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Solution combustion synthesis, characterization, magnetic, and dielectric properties of CoFe2O4 and Co0.5M0.5Fe2O4 (M = Mn, Ni, and Zn)
No full textNanocrystalline CoFe2O4 and Co0.5M0.5Fe2O4 (M = Mn, Ni, and Zn) ferrites were prepared by the solution combustion method using oxalyl dihydrazide as a fuel. These materials were characterized by several physicochemical techniques. X-ray diffraction (XRD) patterns indicate the cubic spinel structure of these ferrites. Field emission scanning electron microscopy (FESEM) images demonstrate the microporous nature of the materials because of the large amount of gas production during their synthesis. High resolution transmission electron microscopy (HRTEM) images show lattice fringes corresponding to the {220} and {311} planes of the spinel structure. Fourier transform infrared (FTIR) spectra exhibit absorption bands around the 500–600 cm−1 wavenumber region which are related to metal–oxygen bonds with tetrahedral coordination. Symmetric and asymmetric stretching and symmetric bending modes associated with tetrahedral and octahedral cations present in the spinel structures have been assessed by Raman spectroscopy. X-ray photoelectron spectroscopy (XPS) studies demonstrate the presence of Co2+, Mn2+, Ni2+, Zn2+, and Fe3+ in tetrahedral and octahedral coordinations in these ferrites. Co0.5Zn0.5Fe2O4 is observed to show the highest saturation magnetization among all these materials. The dielectric measurements reveal that the dielectric constant and loss values decrease with an increase in frequency and the ac conductivity increases at higher frequencies due to mobilization of the charge carriers
Drone-borne magnetic measurements in India
No full textThe Drone-borne magnetic measurements for the first time in India are recorded near Yacharam mafic dolerite dyke using light weight potassium magnetic sensor towed as under slung by an indigenously developed Drone. The dyke cuts across Hyderabad Nagarjuna Sagar road (on NH-65) 51Km from Hyderabad, Telangana State and 200 m North of Yacharam town. An area of 1 Km X 0.6 Km has been selected at test site with a profile (N-S) length of 900 m and line spacing of 50 m. The data has been acquired at 5 samples/ second along 12 profile lines with a drone speed of 5m/second and 35m above the ground surface. The magnetic anomaly map generated based on the UAV-Magnetometer data clearly identifies the geological feature of existence of Dolerite dyke intrusion in granitic-gneissic terrain. The measurement repeatability of the system has been tested by repeated acquisition along two lines and good correlation is found in two data sets. The present study has successfully demonstrated the capability of Drone-Magnetic survey, which is cost effective, faster and reliable
Applicability of tricycle modelling in the simulation of aircraft steering system.
No full textAircraft nose wheel steering system is simulated on MATLAB–Simulink platform to understand the influence of tyre–ground interaction and aircraft ground dynamics on the steering behaviour of the aircraft. The aircraft steering system model generally includes the Nose Landing gear model, Aircraft Dynamics model and Tyre model. In most of the literature, bicycle modelling method is adapted with two main gears lumped together and a nose landing gear, whereas tricycle modelling method with all the three gears is more appropriate and accurate way of predicting the aircraft steering response. In the present work, the mathematical formulation for the tricycle model is developed and it is observed that the resultant equations are non-linear and coupled, whereas the bicycle model is represented with linear and coupled equations. For the same inputs parameters, both tricycle and bicycle models are simulated. Results obtained from both the models are within 5% difference with the introduction of additional non-linearity in the tricycle modelling. Hence for aircraft with nose wheel steering, bicycle method is sufficient for predicting steering response but for the all-wheel steering system (steering on both nose and main landing gear), it is more appropriate to use the tricycle modelling method to predict the accurate steering response
Ferroelectric Phase Transitions of Modified [(Na0.5Bi0.5)1 – xLax]TiO3 (x = 0–0.1) Sodium Bismuth Titanate-Based Ceramics.
No full textWe have studied the effect of A-site cation substitutions in sodium bismuth titanate on the structural parameters, microstructure, and dielectric and ferroelectric properties of [(Na0.5Bi0.5)1 – xAx]TiO3 (A =La3+, x = 0–0.1) ceramics, including those modified with KCl additions. The samples have been shown to undergo phase transitions, which show up as anomalies in dielectric permittivity near ~400 K and peaks at ~600 K. The phase transitions near 400 K exhibit well-defined relaxor behavior, indicative of the presence of
polar regions in a nonpolar matrix, as supported by laser second harmonic generation measurements
Fatigue Crack Growth Prediction under Spectrum Load in an Aluminium Alloy using Crack Driving Force K*eff Approach
No full textFatigue Crack Growth (FCG) behaviour in a Single-Edge-Notched Tension (SENT) specimen of 2024-T3 aluminium
alloy under a standard mini-FALSTAFF spectrum load sequence was experimentally determined. Further, the FCG
behaviour was predicted using cycle-by-cycle method and compared with experimental results. Prediction procedure
involved are rain-flow counting of fatigue load cycles, estimation of crack driving force for each of the counted cycle
and prediction of crack extension per cycle from constant amplitude crack growth rate equation. In the present work, a
new crack driving force (CDF) K*eff involving Kujawski’s crack driving force K* in conjunction with Elber’s crack
closure concept was used to account for load interaction effects. FCG prediction was also made using conventional
CDF ΔKeff (Elber’s) approach. A good correlation was observed between experimental and predicted FCG behaviour
under spectrum loads by the proposed K*eff approach. Also, this prediction was observed to be better than that
predicted by conventional ΔKeff approach
Site Effects Investigation in Srinagar City of Kashmir Basin Using Microtremor and Its Inversion.
No full textThe Srinagar region of Kashmir Valley in North West Himalayas, covers more than 2 million inhabitants and is exposed to high seismic risk. In order to gain insight on potential site effects and subsurface structure of the region, we carried out an extensive high-resolution microtremor ambient noise survey at 429 locations. The acquired dataset was processed using the Horizontal to Vertical Spectral Ratio (HVSR) technique to map the resonance frequency, the thickness of sedimentary cover, and to identify areas prone to seismic amplification. We provide a spatial classification of the obtained HVSR curves in four types: (1) clear peak H/V curves relating the strong impedance contrast in the subsurface; (2) multiple peaks (or Broad) H/V curves corresponding to sloping internal stratification of sediments; (3) two peaks H/V curves related to two different impedance contrast existing in the subsurface; (4) flat H/V curves around and over hard rock outcroppings. The HVSR curves show the peaks in the range of 0.22 Hz to 9.96 Hz indicating heterogeneous and complex sedimentary cover in the region. Inversion of the HVSR curves gives the shear waves velocity distribution which highlights two distinct reflective surfaces in most of the areas. In addition, we also used the estimated fundamental frequency of various types of houses/buildings located in Srinagar city to assess the possibility of resonance in case of occurrence of any earthquake. This study adds a value to the region in earthquake engineering, seismic hazard and risk evaluation purpose for Srinagar and its suburb
The dynamic and thermodynamic structure of the monsoon over southern India: New observations from the INCOMPASS IOP
Get PDFSome of the highest summer monsoon rainfall in South Asia falls on the windward slopes of the Western Ghats mountains on India's west coast and offshore over the eastern Arabian Sea. Understanding of the processes determining the spatial distribution and temporal variability of this region remains incomplete. In this paper, new Interaction of Convective Organization and Monsoon Precipitation, Atmosphere, Surface and Sea (INCOMPASS) aircraft and ground-based measurements of the summer monsoon over the Western Ghats and upstream of them are presented and placed within the context of remote-sensing observations and reanalysis. The transition from widespread rainfall over the eastern Arabian Sea to rainfall over the Western Ghats is documented in high spatial and temporal resolution. Heavy rainfall offshore during the campaign was associated primarily with mid-tropospheric humidity, secondarily with sea surface temperature, and only weakly with orographic blocking. A mid-tropospheric dry intrusion suppressed deep convection offshore in the latter half of the campaign, allowing the build-up of low-level humidity in the onshore flow and enhancing rainfall over the mountains. Rainfall on the lee side of the Western Ghats occurred during the latter half of the campaign in association with enhanced mesoscale easterly upslope flow. Diurnal cycles in rainfall offshore (maximum in the morning) and on the mountains (maximum in the afternoon) were observed. Considerable zonal and temporal variability was seen in the offshore boundary layer, suggesting the presence of convective downdraughts and cold pools. Persistent drying of the subcloud mixed layer several hundred kilometres off the coast was observed, suggesting strong mixing between the boundary layer and the free troposphere. These observations provide quantitative targets to test models and suggest hypotheses on the physical mechanisms determining the distribution and variability in rainfall in the Western Ghats region
Electrochemical and Exfoliation Corrosion Behavior of Reversion-Treated High-Strength Aluminum Alloy
No full textThe present study aims to understand the
microstructural modification affecting the electrochemical
and exfoliation corrosion (EXCO) characteristics of alu-
minum alloy 7010. The alloy was aged for two different
tempers, namely peak aging (T6) and retrogression and re-
aging (RRA). The standard electrochemical polarization
tests and EXCO tests were performed on the treated alloys.
The microstructure of the alloy observed under a scanning
transmission electron microscope revealed the presence of
continuous grain boundary precipitates in T6 alloy. These
precipitates were formed discontinuously after RRA treat-
ment. The RRA alloy microstructure resulted in a shift
toward positive potential. The exfoliation corrosion depth
was reduced to 60–70 lm after RRA treatment, which was
measured to be about 250 lm in T6 condition. The resis-
tance toward the exfoliation corrosion was found to be
influenced by the enriched Cu content of precipitates on
grain boundary after reversion treatment. The results con-
firm that the RRA-tempered alloy improves both electro-
chemical corrosion and EXCO resistance
Effect of surface roughness on the solar photothermal conversion efficiency of spray-coated CuCo2O4 films
No full textMixed transition metal oxide films are emerging as efficient and inexpensive potential alternatives to multilayer cermet spectrally selective coatings. However, to replace the current standards involving a complex metal–dielectric structure, oxides must be optimized in terms of their electronic structure and mainly their film morphology. In the present work, a simple ultrasonic nebulized spray pyrolysis technique is used to deposit CuCo2O4 films for solar absorber coatings. Their photothermal efficiencies are studied for solar thermal energy harvesting for different film thicknesses obtained by varying the deposition time. The film surface attributes are studied using atomic force microscopy and scanning electron microscopy. The films deposited for 5 and 10 min show relatively high visible absorptance (∼0.79) and relatively low thermal emittance (∼0.1) and thus are promising candidates for spectrally selective coatings. Meanwhile, increasing the deposition time (>10 min) increases the thickness, thereby increasing the solar absorptance. However, this results in an uncontrolled increase in the surface roughness, which affects the spectral selectivity adversely, leading to the films having higher thermal emittance of between 0.1 and ∼0.25. Analysis of the specular reflection contribution shows that this deterioration is governed predominantly by interference effects due to surface attributes. This study is important for the technological applications of spectrally selective coatings and makes a significant quantitative contribution to emphasize the importance of surface morphology in optics
Effect of Tufting on Mechanical Performance of Co-cured Co-infused Carbon-Epoxy Composite T-joint
No full textStructural performance of a composite T-joint is investigated to show the efficacy of tufting on the out-of-plane load bearing capability. T-joint representing portion of skin, stringer and rib construction of actual co-cured composite wing of a civil aircraft is selected for this study. Pull-off tests are performed on T-joints to capture failure strength and failure mechanism. The structural behavior of the T-joint in presence of stringer is examined in both tufted and un-tufted case. The pull-off failure load with tufting increased by around 24% compared to the un-tufted T-joints. Tufting also showed enhancement in joint toughness by 120%. Failure modes are similar for both tufted and un-tufted T-joints. Failure at interface is not sudden and progressive failure mechanism is observed in both tufted and un-tufted T-joints. Digital image correlation (DIC) technique is used for full field deformation and strain measurement on the skin. DIC results showed that tufting decreased disbond growth rate in the T-joints. Disbond growth rate was 24% slower in the tufted T-joint