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A Novel Slotted Microstrip Patch Antenna for L-Band Applications
No full textThe demand for a low-profile compact antenna, which is light weighted and easy to fabricate, is increasing as the number of wireless system grows. A novel slotted microstrip patch antenna of this type for L-band applications is designed in this paper. The proposed antenna operates at 1.561GHz and provides a gain of 2.413dBi. It consists of a radiating slot in the patch printed on FR-4 substrate of 1.6mm thickness, with an impedance bandwidth of 653.64MHz. The partial ground plane at the backside, is designed to achieve an Omni-directional radiation pattern for the design
Effect of aerospike on unsteady transonic flow over a blunt body
No full textBlunt-nosed launch vehicles featuring large nose-cone angles experience high levels of pressure fluctuations over the payload region at transonic Mach numbers due to shock-wave/boundary-layer interactions. The main cause for this phenomenon appears to be flow instability associated with separated flow and formation of a vortex pair. Interactions between the induced velocity of the vortex pair and oncoming mean flow cause oscillations of the λ-shock system and high levels of fluctuating pressures. An aerospike causes flow separation at the nose and reattachment of the shear layer downstream, energizing the boundary layer. Consequently, flow separation and vortex formation are prevented: shock oscillations are stabilized. Dramatic reductions in the pressure fluctuations, around 95–35% in the low-frequency range, are observed along the payload region at small angles of attack. The observations are based on wind-tunnel tests involving unsteady pressure measurements, surface-flow patterns, and high-speed shadowgraph recordings on a blunt nose cone with various cone angles
Synthesis and slurry spray coating of barium strontium alumino silicate on SiC substrate.
No full textBarium strontium alumino silicate (BSAS); (Ba0.6Sr0.4Al2Si2O8) was synthesized through solid state reaction between BaCO3, SrCO3, Al2O3 and SiO2 subjected to wet milling in isopropanol for about 24 h. The sequence of the solid state reaction was studied by subjecting to DG/DTG from room temperature to 1550 °C. The crystallographic phase evolution was confirmed by X-ray diffraction of the powders calcined in the range 1000 to 1300 °C for 2 h. The monoclinic celsian phase obtained at 1300 °C, pelletized through uniaxial pressing was sinterable to 67 to 78% density in the temperature range of 1300 to 1500 °C. The density improved to 75 to 94% after ball milling for 76 h, while ZrO2 addition further improved the density by 2%. The celcian phase of BSAS was dispersed in isopropyl alcohol, milled for about 24 h and spray coated on to plain SiC and mullite precoated SiC substrates. Sintering of coated samples and characterization for weight gain/loss, microstructure, scratch test prove that mullite + BSAS coating is more effective than single layer coating of BSAS on SiC substrates
Detection of inclusion by using 3D laser scanner in composite prepreg manufacturing technique using convolutional neural networks.
No full textAmong different manufacturing techniques available for composite aircraft structures, prepreg-based manual layup is widely used. During the fabrication process, the protective films of the prepregs or other materials used in the process could get inside as a foreign object between the layers. The present method of finding the inclusions during the prepreg layup is by visual inspection in the cleanroom. Carrying out visual inspection is challenging as the layup is usually carried out on large surfaces and reflective by nature. This paper proposes a 3D laser scanner-based approach for the detection of inclusion on flat and curved surfaces. Using the portable laser scanner, the surfaces of each layer are scanned and compared the resulting point clouds using with a reference layer data. Thicknesses between two surfaces are computed with Cloud to Cloud, Mesh to Cloud and Hausdorff distance to enhance the visibility of inclusions. It was found that this approach could enhance the visibility of inclusions over 50 micron and above. These enhanced features are used to train a multiview convolutional neural network to mark the inclusion regions, which can aid the inspector to identify the inclusion regions in a fast and efficient way
Development and certification of chromic acid-free anodizing process for aircraft grade aluminium alloys
No full textchromic acid (Cr6+) anodization process is widely used for the corrosion protection of aircraft aluminium alloys.
Hexavalent chromium being toxic in nature need to be phased out by eco-friendly alternatives. In the present study modified tartaric-sulphuric acid (TSA) process has been developed followed by sealing in permanganate based bath to obtain 4 to 6 µm thick anodic oxide layer on 2024-T3, 6061-T6 and 7075-T6 aluminium alloys. The process was carried out using a pilot scale anodizing plant. The anodized specimens were characterized for visual observation, thickness, adhesion, electrical breakdown voltage, corrosion resistance and tensile behaviour. All the tests were carried out as per MIL-A-8625F specifications. The specimens were also subjected for about 800 hrs to real time corrosion testing, 200 metres away from sea shore at Mandapam Camp, Rameshwaram, India. The performance of the permanganate sealed TSA anodized aluminium alloys are comparable with that of the conventional chromic acid anodized coatings. This chromic acid-free anodization process has been qualified to airworthiness regulating standards by Indian military certification authorities. Efforts are in
progress to commercialize this technology for use on aero platforms
The effect of tin concentration on microstructural, optical and electrical properties of ito nanoparticles synthesized using green method
No full textIndium tin oxide (ITO) nanoparticles were synthesized by green combustion method using indium (In) and tin (Sn) as precursors, and Carica papaya seed extract as novel fuel. This paper highlights effect of tin concentration (5%, 10% and 50%) on microstructural, optical and electrical properties of ITO nanoparticles (NPs). The indium nitrate and tin nitrate solution along with the fuel were heated at 600 °C for 1 h in muffle furnace and obtained powder was calcinated at 650 °C for 3 h to produce ITO NPs. The above properties were investigated using XRD, FTIR, UV-Vis spectroscopy, SEM, TEM and computer controlled impedance analyser. The XRD, SEM and TEM investigations reveals the synthesized NPs were spherical in shape with an increase in average grain size (17.66 to 35 nm) as Sn concentration increases. FTIR investigations confirms the In-O bonding. The optical properties results revealed that the ITO NPs band gap decreased from 3.21 to 2.98 eV with increase in Sn concentration. The ac conductivity of ITO NPs was found to increase with increase in Sn concentration. These synthesised ITO NPs showed the excellent properties for emerging sensor and optical device application
Enhancement in cathodic redox reactions of single-chambered microbial fuel cells with castor oil-emitted powder as cathode material
No full textMicrobial fuel cell (MFC) would be a standalone solution for clean, sustainable energy and rural electrification. It can be used in addition to wastewater treatment for bioelectricity generation. Materials chosen for the membrane and electrodes are of low cost with suitable conducting ions and electrical properties. The prime objective of the present work is to enhance redox reactions by using novel and low-cost cathode catalysts synthesized from waste castor oil. Synthesized graphene has been used as an anode, castor oil-emitted carbon powder serves as a cathode, and clay material acts as a membrane. Three single-chambered MFC modules developed were used in the current study, and continuous readings were recorded. The maximum voltage achieved was 0.36 V for a 100 mL mixture of domestic wastewater and cow dung for an anodic chamber of 200 mL. The maximum power density obtained was 7280 mW/m2. In addition, a performance test was evaluated for another MFC with inoculums slurry, and a maximum voltage of 0.78 V and power density of 34.4093 mW/m2 with an anodic chamber of 50 mL was reported. The present study’s findings show that such cathode catalysts can be a suitable option for practical applications of microbial fuel cells
Calcium Bismuth Titanate with High Curie Temperature (Tc) for High-Temperature Sensor Applications
No full textBismuth layer-structured ferroelectric (BLSF) ceramics exhibit linearity in resistivity with respect to temperature changes, and therefore find application as high-temperature sensor materials. In this study, calcium bismuth titanate (CBT), a BLSF material, was synthesized by calcining combined oxide precursors at 850°C for 2 h, and its particle size distribution, phase analysis, grain size distribution and morphology were characterized. Circular discs were prepared by sintering in the temperature range of 1000 to 1200°C. The sintered discs were characterized for dielectric constant (K), P-E hysteresis loop and DC electrical resistivity (ρ) from 100 to 900°C. The highest density (> 95% Th.) was obtained for samples sintered at 1175°C. DC resistivity decreased linearly from 1014 to 105 Ω cm with the rise in temperature from 100 to 900°C, therefore
confirming CBT as a prospective high-temperature sensor material
Identification of Aircraft Longitudinal Derivatives
No full textThis chapter focuses on the application of neural networks to the problem of aircraft aerodynamic modeling and parameter estimation. The neural modeling and neural partial differentiation (NPD) method, which are presented in Chap. 2, are directly applied here to estimate the longitudinal dynamics of an aircraft system. Since the model of an aircraft system is established through the neural network, extends the use of NPD to multi-input and multi-output (MIMO) system ensures online estimation of each aircraft aerodynamics derivatives
Effect of coating thickness on the corrosion behavior of galvanized steel in 3.5 % nacl solution
No full textCorrosion behavior of three carbon steels with increasing galvanized coating thickness of 5.6, 8.4 and 19.2 μm named as T1, T2 and T3, respectively, was studied by immersion test, potentiodynamic polarization and electrochemical impedance spectroscopy in freely aerated 3.5% NaCl solution. The major phase in the corrosion product of all the samples after immersion test was found to be zincite, as determined by X-Ray Diffraction and Fourier Transform Infrared Spectroscopy techniques. The corrosion product on sample T1was well adhered and was compact in most regions. Samples T2 and T3 showed porous and non-adherent growth of corrosion product. Corrosion rates were found to increase with increasing coating thickness. The impedance provided by the coating as well as the substrate was the highest for the sample with thinnest coating (T1). The early exposure of the underlying steel in sample T1 resulted in higher corrosion resistance, which was probably due to the combined effect of zinc corrosion products and Fe-Zn alloy layer. Higher amount of protective γ-FeOOH as well as compact corrosion product could have also improved the corrosion resistance of sample T1. Although the average uniform corrosion resistance was higher for T1, the localized pitting corrosion was also observed, probably due to the thin galvanized layer