This article studies the existence and uniqueness of the mild solution of a family of control systems with a delay that are governed by the nonlinear fractional evolution differential equations in Banach spaces.Moreov...This article studies the existence and uniqueness of the mild solution of a family of control systems with a delay that are governed by the nonlinear fractional evolution differential equations in Banach spaces.Moreover,we establish the controllability of the considered system.To do so,first,we investigate the approximate controllability of the corresponding linear system.Subsequently,we prove the nonlinear system is approximately controllable if the corresponding linear system is approximately controllable.To reach the conclusions,the theory of resolvent operators,the Banach contraction mapping principle,and fixed point theorems are used.While concluding,some examples are given to demonstrate the efficacy of the proposed results.展开更多
The rapid industrial growth and increasing population have led to significant pollution and deterioration of the natural atmospheric environment.Major atmospheric pollutants include NO_(2)and CO_(2).Hence,it is impera...The rapid industrial growth and increasing population have led to significant pollution and deterioration of the natural atmospheric environment.Major atmospheric pollutants include NO_(2)and CO_(2).Hence,it is imperative to develop NO_(2)and CO_(2)sensors for ambient conditions,that can be used in indoor air quality monitoring,breath analysis,food spoilage detection,etc.In the present study,two thin film nanocomposite(nickel oxide-graphene and nickel oxide-silver nanowires)gas sensors are fabricated using direct ink writing.The nano-composites are investigated for their structural,optical,and electrical properties.Later the nano-composite is deposited on the interdigitated electrode(IDE)pattern to form NO_(2)and CO_(2)sensors.The deposited films are then exposed to NO_(2)and CO_(2)gases separately and their response and recovery times are determined using a custom-built gas sensing setup.Nickel oxide-graphene provides a good response time and recovery time of 10 and 9 s,respectively for NO_(2),due to the higher electron affinity of graphene towards NO_(2).Nickel oxide-silver nanowire nano-composite is suited for CO_(2)gas because silver is an excellent electrocatalyst for CO_(2)by giving response and recovery times of 11 s each.This is the first report showcasing NiO nano-composites for NO_(2)and CO_(2)sensing at room temperature.展开更多
Fifty-seven bacteria were isolated from Southern Ocean （Indian sector） water samples which were collected from different latitude and longitude of the ocean. All the isolates were able to grow at 4℃, 20℃, 37℃ and...Fifty-seven bacteria were isolated from Southern Ocean （Indian sector） water samples which were collected from different latitude and longitude of the ocean. All the isolates were able to grow at 4℃, 20℃, 37℃ and tolerable NaCI concentration up to 13.5% （w/v）. 29 out of 57 isolates were identified using 16S rDNA amplification and the sequences were submitted to National Center for Biotechnology Information （NCBI）. All the isolates were classified by using Ribosomal Database Project （RDP） and found that isolates belongs to Proteobacteria and Bacteriodes. The average G＋C content was 56.4%. The isolates were screened for the presence of extracellular enzymes, viz. amylase, catalase, urease, esterase, lipase and protease. The disc diffusion method is used to screen antibiotic production by the isolates against four pathogenic bacteria, viz. Salmonella typhimurium （NCIM 2501）, Staphylococcus aureus （NCIM 2122）, Bacillus subtilis （NCIM 2193）, and Pseudomonas aeruginosa （NCIM 2036）. Nine out of 29 were found to be antibiotic producer.展开更多
A Shape Memory Polymer Composite(SMPC)is developed by reinforcing an epoxy-based polymer with randomly oriented short glass fibers.Diverging from previous research,which primarily focused on the hot programming of sho...A Shape Memory Polymer Composite(SMPC)is developed by reinforcing an epoxy-based polymer with randomly oriented short glass fibers.Diverging from previous research,which primarily focused on the hot programming of short glass fiber-based SMPCs,this work explores the potential for programming below the glass transition temperature(Tg)for epoxy-based SMPCs.To mitigate the inherent brittleness of the SMPC during deformation,a linear polymer is incorporated,and a temperature between room temperature and Tg is chosen as the deformation temperature to study the shape memory properties.The findings demonstrate an enhancement in shape fixity and recovery stress,alongside a reduction in shape recovery,with the incorporation of short glass fibers.In addition to tensile properties,thermal properties such as thermal conductivity,specific heat capacity,and glass transition temperature are investigated for their dependence on fiber content.Microscopic properties,such as fiber-matrix adhesion and the dispersion of glass fibers,are examined through Scanning Electron Microscope imaging.The fiber length distribution and mean fiber lengths are also measured for different fiber fractions.展开更多
Understanding and controlling fracture propagation is one of the most challenging engineering problems,especially in the oil and gas sector,groundwater hydrology,and geothermal energy applications.Predicting fracture ...Understanding and controlling fracture propagation is one of the most challenging engineering problems,especially in the oil and gas sector,groundwater hydrology,and geothermal energy applications.Predicting fracture orientation while possessing a nonlinear material response becomes more complex when the medium is subjected to anisotropic boundary stresses.Furthermore,the fracturing behaviour of geological porous media that exhibit high leak-off potential is not clearly understood.In this context,a novel testing technique is used to simulate in situ conditions in the laboratory and to study the instability characteristics of such geomaterials.The bespoke apparatus designed and developed in this research programme is capable of applying true anisotropic boundary stresses,injecting fluid at a predefined flow rate and viscosity while imaging instability/fracture propagation in a porous medium such as sand and bio-cemented sands.Pressure profiles and fracture propagation are simultaneously recorded during fluid injection into specimens subjected to different boundary stresses.Analysis of the images obtained during the fluid injection process provides information on the evolution of infiltration and fracture area during the injection event.The quantification of pressure and the corresponding fracture signature is,therefore,useful for a comprehensive understanding of the mechanics of fluid-induced fracture propagation.展开更多
Heat treatments play a crucial role in enhancing the mechanical properties of AZ91 Mg alloy by dissolving coarse phases during solution treatment and promoting precipitation during aging.However,non-uniform microstruc...Heat treatments play a crucial role in enhancing the mechanical properties of AZ91 Mg alloy by dissolving coarse phases during solution treatment and promoting precipitation during aging.However,non-uniform microstructures and coarse secondary phases in conventional casting methods hinder the effectiveness of these treatments,leading to reduced ductility,inconsistent properties,and prolonged durations.To overcome these challenges,this study introduces the Strain Integrated Gas-Infusion(SIGI)casting process that integrates strain and gas infusion in the semi-solid state.The impact of the SIGI process on the solution treatment and aging kinetics of AZ91 Mg alloy is explored.The SIGI process refinesα-Mg andβ-Mg_(17)Al_(12)phases,significantly enhancing mechanical properties.Experimental and quantitative analyses reveal that the SIGI process accelerates solute atom dissolution,reducing solution treatment times by half,and promotes faster nucleation and growth of precipitates during aging,shortening aging times by one-third.These improvements result in substantial gains in ultimate tensile strength(~40-50%)and ductility(~20-30%)after age hardening compared to conventional casting.The mechanisms driving these changes,including enhanced nucleation rates,reduced diffusion distances,and microstructural refinement,are discussed.These findings demonstrate the potential of the SIGI casting process to advance magnesium alloy performance for engineering applications.展开更多
Biochar is a carbon sink material with the potential to improve water retention in various soils.However,for the long‐term maintenance of green infrastructure,there is an additional need to regulate the water content...Biochar is a carbon sink material with the potential to improve water retention in various soils.However,for the long‐term maintenance of green infrastructure,there is an additional need to regulate the water contents in the covers to maintain vegetation growth in semiarid conditions.In this study,biochar‐amended soil was combined with subsurface drip irrigation,and the water preservation characteristics of this treatment were investigated through a series of one‐dimensional soil column tests.To ascertain the best treatment method specific to semiarid climatic conditions,the test soil was amended with 0%,1%,3%,and 5%biochar.Automatic irrigation devices equipped with soil moisture sensors were used to control the subsurface water content with the aim of enhancing vegetation growth.Each soil column test lasted 150 h,during which the volumetric water contents and soil suction data were recorded.The experimental results reveal that the soil specimen amended with 3%biochar is the most water‐saving regardless of the time cost.Soil with a higher biochar content(e.g.,5%)consumes a more significant amount of water due to the enhancement of the water‐holding capacity.Based on the experimental results,it can be concluded that the appropriate ratio can be determined within 1%–3%,which can reduce not only the amount of irrigated/used water but also the time cost.Such technology can be explored for water content regulation in green infrastructure and the development of barriers for protecting the environment around deep underground waste containment.展开更多
Quantification of seismic activity is one of the most challenging problems faced by earthquake engineers in probabilistic seismic hazard analysis. Currently, this problem has been attempted using empirical approaches ...Quantification of seismic activity is one of the most challenging problems faced by earthquake engineers in probabilistic seismic hazard analysis. Currently, this problem has been attempted using empirical approaches which are based on the regional earthquake recurrence relations from the available earth- quake catalogue. However, at a specified site of engineering interest, these empirical models are asso- ciated with large number of uncertainties due to lack of sufficient data. Due to these uncertainties, engineers need to develop mechanistic models to quantify seismic activity. A wide range of techniques for modeling continental plates provides useful insights on the mechanics of plates and their seismic activity. Among the different continental plates, the Indian plate experiences diffused seismicity. In India, although Himalaya is regarded as a plate boundary and active region, the seismicity database indicates that there are other regions in the Indian shield reporting sporadic seismic activity. It is expected that mechanistic models of Indian plate, based on finite element method, simulate stress fields that quantify the seismic potential of active regions in India, This article explores the development of a finite element model for Indian plate by observing the simulated stress field for various boundary conditions, geological and theological conditions. The study observes that the magnitude and direction of stresses in the plate is sensitive to these conditions, The numerical analysis of the models shows that the simulated stress field represents the active seismic zones in India.展开更多
Volatile organic compounds(VOC's) in air have become major concern in recent years. Biodegradation of a mixture of ethanol and methanol vapor was evaluated in a laboratory biofilter with a bed of compost and polys...Volatile organic compounds(VOC's) in air have become major concern in recent years. Biodegradation of a mixture of ethanol and methanol vapor was evaluated in a laboratory biofilter with a bed of compost and polystyrene particles using an acclimated mixed culture. The continuous performance of the biofilter was studied with different proportion of ethanol and methanol at different initial concentration and flow rates. The result showed significant removal for both ethanol and methanol, which were composition dependent. The presence of either compound in the mixture inhibited the biodegradation of the other.展开更多
In the present study,AZ31 magnesium alloy sheets were processed by friction stir processing(FSP)to investigate the effect of the grain refinement and grain size distribution on the corrosion behavior.Grain refinement ...In the present study,AZ31 magnesium alloy sheets were processed by friction stir processing(FSP)to investigate the effect of the grain refinement and grain size distribution on the corrosion behavior.Grain refinement from a starting size of 16.4±6.8µm to 3.2±1.2µm was attained after FSP.Remarkably,bimodal grain size distribution was observed in the nugget zone with a combination of coarse(11.62±8.4µm)and fine grains(3.2±1.2µm).Due to the grain refinement,a slight improvement in the hardness was found in the nugget zone of FSPed AZ31.The bimodal grain size distribution in the stir zone showed pronounced influence on the corrosion rate of FSPed AZ31 as observed from the immersion and electrochemical tests.From the X-ray diffraction analysis,more amount of Mg(OH)_(2) was observed on FSPed AZ31 compared with the unprocessed AZ31.Polarization measurements demonstrated the higher corrosion current density for FSPed AZ31(8.92×10^(−5)A/cm^(2))compared with the unprocessed condition(2.90×10^(−5)A/cm^(2))that can be attributed to the texture effect and large variations in the grain size which led to non-uniform galvanic intensities.展开更多
Revised Universal Soil Loss Equation(RUSLE) model coupled with transport limited sediment delivery(TLSD) function was used to predict the longtime average annual soil loss, and to identify the critical erosion-/deposi...Revised Universal Soil Loss Equation(RUSLE) model coupled with transport limited sediment delivery(TLSD) function was used to predict the longtime average annual soil loss, and to identify the critical erosion-/deposition-prone areas in a tropical mountain river basin, viz., Muthirapuzha River Basin(MRB; area=271.75 km^2), in the southern Western Ghats, India. Mean gross soil erosion in MRB is 14.36 t ha^(-1) yr^(-1), whereas mean net soil erosion(i.e., gross erosion-deposition) is only 3.60 t ha^(-1) yr^(-1)(i.e., roughly 25% of the gross erosion). Majority of the basin area(~86%) experiences only slight erosion(<5 t ha^(-1) yr^(-1)), and nearly 3% of the area functions as depositional environment for the eroded sediments(e.g., the terraces of stream reaches, the gentle plains as well as the foot slopes of the plateau scarps and the terrain with concordant summits). Although mean gross soil erosion rates in the natural vegetation belts are relatively higher, compared to agriculture, settlement/built-up areas and tea plantation, the sediment transport efficiency in agricultural areas and tea plantation is significantly high,reflecting the role of human activities on accelerated soil erosion. In MRB, on a mean basis, 0.42 t of soil organic carbon(SOC) content is being eroded per hectare annually, and SOC loss from the 4th order subbasins shows considerable differences, mainly due to the spatial variability in the gross soil erosion rates among the sub-basins. The quantitative results, on soil erosion and deposition, modelled using RUSLE and TLSD, are expected to be beneficial while formulating comprehensive land management strategies for reducing the extent of soil degradation in tropical mountain river basins.展开更多
Existence of tension–compression yield asymmetry is a serious limitation to the load bearing capablities of Magnesium alloys in a number of light weight structural applications.The present work is aimed at nullifying...Existence of tension–compression yield asymmetry is a serious limitation to the load bearing capablities of Magnesium alloys in a number of light weight structural applications.The present work is aimed at nullifying the tension to compression asymmetry problem and strain hardening anomalies in a Magnesium–Silver–Rare Earth alloy by engineering different levels of microstructural conditions via friction stir processing and post process annealing.The existence and extent of yield asymmetry ratio in the range of microstructural conditions was experimentally obtained through quasistatic tensile and compression tests.The yield asymmetry problem was profoundly present in specimens of coarse grained microstructures when compared to their fine grained and ultra fine grained counterparts.The impact of the microstructure and associated mechanisms of plasticity on the macroscopic strain hardening behavior was established by Kock–Mecking’s analysis.Crystal plasticity simulations using Viscoplastic Self Consistency approach revealed the consequential role of extension twinning mechanism for the existence of yield asymmetry and anomalies in strain hardening behavior.This was especially dominant with coarsening of grain size.Electron Microscopy and characterization were conducted thoroughly in partially deformed specimens to confirm the predictions of the above simulations.The role of crystallographic texture for inducing the polarity to Tension–Compression yield asymmetry was corroborated.A critical grain size in Magnesium–Silver–Rare earth alloy was hereby established which could nullify influences of extension twinning in yield asymmetry ratio.展开更多
Friction stir lap welds were produced in 3 mm thick Alclad sheets of Al alloy 2014-T4 using two different tools （with triangular and threaded taper cylindrical pins）. The effects of tool geometry on weld microstruct...Friction stir lap welds were produced in 3 mm thick Alclad sheets of Al alloy 2014-T4 using two different tools （with triangular and threaded taper cylindrical pins）. The effects of tool geometry on weld microstructure, lap-shear performance and failure mode were investigated. The pin profile was found to significantly influence the hook geometry, which in turn strongly influenced the joint strength and the failure mode. Welds produced in alloy 2014-T4 Alclad sheets by using triangular and threaded taper cylindrical tools exhibited an average lap-shear failure load of 16.5 and 19.5 kN, respectively, while the average failure load for standard riveted joints was only 3.4 kN. Welds produced in alloy 2014-T6 Alclad sheets and in alloy 2014-T4 bare sheets （i.e., no Alclad） were comparatively evaluated with those produced in alloy 2014-T4 Alclad sheets. While the welds made （with threaded taper cylindrical tool） in T6 and T4 conditions showed very similar lap-shear failure loads, the joint efficiency of the welds made in T6 condition （43%） was considerably lower （because of the higher base material strength） than those made in T4 condition （51%）. The Alclad layers were found to present no special problems in friction stir lap welding. Welds made with triangular tool in alloy 2014-T4 Alclad and bare sheets showed very similar lap-shear failure loads. The present work provides some useful insights into the use of friction stir welding for joining Al alloys in lap configuration.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
The effect of sintering temperature on the densification mechanisms, microstructural evolution and mechanical properties of spark plasma sintered （SPS） compacts of a gas atomized Al-4.5 wt.%Cu alloy was investigated...The effect of sintering temperature on the densification mechanisms, microstructural evolution and mechanical properties of spark plasma sintered （SPS） compacts of a gas atomized Al-4.5 wt.%Cu alloy was investigated. The powder particles whose size varied between 10 to 500μm was subjected to SPS at 400, 450 and 500℃ at a pressure of 30 MPa. The compact sintered at 500℃ exhibited fully dense microstructure which was characterized by a uniform distribution of the secondary phase, free of dendrites and micro-porosity. Microscopy and the SPS data reveal that the events such as particle rearrangement, localized deformation and bulk deformation appear to be the sequence of sintering mechanisms depending on the size range of powder particles used for consolidation. The compact sintered at 500℃ exhibited the highest hardness and compression strength since the microstructure was characterized by fine distribution of precipitates, large fraction of submicron grains and complete metallurgical bonding.展开更多
Realising the potential of Magnesium(Mg),several globally leading ventures have invested in the Mg industry,but their relatively poor corrosion resistance is a never ending saga till date.The corrosion and bio-corrosi...Realising the potential of Magnesium(Mg),several globally leading ventures have invested in the Mg industry,but their relatively poor corrosion resistance is a never ending saga till date.The corrosion and bio-corrosion behaviour of Mg has gained research attention and still remains a hot topic in the application of automobile,aerospace and biomedical industries.The intrinsic high electrochemical nature of Mg limits their utilization in diverse application.This scenario has prompted the development of Mg composites with an aim to achieve superior corrosion and bio-corrosion resistance.The present review enlightens the influence of grain size(GS),secondary phase,texture,type of matrix and reinforcement on the corrosion and bio-corrosion behaviour of Mg composites.Firstly,the corrosion and bio-corrosion behaviour of Mg composites manufactured by primary and secondary processing routes are elucidated.Secondly,the comprehensive corrosion and bio-corrosion mechanisms of these Mg composites are proposed.Thirdly,the individual role of GS,texture and corrosive medium on corrosion and bio-corrosion behaviour of Mg composites are clarified and revealed.The challenges encountered,unanswered issues in this field are explained in detail and accordingly the scope for future research is framed.The review is presented from basic concrete background to advanced corrosion mechanisms with an aim of creating interest among the readers like students,researchers and industry experts from various research backgrounds.Indeed,the corrosion and bio-corrosion behaviour of Mg composites are critically reviewed for the first time to:(i)contribute to the body of knowledge,(ii)foster research and development,(iii)make breakthrough,and(iv)create life changing innovations in the field of Mg composite corrosion.展开更多
Semiclathrate hydrates of tetra-n-butyl ammonium bromide （TBAB） offer potential solution for gas storage, transportation, separation of flue gases and CO2 sequestration. Models for phase equilibria for these systems...Semiclathrate hydrates of tetra-n-butyl ammonium bromide （TBAB） offer potential solution for gas storage, transportation, separation of flue gases and CO2 sequestration. Models for phase equilibria for these systems have not yet been developed in open literatures and thus require urgent attention. In this work, the first attempt has been made to model phase equilibria of semiclathrate hydrates of CH4, CO2 and N2 in aqueous solution of TBAB. A thermodynamic model for gas hydrate system as proposed by Chen and Guo has been extended for semiclathrate hydrates of gases in aqueous solution of TBAB. A correlation for the activity of water relating to the system temperature, concentration of TBAB in the system and the nature of vip gas molecule has been proposed. The model results have been validated against available experimental data on phase equilibria of semiclathrate hydrate systems of aqueous TBAB with different gases as vip molecule. The extended Chen and Guo＇s model is found to be suitable to explain the promotion effect of TBAB for the studied gaseous system such as, methane, carbon dioxide and nitrogen as a vip molecule. Additionally, a correlation for the increase in equilibrium formation temperature （hydrate promotion temperature, ATp） of semiclathrate hydrate system with respect to pure gas hydrate system has been developed and applied to semiclathrate hydrate of TBAB with several gases as vip molecules. The developed correlation is found to predict the promotion effect satisfactorily for the system studied.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
Effectiveness of pulsed power plasma for the degradation of two toxic volatile organic compounds(VOCs),toluene and methyl isobutyl ketone(MIBK),in aqueous solution was evaluated.The plasma degradation of MIBK has been...Effectiveness of pulsed power plasma for the degradation of two toxic volatile organic compounds(VOCs),toluene and methyl isobutyl ketone(MIBK),in aqueous solution was evaluated.The plasma degradation of MIBK has been studied for the first time.The influence of initial concentration of target compound,solution pH and scavengers on percentage degradation was evaluated.100%removal of 200 mg/L of toluene and MIBK was achieved both in liquid and gaseous phases after 12 and 16 min of plasma treatment,respectively.The first order rate constant of toluene and MIBK degradation(for 200 mg/L each)was 0.421 and 0.319 min~(-1)respectively when they were treated individually,and these values decreased slightly during degradation of their mixture.MIBK degradation was slower than toluene and it might be due to semi volatile and hydrophilic nature of MIBK.The effect of initial concentration of toluene and MIBK showed different degradation patterns.Highest degradation of both the compounds was obtained in neutral pH and in absence of scavengers.·OH radical was the major reactive species involved in their degradation.Their degradation in real environmental matrices showed that removal reduced significantly in secondary effluent due to scavenging of reactive species by various ions and organic matter.The total number of degradation intermediates identified in case of toluene and MIBK was 11 and 14 respectively and formate was the one recalcitrant byproduct generated.The degradation pathway of toluene and MIBK involving reactions of reactive oxygen and nitrogen species and reductive species is proposed.展开更多
The microstructure,mechanical properties and fracture behavior of an as-received QE22 alloy have been investigated under different thermal conditions,including solution treated(ST),under aged(UA),peak aged(PA)and over...The microstructure,mechanical properties and fracture behavior of an as-received QE22 alloy have been investigated under different thermal conditions,including solution treated(ST),under aged(UA),peak aged(PA)and over aged(OA)conditions.A significant increase in hardness of 27%,yield strength of 60%and ultimate tensile strength of 19%was observed in peak aged sample as compared to solution treated sample.The improvements of mechanical strength properties are mainly associated with the metastable λ and β′precipitates.Grain growth was not observed in the ST samples after subjecting to UA and PA treatments due to the presence of eutectic Mg_(12)Nd particles along the grain boundaries.In over aged sample,significant grain growth occurred because of dissolution of eutectic phase particles.Different natures of crack initiation and propagation were observed under different thermal conditions during tensile testing at room temperature.The mode of failure of solution treated sample is transgranular,cleavage and twin boundary fractures.A mixed mode of transgranular,intergranular,cleavage and twin boundary failure is observed in both peak aged and over aged samples.展开更多
文摘This article studies the existence and uniqueness of the mild solution of a family of control systems with a delay that are governed by the nonlinear fractional evolution differential equations in Banach spaces.Moreover,we establish the controllability of the considered system.To do so,first,we investigate the approximate controllability of the corresponding linear system.Subsequently,we prove the nonlinear system is approximately controllable if the corresponding linear system is approximately controllable.To reach the conclusions,the theory of resolvent operators,the Banach contraction mapping principle,and fixed point theorems are used.While concluding,some examples are given to demonstrate the efficacy of the proposed results.
文摘The rapid industrial growth and increasing population have led to significant pollution and deterioration of the natural atmospheric environment.Major atmospheric pollutants include NO_(2)and CO_(2).Hence,it is imperative to develop NO_(2)and CO_(2)sensors for ambient conditions,that can be used in indoor air quality monitoring,breath analysis,food spoilage detection,etc.In the present study,two thin film nanocomposite(nickel oxide-graphene and nickel oxide-silver nanowires)gas sensors are fabricated using direct ink writing.The nano-composites are investigated for their structural,optical,and electrical properties.Later the nano-composite is deposited on the interdigitated electrode(IDE)pattern to form NO_(2)and CO_(2)sensors.The deposited films are then exposed to NO_(2)and CO_(2)gases separately and their response and recovery times are determined using a custom-built gas sensing setup.Nickel oxide-graphene provides a good response time and recovery time of 10 and 9 s,respectively for NO_(2),due to the higher electron affinity of graphene towards NO_(2).Nickel oxide-silver nanowire nano-composite is suited for CO_(2)gas because silver is an excellent electrocatalyst for CO_(2)by giving response and recovery times of 11 s each.This is the first report showcasing NiO nano-composites for NO_(2)and CO_(2)sensing at room temperature.
基金the Expedition support to MoES, New Delhi and NCAOR, Goa (No. Mo ES/NCAOR/SOS/1/2007-PC-I dated January 4, 2011)+5 种基金the Cumulative Professional Development Grant (CPDG Ref No. GO/PD/2011-12/269/3523 dated, August 04, 2011) from BIT, MesraBTISNet Sub DIC (BT/BI/065/2004) for providing internet facilities and the Government of JharkhandDepartment of Agriculture for providing infrastructure development fund (5/B.K.V/Misc/12/2001)the financial support as research fellowship to Centre of Excellence (COE) (Ref No. NPIU/TEQIP II/FIN/31/158, dated April 16, 2013) at the Department of BioEngineering
文摘Fifty-seven bacteria were isolated from Southern Ocean （Indian sector） water samples which were collected from different latitude and longitude of the ocean. All the isolates were able to grow at 4℃, 20℃, 37℃ and tolerable NaCI concentration up to 13.5% （w/v）. 29 out of 57 isolates were identified using 16S rDNA amplification and the sequences were submitted to National Center for Biotechnology Information （NCBI）. All the isolates were classified by using Ribosomal Database Project （RDP） and found that isolates belongs to Proteobacteria and Bacteriodes. The average G＋C content was 56.4%. The isolates were screened for the presence of extracellular enzymes, viz. amylase, catalase, urease, esterase, lipase and protease. The disc diffusion method is used to screen antibiotic production by the isolates against four pathogenic bacteria, viz. Salmonella typhimurium （NCIM 2501）, Staphylococcus aureus （NCIM 2122）, Bacillus subtilis （NCIM 2193）, and Pseudomonas aeruginosa （NCIM 2036）. Nine out of 29 were found to be antibiotic producer.
文摘A Shape Memory Polymer Composite(SMPC)is developed by reinforcing an epoxy-based polymer with randomly oriented short glass fibers.Diverging from previous research,which primarily focused on the hot programming of short glass fiber-based SMPCs,this work explores the potential for programming below the glass transition temperature(Tg)for epoxy-based SMPCs.To mitigate the inherent brittleness of the SMPC during deformation,a linear polymer is incorporated,and a temperature between room temperature and Tg is chosen as the deformation temperature to study the shape memory properties.The findings demonstrate an enhancement in shape fixity and recovery stress,alongside a reduction in shape recovery,with the incorporation of short glass fibers.In addition to tensile properties,thermal properties such as thermal conductivity,specific heat capacity,and glass transition temperature are investigated for their dependence on fiber content.Microscopic properties,such as fiber-matrix adhesion and the dispersion of glass fibers,are examined through Scanning Electron Microscope imaging.The fiber length distribution and mean fiber lengths are also measured for different fiber fractions.
基金supported and funded by the British Petroleum-International Centre for Advanced Materials(BP-ICAM)on project ICAM-39(Water Injection in Soft Sand Reservoirs)the University of Cambridge,UK.Their support is gratefully acknowledged.
文摘Understanding and controlling fracture propagation is one of the most challenging engineering problems,especially in the oil and gas sector,groundwater hydrology,and geothermal energy applications.Predicting fracture orientation while possessing a nonlinear material response becomes more complex when the medium is subjected to anisotropic boundary stresses.Furthermore,the fracturing behaviour of geological porous media that exhibit high leak-off potential is not clearly understood.In this context,a novel testing technique is used to simulate in situ conditions in the laboratory and to study the instability characteristics of such geomaterials.The bespoke apparatus designed and developed in this research programme is capable of applying true anisotropic boundary stresses,injecting fluid at a predefined flow rate and viscosity while imaging instability/fracture propagation in a porous medium such as sand and bio-cemented sands.Pressure profiles and fracture propagation are simultaneously recorded during fluid injection into specimens subjected to different boundary stresses.Analysis of the images obtained during the fluid injection process provides information on the evolution of infiltration and fracture area during the injection event.The quantification of pressure and the corresponding fracture signature is,therefore,useful for a comprehensive understanding of the mechanics of fluid-induced fracture propagation.
文摘Heat treatments play a crucial role in enhancing the mechanical properties of AZ91 Mg alloy by dissolving coarse phases during solution treatment and promoting precipitation during aging.However,non-uniform microstructures and coarse secondary phases in conventional casting methods hinder the effectiveness of these treatments,leading to reduced ductility,inconsistent properties,and prolonged durations.To overcome these challenges,this study introduces the Strain Integrated Gas-Infusion(SIGI)casting process that integrates strain and gas infusion in the semi-solid state.The impact of the SIGI process on the solution treatment and aging kinetics of AZ91 Mg alloy is explored.The SIGI process refinesα-Mg andβ-Mg_(17)Al_(12)phases,significantly enhancing mechanical properties.Experimental and quantitative analyses reveal that the SIGI process accelerates solute atom dissolution,reducing solution treatment times by half,and promotes faster nucleation and growth of precipitates during aging,shortening aging times by one-third.These improvements result in substantial gains in ultimate tensile strength(~40-50%)and ductility(~20-30%)after age hardening compared to conventional casting.The mechanisms driving these changes,including enhanced nucleation rates,reduced diffusion distances,and microstructural refinement,are discussed.These findings demonstrate the potential of the SIGI casting process to advance magnesium alloy performance for engineering applications.
基金Foundation of China(Grant No.52261160382)for financial support.
文摘Biochar is a carbon sink material with the potential to improve water retention in various soils.However,for the long‐term maintenance of green infrastructure,there is an additional need to regulate the water contents in the covers to maintain vegetation growth in semiarid conditions.In this study,biochar‐amended soil was combined with subsurface drip irrigation,and the water preservation characteristics of this treatment were investigated through a series of one‐dimensional soil column tests.To ascertain the best treatment method specific to semiarid climatic conditions,the test soil was amended with 0%,1%,3%,and 5%biochar.Automatic irrigation devices equipped with soil moisture sensors were used to control the subsurface water content with the aim of enhancing vegetation growth.Each soil column test lasted 150 h,during which the volumetric water contents and soil suction data were recorded.The experimental results reveal that the soil specimen amended with 3%biochar is the most water‐saving regardless of the time cost.Soil with a higher biochar content(e.g.,5%)consumes a more significant amount of water due to the enhancement of the water‐holding capacity.Based on the experimental results,it can be concluded that the appropriate ratio can be determined within 1%–3%,which can reduce not only the amount of irrigated/used water but also the time cost.Such technology can be explored for water content regulation in green infrastructure and the development of barriers for protecting the environment around deep underground waste containment.
文摘Quantification of seismic activity is one of the most challenging problems faced by earthquake engineers in probabilistic seismic hazard analysis. Currently, this problem has been attempted using empirical approaches which are based on the regional earthquake recurrence relations from the available earth- quake catalogue. However, at a specified site of engineering interest, these empirical models are asso- ciated with large number of uncertainties due to lack of sufficient data. Due to these uncertainties, engineers need to develop mechanistic models to quantify seismic activity. A wide range of techniques for modeling continental plates provides useful insights on the mechanics of plates and their seismic activity. Among the different continental plates, the Indian plate experiences diffused seismicity. In India, although Himalaya is regarded as a plate boundary and active region, the seismicity database indicates that there are other regions in the Indian shield reporting sporadic seismic activity. It is expected that mechanistic models of Indian plate, based on finite element method, simulate stress fields that quantify the seismic potential of active regions in India, This article explores the development of a finite element model for Indian plate by observing the simulated stress field for various boundary conditions, geological and theological conditions. The study observes that the magnitude and direction of stresses in the plate is sensitive to these conditions, The numerical analysis of the models shows that the simulated stress field represents the active seismic zones in India.
文摘Volatile organic compounds(VOC's) in air have become major concern in recent years. Biodegradation of a mixture of ethanol and methanol vapor was evaluated in a laboratory biofilter with a bed of compost and polystyrene particles using an acclimated mixed culture. The continuous performance of the biofilter was studied with different proportion of ethanol and methanol at different initial concentration and flow rates. The result showed significant removal for both ethanol and methanol, which were composition dependent. The presence of either compound in the mixture inhibited the biodegradation of the other.
文摘In the present study,AZ31 magnesium alloy sheets were processed by friction stir processing(FSP)to investigate the effect of the grain refinement and grain size distribution on the corrosion behavior.Grain refinement from a starting size of 16.4±6.8µm to 3.2±1.2µm was attained after FSP.Remarkably,bimodal grain size distribution was observed in the nugget zone with a combination of coarse(11.62±8.4µm)and fine grains(3.2±1.2µm).Due to the grain refinement,a slight improvement in the hardness was found in the nugget zone of FSPed AZ31.The bimodal grain size distribution in the stir zone showed pronounced influence on the corrosion rate of FSPed AZ31 as observed from the immersion and electrochemical tests.From the X-ray diffraction analysis,more amount of Mg(OH)_(2) was observed on FSPed AZ31 compared with the unprocessed AZ31.Polarization measurements demonstrated the higher corrosion current density for FSPed AZ31(8.92×10^(−5)A/cm^(2))compared with the unprocessed condition(2.90×10^(−5)A/cm^(2))that can be attributed to the texture effect and large variations in the grain size which led to non-uniform galvanic intensities.
基金Financial support from Kerala State Council for Science, Technology, and Environment (004/FSHP/05KSCSTE)
文摘Revised Universal Soil Loss Equation(RUSLE) model coupled with transport limited sediment delivery(TLSD) function was used to predict the longtime average annual soil loss, and to identify the critical erosion-/deposition-prone areas in a tropical mountain river basin, viz., Muthirapuzha River Basin(MRB; area=271.75 km^2), in the southern Western Ghats, India. Mean gross soil erosion in MRB is 14.36 t ha^(-1) yr^(-1), whereas mean net soil erosion(i.e., gross erosion-deposition) is only 3.60 t ha^(-1) yr^(-1)(i.e., roughly 25% of the gross erosion). Majority of the basin area(~86%) experiences only slight erosion(<5 t ha^(-1) yr^(-1)), and nearly 3% of the area functions as depositional environment for the eroded sediments(e.g., the terraces of stream reaches, the gentle plains as well as the foot slopes of the plateau scarps and the terrain with concordant summits). Although mean gross soil erosion rates in the natural vegetation belts are relatively higher, compared to agriculture, settlement/built-up areas and tea plantation, the sediment transport efficiency in agricultural areas and tea plantation is significantly high,reflecting the role of human activities on accelerated soil erosion. In MRB, on a mean basis, 0.42 t of soil organic carbon(SOC) content is being eroded per hectare annually, and SOC loss from the 4th order subbasins shows considerable differences, mainly due to the spatial variability in the gross soil erosion rates among the sub-basins. The quantitative results, on soil erosion and deposition, modelled using RUSLE and TLSD, are expected to be beneficial while formulating comprehensive land management strategies for reducing the extent of soil degradation in tropical mountain river basins.
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 supportFIST grant,Department of Science and Technology,India[grant number SR/FST/ET11-059/2012(G)]for funding electron microscope facility。
文摘Existence of tension–compression yield asymmetry is a serious limitation to the load bearing capablities of Magnesium alloys in a number of light weight structural applications.The present work is aimed at nullifying the tension to compression asymmetry problem and strain hardening anomalies in a Magnesium–Silver–Rare Earth alloy by engineering different levels of microstructural conditions via friction stir processing and post process annealing.The existence and extent of yield asymmetry ratio in the range of microstructural conditions was experimentally obtained through quasistatic tensile and compression tests.The yield asymmetry problem was profoundly present in specimens of coarse grained microstructures when compared to their fine grained and ultra fine grained counterparts.The impact of the microstructure and associated mechanisms of plasticity on the macroscopic strain hardening behavior was established by Kock–Mecking’s analysis.Crystal plasticity simulations using Viscoplastic Self Consistency approach revealed the consequential role of extension twinning mechanism for the existence of yield asymmetry and anomalies in strain hardening behavior.This was especially dominant with coarsening of grain size.Electron Microscopy and characterization were conducted thoroughly in partially deformed specimens to confirm the predictions of the above simulations.The role of crystallographic texture for inducing the polarity to Tension–Compression yield asymmetry was corroborated.A critical grain size in Magnesium–Silver–Rare earth alloy was hereby established which could nullify influences of extension twinning in yield asymmetry ratio.
基金the Indian Space Research Organization (ISRO) for providing financial support forcarrying out this work
文摘Friction stir lap welds were produced in 3 mm thick Alclad sheets of Al alloy 2014-T4 using two different tools （with triangular and threaded taper cylindrical pins）. The effects of tool geometry on weld microstructure, lap-shear performance and failure mode were investigated. The pin profile was found to significantly influence the hook geometry, which in turn strongly influenced the joint strength and the failure mode. Welds produced in alloy 2014-T4 Alclad sheets by using triangular and threaded taper cylindrical tools exhibited an average lap-shear failure load of 16.5 and 19.5 kN, respectively, while the average failure load for standard riveted joints was only 3.4 kN. Welds produced in alloy 2014-T6 Alclad sheets and in alloy 2014-T4 bare sheets （i.e., no Alclad） were comparatively evaluated with those produced in alloy 2014-T4 Alclad sheets. While the welds made （with threaded taper cylindrical tool） in T6 and T4 conditions showed very similar lap-shear failure loads, the joint efficiency of the welds made in T6 condition （43%） was considerably lower （because of the higher base material strength） than those made in T4 condition （51%）. The Alclad layers were found to present no special problems in friction stir lap welding. Welds made with triangular tool in alloy 2014-T4 Alclad and bare sheets showed very similar lap-shear failure loads. The present work provides some useful insights into the use of friction stir welding for joining Al alloys in lap configuration.
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.
文摘The effect of sintering temperature on the densification mechanisms, microstructural evolution and mechanical properties of spark plasma sintered （SPS） compacts of a gas atomized Al-4.5 wt.%Cu alloy was investigated. The powder particles whose size varied between 10 to 500μm was subjected to SPS at 400, 450 and 500℃ at a pressure of 30 MPa. The compact sintered at 500℃ exhibited fully dense microstructure which was characterized by a uniform distribution of the secondary phase, free of dendrites and micro-porosity. Microscopy and the SPS data reveal that the events such as particle rearrangement, localized deformation and bulk deformation appear to be the sequence of sintering mechanisms depending on the size range of powder particles used for consolidation. The compact sintered at 500℃ exhibited the highest hardness and compression strength since the microstructure was characterized by fine distribution of precipitates, large fraction of submicron grains and complete metallurgical bonding.
文摘Realising the potential of Magnesium(Mg),several globally leading ventures have invested in the Mg industry,but their relatively poor corrosion resistance is a never ending saga till date.The corrosion and bio-corrosion behaviour of Mg has gained research attention and still remains a hot topic in the application of automobile,aerospace and biomedical industries.The intrinsic high electrochemical nature of Mg limits their utilization in diverse application.This scenario has prompted the development of Mg composites with an aim to achieve superior corrosion and bio-corrosion resistance.The present review enlightens the influence of grain size(GS),secondary phase,texture,type of matrix and reinforcement on the corrosion and bio-corrosion behaviour of Mg composites.Firstly,the corrosion and bio-corrosion behaviour of Mg composites manufactured by primary and secondary processing routes are elucidated.Secondly,the comprehensive corrosion and bio-corrosion mechanisms of these Mg composites are proposed.Thirdly,the individual role of GS,texture and corrosive medium on corrosion and bio-corrosion behaviour of Mg composites are clarified and revealed.The challenges encountered,unanswered issues in this field are explained in detail and accordingly the scope for future research is framed.The review is presented from basic concrete background to advanced corrosion mechanisms with an aim of creating interest among the readers like students,researchers and industry experts from various research backgrounds.Indeed,the corrosion and bio-corrosion behaviour of Mg composites are critically reviewed for the first time to:(i)contribute to the body of knowledge,(ii)foster research and development,(iii)make breakthrough,and(iv)create life changing innovations in the field of Mg composite corrosion.
基金supported by the the Industrial Consultancy and Sponsored Research (ICSR),Indian Institute of Technology Madras,Chennai (Project Number OEC/10 11/530/NFSC/JITE)the National Institute of Ocean Technology (NIOT),Chennai,India (Project Number OEC/10-11/105/NIOT/JITE)
文摘Semiclathrate hydrates of tetra-n-butyl ammonium bromide （TBAB） offer potential solution for gas storage, transportation, separation of flue gases and CO2 sequestration. Models for phase equilibria for these systems have not yet been developed in open literatures and thus require urgent attention. In this work, the first attempt has been made to model phase equilibria of semiclathrate hydrates of CH4, CO2 and N2 in aqueous solution of TBAB. A thermodynamic model for gas hydrate system as proposed by Chen and Guo has been extended for semiclathrate hydrates of gases in aqueous solution of TBAB. A correlation for the activity of water relating to the system temperature, concentration of TBAB in the system and the nature of vip gas molecule has been proposed. The model results have been validated against available experimental data on phase equilibria of semiclathrate hydrate systems of aqueous TBAB with different gases as vip molecule. The extended Chen and Guo＇s model is found to be suitable to explain the promotion effect of TBAB for the studied gaseous system such as, methane, carbon dioxide and nitrogen as a vip molecule. Additionally, a correlation for the increase in equilibrium formation temperature （hydrate promotion temperature, ATp） of semiclathrate hydrate system with respect to pure gas hydrate system has been developed and applied to semiclathrate hydrate of TBAB with several gases as vip molecules. The developed correlation is found to predict the promotion effect satisfactorily for the system studied.
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the financial support received from Department of Science and Technology(DST),Government of India(Nos.DST/TM/WTI/WIC/2K17/82(G)and DST/CCP/Co E/141/2018(G))for this study。
文摘Effectiveness of pulsed power plasma for the degradation of two toxic volatile organic compounds(VOCs),toluene and methyl isobutyl ketone(MIBK),in aqueous solution was evaluated.The plasma degradation of MIBK has been studied for the first time.The influence of initial concentration of target compound,solution pH and scavengers on percentage degradation was evaluated.100%removal of 200 mg/L of toluene and MIBK was achieved both in liquid and gaseous phases after 12 and 16 min of plasma treatment,respectively.The first order rate constant of toluene and MIBK degradation(for 200 mg/L each)was 0.421 and 0.319 min~(-1)respectively when they were treated individually,and these values decreased slightly during degradation of their mixture.MIBK degradation was slower than toluene and it might be due to semi volatile and hydrophilic nature of MIBK.The effect of initial concentration of toluene and MIBK showed different degradation patterns.Highest degradation of both the compounds was obtained in neutral pH and in absence of scavengers.·OH radical was the major reactive species involved in their degradation.Their degradation in real environmental matrices showed that removal reduced significantly in secondary effluent due to scavenging of reactive species by various ions and organic matter.The total number of degradation intermediates identified in case of toluene and MIBK was 11 and 14 respectively and formate was the one recalcitrant byproduct generated.The degradation pathway of toluene and MIBK involving reactions of reactive oxygen and nitrogen species and reductive species is proposed.
文摘The microstructure,mechanical properties and fracture behavior of an as-received QE22 alloy have been investigated under different thermal conditions,including solution treated(ST),under aged(UA),peak aged(PA)and over aged(OA)conditions.A significant increase in hardness of 27%,yield strength of 60%and ultimate tensile strength of 19%was observed in peak aged sample as compared to solution treated sample.The improvements of mechanical strength properties are mainly associated with the metastable λ and β′precipitates.Grain growth was not observed in the ST samples after subjecting to UA and PA treatments due to the presence of eutectic Mg_(12)Nd particles along the grain boundaries.In over aged sample,significant grain growth occurred because of dissolution of eutectic phase particles.Different natures of crack initiation and propagation were observed under different thermal conditions during tensile testing at room temperature.The mode of failure of solution treated sample is transgranular,cleavage and twin boundary fractures.A mixed mode of transgranular,intergranular,cleavage and twin boundary failure is observed in both peak aged and over aged samples.
