Now showing items 1-20 of 334
Next Page| Abstract: | This is a sequel to our earlier work on the modulated logistic map. Here, we first show that the map comes under the universality class of Feigenbaum. We then give evidence for the fact that our model can generate strange attractors in the unit square for an uncountable number of parameter values in the range μ∞<μ<1. Numerical plots of the attractor for several values of μ are given and the self-similar structure is explicity shown in one case. The fractal and information dimensions of the attractors for many values of μ are shown to be greater than one and the variation in their structure is analysed using the two Lyapunov exponents of the system. Our results suggest that the map can be considered as an analogue of the logistic map in two dimensions and may be useful in describing certain higher dimensional chaotic phenomena. |
| URI: | http://dyuthi.cusat.ac.in/purl/2567 |
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| Dyuthi-P0126.pdf | (484.3Kb) |
| 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: | A laser produced plasma from the multielement solid target YBa2Cu3O7 is generated using 1.06 μm, 9 ns pulses from a Q-switched Nd:YAG laser in air at atmospheric pressure. A time resolved analysis of the profile of the 4554.03 Å resonance line emission from Ba II at various laser power densities has been carried out. It has been found that the line has a profile which is strongly self-reversed. It is also observed that at laser power densities equal to or exceeding 1.6×1011 W cm−2, a third peak begins to develop at the centre of the self-reversed profile and this has been interpreted as due to the anisotropic resonance scattering (fluorescence). The number densities of singly ionized barium ions evaluated from the width of the resonance line as a function of time delay with respect to the beginning of the laser pulse give typical values of the order of 1019 cm−3. The higher ion concentrations existing at smaller time delays are seen to decrease rapidly. The Ba II ions in the ground state resonantly absorb the radiation and this absorption is maximum around 120 ns after the laser pulse. |
| URI: | http://dyuthi.cusat.ac.in/purl/2592 |
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| Dyuthi-P0152.pdf | (408.7Kb) |
| Abstract: | Thermal lens signals in solutions of rhodamine B laser dye in methanol are measured using the dual beam pump-probe technique. The nature of variations of signal strength with concentration is found to be different for 514 and 488 nm Ar + laser excitations. However, both the pump wavelengths produce an oscillatory type variation of thermal lens signal amplitude with the concentration of the dye solution. Probable reasons for this peculiar behaviour (which is absent in the case of fluorescent intensity) are mentioned. |
| URI: | http://dyuthi.cusat.ac.in/purl/2450 |
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| Dyuthi-P0311.pdf | (267.4Kb) |
| Abstract: | Antimedian graphs are introduced as the graphs in which for every triple of vertices there exists a unique vertex x that maximizes the sum of the distances from x to the vertices of the triple. The Cartesian product of graphs is antimedian if and only if its factors are antimedian. It is proved that multiplying a non-antimedian vertex in an antimedian graph yields a larger antimedian graph. Thin even belts are introduced and proved to be antimedian. A characterization of antimedian trees is given that leads to a linear recognition algorithm. |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/2009 |
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| Antimedian graphs.pdf | (151.5Kb) |
| Abstract: | A simple method based on laser beam deflection to study the variation of diffusion coefficient with concentration in a solution is presented. When a properly fanned out laser beam is passed through a rectangular cell filled with solution having concentration gradient, the emergent beam traces out a curved pattern on a screen. By taking measurements on the pattern at different concentrations, the variation of diffusion coefficient with concentration can be determined. |
| URI: | http://dyuthi.cusat.ac.in/purl/2444 |
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| Dyuthi-P0305.pdf | (273.3Kb) |
| Abstract: | This research project explores the utilization of cardanol in various capacities for rubber processing. Cardanol is a phenol with a long side chain in the meta position of the benzene ring. It is obtained by the vacuum distillation of cashew Hut shell liquid (CNSL) which is a cheap agro-byproduct. In this study, the plasticizer property of cardanol was investigated in silica filled and HAF black filled NR, NBR, EPDM and CR by comparing cure characteristics and mechanical properties of vulcanizates containing conventional plasticizer with those containing cardanol as plasticizer. The co-activator, antioxidant and accelerator properties were investigated in gum samples of NR, NBR, EPDM and CR by comparing the properties of vulcanizates which contain conventional co-activator, antioxidant and accelerator with those in which each of them was replaced by cardanol. The general effectiveness of cardanol was investigated by determination of cure time , measurement of physical and mechanical properties, ageing studies, crosslink density, extractability, FTIR spectra, TGA etc.The results show that cardanol can be a substitute for aromatic oil in both silica filled and HAF black filled NR. Again, it can replace dioctyl phthalate in both silica filled and HAF black filled NBR. Similarly, cardanol Can replace naphthenic oil in silica filled as well as HAF black filled EPDM and CR. The cure characteristics and mechanical properties are comparable in all the eight cases. The co-activator property of cardanol is comparable to stearic acid in all the four rubbers. The cure characteristics and mechanical properties in this case are also comparable. The antioxidant ,property of cardanol is comparable to TQ in all the four rubbers. The antioxidant property of cardanol is comparable to TQ in all the four case of NBR and EPDM.The accelerator property of cardarlol is comparable with CBS in the case of NBR and EPDM. No accelerator property is observed in the case of NR. The accelerator property of cardanol in CR is not negligible when compared with TMTD. |
| Description: | Department of Polymer Science and Rubber Technology, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2550 |
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| Dyuthi-T0694.pdf | (10.18Mb) |
| URI: | http://dyuthi.cusat.ac.in/purl/2489 |
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| Dyuthi-P0276.pdf | (145.7Kb) |
| Abstract: | Neural Network has emerged as the topic of the day. The spectrum of its application is as wide as from ECG noise filtering to seismic data analysis and from elementary particle detection to electronic music composition. The focal point of the proposed work is an application of a massively parallel connectionist model network for detection of a sonar target. This task is segmented into: (i) generation of training patterns from sea noise that contains radiated noise of a target, for teaching the network;(ii) selection of suitable network topology and learning algorithm and (iii) training of the network and its subsequent testing where the network detects, in unknown patterns applied to it, the presence of the features it has already learned in. A three-layer perceptron using backpropagation learning is initially subjected to a recursive training with example patterns (derived from sea ambient noise with and without the radiated noise of a target). On every presentation, the error in the output of the network is propagated back and the weights and the bias associated with each neuron in the network are modified in proportion to this error measure. During this iterative process, the network converges and extracts the target features which get encoded into its generalized weights and biases.In every unknown pattern that the converged network subsequently confronts with, it searches for the features already learned and outputs an indication for their presence or absence. This capability for target detection is exhibited by the response of the network to various test patterns presented to it.Three network topologies are tried with two variants of backpropagation learning and a grading of the performance of each combination is subsequently made. |
| Description: | Department of Electronics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2119 |
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| Dyuthi-T0376.pdf | (2.751Mb) |
| Abstract: | We report enhanced back scattering in nanometer-sized ZnO colloids prepared in two different media, by different methods. The FWHM of the back scattered cone and hence the mean free path varied with concentration of ZnO as well as particle size. The Lorentzian profile of backscattered cone indicates the presence of coherence. |
| URI: | http://dyuthi.cusat.ac.in/purl/2587 |
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| Dyuthi-P0147.pdf | (255.6Kb) |
| Abstract: | Light-scattering experiments gained prominence as potential applications of quantum optics, nonlinear optics, and photon localization. The possibility of the realization of lasing action in random media has created much interest in the study of the coherent structure of the backscattered light from disordered media. Backscattering (BS) studies are carried out to analyze the possibilities of photon localization in colloidal silica. The scattering enhancement is best associated with the density of the scatterers. The width of the BS cone and, hence, the mean-free path is related to the concentration of the medium. The dependence of the photon wavelength on the possible characteristics of the scattering is presented. |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/2041 |
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| Backscattering of laser light...pdf | (179.0Kb) |
| Abstract: | ACCURATE sensing of vehicle position and attitude is still a very challenging problem in many mobile robot applications. The mobile robot vehicle applications must have some means of estimating where they are and in which direction they are heading. Many existing indoor positioning systems are limited in workspace and robustness because they require clear lines-of-sight or do not provide absolute, driftfree measurements.The research work presented in this dissertation provides a new approach to position and attitude sensing system designed specifically to meet the challenges of operation in a realistic, cluttered indoor environment, such as that of an office building, hospital, industrial or warehouse. This is accomplished by an innovative assembly of infrared LED source that restricts the spreading of the light intensity distribution confined to a sheet of light and is encoded with localization and traffic information. This Digital Infrared Sheet of Light Beacon (DISLiB) developed for mobile robot is a high resolution absolute localization system which is simple, fast, accurate and robust, without much of computational burden or significant processing. Most of the available beacon's performance in corridors and narrow passages are not satisfactory, whereas the performance of DISLiB is very encouraging in such situations. This research overcomes most of the inherent limitations of existing systems.The work further examines the odometric localization errors caused by over count readings of an optical encoder based odometric system in a mobile robot due to wheel-slippage and terrain irregularities. A simple and efficient method is investigated and realized using an FPGA for reducing the errors. The detection and correction is based on redundant encoder measurements. The method suggested relies on the fact that the wheel slippage or terrain irregularities cause more count readings from the encoder than what corresponds to the actual distance travelled by the vehicle.The application of encoded Digital Infrared Sheet of Light Beacon (DISLiB) system can be extended to intelligent control of the public transportation system. The system is capable of receiving traffic status input through a GSM (Global System Mobile) modem. The vehicles have infrared receivers and processors capable of decoding the information, and generating the audio and video messages to assist the driver. The thesis further examines the usefulness of the technique to assist the movement of differently-able (blind) persons in indoor or outdoor premises of his residence.The work addressed in this thesis suggests a new way forward in the development of autonomous robotics and guidance systems. However, this work can be easily extended to many other challenging domains, as well. |
| Description: | Department of Electronics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2483 |
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| Dyuthi-T0666.pdf | (13.00Mb) |
| Abstract: | Chaotic synchronization of two directly modulated semiconductor lasers with negative delayed optoelectronic feedback is investigated and this scheme is found to be useful for e±cient bidirectional communication between the lasers. A symmetric bidirec- tional coupling is identified as a suitable method for isochronal synchronization of such lasers. The optimum values of coupling and feedback strength that can provide maxi- mum quality of synchronization are identified. This method is successfully employed for encoding/decoding both analog and digital messages. The importance of a symmetric coupling is demonstrated by studying the variation of decoding efficiency with respect to asymmetric coupling. |
| URI: | http://dyuthi.cusat.ac.in/purl/2525 |
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| Dyuthi-P0100.pdf | (1.173Mb) |
| Abstract: | We have studied the bifurcation structure of the logistic map with a time dependant control parameter. By introducing a specific nonlinear variation for the parameter, we show that the bifurcation structure is modified qualitatively as well as quantitatively from the first bifurcation onwards. We have also computed the two Lyapunov exponents of the system and find that the modulated logistic map is less chaotic compared to the logistic map. |
| URI: | http://dyuthi.cusat.ac.in/purl/2562 |
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| Dyuthi-P0121.pdf | (521.1Kb) |
| Abstract: | Hydroxyapatite (HAp, Ca10(PO4)6(OH)2) bioceramic and chitosan (poly [( -1-4) D-glucosamine]) biopolymer show good biocompatibility in vivo. They have biological origin and show excellent interactions with microwave. Microwave study of HAp made using different drying techniques and their composites with chitosan in the ISM band is presented. Pastes are made using HAp and chitosan with different ratios of mixing. The dielectric properties of this composites match with that of human fat, collagen tissues. Some of the compositions exhibit dielectric property close to that of natural bone. This makes them more biocompatible and better substitutes for natural bone. Thus composite bioceramics can be considered as phantom model constituents for imaging purposes. Their dielectric properties prove that they are biocompatible. |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/2050 |
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| Biocompatibilit ... oxyapatite-chitosan....pdf | (306.1Kb) |
| Abstract: | The Present thesis deals with the numerical as well as experimental investigations conducted on the resonance and radiation characteristics of Drum shaped monopole antenna, Funnel shaped monopole antenna and the shorted coplanar antenna.An introduction to the over view of antennas, state of the art planar antenna technologies, different feeding techniques and introduction of coplanar waveguides have been discussed. |
| Description: | Department of Electronics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/1953 |
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| Dyuthi-T0382.pdf | (8.779Mb) |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/1986 |
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| Dyuthi-T0383.pdf | (4.776Mb) |
| URI: | http://dyuthi.cusat.ac.in/purl/2128 |
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| Dyuthi-T0488.pdf | (1.352Mb) |
| Abstract: | This paper is a review of the work done on the dynamics of modulated logistic systems. Three different problems are treated, viz, the modulated logistic map, the parametrically perturbed logistic map and the combination map obtained by combining two maps of the quadratic family. Many of the interesting features displayed by these systems are discussed. |
| URI: | http://dyuthi.cusat.ac.in/purl/2536 |
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| Dyuthi-P0111.pdf | (598.3Kb) |
| Abstract: | Chaotic dynamics of directly modulated semiconductor lasers have been studied extensively over the last two decades because of their application in secure optical communication. However, chaos is generally suppressed in such systems when the nonlinear gain reduction factor is above 0.01 which is very much smaller than the reported values in semiconductors like InGaAsP. In this paper we show that by giving an optoelectronic feedback with appropriate delay one can increase the range of the values of the gain reduction factor for which chaos can be observed. Numerical studies show that negative feedback is more efficient in producing chaotic dynamics. |
| URI: | http://dyuthi.cusat.ac.in/purl/2539 |
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| Dyuthi-P0114.pdf | (704.5Kb) |
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