Enhanced Instability of de Sitter Space in Einstein-Gauss-Bonnet Gravity

We show that the addition of a topological Gauss-Bonnet term to the gravitational action can greatly increase the instability of four-dimensional de Sitter space, by favoring the nucleation of black holes. The pair-production rate given by the Euclidean action for the instanton takes the form exp(Delta S) where S is the entropy in Einstein-Gauss-Bonnet theory. The coefficient of the Gauss-Bonnet term in the action sets a stability bound on the curvature of empty de Sitter space. For that coefficient in the low-energy effective action of heterotic string theory, the maximal curvature of de Sitter space is in general much lower than the Planck scale.Comment: 8 page

Fuzzy clustering of univariate and multivariate time series by genetic multiobjective optimization

Given a set of time series, it is of interest to discover subsets that share similar properties. For instance, this may be useful for identifying and estimating a single model that may fit conveniently several time series, instead of performing the usual identification and estimation steps for each one. On the other hand time series in the same cluster are related with respect to the measures assumed for cluster analysis and are suitable for building multivariate time series models. Though many approaches to clustering time series exist, in this view the most effective method seems to have to rely on choosing some features relevant for the problem at hand and seeking for clusters according to their measurements, for instance the autoregressive coe±cients, spectral measures or the eigenvectors of the covariance matrix. Some new indexes based on goodnessof-fit criteria will be proposed in this paper for fuzzy clustering of multivariate time series. A general purpose fuzzy clustering algorithm may be used to estimate the proper cluster structure according to some internal criteria of cluster validity. Such indexes are known to measure actually definite often conflicting cluster properties, compactness or connectedness, for instance, or distribution, orientation, size and shape. It is argued that the multiobjective optimization supported by genetic algorithms is a most effective choice in such a di±cult context. In this paper we use the Xie-Beni index and the C-means functional as objective functions to evaluate the cluster validity in a multiobjective optimization framework. The concept of Pareto optimality in multiobjective genetic algorithms is used to evolve a set of potential solutions towards a set of optimal non-dominated solutions. Genetic algorithms are well suited for implementing di±cult optimization problems where objective functions do not usually have good mathematical properties such as continuity, differentiability or convexity. In addition the genetic algorithms, as population based methods, may yield a complete Pareto front at each step of the iterative evolutionary procedure. The method is illustrated by means of a set of real data and an artificial multivariate time series data set.Fuzzy clustering, Internal criteria of cluster validity, Genetic algorithms, Multiobjective optimization, Time series, Pareto optimality

Use of blue dust in sintering

Sintering studies were undertaken through a full factorial design of experi¬ment to estimate the quantitative effect of blue dust along with other process variables. Responses from the experiments were then correlated with the process variables through a regression equation. The coefficients of the equation indicated that the coke breeze exerted maximum influence on the strength. It was possible to incorporate blue dust to the extent of 40% with respect to total iron ore fraction without impairing the properties of sinter

A Computer Oriented Algorithm to Determine the Raw-Mixture Composition for Sintering

Sintering is an agglomeration process of fine part-icles and widely used as a standard method for preparation of blast furnace-feed. In iron-ore sintering, iron ore fines viz. iron ore crushed to ---10 mm size, classifier fines, cyclone underflow, blue-dust etc. together with other iron-bearing waste materials viz. mill-scale, flue dust etc. are mixed with fluxing materials like limestone, dolomite etc. and sintered in a continuously operated sinter strand or a bench-scale sinter pot. The sintering of fine particles results from incipient fusion of materi-als due to heat liberated by combustion of coke-breeze incorporated in the raw mixture and also exothermic heat liberated through complex chemical reactions taking place during the process of sintering. Water added during mixing helps to maintain a proper permeability and return fines act as a supporting structure for the mixture

Fuzzy clustering of univariate and multivariate time series by genetic multiobjective optimization

COMISEF Working Papers Series WPS-028 08/02/2010 URL: http://comisef.eu/files/wps028.pd

Optimization of Lovastatin Self-Nanoemulsifying Solid Dosage Form

ACKNOWLEDGEMENTS: I am very thankful to Dr Sanjay S. Patel for his great support for this research work. We are also thankful to Manager of Abitech Corporation, USA, Corel Chemical Ltd., Ahmedabad, and Torrent Pharmaceuticals Ltd., Ahmedabad for providing us necessary ingredients. We are thankful to Shri B. M. Shah College of Pharmaceutical Education and Research, Modasa for providing technical support in form of instruments and guidance.Aim: The aim of present study was to develop and optimized self-nanoemulsifying solid dosage form (SNESDF) of Lovastatin for enhancing its solubility. Lovastatin (whose water solubility is 0.4 x 10-3 mg/mL) is considered to be a reasonable drug because of its high log P value (4.3) and good solubility in oils. Materials and Methods: The formulations were optimized by Box-Behnken statistical design in which the independent variables like Ratio of surfactant: co-surfactant (X1), oil: surfactant co surfactant (X2), and % Aerosil (X3). The formulations were characterized for its dependent variables such as Droplet size (Y1), transmittance (Y3), percentage of drug released within 5 minutes (Y3), and within 15 minutes (Y4). Results and Conclusion: Droplet size and zeta potential of the optimized batch was found to be 21.89 nm and -6.4 mV, respectively. 44.32 % and 90.78 % of the drug was found to be released within 5 min and 15 min, respectively. Hence, by formulating into SNESDF, the solubility of Lovastatin was found to be significantly improved.Objetivo: El objetivo del presente estudio fue desarrollar y optimizar la auto-nanoemulsión forma de dosificación sólida (SNESDF) de la Lovastatina para aumentar su solubilidad. Lovastatina (cuya solubilidad en agua es 0,4 x 10-3 mg / ml) se considera que es un fármaco razonable debido a su alto valor de log P (4,3) y una buena solubilidad en aceites. Materiales y Métodos: Las formulaciones fueron optimizadas por el diseño estadístico Box-Behnken en el cual las variables independientes como relación de tensioactivo: tensioactivo co-(X1), aceite: tensioactivo co tensioactivo (X2), y% Aerosil (X3). Las formulaciones se caracterizan por sus variables dependientes, tales como tamaño de la gota (Y1), la transmitancia (Y3), el porcentaje de fármaco liberado en 5 minutos (Y3), y dentro de 15 minutos (Y4). Resultados y Conclusiones: tamaño de la gota y el potencial zeta del lote optimizado resultó ser 21,89 nm y -6,4 mV, respectivamente. 44,32% y 90,78% del fármaco se encontró que se libera dentro de 5 min y 15 min, respectivamente. Por lo tanto, mediante la formulación en SNESDF de lovastatina , se encontró que la solubilidad mejoraba significativamente

A Beneficiation Scheme for Reduction of Alumina in Iron Ores from Barsua

In order to improve blast furnace productivity by reducing the alumina of iron ore fines from the present level of 3.3-3.9% to the desired level of 2.5%, a detailed characterisation followed by beneficiation studies compris-ing crushing, dry screening, washing, gravity separation of fines and slimes, on the seven individual 'type' and a 'composite' iron ore samples from Barsua Iron Mines were carried out at NML, Jamshedpur to find the amenability of beneficiation and develop a flow-sheet. Based on the find-ings from the studies, two conceptual flowsheets were designed.The first one consisted of crushing the composite sample (62.26% Fe, 2.01% Si02 and 4.22% A1203) to 25 mm followed by wet processing comprising scrubbing & wet screening at 8 mm and classification of -8mm fraction into sand (+100#) and slime (-100#). The -8+1 mm fraction of the sand would be subjected to jigging and -1mm+100 # fraction to tabling. The cyclone underflow obtained by treating the slime would be subjected to tabling as well. The yield of the combined concentrate of fines would be 28% and analyse 64.09% Fe, 1.9% Si02 and 2.95% A1203. The +8 mm lumps, 45% by weight would analyse 63.69% Fe, 1.52% Si02 and 3.8% A1203. Based on mainly grade and physical characteristics of individual type samples, the Second Flowsheet consists of separate proportioning, blending and treatment of two group of ores viz., Direct Ore (Friable, Mineable Transi-tional and Blue Dust) and Beneficiable Ore (Soft Lamina-ted , Lateritic , Hard Laminated and Massive). The flow-sheet consists of dry processing of Direct Ore (29% by weight with 63.55% Fe, 1.69% Si02 and 2.45% A1203) and wet processing of Beneficiable Ore (71% by weight with 61.39% Fe, 2.22% Si02 and 5.09% A1203). The Dry Circuit would consist of crushing the Direct to -25 mm and screening at 8 mm. The lumps and fines would weigh 8% and 21% and analyse 62.62% Fe, 1.79% Si02 and 2.92% A1203 and 63.9% Fe, 1.65% SiO2 and 2.27% Al2O3 respectively. The Benefic-iable will go through the wet circuit as described for the first flowsheet. The washed lump would be 36.43% by weight and analyse 63.4% Fe, 1.38% Si02 and 4.05% Al2O3. The combined lumps from Dry Circuit and Wet Circuit would be 44.43% by weight and analyse 63.25% Fe, 1.45% Si02 and 3.85% A1203.The combined fines from Dry Circuit and Wet Circuit (without concentrates from slime) would weigh 35.62% and analyse 64.1% Fe, 1.59% Si02 and 2.56% A1203. The yield will improve by an additional amount of 5-6% with slight increase in Al2O3 (2.85%) if table con-centrates from cyclone underflow and overflow are recovered. Although quality or quantity of lumps remain almost same in both the cases, there is substantial improvement in grade and yield of fines in the second flowsheet

Beneficiation of Low Grade Chromite Ores from Sukinda

In order to produce directly marketable chrome ore for export and domestic industries, most of the chromite ore beneficiation plants in Sukinda region treat selected rich ores with rejection of huge quantities of low and sub-grade ore (10-38% Cr2O3). Beneficiation is mostly limited to curshing, grinding, desliming and hydrosizing to prod-uce a concentrate of about 50% Cr203 with a yield of about 25-35%. By this also, a huge amount of sub grade fines of about 35-40% Cr203 has been accumulating in the mines. Currently very little efforts are made to treat these low grade ores or recover values from waste dumps. Recently, a study was undertaken at NML. to explore the possibility of developing a flowsheet to produce chromite concentrate preferably with Cr203 content of about 50% with Si02 about 2% from waste dumps analysing between 20 to 23% Cr203, with a view to using these as additional source of feed stock. Detailed physical characterisation, mineralogical analysis, bench and pilot scale studies were undertaken on these samples. The beneficiation process essentially invo- lved removal of ferruginous slime at stages by washing and hydrocycloning and enrichment of different size classified fractions by. simple gravity separation techniques like spiralling and tabling. It was observed that by adoption of the above operations, it was possible to upgrade these low grade ores to obtain concentrate having Cr203 of desired grade with high recovery

Physical method of upgradation for low grade wolframite pre-concentrate from Degana, Rajasthan

Tungsten is a strategic metal and mostly used in defence. It is also used in cutting tools, industrial, electrical, textile and leather sectors. India's tungsten reserves are very limited and the only workable deposit is restricted to Degana in Rajasthan. Tungsten deposit occurs in association with metamorphic rocks and granite igneous rock throughout the world. At Degana, two types of deposit are being worked at, one being quartz load wherein wolframite is mineralised in quartz vein and the other is finely disseminated tungsten mineralisation in the granite body. The sample under investigation belonged to off-grade tungsten pre-concentrate - I (PC - 1) produced at Degana Plant site, assaying 14.50% WOe 20.20% SiO, and 4.13% S. The objective of this study was to find the upgradation conforming to DMRL specification i.e. final wolframite concentrate with >65.0% WO,, and S and SiO, < 1.0% each. Detailed studies indicated that grinding the feed to 200 mesh followed by sulphide flotation at 4.5 and 8.0 pH and repeated vanning of non-sulphide could produce a wanner concen¬trate assaying 64.8% WO,. 1.0% SiO, and 3.0% S with a distribution of 48.8% WO3 in it. Thorough desliming followed by sulphide flotation and then treating on vanner times could produce a concentrate analysing 68.47% WO j, 0.5% SiO3 and 0.48% S which conforms to the DMRL sped¬fications