| Abstract: | The thesis deals with analysis of some Stochastic Inventory Models with Pooling/Retrial of Customers.. In the first model we analyze an (s,S) production Inventory system with retrial of customers. Arrival of customers from outside the system form a Poisson process. The inter production times are exponentially distributed with parameter µ. When inventory level reaches zero further arriving demands are sent to the orbit which has capacity M(<∞). Customers, who find the orbit full and inventory level at zero are lost to the system. Demands arising from the orbital customers are exponentially distributed with parameter γ. In the model-II we extend these results to perishable inventory system assuming that the life-time of each item follows exponential with parameter θ. The study deals with an (s,S) production inventory with service times and retrial of unsatisfied customers. Primary demands occur according to a Markovian Arrival Process(MAP). Consider an (s,S)-retrial inventory with service time in which primary demands occur according to a Batch Markovian Arrival Process (BMAP). The inventory is controlled by the (s,S) policy and (s,S) inventory system with service time. Primary demands occur according to Poissson process with parameter λ. The study concentrates two models. In the first model we analyze an (s,S) Inventory system with postponed demands where arrivals of demands form a Poisson process. In the second model, we extend our results to perishable inventory system assuming that the life-time of each item follows exponential distribution with parameter θ. Also it is assumed that when inventory level is zero the arriving demands choose to enter the pool with probability β and with complementary probability (1- β) it is lost for ever. Finally it analyze an (s,S) production inventory system with switching time. A lot of work is reported under the assumption that the switching time is negligible but this is not the case for several real life situation. |
| URI: | http://dyuthi.cusat.ac.in/purl/57 |
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| Dyuthi-T0009.pdf | (1.614Mb) |
| Abstract: | In this thesis we have presented several inventory models of utility. Of these inventory with retrial of unsatisfied demands and inventory with postponed work are quite recently introduced concepts, the latt~~ being introduced for the first time. Inventory with service time is relatively new with a handful of research work reported. The di lficuity encoLlntered in inventory with service, unlike the queueing process, is that even the simplest case needs a 2-dimensional process for its description. Only in certain specific cases we can introduce generating function • to solve for the system state distribution. However numerical procedures can be developed for solving these problem. |
| Description: | Department of Mathematics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/3824 |
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| Dyuthi-T1755.pdf | (2.141Mb) |
| URI: | http://dyuthi.cusat.ac.in/purl/1666 |
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| Dyuthi-T0013.pdf | (1.956Mb) |
| Abstract: | The thesis entitled Analysis of Some Stochastic Models in Inventories and Queues. This thesis is devoted to the study of some stochastic models in Inventories and Queues which are physically realizable, though complex. It contains a detailed analysis of the basic stochastic processes underlying these models. In this thesis, (s,S) inventory systems with nonidentically distributed interarrival demand times and random lead times, state dependent demands, varying ordering levels and perishable commodities with exponential life times have been studied. The queueing system of the type Ek/Ga,b/l with server vacations, service systems with single and batch services, queueing system with phase type arrival and service processes and finite capacity M/G/l queue when server going for vacation after serving a random number of customers are also analysed. The analogy between the queueing systems and inventory systems could be exploited in solving certain models. In vacation models, one important result is the stochastic decomposition property of the system size or waiting time. One can think of extending this to the transient case. In inventory theory, one can extend the present study to the case of multi-item, multi-echelon problems. The study of perishable inventory problem when the commodities have a general life time distribution would be a quite interesting problem. The analogy between the queueing systems and inventory systems could be exploited in solving certain models. |
| Description: | Department of Mathematics and Statistics Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/3244 |
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| Dyuthi-T1218.pdf | (4.503Mb) |
| Dyuthi-T1218.pdf | (4.503Mb) |
| Abstract: | The classical methods of analysing time series by Box-Jenkins approach assume that the observed series uctuates around changing levels with constant variance. That is, the time series is assumed to be of homoscedastic nature. However, the nancial time series exhibits the presence of heteroscedasticity in the sense that, it possesses non-constant conditional variance given the past observations. So, the analysis of nancial time series, requires the modelling of such variances, which may depend on some time dependent factors or its own past values. This lead to introduction of several classes of models to study the behaviour of nancial time series. See Taylor (1986), Tsay (2005), Rachev et al. (2007). The class of models, used to describe the evolution of conditional variances is referred to as stochastic volatility modelsThe stochastic models available to analyse the conditional variances, are based on either normal or log-normal distributions. One of the objectives of the present study is to explore the possibility of employing some non-Gaussian distributions to model the volatility sequences and then study the behaviour of the resulting return series. This lead us to work on the related problem of statistical inference, which is the main contribution of the thesis |
| Description: | Department of Statistics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/4732 |
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| Dyuthi-T1834.pdf | (3.550Mb) |
| Abstract: | Natural systems are inherently non linear. Recurrent behaviours are typical of natural systems. Recurrence is a fundamental property of non linear dynamical systems which can be exploited to characterize the system behaviour effectively. Cross recurrence based analysis of sensor signals from non linear dynamical system is presented in this thesis. The mutual dependency among relatively independent components of a system is referred as coupling. The analysis is done for a mechanically coupled system specifically designed for conducting experiment. Further, cross recurrence method is extended to the actual machining process in a lathe to characterize the chatter during turning. The result is verified by permutation entropy method. Conventional linear methods or models are incapable of capturing the critical and strange behaviours associated with the dynamical process. Hence any effective feature extraction methodologies should invariably gather information thorough nonlinear time series analysis. The sensor signals from the dynamical system normally contain noise and non stationarity. In an effort to get over these two issues to the maximum possible extent, this work adopts the cross recurrence quantification analysis (CRQA) methodology since it is found to be robust against noise and stationarity in the signals. The study reveals that the CRQA is capable of characterizing even weak coupling among system signals. It also divulges the dependence of certain CRQA variables like percent determinism, percent recurrence and entropy to chatter unambiguously. The surrogate data test shows that the results obtained by CRQA are the true properties of the temporal evolution of the dynamics and contain a degree of deterministic structure. The results are verified using permutation entropy (PE) to detect the onset of chatter from the time series. The present study ascertains that this CRP based methodology is capable of recognizing the transition from regular cutting to the chatter cutting irrespective of the machining parameters or work piece material. The results establish this methodology to be feasible for detection of chatter in metal cutting operation in a lathe. |
| Description: | Division of Mechanical Engineering,School of Engineering, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/3058 |
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| Dyuthi-T1032.pdf | (7.938Mb) |
| Abstract: | Occupational stress is becoming a major issue in both corporate and social agenda .In industrialized countries, there have been quite dramatic changes in the conditions at work, during the last decade ,caused by economic, social and technical development. As a consequence, the people today at work are exposed to high quantitative and qualitative demands as well as hard competition caused by global economy. A recent report says that ailments due to work related stress is likely to cost India’s exchequer around 72000 crores between 2009 and 2015. Though India is a fast developing country, it is yet to create facilities to mitigate the adverse effects of work stress, more over only little efforts have been made to assess the work related stress.In the absence of well defined standards to assess the work related stress in India, an attempt is made in this direction to develop the factors for the evaluation of work stress. Accordingly, with the help of existing literature and in consultation with the safety experts, seven factors for the evaluation of work stress is developed. An instrument ( Questionnaire) was developed using these seven factors for the evaluation of work stress .The validity , and unidimensionality of the questionnaire was ensured by confirmatory factor analysis. The reliability of the questionnaire was ensured before administration. While analyzing the relation ship between the variables, it is noted that no relationship exists between them, and hence the above factors are treated as independent factors/ variables for the purpose of research .Initially five profit making manufacturing industries, under public sector in the state of Kerala, were selected for the study. The influence of factors responsible for work stress is analyzed in these industries. These industries were classified in to two types, namely chemical and heavy engineering ,based on the product manufactured and work environment and the analysis is further carried out for these two categories.The variation of work stress with different age , designation and experience of the employees are analyzed by means of one-way ANOVA. Further three different type of modelling of work stress, namely factor modelling, structural equation modelling and multinomial logistic regression modelling was done to analyze the association of factors responsible for work stress. All these models are found equally good in predicting the work stress.The present study indicates that work stress exists among the employees in public sector industries in Kerala. Employees belonging to age group 40-45yrs and experience groups 15-20yrs had relatively higher work demand ,low job control, and low support at work. Low job control was noted among lower designation levels, particularly at the worker level in these industries. Hence the instrument developed using the seven factors namely demand, control, manager support, peer support, relationship, role and change can be effectively used for the evaluation of work stress in industries. |
| Description: | Division of Safety and Fire Engineering, School of Engineering, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2930 |
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| Dyuthi-T0921.pdf | (2.100Mb) |
| Abstract: | Submarine hull structure is a watertight envelope, under hydrostatic pressure when in operation. Stiffened cylindrical shells constitute the major portion of these submarine hulls and these thin shells under compression are susceptible to buckling failure. Normally loss of stability occurs at the limit point rather than at the bifurcation point and the stability analysis has to consider the change in geometry at each load step. Hence geometric nonlinear analysis of the shell forms becomes. a necessity. External hydrostatic pressure will follow the deformed configuration of the shell and hence follower force effect has to be accounted for. Computer codes have been developed based on all-cubic axisymmetric cylindrical shell finite element and discrete ring stiffener element for linear elastic, linear buckling and geometric nonIinear analysis of stiffened cylindrical shells. These analysis programs have the capability to treat hydrostatic pressure as a radial load and as a follower force. Analytical investigations are carried out on two attack submarine cylindrical hull models besides standard benchmark problems. In each case, the analysis has been carried out for interstiffener, interdeepframe and interbulkhead configurations. The shell stiffener attachment in each of this configuration has been represented by the simply supported-simply supported, clamped-clamped and fixed-fixed boundary conditions in this study. The results of the analytical investigations have been discussed and the observations and conclusions are described. Rotation restraint at the ends is influential for interstiffener and interbulkhead configurations and the significance of axial restraint becomes predominant in the interbulkhead configuration. The follower force effect of hydrostatic pressure is not significant in interstiffener and interdeepframe configurations where as it has very high detrimental effect on buckling pressure on interbulkhead configuration. The geometric nonlinear interbulkhead analysis incorporating follower force effect gives the critical value of buckling pressure and this analysis is recommended for the determination of collapse pressure of stiffened cylindrical submarine shells. |
| Description: | Dept.of Ship Technology,Cochin University of Science & Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2177 |
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| Dyuthi-T0526.pdf | (10.42Mb) |
| Abstract: | The study of simple chaotic maps for non-equilibrium processes in statistical physics has been one of the central themes in the theory of chaotic dynamical systems. Recently, many works have been carried out on deterministic diffusion in spatially extended one-dimensional maps This can be related to real physical systems such as Josephson junctions in the presence of microwave radiation and parametrically driven oscillators. Transport due to chaos is an important problem in Hamiltonian dynamics also. A recent approach is to evaluate the exact diffusion coefficient in terms of the periodic orbits of the system in the form of cycle expansions. But the fact is that the chaotic motion in such spatially extended maps has two complementary aspects- - diffusion and interrnittency. These are related to the time evolution of the probability density function which is approximately Gaussian by central limit theorem. It is noticed that the characteristic function method introduced by Fujisaka and his co-workers is a very powerful tool for analysing both these aspects of chaotic motion. The theory based on characteristic function actually provides a thermodynamic formalism for chaotic systems It can be applied to other types of chaos-induced diffusion also, such as the one arising in statistics of trajectory separation. It was noted that there is a close connection between cycle expansion technique and characteristic function method. It was found that this connection can be exploited to enhance the applicability of the cycle expansion technique. In this way, we found that cycle expansion can be used to analyse the probability density function in chaotic maps. In our research studies we have successfully applied the characteristic function method and cycle expansion technique for analysing some chaotic maps. We introduced in this connection, two classes of chaotic maps with variable shape by generalizing two types of maps well known in literature. |
| Description: | Department of Physics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/3534 |
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| Dyuthi-T1503.pdf | (1.455Mb) |
| Abstract: | HINDI |
| Description: | Depanment of Hindi, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/4815 |
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| Dyuthi-T1912.pdf | (3.416Mb) |
| Abstract: | Hindi |
| Description: | Department of Hindi, Cochin University of Science & Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/4864 |
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| Dyuthi-T1962.pdf | (5.792Mb) |
| Abstract: | HINDI |
| Description: | Department of Hindi Cochin University of Science & Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/4861 |
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| Dyuthi-T1959.pdf | (4.470Mb) |
| Abstract: | HINDI |
| Description: | Department of Hindi, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/4855 |
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| Dyuthi-T1953.pdf | (5.587Mb) |
| Abstract: | HINDI |
| Description: | DEPARTEMENT OF HINDI Cochin University of Science And Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/4847 |
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| Dyuthi-T1944.pdf | (4.070Mb) |
| Abstract: | HINDI |
| Description: | Department of Hindi, Cochin University of Science & Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/4835 |
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| Dyuthi-T1932.pdf | (5.066Mb) |
| Abstract: | HINDI |
| Description: | Department of Hindi, CUSAT |
| URI: | http://dyuthi.cusat.ac.in/purl/4811 |
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| Dyuthi-T1908.pdf | (7.025Mb) |
| URI: | http://dyuthi.cusat.ac.in/purl/4999 |
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| Dyuthi-T2068.pdf | (1.225Mb) |
| URI: | http://dyuthi.cusat.ac.in/purl/5410 |
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| Chapter-1.pdf | (572.7Kb) |
| Chapter-2.pdf | (559.8Kb) |
| Chapter-3.pdf | (538.4Kb) |
| Chapter-4.pdf | (514.9Kb) |
| Chapter-5.pdf | (497.2Kb) |
| Contents.pdf | (511.6Kb) |
| Sandarbh Grandhsooji.pdf | (445.2Kb) |
| Upasamhar.pdf | (426.4Kb) |
| Abstract: | ANN based long range forecast of Indian summer monsoon rainfall for the hydrological regions of India using ocean and atmosphere state parameters with improved accuracy,Trend analysis of SST, sub surface temperature of Indian Ocean and that of ISMR. 3. Prediction of extreme rainfall events using ANN. |
| URI: | http://dyuthi.cusat.ac.in/purl/5152 |
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| Dyuthi-T2186.pdf | (7.822Mb) |
| Abstract: | HINDI |
| Description: | DEPARTMENT OF HINDI,CUSAT |
| URI: | http://dyuthi.cusat.ac.in/purl/4827 |
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| Dyuthi-T1924.pdf | (37.54Mb) |
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