Studies on the Vertical Structure of Horizontal Wind Variability in the Surface Boundary Layer Over Sriharikota

The present study on the vertical structure of horizontal wind variability in the surface boundary layer over Sriharikota. Based on clock wind speed and direction measuring meteorological tower facility from seven levels in the 100 m layer. The study on wind variability and elliptical approximation of wind hodographs investigated for this tropical coastal station established that Sriharikota is of meso-scale weather entity. Wind variability ratio increases from lower levels to upper levels. In South West monsoon months the station is of high ratio values and it gets affected with meso-scale weather features like thunderstorms. Average total shears are observed greater values than scalar shears. Scalar shears are high in the lowest shear levels compared to upper levels. Semi diurnal types of oscillation in average total shears are found in south west monsoon months. During cyclonic storm passage it is observed that there can be significant difference in mean wind speed from 10 m to 100 m level, but it is not so for peak wind speeds. The variations in wind variability ratio in different months is clearly depicted its strong link to define meso-scale or synoptic –scale forcing domination for this station. Meso-scale forcing is characterized by diurnal wind variability and synoptic- scale forcing by interdiurnal wind variability.

On Implementing Joins, Aggregates and Universal Quantifier in Temporal Databases using SQL Standards

A feasible way of implementing a temporal database is by mapping temporal data model onto a conventional data model followed by a commercial database management system. Even though extensions were proposed to standard SQL for supporting temporal databases, such proposals have not yet come across standardization processes. This paper attempts to implement database operators such as aggregates and universal quantifier for temporal databases, implemented on top of relational database systems, using currently available SQL standards.

A Cryptosystem Using the Concepts of Algebraic Geometric Code

Cryptosystem using linear codes was developed in 1978 by Mc-Eliece. Later in 1985 Niederreiter and others developed a modified version of cryptosystem using concepts of linear codes. But these systems were not used frequently because of its larger key size. In this study we were designing a cryptosystem using the concepts of algebraic geometric codes with smaller key size. Error detection and correction can be done efficiently by simple decoding methods using the cryptosystem developed. Approach: Algebraic geometric codes are codes, generated using curves. The cryptosystem use basic concepts of elliptic curves cryptography and generator matrix. Decrypted information takes the form of a repetition code. Due to this complexity of decoding procedure is reduced. Error detection and correction can be carried out efficiently by solving a simple system of linear equations, there by imposing the concepts of security along with error detection and correction. Results: Implementation of the algorithm is done on MATLAB and comparative analysis is also done on various parameters of the system. Attacks are common to all cryptosystems. But by securely choosing curve, field and representation of elements in field, we can overcome the attacks and a stable system can be generated. Conclusion: The algorithm defined here protects the information from an intruder and also from the error in communication channel by efficient error correction methods.

NANO - ZINC OXIDE: A Novel Modifier for Thermoplastics

Various synthesis routes have been developed in recent years for the preparation of nanoparticles. One of those methods is polymer induced crystallization. The first objective of the present work was to prepare nano ZnO powder by polymer induced crystallization in chitosan solution and to characterize the material using different techniques like TEM, SEM, XRD, FTLR, UV spectroscopy, TGA, DSC etc.The second object of the study is to prepare composites using nano ZnO. It has been undertaken to explore the potential of nano ZnO as reinforcement in engineering as well as commodity thermoplastics to widen their application spectra. We selected three engineering thermoplastics like [poly ethylene terephthalate, polyamide 6, and polycarbonate] and three commodity plastics like [polypropylene, high density polyethylene, and polystyrene] for the study. To date one of the few disadvantages associated with nanoparticle incorporation has concerned toughness and impact performance. Modification of polymers could reduce impact performance. The present study also focused on whether nano ZnO can act as a modifier for thennoplastics, without sacrificing their impact strength.

Aqueous Sol-gel Process for Nanocrystalline Photocatalytic Titania, Transparent Functional Coatings and Ceramic Membrane

The present thesis develops from the point of view of titania sol-gel chemistry and an attempt is made to address the modification of the process for better photoactive titania by selective doping and also demonstration of utilization of the process for the preparation of supported membranes and self cleaning films.A general introduction to nanomaterials, nanocrystalline titania and sol-gel chemistry are presented in the first chapter. A brief and updated literature review on sol-gel titania, with special emphasis on catalytic and photocatalytic properties and anatase to rutile transformation are covered. Based on critical assessment of the reported information the present research problem has been defined.The second chapter describes a new aqueous sol-gel method for the preparation of nanocrystalline titania using titanyl sulphate as precursor. This approach is novel since no earlier work has been reported in the same lines proposed here. The sol-gel process has been followed at each step using particle size, zeta potential measurements on the sol and thermal analysis of the resultant gel. The prepared powders were then characterized using X-ray diffraction, FTIR, BET surface area analysis and transmission electron microscopy.The third chapter presents a detailed discussion on the physico-chemical characterization of the aqueous sol-gel derived doped titania. The effect of dopants such as tantalum, gadolinium and ytterbium on the anatase to rutile phase transformation, surface area as well as their influence on photoactivity is also included. The fourth chapter demonstrates application of the aqueous sol-gel method in developing titania coatings on porous alumina substrates for controlling the poresize for use as membrane elements in ultrafiltration. Thin coatings having ~50 nm thickness and transparency of ~90% developed on glass surface were tested successfully for self cleaning applications.

Studies on the Commercially Important Fishing Gears of Vembanad Lake

Department of Industrial Fisheries, Cochin University of Science and Technology

Biology of Decapod crustaceans in different environmental conditions

This thesis Entitled Biology of Decapod crustaceans in different Environmental conditions. Prawn culture is practiced in Kerala in two types of fields namely seasonal and perennial; In seasonal fields paddy is grown during the monsoon period and prawns are cultured during the rest of the year. when compared to seasonal fields; perennial fields are subjected to much fluctuations in its environmental characteristics. The perennial fields were found more productive than seasonal fields. The benthic production in perronial fields were almost double that of seasonal fields. But in the matter of species diversity both fields were equal. Seasonal changes were observéd in the species abundance of benthic organisms in both the seasonal and perennial fields. Both isometric and allometric growth were noticed in P. indicus .But during most of the months the growth was near to isometric. The condition of the prawn also fluctuated between better and poor.During most of the months the prawn in perennial fields wore in good condition while in the seasonal fields the condition changed from year to year. This indicates that the perennial field provides a better habitat for P. indicus.