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Structural and electrical properties of M-doped TiO2 (M = Ni, Cu, Zn) relevant to their application as electrolytes for solid oxide fuel cells
No full textLow-cost semiconductors have emerged as potential electrolyte materials for intermediate temperature solid oxide fuel cells (IT-SOFC). The present work describes the synthesis and characterization of Ti0.95M0.05O2−δ (M = Ni, Cu, Zn) followed by the determination of ionic conductivity using a.c. impedance technique. The formation of the solid solution was confirmed by XRD, Raman, FTIR, DR-UV–Vis, PL, BET, FE-SEM, and EDX. The obtained ionic conductivities (in S cm−1) for TiO2 (1.92 × 10−5), Ti0.95Ni0.05O2−δ (2.78 × 10−5), Ti0.95Zn0.05O2−δ (2.16 × 10−5) at 973 K and for Ti0.95Cu0.05O2−δ (2.39 × 10−3) at 1023 K are comparable to commercially available YSZ operating at high temperature and doped ceria electrolytes. The ionic conductivities were found to increase linearly in the temperature range of 673–1023 K. The lower activation energy of 1.08, 1.41, and 1.17 eV was obtained for TiO2, Ti0.95Ni0.05O2−δ, and Ti0.95Zn0.05O2−δ, respectively. Thus, low-cost Ni, Cu, Zn-doped TiO2 solid solutions may be regarded as plausible electrolyte materials for SOFCs. Graphical abstract: Structural and electrical properties of Ti0.95M0.05O2−δ (M = Ni, Cu, Zn) are reported for their plausible applications as SOFC electrolytes. Lower Ea of 1.08, 1.41, and 1.17 eV are obtained for TiO2, Ni-TiO2 and Zn-TiO2, samples respectively. The Cu-TiO2 showed comparable oxide ion conductivity with other potential electrolyte materials
Three-dimensional direct numerical simulation of Rayleigh-Taylor instability triggered by acoustic excitation
No full textRayleigh–Taylor instability (RTI) occurs when the interface between two fluids of different densities is removed, with the heavier (cold) fluid resting on top of the lighter (hot) fluid in the equilibrium state. This arrangement is unstable due to buoyancy, in the absence of any other forces. RTI is noted across a range of length scales from very small in nuclear fusion to supernova explosion at astrophysical scales. RTI is viewed as a baroclinic instability if viscous actions are ignored. An accurate non-overlapping parallel algorithm is used to solve a three-dimensional RTI problem, employing more than 4 × 109 points and a refined time step (7.69×10−8s
) for the direct numerical simulation. Air masses at two different temperatures are initially separated by a non-conducting partition inside a box (with a temperature difference of 200 K). The impermeable partition is removed impulsively at t = 0, and the ensuing instability is triggered by an acoustic mechanism involving infra to ultrasonic pulses that travel to either side of the interface. Present high precision petascale computations enable one to capture acoustic disturbances with unprecedented accuracy without any additional interfacial disturbances. The creation of the vorticity is studied by performing enstrophy budget for the compressible flow for RTI, which shows that the viscous terms are dominant compared to the baroclinic one
Fabrication of spectrally selective tandem stack of HfZrC/HfZrCN/HfZrON/HfZrO by reactive magnetron sputtering for CSP applications
No full textA novel HfZrC/HfZrCN/HfZrON/HfZrO based solar absorber tandem stack was successfully deposited on silicon and stainless steel (SS) substrates by pulsed DC reactive magnetron sputtering using an alloy target of HfZr. The optimized tandem stack was fabricated by varying the deposition parameters like reactive gas flow rates (C2H2, N2, and O2), sputtering power, and deposition time. X-ray diffraction and X-ray photoelectron spectroscopic methods were used to determine the structural and chemical compositions present in the optimized tandem coatings. In the tandem stack, HfZrC, HfZrCN and HfZrON/HfZrO layers act as a main absorber layer, a semi-absorber layer and double layer anti-reflection in the coating structure. The high spectral selectivity was achieved by optimizing the individual layers in the tandem stack, which exhibits 0.947 of optical absorptance in the solar region and 0.14 of low emissivity in the IR region. The optimized tandem stack is stable up to a temperature of 500 °C in a vacuum environment. The present investigation demonstrates that the developed HfZrC/HfZrCN/HfZrON/HfZrO tandem stack exhibited high solar spectral selectivity and good thermal stability, thus it can be used in high-temperature solar concentrated power applications
Investigation of Pilot Inceptor Workload and Workload Buildup Technique Through Simulator and In-Flight Studies
No full textObjective: This study investigates the relationship of pilot inceptor workload (PIW) with the workload buildup flight test technique (WBFTT) with various conditions of pilot workload, for objective aircraft handling qualities (HQ) evaluation. Background: HQ evaluation of a piloted aircraft remains an elusive area of flight testing, due to the existing subjective evaluation technique for the pilot workload. The pilot control inceptor being an important interface for a pilot with the aircraft, it is the best tool to estimate pilot workload. Method: The statistical model of this research involved 3 independent variables, namely aircraft flying qualities, secondary task, and boundary effect of WBFTT, each differently affecting the pilot workload. Two studies were undertaken on a fixed-base, variable-stability HQ research flight simulator with military test pilots. In-flight study of pilot inceptor movement was undertaken in an advanced jet trainer aircraft during high pilot-gain air-to-ground target tracking tasks. Results: The results of simulator studies validated the relationships of PIW and WBFTT with statistical significance from a wide set of data, with variations in pilot workload in terms of flying qualities and secondary task. The in-flight studies validated the effects of high pilot gain and proximity to ground (boundary), on the pilot inceptor movements, in training combat maneuvers. Conclusion: Studies manifested PIW as a simple and direct measure to estimate pilot workload and WBFTT as an effective technique for HQ stress testing with high pilot gain
Study on the ANN Forecasting of Epidemical Diseases
No full textThis chapter is based on the using of artificial neural network (ANN) for epidemical outbreaks. The precise forecast informs precautionary of epidemical diseases control. This objective can only be attained through appropriate models. Not only is the forecasting precision essential but also its methodologies and procedure of model selection. This chapter directed on delivering a summary on the application of ANN for the epidemic forecasts. It also proposed a neural network model (multi-layer perceptron feed forward neural network (MLPFFNN)) for the forecasting of new arrival number of COVID-19 cases. A review on the comparison for the achievements of ANN is provided. Hybrid of ANN with other conventional methods are compared. Executing hybrid ANN with advanced algorithms like data transformation, learning algorithm, weight converging optimization increases learning and generalization of ANN beyond training. The proposed model provides a close prediction within a maximum deviation of 1500 cases at the end of July 2020
Electrospun nanofiber-based respiratory face masks—a review
No full textThe severe acute respiratory syndrome coronavirus (SARS-CoV-2) pandemic of 2019 forced widespread use of face coverings as a mandatory step towards reducing infection by the virus. The face mask acts as a barrier for transmission of infected aerosols among its user and surrounding people. This has propelled pace of research and development of face masks around the world. This short review is an effort to present advances in materials and designs used for face masks. Details available in scientific literature and company brochures have been accessed and the use of nanomaterials and designs for the new generation of face masks have been discussed. Special attention was given to the face masks based on electrospun nanofiber-based membrane materials due to their nano-sized pores, light weight, and high filtration efficiency; therefore, they are commercially viable and popular among various products available in the market. Incorporation of metal organic framework (MOFs) and graphene have opened avenues to more advanced/multi-functional, reusable, and high capacity adsorption filtration membranes. Rapid prototyping/3-dimensional (3-D) printing techniques have been applied to shorten the time of manufacture of face masks. This review is expected to be very helpful for engineers, scientists, and entrepreneurs working on development of novel face masks required in plenty during this pandemic period
Structural, magnetic, and dielectric properties of solution combustion synthesized LaFeO3, LaFe0.9Mn0.1O3, and LaMnO3perovskites
No full textNanocrystalline LaFeO3, LaFe0.9Mn0.1O3, and LaMnO3 perovskites have been synthesized by a novel solution combustion route, in which oxalyl dihydrazide (ODH) has been used as a fuel. These materials have been characterized using several physicochemical techniques. LaFeO3 and LaFe0.9Mn0.1O3 adopt an orthorhombic structure and LaMnO3 crystallizes in a rhombohedral structure as demonstrated by X-ray diffraction (XRD) patterns. The microporous character of the materials due to huge gas evolution during preparation has been revealed by field emission scanning electron microscopy (FESEM) images. Corresponding elements are present in stoichiometric amounts in all perovskites as revealed by energy dispersive X-ray spectroscopy (EDXS) analyses. X-ray photoelectron spectroscopy (XPS) studies demonstrate the presence of La3+, Fe2+, Fe3+, Mn3+, and Mn4+ species in the respective materials. Absorption bands in the frequency range of 500-600 cm-1 related to Fe-O/Mn-O bonds in FeO6/MnO6 octahedra are observed in Fourier transform infrared (FTIR) spectra. Raman spectroscopy depicts symmetric modes related to metal-oxygen bonds in orthorhombic and rhombohedral structures. Weak ferromagnetism has been observed in LaFeO3 and LaFe0.9Mn0.1O3 which is due to superexchange interaction between the magnetic cations. However, LaMnO3 shows paramagnetic behavior. The electrical characteristics exhibit the lowest dielectric loss for magnetic LaFeO3 among the LaFeO3, LaFe0.9Mn0.1O3, and LaMnO3 perovskites studied here
Control of three-dimensional separation due to sharp fins using co-rotating vanes ahead of quasi-conical and conical zones
No full textThis experimental investigation studies the effect of an array of 30° inclined co-rotating vanes in controlling a three-dimensional interaction generated by a 15° semi-infinite sharp fin at Mach 2.05. The array is located upstream of the quasi-conical and conical zones of interaction. The primary objective is to study variation in (i) vane chord length c/h = 7.2, 4.2, and 2.5 and (ii) vane height h/δ = 0.3, 0.5, and 0.75 for c/h = 2.5 case in controlling the interaction. Control with the smallest chord length of c/h = 2.5 and h/δ = 0.75 shows the most promising result relative to vanes with longer chord lengths. The vortex trails from this configuration penetrate deeply into the quasi-conical zone of interaction, thereby modifying it both azimuthally and radially. The plateau pressure in the conical region of interaction shows a reduction of approximately 60% with an accompanied reduction in the separation shock strength by nearly 70% for this case. Implementing control in either quasi-conical or conical zones reduces the overall control effectiveness considerably. Removing vanes ahead of quasi-conical zone reduces the effectiveness of favorably modifying the flow development in this region. The bow shock formed ahead of the first vane interacts with the three-dimensional interaction creating a pressure jump that separates the region of vortex influence from that of no control
Recent trends and challenges in developing boride and carbide-based solar absorbers for concentrated solar power
No full textConcentrating solar power technology has gained increased attention as a source for clean energy. However, because of low power density, it requires large areas and materials with high photothermal conversion efficiency, to harness solar energy. The solar receiver coated with solar selective material plays a critical role in efficiently converting solar energy to useful power. Because of the moderate solar selective nature and excellent thermal properties, significant efforts are currently being invested on the use of ultra-high temperature ceramics as solar selective absorbers. This literature survey presents a critical review of the research and development of early transition metal boride and carbide-based solar selective absorbers, both in bulk and tandem coating formats. In particular, we have emphasized the use of transition metal borides and carbides as intrinsic absorbers as bulk or even exploiting a multilayer design approach to improve the absorptance in the solar spectrum region. One of the key aspects is to introduce a gradient in optical constants (refractive index, extinction coefficient) to tailor high absorptance and low emissivity in tandem absorber coatings, with insightful understanding into microstructure-optical property correlation. The challenges in developing tandem solar absorbers with long-term thermal stability at mid to high temperature window in different working atmosphere are emphasized to spur the development of next generation spectrally-selective solar absorbers
Development of TRINETRA: A Sensor Based Vision Enhancement System for Obstacle Detection on Railway Tracks
No full textThis paper presents the design and development of an innovative device TRINETRA: A sensor based vision enhancement system for obstacle detection on railway tracks. The TRINETRA is termed as Technological Research and Innovation for National Empowerment of Trains to Reduce Accidents. The authors have developed a prototype of TRINETRA, which promises easy passage for trains in unknown environments such as zero visibility situations, fog, smog, and heavy rain. The prototype is based upon the integration of a camera, Radio Detection and Ranging (RADAR), and Infrared (IR) Light Amplification by Stimulated Emission of Radiation (LASER). The camera used in the prototype catches a long-range view of the track and presents it live on a mini screen fixed in the loco pilot cabin. A combined short, mid, and long-range radar sensor system is used to detect obstacles continuously in loco pilot blind spots on the track, particularly for collision avoidance assistance at high speed. The present work proposes a long-range laser IR illuminator with a wide range of color and mono cameras to aid clear and precise monitoring in zero visibility conditions, which is fixed on the front portion/engine of the locomotive/engine. The prototype experimental results for 2 m - 2 km distances have been performed on a live running train, which shows that the developed prototype tracks obstacles effectively during fog and smog conditions. The design concept, observation, prototype model, and other technical specifications have been presented, and satisfactory results were found