Tina,Sebastian; Dr.Sudha Kartha,C; Dr.Vijayakumar, K P(Cochin University of Science & Technology, August , 2009)
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Abstract:
Aim of the present work was to automate CSP process, to deposit and
characterize CuInS2/In2S3 layers using this system and to fabricate devices using
these films.An automated spray system for the deposition of compound
semiconductor thin films was designed and developed so as to eliminate the manual
labour involved in spraying and facilitate standardization of the method. The system
was designed such that parameters like spray rate, movement of spray head, duration
of spray, temperature of substrate, pressure of carrier gas and height of the spray head
from the substrate could be varied. Using this system, binary, ternary as well as
quaternary films could be successfully deposited.The second part of the work deal with deposition and characterization of
CuInS2 and In2S3 layers respectively.In the case of CuInS2 absorbers, the effects of
different preparation conditions and post deposition treatments on the optoelectronic,
morphological and structural properties were investigated. It was observed
that preparation conditions and post deposition treatments played crucial role in controlling the properties of the films. The studies in this direction were useful in
understanding how the variation in spray parameters tailored the properties of the
absorber layer. These results were subsequently made use of in device fabrication
process.Effects of copper incorporation in
In2S3 films were investigated to find how the diffusion of Cu from CuInS2 to In2S3
will affect the properties at the junction. It was noticed that there was a regular
variation in the opto-electronic properties with increase in copper concentration.Devices were fabricated on ITO coated glass using CuInS2 as absorber and
In2S3 as buffer layer with silver as the top electrode. Stable devices could be
deposited over an area of 0.25 cm2, even though the efficiency obtained was not high.
Using manual spray system, we could achieve devices of area 0.01 cm2 only. Thus
automation helped in obtaining repeatable results over larger areas than those
obtained while using the manual unit. Silver diffusion on the cells before coating the
electrodes resulted in better collection of carriers.From this work it was seen CuInS2/In2S3 junction deposited through
automated spray process has potential to achieve high efficiencies.
Description:
Department of Physics,
Cochin University of Science and Technology
Jeevanand, E S; Dr.Unnikrishnan Nair, N(December 20, 1993)
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Abstract:
This thesis Entitled Bayesian inference in Exponential and pareto populations in the presence of outliers. The main theme of the present thesis is focussed on various estimation problems using the Bayesian appraoch, falling under the general category of accommodation procedures for analysing Pareto data containing outlier. In Chapter II. the problem of estimation of parameters in the classical Pareto distribution specified by the density function. In Chapter IV. we discuss the estimation of
(1.19) when the sample contain a known number of outliers under three different data generating mechanisms, viz. the exchangeable model. Chapter V the prediction of a future observation based on a random sample that contains one contaminant. Chapter VI is devoted to the study of estimation
problems concerning the exponential parameters under a k-outlier model.
Description:
Department of
Mathematics and Statistics, Cochin University of Science
and Technoloy
James, Kurian; Dr.Saseendran Pillai,P R(Cochin University of Science & Technology, October , 2008)
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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
Mathew, K T; Dr.Gopalakrishnan Nair, K(Cochin University of Science And Technology, May , 1978)
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Abstract:
In the present thesis, possibility of beam shaping of sectoral horns and corner reflector systems'has been studied in detail. The experimental results obtained in the above two cases are compared. As far as the flanged sectoral horns are concerned, the special advantage is that the gain is increased without impairing impedance conditions. An intense study on corner reflector antennas shows that the been broadening or focussing will be possible by adjusting parameters
involved. Beam tilting by imposing asymmetries is another interesting property of the systems. A comprehensive study of these fields has been presented in Chapter II. Chapter III is exclusively for describing the experimental techniques used in the present investigation.
In Chapter IV, experimental results on flanged sectoral horns and corner reflector eyetses are presented. A comparative analysis of the experimental results obtained with flanged sectoral horns and corner reflector systems is presented in the Chapter V. The similarity and close resemblance in each aspects are shown by presenting typical results from these two eysteee.
Theoretical aspects of both types of antennas are considered in Chapter VI. Attempts are made for co-ordinating the theoretical aspects and drawing a final conclusion. In Chapter VII. the final conclusion that the flanged sectoral horn may be considered as a corner reflector system has been drawn. The importance of the conclusions and usefulness are pointed out. The scope for further
work in these lines has been indicated.
Description:
Department of physics, Cochin University of Science And Technology
Joseph, Benny; Mathew, George(Cochin University Of Science And Technology, August 19, 2015)
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Abstract:
The research in the area of geopolymer is gaining momentum during the past 20 years. Studies confirm that geopolymer concrete has good compressive strength, tensile strength, flexural strength, modulus of elasticity and durability. These properties are comparable with OPC concrete.There are many occasions where concrete is exposed to elevated temperatures like fire exposure from thermal processor, exposure from furnaces, nuclear exposure, etc.. In such cases, understanding of the behaviour of concrete and structural members exposed to elevated temperatures is vital. Even though many research reports are available about the behaviour of OPC concrete at elevated temperatures, there is limited information available about the behaviour of geopolymer concrete after exposure to elevated temperatures. A preliminary study was carried out for the selection of a mix proportion. The important variable considered in the present study include alkali/fly ash ratio, percentage of total aggregate content, fine aggregate to total aggregate ratio, molarity of sodium hydroxide, sodium silicate to sodium hydroxide ratio, curing temperature and curing period. Influence of different variables on engineering properties of geopolymer concrete was investigated. The study on interface shear strength of reinforced and
unreinforced geopolymer concrete as well as OPC concrete was also carried out. Engineering properties of fly ash based geopolymer concrete after exposure to elevated temperatures (ambient to 800 °C) were studied and the corresponding results were compared with those of conventional concrete. Scanning Electron Microscope analysis, Fourier Transform Infrared analysis, X-ray powder Diffractometer analysis and Thermogravimetric analysis of geopolymer mortar or paste at ambient temperature and after exposure to elevated temperature were also carried out in the present research work. Experimental study was conducted on geopolymer concrete beams after exposure to elevated temperatures (ambient to 800 °C). Load deflection characteristics, ductility
and moment-curvature behaviour of the geopolymer concrete beams after exposure to elevated temperatures were investigated. Based on the present study, major conclusions derived could be summarized as follows.
There is a definite proportion for various ingredients to achieve maximum strength properties. Geopolymer concrete with total aggregate content of 70% by volume, ratio of fine aggregate to total aggregate of 0.35, NaOH molarity 10, Na2SiO3/NaOH ratio of 2.5 and alkali to fly ash ratio of 0.55 gave maximum compressive strength in the present study. An early strength development in geopolymer concrete could be achieved by the proper selection of curing temperature and the period of curing. With 24 hours of curing at 100 °C, 96.4% of the 28th day cube compressive strength could be achieved in 7 days in the present study. The interface shear strength of geopolymer concrete is lower to that of OPC concrete. Compared to OPC concrete, a reduction in the interface shear strength by 33% and 29% was observed for unreinforced and reinforced geopolymer specimens respectively. The interface shear strength of geopolymer concrete is lower than ordinary Portland cement concrete. The interface shear strength of geopolymer concrete can be approximately estimated as 50% of the value obtained based on the available equations for the calculation of interface shear strength of ordinary portland cement concrete (method used in Mattock and ACI). Fly ash based geopolymer concrete undergoes a high rate of strength loss (compressive strength, tensile strength and modulus of elasticity) during its early heating period (up to 200 °C) compared to OPC concrete. At a temperature exposure beyond 600 °C, the unreacted crystalline materials in geopolymer concrete get transformed into amorphous state and undergo polymerization. As a result, there is no further strength loss (compressive strength, tensile strength and modulus of elasticity) in geopolymer concrete, whereas, OPC concrete continues to lose its strength properties at a faster rate beyond a temperature exposure of 600 °C. At present no equation is available to predict the strength properties of geopolymer concrete after exposure to elevated temperatures. Based on the study carried out, new equations have been proposed to predict the residual strengths (cube compressive strength, split tensile strength and modulus of elasticity) of geopolymer concrete after exposure to elevated temperatures (upto 800 °C). These equations could be used for material modelling until better refined equations are available. Compared to OPC concrete, geopolymer concrete shows better resistance against surface cracking when exposed to elevated temperatures. In the present study, while OPC concrete started developing cracks at 400 °C, geopolymer concrete did not show any
visible cracks up to 600 °C and developed only minor cracks at an exposure temperatureof 800 °C. Geopolymer concrete beams develop crack at an early load stages if they are exposed to elevated temperatures. Even though the material strength of the geopolymer concrete does not decrease beyond 600 °C, the flexural strength of corresponding beam reduces rapidly after 600 °C temperature exposure, primarily due to the rapid loss of the strength of steel. With increase in temperature, the curvature at yield point of geopolymer concrete beam increases and thereby the ductility reduces. In the present study, compared to the ductility at ambient temperature, the ductility of geopolymer concrete beams reduces by 63.8% at 800 °C temperature exposure. Appropriate equations have been proposed to predict the service load crack width of geopolymer concrete beam exposed to elevated temperatures. These equations could be used to limit the service load on geopolymer concrete beams exposed to elevated temperatures (up to 800 °C) for a predefined crack width (between 0.1mm and 0.3 mm) or vice versa. The moment-curvature relationship of geopolymer concrete beams at ambient temperature is similar to that of RCC beams and this could be predicted using strain compatibility approach Once exposed to an elevated temperature, the strain compatibility approach underestimates the curvature of geopolymer concrete beams between the first cracking and yielding point.
Vigi V, Nair; Sankaranarayanan, K C(Cochin University Of Science And Technology, October , 2014)
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Abstract:
This study aims to analyze, compare and contrast the behavioral competency of officials in commercial banks headquartered in Kerala. This is done by analyzing the soft skills/behavioral skills possessed by an individual employee in both clerical and managerial levels and the means adopted to enhance their said skills in near future. The study was conducted with the objective of analyzing the behavioral competency of the managers and clerical staff in the commercial banks headquartered in Kerala. The researcher has gone through the available literature with respect to employee competency, job satisfaction and employee performance evaluation to formulate the problem and conceptualize the framework of the study. The study concluded that the competency of the employees differs from one bank to the other but strengthening the employees’ competency is the only possible solution by which the banks can determine their future growth prospects. Only through competency, banks can achieve high level of performance especially under the globalised situation.