Electrical Engineering

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The light emission process from a p-n junction in the forward-bias region is slow to respond to modulation signals due to the indirect band structure of silicon. Experimental results for a reverse-bias region showing light modulation in the range of tens of gigahertz are observed for the first time. For such a light emitter, the limiting speed of light modulation is shown to be determined by the transit time of the minority carriers across the junction during the filament formation of breakdown currents, which has been demonstrated by simulation of the propagation of a shockwave-like pattern in the breakdown field. © 2004 IEEE.

(SoE) School of Engineering

World University root node

IEEE Electron Device Letters

High-speed light modulation in avalanche breakdown mode for Si diodes

In the present work, a surface acoustic wave (SAW) interdigital transducer (IDT) has been modeled as a resistance-inductance-capacitance (RLC) network. The model includes the effects of metal shorting and energy storage at metal discontinuities, as well as an arbitrary polarity sequence of fingers. A C ++ program generates the equivalent electrical circuit, which is directly simulated by Simulation Program with Integrated Circuit Emphasis (SPICE), a popular electrical circuit simulator. Simulations compare well with reported experimental results, validating the proposed model.

IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control

A circuit simulation compatible surface acoustic wave interdigital transducer macro-model

An electrical modelling and analysis is presented for thermal nondestructive evaluation of materials by stepped infrared thermography. A one-dimensional electrical analysis based on the Laplace transform technique of network-analysis and time delay in an RC ladder network is given for defect depth estimation. Defect depth is evaluated based on the time instants at which surface temperature evolution over the defect and nondefect regions of the material deviates from its constant initial slope, corresponding to the response of a semi-infinite material under similar conditions of step heating. The method is applicable even for three-dimensional geometries of materials having unknown thermal properties and variable surface emissivity. Experimental and simulated results validate the proposed method and give good estimation of defect depth, even under noisy conditions for a thermally anisotropic material and a nonflat bottom type of defect. © IEE, 2004.

IEE Proceedings: Science, Measurement and Technology

Electrical approach to defect depth estimation by stepped infrared thermography

In this paper, we propose FRID (Fuzzy-Rough Interactive Dichotomizes); a methodology for the induction of decision trees using rough set based measures to capture cognitive uncertainties inherent to databases. These measures are: 1) Fuzzy-roughness and 2) Fuzzy-rough entropy. Developed FRID algorithms have been initially applied to various real-world benchmark datasets, and experimentally compared with the three fuzzy decision tree generation algorithms reported so far. Simulation results confirm that the use of proposed strategy leads to smaller decision trees and as a result better generalization performance.

IEEE International Conference on Fuzzy Systems

FRID: Fuzzy-rough interactive dichotomizers

We consider the efficient initialization of structure and parameters of generalized Gaussian radial basis function (RBF) networks using fuzzy decision trees generated by fuzzy ID3 like induction algorithms. The initialization scheme is based on the proposed functional equivalence property of fuzzy decision trees and generalized Gaussian RBF networks. The resulting RBF network is compact, easy to induce, comprehensible, and has acceptable classification accuracy with stochastic gradient descent learning algorithm.

International journal of neural systems

On the structure and initial parameter identification of Gaussian RBF networks.

Today an average transmission line is loaded more heavily than ever before and this has given rise to serious problem of voltage instability. A noble method for power system voltage instability estimation and improvement using ANN is presented The method is based on the fan that reactive power injections at critical buses of the power system help to steer the system away from a developing voltage collapse. The location and quantum of reactive power support has been computed based on sensitivity. The sensitivity matrix is formulated by cascading the output/input sensitivity of multiplayer perceptron model with that of input features versus reactive power injections. The effectiveness of the proposed method is demonstrated on Ward-Hale 6-bus, IEEE14-bus and IEEE 30-bus test systems. The method can be effectively used to make the system secure against voltage collapse condition in system planning and on-line operation.

Journal of the Institution of Engineers (India): Electrical Engineering Division

Sensitivity based approach for voltage instability alleviation using ANN

Fabrication of Micro-Electro-Mechanical-System (MEMS) using bulk silicon micromachining technology and semiconductor power devices often requires wafer processing from both the front and the back side of the silicon wafer. While transferring patterns onto one side of the wafer using photolithography, it is a requirement to align these with respect to already-formed patterns on the other side of the wafer. In order to do this, very expensive infrared mask aligners are generally used, which enables "viewing" of the patterns on one side of the wafer from the other side for the purpose of accurate pattern registration. In the present paper, a new technique is presented for front-to-back alignment. In this technique, identical square-shaped patterns called a "reference frame", having sides greater than the wafer diameter, are created on both the mask plates and used for pattern transfer on the two sides of the wafer. The regular device patterns are placed within this reference frame using the corners of the square as origins of coordinates. The detailed procedure of mask design and wafer-to-mask alignment is described. The technique has been successfully used to form common MEMS structures such as diaphragm and cantilever beams. Copyright © 2004 American Scientific Publishers. All rights reserved.

Sensor Letters

A new technique of front-to-back alignment for MEMS

The phenomenon of light coalescence in Si light emitter during avalanche breakdown is investigated. DC stressing results in light coalescence for low values of current (<25 mA) with total light emission coming out of the junction remaining constant. However, DC stressing with large current values (>40 mA) do not show light coalescence. The light coalescence phenomenon can be reversed when emitters are subjected to higher levels of currents. The purpose of this paper is to explain the difference in light coalescence behavior for large and small values of DC excitations and the reversibility of the phenomenon using hydrogen migration model. © 2002 Elsevier Science Ltd. All rights reserved.

Solid-State Electronics

Reversible light coalescence phenomena of Si photo-emitters under stressing at low breakdown currents

Radiation induced leakage current in a variable-thickness SiO 2-on-Si structure (1.0-6.5 nm) is detected and characterized by a novel technique, time-dependent electric field-induced second-harmonic generation (EFISH). The role of second-harmonic generation (SHG) for in situ monitoring of the DC field across the oxide and its utility in understanding the dynamics of the carriers in response to their photo-injection is discussed. Plausible mechanisms responsible for radiation-induced leakage current through thin oxides are used to explain the experimental results.

IEEE Transactions on Nuclear Science

Contactless Ultra-Fast Laser Probing of Radiation-Induced Leakage Current in Ultra-Thin Oxides

Today an average transmission line is loaded more heavily than ever before and this has given rise to serious problem of voltage instability. A noble method for power system voltage instability estimation and improvement using ANN is presented. The method is based on the fact that reactive power injections at critical buses of the power system help to steer the system away from a developing voltage collapse. The location and quantum of reactive power support has been computed based on sensitivity. The sensitivity matrix is formulated by cascading the output/input sensitivity of multiplayer perceptron model with that of input features versus reactive power injections. The effectiveness of the proposed method is demonstrated on Ward-Hale 6-bus, IEEE 14-bus and IEEE 30-bus test systems. The method can be effectively used to make the system secure against voltage collapse condition in system planning and on-line operation. © 2003 Elsevier Science Ltd. All rights reserved.