This research article mainly reports on the precise structural,optical,and photocatalytic properties of cerium(Ce)-substituted yttrium manganite(YMnO_(3))nanoparticles synthesized by the polyacrylamide gel method.The ...This research article mainly reports on the precise structural,optical,and photocatalytic properties of cerium(Ce)-substituted yttrium manganite(YMnO_(3))nanoparticles synthesized by the polyacrylamide gel method.The characteristics of YMnO_(3)were investigated by the substitution of Ce into the Y site at various molar percentages.The Raman and X-ray diffraction(XRD)analyses confirmed the pure phase of hexagonal YMnO_(3),supported by the Rietveld refinement.The microstructural studies indicate inhomogeneous and irregular particle distribution.The X-ray photoelectron spectroscopy(XPS)results show the presence of two ionic states of Mn and Ce along with Y^(3+)state and oxygen vacancies.Extensive optical exploration using photoluminescence(PL)spectroscopy and UV-Vis-NIR analysis indicates that the intensity of absorption peak increases in the visible region,while the bandgap decreases from 1.42 to1.30 eV with the Ce ion doping(5 mol%-15 mol%).Photocatalytic properties of the polycrystalline nanoparticles were investigated by degradation of the pollutant 4-nitrophenol.The process of amplified photocatalysis process was elucidated by the lowered bandgap and rate of charge carrier recombination.It can be conjugated from this study that the synthesized nanoparticles may be employed as highly efficient(92.8%)visible light-triggered photocatalysts in a variety of real-world applications.展开更多
The recycling of rare earth elements（REE） from end-of-life REE based products is an environment friendly proposition. Waste Sm-Co based permanent magnet generated during machining is a good source for both Sm and Co...The recycling of rare earth elements（REE） from end-of-life REE based products is an environment friendly proposition. Waste Sm-Co based permanent magnet generated during machining is a good source for both Sm and Co. In the present study a simpler process of acid leaching at 80 ℃ followed by solvent extraction, oxalate precipitation and calcination is described for producing pure Sm2 O3 and Co3 O4. With either 10 vol% H2SO4 or 15 vol% HCI at 80 ℃ more than 95% Sm and Co are leached in 1 h.Extraction of Sm from sulphate leach liquor with TBP or Aliquat 336 was poor. Although extraction with TOPS-99 is quantitative but Sm from sulphate leach liquor precipitated as Sm2（SO4）3·8 H2O. The chloride leach liquor at an initial pH of 2.5 and with 1.2 mol/L TOPS-99 shows requirement of 4-stages at A：O = 3：2. Stripping with oxalic acid precipitates Sm-oxalate which is calcined at 800 ℃ to produce Sm2 O3. Co3 O4 is recovered from the raffinate through oxalate precipitation followed by calcination at450℃.展开更多
In the nonparametric data envelopment analysis literature,scale elasticity is evaluated in two alternative ways:using either the technical efficiency model or the cost efficiency model.This evaluation becomes problema...In the nonparametric data envelopment analysis literature,scale elasticity is evaluated in two alternative ways:using either the technical efficiency model or the cost efficiency model.This evaluation becomes problematic in several situations,for example(a)when input proportions change in the long run,(b)when inputs are heterogeneous,and(c)when firms face ex-ante price uncertainty in making their production decisions.To address these situations,a scale elasticity evaluation was performed using a value-based cost efficiency model.However,this alternative value-based scale elasticity evaluation is sensitive to the uncertainty and variability underlying input and output data.Therefore,in this study,we introduce a stochastic cost-efficiency model based on chance-constrained programming to develop a value-based measure of the scale elasticity of firms facing data uncertainty.An illustrative empirical application to the Indian banking industry comprising 71 banks for eight years(1998–2005)was made to compare inferences about their efficiency and scale properties.The key findings are as follows:First,both the deterministic model and our proposed stochastic model yield distinctly different results concerning the efficiency and scale elasticity scores at various tolerance levels of chance constraints.However,both models yield the same results at a tolerance level of 0.5,implying that the deterministic model is a special case of the stochastic model in that it reveals the same efficiency and returns to scale characterizations of banks.Second,the stochastic model generates higher efficiency scores for inefficient banks than its deterministic counterpart.Third,public banks exhibit higher efficiency than private and foreign banks.Finally,public and old private banks mostly exhibit either decreasing or constant returns to scale,whereas foreign and new private banks experience either increasing or decreasing returns to scale.Although the application of our proposed stochastic model is illustrative,it can be potentially applie展开更多
Objective:To surveill emerging variants by nanopore technology-based genome sequencing in different COVID-19 waves in Sri Lanka and to examine the association with the sample characteristics,and vaccination status.Met...Objective:To surveill emerging variants by nanopore technology-based genome sequencing in different COVID-19 waves in Sri Lanka and to examine the association with the sample characteristics,and vaccination status.Methods:The study analyzed 207 RNA positive swab samples received to sequence laboratory during different waves.The N gene cut-off threshold of less than 30 was considered as the major inclusion criteria.Viral RNA was extracted,and elutes were subjected to nanopore sequencing.All the sequencing data were uploaded in the publicly accessible database,GISAID.Results:The Omicron,Delta and Alpha variants accounted for 58%,22%and 4%of the variants throughout the period.Less than 1%were Kappa variant and 16%of the study samples remained unassigned.Omicron variant was circulated among all age groups and in all the provinces.Ct value and variants assigned percentage was 100%in Ct values of 10-15 while only 45%assigned Ct value over 25.Conclusions:The present study examined the emergence,prevalence,and distribution of SARS-CoV-2 variants locally and has shown that nanopore technology-based genome sequencing enables whole genome sequencing in a low resource setting country.展开更多
Functionalized single-walled carbon nanotubes(f-SWCNTs)hybridized with freshly prepared zinc oxide(ZnO)nanocrystals have been found to be good luminescent material with tuned emission properties.A three-phase nanocomp...Functionalized single-walled carbon nanotubes(f-SWCNTs)hybridized with freshly prepared zinc oxide(ZnO)nanocrystals have been found to be good luminescent material with tuned emission properties.A three-phase nanocomposite of sulfonated polyaniline embedded with such SWCNT/ZnO nanostructures has been prepared by a simple solution mixing chemical process and characterized by using high-resolution transmission electron microscopy,X-ray diffractometry,Raman spectroscopy,Fourier transform infrared spectroscopy,and thermogravimetric analysis.The study of UVvisible absorption and photoluminescence spectroscopies reveal that the ternary polymer nanocomposite is a luminescent material with enhanced emission intensity.Also an increase in DC conductivity indicates that the nanocomposite is also a good conductive material,satisfying Mott’s variable range hopping model for a two-dimensional conduction.Such a three-phase nanocomposite may find extensive application in dye-sensitized solar cells,sensors,and supercapacitors.展开更多
An approach was developed to upgrade the bauxite ore by molecular hydrogen and hydrogen plasma. A gibbsite-type bauxite sample was obtained from National Aluminium Company（NALCO）, Odisha, India. The obtained sample ...An approach was developed to upgrade the bauxite ore by molecular hydrogen and hydrogen plasma. A gibbsite-type bauxite sample was obtained from National Aluminium Company（NALCO）, Odisha, India. The obtained sample was crushed and sieved（to 100 μm） prior to the chemical analysis and grain-size distribution study. The bauxite sample was calcined in the temperature range from 500 to 700°C for different time intervals to optimize the conditions for maximum moisture removal. This process was followed by the reduction of the calcined ore by molecular hydrogen and hydrogen plasma. Extraction of alumina from the reduced ore was carried out via acid leaching in chloride media for 2 h at 60°C. X-ray diffraction, scanning electron microscopy, thermogravimetry in conjunction with differential scanning calorimetry, and Fourier transform infrared spectroscopy were used to determine the physicochemical characteristics of the material before and after extraction. Alumina extracted from the reduced ore at the optimum calcination temperature of 700°C and the optimum calcination time of 4 h is found to be 90% pure.展开更多
Nano-sized polyacrylonitrile （PAN） particles were prepared under the catalytic effect of in situ developed CoCl2/EDTA complex with ammonium persulfate as the initiator in the absence of any added emulsifier. The emu...Nano-sized polyacrylonitrile （PAN） particles were prepared under the catalytic effect of in situ developed CoCl2/EDTA complex with ammonium persulfate as the initiator in the absence of any added emulsifier. The emulsion polymerization was studied at varying concentrations of the initiator, monomer, complex and solvent over a temperature range of 30-70℃. The overall activation energy （Ea, 49.79 kJ/mol）, energy of dissociation of initiator （Ed, 82.68 kJ/mol）, number of micelles （0.163 × 10^18） and the viscosity average molecular weight of the polymer were computed. The distribution of particle sizes was determined by transmission electron microscopy （TEM）. It was found that the oil-in-water polymerization was stabilized by the presence of the CoCl2/EDTA in situ complex reducing the particle size into the nano order. The average diameters of PAN nano particles, obtained by TEM, were in the range of 50-150 nm at the maximum conversion. The experimental particle size was mainly dependent on the concentration of the complex and temperature.展开更多
Magnesium and magnesium in-situ composites have significant potential in the application of design and manufacturing for automotive and aerospace industries because of their high specific strength and reduced fuel con...Magnesium and magnesium in-situ composites have significant potential in the application of design and manufacturing for automotive and aerospace industries because of their high specific strength and reduced fuel consumption.But there are many challenges for machining of Mg based alloys and composites because of the high tendency of fire and oxidation.These challenges can be minimized through microstructural engineering.In this present study,the machining performances of AZ91 Mg alloy and in-situ hybrid TiC+TiB_(2)reinforced AZ91 metal matrix composite was investigated.The effectβ-Mg_(17)Al_(12)phases and grain refinement with and without in-situ particles on machinability were studied through microstructural engineering via aging and friction stir processing.The end milling operation was carried out at different cutting speeds ranging from 25 mm/min to 90 mm/min under dry environment by using an AlTiN-coated tungsten carbide tool.The optimum cutting speed for machining was found to be 75 mm/min based on the surface roughness values of all conditioned materials.The base material with dendritic microstructure was found to have poor machinability in terms of inadequate surface finish and edge-burrs formation.The combined effect of in-situ TiC+TiB_(2)particles addition and grain refinement enhanced the machining performance of the material with superior surface finish,negligible edge-burr formation and better tool wear resistance.The influence of in-situ TiC+TiB_(2)particles,β-Mg_(17)Al_(12)phases and grain refinement on machining characteristics are explained based on the tool wear mechanisms,chip behavior and machining induced affected zone.展开更多
In this study,we conduct an analysis of traversable wormhole solutions within the framework of linear f(Q,T)=αQ+βT gravity,ensuring that all energy conditions hold for the entire spacetime.The solutions presented in...In this study,we conduct an analysis of traversable wormhole solutions within the framework of linear f(Q,T)=αQ+βT gravity,ensuring that all energy conditions hold for the entire spacetime.The solutions presented in this paper are derived through a comprehensive analytical examination of the parameter space associated with the wormhole model.This involves considering the exponents governing the redshift and shape functions,as well as the radius of the wormhole throat(r_(0)),the redshift function value at the throat(∅_(0)),and the model parameters(αandβ).Moreover,we establish bounds on these free parameters,which guarantee the satisfaction of the energy conditions throughout spacetime and also provide two solutions.Furthermore,we use the Israel junction condition to observe the stability of a thin-shell around the wormhole.Finally,we calculate the null energy condition criteria as well as the potential for the thin-shell and how it varies with the chosen shape function.展开更多
Mg-4Zn-1RE-0.5Zr (ZE41) Mg alloy is extensively used in the aerospace and automobile industries.In order to improve the applicability and performance,this alloy was engineered with in-situ Ti B2reinforcement to form T...Mg-4Zn-1RE-0.5Zr (ZE41) Mg alloy is extensively used in the aerospace and automobile industries.In order to improve the applicability and performance,this alloy was engineered with in-situ Ti B2reinforcement to form Ti B2/ZE41 composite.The high temperature deformation behavior and manufacturability of the newly developed Ti B2/ZE41 composite and the parent ZE41 Mg alloy were studied via establishing constitutive modeling of flow stress,deformation activation energy and processing map over a temperature range of 250℃-450℃ and strain rate range of 0.001 s-1-10 s-1.The predicted flow stress behavior of both materials were found to be well consistent with the experimental values.A significant improvement in activation energy was found in Ti B2/ZE41 composite (171.54 k J/mol) as compared to the ZE41 alloy (148.15 k J/mol) due to the dispersed strengthening of in-situ Ti B2particles.The processing maps were developed via dynamic material modeling.A wider workability domain and higher peak efficiency (45%) were observed in Ti B2/ZE41 composite as compared to ZE41 alloy (41%).The Dynamic recrystallization is found to be the dominating deformation mechanism for both materials;however,particle stimulated nucleation was found to be an additional mode of deformation in Ti B2/ZE41 composite.The twinning and stress induced cracks were observed in both the materials at low temperature and high strain rate.A narrow range of instability zone is found in the present Ti B2/ZE41 composite among the existing published literature on Mg based composites.The detailed microstructural characterization was carried out in both workability and instability domains to establish the governing deformation mechanisms.展开更多
In this study, we explore the concept of cosmological inflation within the framework of the f(T, T)theory of gravity, where f is a general function of the torsion scalar T and the trace T of the energy-momentum tensor...In this study, we explore the concept of cosmological inflation within the framework of the f(T, T)theory of gravity, where f is a general function of the torsion scalar T and the trace T of the energy-momentum tensor.It is assumed that the conditions of slow-roll inflation are applicable in f(T, T) gravity. To determine different observables related to inflation, such as the tensor-to-scalar ratio r, scalar spectral index ns, spectral index αs, and tensor spectral index nt, the Hubble slow-roll parameters are utilized for a particular model of f(T, T). Lastly, an assessment is carried out to determine the feasibility of the models by conducting a numerical analysis of the parameters. The findings indicate that it is feasible to achieve compatibility with the observational measurements of slow-roll parameters by utilizing different values of the free parameters.展开更多
Nano-sized reinforcements improved the mechanical characteristics efficiently by promoting more implicit particle hardening mechanisms compared to micron-sized reinforcements.Nano-sized particles lessen the critical p...Nano-sized reinforcements improved the mechanical characteristics efficiently by promoting more implicit particle hardening mechanisms compared to micron-sized reinforcements.Nano-sized particles lessen the critical particle solidification velocity for swamp and thus offers better dispersal.In the present investigation,the friction stir processing(FSP)is utilized to produce AZ31/Al_(2)O_(3)nanocomposites at various tool rotation speeds(i.e.,900,1200,and 1500 rpm)with an optimized 1.5%volume alumina(Al_(2)O_(3))reinforcement ratio.The mechanical and corrosion behavior of AZ31/Al_(2)O_(3)-developed nanocomposites was investigated and compared with that of the AZ31 base alloy.The AZ31 alloy experienced a comprehensive dynamic recrystallization during FSP,causing substantial grain refinement.Grain-size strengthening is the primary factor contributed to the enhancement in the strength of the fabricated nanocomposite.Tensile strength and yield strength values were lower than those for the base metal matrix,although an upward trend in both values has been observed with an increase in tool rotation speed.An 19.72%increase in hardness along with superior corrosion resistance was achieved compared to the base alloy at a tool rotational speed of 1500 rpm.The corrosion currents(Jcorr)of all samples dropped with increase in the rotational speed,in contrast to the corrosion potentials(Ecorr),which increased.The values of Jcorr of AZ31/Al_(2)O_(3)were 42.3%,56.8%,and 65.5%lower than those of AZ31 alloy at the chosen rotating speeds of 900,1200,and 1500 rpm,respectively.The corrosion behavior of friction stir processed nanocomposites have been addressed in this manuscript which has not been given sufficient attention in the existing literature.Further,this work offers an effective choice for the quality assurance of the FSP process of AZ31/Al_(2)O_(3)nanocomposites.The obtained results are relevant to the development of lightweight automobile and aerospace structures and components.展开更多
The quality of coke affects the performance of the blast furnace, factors affecting coke quality include coal properties, coal charge granulometry and carbonization conditions. The coke properties in elude the size an...The quality of coke affects the performance of the blast furnace, factors affecting coke quality include coal properties, coal charge granulometry and carbonization conditions. The coke properties in elude the size analysis, cold strength (Micum Indices-M4(). MI0) and hot strength (Coke Reactivity Index-CRI, Coke Strength after Reaction-CSR) properties and structural properties such as coke structure and texture. Structural properties comprise the porosity, pore-cell wall thickness and pore sizes, while textures consist of the carbon forms in the coke. In present work, advanced method such as image analysis method was used to interpret coke microstructure. Conventional methods such as determination of coke porosity by measurement of real and apparent density and mercury porosimetry have a number of limitations. Coke size, magnification, number of image frames captured, process of pellet preparations and coke properties such as M4(), M|0, CRI and CSR (low, medium and high values) were taken as variables for experimental purposes. The coke structure parameters such as porosity, length, perimeter, breadth, roundness, pore-wall thickness and pore size distribution of the pores were determined by image analysis method. This method provided average porosity in addition to pore-wall thickness and pore-size distribution. The pore wall thickness measuremenl by image analysis method provided significant correlations with M40, CRI and CSR values. This explained the usability of image analysis for coke structure measurement.展开更多
In the present study,we investigate the anisotropic stellar solutions admitting Finch-Skea symmetry(viable and non-singular metric potentials)in the presence of some exotic matter fields,such as Bose-Einstein Condensa...In the present study,we investigate the anisotropic stellar solutions admitting Finch-Skea symmetry(viable and non-singular metric potentials)in the presence of some exotic matter fields,such as Bose-Einstein Condensate(BEC)dark matter,the Kalb-Ramond fully anisotropic rank-2 tensor field from the low-energy string theory effective action,and the gauge field imposing U(1)symmetry.Interior spacetime is matched with both Schwarzchild and Reissner-N?rdstrom vacuum spacetimes for BEC,KB,and gauge fields.In addition,we study the energy conditions,Equation of State(EoS),radial derivatives of energy density and anisotropic pressures,Tolman-OppenheimerVolkoff equilibrium condition,relativistic adiabatic index,sound speed,and surface redshift.Most of the aforementioned conditions are satisfied.Therefore,the solutions derived in the current study lie in the physically acceptable regime.展开更多
We present a novel gravastar model based on the Mazur-Mottola(2004)method with an isotropic matter distribution in f(Q)gravity.The gravastar,which is a hypothesized substitute for a black hole,is built using the Mazur...We present a novel gravastar model based on the Mazur-Mottola(2004)method with an isotropic matter distribution in f(Q)gravity.The gravastar,which is a hypothesized substitute for a black hole,is built using the Mazur-Mottola mechanism.This approach allows us to define the gravastar as having three stages.The first one is an inner region with negative pressure;the next region is a thin shell that is made up of ultrarelativistic stiff fluid,and we studied the proper length,energy,entropy,and surface energy density for this region.Additionally,we demonstrated the possible stability of our suggested thin shell gravastar model through the graphical study of the surface redshift.The exterior Schwarzschild geometry describes the outer region of the gravastar.In the context of f(Q)gravity,we discovered analytical solutions for the interior of gravastars that are free of any type of singularity and the event horizon.展开更多
In the last few decades,gravastars have been proposed as an alternative to black holes.The stability of a gravastar has been examined in many modified theories of gravity along with Einstein's GR.The f(Q,T)gravity...In the last few decades,gravastars have been proposed as an alternative to black holes.The stability of a gravastar has been examined in many modified theories of gravity along with Einstein's GR.The f(Q,T)gravity,a successfully modified theory of gravity for describing the current accelerated expansion of the universe,has been used in this study to examine gravastar in different aspects.According to Mazur and Mottola[Proc.Natl.Acad.Sci.101,9545(2004);Gravitational condensate stars:An alternative to black holes,I12-011,(2002)],a gravastar has three regions with three different equations of state.In this study,we examined the interior of a gravastar by consid-ering p=-ρ EoS to describe the dark sector for the interior region.The next region is a thin shell of ultrarelativistic stiff fluid,in which we investigated several physical properties,including proper length,energy,entropy,and surface energy density.Additionally,we examined the surface redshift and speed of sound to check the potential stability of our proposed thin-shell gravastar model.Furthermore,we used the entropy maximization technique to verify the stability of the gravastar model.A gravastar's outer region is a complete vacuum described by exterior Schwarzschild geometry.Finally,we presented a stable gravastar model,which is singularity-free and devoid of any incom-pleteness in classical black hole theory.展开更多
Detailed experimental investigations were carried out for microwave pre-treatment of high ash Indian coal at high power level(900 W) in microwave oven. The microwave exposure times were fixed at60 s and 120 s. A rheol...Detailed experimental investigations were carried out for microwave pre-treatment of high ash Indian coal at high power level(900 W) in microwave oven. The microwave exposure times were fixed at60 s and 120 s. A rheology characteristic for microwave pre-treatment of coal-water slurry(CWS) was performed in an online Bohlin viscometer. The non-Newtonian character of the slurry follows the rheological model of Ostwald de Waele. The values of n and k vary from 0.31 to 0.64 and 0.19 to 0.81 Pa·sn,respectively. This paper presents an artificial neural network(ANN) model to predict the effects of operational parameters on apparent viscosity of CWS. A 4-2-1 topology with Levenberg-Marquardt training algorithm(trainlm) was selected as the controlled ANN. Mean squared error(MSE) of 0.002 and coefficient of multiple determinations(R^2) of 0.99 were obtained for the outperforming model. The promising values of correlation coefficient further confirm the robustness and satisfactory performance of the proposed ANN model.展开更多
In this study,we obtain wormhole solutions in the recently proposed extension of symmetric teleparallel gravity,known as f(Q,T)gravity.Here,the gravitational Lagrangian L is defined by an arbitrary function f of Q and...In this study,we obtain wormhole solutions in the recently proposed extension of symmetric teleparallel gravity,known as f(Q,T)gravity.Here,the gravitational Lagrangian L is defined by an arbitrary function f of Q and T,where Q is a non-metricity scalar,and T is the trace of the energy-momentum tensor.In this study,we obtain field equations for a static spherically symmetric wormhole metric in the context of general f(Q,T)gravity.We study the wormhole solutions using(ⅰ)a linear equation of state and(ⅱ)an anisotropy relation.We adopt two different forms of f(Q,T),(a)linear f(Q,T)=αQ+βT and(b)non-linear f(Q,T)=Q+λQ^(2)+ηT,to investigate these solutions.We investigate various energy conditions to search for preservation and violation among the obtained solutions and find that the null energy condition is violated in both cases of our assumed forms of f(Q,T).Finally,we perform a stability analysis using the Tolman-Oppenheimer-Volkov equation.展开更多
In this paper, we determine the general solution of the functional equation f1 （2x ＋ y） ＋ f2（2x - y） = f3（x ＋ y） ＋ f4（x - y） ＋ f5（x） without assuming any regularity condition on the unknown functions f1...In this paper, we determine the general solution of the functional equation f1 （2x ＋ y） ＋ f2（2x - y） = f3（x ＋ y） ＋ f4（x - y） ＋ f5（x） without assuming any regularity condition on the unknown functions f1,f2,f3, f4, f5 ： R→R. The general solution of this equation is obtained by finding the general solution of the functional equations f（2x ＋ y） ＋ f（2x - y） = g（x ＋ y） ＋ g（x - y） ＋ h（x） and f（2x ＋ y） - f（2x - y） = g（x ＋ y） - g（x - y）. The method used for solving these functional equations is elementary but exploits an important result due to Hosszfi. The solution of this functional equation can also be determined in certain type of groups using two important results due to Szekelyhidi.展开更多
基金the Science and Engineering Research Board(SERB)Department of Science and Technology(DST)Government of India(FILE EMR/2016/007046)。
文摘This research article mainly reports on the precise structural,optical,and photocatalytic properties of cerium(Ce)-substituted yttrium manganite(YMnO_(3))nanoparticles synthesized by the polyacrylamide gel method.The characteristics of YMnO_(3)were investigated by the substitution of Ce into the Y site at various molar percentages.The Raman and X-ray diffraction(XRD)analyses confirmed the pure phase of hexagonal YMnO_(3),supported by the Rietveld refinement.The microstructural studies indicate inhomogeneous and irregular particle distribution.The X-ray photoelectron spectroscopy(XPS)results show the presence of two ionic states of Mn and Ce along with Y^(3+)state and oxygen vacancies.Extensive optical exploration using photoluminescence(PL)spectroscopy and UV-Vis-NIR analysis indicates that the intensity of absorption peak increases in the visible region,while the bandgap decreases from 1.42 to1.30 eV with the Ce ion doping(5 mol%-15 mol%).Photocatalytic properties of the polycrystalline nanoparticles were investigated by degradation of the pollutant 4-nitrophenol.The process of amplified photocatalysis process was elucidated by the lowered bandgap and rate of charge carrier recombination.It can be conjugated from this study that the synthesized nanoparticles may be employed as highly efficient(92.8%)visible light-triggered photocatalysts in a variety of real-world applications.
基金supported by Sustainable Technologies for the Utilisation of Rare Earths(SURE),CSC-0132 supported by CSIR,India
文摘The recycling of rare earth elements（REE） from end-of-life REE based products is an environment friendly proposition. Waste Sm-Co based permanent magnet generated during machining is a good source for both Sm and Co. In the present study a simpler process of acid leaching at 80 ℃ followed by solvent extraction, oxalate precipitation and calcination is described for producing pure Sm2 O3 and Co3 O4. With either 10 vol% H2SO4 or 15 vol% HCI at 80 ℃ more than 95% Sm and Co are leached in 1 h.Extraction of Sm from sulphate leach liquor with TBP or Aliquat 336 was poor. Although extraction with TOPS-99 is quantitative but Sm from sulphate leach liquor precipitated as Sm2（SO4）3·8 H2O. The chloride leach liquor at an initial pH of 2.5 and with 1.2 mol/L TOPS-99 shows requirement of 4-stages at A：O = 3：2. Stripping with oxalic acid precipitates Sm-oxalate which is calcined at 800 ℃ to produce Sm2 O3. Co3 O4 is recovered from the raffinate through oxalate precipitation followed by calcination at450℃.
文摘In the nonparametric data envelopment analysis literature,scale elasticity is evaluated in two alternative ways:using either the technical efficiency model or the cost efficiency model.This evaluation becomes problematic in several situations,for example(a)when input proportions change in the long run,(b)when inputs are heterogeneous,and(c)when firms face ex-ante price uncertainty in making their production decisions.To address these situations,a scale elasticity evaluation was performed using a value-based cost efficiency model.However,this alternative value-based scale elasticity evaluation is sensitive to the uncertainty and variability underlying input and output data.Therefore,in this study,we introduce a stochastic cost-efficiency model based on chance-constrained programming to develop a value-based measure of the scale elasticity of firms facing data uncertainty.An illustrative empirical application to the Indian banking industry comprising 71 banks for eight years(1998–2005)was made to compare inferences about their efficiency and scale properties.The key findings are as follows:First,both the deterministic model and our proposed stochastic model yield distinctly different results concerning the efficiency and scale elasticity scores at various tolerance levels of chance constraints.However,both models yield the same results at a tolerance level of 0.5,implying that the deterministic model is a special case of the stochastic model in that it reveals the same efficiency and returns to scale characterizations of banks.Second,the stochastic model generates higher efficiency scores for inefficient banks than its deterministic counterpart.Third,public banks exhibit higher efficiency than private and foreign banks.Finally,public and old private banks mostly exhibit either decreasing or constant returns to scale,whereas foreign and new private banks experience either increasing or decreasing returns to scale.Although the application of our proposed stochastic model is illustrative,it can be potentially applie
文摘Objective:To surveill emerging variants by nanopore technology-based genome sequencing in different COVID-19 waves in Sri Lanka and to examine the association with the sample characteristics,and vaccination status.Methods:The study analyzed 207 RNA positive swab samples received to sequence laboratory during different waves.The N gene cut-off threshold of less than 30 was considered as the major inclusion criteria.Viral RNA was extracted,and elutes were subjected to nanopore sequencing.All the sequencing data were uploaded in the publicly accessible database,GISAID.Results:The Omicron,Delta and Alpha variants accounted for 58%,22%and 4%of the variants throughout the period.Less than 1%were Kappa variant and 16%of the study samples remained unassigned.Omicron variant was circulated among all age groups and in all the provinces.Ct value and variants assigned percentage was 100%in Ct values of 10-15 while only 45%assigned Ct value over 25.Conclusions:The present study examined the emergence,prevalence,and distribution of SARS-CoV-2 variants locally and has shown that nanopore technology-based genome sequencing enables whole genome sequencing in a low resource setting country.
文摘Functionalized single-walled carbon nanotubes(f-SWCNTs)hybridized with freshly prepared zinc oxide(ZnO)nanocrystals have been found to be good luminescent material with tuned emission properties.A three-phase nanocomposite of sulfonated polyaniline embedded with such SWCNT/ZnO nanostructures has been prepared by a simple solution mixing chemical process and characterized by using high-resolution transmission electron microscopy,X-ray diffractometry,Raman spectroscopy,Fourier transform infrared spectroscopy,and thermogravimetric analysis.The study of UVvisible absorption and photoluminescence spectroscopies reveal that the ternary polymer nanocomposite is a luminescent material with enhanced emission intensity.Also an increase in DC conductivity indicates that the nanocomposite is also a good conductive material,satisfying Mott’s variable range hopping model for a two-dimensional conduction.Such a three-phase nanocomposite may find extensive application in dye-sensitized solar cells,sensors,and supercapacitors.
基金National Aluminium Company (NALCO) for financial support
文摘An approach was developed to upgrade the bauxite ore by molecular hydrogen and hydrogen plasma. A gibbsite-type bauxite sample was obtained from National Aluminium Company（NALCO）, Odisha, India. The obtained sample was crushed and sieved（to 100 μm） prior to the chemical analysis and grain-size distribution study. The bauxite sample was calcined in the temperature range from 500 to 700°C for different time intervals to optimize the conditions for maximum moisture removal. This process was followed by the reduction of the calcined ore by molecular hydrogen and hydrogen plasma. Extraction of alumina from the reduced ore was carried out via acid leaching in chloride media for 2 h at 60°C. X-ray diffraction, scanning electron microscopy, thermogravimetry in conjunction with differential scanning calorimetry, and Fourier transform infrared spectroscopy were used to determine the physicochemical characteristics of the material before and after extraction. Alumina extracted from the reduced ore at the optimum calcination temperature of 700°C and the optimum calcination time of 4 h is found to be 90% pure.
文摘Nano-sized polyacrylonitrile （PAN） particles were prepared under the catalytic effect of in situ developed CoCl2/EDTA complex with ammonium persulfate as the initiator in the absence of any added emulsifier. The emulsion polymerization was studied at varying concentrations of the initiator, monomer, complex and solvent over a temperature range of 30-70℃. The overall activation energy （Ea, 49.79 kJ/mol）, energy of dissociation of initiator （Ed, 82.68 kJ/mol）, number of micelles （0.163 × 10^18） and the viscosity average molecular weight of the polymer were computed. The distribution of particle sizes was determined by transmission electron microscopy （TEM）. It was found that the oil-in-water polymerization was stabilized by the presence of the CoCl2/EDTA in situ complex reducing the particle size into the nano order. The average diameters of PAN nano particles, obtained by TEM, were in the range of 50-150 nm at the maximum conversion. The experimental particle size was mainly dependent on the concentration of the complex and temperature.
基金the Ministry of Human Resource and Development for funding this Co E through Grant No.-SB20210992MEMHRD008517the support of the FIST grant,Department of Science and Technology,India(Grant#SR/FST/ET11059/2012(G))for the use of the electron microscopy facility
文摘Magnesium and magnesium in-situ composites have significant potential in the application of design and manufacturing for automotive and aerospace industries because of their high specific strength and reduced fuel consumption.But there are many challenges for machining of Mg based alloys and composites because of the high tendency of fire and oxidation.These challenges can be minimized through microstructural engineering.In this present study,the machining performances of AZ91 Mg alloy and in-situ hybrid TiC+TiB_(2)reinforced AZ91 metal matrix composite was investigated.The effectβ-Mg_(17)Al_(12)phases and grain refinement with and without in-situ particles on machinability were studied through microstructural engineering via aging and friction stir processing.The end milling operation was carried out at different cutting speeds ranging from 25 mm/min to 90 mm/min under dry environment by using an AlTiN-coated tungsten carbide tool.The optimum cutting speed for machining was found to be 75 mm/min based on the surface roughness values of all conditioned materials.The base material with dendritic microstructure was found to have poor machinability in terms of inadequate surface finish and edge-burrs formation.The combined effect of in-situ TiC+TiB_(2)particles addition and grain refinement enhanced the machining performance of the material with superior surface finish,negligible edge-burr formation and better tool wear resistance.The influence of in-situ TiC+TiB_(2)particles,β-Mg_(17)Al_(12)phases and grain refinement on machining characteristics are explained based on the tool wear mechanisms,chip behavior and machining induced affected zone.
基金supported by the University Grants Commission(UGC),New Delhi,India,for awarding National Fellowship for Scheduled Caste Students(UGC-Ref.No.201610123801)supported by the Council of Scientific and Industrial Research(CSIR),Government of India,New Delhi,for junior research fellowship(File No.09/1026(13105)/2022-EMR-I)supported by the National Board for Higher Mathematics(NBHM)under the Department of Atomic Energy(DAE),Govt.of India for financial support to carry out the research project(No.02011/3/2022 NBHM(R.P.)/R&D II/2152 Dt.14.02.2022)
文摘In this study,we conduct an analysis of traversable wormhole solutions within the framework of linear f(Q,T)=αQ+βT gravity,ensuring that all energy conditions hold for the entire spacetime.The solutions presented in this paper are derived through a comprehensive analytical examination of the parameter space associated with the wormhole model.This involves considering the exponents governing the redshift and shape functions,as well as the radius of the wormhole throat(r_(0)),the redshift function value at the throat(∅_(0)),and the model parameters(αandβ).Moreover,we establish bounds on these free parameters,which guarantee the satisfaction of the energy conditions throughout spacetime and also provide two solutions.Furthermore,we use the Israel junction condition to observe the stability of a thin-shell around the wormhole.Finally,we calculate the null energy condition criteria as well as the potential for the thin-shell and how it varies with the chosen shape function.
基金Department of Science and Technology, India [grant number of DST/TDT/AMT/ 2017/211(G)] (MEE/18–19/412/DSTX/SUSH) for the financial support and FIST grant, Department of Science and Technology, India [grant number SR/FST/ET11–059/2012 (G)] for funding electron microscope facilitya part of Center of Excellence (Co E) in Applied Magnesium Research (A Vertical of Center for Materials and Manufacturing for Futuristic Mobility), IIT Madrasthe Ministry of Human Resource and Development for funding this CoE through grant number–SB20210992MEMHRD008517。
文摘Mg-4Zn-1RE-0.5Zr (ZE41) Mg alloy is extensively used in the aerospace and automobile industries.In order to improve the applicability and performance,this alloy was engineered with in-situ Ti B2reinforcement to form Ti B2/ZE41 composite.The high temperature deformation behavior and manufacturability of the newly developed Ti B2/ZE41 composite and the parent ZE41 Mg alloy were studied via establishing constitutive modeling of flow stress,deformation activation energy and processing map over a temperature range of 250℃-450℃ and strain rate range of 0.001 s-1-10 s-1.The predicted flow stress behavior of both materials were found to be well consistent with the experimental values.A significant improvement in activation energy was found in Ti B2/ZE41 composite (171.54 k J/mol) as compared to the ZE41 alloy (148.15 k J/mol) due to the dispersed strengthening of in-situ Ti B2particles.The processing maps were developed via dynamic material modeling.A wider workability domain and higher peak efficiency (45%) were observed in Ti B2/ZE41 composite as compared to ZE41 alloy (41%).The Dynamic recrystallization is found to be the dominating deformation mechanism for both materials;however,particle stimulated nucleation was found to be an additional mode of deformation in Ti B2/ZE41 composite.The twinning and stress induced cracks were observed in both the materials at low temperature and high strain rate.A narrow range of instability zone is found in the present Ti B2/ZE41 composite among the existing published literature on Mg based composites.The detailed microstructural characterization was carried out in both workability and instability domains to establish the governing deformation mechanisms.
基金the Science and Engineering Research Board,Department of Science and Technology,Government of India for financial support to carry out research project No.:CRG/2022/001847 and IUCAA。
文摘In this study, we explore the concept of cosmological inflation within the framework of the f(T, T)theory of gravity, where f is a general function of the torsion scalar T and the trace T of the energy-momentum tensor.It is assumed that the conditions of slow-roll inflation are applicable in f(T, T) gravity. To determine different observables related to inflation, such as the tensor-to-scalar ratio r, scalar spectral index ns, spectral index αs, and tensor spectral index nt, the Hubble slow-roll parameters are utilized for a particular model of f(T, T). Lastly, an assessment is carried out to determine the feasibility of the models by conducting a numerical analysis of the parameters. The findings indicate that it is feasible to achieve compatibility with the observational measurements of slow-roll parameters by utilizing different values of the free parameters.
文摘Nano-sized reinforcements improved the mechanical characteristics efficiently by promoting more implicit particle hardening mechanisms compared to micron-sized reinforcements.Nano-sized particles lessen the critical particle solidification velocity for swamp and thus offers better dispersal.In the present investigation,the friction stir processing(FSP)is utilized to produce AZ31/Al_(2)O_(3)nanocomposites at various tool rotation speeds(i.e.,900,1200,and 1500 rpm)with an optimized 1.5%volume alumina(Al_(2)O_(3))reinforcement ratio.The mechanical and corrosion behavior of AZ31/Al_(2)O_(3)-developed nanocomposites was investigated and compared with that of the AZ31 base alloy.The AZ31 alloy experienced a comprehensive dynamic recrystallization during FSP,causing substantial grain refinement.Grain-size strengthening is the primary factor contributed to the enhancement in the strength of the fabricated nanocomposite.Tensile strength and yield strength values were lower than those for the base metal matrix,although an upward trend in both values has been observed with an increase in tool rotation speed.An 19.72%increase in hardness along with superior corrosion resistance was achieved compared to the base alloy at a tool rotational speed of 1500 rpm.The corrosion currents(Jcorr)of all samples dropped with increase in the rotational speed,in contrast to the corrosion potentials(Ecorr),which increased.The values of Jcorr of AZ31/Al_(2)O_(3)were 42.3%,56.8%,and 65.5%lower than those of AZ31 alloy at the chosen rotating speeds of 900,1200,and 1500 rpm,respectively.The corrosion behavior of friction stir processed nanocomposites have been addressed in this manuscript which has not been given sufficient attention in the existing literature.Further,this work offers an effective choice for the quality assurance of the FSP process of AZ31/Al_(2)O_(3)nanocomposites.The obtained results are relevant to the development of lightweight automobile and aerospace structures and components.
文摘The quality of coke affects the performance of the blast furnace, factors affecting coke quality include coal properties, coal charge granulometry and carbonization conditions. The coke properties in elude the size analysis, cold strength (Micum Indices-M4(). MI0) and hot strength (Coke Reactivity Index-CRI, Coke Strength after Reaction-CSR) properties and structural properties such as coke structure and texture. Structural properties comprise the porosity, pore-cell wall thickness and pore sizes, while textures consist of the carbon forms in the coke. In present work, advanced method such as image analysis method was used to interpret coke microstructure. Conventional methods such as determination of coke porosity by measurement of real and apparent density and mercury porosimetry have a number of limitations. Coke size, magnification, number of image frames captured, process of pellet preparations and coke properties such as M4(), M|0, CRI and CSR (low, medium and high values) were taken as variables for experimental purposes. The coke structure parameters such as porosity, length, perimeter, breadth, roundness, pore-wall thickness and pore size distribution of the pores were determined by image analysis method. This method provided average porosity in addition to pore-wall thickness and pore-size distribution. The pore wall thickness measuremenl by image analysis method provided significant correlations with M40, CRI and CSR values. This explained the usability of image analysis for coke structure measurement.
基金National Board for Higher Mathematics(NBHM)under Department of Atomic Energy(DAE)Govt.of India for financial support to carry out the Research project No.:02011/3/2022 NBHM(R.P.)/R#D II/2152 Dt.14.02.2022Sokoliuk O.performed the work in frame of the"Mathematical modeling in interdisciplinary research of processes and systems based on intelligent supercomputer,grid and cloud technologies"program of the NAS of Ukraine。
文摘In the present study,we investigate the anisotropic stellar solutions admitting Finch-Skea symmetry(viable and non-singular metric potentials)in the presence of some exotic matter fields,such as Bose-Einstein Condensate(BEC)dark matter,the Kalb-Ramond fully anisotropic rank-2 tensor field from the low-energy string theory effective action,and the gauge field imposing U(1)symmetry.Interior spacetime is matched with both Schwarzchild and Reissner-N?rdstrom vacuum spacetimes for BEC,KB,and gauge fields.In addition,we study the energy conditions,Equation of State(EoS),radial derivatives of energy density and anisotropic pressures,Tolman-OppenheimerVolkoff equilibrium condition,relativistic adiabatic index,sound speed,and surface redshift.Most of the aforementioned conditions are satisfied.Therefore,the solutions derived in the current study lie in the physically acceptable regime.
基金the National Board for Higher Mathematics (NBHM) under the Department of Atomic Energy (DAE) of the government of India for financial support to carry out the research project (02011/3/2022 NBHM(R.P.)/R&D Ⅱ/2152 Dt.14.02.2022)
文摘We present a novel gravastar model based on the Mazur-Mottola(2004)method with an isotropic matter distribution in f(Q)gravity.The gravastar,which is a hypothesized substitute for a black hole,is built using the Mazur-Mottola mechanism.This approach allows us to define the gravastar as having three stages.The first one is an inner region with negative pressure;the next region is a thin shell that is made up of ultrarelativistic stiff fluid,and we studied the proper length,energy,entropy,and surface energy density for this region.Additionally,we demonstrated the possible stability of our suggested thin shell gravastar model through the graphical study of the surface redshift.The exterior Schwarzschild geometry describes the outer region of the gravastar.In the context of f(Q)gravity,we discovered analytical solutions for the interior of gravastars that are free of any type of singularity and the event horizon.
基金SP&PKS acknowledges the National Board for Higher Mathematics(NBHM)under the Department of Atomic Energy(DAE),Govt.of India for financial support to carry out the Research project No.:02011/3/2022 NBHM(R.P.)/R&D II/2152 Dt.14.02.2022.PKS thanks Transilvania University of Brasov for Transilvania Fellowship for Visiting Professors。
文摘In the last few decades,gravastars have been proposed as an alternative to black holes.The stability of a gravastar has been examined in many modified theories of gravity along with Einstein's GR.The f(Q,T)gravity,a successfully modified theory of gravity for describing the current accelerated expansion of the universe,has been used in this study to examine gravastar in different aspects.According to Mazur and Mottola[Proc.Natl.Acad.Sci.101,9545(2004);Gravitational condensate stars:An alternative to black holes,I12-011,(2002)],a gravastar has three regions with three different equations of state.In this study,we examined the interior of a gravastar by consid-ering p=-ρ EoS to describe the dark sector for the interior region.The next region is a thin shell of ultrarelativistic stiff fluid,in which we investigated several physical properties,including proper length,energy,entropy,and surface energy density.Additionally,we examined the surface redshift and speed of sound to check the potential stability of our proposed thin-shell gravastar model.Furthermore,we used the entropy maximization technique to verify the stability of the gravastar model.A gravastar's outer region is a complete vacuum described by exterior Schwarzschild geometry.Finally,we presented a stable gravastar model,which is singularity-free and devoid of any incom-pleteness in classical black hole theory.
基金the sponsor CSIR (Council of Scientific and Industrial Research), New Delhi for their financial grant to carry out the present research work
文摘Detailed experimental investigations were carried out for microwave pre-treatment of high ash Indian coal at high power level(900 W) in microwave oven. The microwave exposure times were fixed at60 s and 120 s. A rheology characteristic for microwave pre-treatment of coal-water slurry(CWS) was performed in an online Bohlin viscometer. The non-Newtonian character of the slurry follows the rheological model of Ostwald de Waele. The values of n and k vary from 0.31 to 0.64 and 0.19 to 0.81 Pa·sn,respectively. This paper presents an artificial neural network(ANN) model to predict the effects of operational parameters on apparent viscosity of CWS. A 4-2-1 topology with Levenberg-Marquardt training algorithm(trainlm) was selected as the controlled ANN. Mean squared error(MSE) of 0.002 and coefficient of multiple determinations(R^2) of 0.99 were obtained for the outperforming model. The promising values of correlation coefficient further confirm the robustness and satisfactory performance of the proposed ANN model.
基金University Grants Commission(UGC),New Delhi,India,for awarding National Fellowship for Scheduled Caste Students(UGC-Ref.No.:201610123801)the Department of Science and Technology(DST),Government of India,New Delhi,for awarding a Senior Research Fellowship(File No.DST/INSPIRE Fellowship/2019/IF190911)National Board for Higher Mathematics(NBHM)under Department of Atomic Energy(DAE),Govt.of India for financial support to carry out the Research project No.:02011/3/2022 NBHM(R.P.)/R&D II/2152 Dt.14.02.2022。
文摘In this study,we obtain wormhole solutions in the recently proposed extension of symmetric teleparallel gravity,known as f(Q,T)gravity.Here,the gravitational Lagrangian L is defined by an arbitrary function f of Q and T,where Q is a non-metricity scalar,and T is the trace of the energy-momentum tensor.In this study,we obtain field equations for a static spherically symmetric wormhole metric in the context of general f(Q,T)gravity.We study the wormhole solutions using(ⅰ)a linear equation of state and(ⅱ)an anisotropy relation.We adopt two different forms of f(Q,T),(a)linear f(Q,T)=αQ+βT and(b)non-linear f(Q,T)=Q+λQ^(2)+ηT,to investigate these solutions.We investigate various energy conditions to search for preservation and violation among the obtained solutions and find that the null energy condition is violated in both cases of our assumed forms of f(Q,T).Finally,we perform a stability analysis using the Tolman-Oppenheimer-Volkov equation.
文摘In this paper, we determine the general solution of the functional equation f1 （2x ＋ y） ＋ f2（2x - y） = f3（x ＋ y） ＋ f4（x - y） ＋ f5（x） without assuming any regularity condition on the unknown functions f1,f2,f3, f4, f5 ： R→R. The general solution of this equation is obtained by finding the general solution of the functional equations f（2x ＋ y） ＋ f（2x - y） = g（x ＋ y） ＋ g（x - y） ＋ h（x） and f（2x ＋ y） - f（2x - y） = g（x ＋ y） - g（x - y）. The method used for solving these functional equations is elementary but exploits an important result due to Hosszfi. The solution of this functional equation can also be determined in certain type of groups using two important results due to Szekelyhidi.
