ETD at Indian Institute of Science
(529 recursos)
Repository of Theses and Dissertations of Indian Institute of Science, Bangalore, India. The repository has been developed to capture, disseminate and preserve research theses of Indian Institute of Science.
Mostrando recursos 1 - 20 de 26
1.
Studies on Solar Cell AC Parameters (Instrumentation, Measurements and Applications) - Kumar, R Anil
Photovoltaic (PV) conversion of solar energy appears to be one of the most promising ways of meeting the increasing energy demand. In space, photovoltaic power source is the only safe alternative. Conventional silicon solar cell technologies have seen several improvements and off late GaAs/Ge and multijunction solar cells are developed to improve conversion efficiency. Demand for higher power, smaller size, lesser weight and higher efficiency has necessitated the use of high frequency switching power conditioners, which requires a better understanding of the AC characteristics of the solar cell, especially its capacitance. Solar cell is large p-n junction diode, whose AC
parameters...
2.
A Digital Auto Correlation Spectrometer For Solar Burst Obsevations At Decameter Wavelengths - Chellasamy, E Ebenezer
This thesis reports the design, construction, and the initial results obtained from a digital spectrograph for observations of radio burst emission from the Sun. One of the distinct advantages of radio spectral studies of the Sun during events such as solar flares, coronal mass ejections (CMEs), etc. is that it gives a straight forward estimate of the speed of the outflowing material into the outer atmosphere of the Sun and subsequently the interplanetary medium. It is well known that in the solar atmosphere, the electron density and consequently the plasma frequency gradually decreases with increasing distance from the center. Therefore...
3.
ECR Assisted Deposition of Tin And Si3N4 Thin Films For Microelectronic Applications - Vargheese, K Deenamma
The broad theme of the present research investigation is Ion Assisted Deposition of thin films and its effect on the properties of thin films. Though this activity has been of interest to researchers for more than a decade, the development of different types of ion sources with control over the ion flux and energy, makes it a current topic of interest. Ion assisted deposition was successful in depositing thin films of many material with desired qualities, however, there are certain class of materials whose deposition has been rather difficult. This has mainly been attributed to higher energies and low ion...
4.
Measurement Of Solar Cell AC Parameters Using Impedance Spectroscopy - Anil Kumar, R
Photovoltaic (PV) conversion of solar energy appears to be one of the most promising ways of meeting the increasing future energy demand. In space, photovoltaic power source is the only alternative. The demand for higher power has necessitated the use of high speed switching charge controller and power conditioner. To design an efficient and reliable switching charge controller, the static (I-V) and dynamic (AC) characteristics of a solar cell need to be understood.
The AC parameters of a solar cell can be measured either by Frequency Domain technique or by Time Domain technique. In frequency domain technique, a small signal is...
5.
Optical Metrology:Techniques For The Measurement Of Optical Parameters - Rao, S Madhusudana
The work reported in this thesis has been carried out in the following two areas of Optical metrology:
1. Measurement and correction of prism angles
2. Measurement of refractive indices using a spectrograph.
The prism angles are conventionally tested by mechanical bevel protractors, autocol-limators (angle dekkors), simple interference techniques and interferometers.
All these methods have their own limitations either in accuracy or in terms of cost.
Mechanical methods are usually employed to measure the angles of prisms. Interference techniques and interferometers are also used but they need optically polished components. For both mechanical and simple interference methods of testing, it is essential to fabricate more...
6.
Studies On Surface Plasmon Resonance And Related Experimental Methods Using Fixed Plasmon Angle - Prabhu, G Radhakrishna
Surface plasmon waves are transverse magnetic electromagnetic waves propagating along a dielectric-metal interface. These waves can be excited by resonant absorption of electromagnetic radiation leading to surface plasmon resonance (SPR) at the interface. The resonance is characterised by a reduction in the intensity of the reflected light at the interface due to strong coupling of incident optical radiation to surface plasmons. This gives rise to a minimum at a sharply defined angle of incidence, referred to as SPR angle or plasmon angle. The phenomenon of SPR has been extensively used in the past to develop reflective type optical devices for...
7.
Development Of Point-Contact Surface Acoustic Wave Based Sensor System - Parmar, Biren Jagadish
Surface Acoustic Waves (SAW) fall under a special category of elastic waves that need a material medium to propagate. The energy of these waves is confined to a limited depth below the surface over which they propagate, and their amplitudes decay with increasing depth. As a consequence of their being a surface phenomenon, they are easily accessible for transduction. Due to this reason, a lot of research has been carried out in the area, which has resulted in two very popular applications of SAW - SAW devices and in Non-Destructive Testing and Evaluation.
A major restriction of SAW devices is that...
8.
Semi Conducting Metal Oxide Gas Sensors: Development And Related Instrumentation - Abhijith, N
A sensor is a technological device or biological organ that detects, or senses, a signal or physical condition and chemical compounds. Technological developments in the recent decades have brought along with it several environmental problems and human safety issues to the fore. In today's world, therefore, sensors, which detect toxic and inflammable chemicals quickly, are necessary. Gas sensors which form a subclass of chemical sensors have found extensive applications in process control industries and environmental monitoring.
The present thesis reports the attempt made in development of Zinc oxide thin film based gas sensors. ZnO is sensitive to many gases of interest...
9.
Resonant Excitation Of Ions In Paul Trap Mass Spectrometer - Sarurkar, Vikram A
A Paul trap mass spectrometer has a three-electrode geometry mass analyzer consisting of two identical end cap electrodes and a ring electrode. Traditionally, the two end cap electrodes are electrically grounded and an RF potential is applied to the central ring electrode to generate the "trapping field". Ions of the analyte sample are formed in situ by electron bombardment and mass analysis of the fragment ions is performed by mass selectively destabilizing the ions from the trap. The inhornogeneities present in the trapping field (introduced either by misalignment of the trap geometry or by applying a dipolar auxiliary excitation across...
10.
Pressure Sensor Development Using Hard Anodized Aluminum Diaphragm And Thin Film Strain Gauges - Rajendra, A
The sensor is a device that converts a form of energy concerning which the information is
sought, called the measurand, to a form (electrical) in which it can be usefully processed or interpreted. Sensors rely on physical or chemical phenomena and materials where those phenomena appear to be useful. Those phenomena may concern the material itself or its geometry. Hence, the major innovations in sensors come from new materials, new fabrication techniques or both.
Normally, thin film sensors are realized by depositing a sensing film on a suitable substrate. There could be many combination of metals and insulating materials being deposited depending...
11.
Nonlinear Dynamics Of Resonances In, And Ejection From Paul Traps - Rajanbabu, N
This thesis presents results of investigations that have been carried out to understand dynamics in nonlinear Paul trap mass spectrometers. Of the three problems that have been taken up for study in this thesis, the first concerns understanding early/delayed ejection of ions in mass selective boundary ejection experiments. The second looks at the differential resolution observed in forward and reverse scan resonance ejection experiments. The third study explores a coupled nonlinear resonance within the nominally stable region of trap operation.
The method of multiple scales has been to elucidate dynamics associated with early and delayed ejection of ions in mass selective...
12.
Gas Sensors - Micro-Heater Designs And Studies On Sensor Film Deposition - Singh, Inderjit
Current gas sensor technology, although meeting the minimum requirements in many instances, suffers for a number of limitations. Hence, there is currently a considerable volume of research being undertaken at many laboratories of different countries. In the past, all chemical sensors and catalyst were optimized empirically by a trial and error method. Today, however, systematic research and development is becoming increasingly important in order to improve sensors and to find new sensing principles. Obtaining a long term stable gas sensor with improved sensitivity, selectivity, and low cost for mass production passes through fundamental research and material characterization to build new...
13.
Ultrasound Assisted Optical Elastography For Measurement Of Mechanical Properties Of Soft Tissue Mimicking Phantoms - Usha Devi Amma, C
This work describes the development of an optical probe for measuring movement of tissue particles deep inside which are loaded by an ultrasound remote palpation device. The principle of the method is that ultrasound force which can be applied inside the tissue makes the tissue particles vibrate and this vibration phase-modulates the light intercepting the insoniified region which results in a modulated speckle intensity on detection outside the object. This speckle intensity modulation detected through the measured intensity autocorrelation is a measure of the vibration amplitude. Since the vibration amplitude is related to the local elastic properties of the medium,...
14.
Studies On The Effect Of Closed Loop Controls On The Stability Of High Repetition Rate Copper Vapour Laser Pumped Dye Laser - Saxena, Piyush
Copper vapour laser (CVL) pumped high repetition rate narrow bandwidth dye laser is an important source of tunable radiation. It finds numerous applications in spectroscopic investigations and selective material processing like atomic vapour laser isotope separation (AVLIS). Being wavelength selective in these applications stability of the output wavelength and bandwidth are extremely important. The stability of these parameters depend upon the refractive index fluctuation of the dye medium, due to pump beam induced temperature gradients, dye solution flow, and mechanical stability of optical components. Precise measurement of wavelength and bandwidth of a dye laser and control over parameters governing the...
15.
Property Modulation Of Zinc Oxide Through Doping - Kekuda, Dhananjaya
Semi conductors are of technological importance and attracted many of the re-searchers. ZnO belongs to the family of II-VI semiconductors and has material properties well suitable to UV light emitters, varistors, Schottky diodes, gas sensors, spintronics, ferroelectric devices and thin film transistors. It has been considered as a competitor to GaN, which belongs to the family of III-V semiconductors. This is due to the fact that ZnO of high quality can be deposited at lower growth temperatures than GaN, leading to the possibility of transparent junctions on less expensive substrates such as glass. This will lead to low-cost UV lasers...
16.
Gas Sensor-Studies On Sensor Film Deposition, ASIC Design And Testing - Bagga, Shobi
The widespread use of Liquid Petroleum Gas (LPG) for cooking and as fuel for automobile vehicles requires fast and selective detection of LPG to precisely measure the leakage of gas for preventing the occurrence of accidental explosions. The adoption of Micro-Electro-Mechanical-System (MEMS) technology for fabricating the gas sensor provides other potential advantages for sensing applications, which includes low power consumption, low fabrication cost, high quality, small size and reliability. MEMS based gas sensor requires a sensitive layer of oxide material like ZnO, SnO2, TiO2, Fe2O3, etc. The tin oxide material used in the present work changes its electrical properties, as...
17.
Studies On The Electrical Properties Of Titanium Dioxide Thin Film Dielectrics For Microelectronic Applications - Kurakula, Sidda Reddy
The scaling down of Complementary Metal Oxide Semiconductor (CMOS) transistors requires replacement of conventional silicon dioxide layer with higher dielectric constant (K) material for gate dielectric. In order to reduce the gate leakage current, and also to maximize gate capacitance, ‘high K’ gate oxide materials such as Al2O3, ZrO2, HfO2, Ta2O5, TiO2, Er2O3, La2O3, Pr2O3, Gd2O3, Y2O3, CeO2 etc. and some of their silicates such as ZrxSi1–xOy, HfxSi1–xOy, AlxZr1–xO2 etc. are under investigation.
A systematic consideration of the required properties of gate dielectrics indicates that the key guidelines for selecting an alternate gate dielectric are (a) permittivity, band gap and...
18.
Geometry Optimization Of Axially Symmetric Ion Traps - Tallapragada, Pavan K
This thesis presents numerical optimization of geometries of axially symmetric ion
trap mass analyzers. The motivation for this thesis is two fold. First is to demonstrate
how the automated scheme can be applied to achieve geometry parameters of axially
symmetric ion traps for a desired field configuration. Second is, through the
Geometries investigated in this thesis, to present practically achievable geometries for mass spectroscopists to use. Here the underlying thought has been to keep the design simple for ease of fabrication (with the possibility of miniaturization) and still ensure that the performance of these analyzers is similar to the stretched geometry Paul traps....
19.
Denoising And Inpainting Of Images : A Transform Domain Based Approach - Gupta, Pradeep Kumar
Many scientific data sets are contaminated by noise, either because of data acquisition process, or because of naturally occurring phenomena. A first step in analyzing such data sets is denoising, i.e., removing additive noise from a noisy image. For images, noise suppression is a delicate and a difficult task. A trade of between noise reduction and the preservation of actual image features has to be made in a way that enhances the relevant image content.
The beginning chapter in this thesis is introductory in nature and discusses the Popular denoising techniques in spatial and frequency domains. Wavelet transform has wide...
20.
Investigations On Topological Thresholds In Metal Doped Ternary Telluride Glasses - Manikandan, N
The ability to tune the properties over a wide range of values by changing the additives, composition, etc., has made chalcogenide glassy semiconductors, most interesting from both fundamental physics as well as technology point of view. In particular, the occurrence of the two network topological thresholds namely the Rigidity Percolation Threshold (RPT) and the Chemical Threshold (CT) and their influence on various properties of chalcogenide glasses have been of immense interest during the last three decades.
The Rigidity Percolation Threshold (also known as the Stiffness Threshold or Mechanical Threshold) corresponds to the composition at which the material transforms from a...
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