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Self-healing microcapsules encapsulated with carbon nanotubes for improved thermal and electrical properties
No full textMicrocapsules are widely used by researchers in self-healing composites. In this study, multi-walled carbon nanotubes (CNT) were incorporated into the core of the microcapsules, along with the self-healing agent. Dicyclopentadiene (DCPD) and urea-formaldehyde (UF) were chosen as the core and shell materials respectively, and DCPD–CNT–UF based dual core microcapsules were synthesized. Two types of microcapsules, namely, DCPD–UF and DCPD–CNT–UF were successfully synthesized by the in situ polymerization technique. The novelty of this work is the development of dual core microcapsules with DCPD–CNT–UF combination. Surface morphology characterization and elemental analysis of the microcapsules were carried out using a scanning electron microscope (SEM-EDX). TGA and DSC analysis show that DCPD–CNT–UF microcapsules have better thermal stability than DCPD–UF microcapsules. These novel DCPD–CNT–UF microcapsules were found to be compatible with epoxy base resin for making resin castings. The presence of CNT is found to improve the mechanical, thermal and electrical properties of the resin cast specimens without compromising on self-healing efficiency
Automated Cardiac Health Diagnosis: A Time-Domain Approach.
Get PDFCardiological problems are one of the leading causes of human fatality. Electrocardiogram is a major noninvasive tool for monitoring heart conditions. The human vision is not suitable to identify the minute changes in Electrocardiogram wave amplitude and time intervals; hence an automatic diagnostic tool is necessary for precise abnormality detection. This paper presents a classification method to classify seven heartbeat conditions-normal and six classes of abnormalities. The algorithm implements a time domain approach to obtain the statistical features from the Electrocardiogram beats extracted from the arrhythmia database. This objective of this work is to find the suitability of time domain features to arrhythmia classification with machine learning. The statistical features are extracted from raw ECG signal, the time derivative, time integral and 5-point first derivative stencil of the ECG data. The cardiac abnormality classification is implemented with Support Vector Machine. The attained classification accuracy is upto 93% for chosen input feature pairs for binary Support Vector Machine
UAS Simulator: A Laboratory Set-Up
Get PDFThis work describes the procedure for laboratory setup for Unmanned Aerial System (UAS) Simulator. UAS has three major components viz., UAV (or drone), Pilot and the system in place that connects both of them or interface. This simulator not only helps pilot for training purposes, designers for testing new models, mission planners in planning missions in a different environment but also helps in testing and development of the Synthetic Vision System (SVS). SVS generates a rendered image or 3D image of the flying environment and aware operator using an onboard database of terrain, obstacles, and relevant cultural features
Rheological properties of concentrated polyacrylonitrile co-polymer and lignin blend solution
No full textPolyacrylonitrile copolymers with different molecular weights (Mws) are synthe-sised by aqueous free-radical redox polymerisation technique. Polyacrylonitrile (PAN) and lignin-blended solutions are prepared in dimethyl sulphoxide solvent by varying the polyacrylonitrile/lignin content. The effect of lignin addition to PAN copolymer having different weight-average Mws on the rheological properties is explored. Rheological measurements indicate that the solution viscosity reduces with the increase in the lignin content. The Cole–Cole plot or Han plot and Cas-son plot are used to characterise the solution homogeneity. The slope value of the plot suggests that the molecular-level homogeneity of the solution is not affected much by the addition of lignin. Thermal-induced gelation of concentrated solution has been rheologically investigated to avoid overheating of solution during the dis-solution, storage and transportation for further wet spinning process
Improvement in piezoelectric properties of PLZT thin film with large cation doping at A-site
No full textThis paper reports improved piezoelectric properties of PLZT, designed by partially substituting larger trivalent cation (Bi3+) in place of La3+. For the present investigation, stoichiometric compositions of Pb0.92(La1-yBiy)0.08(Zr0.52Ti0.48)O3 (PLBZT) with y = 0.0, 0.3, 0.5 and 0.7 were prepared by chemical solution deposition method. The XRD results and Raman spectroscopy studies reveal the change in crystal structure with an increase in distortion of the tetragonal unit cell with Bi3+ concentrations. The FESEM study shows a distinct change in the microstructure of PLZT with increasing Bi3+ concentrations. The P-E hysteresis study on all the Bi3+ doped PLZT films give slimmer hysteresis loop, relatively low coercive field (20 kV/cm) and higher switching current (0.5 mA). The polarization fatigue property of PLZT film is improved with Bi3+ doping. The enhanced piezoelectric displacement in Bi3+ doped PLZT yielded almost 3 times higher d33 values than PLZT film at y = 0.5. The substantial enhancement in piezoelectric properties of PLBZT is correlated with the intrinsic contribution of the material that arises from crystal structure and extrinsic contribution that comes from the externally triggered domain wall movement
Composites airframe panel design for post-buckling – An experimental investigation
No full textThree series of airframe composite panels with T-stiffener, I-stiffener and J-stiffener are designed and optimized to have the same local skin buckling load and weight. All the panels are designed to undergo local skin buckling between Design Limit Load (DLL) and Design Ultimate Load (DUL), approximately at 120% of DLL to utilize the reserve strength in structures. Additionally, identical panels are designed and fabricated from each series to study the effect of various extrinsic parameters such as disbond, delamination, impact damage and repeated loading to identify the best performing series for post-buckling design. All the panels are tested under compression to demonstrate no onset of damage before DUL. The influence of defects such as disbond, delamination and impact damage on the post-buckling behavior is also demonstrated. One pristine panel of each series is repeatedly loaded 1000 times beyond buckling to determine the onset of damage if any. The panels with I-stiffener and J-stiffener found to be the potential design choices for post-buckling design philosophy due to the high margin between skin buckling and collapse load even in the presence of damage. The results from this study would help in moving closer to the post-buckled composite design philosophy for airframe structure
Enhanced photothermal conversion in nanometric scale MoOx multilayers with Al2O3 passivation layer
No full textAn optically selective stack based on molybdenum oxide nanometric layers (Mo/MoOx/Mo/MoO3/Al2O3) was designed using SCOUT reflectance simulations and fabricated using balanced magnetron sputtering for applications in solar thermal systems. The material properties were experimentally optimised by varying the process parameters namely: target power, gas flow rates, and deposition time. In the stack, the bottommost Mo metal layer is used to improve adhesion, reduce diffusion while acting as an infrared reflector, the MoOx layer of the tandem stack acts as the primary light absorbing layer, and the topmost MoO3 + Al2O3 layers act as anti-reflection layers. The individual layers of the optical stack exhibited an amorphous structure as confirmed using X-ray diffraction. The existence of lower oxidation states (+4, +5) of molybdenum in the MoOx layer was revealed by X-ray photoelectron spectroscopy. The stack achieved a high absorptance in the solar spectrum region (α = 0.969) and a low thermal emissivity in the infrared region (ε = 0.15 at 82 °C) at optimal process parameters. The oxidation resistance and thermal stability were evaluated by annealing the samples in vacuum up to 500 °C
Influence of solid lubricants addition on the tribological properties of HVOF sprayed NiMoAl coating from 30 °C to 400 °C
No full textThe present study focuses on the influence of solid lubricants (MoS2, h-BN, Cr2AlC, and Cr2AlCAg) addition on the tribological properties of NiMoAl alloy in the range of 30 °C (Room Temperature, RT) to 400 °C. For this, NiMoAl and NiMoAl with 20 wt% of different solid lubricant powders were prepared and coated on a stainless steel substrate by High-Velocity Oxy-Fuel (HVOF) spraying. The coefficient of friction (COF) of NiMoAl coating at RT and 400 °C is 0.72 ± 0.05 and 0.47 ± 0.03, respectively. The addition of 20 wt% MoS2, h-BN, Cr2AlC, and Cr2AlCAg in NiMoAl reduces the COF by (50% & 30%), (47% & 45%), (37% & 49%) and (64% & 66%), respectively at RT & 400 °C. Characterization of the worn-out surfaces shows that the tribo-chemical by-products such as Ni3S2, Cr7C3, and Ag2MoO4 act as a friction modifier and reduces the COF. NiMoAl-20 wt% Cr2AlC coating shows a large decrease in COF with an increase in temperature
Shock-induced flow separation in an overexpanded supersonic planar nozzle.
Get PDFShock-induced flow separation in an overexpanded supersonic planar nozzle is investigated numerically by means
of three-dimensional wall-modeled large-eddy simulations (LES). The objective of this study is to identify the origin
of the low-frequency shock oscillations (LFO) and the associated side-loads generation in planar nozzles. The
computational results are compared with the experimental data for validation. The promise of the near-wall LES
modeling approach, adopted in this study, is supported by its satisfactory performance in correctly predicting
the shock-induced flow separation and offering a major advantage of being 30–40 times faster than the wall-resolved
LES counterpart, allowing thereby the capture of very–low-frequency shock oscillations with much better statistics
convergence. The simulations bring clear evidence of the existence of broadband and energetically significant LFO in
the vicinity of the separated shock, whose forward and backward movements are mainly driven by changes in
the downstream flow conditions. The complex interactions between the backflow, the separation bubbles, and the
large-scale turbulent structures developing in the shear-layer region strongly influence the shock unsteadiness, which in turn drives the LFO. A scenario of the LFO, confirming conclusions from earlier studies, is described in this work
Reference-Free Real-Time Power Line Monitoring Using Distributed Anti-Stokes Raman Thermometry for Smart Power Grids
No full textWe report the experimental demonstration of a reference-free Distributed Anti-Stokes Raman Thermometry (DART) scheme for real-time power line monitoring in overhead power transmission (OPGW/OPC) cables. Our work is based on the loop configuration in which only the anti-Stokes intensity is captured and processed to determine the temperature, thereby providing a self-calibrated solution that is tailor-made for a rugged field measurement. Temperature experienced by the optical fiber embedded in the power cable is estimated through a simple heat transfer model and is experimentally validated using a homebuilt DART system with a root mean square (RMS) temperature error of 0.33 °C