| URI: | http://dyuthi.cusat.ac.in/purl/1663 |
| Files | Size |
|---|---|
| Dyuthi-T0148.pdf | (2.294Mb) |
| Abstract: | Multivariate lifetime data arise in various forms including recurrent event data when individuals are followed to observe the sequence of occurrences of a certain type of event; correlated lifetime when an individual is followed for the occurrence of two or more types of events, or when distinct individuals have dependent event times. In most studies there are covariates such as treatments, group indicators, individual characteristics, or environmental conditions, whose relationship to lifetime is of interest. This leads to a consideration of regression models.The well known Cox proportional hazards model and its variations, using the marginal hazard functions employed for the analysis of multivariate survival data in literature are not sufficient to explain the complete dependence structure of pair of lifetimes on the covariate vector. Motivated by this, in Chapter 2, we introduced a bivariate proportional hazards model using vector hazard function of Johnson and Kotz (1975), in which the covariates under study have different effect on two components of the vector hazard function. The proposed model is useful in real life situations to study the dependence structure of pair of lifetimes on the covariate vector . The well known partial likelihood approach is used for the estimation of parameter vectors. We then introduced a bivariate proportional hazards model for gap times of recurrent events in Chapter 3. The model incorporates both marginal and joint dependence of the distribution of gap times on the covariate vector . In many fields of application, mean residual life function is considered superior concept than the hazard function. Motivated by this, in Chapter 4, we considered a new semi-parametric model, bivariate proportional mean residual life time model, to assess the relationship between mean residual life and covariates for gap time of recurrent events. The counting process approach is used for the inference procedures of the gap time of recurrent events. In many survival studies, the distribution of lifetime may depend on the distribution of censoring time. In Chapter 5, we introduced a proportional hazards model for duration times and developed inference procedures under dependent (informative) censoring. In Chapter 6, we introduced a bivariate proportional hazards model for competing risks data under right censoring. The asymptotic properties of the estimators of the parameters of different models developed in previous chapters, were studied. The proposed models were applied to various real life situations. |
| Description: | Department of Statistics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2708 |
| Files | Size |
|---|---|
| Dyuthi-T0758.pdf | (5.959Mb) |
| Abstract: | Reliability analysis is a well established branch of statistics that deals with the statistical study of different aspects of lifetimes of a system of components. As we pointed out earlier that major part of the theory and applications in connection with reliability analysis were discussed based on the measures in terms of distribution function. In the beginning chapters of the thesis, we have described some attractive features of quantile functions and the relevance of its use in reliability analysis. Motivated by the works of Parzen (1979), Freimer et al. (1988) and Gilchrist (2000), who indicated the scope of quantile functions in reliability analysis and as a follow up of the systematic study in this connection by Nair and Sankaran (2009), in the present work we tried to extend their ideas to develop necessary theoretical framework for lifetime data analysis. In Chapter 1, we have given the relevance and scope of the study and a brief outline of the work we have carried out. Chapter 2 of this thesis is devoted to the presentation of various concepts and their brief reviews, which were useful for the discussions in the subsequent chapters .In the introduction of Chapter 4, we have pointed out the role of ageing concepts in reliability analysis and in identifying life distributions .In Chapter 6, we have studied the first two L-moments of residual life and their relevance in various applications of reliability analysis. We have shown that the first L-moment of residual function is equivalent to the vitality function, which have been widely discussed in the literature .In Chapter 7, we have defined percentile residual life in reversed time (RPRL) and derived its relationship with reversed hazard rate (RHR). We have discussed the characterization problem of RPRL and demonstrated with an example that the RPRL for given does not determine the distribution uniquely |
| Description: | Department of Statistics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/3157 |
| Files | Size |
|---|---|
| Dyuthi-T1131.pdf | (3.496Mb) |
| URI: | http://dyuthi.cusat.ac.in/purl/5509 |
| Files | Size |
|---|---|
| Dyuthi T-2551.pdf | (44.51Mb) |
| Abstract: | Queueing system in which arriving customers who find all servers and waiting positions (if any) occupied many retry for service after a period of time are retrial queues or queues with repeated attempts. This study deals with two objectives one is to introduce orbital search in retrial queueing models which allows to minimize the idle time of the server. If the holding costs and cost of using the search of customers will be introduced, the results we obtained can be used for the optimal tuning of the parameters of the search mechanism. The second one is to provide insight of the link between the corresponding retrial queue and the classical queue. At the end we observe that when the search probability Pj = 1 for all j, the model reduces to the classical queue and when Pj = 0 for all j, the model becomes the retrial queue. It discusses the performance evaluation of single-server retrial queue. It was determined by using Poisson process. Then it discuss the structure of the busy period and its analysis interms of Laplace transforms and also provides a direct method of evaluation for the first and second moments of the busy period. Then it discusses the M/ PH/1 retrial queue with disaster to the unit in service and orbital search, and a multi-server retrial queueing model (MAP/M/c) with search of customers from the orbit. MAP is convenient tool to model both renewal and non-renewal arrivals. Finally the present model deals with back and forth movement between classical queue and retrial queue. In this model when orbit size increases, retrial rate also correspondingly increases thereby reducing the idle time of the server between services |
| URI: | http://dyuthi.cusat.ac.in/purl/60 |
| Files | Size |
|---|---|
| Dyuthi-T0142.pdf | (5.426Mb) |
| Abstract: | The main objective of this thesis work is to optimize the growth conditions for obtaining crystalline and conducting Lao.5Sro.5Co03 (LSCO) and Lao.5Sro.5Coo.5.5Nio.5O3 (LSCNO) thin films at low processing temperatures. The films are prepared by radio frequency magnetron sputtering under various deposition conditions. The thin films were used as electrodes for the fabrication of ferroelectric capacitors using BaO.7SrO.3 Ti03 (BST) and PbZro.52 Tio.4803 (PZT). The structural and transport properties of the La1_xSrxCo03 and Lao.5Sro.5Co1_xNix03 are also investigated. The characterization of the bulk and the thin films were performed using different tools. A powder X-ray diffractometer was used to analyze the crystalline nature of the material. The transport properties were investigated by measuring the temperature dependence of resistivity using a four probe technique. The magnetoresistance and thermoelectric power were also used to investigate the transport properties. Atomic force microscope was used to study the surface morphology and thin film roughness. The ferroelectric properties of the capacitors were investigated using RT66A ferroelectric tester. |
| Description: | Department of Physics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2514 |
| Files | Size |
|---|---|
| Dyuthi-T0673.pdf | (8.465Mb) |
| Abstract: | This study deals with the salient features of the north Indian ocean associated with the summer monsoon. The focus is given on the Arabian sea mini warm pool, which is a part of the Indian ocean. It primarily study the certain aspects of the atmosphere and ocean variability in the north Indian ocean. The attempt were made to understand various aspects of time –scale variability of major features occurring in the Indian summer monsoon. The result from the thesis can be utilized as an input for model studies for prediction of monsoon, understanding ocean dynamics, radar tracking and ranging etc. |
| URI: | http://dyuthi.cusat.ac.in/purl/108 |
| Files | Size |
|---|---|
| Dyuthi-T0366.pdf | (21.14Mb) |
| Neema C P ,Dept.of Atmospheric Sciences,1328.PDF | (3.570Mb) |
| URI: | http://dyuthi.cusat.ac.in/purl/1723 |
| Files | Size |
|---|---|
| Dyuthi-T0155.pdf | (6.270Mb) |
| Abstract: | In the present investigation, an attempt is made to document various episodes of transgression and regression during the late Quaternary period from the study of coastal and shelf sequences extending from the inland across the beach to the shelf domain. Shore parallel beach ridges with alternating swales and occurrence of strand line deposits on the shelf make the northern Kerala coast an ideal natural laboratory for documenting the morpho-dynamic response of the coast to the changing sea level. The objectives of the study are lithographic reconstruction of environments of deposition from the coastal plain and shelf sequences; documentation of episodes of transgression and regression by studying different coastal plain sequences and shelf deposits and evolve a comprehensive picture of late Quaternary coastal evolution and sea level changes along the northern Kerala coast by collating morphological, lithological and geochronological evidences from the coastal plain and shelf sequences. The present study is confined to two shore-normal east-west trending transects, Viz. Punjavi and Onakkunnu, in the northern Kerala coast. |
| URI: | http://dyuthi.cusat.ac.in/purl/130 |
| Files | Size |
|---|---|
| Dyuthi-T0144.pdf | (9.307Mb) |
| URI: | http://dyuthi.cusat.ac.in/purl/5515 |
| Files | Size |
|---|---|
| Dyuthi T-2557.pdf | (29.81Mb) |
| Abstract: | Experimental Neutrino Physics is an active area of research in high energy physics. The investigation of the properties of this elusive particles has started since it’s discovery itself. In the standard model of particle physics, neutrinos are massless, the discovery of neutrino oscillation is the first evidence that demands the extensions of standard model. It is well established the existence of three active neutrinos, e, μ and , but recent experiments like LSND and MiniBooNE has found some anomalies in their data. These experimental data could not be explained using three flavour neutrino oscillation physics, but they could explain the anomaly by adding a fourth type neutrino called sterile neutrinos. The evidences obtained from these experiments are not yet conclusive. Search for sterile neutrino is an extensive research area in the field of neutrino physics. The main work presented in this thesis is a sterile neutrino search at MINOS (Main Injector Neutrino Oscillation Search) experiment at Fermilab, USA. MINOS is a two detector experiment at Fermilab, which studies the neutrinos produced at Fermilab Main Injector particle accelerator. MINOS Near Detector is situated at 1 km away from the source and the Far Detector is at Soudan Mine at Minnesota, 735 km away from the neutrino source. The experiment is built to study neutrino oscillation phenomena in the atmospheric sector and has made world class measurements on neutrino oscillation parameters. The MINOS experiment is also capable of looking for small perturbation in the energy spectra caused by any fourth type of neutrino and can extract the oscillation parameters. |
| URI: | http://dyuthi.cusat.ac.in/purl/5135 |
| Files | Size |
|---|---|
| Dyuthi-T2169.pdf | (7.459Mb) |
| Abstract: | The Sediment budgeting studies are done to bring out the coastal processes at work, to understand the beach-innershelf sedimentary dynamics and to assess the stability of any coastal stretch. There is a dearth of such studies as far as the Indian coast is concerned. The Chavara coast of Kollam district, Kerala, is world famous for its rich heavy mineral resources. These mineral resources are being commercially mined by the Indian Rare Earths Ltd. (IREL) and Kerala Minerals and Metals Ltd. (KMML), two Public Sector Undertakings located in the area. The impact of mining on stability of the beach has been a point of debate among the local people as well as researchers. The coastal stretch of 22km length from Neendakara to Kayamkulam which is referred to as the Chavara coast. The tidal, wind driven and continental shelf currents, there could also be the contribution of coastal trapped waves and baroclinic flow associated with the plumes of fresh water coming from the estuaries. The main objectives of the study are the hydrodynamic processes and mechanism involved in the sediment movement along the Chavara coast, Identify the different sources and sinks of beach sand along the coast, Quantify the sediment input/output into/from the coast and assess the erosion/accretion scenario of the coast. |
| URI: | http://dyuthi.cusat.ac.in/purl/938 |
| Files | Size |
|---|---|
| Dyuthi-T0147.pdf | (11.59Mb) |
| Abstract: | Chemistry occupies a unique middle position in the scientific arena, between physics and mathematics on the one side and biology, ecology, sociology and economics on the other [1]. Chemistry is the science of matter and of its transformations, and life is its highest expression [2]. According to reductionist thinking biology is reducible into chemistry, chemistry into physics, and ultimately physics into mathematics. Reductionism implies the ease of understanding one level in terms of another.The work presented this thesis comprises synthesis and characterization of suitably substituted thiocarbohydrazone and carbohydrazone ligand building blocks, self-assembled metallosupramolecular square grid complexes as well as some di/multinuclear complexes. The primary aim was the deliberate syntheses of some novel transition metal framework complexes, mainly metallosupramolecular coordination square grids by self-assembly and their physico-chemical characterization. The work presented, however, also include synthesis and characterization of four mononuclear Ni(II) complexes of two thiosemicarbazones, which we carried out as a preliminary and supporting study. Based on the present work we would like to conclude that the carbohydrazones, thiocarbohydrazones and their coordination framework complexes of transition metals are promising systems for wide application in science and technology varied from physics to biotechnology. Novel classes of materials and biologically important potential compounds open up further scope of researches and we hopefully welcome any sort of related research to make this work more valuable. |
| URI: | http://dyuthi.cusat.ac.in/purl/3016 |
| Files | Size |
|---|---|
| Dyuthi-T0995.pdf | (17.18Mb) |
| URI: | http://dyuthi.cusat.ac.in/purl/1667 |
| Files | Size |
|---|---|
| Dyuthi-T0149.pdf | (3.609Mb) |
| Description: | Department of Biotechnology, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2705 |
| Files | Size |
|---|---|
| Dyuthi-T0757.pdf | (12.27Mb) |
| Abstract: | Parkinson’s disease is a chronic progressive neurodegenerative disorder characterized by the selective loss of dopaminergic neurons in the SNpc resulting in severe motor impairments. Serotonergic system plays an important regulatory role in the pathophysiology of PD in rats, the evaluation of which provides valuable insight on the underlying mechanisms of motor, cognitive and memory deficits in PD. We observed a decrease in 5-HT content in the brain regions of 6-OHDA infused rat compared to control. The decreased 5-HT content resulted in a decrease of total 5-HT, 5-HT2A receptors and 5-HTT function and an increase of 5-HT2C receptor function. 5-HT receptor subtypes - 5-HT2A and 5-HT2C receptors have differential regulatory role on the modulation of DA neurotransmission in different brain regions during PD. Our observation of impaired serotonergic neurotransmission in SNpc, corpus striatum, cerebral cortex, hippocampus, cerebellum and brain stem demonstrate that although PD primarily results from neurodegeneration in the SNpc, the associated neurochemical changes in other areas of the brain significantly contributes to the different motor and non motor symptoms of PD. The antioxidant enzymes – SOD, CAT and GPx showed significant down regulation which indicates increased oxidative damage resulting in neurodegeneration. We also observed an increase in the level of lipid peroxidation. Reduced expression of anti-apoptotic Akt and enhanced expression of NF-B resulting from oxidative stress caused an activation of caspase-8 thus leading the cells to neurodegeneration by apoptosis. BMC administration in combination with 5-HT and GABA to PD rats showed reversal of the impaired serotonergic neurotransmission and oxidative stress mediated apoptosis. The transplanted BMC expressed NeuN confirming that 5-HT and GABA induced the differentiation and proliferation of BMC to neurons in the SNpc along with an increase in DA content and an enhanced expression of TH. Neurotrophic factors – BDNF and GDNF rendered neuroprotective effects accompanied by improvement in behavioural deficits indicating a significant reversal of altered dopaminergic and serotonergic neurotransmission in PD. The restorative and neuroprotective effects of BMC in combination with 5-HT and GABA are of immense therapeutic significance in the clinical management of PD. |
| Description: | Department of Biotechnology, Cochin University of Science and Technology, |
| URI: | http://dyuthi.cusat.ac.in/purl/3072 |
| Files | Size |
|---|---|
| Dyuthi-T1046.pdf | (27.87Mb) |
| URI: | http://dyuthi.cusat.ac.in/purl/1094 |
| Files | Size |
|---|---|
| Balakrishna Warrier,K 1982.pdf | (1.270Mb) |
| URI: | http://dyuthi.cusat.ac.in/purl/2138 |
| Files | Size |
|---|---|
| Dyuthi-T0499.pdf | (9.135Mb) |
| Abstract: | This thesis is mainly concerned with the synthesis and characterisation of new simple and zeolite encapsulated transition metal (manganese(II),nickel(II),and copper(II)complexes of quinoxaline based double Schiff base ligands.Theses ligands are N,N'-bis(quinoxaline-2-carboxalidene)hydrazine,N,N'-bis(quinoxaline-2-carboxalidene)-1,2-diaminoethane,N,N'-bis(quinoxaline-2-carboxalidene)-1,3-diamonopropane,N,N'-bis(quinoxaline-2-carboxalidene)-1,4-diaminobutane,N,N'-bis(quinoxaline-2-carboxalidene)-1,2-diaminocyclohexane and N,N'-bis(quinoxaline-2-carboxalidene)-1,2-diaminobenzene.The Schiff base ligands have been characterised by spectral and single crystal XRD studies.Theses ligands provide great structural diversity during complexation.Mn(II) and Ni(II) form octahedral with these Schiff bases,whereas Cu(II) forms both octahedral and tetrahedral complexes.Studies on the biological and Catalytic activity of the copper(ll) complexes are also presented in this thesis. |
| Description: | Dept.of Applied Chemistry,Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2936 |
| Files | Size |
|---|---|
| Dyuthi-T0927.pdf | (10.36Mb) |
Dyuthi Digital Repository Copyright © 2007-2011 Cochin University of Science and Technology. Items in Dyuthi are protected by copyright, with all rights reserved, unless otherwise indicated.