Abstract: | The current study is aimed at the development of a theoretical simulation tool based on Discrete Element Method (DEM) to 'interpret granular dynamics of solid bed in the cross section of the horizontal rotating cylinder at the microscopic level and subsequently apply this model to establish the transition behaviour, mixing and segregation.The simulation of the granular motion developed in this work is based on solving Newton's equation of motion for each particle in the granular bed subjected to the collisional forces, external forces and boundary forces. At every instant of time, the forces are tracked and the positions velocities and accelarations of each partcle is The software code for this simulation is written in VISUAL FORTRAN 90 After checking the validity of the code with special tests, it is used to investigate the transition behaviour of granular solids motion in the cross section of a rotating cylinder for various rotational speeds and fill fraction.This work is hence directed towards a theoretical investigation based on Discrete Element Method (DEM) of the motion of granular solids in the radial direction of the horizontal cylinder to elucidate the relationship between the operating parameters of the rotating cylinder geometry and physical properties ofthe granular solid.The operating parameters of the rotating cylinder include the various rotational velocities of the cylinder and volumetric fill. The physical properties of the granular solids include particle sizes, densities, stiffness coefficients, and coefficient of friction Further the work highlights the fundamental basis for the important phenomena of the system namely; (i) the different modes of solids motion observed in a transverse crosssection of the rotating cylinder for various rotational speeds, (ii) the radial mixing of the granular solid in terms of active layer depth (iii) rate coefficient of mixing as well as the transition behaviour in terms of the bed turnover time and rotational speed and (iv) the segregation mechanisms resulting from differences in the size and density of particles.The transition behaviour involving its six different modes of motion of the granular solid bed is quantified in terms of Froude number and the results obtained are validated with experimental and theoretical results reported in the literature The transition from slumping to rolling mode is quantified using the bed turnover time and a linear relationship is established between the bed turn over time and the inverse of the rotational speed of the cylinder as predicted by Davidson et al. [2000]. The effect of the rotational speed, fill fraction and coefficient of friction on the dynamic angle of repose are presented and discussed. The variation of active layer depth with respect to fill fraction and rotational speed have been investigated. The results obtained through simulation are compared with the experimental results reported by Van Puyvelde et. at. [2000] and Ding et at. [2002].The theoretical model has been further extended, to study the rmxmg and segregation in the transverse direction for different particle sizes and their size ratios. The effect of fill fraction and rotational speed on the transverse mixing behaviour is presented in the form of a mixing index and mixing kinetics curve. The segregation pattern obtained by the simulation of the granular solid bed with respect to the rotational speed of the cylinder is presented both in graphical and numerical forms. The segregation behaviour of the granular solid bed with respect to particle size, density and volume fraction of particle size has been investigated. Several important macro parameters characterising segregation such as mixing index, percolation index and segregation index have been derived from the simulation tool based on first principles developed in this work. |
URI: | http://dyuthi.cusat.ac.in/purl/2381 |
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Dyuthi-T0653.pdf | (5.339Mb) |
Abstract: | One can do research in pointfree topology in two ways. The rst is the contravariant way where research is done in the category Frm but the ultimate objective is to obtain results in Loc. The other way is the covariant way to carry out research in the category Loc itself directly. According to Johnstone [23], \frame theory is lattice theory applied to topology whereas locale theory is topology itself". The most part of this thesis is written according to the rst view. In this thesis, we make an attempt to study about 1. the frame counterparts of maximal compactness, minimal Hausdor - ness and reversibility, 2. the automorphism groups of a nite frame and its relation with the subgroups of the permutation group on the generator set of the frame |
Description: | Department of Mathematics Cochin University of Science and Technology |
URI: | http://dyuthi.cusat.ac.in/purl/4746 |
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Dyuthi-T1844.pdf | (460.2Kb) |
URI: | http://dyuthi.cusat.ac.in/purl/1014 |
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RAVEENDRAN NAIR B 1988.pdf | (259.7Kb) |
Abstract: | The incidence of diabetes is rapidly increasing and by 2030 an expected 592 million individuals are projected to be affected (WHO report). Hyperglycaemic condition is recognized as the causal link between diabetes and its complications. The chronic hyperglycemia resulting from diabetes brings about a rise in oxidative stress due to overproduction of reactive oxygen species (ROS) as a result of glucose auto oxidation and protein glycosylation. Generation of ROS leads to oxidative damage of the structural components (such as lipids, DNA and proteins) of cells and potentiate diabetes related complications. Oxidative insult in cells is also created by the impairment in functioning of endogenous antioxidant enzymes because of their non enzymatic glycosylation and oxidation. The prolonged exposure of oxidative stress may cause insulin resistance by triggering an alteration in cellular redox balance. Several lines of evidence suggest that oxidative stress occurs in diabetes and could have a role in the development of insulin resistance. The cause and cellular mechanism responsible for this abnormality is not fully understand despite of intense investigative efforts. However it is unknown whether it is the cause or consequence of diabetes. Despite strong experimental evidence indicating that oxidative stress may determine the onset and progression of late-diabetic complications, controversy exists between the cause and associative relationship between oxidative stress and diabetes mellitus. Disruption of glucose homeostasis is a characteristic feature of Non-insulin dependent diabetes mellitus (NIDDM) and is associated with some complications including cardiovascular disease and renal failure. Glucose transport, the rate limiting step in glucose metabolism, can be activated in peripheral tissues by two distinct pathways. One stimulated by insulin through IRS-1/PI3K, Preface Page 2 the other by muscle contraction/exercise through the activation of AMPK. Both pathways also increase the phosphorylation and activity of MAPK family components of which p38 MAPK participates in the full activation of GLUT4.Insulin exerts its biological effect upon binding with the insulin receptor (IR) thereby activating the downstream signaling that lead to enhanced glucose uptake. In skeletal muscle, it potentiates glucose transport through PI3K mediated or non-PI3K mediated pathways. Alterations or defects in its signal transduction pathway was found in diabetic patients associated with decreased levels of IRb, IRS-1, and PI3K. In the insulin signaling, PI3K is a key molecule and inhibition of PI3K completely abolish insulin stimulated uptake. Akt or Pkb is an important downstream target of insulin stimulated glucose transport and metabolism.Impairment in fuel metabolism occurs in obesity, and this impairment is a leading pathogenic factor in type 2 diabetes. The insulin resistance associated with type 2 diabetes is most profound at the level of skeletal muscle as this is the primary site of glucose and fatty acid utilization. Therefore, an understanding of how to activate AMPK in skeletal muscle would offer significant pharmacologic benefits in the treatment of type 2 diabetes. Metformin and the thiazolidinedione drugs exert the effects via activation of AMPK. Activation of AMPK occurs in response to exercise, an activity known to have significant benefit for type 2 diabetics. AMPK serves as sensor of energy status whose activity is triggered in response to changes in nutritional status in order to modulate tissue-specific metabolic pathways |
URI: | http://dyuthi.cusat.ac.in/purl/5151 |
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Dyuthi-T2185.pdf | (9.806Mb) |
URI: | http://dyuthi.cusat.ac.in/purl/5083 |
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Dyuthi-T 2146.pdf | (10.28Mb) |
URI: | http://dyuthi.cusat.ac.in/purl/5122 |
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Dyuthi-T 2187.pdf | (6.440Mb) |
Abstract: | A critical survey of the fruits and vegetable markets of the towns and cities in South India reveals that banana fruit stalk wastes share a dominant proportion among the solid wastes generated. In the light of the review of literature presented in the foregoing section, few reports are available on the utilisation of banana waste for the production of alcoholic beverages, biogas, and single cell protein. However, it is not yet tried for the production of industrial enzymes. Moreover, preliminary fermentation studies conducted under uncontrolled conditions revealed that banana fruit stalk could be aptly utilised as solid substrate? for the industrial production of microbial amylases and cellulases at a cheaper cost. Therefore, it was proposed to conduct a detailed study towards the development of a suitable fermentation process for the production of industrial enzymes using banana fruit stalk wastes, which is rich in carbohydrate, as solid substrate, employing bacteria, under SSF. |
Description: | Department of Biotechnology, Cochin University of Science & Technology, |
URI: | http://dyuthi.cusat.ac.in/purl/3362 |
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Dyuthi-T1339.pdf | (3.715Mb) |
URI: | http://dyuthi.cusat.ac.in/purl/1739 |
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Dyuthi-T0202.pdf | (2.099Mb) |
URI: | http://dyuthi.cusat.ac.in/xmlui/purl/2021 |
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Dyuthi-T0432.pdf | (2.889Mb) |
Abstract: | there has been much research on analyzing various forms of competing risks data. Nevertheless, there are several occasions in survival studies, where the existing models and methodologies are inadequate for the analysis competing risks data. ldentifiabilty problem and various types of and censoring induce more complications in the analysis of competing risks data than in classical survival analysis. Parametric models are not adequate for the analysis of competing risks data since the assumptions about the underlying lifetime distributions may not hold well. Motivated by this, in the present study. we develop some new inference procedures, which are completely distribution free for the analysis of competing risks data. |
Description: | Department of Statistics, Cochin University of Science and Technology |
URI: | http://dyuthi.cusat.ac.in/purl/3810 |
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Dyuthi-T1741.pdf | (1.808Mb) |
Abstract: | The thesis has covered various aspects of modeling and analysis of finite mean time series with symmetric stable distributed innovations. Time series analysis based on Box and Jenkins methods are the most popular approaches where the models are linear and errors are Gaussian. We highlighted the limitations of classical time series analysis tools and explored some generalized tools and organized the approach parallel to the classical set up. In the present thesis we mainly studied the estimation and prediction of signal plus noise model. Here we assumed the signal and noise follow some models with symmetric stable innovations.We start the thesis with some motivating examples and application areas of alpha stable time series models. Classical time series analysis and corresponding theories based on finite variance models are extensively discussed in second chapter. We also surveyed the existing theories and methods correspond to infinite variance models in the same chapter. We present a linear filtering method for computing the filter weights assigned to the observation for estimating unobserved signal under general noisy environment in third chapter. Here we consider both the signal and the noise as stationary processes with infinite variance innovations. We derived semi infinite, double infinite and asymmetric signal extraction filters based on minimum dispersion criteria. Finite length filters based on Kalman-Levy filters are developed and identified the pattern of the filter weights. Simulation studies show that the proposed methods are competent enough in signal extraction for processes with infinite variance.Parameter estimation of autoregressive signals observed in a symmetric stable noise environment is discussed in fourth chapter. Here we used higher order Yule-Walker type estimation using auto-covariation function and exemplify the methods by simulation and application to Sea surface temperature data. We increased the number of Yule-Walker equations and proposed a ordinary least square estimate to the autoregressive parameters. Singularity problem of the auto-covariation matrix is addressed and derived a modified version of the Generalized Yule-Walker method using singular value decomposition.In fifth chapter of the thesis we introduced partial covariation function as a tool for stable time series analysis where covariance or partial covariance is ill defined. Asymptotic results of the partial auto-covariation is studied and its application in model identification of stable auto-regressive models are discussed. We generalize the Durbin-Levinson algorithm to include infinite variance models in terms of partial auto-covariation function and introduce a new information criteria for consistent order estimation of stable autoregressive model.In chapter six we explore the application of the techniques discussed in the previous chapter in signal processing. Frequency estimation of sinusoidal signal observed in symmetric stable noisy environment is discussed in this context. Here we introduced a parametric spectrum analysis and frequency estimate using power transfer function. Estimate of the power transfer function is obtained using the modified generalized Yule-Walker approach. Another important problem in statistical signal processing is to identify the number of sinusoidal components in an observed signal. We used a modified version of the proposed information criteria for this purpose. |
Description: | Department of Statistics, Cochin University of Science and Technology |
URI: | http://dyuthi.cusat.ac.in/purl/2770 |
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Dyuthi-T0793.pdf | (2.046Mb) |
URI: | http://dyuthi.cusat.ac.in/purl/5293 |
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Dyuthi T-2329.pdf | (7.746Mb) |
Description: | Department of Statistics, Cochin University of Science and Technology |
URI: | http://dyuthi.cusat.ac.in/purl/2574 |
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Dyuthi-T0703.pdf | (5.795Mb) |
URI: | http://dyuthi.cusat.ac.in/purl/5247 |
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Dyuthi T-2283.pdf | (1.706Mb) |
URI: | http://dyuthi.cusat.ac.in/purl/5439 |
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Dyuthi T-2480.pdf | (3.707Mb) |
Abstract: | This thesis Entitled “modelling and analysis of recurrent event data with multiple causes.Survival data is a term used for describing data that measures the time to occurrence of an event.In survival studies, the time to occurrence of an event is generally referred to as lifetime.Recurrent event data are commonly encountered in longitudinal studies when individuals are followed to observe the repeated occurrences of certain events. In many practical situations, individuals under study are exposed to the failure due to more than one causes and the eventual failure can be attributed to exactly one of these causes.The proposed model was useful in real life situations to study the effect of covariates on recurrences of certain events due to different causes.In Chapter 3, an additive hazards model for gap time distributions of recurrent event data with multiple causes was introduced. The parameter estimation and asymptotic properties were discussed .In Chapter 4, a shared frailty model for the analysis of bivariate competing risks data was presented and the estimation procedures for shared gamma frailty model, without covariates and with covariates, using EM algorithm were discussed. In Chapter 6, two nonparametric estimators for bivariate survivor function of paired recurrent event data were developed. The asymptotic properties of the estimators were studied. The proposed estimators were applied to a real life data set. Simulation studies were carried out to find the efficiency of the proposed estimators. |
Description: | Department of Statistics, Cochin University of Science and Technology |
URI: | http://dyuthi.cusat.ac.in/purl/3031 |
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Dyuthi-T1006.pdf | (8.122Mb) |
Abstract: | The thesis deals with some of the non-linear Gaussian and non-Gaussian time models and mainly concentrated in studying the properties and application of a first order autoregressive process with Cauchy marginal distribution. In this thesis some of the non-linear Gaussian and non-Gaussian time series models and mainly concentrated in studying the properties and application of a order autoregressive process with Cauchy marginal distribution. Time series relating to prices, consumptions, money in circulation, bank deposits and bank clearing, sales and profit in a departmental store, national income and foreign exchange reserves, prices and dividend of shares in a stock exchange etc. are examples of economic and business time series. The thesis discuses the application of a threshold autoregressive(TAR) model, try to fit this model to a time series data. Another important non-linear model is the ARCH model, and the third model is the TARCH model. The main objective here is to identify an appropriate model to a given set of data. The data considered are the daily coconut oil prices for a period of three years. Since it is a price data the consecutive prices may not be independent and hence a time series based model is more appropriate. In this study the properties like ergodicity, mixing property and time reversibility and also various estimation procedures used to estimate the unknown parameters of the process. |
URI: | http://dyuthi.cusat.ac.in/purl/40 |
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Dyuthi-T0177.pdf | (1.709Mb) |
Abstract: | Comets are the spectacular objects in the night sky since the dawn of mankind. Due to their giant apparitions and enigmatic behavior, followed by coincidental calamities, they were termed as notorious and called as `bad omens'. With a systematic study of these objects modern scienti c community understood that these objects are part of our solar system. Comets are believed to be remnant bodies of at the end of evolution of solar system and possess the material of solar nebula. Hence, these are considered as most pristine objects which can provide the information about the conditions of solar nebula. These are small bodies of our solar system, with a typical size of about a kilometer to a few tens of kilometers orbiting the Sun in highly elliptical orbits. The solid body of a comet is nucleus which is a conglomerated mixture of water ice, dust and some other gases. When the cometary nucleus advances towards the Sun in its orbit the ices sublimates and produces the gaseous envelope around the nucleus which is called coma. The gravity of cometary nucleus is very small and hence can not in uence the motion of gases in the cometary coma. Though the cometary nucleus is a few kilometers in size they can produce a transient, extensive, and expanding atmosphere with size several orders of magnitude larger in space. By ejecting gas and dust into space comets became the most active members of the solar system. The solar radiation and the solar wind in uences the motion of dust and ions and produces dust and ion tails, respectively. Comets have been observed in di erent spectral regions from rocket, ground and space borne optical instruments. The observed emission intensities are used to quantify the chemical abundances of di erent species in the comets. The study of various physical and chemical processes that govern these emissions is essential before estimating chemical abundances in the coma. Cameron band emission of CO molecule has been used to derive CO2 abundance in the comets based on the assumption that photodissociation of CO2 mainly produces these emissions. Similarly, the atomic oxygen visible emissions have been used to probe H2O in the cometary coma. The observed green ([OI] 5577 A) to red-doublet emission ([OI] 6300 and 6364 A) ratio has been used to con rm H2O as the parent species of these emissions. In this thesis a model is developed to understand the photochemistry of these emissions and applied to several comets. The model calculated emission intensities are compared with the observations done by space borne instruments like International Ultraviolet Explorer (IUE) and Hubble Space Telescope (HST) and also by various ground based telescopes. |
Description: | Space Physics Laboratory Vikram Sarabhai Space Centre Indian Space Research Organisation Thiruvananthapuram |
URI: | http://dyuthi.cusat.ac.in/purl/3748 |
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Dyuthi-T1710.pdf | (9.535Mb) |
URI: | http://dyuthi.cusat.ac.in/purl/5447 |
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Dyuthi T-2488.pdf | (6.226Mb) |
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