed polarity (R) ('Malwa Reversed Epoch'). Interestingly, on the southern side of the river, about 21 m thick N flows are overlain by 476 m R flows, which in turn are capped by 52m thick N flows (' Satpura Normal Epoch ') resulting in an unambiguous NRN sequence in the Deccan basalt province. It appears that the northern side of the Narmada River has been thrown up relative to the southern side. Based on the correlation of the magnetic reversals in the Deccan as well as marine magnetic anomalies, it seems likely that the normally magnetized older Rajmahal traps (about 100 MA) of eastern India form the base of the Deccan basalts.

Design and analysis of parallel Monte Carlo algorithms

Abstract: This paper demonstrates that the potential of intrinsic parallelism in Monte Carlo methods, which has remained essentially untapped so far, can be exploited to implement these methods efficiently on SIMD and MIMD computers. Two basic static and dynamic computation assignment schemes are proposed for assigning the primary estimate computations (PECs) to processors in a parallel computer. These schemes can be used to design parallel Monte Carlo algorithms for many applications. The time complexity analyses of static computation assignment (SCA) schemes are carried out using some results from order statistics, whereas those of dynamic computation assignment (DCA) schemes are carried out using results from order statistics, renewal and queueing theories. It is shown that for smaller number of processors, linear speedup can be achieved with the SCA schemes and the speedup almost equal to the number of processors can be achieved with the DCA schemes. Some computational results for Monte Carlo solutions of Lapla...

A new general Routh-like algorithm to determine the number of RHP roots of a real or complex polynomial

Abstract: A new Routh-like algorithm for determining the number of right-half plane (RHP) roots of a polynomial with real or complex coefficients is given. It includes the Routh algorithm for real polynomials as a special case. Moreover, the algorithm also applies directly to the singular case wherein the leading coefficient of a row, but not the entire row, vanishes, needing far fewer computations than the heuristic epsilon - method about which there was a vigorous discussion in these TRANSACTIONS a few years ago, and further not requiring investigation of an auxiliary polynomial. The algorithm is illustrated by a few examples. The proof of the algorithm is based on the Principle of the Argument, and thus also constitutes a simple proof of the Routh algorithm in the regular case.

Neutron and proton densities in nuclei

Abstract: A simple expression for nuclear densities which incorporates the correct asymptotic and central behaviour, gives quite accurate values for rms radii and surface thicknesses. It also brings out some important nuclear properties, (i) global constancy of neutron densities, (ii) equality of half-density radiiR for neutrons and protons, (iii) near constancy ofRN−1/3, (iv) larger surface thickness and rms radius for neutrons (v) shell effects on charge density.

Solubility characteristics of R22-DMF refrigerant-absorbent combination

Abstract: This Paper presents the solubility data of Refrigerant 22 (R22) - dimethyl formamide (DMF) measured over a wide range of temperature (−25°C to 120°C) and over a complete range of composition. The mixtures show large negative deviation from Raoult's law and there is large difference in normal boiling point its components. Thus this combination is suited for vapour absorption refrigerant systems. The In P-1/T diagram and temperature-composition diagram for the mixtures of R22-DMF have also been plotted for use in the analysis of vapour absorption systems.

Structural and Electrical Properties of the LaCo1−xMnxO3 and LaCo1−xFexO3 Systems

Abstract: Structure and electrical properties of two perovskite systems LaCo1−xMnxO3 and LaCo1−xFexO3 (0 ≦ x ≦ 1) are described. A phenomenological phase diagram based on the relation between cation radii rA, rB and the void radius at the A-site is proposed that rationalises most of the existing structural data. Results on measurements of electrical resistivity and Seebeck coefficient are discussed. Struktur und elektrische Eigenschaften der beiden Perovskite-Systeme LaCo1−xMnxO3 und LaCo1−xFexO3 (0 ≦ x ≦ 1) werden beschrieben. Ein phanomenologisches Phasendiagramm, das auf einer Beziehung zwischen den Kationenradien rA, rB und dem Hohlraumradius an den A- Platzen beruht, wird vorgeschlagen und fast die meisten der existierenden Strukturdaten zu- sammen. Mesergebnisse der elektrischen Leitfahigkeit und des Seebeckkoeffizienten werden diskutiert.

Rapid spectrophotometric determination of thorium(IV) with 1-(2′-thiazolylazo)-2-naphthol

Abstract: Thorium(IV) reacts with 1-(2′-thiazolylazo)-2-naphthol (TAN) in the presence of antipyrine to form a sparingly soluble red-coloured chelate, soluble in ≥36% methanol (v/v). Complexation takes place instantaneously at pH 2.4–2.8, maintained by glycine buffer. Antipyrine is found to enhance sensitivity of the complex, which is stable for 19 hours. The 1∶2 complex exhibits maximum absorbance at 555 nm, obyes Beer's law in the concentration range from 0.32 to 6.56 μg of thorium(IV) per ml, has a molar absorptivity of 3.14·104 dm3/mol−1·cm−1 and a Sandel sensitivity of 7.4 ng·cm−2. The formation constant (log K) is found to be 8.62 and 8.45. Interference of 57 anions and cations in the determination of thorium(IV) has been studied. From ten repeated determinations, the coefficient of variation was found to be ±0.98%. The method was successfully applied for determination of thorium content in a sample of monazite.

Heat transfer from rectangular plates inclined at different angles of attack and yaw to an air stream

Abstract: Average heat transfer coefficients during forced convection air flow over inclined and yawed rectangular plates have been experimentally determined. Tripping wires at the edges ensured that a turbulent boundary layer prevailed over the plates. The experiments were carried out for a constant surface temperature and covered two plates of different aspect ratios, angles of attack from 0 to 45 deg, angles of yaw from 0 to 30 deg, and Reynolds numbers from 2 times; 104 to 3.5 times; 105 . The results show that the average heat transfer coefficient is essentially insensitive to the aspect ratio and angle of yaw. However, it is a function of Reynolds number and the angle of attack. Correlation equations for various angles of attack are suggested.

Stress distribution in a two-dimensional infinite anisotropic medium with collinear cracks

Abstract: The plane problem of an anisotropic material with cracks, whose surfaces are subject to surface tractions of a general kind, is studied. The medium considered if of infinite extent and the cracks are located on a single line. The Fourier transform method is employed to derive the stress and displacement components at an arbitrary point of the medium in terms of the dislocation densities and the stress discontinuities on the crack line. These formulae for stress and displacement components involve the roots of a quartic equation whose coefficients are the material constants. The cases of different roots and pairwise coincident roots are examined separately. An orthotropic medium is an important example for the case of different roots while an isotropic medium is that for the case of pairwise coincident roots. These examples are discussed in detail. As an illustration of the use of these formulae the problem of a single crack in an infinite anisotropic medium is examined in detail.

Physical boson basis states in the boson expansion theories.

Abstract: The use of physical boson basis states is stressed for the calculations in the boson space The explicit form of physical boson basis states in terms of bosons is derived for the nonunitary boson mapping of Dyson The ambiguity in the normalization introduced due to the use of bi-orthonormal basis states is satisfactorily resolved, resulting in a Hermitian matrix This Hermitian matrix is found to coincide with the Hamiltonian matrix in the fermion space The model cases where the use of a boson basis is justified are shown to be consistent with our view of using physical boson basis states

A model on the breakdown of crude oil gel

Abstract: A new model is proposed on the basis of the simultaneous decrease of build-up yield stress and viscosity to describe the break down of crude oil gel. A set of two experiments conducted at different but under constant wall shear stress is required to compute the four parameters of the model. The model is verified with reported data. On propose un nouveau modele pour decrire la rupture d'un gel de petrole brut base sur la diminution simultanee de la limite de contrainte et de la viscosite. II faut faire une serie de deux experiences pour des contraintes de cisallement a la paroi differentes mais constantes. pour calculer les quatre parametres du mod%eGle. On a verifie le modele en employant les resultats de la litterature.

Studies in the synthesis of diisocyanates and polyimides therefrom

Abstract: Syntheses du diisocyanato-4,4' azobenzene et du dichloro-3,3' diisocyanato-4,4' diphenylmethane; synthese des polyimides et leur caracterisation

Cation-exchange chromatographic-separation of lead from mixed-solvents

Abstract: The cation exchange separation of lead from associated elements on Dowex 50W-X8, was carried out in mixed solvent systems. Elution behaviour was studied with 0.75 M HCl in the presence of various concentrations of solvents such as methanol, ethanol, 2-propanol, acetone, 1, 4 dioxane and tetrahydrofuran. Tetrahydrofuran, 1, 4 dioxane and acetone were effective in the presence of hydrochloric acid. At low concentrations of methanol, ethanol and 2-propanol in hydrochloric acid were useful for the separation of ions from lead. Lead was separated from binary and as well as multicomponent mixtures. The method was extended to the separation of lead from lead base alloys.