Department of Mechanical Engineering

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IIT Jodhpur

In this work, we report a new method for the synthesis of zinc oxide (ZnO) nanoflowers/graphene oxide (GO) composite, uniformly grown over Silicon (Si) substrate. The synthesis is performed by utilizing aqueous chemical approach where ZnO nanoseeds are obtained using zinc acetate (C4H6O4Zn) and isopropanol (C3H7OH), while Graphene oxide (GO) is fabricated by using Hummer's method. The nanocomposite was fabricated by mixing of GO and ZnO nanoseed solution followed by vigorous ultra-sonication and spin-coating over the Si substrate. Finally, the nanoflowers type structures were grown from ZnO nanoseed by placing the coated Si substrate in a solution containing Zn+2 environment. The nanocomposite was characterized by various techniques such as Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray diffraction (XRD) analysis. The performance of nanocomposite was analyzed for remediation of methylene blue (MB) dye by utilizing sunlight as an energy source to initiate the photoreaction. The composite (GO/ZnO) shows ~ 33% faster decolorization of 20 mg/L of MB dye in comparison with pure ZnO. The improved performance is attributed to the prevention of recombining of electron (conduction band) and holes (valence band) during the photocatalytic reaction. Moreover, GO itself provides excess electrons for enhancing the photocatalytic reaction by providing excess hydroxyl radicals. Further, the nanocomposite was successfully utilized for decolorization of an industrial dye. Hence, nanoflowers type ZnO/GO composite material grown over Si substrate provides an alternative for effective removal of real dye from industrial wastewater without any post process filtration requirement. © 2018

World University root node

Materials Science in Semiconductor Processing

Facile synthesis of ZnO/GO nanoflowers over Si substrate for improved photocatalytic decolorization of MB dye and industrial wastewater under solar irradiation

Modern aircraft systems are system of systems involving multidisciplinary engineering viz., aeronautical/aerospace, RF, computer science, electrical, electronics, mechanical and electromechanical, etc. The maintenance of such a system becomes complex when a system is to be operational on the 24 × 7 basis. Commercial aircraft travel thousands of miles everyday and restless schedule of takeoff, landing, and turn around to do it again. Similarly, military aircraft undergo rigorous and continuous operations during war and trial exercises. In both the cases, human lives are directly at risk if the aircraft maintenance is not proper. In addressing the aircraft system requirements, the normal tendency is to deal primarily with those elements of the aircraft system that relates directly to the aircraft performance for flying. At the same time, very little attention is given to periodic maintenance and aircraft health monitoring system until the system fails and needs breakdown maintenance. This breakdown maintenance consumes more resources in terms of time, cost, and manpower. With the advent of different embedded smart sensors, online health monitoring of such complex aircraft systems can be possible. The health of the different components of the aircraft systems can be monitored continuously and necessary preventive action can be taken immediately before it fails. This paper introduces the use of various embedded smart sensors to detect and monitor the health issues or failure of different components of the aircraft, ultimately enabling proactive maintenance to prevent aircraft subsystems/components from breakdowns. © 2019, Springer Nature Singapore Pte Ltd.

Energy, Environment, and Sustainability

Embedded Sensors for Health Monitoring of an Aircraft

In this paper we propose a distributed locality sensitive hashing based framework for image super resolution exploiting computational and storage efficiency of cloud. Now days huge multimedia data is available on the cloud which can be utilized using store anywhere and excess anywhere model. It may be noted that super resolution is required for consumer electronics display devices due to various reasons. The propose framework exploits the image correlation for image super resolution using locality sensitive hashing (LSH) for manifold learning. In our work we have exploited the benefits of manifold learning for image super resolution, which in-turn is a highly time complex operation. The time complexity is involved due to finding the approximate nearest neighbors from trillion of image patches for locally linear embedding (LLE) operation. In our approach it is mitigated by using a distributed framework which internally uses hash tables for mapping of patches in the target image from a database of internet picture collection. The proposed framework for super resolution provides promising results in comparison to existing approaches. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

Department of Computer Science & Engineering

Department of Electrical Engineering

Multimedia Tools and Applications

Image super resolution using distributed locality sensitive hashing for manifold learning

Experiments are conducted to study the flow separations on a sphere rolling on an inclined plane submerged in water. These experiments are performed at Reynolds numbers Re between 1350 and 1550. The experiments show that the flow separations on the surface of a rolling sphere can be organized into four distinct regions: (i) region of primary separation-I on the front upper sphere and extending below the poles, (ii) region of viscous blockage at the crevice surrounding the point of contact and shear layer separation ahead and at the sides of the viscous blockage, (iii) region of primary separation-II on the rear lower sphere and (iv) secondary separations on the rear upper sphere surface. The ratio of the width of the viscous blockage to the diameter of the sphere is found to be 0.4. Primary separation-I surface is symmetrical about the equatorial plane of the rolling sphere. Primary separation-II from the rear lower sphere surface is asymmetrical about the equator and eddies are shed alternately on either side of the equator from this separation surface. These lower eddies are energetic and dominate the dynamics of the wake. The upper eddy shedding from the primary separation-I surface and the lower eddy shedding from the primary separation-II surface are synchronized. © 2019, Indian Academy of Sciences.

Fulltext

Sadhana - Academy Proceedings in Engineering Sciences

Three-dimensional flow separations on a rolling sphere

In this paper, an attempt has been made to develop a framework for closed-loop impact modeling of a multi-arm robotic system mounted on a servicing satellite while capturing a tumbling orbiting object. When the satellite is in broken state or does not have provision for grapple and tumbling, the interception is very difficult. In such cases, interception using multi-arm robotic system can be appealing as this will certainly increase the probability of grasp in comparison to a single-arm robot. When multiple arms of a robot will capture only one target object from different points of contact, then it is termed as closed-loop impact. In this paper, first, the dynamic models of a multi-arm robot and a tumbling orbiting object are obtained. The target dynamics has been modeled considering it to be a rigid body. Then, the three phases of the capturing operation, namely, approach, impact, and postimpact have been modeled. Efficacy of the framework is shown using a dual-arm robot mounted on a servicing satellite performing capturing operation when both arms of robot capture a single target object. The effects of relative velocity and angle of approach on the impact forces would also be investigated.

Modeling and Estimation of Closed-Loop Impact for Multi-arm Space Robot While Capturing a Tumbling Orbiting Object

In this paper, a kinematic motion planning algorithm for cooperative spatial payload manipulation is presented. A hierarchical approach is introduced to compute realtime collision-free motion plans for a formation of mobile manipulator robots. Initially, collision-free configurations of a deformable 2-D virtual bounding box are identified, over a planning horizon, to determine a convex workspace for the entire system. Then, 3-D payload configurations whose projections lie within the convex workspace are computed. Finally, a convex decentralized model-predictive controller is formulated to plan collision-free trajectories for the formation of mobile manipulators. Our work facilitates real-time motion planning for the system and is scalable in the number of robots. The algorithm is validated in simulated dynamic environments. © 2019 IEEE.

IEEE International Conference on Automation Science and Engineering

Motion planning for multi-mobile-manipulator payload transport systems

The aim of present study is to investigate the physicochemical and thermophysical behaviour of submerged arc welding slags designed by CaO-SiO2-CaF2 and CaO-SiO2-Al2O3 system. Slag was produced during submerged arc welding using laboratory prepared agglomerated fluxes. By using mixture design and extreme vertices approach twenty one submerged arc welding slags were formulated. X-ray fluorescence technique was used to find the elemental weight percentage of each flux ingredient. The thermophysical behavior such as specific heat, thermal conductivity and thermal diffusivity of each slag was evaluated by hot disc technique. Density of submerged arc welding slags was evaluated at room temperature. FTIR technique was used to study the structural behaviour of submerged arc welding slags. Multi objective optimization technique was performed to derive the optimized slag formulations. Individual, binary and ternary slag constituents have been developed using various regression models for thermophysical and physicochemical properties. Significance level (upto 95%) has been checked for regression models by using F-test. © 2019, Springer Nature B.V.

Silicon

Design and Development of Submerged Arc Welding Slags Using CaO-SiO2-CaF2 and CaO-SiO2-Al2O3 System

Linepipe steels find application in oil and gas transportation, pressure vessels, offshore and other engineering parts because of its high strength as well as high ductility. The reason behind the combination of high strength and ductility is the very fine-grained microstructure. In the present work, a heat treatment procedure was used to alter the microstructure of as-received parent metal and to study its effect on the corrosion behaviour of as-received X70 linepipe steel. One-step austenitizing followed by quenching and subsequent tempering was performed at 300 °C, 450 °C and 600 °C temperatures to alter the microstructure of as-received base metal. To find the corrosion behaviour due to weight loss, as-received steel specimens were exposed in four different environments for 30 days (normal water pH-7, seawater pH-8.2, 5%NaCl + 10−2 mol/l sodium thiosulphate pH-3 and 5%NaCl + 10−3 mol/l sodium thiosulphate pH-5). Microstructure of different heat-treated samples shows the presence of different phases developed during heat treatment. Macrostructure examination of different immersed specimens reveals the presence of pits on the outer surface. Different pH and concentration of various exposed solutions affect the corrosion behaviour of heat-treated samples. Microhardness and impact strength of heat-treated samples were evaluated. © 2018, The Indian Institute of Metals - IIM.

Transactions of the Indian Institute of Metals

Effect of Heat Treatment on Mechanical Properties and Corrosion Behaviour of API X70 Linepipe Steel in Different Environments

The creep tests were conducted on multi-pass shielded metal arc welded P91 steel weld joint at creep exposure temperature of 620 °C for an applied stress of 150 and 200 MPa in as-welded, and post weld heat treatments (PWHTs) state. The PWHTs involved the tempering at 760 °C/2 h/air cooling (referred as PWHT) and re-austenitizing at 1040 °C/60 min/air cooling + tempering at 760 °C/2 h/air cooling (refereed as PWNT). Results indicate a great influence of heat treatment conditions on the creep rupture life, fracture location and microstructure evolution of the P91 welded joint. As-welded and PWHT specimens showed the Type IV mode of failure and the fracture occurred in soft fine-grained heat affected zone/inter-critical heat affected zone (FGHAZ/IC-HAZ). In PWNT specimens, a shift in fracture location was observed from FGHAZ/ICHAZ to over tempered base zone. The degree of heterogeneity in terms of the microstructure and mechanical properties across the welded joints before the creep exposure have observed a great influence on the creep rupture life. As compared to other heat treated specimen, PWNT specimen exhibited higher creep rupture life at the lower applied stress of 150 MPa and creep exposure temperature of 620 °C due to lower degree of heterogeneity across the welded joints. However, Laves phase formation (Fe2W/Fe2Mo) was noticed in different zones (weld zone + heat affected zones) of the crept specimen for PWNT condition exposed at 620 °C for 150 MPa. © 2018 Elsevier B.V.

Journal of Materials Processing Technology

Effect of post weld heat treatments on microstructure evolution and type IV cracking behavior of the P91 steel welds joint

In the present paper, a high-temperature packed bed energy storage system of volume 175, 000 m3 is numerically investigated. The system is a underground packed bed of truncated conical shape, which comprises of rocks as a storage medium and air as a heat transfer fluid. A one-dimensional, two-phase model is developed to simulate the transient behavior of the storage. The developed model is used to conduct a parametric study with a wide range of design parameters to investigate the change in performance during both charging and discharging operation. Results show that the model satisfactorily predicts the dynamic behavior, and the truncated conical shaped storage with a rock diameter of 3 cm, insulation thickness up to 0.6 m and charging-discharging rate of 553 kg/s leads to lower thermal losses and higher energy efficiencies. The paper provides useful insight into the transient performance and efficiency of a large-scale packed bed energy storage system within the range of parameters investigated. Copyright © 2019 ASME.