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Efficient synthesis of perovskite-type oxide photocathode by nonhydrolytic sol-gel method with an enhanced photoelectrochemical activity
No full textThe photoelectrochemical activity of PbTiO3 (PTO) for water splitting was studied by linear sweeping voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) techniques. The nanohydrolytic sol-gel method was used to synthesise a crystalline PbTiO3 perovskite nanoparticles. The physical and chemical properties of nanoparticles such as crystal structure, surface area, reducibility, band gap energy, particle morphology and size, surface composition and valence states were investigated by X-Ray diffraction (XRD), BET, temperature-programmed reduction (TPR), UV diffuse reflectance spectroscopy (UV-DRS), high resolution scanning and transmission electron microscopy (HR-SEM and HR-TEM) along with X-Ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). PTO nanoparticles showed pure crystallinity, high surface area (14 m(2)/g) and high oxygen mobility. PTO has band gap energy of 2.66 eV, which makes it active under visible light irradiation. Moreover, nanoparticles vary in size and create a core-shell structure in a way that small particles surround large particles. The core-shell structure along with a free defected sites on the surface results in high photoelectrochemical activity for water splitting reaction. The I-V curve revealed that the PTO nanoparticles are a p-type electrode with the photocurrent efficiency of approximate to 19%. This suggests that the photoelectrode does not require external bias to initiate the water splitting and the reaction can be initiated simply by making a connection between the anode and the cathode. In addition, a great stability is observed for PTO electrodes during the reaction, as evidenced by no leaching to the reaction medium. (C) 2018 Elsevier B.V. All rights reserved
Total Synthesis of Emmyguyacins A and B, Potential Fusion Inhibitors of Influenza Virus
No full textFungal glycolipids emmyguyacins A and B inhibit the pH-dependent conformational change of hemaglutinin A during replication of the Influenza virus. Herein, we report the first total synthesis and structure confirmation of emmyguyacins A and B. Our efficient route, which involves regioselective functionalization of trehalose, allows rapid access to adequate amounts of chemically pure emmyguyacin analogues including the desoxylate derivatives for SAR studies
Effect of buffer iron doping on delta-doped beta-Ga2O3 metal semiconductor field effect transistors
No full textWe report on the effect of iron (Fe)-doped semi-insulating buffers on the electron transport and DC-RF dispersion in Si delta (delta)-doped beta-Ga2O3 metal-semiconductor field effect transistors. The effect of the distance between the 2-dimensional electron gas and the Fe-doped region was investigated, and Fe doping in the buffer was found to have a significant effect on the transport properties. It was found that buffers thicker than 600 nm can enable better transport and dispersion properties for field effect transistors, while maintaining relatively low parasitic buffer leakage. This work can provide guidance for the use of Fe-doped insulating buffers for future Ga2O3 based electronics. Published by AIP Publishing
Pipe wall thickness prediction with CFD based mass transfer coefficient and degradation feedback for flow accelerated corrosion
No full textPipe wall thickness reduction due to Flow Accelerated Corrosion (FAC) depends on mass transfer coefficient (MTC), temperature, pH and roughness. The purpose of this research work is to predict the wall thickness reduction due to FAC in bends and orifice. The paper proposes a model for temporal wall thickness prediction in pipe bend and orifice taking into account the positive feedback from FAC induced roughness and spatial MTC. This is applied for two geometrical configurations (i) FAC experiment performed on 58 degrees carbon steel pipe bend (ii) FAC experiment in an orifice with gypsum. In the 58 degrees carbon steel pipe, the predictions were in good comparison with the experimental values at different locations with percentage error between the predicted and experimental wall thickness in the range (-5%, +12%) at all locations on pipe extrados. For the orifice, the error was in the range of (-0.3 mm, +0.6 mm) at all measured locations. The MTC was estimated using computational fluid dynamics (CFD) with k-w SST (shear stress transport) model for both configurations. The comparison of predicted values of wall thickness with experimental values shows that errors in prediction are moderate to low
Evaluation of estuary shoreline shift in response to climate change: A study from the central west coast of India
No full textThe prediction of coastal sediment transport and rate of change of shorelines into the future are traditionally done by analysis of historical satellite imageries and field observations or by empirical/numerical modeling. The modeling is traditionally done on the basis of historical data. Instead, here, we suggest the use of future conditions impacted by the climate change for this purpose and a procedure based on regional climate models. Further, considering the difficulty at some places to acquire a large amount of data of various parameters to run a numerical model, we propose the use of simple neural network as an alternative. The location studied belongs to the shoreline adjoining the estuary of River Gangavali, along the central west coast of India. Waves were simulated using a numerical wave model for past and future time periods of 36years each, and a numerical coastal evolution model was run with this input. It was found that in future, the wave activity at this site would intensify along with certain shift in the direction of wave attack. This will push the net and gross sediment transports up by 131.7% and 114.3%, respectively, and also enhance the shoreline change rate. It was noticed that the future shifts in the wave direction could be as influential as those in the wave height and can cause more accretion of the shoreline. The study emphasizes the importance of considering the projected climate over the past one in planning a regional coastal ecosystem
Analytical modeling of temperature and power dependent photoluminescence (PL) spectra of InAs/GaAs quantum dots
No full textIn order to theoretically analyze the Photoluminescence (PL) spectra and its dependence on temperature and power, we have calculated the electronic band structure of self-assembled InAs/GaAs Quantum Dots (QDs) with a temperature dependent 8 band k.p Hamiltonian by including the effects of strain. The transition energies for the ground state and the first excited state are calculated using a mathematical model, which takes into account the effect of both homogeneous and inhomogeneous broadening, caused due to carrier scattering processes and QD size variation, respectively. Our proposed analytical model describes the origin of bimodal peak in the PL spectra and its correlation with the transition energies for different temperatures by considering the temperature induced intrinsic carrier concentration and carrier relaxation time. The applicability of the derived expression is validated using the experimental data of single layer InAs/GaAs QDs grown using Stranski-Krastanov growth mode. In addition to this, the simplicity of the model and its various useful aspects including computation of temperature dependent electronic band profiles and complete PL spectra make it a potential tool to study the optoelectronic properties of QD heterostructures. Published by AIP Publishing
A systematic literature review of Burgers' equation with recent advances
No full textEven if numerical simulation of the Burgers' equation is well documented in the literature, a detailed literature survey indicates that gaps still exist for comparative discussion regarding the physical and mathematical significance of the Burgers' equation. Recently, an increasing interest has been developed within the scientific community, for studying non-linear convective-diffusive partial differential equations partly due to the tremendous improvement in computational capacity. Burgers' equation whose exact solution is well known, is one of the famous non-linear partial differential equations which is suitable for the analysis of various important areas. A brief historical review of not only the mathematical, but also the physical significance of the solution of Burgers' equation is presented, emphasising current research strategies, and the challenges that remain regarding the accuracy, stability and convergence of various schemes are discussed. One of the objectives of this paper is to discuss the recent developments in mathematical modelling of Burgers' equation and thus open doors for improvement. No claim is made that the content of the paper is new. However, it is a sincere effort to outline the physical and mathematical importance of Burgers' equation in the most simplified ways. We throw some light on the plethora of challenges which need to be overcome in the research areas and give motivation for the next breakthrough to take place in a numerical simulation of ordinary / partial differential equations
Isolation and biochemical characterisation of two thermophilic green algal species- Asterarcys quadricellulare and Chlorella sorokiniana, which are tolerant to high levels of carbon dioxide and nitric oxide
No full textAtmospheric levels of carbon dioxide (CO2) and nitric oxide (NO) have been on the rise ever since the beginning of industrialisation. A significant fraction of this increase can be attributed to the emissions from stationary sources such as thermal power plants and steel plants. While there has been an impetus in recent times towards sequestration of these greenhouse gases at source, current technologies are not commercially viable. In this context, microalgae-mediated CO2 capture and utilization has attracted attention, although several technological challenges remain to be addressed. Importantly, this process will require algal strains that grow fast and are tolerant to high light, temperature and flue gases. The majority of the reported algal strains fail in at least one of these requirements. On account of this, we have isolated two novel green algal strains, which have been identified as Asterarcys quadricellulare and Chlorella sorokiniana, from water bodies that are located in and around a steel plant in India. These are relatively fast-growing strains with specific growth rates of up to 0.06 h(-1) and 0.1 h(-1), respectively. Furthermore, these strains can tolerate high temperatures of up to 43 degrees C, high light intensity and high CO2 and NO levels. When exposed to high CO2 levels, 55-71% of the dry cell weight comprised of carbohydrates. Additionally, exposure to NO gas along with CO2 led to an enhanced lipid accumulation of 44%-46% of dry biomass. The high lipid content makes these strains valuable feedstock in biodiesel production, and the high carbohydrate content makes the lipid extracted biomass an attractive source of carbon for biochemical conversion to ethanol. We believe that these strains are promising and ready to be tested with real flue gases under outdoor conditions
Inclusive J/psi production in Xe-Xe collisions at root s(NN)=5.44 TeV
No full textInclusive J/psi production is studied in Xe-Xeinteractions at a centre-of-mass energy per nucleon pair of root s(NN) = 5.44 TeV, using the ALICE detector at the CERN LHC. The J/psi meson is reconstructed via its decay into a muon pair, in the centre-of-mass rapidity interval 2.5 < y < 4 and down to zero transverse momentum. In this Letter, the nuclear modification factors R-AA for inclusive J/psi, measured in the centrality range 0-90% as well as in the centrality intervals 0-20% and 20-90% are presented. The R-AA values are compared to previously published results for Pb-Pbcollisions at root s(NN) = 5.02 TeV and to the calculation of a transport model. A good agreement is found between Xe-Xe and Pb-Pbresults as well as between data and the model. (C) 2018 Organisation europeenne pour la recherche nucleaire. Published by Elsevier B.V
Flexible Power Electronic Converters for Producing AC Superimposed DC (ACsDC) Voltages
No full textSeveral applications such as power supplies for electric precipitators, ozone generation, partial discharge, etc., require ac superimposed dc (ACsDC) voltage supply. Most of such applications use intransigent systems for producing ACsDC voltages. In this paper, three different kinds of flexible power electronic converters are proposed for producing ACsDC voltages. These converters have two power conversion stages: input and output. In the input stage, two isolated dc voltages are obtained by using an isolated three-port dc-dc converter or two isolated two-port dc-dc converters. In the output stage, one of the input-stage dc voltages is used to generate an ac voltage and the obtained ac voltage is added to the remaining input-stage dc voltage to obtain an ACsDC voltage. Based on the converters used in the input stage, the proposed ACsDC converters are named as a dual active bridge (DAB) converter-based ACsDC converter (DAB-ACsDC), triple port active bridge (TAB) converter-based ACsDC converter (TAB-ACsDC), and dual transformer-based asymmetrical triple port active bridge (DT-ATAB) converter-based ACsDC converter (DTATAB-ACsDC). A detailed analysis of these ACsDC converters and their verifications using simulations and experimental studies are presented, which depict that the proposed converters can be used effectively for producing ACsDC voltages