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: Quantum efficiency & Diode. The organization has 618 authors who have published 940 publications receiving 10674 citations.

Evaluation of Congestion Aware Social Metrics for Centrality-Based Routing

Abstract: Opportunistic networks utilize pocket switching for routing where each node forwards its messages to a suitable next node. The selection of the forwarder node is crucial for the efficient performance of a routing protocol. In any opportunistic network, some nodes have a paramount role in the routing process and these nodes could be identified with the assistance of the existing centrality measures available in network theory. However, the central nodes tend to suffer from congestion because a large number of nodes that are relatively less central attempt to forward their payload to the central nodes to increase the probability of the message delivery. This paper evaluates mechanisms to transform the social encounters into congestion aware metrics so that high-ranking central nodes are downgraded when they encounter congestion. The network transformations are aimed at aggregating the connectivity patterns of the nodes to implicitly accumulate the network information to be utilized by centrality measures for routing purposes. We have analyzed the performance of the metrics’ computed centrality measures using routing simulation on three real-world network traces. The results revealed that betweenness centrality along with the congestion aware network metrics holds the potential to deliver a competitive number of messages. Additionally, the proposed congestion aware metrics significantly balance the routing load among the central nodes.

Evaluating humidity sensing response of graphene quantum dots synthesized by hydrothermal treatment of glucose.

Abstract: Graphene quantum dots (GQDs) were prepared using a single-step hydrothermal treatment of glucose (C6H12O6) powder. X-ray diffraction patterns confirmed the random stacking or amorphous character of GQDs. Additionally, the UV-vis spectra confirmed the formation of GQDs with evident absorption peaks at 237 and 305 nm, which is attributed toπ-π* andn-π* transitions correspondingly. The average size and surface roughness of graphene quantum dots were estimated by atomic force microscopy images and found to be 27.0 ± 1.0 and 2.3 nm, respectively. Afterwards, the effect of increasing relative humidity (RH) from 0%-95%, and frequency, was analyzed using the capacitive and resistive responses of synthesized GQDs. The capacitive output at 0.1 kHz revealed that initially capacitance remains constant (15.0 ± 1.0 pF) up to a humidity level ranging between 0%-50%. Likewise, capacitance also displayed stabilized behavior after frequency levels were increased i.e., 1.0 and 10 kHz, at a humidity ranging from 0%-55%. Moreover, capacitance showed a 115,455, 22,480 and 3,620% improvement from their stable values at each respective frequency level i.e., 0.1, 1.0 and 10 kHz. The capacitive sensitivity decreased to 84.20 and 96.83% at greater frequencies (1.0 and 10 kHz) in comparison to the sensitivity at 0.1 kHz facing similar variations in a humid environment. In contrast, resistance displayed an exponential decline by 99.9900, 99.9796 and 99.9925%, accordingly, when RH increases from 0 to 95% at 0.1, 1.0 and 10 kHz, respectively. However, with the rise in frequency level from 0.1 to 1.0 kHz, resistive sensitivity increased considerably to 69 and 158.5%, respectively, in two prominent humidity ranges i.e., 0 ≤ RH ≤ 25% and 25% ≤ RH ≤ 50%. A further increase in testing frequency to 10 kHz enhances the resistive sensitivity by 598.5 and 178.5% when compared with the lowest sensitivity values at two noticeable humidity levels, 0%-25% and 25%-50%. The response and recovery times of our specimen were better than most of previously fabricated GQDs and other carbon-derived nanomaterials, which makes the nano-GQDs of our study more suitable for RH sensor application.

A note on classification of teleparallel conformal vector fields in bianchi type i space-times in the teleparallel theory of gravitation

Abstract: A study of teleparallel conformal vector fields in Bianchi type I space-times in the teleparallel theory of gravitation is given by using the direct integration technique. From the above study it turns out that the dimensions of teleparallel conformal vector fields are 8, 9, 10 or 11. The case when the above space-times become FRW 0 k = model it admits eleven teleparallel conformal vector fields. This classification also covers the timelike version of plane symmetric space-times.

Vibration induced failure analysis of a high speed rotor supported by active magnetic bearings

Abstract: Active Magnetic Bearings (AMBs) are increasingly used in various industries and a quick re-levitation of AMBs supported high speed flexible rotor is necessary in case of vibration induced failure. A robust fault diagnosis algorithm is presented to detect suspected saturation type of nonlinearity associated with a power amplifier. A five degree-of-freedom AMB system consisting of four opposing pair of radial magnets and a pair of axial magnets is considered. In this paper failure of an industrial grade AMB system is investigated using Sinusoidal Input Describing Function (SIDF) method. SIDF predicts the gain and frequency at which failure occurs. It is demonstrated that the predicted frequency is in agreement with the frequency at which failure occurs.

Water Absorption Resistance Study of HTV Silicone Rubber-Based Hybrid Composites

Abstract: Silicone rubber-based insulating polymers are extensively used in high voltage outdoor applications due to their high hydrophobicity and better withstand performance. However, the main problem with polymeric composites is their aging due to external environmental stresses (e.g. direct sunlight, high humidity and temperatures, ultraviolet radiations, etc.) as well as strength of the applied electrical field. In the present work, for examining weight gain, hydrophobicity, and hardness, five different types of HTV silicone rubber-based hybrid composites are prepared. All the samples are reinforced with micro-alumina (20 wt. %) and different concentrations of silica fillers. Material samples are immersed in distilled and boiling water for 24h and 2h, respectively. For analysis, hydrophobicity, weight gain and hardness tests are conducted. The results of the performed tests indicated that the sample filled with 6 wt. % of nano-silica has less percentage gain in weight due to water absorption compared to the other hybrid composites. The sample with the same composition showed high hydrophobicity as well.