Department of Electrical Engineering

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The paper discusses the design aspects of capacitive RF MEMS Symmetric Toggle Switch (STS) with particular emphasis on device compactness, reliability, and improvement in isolation &amp; insertion loss by incorporating hafnium dioxide (HfO2) as a dielectric material. The major impact of the change from SiO2 to HfO2 having dielectric constant of 20, is the reduction in overall dimensions of the switch; capacitive overlap area is reduced by 75% leading to overall reduction of about 50%. Significant improvement in isolation (-43dB) and insertion loss (-0.014dB), at 11 GHz with 50 nm thick HfO2 as a dielectric layer compared to -29 dB and -0.016 dB @ 11 GHz respectively for SiO2 makes hafnium dioxide an attractive dielectric for RF micro-electro-mechanical systems (MEMS) switch for new generation of low-loss high-linearity microwave circuits.

World University root node

Nanotechnology 2010: Electronics, Devices, Fabrication, MEMS, Fluidics and Computational - Technical Proceedings of the 2010 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2010

Design of compact, high capacitance ratio MEMS switch for X - Band applications using high-k dielectric materials

Porous silicon based sensors were tested in the presence of various linear aliphatic alcohols (methanol to n-hexanol) and water in the range of 10-100 ppm by photoluminescence quenching technique. An increasing trend in the degree of quenching was observed with the chain length of alcohols while minimum response was given to water. Sensitivity as high as 80-90% and nearly instant response time has proven the sensors to be highly efficient. Photoluminescence quenching phenomena is discussed on the basis of charge transfer mechanism between the host and the vapour-induced surface states, but the degree of quenching and anomalous response as a function of chain length suggests no unique quenching theory for estimating the sensitivity for the set of alcohols tested. From methanol to butanol, the sensitivity was dependent on the effective concentration of analytes in the porous silicon matrix, while for pentanol and hexanol having high boiling point, the sensitivity was linked to dielectric quenching mechanism due to the condensation of vapours inside the pores.

Fulltext

International Journal on Smart Sensing and Intelligent Systems

Highly sensitive porous silicon sensor: Detection of organic vapours using photoluminescence quenching technique

This paper presents a new approach for integral sliding mode controller for a class of unmatched uncertain systems. A nominal control is computed using sliding mode techniques which works for unmatched uncertain system. Integral sliding mode is further added to ensure robust reaching phase. A control system for slosh-free motion of a partially filled liquid container is sought. This is representative of a broader class of systems to which the proposed methodology is applicable. A simple pendulum model is considered to represent a fundamental mode of the lateral slosh. The effectiveness of the proposed scheme is demonstrated by simulation results. © 2010 IEEE.

IECON Proceedings (Industrial Electronics Conference)

Robust control for slosh-free motion using sliding modes

Image quality assessment (IQA) is useful in many visual processing systems but challenging to perform in line with the human perception. A great deal of recent research effort has been directed towards IQA. In order to overcome the difficulty and infeasibility of subjective tests in many situations, the aim of such effort is to assess visual quality objectively towards better alignment with the perception of the Human Visual system (HVS). In this work, we review and analyze the recent progress in the areas related to IQA, as well as giving our views whenever possible. Following the recent trends, we discuss the engineering approach in more details, explore the related aspects for feature pooling, and present a case study with machine learning. © 2010 SPIE.

Proceedings of SPIE - The International Society for Optical Engineering

Perceptual image quality assessment: Recent progress and trends

Objective image quality estimation is useful in many visual processing systems, and is difficult to perform in line with the human perception. The challenge lies in formulating effective features and fusing them into a single number to predict the quality score. In this brief, we propose a new approach to address the problem, with the use of singular vectors out of singular value decomposition (SVD) as features for quantifying major structural information in images and then support vector regression (SVR) for automatic prediction of image quality. The feature selection with singular vectors is novel and general for gauging structural changes in images as a good representative of visual quality variations. The use of SVR exploits the advantages of machine learning with the ability to learn complex data patterns for an effective and generalized mapping of features into a desired score, in contrast with the oft-utilized feature pooling process in the existing image quality estimators; this is to overcome the difficulty of model parameter determination for such a system to emulate the related, complex human visual system (HVS) characteristics. Experiments conducted with three independent databases confirm the effectiveness of the proposed system in predicting image quality with better alignment with the HVS's perception than the relevant existing work. The tests with untrained distortions and databases further demonstrate the robustness of the system and the importance of the feature selection. © 2010 IEEE.

IEEE Transactions on Neural Networks

Objective image quality assessment based on support vector regression

The paper presents the mathematical modeling of the space-time kinetics phenomena in Advanced Heavy Water Reactor (AHWR), a 920 MW (thermal), vertical pressure tube type thorium based nuclear reactor. The physical dimensions and the internal feedback effects of the AHWR are such that it is susceptible to xenon induced spatial oscillations. For the study of spatial effects and design of suitable control strategy, the need for a suitable mathematical model which is not of a very large order arises. In this paper, a mathematical model of the reactor within the framework of nodal modeling is derived with the two group neutron diffusion equation as the basis. A linear model in standard state space form is formulated from the set of equations so obtained. It has been shown that comparison of linear system properties could be helpful in deciding upon an appropriate nodalization scheme and thus obtaining a reasonably accurate model. For validation, the transient response of the simplified model has been compared with those from a rigorous finite-difference model. © 2009 Elsevier Ltd. All rights reserved.

Annals of Nuclear Energy

Space-time kinetics modeling of Advanced Heavy Water Reactor for control studies

Sliding mode design based on Lyapunov matrices is proposed as roll autopilot for a tail controlled missile. The search of Lyapunov matrix for systems with unmatched uncertainties is formulated in terms of linear matrix inequality. The proposed scheme ensures robust roll position control even in the presence of large mismatched parametric uncertainties and external disturbances. The performance of roll autopilot design based on sliding mode technique is compared with the classical autopilot. The simulation results demonstrate that the sliding mode based roll autopilot maintains its performance over wide range of variation of parameters. © 2010 IEEE.

Proceedings of the 2010 11th International Workshop on Variable Structure Systems, VSS 2010

Design of roll autopilot for a tail controlled missile using sliding mode technique

The contact resistance in pentacene organic field-effect transistors (OFETs) is found to be significantly reduced by selectively doping the organic semiconductor region beneath the source/drain electrodes. A 10 nm co-evaporated (1:1 ratio) layer of molybdenum tris-[1,2-bis(trifluoromethyl)ethane-1,2-dithiolene] and pentacene was deposited under the metal electrodes for this purpose. The width-normalized contact resistance (varying channel lengths of 25-200 μm used for the study) in contact-doped devices was lowered significantly (0.5 kΩ-cm) in comparison to reference devices (3.4 kΩ-cm) in the accumulation regime (VGS = -30 V). Doping of the contacts did not affect the stability of the devices under continuous bias stress significantly. © 2010 Elsevier B.V. All rights reserved.

Organic Electronics

Pentacene organic field-effect transistors with doped electrode-semiconductor contacts

A sliding mode controller is proposed for an uncertain input-delay system to enhance performance. A nonlinear sliding surface is proposed to achieve better transient response for general uncertain discrete SISO linear systems with input delay. Both matched and unmatched perturbations are considered and ultimate boundedness of motion is proved. The step tracking problem is analysed. The proposed surface increases the damping ratio of the transformed system (delay free) as the output moves nearer to the setpoint. To simplify the surface design, a linear matrix inequality based tuning procedure is proposed. The control law is designed based on an equivalent control approach which guarantees one step reaching. The scheme is able to achieve low overshoot and low settling time simultaneously which is not possible with a linear sliding surface. Simulation results verify the effectiveness of the proposed nonlinear surface over different linear surfaces. © 2010 Taylor &amp; Francis.

International Journal of Control

A nonlinear sliding surface to improve performance of a discrete-time input-delay system

This paper presents a novel algorithm for enhancement of spatial resolution of images. The proposed algorithm estimates a Least square based predictor of lower order and interpolates the coefficients of higher order predictor. We have reduced the predictor order form p to (p-1) that results into a saving of computational power. The proposed algorithm is generic that can be used with most of the LS based interpolation algorithms reported in literature. We have shown that use of interpolated prediction coefficient causes insignificant loss in subjective as well as objective (PSNR) quality of the higher resolution (HR) image as compared with the PSNR obtained by the actual prediction coefficient and there is around 40% to 50% reduction in computational complexity. © 2010 IEEE.