B. Sheela Rani

Colour image segmentation using fuzzy clustering techniques and competitive neural network

This paper explains the task of segmenting any given colour image using fuzzy clustering algorithms and competitive neural network. The fuzzy clustering algorithms used are Fuzzy C means algorithm, Possibilistic Fuzzy C means. Image segmentation is the process of dividing the pixels into homogeneous classes or clusters so that items in the same class are as similar as possible and items in different classes are as dissimilar as possible. The most basic attribute for image segmentation is the luminance amplitude for a monochrome image and colour components for a colour image. Since there are more than 16 million colours available in any image and it is difficult to analyse the image on all of its colours, the likely colours are grouped together by means of image segmentation. For that purpose soft computing techniques namely Fuzzy C means algorithm (FCM), Possibilistic Fuzzy C means algorithm (PFCM) and competitive neural network (CNN) have been used. A self-estimation algorithm has been developed for determining the number of clusters. The images segmented by these three soft computing techniques are compared using image quality metrics: peak signal to noise ratio (PSNR) and compression ratio. The time taken for image segmentation is also used as a comparison parameter. The techniques have been tested with images of different size and resolution and the results obtained by CNN are proven to be better than the fuzzy clustering technique.

Isolation of Defects in Radiographic Weld Images with Wavelet Denoising Using Log-Gabor Filter

Radiography is one of the oldest and most widely used NDT methods for the detection of volumetric defects in welds and castings. Radiographic films are chosen to record the images, due to higher resolution and their flexible usability for any kind of job. When digitized any radiographic image is characterized by three parameters, viz., optical density, contrast, resolution. Of these parameters, resolution of the film depends on the film quality and geometrical unsharpness. The objective of presented work is to compare the radiographic film image acquired at three different resolutions and denoise those images using wavelet technique and to find out the best filter that furnishes the maximum details of the acquired radiographic image. The denoising operation is performed using non orthogonal log-gabor wavelet function. This paves way to decide the best filter to retrieve the information recorded in the radiographic weld images which in turn helps to locate the defects and its dimensions in the corresponding weld piece. Radiographic image offline scattered porosity defect that occurs in weld is taken for this work.

Electronic power supply design for Sathyabama University Nano Satellite

This paper presents the practical and theoretical design of the power supply unit (PSU) of the Sathyabama University Nano Satellite. The solar arrays are configured such that the cells of each side on the satellite are connected in series and the four sides are connected in parallel. This configuration has been chosen, because it was found that it is the best trade off between ease of maximum power point tracking(MPPT) and to improve the converter performance. The diodes protect the cells from conducting a reverse current. The battery charge controller acts as a central unit of the electronic subsystem, it takes care of charging the battery unit. It basically transfers power from solar panel to the battery at unregulated bus. The choice of battery configuration and capacity is calculated on the basis of orbital calculation. This battery is also responsible for voltage control of the intermediate power bus between the two converters. The batteries keep the average voltage in the range 6.0–8.4V. This is used to convert the intermediate bus voltage to 5v and 3.3v bus levels for the other subsystem. The simulation results of various converters are shown.

Attitude determination and control system of Sathyabamasat

A high-precision attitude determination and control of the sathyabama satellite is an essential task for the success of the whole mission. Satellite Attitude determination and control system is an integral part of any satellite. For satellites in LEO an interaction with the local geomagnetic field is an important means of controlling the attitude or orientation. Attitude estimation is highly nonlinear due to the inherent nonlinearity in rotational kinematics, satellite attitude dynamics, and the nature of information through sensors, such as magnetometers. For attitude control, actuators must be based primarily on space and weight minimization. It uses three magnetic torque coils which are oriented orthogonally to each other. This paper describes the attitude determination and control in a closed loop configuration.

Multi-scale wavelet algorithm based noise reduction in ultrasonic images at elevated temperatures

Time-of-Flight Diffraction (TOFD) is an advanced ultrasonic inspection technique best suited for inspection especially inservice wherein the focus is on detection of cracks and linear indications which can propagate during service. The technique is widely used in process industries and also in strategic sector like nuclear. In the case of ISI in nuclear industry, the main difficulties likely to arise during such inspection are the high temperature (during shut down) and the background radiation. With the advent of high temperature probes, this limitation can be overcome. However, a fundamental factor which still is a cause for concern is the degradation of the signal to noise ratio due to thermal noise. Experiments conducted by the authors reveal that the contrast of acquired TOFD Images reduces progressively with increasing temperatures. As the temperature increases beyond 373K, the noise makes interpretation of images difficult and thus possibility of linear defects getting missed out arise. It is well known that the wavelets can be effectively employed for denoising. Wavelets have also been applied in general for denoising UT signals. However, its application for UT signals from stainless steel and which is at high temperature has not been attempted so far. In this paper, we explore the innovative application of wavelet thresholding for denoising applications due to its greater flexibility. Analysis of the restored image indicate that the Symlets family with the suitable thresholding has Higher Peak Signal to Noise Ratio(PSNR) value than the Coiflets wavelet family.

Automated weld defect classification from ultrasonic signals using statistical moments on normal distribution curves of wavelet co-efficient

Ultrasonic Testing is a highly reliable Non-Destructive Testing Technique for weld defect characterization. Defects occur either high frequency components (Porosity, Sidewall crack) or as low frequency components (Root, Lack of Fusion, Lack of penetration, slag) in the UT signal. Manual interpretation of these signals is subjective in nature and is dependent on the expertise of the individual. Hence it is necessary to develop automated signal analysis system that classifies the defect. As defect classification is non-linear in nature, neural network based classification techniques are cited in literature. However neural network based techniques are computationally complex and has prediction error. Hence in this paper, an effective range based classification system using statistical moments is proposed. Performance of the proposed technique is measured in terms sensitivity and specificity.

On board communication subsystem for Sathyabama University nano-satellite

The primary goal of the communication subsystem of any satellite is to establish a communication link between the satellite and the ground station to relay payload and housekeeping data.[1] In this paper, various hardware and software design aspects of the Sathyabama nanosatellite communication subsystem is discussed. Hardware devices chosen for our design includes Microhard MHX-425 ultra low power FHSS radio transceiver, Beacon transmitter, Microchip dsPIC on board processor and monopole antennas. The software written for the dsPIC processor is responsible for encoding telemetry and payload information into standard AX.25 format data packets as well as decoding commands transmitted from the ground station.

A survey to select microcontroller for Sathyabama satellite's On Board Computer subsystem

Nanosatellite is the prime focus of many universities those who are interested in space technology. Nanosatellite is popular due to its feasibility and affordability. The primary mission of the Sathyabama nanosatellite is pollution monitoring and data communication to the earth station. For any satellite, On Board Computer (OBC) is considered to be the brain of the satellite. OBC must be designed in such a way that each subsystem should be controlled and monitored by the OBC of the satellite. It is a very important task to choose a microcontroller for OBC in order to make the Sathyabama nanosatellite efficient and powerful in all situations. In this paper, an extensive survey has been made on many international nanosatellites like CubeSat, TUBSAT-N and many national nanosatellites like STUDSAT, PRATHAM etc. to select a right microcontroller for our Sathyabama nanosatellite mission.

PERFORMANCE EVALUATION OF HOT SPOT EXTRACTION AND QUANTIFICATION ALGORITHMS FOR ON-LINE WELD MONITORING FROM WELD THERMOGRAPHS

The quality of welded steel structures play an important role in determining the reliability of a building. Weld quality is affected by Incomplete Penetration, which is a most commonly occurring defect in welds. An automated adaptive welding system if developed can correct the deviation in the welding current online so as to adjust the depth of Penetration to provide defect free welds. This system requires an on-line weld-monitoring sensor, efficient image processing algorithm for defect identification and neurofuzzy control software for correlating the defect characteristics with deviations in physical parameters. Infrared Thermography is the best-suited sensor for on-line weld monitoring and continuous assessment of welds. Incomplete penetration affects the hot spot of the thermograph and hence hot spot quantification describes the defect effectively. Three different algorithms namely conventional algorithm, region-growing algorithm and Euclidean distance based color image segmentation algorithm are developed for hot spot quantification. The paper compares the effectiveness and suitability of these algorithms for on-line weld monitoring.

Actualization of a phased array antenna utilizing digital beamforming

In this article we present a study in regards to the actualization of a phased array antenna utilizing digital beamforming. Digital beam forming comprises of the spatial permeation of a signal where the phase shifting, adding, and amplitude scaling are actualized digitally. The thought is to utilize a programmable and computational environment which forms a signal in the digital realm to supervise the dynamic phase shift among the antenna components in the array. Digital beamforming permits various appealing elements in the exhibitions of communication frameworks. The fundamental point of interest to be picked up from digital beamforming is enormously increased adaptability with no attendant deterioration in signal to-noise ratio (SNR).