Photochemical and Photophysical Studies of a Few Bischromophoric Systems

Department of Applied Chemistry, Cochin University of Science and Technology

BROADBAND WIDE COVERAGE UNIPLANAR ANTENNA

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.

Adoption of Technology-Enabled Banking Self-Services: Antecedents and Consequences

School of Management Studies, Cochin University of Science and Technology

EVANESCENT WAVE FIBRE OPTIC SENSORS: DESIGN, FABRICATION AND CHARACTERIZATION

International School of Photonics, Cochin University of Science and Technology

DEVELOPMENT AND ANLAYSIS OF BROADBAND L·STRIP FED MICROSTRIP ANTENNAS

The thesis is the outcome of the experimental and theoretical Investigations on novel feeding techniques for bandwidth enhancement of microstrip patches. The new feeding techniques provide bandwidth enhancement without deteriorating the radiation characteristics of the antenna. The antenna is analysed using finite Difference Time Domain (FDTD) method. The predicated results are compared with the experimental results and excellent agreement is observed. The results are also verified using IE3D simulation software. The antenna is suitable for personal and broadband communications.

Design. Fabrication and Characterization of Fiber Optic Sensors for Physical and Chemical Applications

Advent of lasers together with the advancement in fiber optics technology has revolutionized the sensor technology. Advancement in the telemetric applications of optical fiber based measurements is an added bonus. The present thesis describes variety of fiber based sensors using techniques like micro bending, long period grating and evanescent waves. Sensors to measure various physical and chemical parameters are described in this thesis.

Design Techniques for Sigmadelta based ADC for Wireless Applications

Analog-to digital Converters (ADC) have an important impact on the overall performance of signal processing system. This research is to explore efficient techniques for the design of sigma-delta ADC,specially for multi-standard wireless tranceivers. In particular, the aim is to develop novel models and algorithms to address this problem and to implement software tools which are avle to assist the designer's decisions in the system-level exploration phase. To this end, this thesis presents a framework of techniques to design sigma-delta analog to digital converters.A2-2-2 reconfigurable sigma-delta modulator is proposed which can meet the design specifications of the three wireless communication standards namely GSM,WCDMA and WLAN. A sigma-delta modulator design tool is developed using the Graphical User Interface Development Environment (GUIDE) In MATLAB.Genetic Algorithm(GA) based search method is introduced to find the optimum value of the scaling coefficients and to maximize the dynamic range in a sigma-delta modulator.

Characterization of Hydrothermally Annealed Low Temperature Bioactive Thin Film Coatings of Hydroxyapatite on TiAl6V4 Implant material

This thesis summarizes the results on the growth and characterisation of thin films of HA grown on TiAl6V4 (Ti) implant material at a lower substrate temperature by a combination of Pulsed laser deposition and a hydrothermal treatment to get sufficiently strong crystalline films suitable for orthopaedic applications. The comparison of the properties of the coated substrate has been made with other surface modification techniques like anodization and chemical etching. The in-vitro study has been conducted on the surface modified implants to assess its cell viability. A molecular level study has been conducted to analyze the adhesion mechanism of protein adhesion molecules on to HA coated implants.

Development and Analysis of a Drum-Shaped Compact Microstrip Antenna

The thesis is the outcome of the experimental and theoretical investigations on a new compact drum-shaped microstrip antenna. A new compact antenna suitable for personal communication system(PCS), Global position System(GPS) and array applications is developed and analysed. The generalised cavity model and spatial fourier transform technique are suitably modified for the analysis of the antenna. The predicted results are compared with experimental results and excellent agreement is observed. The experimental work done by the author in related fields are incorporated as three appendices in this thesis. A single feed dual frequency microstrip antenne is presented in appendix A.Appendix B describes a new broadband dual frequeny microstrip antenna. The bandwidth enhancement effect of microstrip antennas through dielectric resonator loading is demonstarted in Appendix C.

Development and Analysis of Microstrip Antennas For Dual Band Microwave Communication

The thesis explores the outcome of the exhaustive theoretical and experimental investigations performed on Octagonal Microstrip Antenna configurations. Development of the MATLAB TM backed 3D-Conformal Finite Difference Time Domain (CFDTD)Modeller for the numerical computation of the radiation characteristics of the antenna is the theme of the work. The predicted results are verified experimentally and by IE3D TM simulation. The influence of the patch dimensions,feed configurations,feed dimensions and feed positions upon the radiation performance of the antenna is studied in detail. Octagonal Microstrip Antenna configurations suitable for Mobile-Bluetooth application is dealt in detail. A simple design formula for the regular Octagonal geometry is also presented. A compact planar multi band antenna for GPS/DCS/2.4/5.8GHz WLAN application is included as appendix A. Planar near field measurement technique is explained in appendix B.

Development of a Technique for Estimating Rain Parameters from Rain Noise Measurements

The measurement of global precipitation is of great importance in climate modeling since the release of latent heat associated with tropical convection is one of the pricipal driving mechanisms of atmospheric circulation.Knowledge of the larger-scale precipitation field also has important potential applications in the generation of initial conditions for numerical weather prediction models Knowledge of the relationship between rainfall intensity and kinetic energy, and its variations in time and space is important for erosion prediction. Vegetation on earth also greatly depends on the total amount of rainfall as well as the drop size distribution (DSD) in rainfall.While methods using visible,infrared, and microwave radiometer data have been shown to yield useful estimates of precipitation, validation of these products for the open ocean has been hampered by the limited amount of surface rainfall measurements available for accurate assessement, especially for the tropical oceans.Surface rain fall measurements(often called the ground truth)are carried out by rain gauges working on various principles like weighing type,tipping bucket,capacitive type and so on.The acoustic technique is yet another promising method of rain parameter measurement that has many advantages. The basic principle of acoustic method is that the droplets falling in water produce underwater sound with distinct features, using which the rainfall parameters can be computed. The acoustic technique can also be used for developing a low cost and accurate device for automatic measurement of rainfall rate and kinetic energy of rain.especially suitable for telemetry applications. This technique can also be utilized to develop a low cost Disdrometer that finds application in rainfall analysis as well as in calibration of nozzles and sprinklers. This thesis is divided into the following 7 chapters, which describes the methodology adopted, the results obtained and the conclusions arrived at.

Investigations on the Distribution Characteristics of Heavy Metals in Squid (Loligo spp.) in Relation to Levels in Food Fishes from the West Coast of India with a Perspective on Seafood Safety

The present study entitled "Investigations on the Distribution Characteristics of Heavy Metals in Squid (Loligo spp.) in Relation to Levels in Food Fishes from the West Coast of India with a Perspective on Seafood Safety"attempts to establish the base line data on metal levels in squids along the west coast of India. The study is of great relevance in the present context when utmost importance is being given for producing wholesome seafoods especially in the export market with a perspective on seafood safety.The thesis presents a comprehensive account of the base line data on important heavy metals, viz., Hg, Cd, Pb, Cu, Zn, Fe, Mn Cr and Ni in the edible and non-edible body components of the most abundant Loligo species, viz., L. duvauceli caught along the west coast of India.

Design and Development of Fiber Optic Sensors for Trace Detection of Certain Environmental Pollutants

In recent years,photonics has emerged as an essential technology related to such diverse fields like laser technology,fiber optics,communication,optical signal processing,computing,entertainment,consumer electronics etc.Availabilities of semiconductor lasers and low loss fibers have also revolutionized the field of sensor technology including telemetry. There exist fiber optic sensors which are sensitive,reliable.light weight and accurate devices which find applications in wide range of areas like biomedicine,aviation,surgery,pollution monitoring etc.,apart from areas in basic sciences.The present thesis deals with the design,fabrication and characterization of a variety of cost effective and sensitive fiber optic sensors for the trace detetction of certain environment pollutants in air and water.The sensor design is carried out using the techniques like evanescent waves,micro bending and long period gratings.

Characterization of Selected Photonic Materials and Systems Using Photoacoustic Technique

The photoacoustic investigations carried out on different photonic materials are presented in this thesis. Photonic materials selected for the investigation are tape cast ceramics, muItilayer dielectric coatings, organic dye doped PVA films and PMMA matrix doped with dye mixtures. The studies are performed by the measurement of photoacoustic signal generated as a result of modulated cw laser irradiation of samples. The gas-microphone scheme is employed for the detection of photoacoustic signal. The different measurements reported here reveal the adaptability and utility of the PA technique for the characterization of photonic materials.Ceramics find applications in the field of microelectronics industry. Tape cast ceramics are the building blocks of many electronic components and certain ceramic tapes are used as thermal barriers. The thermal parameters of these tapes will not be the same as that of thin films of the same materials. Parameters are influenced by the presence of foreign bodies in the matrix and the sample preparation technique. Measurements are done on ceramic tapes of Zirconia, Zirconia-Alumina combination, barium titanate, barium tin titanate, silicon carbide, lead zirconate titanateil'Z'T) and lead magnesium niobate titanate(PMNPT). Various configurations viz. heat reflection geometry and heat transmission geometry of the photoacoustic technique have been used for the evaluation of different thermal parameters of the sample. Heat reflection geometry of the PA cell has been used for the evaluation of thermal effusivity and heat transmission geometry has been made use of in the evaluation of thermal diffusivity. From the thermal diffusivity and thermal effusivity values, thermal conductivity is also calculated. The calculated values are nearly the same as the values reported for pure materials. This shows the feasibility of photoacoustic technique for the thermal characterization of ceramic tapes.Organic dyes find applications as holographic recording medium and as active media for laser operations. Knowledge of the photochemical stability of the material is essential if it has to be used tor any of these applications. Mixing one dye with another can change the properties of the resulting system. Through careful mixing of the dyes in appropriate proportions and incorporating them in polymer matrices, media of required stability can be prepared. Investigations are carried out on Rhodamine 6GRhodamine B mixture doped PMMA samples. Addition of RhB in small amounts is found to stabilize Rh6G against photodegradation and addition of Rh6G into RhB increases the photosensitivity of the latter. The PA technique has been successfully employed for the monitoring of dye mixture doped PMMA sample. The same technique has been used for the monitoring of photodegradation ofa laser dye, cresyl violet doped polyvinyl alcohol also.Another important application of photoacoustic technique is in nondestructive evaluation of layered samples. Depth profiling capability of PA technique has been used for the non-destructive testing of multilayer dielectric films, which are highly reflecting in the wavelength range selected for investigations. Eventhough calculation of thickness of the film is not possible, number of layers present in the system can be found out using PA technique. The phase plot has clear step like discontinuities, the number of which coincides with the number of layers present in the multilayer stack. This shows the sensitivity of PA signal phase to boundaries in a layered structure. This aspect of PA signal can be utilized in non-destructive depth profiling of reflecting samples and for the identification of defects in layered structures.

Mocrostrip-Fed Compact Dual Band Planar Antenna

The thesis is the outcome of the theoretical and experimental investigations on mocrostrip-fed printed strip monopole antenna.Finite ground plane has been effectively utilized to excite a new resonance near the fundamental mode by introducing another extended strip from the ground plane,without affecting compactness.Further size reduction was achieved by carrying out folding analysis on dual strip antenna and a compact folded dual strip antenna has been designed.Design methodologies for both the compact dual band antennas are presented.The proposed antennas can be used for mobile and WLAN applications due to wide bandwidth,moderate gain and omnidirectional radiation coverage.