Showing papers by "Jadavpur University published in 1992"

A new algorithm for the reconfiguration of distribution feeders for loss minimization

Abstract: The authors report a power-flow-minimum heuristic algorithm for determining the minimum loss configuration of radial distribution networks. The algorithm is based on the concept of optimum flow pattern which is determined by solving the KVL and KCL (Kirchoff's voltage and current laws) equations of the network. The optimum flow pattern of a single loop formed by closing a normally open switch is found, and the flow pattern is established in the radial network by opening a closed switch. This process is repeated until the minimum loss configuration is obtained. A simple, fast and approximate power flow method has also been developed to assist the reconfiguration algorithm. The proposed reconfiguration algorithm has been found to give better network configuration than those obtained by some other methods. >

Non-ideal mixing in the phlogopite-annite binary: constraints from experimental data on Mg−Fe partitioning and a reformulation of the biotite-garnet geothermometer

Abstract: The existing experimental data [Ferry and Spear 1978; Perchuk and Lavrent'eva 1983] on Mg−Fe partitioning between garnet and biotite are disparate. The underlying assumption of ideal Mg−Fe exchange between the minerals has been examined on the basis of recently available thermochemical data. Using the updated mixing parameters for the pyrope-almandine asymmetric regular solution as inputs [Ganguly and Saxena 1984; Hackler and Wood 1984], thermodynamic analysis points to non-ideal mixing in the phlogopite-annite binary in the temperature range of 550°C–950°C. The non-ideality can be approximated by a temperature-independent, one constant Margules parameter. The retrieved values for enthalpy of mixing for Mg−Fe biotites and the standard state enthalpy and entropy changes of the exchange reaction were combined with existing thermochemical data on grossular-pyrope and grossular-almandine binaries to obtain geothermometric expressions for Mg−Fe fractionation between biotite and garnet. [T in K] $$\begin{gathered} {\text{T(HW) = [20286 + 0}}{\text{.0193P - \{ 2080(X}}_{{\text{Mg}}}^{{\text{Gt}}} {\text{)}}^{\text{2}} {\text{ - 6350(X}}_{{\text{Fe}}}^{{\text{Gt}}} {\text{)}}^{\text{2}} \hfill \\ {\text{ - 13807(X}}_{{\text{Ca}}}^{{\text{Gt}}} {\text{)(1 - X}}_{{\text{Mn}}}^{{\text{Gt}}} {\text{) + 8540(X}}_{{\text{Fe}}}^{{\text{Gt}}} {\text{)(X}}_{{\text{Mg}}}^{{\text{Gt}}} {\text{)(1 - X}}_{{\text{Mn}}}^{{\text{Gt}}} {\text{)}} \hfill \\ {\text{ + 4215(X}}_{{\text{Ca}}}^{{\text{Gt}}} {\text{)(X}}_{{\text{Mg}}}^{{\text{Gt}}} {\text{ - X}}_{{\text{Fe}}}^{{\text{Gt}}} {\text{)\} + 4441}}{{{\text{(2X}}_{{\text{Mg}}}^{{\text{Bt}}} {\text{ - 1)]}}} \mathord{\left/ {\vphantom {{{\text{(2X}}_{{\text{Mg}}}^{{\text{Bt}}} {\text{ - 1)]}}} {{\text{[13}}{\text{.138}}}}} \right. \kern- ulldelimiterspace} {{\text{[13}}{\text{.138}}}} \hfill \\ {\text{ + 8}}{\text{.3143 InK}}_{\text{D}} {\text{ + 6}}{\text{.276(X}}_{{\text{Ca}}}^{{\text{Gt}}} ){\text{(1 - X}}_{{\text{Mn}}}^{{\text{Gt}}} )] \hfill \\ {\text{T(GS) = [13538 + 0}}{\text{.0193P - \{ 837(X}}_{{\text{Mg}}}^{{\text{Gt}}} )^{\text{2}} {\text{ - 10460(X}}_{{\text{Fe}}}^{{\text{Gt}}} )^2 \hfill \\ {\text{ - 13807(X}}_{{\text{Ca}}}^{{\text{Gt}}} )(1{\text{ - X}}_{{\text{Mn}}}^{{\text{Gt}}} {\text{) + 19246(X}}_{{\text{Fe}}}^{{\text{Gt}}} ){\text{(X}}_{{\text{Mg}}}^{{\text{Gt}}} ){\text{(1 - X}}_{{\text{Mn}}}^{{\text{Gt}}} ) \hfill \\ {\text{ }}{{{\text{ + 5649(X}}_{{\text{Ca}}}^{{\text{Gt}}} ){\text{(X}}_{{\text{Mg}}}^{{\text{Gt}}} {\text{ - X}}_{{\text{Fe}}}^{{\text{Gt}}} ){\text{\} + 7972(2X}}_{{\text{Mg}}}^{{\text{Bt}}} {\text{ - 1)]}}} \mathord{\left/ {\vphantom {{{\text{ + 5649(X}}_{{\text{Ca}}}^{{\text{Gt}}} ){\text{(X}}_{{\text{Mg}}}^{{\text{Gt}}} {\text{ - X}}_{{\text{Fe}}}^{{\text{Gt}}} ){\text{\} + 7972(2X}}_{{\text{Mg}}}^{{\text{Bt}}} {\text{ - 1)]}}} {{\text{[6}}{\text{.778}}}}} \right. \kern- ulldelimiterspace} {{\text{[6}}{\text{.778}}}} \hfill \\ {\text{ + 8}}{\text{.3143InK}}_{\text{D}} {\text{ + 6}}{\text{.276(X}}_{{\text{Ca}}}^{{\text{Gt}}} )(1{\text{ - X}}_{{\text{Mn}}}^{{\text{Gt}}} )] \hfill \\ \end{gathered} $$ The reformulated geothermometer is an improvement over existing biotite-garnet geothermometers because it reconciles the experimental data sets on Fe−Mg partitioning between the two phases and is based on updated activity-composition relationship in Fe−Mg−Ca garnet solid solutions.

An Economic Order Quantity Model for Items with Two Levels of Storage for a Linear Trend in Demand

Abstract: A deterministic inventory model with two levels of storage (own warehouse and rented warehouse) is studied by considering a linear (positive) trend in demand. Firstly, the model is formulated and solved without allowing backlogging. Secondly, the model is reformulated and solved under the assumptions that shortages in inventory are allowed and backlogged. The results are illustrated with the help of numerical examples.

Environments and processes of manganese deposition

Abstract: Concentration of manganese in solution and its deposition takes place by redox-controlled processes in a variety of modern and ancient geologic and geochemical environments. Modern Mn deposition occurs predominantly in deep-sea areas rather than shallow-water domains. Although deep-sea sedimentary deposits dominate, hydrothermal contribution of Mn to the ocean system may be substantial. Mn deposition from hydrothermal solutions at or near sea-floor-spreading centers and less commonly in island-arc areas is known. In addition, near- and far-field dispersion of Mn from vent sites is also substantial. Such distributions are controlled by the flow rate and egress temperature of the solution and the residence time of Mn in seawater. Thus, even in sedimentary deposit domains, at least partial derivation of Mn from a hydrothermal source is possible. Sedimentary Fe-Mn crusts on older volcanic substrates on seamounts form by hydrogenous deposition of metal concentrated from terrigenous sources in the mid-water column, oxygen-minimum zones. Thus, the presence or absence of volcanic rocks is not a clear indication of whether sedimentary Mn deposits, particularly in the ancient geologic record, are the result of a totally terrigenous or a totally volcanogenic source. Abyssal Fe-Mn nodules are considered to form from a basin water (hydrogenous) and/or pore water (early diagenetic) supply of metals, but in most cases the extent of supply from either of the sources is unknown. The metal incorporation mechanisms of free-moving nodules is little understood and it is possible that in most cases both sources contribute to the nodule composition. Therefore, no nodule should be considered as totally hydrogenous or totally early diagenetic based only on its bulk composition. The determined growth rate giving only an average value cannot by itself reveal the growth history of the nodules. Biological participation, directly or indirectly, controls Mn deposition. The stratified Black Sea demonstrates the concentration of Mn in solution in an anoxic zone, its advection toward the redox interface, and its precipitation in an oxygenated condition. Similar stratified basins are contemplated for ancient Mn deposition in shallow-water basin-margin areas. Geologic and geochemical signatures indicate that during sea-level highstands, stratified basins formed in which Mn was concentrated in solution in the anoxic part. Corresponding transgression led to the impingement of the redox interface on the continental shelf, and precipitation of Mn oxides could take place across the interface during transgression-regression cycles. Offshore, in anoxic or dysaerobic conditions,Mn carbonate could form by early diagenetic reaction of Mn (super +2) with CO 2 or HCO 3 (super -) produced by organic carbon oxidation. Critical Mn deposits occurring in transgressive, glaciogenic, and black shale-bearing ancient sequences support this paleoenvironmental model for Mn deposition.

Effects of plant extract Centella asiatica (Linn.) on cold restraint stress ulcer in rats.

Abstract: Extract of C. asiatica (Linn.) inhibited significantly gastric ulceration induced by cold and restraint stress (CRS) in Charles-Foster rats, Antiulcer activity of plant extract was compared with famotidine (H2-antagonist) and sodium valproate (anti-epileptic). Plant extract, formotidine and sodium valproate showed a dose dependent reduction of gastric ulceration. Plant extract increased brain GABA level which was also dose dependent. Pretreatment with bicuculline methiodide (specific GABAA-antagonist) at the dose level of 0.5 mg/kg im, reversed the antiulcerogenic activity of both plant extract and sodium valproate. Bicuculline as such did not induce gastric ulceration in normal rat.

Dehydration melting, fluid buffering and decompressional P–T path in a granulite complex from the Eastern Ghats, India

Abstract: A suite of metapelites, charnockites, calc-silicate rocks, quartzo-feldspathic gneisses and mafic granulites is exposed at Garbham, a part of the Eastern Ghats granulite belt of India. Reaction textures and mineral compositional data have been used to determine the P–T–X evolutionary history of the granulites. In metapelites and charnockites, dehydration melting reactions involving biotite produced quartzofeldspathic segregations during peak metamorphism. However, migration of melt from the site of generation was limited. Subsequent to peak metamorphism at c. 860° C and 8 kbar, the complex evolved through nearly isothermal decompression to 530-650° C and 4-5 kbar. During this phase, coronal garnet grew in the calc-silicates, while garnet in the presence of quartz broke down in charnockite and mafic granulite. Fluid activities during metamorphism were internally buffered in different lithologies in the presence of a melt phase. The P–T path of the granulites at Garbham contrasts sharply with the other parts of the Eastern Ghats granulite belt where the rocks show dominantly near-isobaric cooling subsequent to peak metamorphism.

International Trade and Endogenous Production Structures

Abstract: No single production structure has become dominant in models of the pure theory of international trade, even those characterized by perfect competition. Most models are represented by Ricardian, Heckscher-Ohlin, or Specific-Factors structures, or variants and combinations of these, with the selection often dictated by the problem being investigated. However, it is well known that if a country is freed from the bonds of autarky and allowed to engage in trade in goods or factors, a certain degree of specialization is encouraged so that the production structure with trade can differ significantly from that postulated in autarky. In that sense production structures are endogenously affected by trade.

A Note on a Replenishment Policy for an Inventory Model with Linear Trend in Demand and Shortages

Abstract: The present paper deals with an alternative approach for finding the optimal number of replenishments and optimal replenishment times for a finite-horizon inventory problem with linearly increasing demand allowing shortages which are fully backlogged. The method is developed by assuming that successive replenishment cycle lengths are in arithmetic progression. The corresponding results in the absence of shortage are also derived and finally some numerical examples are presented and compared with the existing methods to test the accuracy and effectiveness of the method. A sensitivity analysis has also been presented to study the effect of changes in the system parameters on the optimal cost.

On the effective electron mass in strained layer superlattices of non-parabolic semiconductors under strong magnetic quantization

Abstract: An attempt is made to study the effective electron mass in strained layer superlattices of non-parabolic semiconductors with graded structures under sirong magnetic quantization and to compare the same with the bulk specimens of the constituent materials, by formulating the appropriate magneto-dispersion laws. It is found, taking InAs/GaSb superlattice as an example, that the effective electron mass oscillates with the inverse quantizing magnetic field due to the Shubnikov-de Hass effect. The dependence of the effective mass on the magnetic quantum number in addition to Fermi energy is an intrinsic property of such semiconductor heterostructures. The stress makes the mass quantum number dependent in bulk specimens and even in the presence of broadening, the effective masses in superlattices exhibit significant oscillations with enhanced numerical values from that of the constituent semiconductors. Besides the effective electron masses also increase in an oscillatory way with increasing electron c...

An improved technique for the determination of solar cell parameters

Abstract: An improved method based on a computer-aided curve fitting technique for the simultaneous determination of the different solar cell parameters (Rs, Rsh, A, I0 and Iph) from single illuminated I-V characteristics has been developed The technique is very fast and precise It gives realistic values of the parameters for solar cells of various qualities and at different levels of illumination The validity of the method has been checked by comparing it with the values of some of the parameters measured directly by other methods

Ripple/dune to upper stage plane bed transition: Some observations from the ancient record

Abstract: In two Proterozoic sandstones, of the Indian shield cross-stratification and cross-lamination are observed to grade continuously into parallel-laminations often bearing parting lineations. These are interpreted as having resulted from a gradual transition from ripple/dune to upper stage plane bed structures. During the transition the inclination of the cross-strata diminishes and their shape changes from concave-up to sigmoidal. The sigmoidal cross-strata are characterized by well defined topsets, foresets and toesets and the topsets bear parting lineations. In the course of the transition sigmoidal cross-strata may give way either to horizontal parallel-lamination or inclined parallel-lamination. In the former the toesets of the successive sigmoidal cross-strata thicken and the thickness of the cross-strata beyond the brink point (the junction between the topset and foreset) tends to become uniform until a plane-bed state is reached and horizontal parallel-laminations are formed. In the latter the topset of the successive sigmoidal cross-strata increases in length at the expense of the foreset and toeset until the brink point ceases to exist so that only the topset laminations prevail and appear as inclined parallel-laminations. These transitions presumably result from a gradual increase in flow intensity beyond the stability limits of ripples/dunes. The progressive morphological changes of the cross-stratification over the transition are attributed to changing fallout patterns on the lee face of the bedforms in response to increasing flow intensity. Preservation of the records of such transitions suggests an abundant supply of sand grade sediments from suspension during the transition, shaping the sediment concentration profile over the bedforms and facilitating turbulence suppression. The variation in the pattern of transition from sigmoidal cross-stratification to parallel-lamination may be the result of different rates of sediment feed from the prevailing suspended sediment load in the two instances.

Kinetics of photoinduced electron transfer in a photoelectrochemical cell consisting of thiazine dyes and Triton X-100 surfactant

Abstract: Systems consisting of thiazine dyes in an aqueous solution of Triton X-100 generate photovoltage when studied in a photoelectrochemical cell arrangement. The growth and decay of the photovoltage follow functional forms related to the relaxation times. The rate constants of the forward light reaction and backward dark reaction have been calculated using the relaxation times. A possible mechanism of photovoltage generation involves the photoinduced electron transfer from Triton X-100 surfactant to the thiazine dye through a charge transfer (CT) interaction. A good correlation between the photovoltage, determined by photoelectrochemical studies, and the equilibrium constant, determined by kinetic and spectral studies, confirms this mechanism.

Indomethacin-loaded microspheres : design and preparation by a multiple-emulsification technique and their in vitro evaluation

Abstract: A new oral controlled-release drug delivery system was developed with two polymers using a multiple-emulsification technique. Powdered drug was dispersed in methyl cellulose sol, which was emulsified in ethyl cellulose solution in ethyl acetate. The primary emulsion thus formed was reemulsified in aqueous medium. During this phase, discrete microspheres were formed under optimized conditions. The size distribution of the microspheres was investigated, and scanning electron microscopy revealed the surface topography of the microspheres. The in vitro drug release followed first-order diffusion-controlled dissolution. More than 85% of the drug was released over 6 hr at pH 6.2 for all dissolution batches.

Depositional models for manganese oxide and carbonate deposits of the Precambrian Sausar Group, India

Abstract: Manganese ores occur conformably enclosed in the pelitic Mansar Formation and the calcareous Lohangi Formation of the Proterozoic Sausar Group in central India. Manganese oxides with variable silicate admixtures constitute the predominant ores. Further, manganese carbonate-oxide deposits, with or without silicates, occur as isolated lenses in the oxide deposits. Lithologic characteristics indicate that the Sausar Group sediments were deposited in a stable shelf environment. From the mineral-chemical attributes of the manganese deposits, we propose that the oxide ores were formed when anoxic bottom water enriched in Mn (super +2) was welled up on the continental margin and mixed with oxygenated surface water. Manganese carbonates were diagenetically derived from oxides by reaction with calcareous partings in isolated pools under evaporative conditions. Manganese silicate admixtures were produced as a consequence of influx of detritus during sedimentation.

Influence of surface texturization on the light trapping and spectral response of silicon solar cells

Abstract: A quantitative model that explains the spectral response, internal quantum efficiency, total short-circuit current, open-circuit voltage, and efficiency of high-efficiency solar cells with textured front surface and Lambertian back-surface reflectors is presented. A comparison of the textured cell characteristics is made with those of planar cells, and the separate roles of the front surface reflection coefficient and internal quantum efficiency in enhancing the short-circuit current have been investigated. It is shown that, in the case of large diffusion lengths, almost all the contribution to the increase of spectral response on texturization is due to the reduced reflection coefficient whereas, for small diffusion lengths, there is a significant increase in internal quantum efficiency on texturization, especially in the region of higher wavelengths. However, there is a small decrease in open-circuit voltage for large diffusion lengths, whereas no significant change is observed for small diffusion lengths on texturization. Nevertheless, there is a net gain in power conversion efficiency which is larger for smaller diffusion lengths. >

Pharmacological studies of the antiinflammatory profile of Mikania cordata (Burm) B. L. Robinson root extract in rodents

Abstract: The methanolic fraction of the root extract of Mikania cordata was found to possess an inhibitory effect on carrageenin and other mediator—induced oedema; there was a significant inhibition of protein exudation, an increase in peritoneal capillary permeability and leucocyte migration in inflammatory conditions. The extract significantly inhibited both cotton pellet and carrageenin—induced granuloma formation, was effective in experimentally induced arthritic conditions and turpentine—induced joint oedema. The extract also possessed inhibitory effects on sodium urate-induced experimental gout. A significant reduction of pyrexia was also found to occur when rats were treated with the extract. Thus it may be concluded that the methanolic fraction of M. cordata root extract possessed significant antiinflammatory effects in exudative, proliferative and chronic phases of inflammation and demonstrated an antipyretic activity.

Relationship of hypolipidemic and antineoplastic activities of tricyclohexyl- and triphenylphosphine boranes, carboxyboranes, cyanoboranes, and related derivatives.

Abstract: A series of tricyclohexyl- and triphenylphosphine boranes, carboxyboranes and cyanoboranes were synthesized These compounds have potent hypolipidemic effects, antineoplastic and antiinflammatory activities in rodents Furthermore, they demonstrated potent cyctotoxicity against standard human tissue culture lines The compounds which afforded the best hypolipidemic activity, ie greater than 40% reduction of serum cholesterol and triglyceride levels, were diphenyl-(4-methylphenyl)-phosphine borane and triphenylphosphine carboxyborane Other derivatives demonstrated more potent antineoplastic activity against the Ehrlich ascites carcinoma growth including triphenylphosphine cyanoborane, 2-amino-4-methyl-pyridine cyanoborane and 2-amino-pyridine cyanoborane Most of the derivatives showed good activity against murine L1210 lymphoid leukemia, Tmolt3 human leukemia, uterine HeLaS cells, and human glioma cell growth Select compounds were active against colon adenocarcinoma, KB nasopharynx, lung bronchogenic and osteosarcoma cell growth Tricyclohexyl- and triphenylphosphine boranes and the carboxy derivatives of the latter borane demonstrated good antiinflammatory activity Beziehungen zwischen lipidsenkenden Eigenschaften und antineoplastischer Aktivitat von Tricyclohexyl- und Triphenylphosphin-boranen, Carboxyboranen, Cyanoboranen und verwandten Verbindungen Tricyclohexyl- und Triphenylphosphinborane, Carboxyborane und Cyanoborane wurden hergestellt Diese Verbindungen sind bei Nagetieren wirksame Lipidsenker mit antineoplastischen und entzundungshemmenden Eigenschaften, die zugleich gegen die ublichen menschlichen Zellkulturen, die als Standards eingesetzt wurden, cytotoxisch wirken Die Verbindungen mit den besten Lipidsenker-Eigenschaften — Senkung des Serumcholesterols und der Triglyceride um mehr als 40% — waren Diphenyl-(4-methylphenyl)-phosphinboran und Triphenylphosphin-carboxyboran Starkere antineoplastische Wirkung gegen Ehrlich-Ascites Carcinom zeigten ua Triphenylphosphin-cyanoboran, 2-Amino-4-methylpyridin-cyanoboran und 2-Aminopyridin-cyanoboran Die meisten Derivate waren gut wirksam gegen L1210-lymphoide Leukamie der Maus, uterine HeLaS-Zellen und menschliche Gliomazellen Ausgewahlte Verbindungen unterdrucken das Zellwachstum des Colon-Adenocarcinoms, des KB Nasopharynx und des Osleosarcoms Tricyclohexyl- und Triphenylphosphinborane und Carboxyderivate der letztgenannten Verbindungen waren gute Entzundungshemmer

Flavour Democracy Calls for the Fourth Generation

Abstract: It is argued with the help of an illustrative model, that the inter--species hierarchy among the fermion masses and the quark mixing angles can be accommodated naturally in the standard model with (approximate) flavor democracy provided there are four families of sequential quark--leptons with all members of the fourth family having roughly equal masses. The special problem of light neutrino masses (if any) and possible solutions are also discussed.

A simple analysis of the electronic contribution to the elastic constants in stressed Kane type semiconductors

Abstract: In this paper an attempt is made to study the electronic contribution to the second and third order elastic constants in stressed Kane type semiconductors by formulating the respective expressions. It is found, for stressed n-InSb, that they increase with increasing carrier concentration in different manners, since the variations are totally band structure dependent and the stress enhances the numerical values of the elastic constants. We have also suggested an experimental method of determining the above contributions for degenerate materials having arbitrary dispersion laws. In addition, the well-known results for non-degenerate parabolic semiconductors have been obtained from the generalized expressions under certain limiting conditions.

Self-similarity in particle production in hadron-nucleus interactions at 350 and 200 GeV/ c

Abstract: Self-similarity in multiparticle production in {pi}{sup {minus}}-nucleus interactions at 350 and at 200 GeV/{ital c} has been studied in terms of factorial moments {ital F}{sub {ital q}} as well as fractal moments {ital G}{sub {ital q}}. Fractal parameters, already developed in the classical chaotic system, have been discussed and those parameters for multiparticle production in {pi}{sup {minus}}-nucleus interactions have been evaluated. While the {ital F}-moment analysis confirms nonstatistical fluctuations, and in terms of anomalous dimensions, predicts cascading in hadronization, multifractality is indicated through the {ital G}-moment analysis. Variation in the nature or values of fractal parameters have been studied in different sizes of phase space and in different energies for the same reactants. Such a phenomenological analysis is essential at the present stage of development in the study of fractality in multiparticle production.