Showing papers by "Indian Institute of Technology Bombay published in 2000"

Finite-Time Stability of Continuous Autonomous Systems

Abstract: Finite-time stability is defined for equilibria of continuous but non-Lipschitzian autonomous systems. Continuity, Lipschitz continuity, and Holder continuity of the settling-time function are studied and illustrated with several examples. Lyapunov and converse Lyapunov results involving scalar differential inequalities are given for finite-time stability. It is shown that the regularity properties of the Lyapunov function and those of the settling-time function are related. Consequently, converse Lyapunov results can only assure the existence of continuous Lyapunov functions. Finally, the sensitivity of finite-time-stable systems to perturbations is investigated.

Mixing and Segregation of Granular Materials

Abstract: ▪ Abstract Granular materials segregate. Small differences in either size or density lead to flow-induced segregation, a complex phenomenon without parallel in fluids. Modeling of mixing and segregation processes requires the confluence of several tools, including continuum and discrete descriptions (particle dynamics, Monte Carlo simulations, cellular automata computations) and, often, considerable geometrical insight. None of these viewpoints, however, is wholly satisfactory by itself. Moreover, continuum and discrete descriptions of granular flows are regime dependent, and this fact may require adopting different subviewpoints. This review organizes a body of knowledge that forms—albeit imperfectly—the beginnings of an expandable continuum framework for the description of mixing and segregation of granular materials. We focus primarily on noncohesive particles, possibly differing in size, density, shape, etc. We present segregation mechanisms and models for size and density segregation and introduce ch...

Natural extracts using supercritical carbon dioxide

Abstract: INTRODUCTION Importance of Nature Cure Naturopathy Natural Extracts CO2 as an SCF Solvent SCFE Process SCFE Applications References Figure Captions - Chapter 1 Figures 11 - 13 FUNDAMENTALS OF SUPERCRITICAL FLUIDS AND PHASE EQUILIBRIA Process Schemes and Parameters in SCFE Thermodynamics of SCF State Variability of Density with P and T Addition of Cosolvent to SCF Solvent Solubility Behavior in SCF Solvent Solubility Isotherms and Cross Over Phenomena Solubility Isobars Pressure and Temperature Effects Solvent Capacity and Selectivity Cosolvent Effects SCF Phase Equilibrium Behavior Liquid-Fluid Phase Equilibria Solid-Fluid Phase Equilibria Polymer-Fluid Phase Equilibria Thermodynamic Modelling The Equation of State Approach Solid-Fluid Equilibrium Calculations Mixing Rules CS and GC Methods Solubility Predictions of Solid from Pure Components Properties Liquid-Fluid Equilibrium Calculations Mixing Rules Regression of Binary Adjustable Parameters Prediction of Multicomponent Data from Binary Interaction Constants Prediction of Phase Boundaries Mixture Critical Point Calculations Multiphase (L-L-V) Calculations Solubility Predictions Using Solvent-Cluster Interaction Model Solubility Calculations from Correlations Selectivity of Natural Molecules from Pure Component Solubilities Thermophysical Properties of CO2 Nomenclature References Figure Captions - Chapter 2 Figures 21 - 227 (b) FUNDAMENTAL TRANSPORT PROCESES IN SUPERCRITICAL FLUID EXTRACTION Transport Properties of SCFs Viscosity Diffusivity Thermal Conductivity Interfacial Tension Mass Transfer Behavior SCFE From Solid Feed Mechanism of Transport from Solids Stages of Extraction from Different Natural Materials SCFF from Liquid Feed Fractionation of Liquids by SFC Mass Transfer Modelling For SCFE from Solids Process Parameters Mass Transfer Coefficients Effect of Axial Dispersion and Convective Flows Shrinking Core Leaching Model Heat Transfer in SCFs Heat Transfer Coefficients Effects of Free Convective Flow Heat Transfer Coefficient for Two Phase Flow Heat Exchanger Specifications Nomenclature References Figure Captions - Chapter 3 Figures 31(a) - 316 FLAVOR AND FRAGRANCE EXTRACTS Market Demand Natural Essential Oils Methods of Recovery of Natural Essential Oils Steam Distillation Maceration Enfleurage Cold Expression Extraction with Volatile Organic Solvents Choice of Solvents Purification of Crude Extract Vacuum Distillation Molecular Distillation Liquid-Liquid Fractionation Supercritical CO2 Extraction Commercial Advantage SC CO2 Extracted Floral Fragrance Jasmine Fragrance Rose Fragrance Bitter Orange Flower Fragrance Lavender Inflorescence Fragrance Marigold Fragrance Sandalwood Fragrance Vetiver Fragrance References Figure Captions - Chapter 4 Figures 41 - 47(b) FRUIT EXTRACTS Importance of Recovery Citrus Oil Recovery During Juice Extraction Flavoring Components in Fruits Stability and Quality CO2 Extraction Processes Deterpenation of Citrus Oil by SC CO2 Dealcoholation of Fruit Juice by SC CO2 Enzyme Inactivation and Sterilization by +SC CO2 References Figure Captions - Chapter 5 Figures 51 - 56 SPICE EXTRACTS Importance of Recovery Classification of Spices Therapeutic Properties of Spices Spice Constituents Production of Spice Extracts SC CO2 Extraction and Fractionation Celery Seeds Red Chili Paprika Ginger Nutmeg Pepper Vanilla Cardamom Fennel, Caraway and Coriander Garlic Cinnamon Market Trends References Figure Captions - Chapter 6 Figure 61 HERBAL EXTRACTS Importance of Recovery Herbal Remedies Recovery Methods Antioxidative and Antimicrobial Constituents Anti-inflammatory Constituents Anti-Cancerous Alkaloids Anti-Carcinogenic Polyphenols Medicinal Constituents of Tea Extract Fat Regulating Agent Therapeutic Oils and Fatty Acids References NATURAL ANTIOXIDANTS Importance of Recovery Classification Botanicals with Antioxidative Activity Tocopherols as Antioxidants Recovery by SC CO2 Spice and Herbal Extracts as Antioxidants Recovery by SC CO2 Plant Leaf Extracts as Antioxidants Flavonoids Recovery of Flavonoids Carotenoids as Antioxidants Recovery of ? Carotene by SC CO2 Solubility of Antioxidants in SC CO2 References Figure Captions - Chapter 8 Figures 81 - 87 NATURAL FOOD COLORS Carotenoids as Food Colors Recovery of Carotenoids by SC CO2 Grass Orange Peel Turmeric Paprika Red Chili Carrot Marigold Flowers Annatto Other Natural Colors Anthocyanins as Food Colors Classification of Anthocyanins Recovery of Anthocyanins Commercial Anthocyanin-based Food Colors Betacyanins References Figure Captions - Chapter 9 Figures 91 - 92 PLANT AND ANIMAL LIPIDS Importance of Recovery Recovery Methods Separation of FFA from Vegetable Oil by SC CO2 Fractionation of PUFA from Animal Lipids Refining and Deodorisation of Vegetable Oil Fractionation of Glycerides Extraction of Oil from Oil Bearing Materials Sunflower Oil Corn Germ Oil Soybean Oil Olive Husk Oil Grape Seed Oil Animal Lipids Deoiling of Lecithin by SC CO2 Soya Phospholipids Oat Lecithin Canola Lecithin PC from Deoiled Cottonseed PC from Egg Yolk Dilipidation and Decholesterification of Food Butter Egg Yolk Powder Fish and Meat Muscles References Figure Captions - Chapter 10 Figures 101 - 1012 NATURAL PESTICIDES Importance of Recovery Bioactivity of Neem Neem Based Pesticides Azadirachtin-based Formulations Commercial Production Recovery of Azadirachtin from Neem Kernel Conventional Processes Supercritical CO2 Extraction Pyrethrum Based Pesticides Recovery of Pyrethrins Nicotine Based Pesticides Reovery of Nicotine by SC CO2 References APPENDICES Thermophysical Properties of Carbon Dioxide Definitions of Fatty Acids and Their Compositions in Various Oils Some Statistics on Major Vegetable Oils and Oilseeds INDEX

Engineering Aspects of Industrial Liquid-Phase Air Oxidation of Hydrocarbons

Abstract: Liquid-phase air oxidation of hydrocarbons, notably p-xylene, cumene, ethylbenzene/isobutane, cyclohexane, and n-butane, is of great scientific, technological, and commercial importance. This state-of-the-art paper covers the chemistry and engineering science aspects of these reactions. The role of uncatalyzed reactions and metal ion and mixed metal ion catalysts with bromide activation is discussed. An analysis is presented for the role of mass transfer in influencing the rate of reaction and selectivity for the desired product. Different types of reactors that are used, notably bubble-column reactors and mechanically agitated reactors, are analyzed, and a simple basis is provided for selection of reactors. Some emerging oxidation systems, notably oxidation of cycloalkenes (cyclohexene/cyclooctene/cyclododecene) and oxidation of isobutane under supercritical conditions, are presented. New strategies for conducting air oxidations, such as in biphasic systems (including fluorous biphasic systems), biocatalysis, photocatalysis, etc., are emerging and illustrate the considerable tailoring of the reaction microenvironment that is becoming possible. In some cases, it may be possible to manipulate chemo-, regio-, and enantioselectivity in these reactions.

Data mining for hypertext: a tutorial survey

Abstract: With over 800 million pages covering most areas of human endeavor, the World-wide Web is a fertile ground for data mining research to make a difference to the effectiveness of information search. Today, Web surfers access the Web through two dominant interfaces: clicking on hyperlinks and searching via keyword queries. This process is often tentative and unsatisfactory. Better support is needed for expressing one's information need and dealing with a search result in more structured ways than available now. Data mining and machine learning have significant roles to play towards this end.In this paper we will survey recent advances in learning and mining problems related to hypertext in general and the Web in particular. We will review the continuum of supervised to semi-supervised to unsupervised learning problems, highlight the specific challenges which distinguish data mining in the hypertext domain from data mining in the context of data warehouses, and summarize the key areas of recent and ongoing research.

Algorithm 806: SPRNG: a scalable library for pseudorandom number generation

Abstract: In this article we present background, rationale, and a description of the Scalable Parallel Random Number Generators (SPRNG) library. We begin by presenting some methods for parallel pseudorandom number generation. We will focus on methods based on parameterization, meaning that we will not consider splitting methods such as the leap-frog or blocking methods. We describe, in detail, parameterized versions of the following pseudorandom number generators: (i) linear congruential generators, (ii) shift-register generators, and (iii) lagged-Fibonacci generators. We briefly describe the methods, detail some advantages and disadvantages of each method, and recount results from number theory that impact our understanding of their quality in parallel applications. SPRNG was designed around the uniform implementation of different families of parameterized random number generators. We then present a short description of SPRNG. The description contained within this document is meant only to outline the rationale behind and the capabilities of SPRNG. Much more information, including examples and detailed documentation aimed at helping users with putting and using SPRNG on scalable systems is available at htt;//sprng.sc.fsu.edu. In this description of SPRNG we discuss the random-number generator library as well as the suite of tests of randomness that is an integral part of SPRNG. Random-number tools for parallel Monte Carlo applications must be subjected to classical as well as new types of empirical tests of randomness to eliminate generators that show defects when used in scalable envionments.

Effects of Intermicellar Exchange Rate on the Formation of Silver Nanoparticles in Reverse Microemulsions of AOT

Abstract: We report the effects of intermicellar exchange rate on absorption spectra and particle size of silver nanoparticles synthesized in reverse micelles of AOT The silver nanoparticles are prepared by the method of mixing of two microemulsions, one containing the silver nitrate and the other containing sodium borohydride The intermicellar exchange rate is varied by changing the organic solvent, surfactant (SDS, NP-5, and DTAB), and organic (benzyl alcohol and toluene) additives The higher intermicellar exchange rate is found to give smaller particle size and blue shift in the absorption spectra An interesting and potentially useful effect has been observed in that addition of a small amount of a nonionic surfactant significantly reduces the particle size

Landslide hazard susceptibility mapping based on terrain and climatic factors for tropical monsoon regions

Abstract: Deep weathering, residual material (colluvium) and random rainfall intensity are mainly responsible for landslides in tropical monsoon regions. These parameters are often not taken into consideration in a landslide susceptibility assessment. Sustainable resources development in this region requires information on the spatial distribution of areas susceptible to landslides. This study highlights various aspects of the landslides that take place on the west coast of India and a methodology developed for landslide susceptibility mapping.

Crystallisation kinetics in AO-Al2O3-SiO2-B2O3 glasses (A = Ba, Ca, Mg)

Abstract: The crystallisation kinetics of AO-Al2O3-SiO2-B2O3glasses (A = Ba, Ca, Mg) was investigated using DTA, XRD, and microstructural studies. Moreover, the influence of nucleating agentssuch as TiO2, ZrO2, Cr2O3, and Ni on MgO base glasses waselucidated. The glasses are of interest for the development ofsealants in Solid Oxide Fuel Cells (SOFC). The activation energy ofcrystal growth, E a, was evaluated for the different glassesusing the modified Kissinger equation. The preparation method of theglasses seems to determine whether surface or bulk nucleation is thedominant mechanism. The E a values vary between 330 and622 kJ/mol. The nucleating agents tend to enhance E a exceptZrO2. An increase of the Al2O3 concentration induces phaseseparation and decreases E a. The results are discussed onthe basis of the structural role and chemical properties of the Alions as well as with respect to the possible use of the glasses inSOFC.

Instability criteria for hot deformation of materials

Abstract: Forming and forging processes are among the oldest and most important materials related technologies. New materials technologies centre on the development and widespread use of thermomechan...

Tuned liquid dampers for controlling earthquake response of structures

Abstract: Numerical simulations of a single-degree-of-freedom (SDOF) structure, rigidly supporting a tuned liquid damper (TLD) and subjected to both real and artificially generated earthquake ground motions, show that a properly designed TLD can significantly reduce the structure's response to these motions. The TLD is a rigid, rectangular tank with shallow water in it. Its fundamental linear sloshing frequency is tuned to the structure's natural frequency. The TLD is more effective in reducing structural response as the ground excitation level increases. This is because it then dissipates more energy due to sloshing and wave breaking. A larger water-depth to tank-length ratio than previous studies suggested, which still falls within the constraint of shallow water theory, is shown to be more suitable for excitation levels expected in strong earthquake motions. A larger water-mass to structure-mass ratio is shown to be required for a TLD to remain equally effective as structural damping increases. Furthermore, the reduction in response is seen to be fairly insensitive to the bandwidth of the ground motion but is dependent on the structure's natural frequency relative to the significant ground frequencies. Finally, a practical approach is suggested for the design of a TLD to control earthquake response. Copyright © 2000 John Wiley & Sons, Ltd.

Heat exchanger design targets for minimum area and cost

Abstract: A methodology is proposed to determine the feasible region for shell and tube heat exchanger designs on a pressure drop diagram. By accounting for operating as well as geometrical constraints, the feasible region is de®ned so as to eliminate trial-and-error during the design activity. Every point on this plot of shellside versus tubeside pressure drop corresponds to a unique design in terms of tube length, shell diameter and baffle spacing. Furthermore, curves may be plotted for designs corresponding to a specified heat exchange area or a given total annual cost. Such curves permit screening of various design options prior to detailed rating of the exchangers, and allow heat exchanger design targets to be established for minimum area or cost. The area target ensures an exchanger of the smallest size with minimum capital cost, whereas the cost target yields the optimum pressure drops accounting for the tradeoff between power consumption and heat exchanger area. The methodology is equation-based and can be conveniently implemented on a computer.

Synthesis, spectral characterization, and structural studies of 2-aminobenzoate complexes of divalent alkaline earth metal ions: X-ray crystal structures of [Ca(2-aba)2(OH2)3]infinity, [[Sr(2-aba)2(OH2)2].H2O]infinity, and [Ba(2-aba)2(OH2)]infinity (2-abaH = 2-NH2C6H4COOH).

Abstract: Reactions of alkaline earth metal chlorides with 2-aminobenzoic acid (2-abaH) have been investigated. The treatment of MCl2·nH2O (M = Mg, Ca, Sr or Ba) with 2-abaH in a 1:2 ratio in a MeOH/H2O/NH3 mixture leads to the formation of anthranilate complexes [Mg(2-aba)2] (1), [Ca(2-aba)2(OH2)3]∞ (2), [{Sr(2-aba)2(OH2)2}·H2O)]∞ (3), and [Ba(2-aba)2(OH2)]∞ (4), respectively. Alternatively, these products can also be obtained starting from the corresponding metal acetates. Anthranilate complexes 1−4 have been characterized with the aid of elemental analysis, pH measurements, thermal analysis, and infrared, ultraviolet, and NMR (1H and 13C) spectroscopic studies. All the products are found to be thermally very stable and do not melt on heating to 250 °C. Thermal studies of complexes 2−4, however, indicate the loss of coordinated and lattice water molecules below 200 °C. In the case of the magnesium complex, the analytical and thermogravimetric studies indicate the absence of any coordinated or uncoordinated water ...

Slicing concurrent programs

Abstract: Slicing is a well-known program analysis technique for analyzing sequential programs and found useful in debugging, testing and reverse engineering. This paper extends the notion of slicing to concurrent programs with shared memory, interleaving semantics and mutual exclusion. Interference among concurrent threads or processes complicates the computation of slices of concurrent programs. Further, unlike slicing of sequential programs, a slicing algorithm for concurrent programs needs to differentiate between loop-independent data dependence and certain loop-carried data dependences.We show why previous methods do not give precise solutions in the presence of nested threads and loops and describe our solution that correctly and efficiently computes precise slices. Though the complexity of this algorithm is exponential on the number of threads, a number of optimizations are suggested. Using these optimizations, we are able to get near linear behavior for many practical concurrent programs.

Design of Sensor Network Based on the Signed Directed Graph of the Process for Efficient Fault Diagnosis

Abstract: An optimally located network of sensors is a prerequisite for successful application of fault diagnosis techniques. Most of the previous work in the area of fault diagnosis deals with methodologies for identifying possible faults, given sensor data. Available literature suggests that very little work has been done on methods for optimally locating the sensors for efficient fault diagnosis. Some algorithms based on the concepts of observability and resolution were discussed in our previous work (ref 1: Raghuraj et al. AIChE J. 1999, 45 (2), 310). These algorithms are based on a digraph (DG) representation of the process. In this article, the sensor location work is extended to use the signed directed graph (SDG) representation of the process. Various issues involved in utilizing the SDG of the process for the problem of sensor location are discussed. Algorithms for sensor network design based on the SDG of the process are detailed and applied to two chemical engineering case studies. It is shown that bett...

Efficient policies for increasing capacity in Bluetooth: an indoor pico-cellular wireless system

Abstract: In indoor pico-cellular wireless systems, such as Bluetooth, a pico-cell has a master-slave configuration. Bluetooth is a centralized master driven system that supports time division duplex medium access control. A pico-cell has a limit on the maximum number of active slaves. In Bluetooth, a pico-cell can have a maximum of seven slaves in active state (capable of transmitting and receiving data). The remaining slaves in a pico-cell remain in an inactive state. Having more than seven slaves connected to the master can be advantageous in many situations. Having a large number of slaves in one pico-cell as compared to forming new pico-cells can lead to lower power consumption and a relatively simple network architecture. We investigate different methods of increasing the capacity of Bluetooth pico-cells. We propose new policies using the park mode to increase the number slaves virtually connected to a master. These policies can have a significant impact on system parameters such as the throughput, packet delays and dropping probability of packets.