Showing papers by "Indian Institute of Science published in 1984"
TL;DR: In this article, a new method of modeling material behavior which accounts for the dynamic metallurgical processes occurring during hot deformation is presented, which considers the workpiece as a dissipator of power in the total processing system and evaluates the dissipated power co-contentJ = ∫o σ e ⋅dσ from the constitutive equation relating the strain rate (e) to the flow stress (σ).
Abstract: A new method of modeling material behavior which accounts for the dynamic metallurgical processes occurring during hot deformation is presented. The approach in this method is to consider the workpiece as a dissipator of power in the total processing system and to evaluate the dissipated power co-contentJ = ∫o σ e ⋅dσ from the constitutive equation relating the strain rate (e) to the flow stress (σ). The optimum processing conditions of temperature and strain rate are those corresponding to the maximum or peak inJ. It is shown thatJ is related to the strain-rate sensitivity (m) of the material and reaches a maximum value(J max) whenm = 1. The efficiency of the power dissipation(J/J max) through metallurgical processes is shown to be an index of the dynamic behavior of the material and is useful in obtaining a unique combination of temperature and strain rate for processing and also in delineating the regions of internal fracture. In this method of modeling, noa priori knowledge or evaluation of the atomistic mechanisms is required, and the method is effective even when more than one dissipation process occurs, which is particularly advantageous in the hot processing of commercial alloys having complex microstructures. This method has been applied to modeling of the behavior of Ti-6242 during hot forging. The behavior of α+ β andβ preform microstructures has been exam-ined, and the results show that the optimum condition for hot forging of these preforms is obtained at 927 °C (1200 K) and a strain rate of 1CT•3 s•1. Variations in the efficiency of dissipation with temperature and strain rate are correlated with the dynamic microstructural changes occurring in the material.
1,121 citations
TL;DR: In this paper, the authors investigated the relationship between organized convection over the Indian Ocean and sea surface temperature (SST) and reported that on a monthly basis the degree of cloudiness correlates well with SST for the relatively colder oceans, but when SST is maintained above 28 °C it ceases to be an important factor in determining the variability of cloudsiness.
Abstract: In monsoon regions, the seasonal migration of the intertropical convergence zone (ITCZ) is manifested as a seasonal reversal of winds. Most of the summer monsoon rainfall over India occurs owing to synoptic and large-scale convection associated with the continental ITCZ (Fig. 1). We have investigated the interaction between these large-scale convective systems and the ocean over which they are generated1â3, concentrating on the relationship between organized convection over the Indian Ocean and sea surface temperature (SST). We report here that on a monthly basis the degree of cloudiness correlates well with SST for the relatively colder oceans, but when SST is maintained above 28 °C it ceases to be an important factor in determining the variability of cloudiness. Over the major regions of convection east of 70°E, which are warm year after year, the observed cloudiness cannot be correlated with variations in SST.
406 citations
01 Jan 1984
TL;DR: Crystal structures of over three dozen Aib-containing peptides, ranging in length from 2 to 11 residues, have been reported so far which exemplify various types of beta-turns, consecutive beta- turns, and helical structures.
Abstract: The introduction of alpha-aminoisobutyric acid (Aib) into peptides dramatically limits the range of accessible backbone conformations. The presence of two geminal methyl groups at C alpha sterically compels Aib residues to largely favor structures in the right- or left-handed 3(10)/alpha-helical regions (phi approximately +/- 60 +/- 20 degrees, psi approximately +/- 30 +/- 20 degrees) of the peptide conformational map. Aib residues occur extensively in microbial peptides which form transmembrane channels. This observation has stimulated considerable interest in the stereochemistry of Aib peptides. This review summarizes theoretical studies on the conformations of Aib residues and examines the available data on solid-state structures, derived from single crystal X-ray diffraction studies. Crystal structures of over three dozen Aib-containing peptides, ranging in length from 2 to 11 residues, have been reported so far which exemplify various types of beta-turns, consecutive beta-turns, and helical structures. Examples of nonhydrogen bonded and cyclic structures are also described. The crystallographic results compare well with structural studies in solution, establishing that Aib peptides can provide rigid structural models for the development of spectroscopic methods of peptide conformational analysis.
302 citations
TL;DR: In this article, the crystal chemistry of the oxides of the general formula A 2 B O 4 with particular reference to the stability of the K 2 NiF 4 structure and the relations between the different structures exhibited by this family of oxides is discussed.
231 citations
TL;DR: In this paper, the tetragonal-T structure of K 2 NiF 4 was studied and the atomic displacements in these distorted phases were discussed and rationalized in terms of the chemistry of the various compounds.
174 citations
TL;DR: In this paper, direct precipitation of fine powders of lead zirconate titanate (PZT) in the complete range of solid solution under hydrothermal conditions, starting from lead oxide and titania/zirconia mixed gels, is investigated.
139 citations
TL;DR: In this paper, it is shown that the Euler-Bernoulli theory gives Euler Bernoulli solutions in that part of the beam where shear deformation is unimportant and a shear-deformation type of solution in the pari of a cantilever beam, with transition stress patterns between the two.
Abstract: It is well known that the Euler-Bernoulli theory of the bending of beams makes use of a contradicting assumption of zero shear strains and nonzero shear stresses. Sometimes, this type oJ assumption is also carried over to more refined shear deformation theories. This paper outlines a theory thai avoids this assumption. With the aid of the specific example of a tip loaded cantilever beam, it is shown that the present theory gives Euler Bernoulli solutions in that part of the beam where shear deformation is unimportant and a shear deformation type of solution in the pari of the beam where shear deformation is important, with transition stress patterns between the two. Numerical studies, with a shear modulus representative of sandwich beams, bring out the usefulness of the present theory for the analysis of such soft-cored beams.
117 citations
TL;DR: In this article, the invariance of the degree of global coherence of Gaussian Schell-model fields is established in full generality and new invariants associated with incoherent superpositions of such fields are found.
Abstract: Propagation characteristics of Gaussian Schell-model fields through first-order optical systems and in free space are analyzed by the method of generalized rays. This allows the development of a simple geometrical description of these processes. The invariance of the degree of global coherence is established in full generality. Asymptotic behavior under free propagation and the emergence of a far-zone universal structure are analyzed. New invariants associated with incoherent superpositions of such fields are found.
114 citations
TL;DR: Both NADH- and NADPH-cytochrome c reductase activities were not significantly changed during the six days of treatment and Oral administration of these two terpenoids did not affect any of the lung-microsomal parameters measured.
Abstract: 1. Metabolites isolated from the urine of rats after oral administration of geraniol (I) were: geranic acid (II), 3-hydroxy-citronellic acid (III), 8-hydroxy-geraniol (IV), 8-carboxy-geraniol (V) and Hildebrandt acid (VI).
2. Metabolites isolated from urine of rats after oral administration of linalool (VII) were 8-hydroxy-linalool (VIII) and 8-carboxy-linalool (IX).
3. After three days of feeding rats with either geraniol or linalool, liver-microsomal cytochrome P-450 was increased. Both NADH- and NADPH-cytochrome c reductase activities were not significantly changed during the six days of treatment.
4. Oral administration of these two terpenoids did not affect any of the lung-microsomal parameters measured.
97 citations
TL;DR: In this article, the authors investigated the metal-insulator transition in perovskite systems LaNi1-xMxO3 (M = Cr, Mn, Fe, and Co) by transport measurements over the temperature range 12-300 K.
89 citations
TL;DR: In this paper, a unified computer program for structural synthesis and analysis of simple jointed kinematic chains with a degree of freedom 0.5 is presented. And applications of this program are presented in the succeeding parts of this paper.
TL;DR: Mesures de diffraction RX, calorimetrie differentielle a balayage, RPE, susceptibilite magnetique and conductivite electrique, entre 10 and 300 K, sur des poudres et monocristaux La 2 NiO 4
TL;DR: In this article, the i.r. and Raman spectra of polycrystalline samples of pyridine-2-thione have been obtained and a complete assignment of all the observed peaks has been possible.
TL;DR: The reliability of the computer program for structural synthesis and analysis of simple-jointed kinematic chains developed in Part 1 has been established by applying it to several cases for cases for which solutions are either fully or partially available in the literature.
TL;DR: Proposition d'un schema d'impulsions modifie pour les experiences COSY qui reduit drastiquement le temps d'accumulation des donnees and rend ces experiences comme une des plus puissantes as discussed by the authors.
TL;DR: In this paper, single-phase LaNi1-xMnxO3 samples in the compositional range 0 0.05 to 0.50 K were used to investigate the ferromagnetic spin glass properties of LaNi 1-mnx oxide.
Abstract: Single-phase LaNi1-xMnxO3 samples in the compositional range 0 0.05, but any motional enthalpy appears to remain small ( Delta Hm approximately=0). The x=0.1 sample exhibits ferrimagnetic spin glass behaviour below 40K, and the ferromagnetic interactions increase with manganese concentration. The oxide with x=0.50 is ferromagnetic with a well defined Curie temperature.
TL;DR: In this paper, a complete collection of 97 10-link, three-freedom simple-jointed kinematic chains is presented, and the program shows that of these chains, 3 have total freedom, 70 have partial freedom and the remaining 24 have fractionated freedom.
TL;DR: Vanadate-stimulated NADH oxidation activity could be partially solubilized by treating erythrocyte membranes either with Triton X-100 or sodium cholate, and partially purified enzyme obtained by extraction with cholate and fractionation by ammonium sulphate and DEAE-Sephadex was found to be unstable.
Abstract: Oxidation of NADH by rat erythrocyte plasma membrane was stimulated by about 50-fold on addition of decavanadate, but not other forms of vanadate like orthovanadate, metavanadate aad vanadyl sulphate. The vanadate-stimulated activity was observed only in phosphate buffer while other buffers like Tris, acetate, borate and Hepes were ineffective. Oxygen was consumed during the oxidation of NADH and the products were found to be NAD+ and hydrogen peroxide. The reaction had a stoichiometry of one mole of oxygen consumption and one mole of H2O2 production for every mole of NADH that was oxidized.
TL;DR: Sulfate adsorption on kaolinite was followed at 0.7 ~teq/ml to 99/~eq/ml solution concentrations at 30"C and at pH 6.0, and the amount of OH- ions released and the change in surface charge were determined as mentioned in this paper.
Abstract: Sulfate adsorption on kaolinite was followed at 0.7 ~teq/ml to 99/~eq/ml solution concentrations at 30"C and at pH 6.0, and the amount of OH- ions released and the change in surface charge were determined. Sulfate was adsorbed at positive and neutral sites by displacing OH 2 and OH- groups, respectively. Adsorption of sulfate occurred predominantly at positive sites at low (0.7/~eq/ml to 0.9/~eq/ ml) solution concentrations, whereas at higher solution concentrations, the proportion of the sulfate adsorbed at the neutral sites increased, varying from 51% at 4.9 #eq/ml to 68% at 99 ~teq/ml. The form of sulfate bonding was apparently governed by the level of the positive charge on the clay surface. Higher positive charge at low and intermediate levels of sulfate saturation resulted in the adsorption of sulfate as a divalent anion by forming a 6-member ring with surface A1. With a decrease in positive charge at higher levels of adsorption, the sulfate ion formed both monodentate and bidentate complexes.
01 Jul 1984
TL;DR: In this paper, a new technique for reducing the torque pulsations in a conventional current source inverter fed induction motor drive is presented, which does not attempt to improve the current waveforms, but modifies the air gap MMF directly.
Abstract: A new technique for reducing the torque pulsations in a conventional current source inverter fed induction motor drive is presented. This does not attempt to improve the current waveforms, but modifies the airgap MMF directly. This is based on the use of a motor with two sets of balanced phase windings, with a 30 electrical degree phase difference between them, and each set being fed from a conventional current source inverter. The two inverters are further connected in series so that they can operate from the same current source. As a consequence of this arrangement, the voltage rating of the components of each inverter is reduced, along with reduced torque ripple. This scheme has been experimentally verified and compared with the performance of a conventional scheme.
TL;DR: The results suggest that the occurrence of stuttering might be related to the demands that speech makes on motor planning, particularly at the beginning of sentences, and might have significance for the speech breakdown views on stuttering.
Abstract: The purpose of this study was to analyze the influence of sentence length and clause position on stuttering in the complex sentences of two languages—English and Kannada. Ten monolingual adult stut...
TL;DR: In this paper, the authors describe the formation of structures longue distance entrainant une intercroissance recurrente coherente de deux unites distinctes chimiquement mais apparentees structuralement, possing un plan cristallographique identique.
TL;DR: In this article, the EPR spectra of BaTiO 3 ceramics, exhibiting the PTC effect, showed two signals at room temperature with g = 1.963 indicating activation of the corresponding defect centres, possibly V'Ba, causing diminution of charge carriers.
TL;DR: In this article, a simple three-state model permitting two different configurational states for the solvent, together with one for the organic adsorbate, is analyzed to derive the adsorption isotherm.
TL;DR: The results suggest that folded conformations may allow highly active interactions with the neutrophil formylpeptide receptor.
TL;DR: Using the link-link incidence matrix to represent a simple-jointed kinematic chain algebraic procedures have been developed to determine its structural characteristics such as the type of freedom of the chain, the number of distinct mechanisms and driving mechanisms that can be derived from the chain.
TL;DR: In this paper, the authors investigated the spectral properties of mixed-alkali diborate glasses and found that B-O stretching and bending frequencies exhibit nonlinear shifts which can be described as a mild mixedalkali effect.
TL;DR: In this paper, five cyclic peptide disulphides of the type Boc-Cys-Pro-X-cys-NHMe have been synthesized, where X = Gly (1), L-Ala (2), D-Aib (3), Aib (4) and L-Leu (5).
01 Apr 1984
TL;DR: There is much variation in the extent of communication and suckling from one allomother to another with a mother definitely preferring her own calf, with considerable reduction in the amount of time devoted to feeding.
Abstract: This study is based on 645 hr of observations on the social behaviour of tame elephants maintained at three wildlife sanctuaries of Bandipur, Mudumalai and Anaimalai in South India. These elephants are wild captured adults, and their calves born in captivity. The observations were carried out when the elephants are left free for grazing in their natural habitat, where they often intermingle with wild herds. The adult females always stay together when there are calves present: while the adult males graze by themselves. The calves position themselves between adult females and juveniles closer to their mother. All females rush together when a calf sounds alarm. The adult females stand guard over calves lying down for rest thereby accepting considerable reduction in the amount of time devoted to feeding. The ‘allomothers’ suckle other calves when they have no calf of their own, sometimes as much as the mother herself. The acts of social communication are largely initiated by the calf touching the breast or body of an adult female with its nostril. There is much variation in the extent of communication and suckling from one allomother to another with a mother definitely preferring her own calf.