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 37
1.
Task Scheduling Technlques for Distrlbuted/Parallel Processing Systems - Sreenivasan, C R
This dissertation discusses the principles, techniques and approaches adopted in the design of task scheduling algorithms for Distributed Parallel Processing Computer Systems (DPCSs) connected with network of front-end systems (FSs), The primary goal in the design of scheduling algorithms is to minimise the total turnaround time of the jobs to be scheduled by maximizing the utilisation of the resources of the DPCS with minimum data communication overhead, The users present their jobs to be scheduled at the FS, The FS receives a job and generates a finite set of independent tasks based on mutually independent sections having inherent parallelism, Each...
2.
Why only two ears? Some indicators from the study of source separation using two sensors - Joseph, Joby
In this thesis we develop algorithms for estimating broadband source signals from a mixture using only two sensors. This is motivated by what is known in the literature as cocktail party effect, the ability of human beings to listen to the desired source from a mixture of sources with at most two ears. Such a study lets us, achieve a better understanding of the auditory pathway in the brain and confirmation of the results from physiology and psychoacoustics, have a clue to search for an equivalent structure in the brain which corresponds to the modification which improves the algorithm, come...
3.
Clustering For Designing Error Correcting Codes - Joseph, Binoy
In this thesis we address the problem of designing codes for specific applications. To do so we make use of the relationship between clusters and codes. Designing a block code over any finite dimensional space may be thought of as forming the corresponding number of clusters over the particular dimensional space. In literature we have a number of algorithms available for clustering. We have examined the performance of a number of such algorithms, such as Linde-Buzo-Gray, Simulated Annealing, Simulated Annealing with Linde-Buzo-Gray, Deterministic Annealing, etc, for design of codes. But all these algorithms make use of the Eucledian squared error...
4.
A Hybrid Knowledge-Based System for Process Plant Fault Diagnosis - Pramanik, Saugata
Knowledge-Based Systems (KBSs) represent a relatively new programming approach and methodology that has evolved and is still evolving as an important sub-area of Artificial Intelligence (AI) research. The most prevalent application of KBSs, which emerged in recent times, has been various types of diagnosis and troubleshooting. KBS has an important role to play, particularly in fault diagnosis of process plants, which involve lot of challenges starting from commonly occurring malfunctions to rarely occurring emergency situations. The KBS approach is promising for this domain as it captures efficient problem-solving of experts, guides the human operator in rapid fault detection, explains the...
5.
Design and Development of a Hybrid TDMA/CDMA MAC Protocol for Multimedia Wireless Networks - D, Rajaveerappa
A wireless local area network (WLAN) provides high bandwidth to users in a limited geographical area. This network faces certain challenges and constraints that are not imposed on their wired counterparts. They are: frequency allocation, interference and reliability, security, power consumption, human safety, mobility, connection to wired LAN,service area, handoff and roaming, dynamic configuration and the throughput. But the
wireless medium relies heavily on the features of MAC protocol and the MAC protocol is the core of medium access control for WLANs. The available MAC protocols all have their own merits and demerits.
In our research works, we propose a hybrid MAC...
6.
A Study On Bandpassed Speech From The Point Of Intelligibility - Ganesh, Murthy C N S
Speech has been the subject of interest for a very long time. Even with so much advancement in the processing techniques and in the understanding of the source of speech, it is, even today, rather difficult to generate speech in the laboratory in all its aspects. A simple aspect like how the speech can retain its intelligibility even if it is distorted or band passed is not really understood. This thesis deals
with one small feature of speech viz., the intelligibility of speech is retained even when it is bandpassed with a minimum bandwidth of around 1 KHz located any where...
7.
Diffraction Tomographic Imaging With A Circular Array - Vasuki, A
In the conventional diffraction tomography a linear array is used to receive forward scattered field. Then a standard algorithm like back propagation or Fourier domain interpolation is used for reconstruction of the object. A circular array which captures both forward and backward scattered field has been proposed. A new theorem is proposed, which states that the scattered field measured with a large circular array surrounding the object is proportional to the Fourier transform of the object profile taken on the circumference of a circle of radius equa1 to the wave number and centered at (-k0 cosZO, -k0 sin Z0). The...
8.
Lambda Bipolar Transistor (LBT) in Static Random Access Memory Cell - Sarkar, Manju
With a view to reduce the number of components in a Static Random Access Memory (SRAM) cell, the feasibility of use of Lambda Bipolar Transistor (LBT)in the bistable element of the cell has been explored under the present study. The LBT under consideration here comprises of an enhancement mode MOSFET integrated with a parasitic bipolar transistor so as to perform as a negative resistance device. LBTs for the study have been fabricated and analysed. The devices have been shown to function at much lower voltage and current levels than those reported earlier/ and thus have been shown to be suitable...
9.
Methods for Blind Separation of Co-Channel BPSK Signals Arriving at an Antenna Array and Their Performance Analysis - Anand, K
Capacity improvement of Wireless Communication Systems is a very important area of current research. The goal is to increase the number of users supported by the system per unit bandwidth allotted. One important way of achieving this improvement is to use multiple antennas backed by intelligent signal processing. In this thesis, we present methods for blind separation of co-channel BPSK signals arriving at an antenna array. These methods consist of two parts, Constellation Estimation and Assignment. We give two methods for constellation estimation, the Smallest Distance Clustering and the Maximum Likelihood Estimation. While the latter is theoretically sound,the former is...
10.
Dynamic Dealy Compensation and Synchronisation Services for Continuous Media Streams - Shivaprasad, Mala A
Multimedia' nature of an application refers to the presence of several media streams in parallel. Whether it is receiving real-time data or retrieving stored data, there exists an end-to-end delay in data transfer from source to destination over the network. This delay experienced can be split into a fixed part and a variable part. Data processing time like coding and decoding at the source and destination are the fixed delays experienced. The variable delay occurs mainly due to queuing at the intermediate nodes during its flow through the network. The variable or unequal delays introduce gaps or discontinuities within a...
11.
Estimation Of Object Shape From Scattered Field - Buvaneswari, A
The scattered field from an object, when illuminated with ultrasound, is useful in
the reconstruction of it's cross section - a problem broadly classified as 'tomography'. In
many situations of medical imaging, we will be interested in getting to know the location
and the extent of growth of the inhomogeneity. The Maximum Likelihood (ML) estimation of the location and the shape parameters (of scale and orientation angle), has been done along with the corresponding CR bounds, for the case of weakly scattering objects, where the Fourier Diffraction Theorem(FDT) holds. It has been found that the a-priori information of a reference object function helps...
12.
Performance Analysis Of A Variation Of The Distributed Queueing Access Protocol - Gautam, S Vijay
"A distributed queueing Medium Access Control (MAC) protocol is used in Distributed Queue Dual Bus (DQDB) networks. A modified version of the MAC protocol was proposed by R.R. Pillai and U. Mukherji in an attempt to overcome some of the shortcomings of the DQDB MAC protocol. They analyzed the performance of the system for Bernoulli arrivals and for large propagation delays between the nodes. We extend the performance analysis of the modified MAC protocol for a DQDB type of Network. The parameter of interest to us is the bus access delay. This has two components, viz., the request bus access...
13.
Modelling And Analysis Of Event Message Flows In Distributed Discrete Event Simulators Of Queueing Networks - Shorey, Rajeev
Distributed Discrete Event Simulation (DDES) has received much attention in recent years, owing to the fact that uniprocessor based serial simulations may require excessive amount of simulation time and computational resources. It is therefore natural to attempt to use multiple processors to exploit the inherent parallelism in discrete event simulations in order to speed up the simulation process.
In this dissertation we study the performance of distributed simulation of queueing networks, by analysing queueing models of message flows in distributed discrete event simulators. Most of the prior work in distributed discrete event simulation can be categorized as either empirical studies or...
14.
Phase Sensitive Estimation Of Fluorescence Lifetime For Fiber Optic Biosensors - Vadde, Venkatesh
Fluorescence lifetime determination and allied studies find application in spectroscopy in general and fiber optic biosensors in particular. Instruments and sensors cited in literature however use open loop, intensity based techniques with sophisticated detectors and components. We propose phase sensitive signal processing schemes to estimate the fluorescence lifetime using simple detectors and components, without compromising on accuracy. The performance of the schemes proposed is analysed and contrasted from a communications (signals and systems) point of view.
The resolution and sensitivity limits imposed in processing the signal, by systematic errors and additive noise, are derived for the schemes suggested. It is found...
15.
Speech Encryption Using Wavelet Packets - Bopardikar, Ajit S
The aim of speech scrambling algorithms is to transform clear speech into an unintelligible signal so that it is difficult to decrypt it in the absence of the key.
Most of the existing speech scrambling algorithms tend to retain considerable residual intelligibility in the scrambled speech and are easy to break. Typically, a speech scrambling algorithm involves permutation of speech segments in time, frequency or time-frequency domain or permutation of transform coefficients of each speech block. The time-frequency algorithms have given very low residual intelligibility and have attracted much attention.
We first study the uniform filter bank based time-frequency scrambling algorithm with...
16.
Studies on Amorphous Silicon Thin Films Doped with Aluminium - Ho, Kang Jin
Amorphous Silicon(a-Si) films have attracted the attention of several investigators as it is an economical material for devices. One of the problems that is addressed is the doping of these films after they are prepared.
In this thesis, we investigated the effects of doping amorphous Silicon films(prepared by r.f. sputtering) with Aluminium(Al) by thermal diffusion. Amorphous Silicon films have been prepared on glass substrates at optimal process parameters. Then, the a-Si films are coated with Al by vacuum evaporation and subjected to heating in N2 atmosphere in the temperature range 300°C to 600°C for different durations.
After etching Al layer, it has...
17.
DSP Techniques for Performance Enhancement of Digital Hearing Aid - Udayashankara, V
Hearing impairment is the number one chronic disability affecting people in the world. Many people have great difficulty in understanding speech with background noise. This is especially true for a large number of elderly people and the sensorineural impaired persons. Several investigations on speech intelligibility have demonstrated that subjects with sensorineural loss may need a 5-15 dB higher signal-to-noise ratio than the normal hearing subjects. While most defects in transmission chain up to cochlea can nowadays be successfully rehabilitated by means of surgery, the great majority of the remaining inoperable cases are sensorineural hearing impaired, Recent statistics of the hearing...
18.
Synthesis of Arbitrary Antenna Arrays - Nagesh, S R
Design of antenna arrays for present day requirements has to take into account both mechanical and electrical aspects. Mechanical aspects demand the antennas to have low profile, non-protruding structures, structures compatible to aerodynamic requirements and so on. Electrical aspects may introduce several constraints either due to. technical reasons or due to readability conditions in practice. Thus, arrays of modern requirements may not fall into the category of linear or planar arrays. Further, due to the nearby environment, the elements will generate complicated individual patterns. These issues necessitate the analysis and synthesis of antenna arrays which are arbitrary as far as...
19.
Optimal Control Problems In Communication Networks With Information Delays And Quality Of Service Constraints - Kuri, Joy
In this thesis, we consider optimal control problems arising in high-speed integrated communication networks with Quality of Service (QOS) constraints. Integrated networks are expected to carry a large variety of traffic sources with widely varying traffic characteristics and performance requirements. Broadly, the traffic sources fall into two categories: (a) real-time sources with specified performance criteria, like small end to end delay and loss probability (sources of this type are referred to as Type 1 sources below), and (b) sources that do not have stringent performance criteria and do not demand performance guarantees from the network - the so-called Best Effort...
20.
Electrical Properties Of Diamond Like Carbon Films In Metal-Carbon-Silicon (MCS) Structure - Reddy, K Siva Sankara
Amorphous carbon film with Diamond like properties is the subject of intense interest in the past one and half decade. The unusual properties of these diamond like carbon films arise from the preponderance of SP3 tetrahedral bonding of carbon in the film. Depending on the processing technique and the processing conditions used, the structure of the films can range from amorphous carbon to large grain polycrystalline diamond. These deposited amorphous carbon films, which are smooth, may find their use in optoelectronics, in dielectric films and in microelectronics. These films are found to be chemically inhomogeneous(containing SP3 hybridized carbon in a...
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