Ghulam Ishaq Khan Institute of Engineering Sciences and Technology

About: Ghulam Ishaq Khan Institute of Engineering Sciences and Technology is a education organization based out in Topi, Pakistan. It is known for research contribution in the topics: Thin film & Quantum efficiency. The organization has 618 authors who have published 940 publications receiving 10674 citations.

A Review of TiNiPdCu Alloy System for High Temperature Shape Memory Applications

Abstract: High temperature shape memory alloys (HTSMAs) are important smart materials and possess a significant potential to improve many engineering systems. Many TiNi-based high temperature ternary alloy systems have been reported in literature including TiNiPd, TiNiPt, TiNiZr, TiNiAu, TiNiHf, etc. Some quaternary additions of certain elements in the above systems have been successful to further improve many important shape memory and mechanical properties. The success criteria for an HTSMA become strict in terms of its cyclic stability, maximum recoverable strain, creep resistance, and corrosion resistance at high temperatures. TiNiPdCu alloy system has been recently proposed as a promising HTSMA. Unique nanoscaled precipitates formed in TiNiPdCu-based HTSMAs are found to be stable at temperatures above 773 K, while keeping the benefits of ease of fabrication. It is expected that this alloy system possesses significant potential especially for the high temperature shape memory applications. Till now many research reports have been published on this alloy system. In the present work, a comprehensive review of the TiNiPdCu system is presented in terms of thermomechanical behavior, nanoscale precipitation mechanism, microstructural features, high temperature shape memory and mechanical properties, and the important parameters to control the high temperature performance of these alloys.

Novel strategies for path stability estimation under topology change using Hello messaging in MANETs

Abstract: Path stability estimation due to connectivity failures is one of the key challenges for effective communication under random mobility of network nodes in mobile ad hoc networks (MANETs). Under random movement of network nodes and topology triggered reactive path distribution statistics among the neighboring nodes, there must be a unified model to determine an adequate path stability estimation strategy in MANETs. We present novel link connectivity metrics (LCM) and path distribution analysis (PDA) strategies for path stability estimation under uniform speed and random trajectory of mobile nodes. We also design an adaptive routing model that guarantees effective communication among neighboring nodes inside a cluster. We find that LCM strategy among neighboring nodes is affected by the link expiration time, relative velocity, link connectivity, and link stability metrics in terms of remaining probability for a connected link, link recovery probability, and stability of a path at different time steps of a Markov process. We also find that PDA strategy among neighboring nodes is affected by the link excess life, distribution of path durations, cluster stability, and path duration statistics in terms of throughput and overhead during Hello message(s) communication at different time steps of a Markov process. Analytical and simulation results indicate efficacy of the proposed LCM and PDA strategies by efficiently estimating path stability under topology change, thereby, increasing the global network connectivity.

Spatially adaptive image restoration using fuzzy punctual kriging

Abstract: We present a general formulation based on punctual kriging and fuzzy concepts for image restoration in spatial domain. Gray-level images degraded with Gaussian white noise have been considered. Based on the pixel local neighborhood, fuzzy logic has been employed intelligently to avoid unnecessary estimation of a pixel. The intensity estimation of the selected pixels is then carried out by employing punctual kriging in conjunction with the method of Lagrange multipliers and estimates of local semi-variances. Application of such a hybrid technique performing both selection and intensity estimation of a pixel demonstrates substantial improvement in the image quality as compared to the adaptive Wiener filter and existing fuzzykriging approaches. It has been found that these filters achieve noise reduction without loss of structural detail information, as indicated by their higher structure similarity indices, peak signal to noise ratios and the new variogram based quality measures.

A robust H ∞ control for unmanned aerial vehicle against atmospheric turbulence

Abstract: Unmanned aerial vehicles (UAVs) experience different atmospheric uncertainties during the flight operation. These uncertainties caused the problem in the stability and the desired performance of the system. This research paper is structured to nullify the influence of atmospheric turbulence and ground effect on the unmanned aerial vehicle to control the roll angle. The model of Dryden turbulence is used as it is one of the major disturbances affecting the UAVs and then dynamic output feedback robust controller is synthesized using linear matrix inequality (LMI) approach to minimize the effect of atmospheric turbulence in the plant. This research managed to design controller so that it can meet both robustness and stability requirements. To investigate the performance of proposed technique, robust control effort is compared with optimal LQR control law. The simulation results show that robust dynamic output feedback control has achieved good transient and steady state performance than LQR optimal control against atmospheric turbulence.