Though the formation of polysulfide is desirable,as it contributes to the capacity build-up,it must not leak into the electrolyte.The loss of polysulfide causes capacity fade,a change in the local chemistry of the ele...Though the formation of polysulfide is desirable,as it contributes to the capacity build-up,it must not leak into the electrolyte.The loss of polysulfide causes capacity fade,a change in the local chemistry of the electrolyte,and anode poisoning.Constant efforts are in progress to find suitable polysulfide-absorbing materials;however,the magical polysulfide absorber is yet to be discovered or developed.Experimental methods alone often fall short in accelerating the investigations may be due to the complex Nature of the testing.This review focuses on the importance of computational methods,particularly density functional theory(DFT),in screening suitable polysulfide absorbers.It highlights the critical role of anchoring materials in improving Na-S battery performance,including pristine and doped graphene,metal–organic frameworks,carbon Nanofibers,vanadium disulfide,MXenes,and metal sulfides.By examining adsorption energies,charge transfer mechanisms,and catalytic properties,this review provides insights into the design of advanced materials that can effectively immobilize polysulfides and enhance battery stability.The review aims to guide future research efforts toward the development of high-performance RT Na-S batteries through a comprehensive understanding of the polysulfide-absorbing materials.展开更多
In heterogeneous traffic conditions, roundabout capacity is described by vehicle and driver characteristics which are different from traffic conditions in homogeneous conditions. In the present study, the capacity of ...In heterogeneous traffic conditions, roundabout capacity is described by vehicle and driver characteristics which are different from traffic conditions in homogeneous conditions. In the present study, the capacity of the roundabout is determined using various capacity formulas such as gap acceptance models given by Highway Capacity Manual 2010 （US）, German model （2001）; empirical regression models given by TRRL （UK） and weaving models given by IRC： 65-1976 （India）. In addition, microscopic simulation model like VISSIM （PTV Ger- many） is also used to derive capacity values. Unlike the other capacity estimation models, VISSIM is helpful in estimating capacity values using geometric and driver characteristics and it can also simulate heterogeneous traffic condition accurately. Capacity is estimated after calibrating the simulation model （VISSIM） developed for the roundabout. This is achieved by incorporating different vehicle classes to represent the heterogeneous traffic environment, driver gap acceptance, and lane changeparameters. All the required inputs were extracted from the video using semi-automatic data collection methods. Data are used for the estimation of capacity values from dif- ferent methods mentioned above and for the calibration and validation of simulation model. The capacity values esti- mated form various formulas except German model are distinctly different from the field values and they are either overestimating or underestimating. Analysis of these observations reveals that the capacity values from VISSIM and German models are nearly matching with the field capacity.展开更多
A general neural network based methodology that has the potential to replace the computationally-intensive site-specific seismic analysis of structures is proposed in this paper. The basic framework of the methodology...A general neural network based methodology that has the potential to replace the computationally-intensive site-specific seismic analysis of structures is proposed in this paper. The basic framework of the methodology consists of a feed forward back propagation neural network algorithm with one hidden layer to represent the seismic potential of a region and soil amplification effects. The methodology is implemented and verified with parameters corresponding to Delhi city in India. For this purpose, strong ground motions are generated at bedrock level for a chosen site in Delhi due to earthquakes considered to originate from the central seismic gap of the Himalayan belt using necessary geological as well as geotechnical data. Surface level ground motions and corresponding site-specific response spectra are obtained by using a one-dimensional equivalent linear wave propagation model. Spectral acceleration values are considered as a target parameter to verify the performance of the methodology. Numerical studies carried out to validate the proposed methodology show that the errors in predicted spectral acceleration values are within acceptable limits for design purposes. The methodology is general in the sense that it can be applied to other seismically vulnerable regions and also can be updated by including more parameters depending on the state-of-the-art in the subject.展开更多
With the increasing use of metal foams in various engineering applications, investigation of their dynamic behaviour under varying strain rate is necessary. Closed cell aluminium fly ash foam developed through liquid ...With the increasing use of metal foams in various engineering applications, investigation of their dynamic behaviour under varying strain rate is necessary. Closed cell aluminium fly ash foam developed through liquid metallurgy route was investigated for its stress--strain behaviour at different strain rates ranging from 700 s^-1 to 1950 s^-1. The numerical model of split Hopkinson pressure bar （SHPB） was simulated using commercially available finite element code Abaqus/Explicit. Validation of numerical simulation was carried out using available experimental and numerical results. Full scale stress--strain curves wez＇e developed for various strain rates to study the effect of strain rate on compressive strength and energy absorption. The results showed that the closed cell aluminium fly ash foam is sensitive to strain rate.展开更多
Transmission tower-line systems are designed using static loads specified in various codes. This paper compares the dynamic response of a test transmission line with the response due to static loads given by Eurocode....Transmission tower-line systems are designed using static loads specified in various codes. This paper compares the dynamic response of a test transmission line with the response due to static loads given by Eurocode. Finite element design software SAP2000 was used to model the towers and lines. Non-linear dynamic analysis including the large displacement effects was carried out. Macroscopic aspects of wind coherence along element length and integration time step were investigated. An approach is presented to compare the probabilistic dynamic response due to 7 different stochastically simulated wind fields with the response according to EN-50341. The developed model will be used to study the response recorded on a test line due to the actual wind speed time history recorded. It was found that static load from EN overestimated the strength of conductor cables. The response of coupled system considering towers and cables was found to be different from response of only cables with fixed supports.展开更多
Shock tube experiments were carried out to investigate dynamic behavior of Ultra-high hardness(UHH)steel and Aluminium(Al) sheets of 0.8 mm thickness at 0.55, 0.9 and 1.18 MPa peak-over pressure.Experimental results s...Shock tube experiments were carried out to investigate dynamic behavior of Ultra-high hardness(UHH)steel and Aluminium(Al) sheets of 0.8 mm thickness at 0.55, 0.9 and 1.18 MPa peak-over pressure.Experimental results showed that center point deflection increases with an increase in peak-over pressure for Al sheets. However, UHH steel sheets showed negligible deformation when loaded at low peak-over pressures and showed sudden brittle failure at high peak-over pressures. Similar results were obtained by quasi-static testing, UHH steel failed abruptly while Al showed ductile behavior. Results from literature indicate that to protect structures against shock loading it is necessary that they dissipate energy via plastic deformation. The Al sheets were shown to deform plastically both in quasi-static and shock loading. Thus, hardness along with ductility is required to dissipate supersonic shock waves.展开更多
Transparent luminescent solar concentrator(LSC)is extensively regarded as the most promising sunlight tapping device for its application in buildings integrated with photovoltaics(BIPV)or as solar window glass.Convent...Transparent luminescent solar concentrator(LSC)is extensively regarded as the most promising sunlight tapping device for its application in buildings integrated with photovoltaics(BIPV)or as solar window glass.Conventional LSCs doped with organic dyes suffered from high reabsorption losses with no transparency;whereas,recently reported heavy metal-doped quantum dots avoided such losses but possessed the risk of high toxicity and low ambient stability.Thus,luminophores with massive spectral shifts and co rdial relationships with the enviro nment are very much desirable.In this paper,we report the fabrication of PMMA based transparent LSC embedded with nanocrystals of environmental friendiness and multispectral harvesting gadolinium oxysulphide(Gd_(2)O_(2) S:Er,Yb)fluorophore.The Gd_(2)O_(2) S:Er,Yb nanofluorophore absorbs various excitation wavelengths ranging from UV to NIR and emits in the visible region offering huge Stoke’s and anti-Stoke’s shift concurrently.The non-existent reabsorption losses and overlapping maxima of Gd_(2)O_(2) S:Er,Yb nanofluorophore generated photon flux with solar cells’responsivity enhance the efficiency characteristics of the LSC waveguide.Performance analysis of LSC as a function of varying nanofluorophore dispersion ratio and changing edge width optimizes the fabrication process and exhibits high power conversion efficiency of-6,93%and optical efficiency of-8.57%.The LSC slab demonstrates high photostability under irradiation for prolonged hours without any dip in the emission characteristics.The Gd_(2)O_(2) S:Er,Yb nanofluorophore diffused LSC waveguide offering spectral tunability,cost-reduction,efficiency enhancement,and high concentration factor whilst being sustainable for long term use makes it a fascinating transparent solar window.展开更多
In this paper, the performance of various Pulse Position Modulation (PPM) schemes has been analysed for PIN and APD receivers in the presence of atmospheric turbulence. It is observed that the performance of the APD r...In this paper, the performance of various Pulse Position Modulation (PPM) schemes has been analysed for PIN and APD receivers in the presence of atmospheric turbulence. It is observed that the performance of the APD receiver is always better than that of the PIN receiver as expected. Among the various modulation schemes, the performance of Differential Amplitude PPM (DAPPM) scheme with more number of amplitude levels is better than that of the other schemes for the same single level peak amplitude. Further, the optimum gain of APD receiver does not change substantially for different modulation schemes and turbulent conditions.展开更多
Seismic response of ground supported baseisolated liquid storage tanks are evaluated under bi-directional earthquakes. The base-isolated liquid storage tanks are modeled using mechanical analogs with two and three lum...Seismic response of ground supported baseisolated liquid storage tanks are evaluated under bi-directional earthquakes. The base-isolated liquid storage tanks are modeled using mechanical analogs with two and three lumped masses (Model 1 and Model 2). Two types of isolation systems, such as sliding system and elastomeric system, are considered for the present study. The isolation systems are modeled using Wen’s equation for hysteretic isolation systems. Response of base-isolated liquid storage tanks, evaluated through two different modeling approaches, is compared. Both the models predict similar sloshing displacement. The effect of interaction between the mutually perpendicular seismic responses of the isolator is investigated for both the models. It is observed that interaction affects the peak seismic response of the base-isolated liquid storage tanks significantly, under the bi-directional earthquake components.展开更多
The Al-Si alloy with near eutectic composition has been conventionally used as a piston material for automobile applications. It is required to possess high abrasive wear resistance for enhanced life of the engine. Th...The Al-Si alloy with near eutectic composition has been conventionally used as a piston material for automobile applications. It is required to possess high abrasive wear resistance for enhanced life of the engine. The alloy is known to have fairly good wear resistance due to increased percentage of silicon present in fine form. In the present investigation, Al-SiC particulate composites have been studied for their wear resistance against emery paper (400 grit SiC particles) counterface and a comparison has been made with existing piston alloy i.e. Al-Si alloy. The Al-SiC composites have been prepared using Liquid Metallurgy technique employing 2124 Al alloy as the base material with 10 and 20 % SiC particulates by weight. The abrasive wear study has been conducted on a Pin on Disc machine. The wear rate in terms of weight loss per unit sliding distance as well as the volumetric wear rate have been obtained for the Al-SiC composites. The characteristics of worn surface were investigated using SEM. The composites are found to possess very high wear resistance as compared to Al-Si piston alloy. The results have been discussed and important conclusions are outlined.展开更多
In the present work, one-dimensional nanostructures of silicon oxide (SiOx) have been synthesized by thermal annealing method with and without chromium thin film on silicon substrate. The synthesis was carried out at ...In the present work, one-dimensional nanostructures of silicon oxide (SiOx) have been synthesized by thermal annealing method with and without chromium thin film on silicon substrate. The synthesis was carried out at different process temperatures ranging from 1000°C to 1100°C by using gold/chromium (Au/Cr) catalysts stack layer on the Si substrate in nitrogen (N2) ambience. The as-synthesized SiOx nanostructures have tetragonal rutile structure and show polycrystalline nature. The SEM images reveal wire-like nanostructures on the substrate with and without chromium thin film. Under the catalytic reaction of the gold/chromium metal, the density of SiOx nanowires is enhanced, since the Cr layer serves as a diffusion barrier for the diffusion of the gold downwards into the Si substrate. The vapor-liquid solid (VLS) growth mechanism is found to be dominant in the growth of SiOx nanowires. Furthermore, X-Ray diffraction microscopy (XRD) and Photoluminescence spectroscopy (PL) analysis conclude the defect free growth of the SiOx nanowires on gold/chrome/silicon substrate.展开更多
This paper presents the formulation of the possibilistic Renyi entropy function from the Renyi entropy function using the framework of Hanman-Anirban entropy function. The new entropy function is used to derive the in...This paper presents the formulation of the possibilistic Renyi entropy function from the Renyi entropy function using the framework of Hanman-Anirban entropy function. The new entropy function is used to derive the information set features from keystroke dynamics for the authentication of users. A new composite fuzzy classifier is also proposed based on Mamta-Hanman entropy function and applied on the Information Set based features. A comparison of the results of the proposed approach with those of Support Vector Machine and Random Forest classifier shows that the new classifier outperforms the other two.展开更多
Nearly 95% of monomers or chemical intermediates used today are based on fossilized carbon such as coal and petroleum. This has resulted in a high rate of depletion of fossilized reserves, continuous escalation in pet...Nearly 95% of monomers or chemical intermediates used today are based on fossilized carbon such as coal and petroleum. This has resulted in a high rate of depletion of fossilized reserves, continuous escalation in petroleum prices, environmental impact with the increase in emission of greenhouse gases, and accumulation of non-biodegradable waste on earth. Current global main challenges are moving towards green sources - need for vast new and sustainable material resources;supplement, reuse and replace petroleum based polymeric materials;biodegradability of materials to prevent build up of waste;toxicity associated with the preparation, usage and environmental safety. Recent investigations are therefore, focused on procuring materials from the plant resources, agricultural waste and their utility in synthesis of polymeric materials. Amongst the polymers derived from natural resources poly(lactic acid) is a leading candidate. Commercial quantities of natural oil-based polyols such as castor, soya bean oil have been available over the past several years and currently used for synthesis of? polyesters, polyurethanes etc, but today many other? natural materials are also being investigated. It should be possible to produce sustainable polymers commercially and economically.展开更多
This paper proposes a novel equalizer, termed here as Evolutionary MPNN, where a complex modified probabilistic Neural Networks (MPNN) acts as a filter for the detected signal pattern. The neurons were embedded with o...This paper proposes a novel equalizer, termed here as Evolutionary MPNN, where a complex modified probabilistic Neural Networks (MPNN) acts as a filter for the detected signal pattern. The neurons were embedded with optimization algorithms. We have considered two optimization algorithms, Bacteria Foraging Optimization (BFO) and Ant Colony Optimization (ACO). The proposed structure have the ability to process complex signals also can perform for slowly varying channels. Also, Simulation results prove the superior performance of the proposed equalizer over the existing MPNN equalizers.展开更多
The prediction of water quality in terms of variables like dissolved oxygen (DO), biochemical oxygen demand (BOD), pH value, total dissolved solids (TDS) and salinity etc. is useful for evaluating the use of water for...The prediction of water quality in terms of variables like dissolved oxygen (DO), biochemical oxygen demand (BOD), pH value, total dissolved solids (TDS) and salinity etc. is useful for evaluating the use of water for various related purposes. The widely used Streeter and Phelps models for computing biochemical oxygen demand and its impact on dissolved oxygen do not account for the settleable component of BOD and related implications. The model also does not account for the impact of storage zone on the stream’s DO. In the present work an attempt is made to develop a model which simultaneously accounts for the settleable component of BOD and the effect of storage zones onriver’s DO. An application of the model to real field data suggests that the cumulative impact of settleable BOD and presence of storage zone in the river is to shift the critical deficit closer to the point source and magnify its amount.展开更多
Commercial-level sodium metal batteries require electrolytes with high ionic mobility and excellent thermo-mechanical and electrochemical stability.Conventional flammable liquid electrolytes,prone to dendrite growth a...Commercial-level sodium metal batteries require electrolytes with high ionic mobility and excellent thermo-mechanical and electrochemical stability.Conventional flammable liquid electrolytes,prone to dendrite growth and unstable interfacial reactions,rarely perform beyond coin-cell demonstrations.To address these shortcomings,a multifunctional composite quasi-solid polymer electrolyte(QSPE)that incorporates boron nitride(BN)as an engineered filler in a highly conductive polymer blend system has been developed.The optimized formation(15BN QSPE)delivers a room-temperature ionic conductivity of 2.15 m S cm^(-1)and a sodium-ion transference number of 0.80.Molecular dynamics simulations elucidate the coordination environment and show improved transport in the presence of BN.BN is chemically active and bifunctional:boron acts as an electron acceptor,interacting with solvents and macromolecules,while nitrogen coordinates with sodium ions,tailoring the solvation environment and transport pathways to promote efficient ion migration.The 15BN QSPE is self-extinguishing,resists oxidative thermal degradation,and enables stable cycling in symmetric sodium cells for>1400 h at0.5 m A cm^(-2).A Prussian blue full cell achieves>1500 stable cycles at 1C with -99% Coulombic efficiency in coin-cell configuration.A two-layer pouch cell with dual 15BN QSPE layers delivers 600 stable cycles at 0.125C and withstands rigorous mechanical abuse.These results position 15BN QSPE as a scalable,highperformance electrolyte offering enhanced safety and efficiency for next-generation sodium metal batteries.展开更多
The experimental tests were carried out on a single cylinder hydrogen fueled spark ignition(SI)generator set with different spark timings(4-20℃A bTDC),exhaust gas recirculation(EGR)up to 28% by volume and water injec...The experimental tests were carried out on a single cylinder hydrogen fueled spark ignition(SI)generator set with different spark timings(4-20℃A bTDC),exhaust gas recirculation(EGR)up to 28% by volume and water injection up to 1.95 kg/h(maximum water to fuel mass ratio of 8:1).The engine speed was kept constant of 3000 r/min.The NOx emission and thermal efficiency of engine with gasoline and hydrogen fuel operation at 1.4 kW power output are 5 g/kWh and 12.1 g/kWh,and 15% and 20.9% respectively.In order to reduce the NOx emission at source level,retarding spark timing,exhaust gas recirculation(EGR),and water injection techniques were studied.Nox emission decreased with spark timing retardation,EGR,and water injection.NOx emission with hydrogen at 1.4 kW power output decreased from 12.1 g/kWh with maximum brake torque(MBT)spark timing(10℃A bTDC)to 8.1 g/kWh with retarded spark timing(4℃A bTDC)due to decrease in the in-cylinder peak pressure and temperature.The Nox emission decreased to 6.1 g/kWh with 20% EGR due to thermal and chemical dilution effect.However,thermal efficiency decreased about 33% and 17% with spark timing retardation and 20EGR respectively as compared to that of MBT spark timing.But,in the case of water injection,the NOx emission decreased significantly without affecting the thermal efficiency of the engine and it is 5.6 g/kWh with water-hydrogen ratio of 4:1(water flow rate of 0.92 kg/h).Water injection is the best suitable method to reduce the NOx emission in a hydrogen fueled engine compared with the spark timing retardation and EGR technique.展开更多
Global warming and climate change are two key probing issues in the present context.The electricity sector and transportation sector are two principle entities propelling both these issues.Emissions from these two sec...Global warming and climate change are two key probing issues in the present context.The electricity sector and transportation sector are two principle entities propelling both these issues.Emissions from these two sectors can be offset by switching to greener ways of transportation through the electric vehicle (EV) and renewable energy technologies (RET).Thus,effective scheduling of both resources holds the key to sustainable practice.This paper presents a scheduling scenario-based approach in the smart grid.Problem formulation with dual objective function including both emissions and cost is developed for conventional unit commitment with EV and RET deployment.In this work,the scheduling and commitment problem is solved using the fireworks algorithm which mimics explosion of fireworks in the sky to define search space and the distance between associated sparks to evaluate global minimum.Further,binary coded fireworks algorithm is developed for the proposed scheduling problem in the smart grid.Thereafter,possible scenarios inconventional as well as smart grid are put forward.Following that,the proposed methodology is simulated using a test system with thermal generators.展开更多
In the present study, five different invert trap configurations （rectangular with and without lids on both sides; trapezoidal, trapezoidal with rectangular base and rectangular with trapezoidal base with lids on both...In the present study, five different invert trap configurations （rectangular with and without lids on both sides; trapezoidal, trapezoidal with rectangular base and rectangular with trapezoidal base with lids on both sides） were simulated for both two-dimensional （2D） and three-dimensional （3D） flow conditions for three sediment types （sand, styrocell and plastic beads） at six flow rates （0.35, 0.70, 1.05, 1.35, 4.55 and 9.95 L/s） for each trap. Computational fluid dynamics （CFD）-based modeling using FLUENT software with Renormalization Group （RNG） k-e model along with discrete phase model （DPM） were used in the simulations. A hexagonal/tetrahedral and map-type non-uniform grid was chosen to discretize the entire computational domain and a control volume finite difference method was used to solve the governing equations. The flow rates selected in the present study cover the entire range of flow rate expected for dry weather and monsoon. The simulation is capable of differentiating between 2D and 3D modeling of particle trajectories, the effects of flow rate and trap geometry on flow patterns developed in the trap. The sediment retention ratio for 2D is higher than that for 3D modeling for all flow conditions, particle types and model geometry due to inclusion of lateral effects in 3D modeling. The invert trap having rectangular shape with trapezoidal base is found to be the most efficient configuration in both 2D and 3D modeling.展开更多
Voltage stability is a major concern in heavily loaded distribution networks.Careful determination of control parameters for loadability enhancement may maximize the utilization of distribution networks.In applicable ...Voltage stability is a major concern in heavily loaded distribution networks.Careful determination of control parameters for loadability enhancement may maximize the utilization of distribution networks.In applicable studies,most of the approaches optimize real/reactive power losses for the current operating conditions of the distribution network.Although,these types of approaches increase the stability margin,such an increase may not be sufficient.The most important factor in loadability enhancement is representation of future load scenarios in addressing the optimization problem.In this paper a look ahead approach is developed for loadability enhancement of an unbalanced distribution system.The determination of the critical loading point is conventionally done using continuation power flow,which is computationally very demanding,and also complex for implementation in unbalanced distribution networks.Therefore,a new,computationally very efficient voltage stability indicator is developed here for determination of the loadability limit.The proposed methodology is demonstrated on IEEE 4 bus and 25 bus unbalanced distribution systems with different transformer connections.展开更多
基金supported by the Indian Institute of Technology Delhi (IIT Delhi)
文摘Though the formation of polysulfide is desirable,as it contributes to the capacity build-up,it must not leak into the electrolyte.The loss of polysulfide causes capacity fade,a change in the local chemistry of the electrolyte,and anode poisoning.Constant efforts are in progress to find suitable polysulfide-absorbing materials;however,the magical polysulfide absorber is yet to be discovered or developed.Experimental methods alone often fall short in accelerating the investigations may be due to the complex Nature of the testing.This review focuses on the importance of computational methods,particularly density functional theory(DFT),in screening suitable polysulfide absorbers.It highlights the critical role of anchoring materials in improving Na-S battery performance,including pristine and doped graphene,metal–organic frameworks,carbon Nanofibers,vanadium disulfide,MXenes,and metal sulfides.By examining adsorption energies,charge transfer mechanisms,and catalytic properties,this review provides insights into the design of advanced materials that can effectively immobilize polysulfides and enhance battery stability.The review aims to guide future research efforts toward the development of high-performance RT Na-S batteries through a comprehensive understanding of the polysulfide-absorbing materials.
文摘In heterogeneous traffic conditions, roundabout capacity is described by vehicle and driver characteristics which are different from traffic conditions in homogeneous conditions. In the present study, the capacity of the roundabout is determined using various capacity formulas such as gap acceptance models given by Highway Capacity Manual 2010 （US）, German model （2001）; empirical regression models given by TRRL （UK） and weaving models given by IRC： 65-1976 （India）. In addition, microscopic simulation model like VISSIM （PTV Ger- many） is also used to derive capacity values. Unlike the other capacity estimation models, VISSIM is helpful in estimating capacity values using geometric and driver characteristics and it can also simulate heterogeneous traffic condition accurately. Capacity is estimated after calibrating the simulation model （VISSIM） developed for the roundabout. This is achieved by incorporating different vehicle classes to represent the heterogeneous traffic environment, driver gap acceptance, and lane changeparameters. All the required inputs were extracted from the video using semi-automatic data collection methods. Data are used for the estimation of capacity values from dif- ferent methods mentioned above and for the calibration and validation of simulation model. The capacity values esti- mated form various formulas except German model are distinctly different from the field values and they are either overestimating or underestimating. Analysis of these observations reveals that the capacity values from VISSIM and German models are nearly matching with the field capacity.
文摘A general neural network based methodology that has the potential to replace the computationally-intensive site-specific seismic analysis of structures is proposed in this paper. The basic framework of the methodology consists of a feed forward back propagation neural network algorithm with one hidden layer to represent the seismic potential of a region and soil amplification effects. The methodology is implemented and verified with parameters corresponding to Delhi city in India. For this purpose, strong ground motions are generated at bedrock level for a chosen site in Delhi due to earthquakes considered to originate from the central seismic gap of the Himalayan belt using necessary geological as well as geotechnical data. Surface level ground motions and corresponding site-specific response spectra are obtained by using a one-dimensional equivalent linear wave propagation model. Spectral acceleration values are considered as a target parameter to verify the performance of the methodology. Numerical studies carried out to validate the proposed methodology show that the errors in predicted spectral acceleration values are within acceptable limits for design purposes. The methodology is general in the sense that it can be applied to other seismically vulnerable regions and also can be updated by including more parameters depending on the state-of-the-art in the subject.
文摘With the increasing use of metal foams in various engineering applications, investigation of their dynamic behaviour under varying strain rate is necessary. Closed cell aluminium fly ash foam developed through liquid metallurgy route was investigated for its stress--strain behaviour at different strain rates ranging from 700 s^-1 to 1950 s^-1. The numerical model of split Hopkinson pressure bar （SHPB） was simulated using commercially available finite element code Abaqus/Explicit. Validation of numerical simulation was carried out using available experimental and numerical results. Full scale stress--strain curves wez＇e developed for various strain rates to study the effect of strain rate on compressive strength and energy absorption. The results showed that the closed cell aluminium fly ash foam is sensitive to strain rate.
文摘Transmission tower-line systems are designed using static loads specified in various codes. This paper compares the dynamic response of a test transmission line with the response due to static loads given by Eurocode. Finite element design software SAP2000 was used to model the towers and lines. Non-linear dynamic analysis including the large displacement effects was carried out. Macroscopic aspects of wind coherence along element length and integration time step were investigated. An approach is presented to compare the probabilistic dynamic response due to 7 different stochastically simulated wind fields with the response according to EN-50341. The developed model will be used to study the response recorded on a test line due to the actual wind speed time history recorded. It was found that static load from EN overestimated the strength of conductor cables. The response of coupled system considering towers and cables was found to be different from response of only cables with fixed supports.
文摘Shock tube experiments were carried out to investigate dynamic behavior of Ultra-high hardness(UHH)steel and Aluminium(Al) sheets of 0.8 mm thickness at 0.55, 0.9 and 1.18 MPa peak-over pressure.Experimental results showed that center point deflection increases with an increase in peak-over pressure for Al sheets. However, UHH steel sheets showed negligible deformation when loaded at low peak-over pressures and showed sudden brittle failure at high peak-over pressures. Similar results were obtained by quasi-static testing, UHH steel failed abruptly while Al showed ductile behavior. Results from literature indicate that to protect structures against shock loading it is necessary that they dissipate energy via plastic deformation. The Al sheets were shown to deform plastically both in quasi-static and shock loading. Thus, hardness along with ductility is required to dissipate supersonic shock waves.
基金Project supported by Department of Science and Technology,Government of India(DST/TMD/CERI/C-24(g))。
文摘Transparent luminescent solar concentrator(LSC)is extensively regarded as the most promising sunlight tapping device for its application in buildings integrated with photovoltaics(BIPV)or as solar window glass.Conventional LSCs doped with organic dyes suffered from high reabsorption losses with no transparency;whereas,recently reported heavy metal-doped quantum dots avoided such losses but possessed the risk of high toxicity and low ambient stability.Thus,luminophores with massive spectral shifts and co rdial relationships with the enviro nment are very much desirable.In this paper,we report the fabrication of PMMA based transparent LSC embedded with nanocrystals of environmental friendiness and multispectral harvesting gadolinium oxysulphide(Gd_(2)O_(2) S:Er,Yb)fluorophore.The Gd_(2)O_(2) S:Er,Yb nanofluorophore absorbs various excitation wavelengths ranging from UV to NIR and emits in the visible region offering huge Stoke’s and anti-Stoke’s shift concurrently.The non-existent reabsorption losses and overlapping maxima of Gd_(2)O_(2) S:Er,Yb nanofluorophore generated photon flux with solar cells’responsivity enhance the efficiency characteristics of the LSC waveguide.Performance analysis of LSC as a function of varying nanofluorophore dispersion ratio and changing edge width optimizes the fabrication process and exhibits high power conversion efficiency of-6,93%and optical efficiency of-8.57%.The LSC slab demonstrates high photostability under irradiation for prolonged hours without any dip in the emission characteristics.The Gd_(2)O_(2) S:Er,Yb nanofluorophore diffused LSC waveguide offering spectral tunability,cost-reduction,efficiency enhancement,and high concentration factor whilst being sustainable for long term use makes it a fascinating transparent solar window.
文摘In this paper, the performance of various Pulse Position Modulation (PPM) schemes has been analysed for PIN and APD receivers in the presence of atmospheric turbulence. It is observed that the performance of the APD receiver is always better than that of the PIN receiver as expected. Among the various modulation schemes, the performance of Differential Amplitude PPM (DAPPM) scheme with more number of amplitude levels is better than that of the other schemes for the same single level peak amplitude. Further, the optimum gain of APD receiver does not change substantially for different modulation schemes and turbulent conditions.
文摘Seismic response of ground supported baseisolated liquid storage tanks are evaluated under bi-directional earthquakes. The base-isolated liquid storage tanks are modeled using mechanical analogs with two and three lumped masses (Model 1 and Model 2). Two types of isolation systems, such as sliding system and elastomeric system, are considered for the present study. The isolation systems are modeled using Wen’s equation for hysteretic isolation systems. Response of base-isolated liquid storage tanks, evaluated through two different modeling approaches, is compared. Both the models predict similar sloshing displacement. The effect of interaction between the mutually perpendicular seismic responses of the isolator is investigated for both the models. It is observed that interaction affects the peak seismic response of the base-isolated liquid storage tanks significantly, under the bi-directional earthquake components.
文摘The Al-Si alloy with near eutectic composition has been conventionally used as a piston material for automobile applications. It is required to possess high abrasive wear resistance for enhanced life of the engine. The alloy is known to have fairly good wear resistance due to increased percentage of silicon present in fine form. In the present investigation, Al-SiC particulate composites have been studied for their wear resistance against emery paper (400 grit SiC particles) counterface and a comparison has been made with existing piston alloy i.e. Al-Si alloy. The Al-SiC composites have been prepared using Liquid Metallurgy technique employing 2124 Al alloy as the base material with 10 and 20 % SiC particulates by weight. The abrasive wear study has been conducted on a Pin on Disc machine. The wear rate in terms of weight loss per unit sliding distance as well as the volumetric wear rate have been obtained for the Al-SiC composites. The characteristics of worn surface were investigated using SEM. The composites are found to possess very high wear resistance as compared to Al-Si piston alloy. The results have been discussed and important conclusions are outlined.
文摘In the present work, one-dimensional nanostructures of silicon oxide (SiOx) have been synthesized by thermal annealing method with and without chromium thin film on silicon substrate. The synthesis was carried out at different process temperatures ranging from 1000°C to 1100°C by using gold/chromium (Au/Cr) catalysts stack layer on the Si substrate in nitrogen (N2) ambience. The as-synthesized SiOx nanostructures have tetragonal rutile structure and show polycrystalline nature. The SEM images reveal wire-like nanostructures on the substrate with and without chromium thin film. Under the catalytic reaction of the gold/chromium metal, the density of SiOx nanowires is enhanced, since the Cr layer serves as a diffusion barrier for the diffusion of the gold downwards into the Si substrate. The vapor-liquid solid (VLS) growth mechanism is found to be dominant in the growth of SiOx nanowires. Furthermore, X-Ray diffraction microscopy (XRD) and Photoluminescence spectroscopy (PL) analysis conclude the defect free growth of the SiOx nanowires on gold/chrome/silicon substrate.
文摘This paper presents the formulation of the possibilistic Renyi entropy function from the Renyi entropy function using the framework of Hanman-Anirban entropy function. The new entropy function is used to derive the information set features from keystroke dynamics for the authentication of users. A new composite fuzzy classifier is also proposed based on Mamta-Hanman entropy function and applied on the Information Set based features. A comparison of the results of the proposed approach with those of Support Vector Machine and Random Forest classifier shows that the new classifier outperforms the other two.
文摘Nearly 95% of monomers or chemical intermediates used today are based on fossilized carbon such as coal and petroleum. This has resulted in a high rate of depletion of fossilized reserves, continuous escalation in petroleum prices, environmental impact with the increase in emission of greenhouse gases, and accumulation of non-biodegradable waste on earth. Current global main challenges are moving towards green sources - need for vast new and sustainable material resources;supplement, reuse and replace petroleum based polymeric materials;biodegradability of materials to prevent build up of waste;toxicity associated with the preparation, usage and environmental safety. Recent investigations are therefore, focused on procuring materials from the plant resources, agricultural waste and their utility in synthesis of polymeric materials. Amongst the polymers derived from natural resources poly(lactic acid) is a leading candidate. Commercial quantities of natural oil-based polyols such as castor, soya bean oil have been available over the past several years and currently used for synthesis of? polyesters, polyurethanes etc, but today many other? natural materials are also being investigated. It should be possible to produce sustainable polymers commercially and economically.
文摘This paper proposes a novel equalizer, termed here as Evolutionary MPNN, where a complex modified probabilistic Neural Networks (MPNN) acts as a filter for the detected signal pattern. The neurons were embedded with optimization algorithms. We have considered two optimization algorithms, Bacteria Foraging Optimization (BFO) and Ant Colony Optimization (ACO). The proposed structure have the ability to process complex signals also can perform for slowly varying channels. Also, Simulation results prove the superior performance of the proposed equalizer over the existing MPNN equalizers.
文摘The prediction of water quality in terms of variables like dissolved oxygen (DO), biochemical oxygen demand (BOD), pH value, total dissolved solids (TDS) and salinity etc. is useful for evaluating the use of water for various related purposes. The widely used Streeter and Phelps models for computing biochemical oxygen demand and its impact on dissolved oxygen do not account for the settleable component of BOD and related implications. The model also does not account for the impact of storage zone on the stream’s DO. In the present work an attempt is made to develop a model which simultaneously accounts for the settleable component of BOD and the effect of storage zones onriver’s DO. An application of the model to real field data suggests that the cumulative impact of settleable BOD and presence of storage zone in the river is to shift the critical deficit closer to the point source and magnify its amount.
基金a seed grant from IIT Delhi(SGNF148)supported by the JST-ERATO Yamauchi Materials SpaceTectonics Project(JPMJER2003)+2 种基金the ARC Australian Laureate Fellowship(FL230100095)the UQ-Yonsei International Joint Research Projectthe support from JSPS Postdoctoral Fellowships for Research in Japan。
文摘Commercial-level sodium metal batteries require electrolytes with high ionic mobility and excellent thermo-mechanical and electrochemical stability.Conventional flammable liquid electrolytes,prone to dendrite growth and unstable interfacial reactions,rarely perform beyond coin-cell demonstrations.To address these shortcomings,a multifunctional composite quasi-solid polymer electrolyte(QSPE)that incorporates boron nitride(BN)as an engineered filler in a highly conductive polymer blend system has been developed.The optimized formation(15BN QSPE)delivers a room-temperature ionic conductivity of 2.15 m S cm^(-1)and a sodium-ion transference number of 0.80.Molecular dynamics simulations elucidate the coordination environment and show improved transport in the presence of BN.BN is chemically active and bifunctional:boron acts as an electron acceptor,interacting with solvents and macromolecules,while nitrogen coordinates with sodium ions,tailoring the solvation environment and transport pathways to promote efficient ion migration.The 15BN QSPE is self-extinguishing,resists oxidative thermal degradation,and enables stable cycling in symmetric sodium cells for>1400 h at0.5 m A cm^(-2).A Prussian blue full cell achieves>1500 stable cycles at 1C with -99% Coulombic efficiency in coin-cell configuration.A two-layer pouch cell with dual 15BN QSPE layers delivers 600 stable cycles at 0.125C and withstands rigorous mechanical abuse.These results position 15BN QSPE as a scalable,highperformance electrolyte offering enhanced safety and efficiency for next-generation sodium metal batteries.
文摘The experimental tests were carried out on a single cylinder hydrogen fueled spark ignition(SI)generator set with different spark timings(4-20℃A bTDC),exhaust gas recirculation(EGR)up to 28% by volume and water injection up to 1.95 kg/h(maximum water to fuel mass ratio of 8:1).The engine speed was kept constant of 3000 r/min.The NOx emission and thermal efficiency of engine with gasoline and hydrogen fuel operation at 1.4 kW power output are 5 g/kWh and 12.1 g/kWh,and 15% and 20.9% respectively.In order to reduce the NOx emission at source level,retarding spark timing,exhaust gas recirculation(EGR),and water injection techniques were studied.Nox emission decreased with spark timing retardation,EGR,and water injection.NOx emission with hydrogen at 1.4 kW power output decreased from 12.1 g/kWh with maximum brake torque(MBT)spark timing(10℃A bTDC)to 8.1 g/kWh with retarded spark timing(4℃A bTDC)due to decrease in the in-cylinder peak pressure and temperature.The Nox emission decreased to 6.1 g/kWh with 20% EGR due to thermal and chemical dilution effect.However,thermal efficiency decreased about 33% and 17% with spark timing retardation and 20EGR respectively as compared to that of MBT spark timing.But,in the case of water injection,the NOx emission decreased significantly without affecting the thermal efficiency of the engine and it is 5.6 g/kWh with water-hydrogen ratio of 4:1(water flow rate of 0.92 kg/h).Water injection is the best suitable method to reduce the NOx emission in a hydrogen fueled engine compared with the spark timing retardation and EGR technique.
文摘Global warming and climate change are two key probing issues in the present context.The electricity sector and transportation sector are two principle entities propelling both these issues.Emissions from these two sectors can be offset by switching to greener ways of transportation through the electric vehicle (EV) and renewable energy technologies (RET).Thus,effective scheduling of both resources holds the key to sustainable practice.This paper presents a scheduling scenario-based approach in the smart grid.Problem formulation with dual objective function including both emissions and cost is developed for conventional unit commitment with EV and RET deployment.In this work,the scheduling and commitment problem is solved using the fireworks algorithm which mimics explosion of fireworks in the sky to define search space and the distance between associated sparks to evaluate global minimum.Further,binary coded fireworks algorithm is developed for the proposed scheduling problem in the smart grid.Thereafter,possible scenarios inconventional as well as smart grid are put forward.Following that,the proposed methodology is simulated using a test system with thermal generators.
文摘In the present study, five different invert trap configurations （rectangular with and without lids on both sides; trapezoidal, trapezoidal with rectangular base and rectangular with trapezoidal base with lids on both sides） were simulated for both two-dimensional （2D） and three-dimensional （3D） flow conditions for three sediment types （sand, styrocell and plastic beads） at six flow rates （0.35, 0.70, 1.05, 1.35, 4.55 and 9.95 L/s） for each trap. Computational fluid dynamics （CFD）-based modeling using FLUENT software with Renormalization Group （RNG） k-e model along with discrete phase model （DPM） were used in the simulations. A hexagonal/tetrahedral and map-type non-uniform grid was chosen to discretize the entire computational domain and a control volume finite difference method was used to solve the governing equations. The flow rates selected in the present study cover the entire range of flow rate expected for dry weather and monsoon. The simulation is capable of differentiating between 2D and 3D modeling of particle trajectories, the effects of flow rate and trap geometry on flow patterns developed in the trap. The sediment retention ratio for 2D is higher than that for 3D modeling for all flow conditions, particle types and model geometry due to inclusion of lateral effects in 3D modeling. The invert trap having rectangular shape with trapezoidal base is found to be the most efficient configuration in both 2D and 3D modeling.
基金This work was supported by Department of Science and Technology(DST),SERB under the project no.SB/FTP/ETA-0183/2013.
文摘Voltage stability is a major concern in heavily loaded distribution networks.Careful determination of control parameters for loadability enhancement may maximize the utilization of distribution networks.In applicable studies,most of the approaches optimize real/reactive power losses for the current operating conditions of the distribution network.Although,these types of approaches increase the stability margin,such an increase may not be sufficient.The most important factor in loadability enhancement is representation of future load scenarios in addressing the optimization problem.In this paper a look ahead approach is developed for loadability enhancement of an unbalanced distribution system.The determination of the critical loading point is conventionally done using continuation power flow,which is computationally very demanding,and also complex for implementation in unbalanced distribution networks.Therefore,a new,computationally very efficient voltage stability indicator is developed here for determination of the loadability limit.The proposed methodology is demonstrated on IEEE 4 bus and 25 bus unbalanced distribution systems with different transformer connections.
