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In situ TEM observations and molecular dynamics simulations of deformation defect activities in Mg via nanoindentation

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Journal of Magnesium and Alloys 2023年第12期11卷 4513-4524页

作者： Yi-Cheng Lai Yubin Ying digvijay yadav Jose Guerrero Yong-Jie Hu Kelvin Y.Xie Department of Materials Science and Engineering Texas A&M UniversityCollege StationTX 77845USA Department of Materials Science and Engineering Drexel UniversityPhiladelphiaPA 19104USA

In this work, we performed in situ nanoindentation in TEM to capture the real-time dislocation and twinning activities in pure Mg during loading and unloading. We demonstrated that the screw component of dislocations glides continuously, while the edge components rapidly become sessile during loading. The twin tip propagation is intermittent, whereas the twin boundary migration is more continuous. During unloading, we observed the elastic strain relaxation causes both dislocation retraction and detwinning. Moreover,we note that the plastic zone comprised of dislocations in Mg is well-defined, which contrasts with the diffused plastic zones observed in face-centered cubic metals under the nanoindentation impressions. Additionally, molecular dynamics simulations were performed to study the formation and evolution of deformation-induced crystallographic defects at the early stages of indentation. We observed that,in addition to dislocations, the I1stacking fault bounded with a Frank loop can be generated from the plastic zone ahead of the indenter, and potentially serve as a nucleation source for abundant dislocations observed experimentally. These new findings are anticipated to provide new knowledge on the deformation mechanisms of Mg, which are difficult to obtain through conventional ex situ approaches. These observations may serve as a baseline for simulation work that investigate the dynamics of dislocation slip and twinning in Mg and alloys.

关键词： In situ TEM Molecular dynamics simulation Dislocation Twinning Mg Nanoindentation

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Microstructure and mechanical properties of spark plasma-sintered La_(2)O_(3) dispersion-strengthened W-Ni-Fe alloy

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Rare Metals 2021年第8期40卷 2230-2236页

作者： Muthuchamy AyyappaRaj digvijay yadav Dinesh K.Agrawal Raja Annamalai Arunjunai Rajan School of Mechanical Engineering VITVellore632014India Materials Research Institute University ParkPennsylvaniaPA16802USA Centre for Innovative Manufacturing Research VITVellore632014India

An investigation of lanthanum oxide(La_(2)O_(3))addition to tungsten heavy alloy(WHA)with a ternary composition of W-7 Ni-3 Fe was reported in this study.The mixed powders were sintered using spark plasma sintering(SPS)technique.La_(2)O_(3)was added in increments of 0.25 wt%,0.50 wt%,0.75 wt%and 1.00 wt%to WHA,respectively.The sintered samples were characterized for microstructural evolution and mechanical properties.The influences of La_(2)O_(3)addition on density,grain size,hardness,ultimate tensile strength(UTS)and ductility on W-7 Ni-3 Fe system were discussed in this study.The highest relative sintered density of 87.95%was obtained for 0.25 wt%La_(2)O_(3)addition to W-7 Ni-3 Fe.The lowest grain size of 7.89μm was observed for 1.00 wt%La_(2)O_(3)addition.Similarly,the highest hardness and UTS of HV 533 and1110 MPa,respectively,were also obtained for the same composition.Scanning electron microscopy(SEM)and energy-dispersive spectroscopy(EDS)of the samples revealed homogenous distribution of La_(2)O_(3)in the alloy matrix.Fractography of the sintered alloy samples revealed W-W intergranular fracture.

关键词： Tungsten heavy alloys Lanthanum oxide Spark plasma sintering Microstructure Mechanical properties

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Effects of dynamic recrystallization and strain-induced dynamic precipitation on the corrosion behavior of partially recrystallized Mg-9Al-lZn alloys

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Journal of Magnesium and Alloys 2020年第4期8卷 1016-1037页

作者： Yenny Cubides Dexin Zhao Lucas Nash digvijay yadav Kelvin Xie Ibrahim Karaman Homero Castaneda Department of Materials Science and Engineering Texas A&M University575 Ross StreetCollege StationTX 77840USA Department of Engineering Technology and Industrial Distribution 106 Ross StreetCollege StationTX 77843USA National Corrosion and Materials Reliability Laboratory 1041 RELLIS PkwyBryanTX 77807USA

The corrosion susceptibility of recrystallized and un-recrystallized grains in equal channel angular pressed(ECAPed)Mg-9Al-lZn(AZ91)alloys immersed in chloride containing media was investigated through immersion testing and an electrochemical microcell technique coupledwith high resolution techniques such as scanning Kelvin probe force microscopy(SKPFM),transmission electron microscopy(TEM),andelectron backscatter diffraction(EBSD).During ECAP,dynamic recrystallization(DRX)and strain-induced dynamic precipitation(SIDP)simultaneously occurred,resulting in a bimodal grain structure of original elongated coarse grains and newly formed equiaxed fine grainswith a large volume fraction ofβ-Mg17Al12 precipitates.Corrosion preferentially initiates and propagates in the DRXed grains,owing tothe greater microchemistry difference between theβ-Mg17Al12 precipitates formed at the DRXed grain boundaries and the adjacentα-Mgmatrix,which induces a strong microgalvanic coupling between these phases.Additionally,the weaker basal texture of the DRXed grainsalso makes these grains more susceptible to electrochemical reactions than the highly textured un-DRXed grains.The influence of dynamicrecrystallization and dynamic precipitation was also studied in ECAPed alloys with differenl levels of deformation strain through corrosion andelectrochemical techniques.Increasing the strain level led to a more uniform corrosion with a shallow penetration depth,lower corrosion ratevalues,and higher protective ability of the oxide film.Furthermore,higher levels of strain resulted in greater hardness values of the ECAPedalloys.The superior corrosion resistance and strength of the ECAPed alloys with increasing strain level was attributed to the combination ofsmaller DRXed grain size,higher DRX ratio,and higher volume fraction of uniformly distributed fineβ-Mg17Al12 precipitates.c 2020 Published by Elsevier B.V.on behalf of Chongqing University.

关键词： Magnesium alloy Bimodal grain structure Dynamic recrystallization Dynamic precipitation Severe plastic deformation Microgalvanic coupling

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Evaluation of intersection conflict warning system at unsignalized intersections:A review

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Journal of Traffic and Transportation Engineering(English Edition) 2023年第4期10卷 530-547页

作者： Yashasvi Rachakonda digvijay S.Pawar Department of Civil Engineering Indian Institute of Technology HyderabadKandiMedak 502285India

Unsignalized intersections are identified as the critical locations due to higher number of road crashes at these locations.The primary causes of crashes at unsignalized intersections are limited sight distance,incorrect assessment of gaps by drivers on the minor road,and higher speeds of vehicles on the major road.In an effort to improve safety and reduce the severity of crashes at unsignalized intersections,an intelligent transportation system(ITS)called the intersection conflict warning system(ICWS)has been developed.The ICWS consists of an activated warning sign and sensors that detect vehicles approaching the intersection.This paper aims to summarize the performance evaluation of ICWS that has been published in the literature.The review commences with an overview of the purpose of designing and installing ICWS at unsignalized intersections.It then discusses driving performance measures considered to evaluate the effectiveness of ICWS in three different environments,i.e.,real world,driving simulator,and simulations,and their results are presented.The paper also discusses the type of sensors used to detect vehicles approaching the intersection and their accuracy in vehicle detection.The results reveal that ICWS had substantially improved driver behaviour.In the presence of ICWS,drivers resulted in shorter reaction time,lower approach speed,increased critical gap acceptance,and reduction in conflicts.An improvement in the performance of ICWS can be achieved by educating drivers about the sign,maintaining system reliability,and further examining the effect of various traffic factors,driver factors,and environmental factors on ICWS.The findings of this study can help researchers and engineers to design a better ICWS that can greatly enhance driving performance and safety at unsignalized intersections.

关键词： Unsignalized intersection Intersection conflict warning system Collision avoidance system Driving simulator Driving performance Sensors

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Potential and performance estimation of free-standing and building integrated photovoltaic technologies for different climatic zones of India

能源与人工环境(英文)

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能源与人工环境(英文) 2022年第1期3卷 40-55页

作者： digvijay Singh Ajay Kumar Gautam Rubina Chaudhary School of Energy and Environmental Studies Devi Ahilya UniversityIndore 452001India

The role of Photovoltaic technologies integrated or attached to the building envelope is crucial in managing the building energy demand.In this paper,the performance of PV technologies with the mounting methods of Build-ing integrated and Free-standing(Building attached)is discussed for six different climate zone of the country.A PVGIS program proposed with three PV cell technologies(Crystalline Silicon,Copper indium diselenide,Cad-mium Telluride)is used to evaluate monthly energy generation potential and losses of the 2 kW p grid-connected PV system at the latitude and 90°.A 2 kW p PV system is chosen for Economic Weaker Section(EWS)housing schemes depending upon the roof area.From the evaluation,the performance parameter has been estimated.A new parameter Energy Deviation(ED),is proposed to choose the best PV technology in terms of performance.The results of ED agree with the parameters Performance Ratio(PR)and Capacity Factor(CF)defined under the IEC Standard 61724.The potential generation of PV technologies at 90°varies from 41%(Warm and Humid)to 64%(Cold and Sunny)when compared with the latitude.In case of Cold and Sunny and Cold and Cloudy at 90°,the generation performance of Copper indium diselenide is found better in Building integrated and Free-standing mounting methods,respectively.For the remaining zones,Cadmium Telluride technology shows better results.The Percentage loss in the system is found to be minimum in the case of Cold and Sunny,varies between 17%and 25%,and maximum is found for Warm and Humid and varies between 23.2%and 33.4%for the proposed PV technologies.The grid feed-in energy from these EWS houses for all the technologies and climatic zones is found above 45%.It is seen that the combined energy generation from the envelopes(Roof,walls,and facades)makes the houses energy plus in nature.The study has important implications for the government to promote the building integrated Photovoltaic policies in the country.

关键词： PV technologies Building Integrated Free-standing Energy Deviation Performance Ratio Capacity Factor

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A Novel Convolutional Neural Networks Based Spinach Classification and Recognition System

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Computers, Materials & Continua 2022年第10期73卷 343-361页

作者： Sankar Sennan digvijay Pandey Youseef Alotaibi Saleh Alghamdi Department of Computer Science and Engineering Sona College of TechnologySalem636005India Department of Technical Education Department of Electronics EngineeringInstitute of Engineering and TechnologyDr.A.P.J.Abdul Kalam Technical UniversityLucknowIndia Department of Computer Science College of Computer and Information SystemsUmm Al-Qura UniversityMakkah21955Saudi Arabia Department of Information Technology College of Computers and Information TechnologyTaif UniversityTaif21944Saudi Arabia

In the present scenario,Deep Learning(DL)is one of the most popular research algorithms to increase the accuracy of data analysis.Due to intra-class differences and inter-class variation,image classification is one of the most difficult jobs in image processing.Plant or spinach recognition or classification is one of the deep learning applications through its leaf.Spinach is more critical for human skin,bone,and hair,etc.It provides vitamins,iron,minerals,and protein.It is beneficial for diet and is readily available in people’s surroundings.Many researchers have proposed various machine learning and deep learning algorithms to classify plant images more accurately in recent years.This paper presents a novel Convolutional Neural Network(CNN)to recognize spinach more accurately.The proposed CNN architecture classifies the spinach category,namely Amaranth leaves,Black nightshade,Curry leaves,and Drumstick leaves.The dataset contains 400 images with four classes,and each type has 100 images.The images were captured from the agricultural land located at Thirumanur,Salem district,Tamil Nadu.The proposed CNN achieves 97.5%classification accuracy.In addition,the performance of the proposed CNN is compared with Support Vector Machine(SVM),Random Forest,Visual Geometry Group 16(VGG16),Visual Geometry Group 19(VGG19)and Residual Network 50(ResNet50).The proposed provides superior performance than other models,namely SVM,Random Forest,VGG16,VGG19 and ResNet50.

关键词： Accuracy convolutional deep learning plant neural networks spinach

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EACR-LEACH:Energy-Aware Cluster-based Routing Protocol for WSN Based IoT

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Computers, Materials & Continua 2022年第8期72卷 2159-2174页

作者： Sankar Sennan Kirubasri Youseef Alotaibi digvijay Pandey Saleh Alghamdi Department of Computer Science and Engineering Sona College of TechnologySalem636005India Department of Computer Science College of Computer and Information SystemsUmm Al-Qura UniversityMakkah21955Saudi Arabia Department of Technical Education Department of Electronics EngineeringInstitute of Engineering and TechnologyDr.A.P.J.Abdul Kalam Technical UniversityLucknowIndia Department of Information Technology College of Computers and Information TechnologyTaif UniversityTaif21944Saudi Arabia

Internet of Things(IoT)is a recent paradigm to improve human lifestyle.Nowadays,number devices are connected to the Internet drastically.Thus,the people can control and monitor the physical things in real-time without delay.The IoT plays a vital role in all kind of fields in our world such as agriculture,livestock,transport,and healthcare,grid system,connected home,elderly people carrying system,cypher physical system,retail,and intelligent systems.In IoT energy conservation is a challenging task,as the devices are made up of low-cost and low-power sensing devices and local processing.IoT networks have significant challenges in two areas:network lifespan and energy usage.Therefore,the clustering is a right choice to prolong the energy in the network.In LEACH clustering protocol,sometimes the same node acts as CH again and again probabilistically.To overcome these issues,this paper proposes the Energy-Aware Cluster-based Routing(EACRLEACH)protocol in WSN based IoT.The Cluster Head(CH)selection is a crucial task in clustering protocol inWSN based IoT.In EACR-LEACH,the CH is selected by using the routing metrics,Residual Energy(RER),Number of Neighbors(NoN),Distance between Sensor Node and Sink(Distance)and Number of Time Node Act as CH(NTNACH).An extensive simulation is conducted on MATLAB 2019a.The accomplishment of EACR-LEACH is compared to LEACH and SE-LEACH.The proposed EACR-LEACH protocol extends the network’s lifetime by 4%-8%and boosts throughput by 16%–24%.

关键词： Cluster head clustering protocol internet of things routing metrics wireless sensor networks

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Analyzing variations in spatial critical gaps at two-way stop controlled intersections using parametric and non-parametric techniques

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Journal of Traffic and Transportation Engineering(English Edition) 2021年第1期8卷 129-138页

作者： digvijay S.Pawar Gopal R.Patil Department of Civil Engineering Indian Institute of Technology HyderabadKandi 502285India Department of Civil Engineering Indian Institute of Technology BombayPowai 400076India

At two-way stop controlled(TWSC)intersections drivers on minor stream are generally at risk because of the difficulty in judging safe gap between major stream vehicles.Any misjudgment by the driver while choosing gap may result in a collision with major stream vehicle.This paper provides important insights for determining and analyzing spatial critical gaps of drivers at high speed and medium speed TWSC intersections.The critical gap line(CGL)fitted for the accepted and rejected gaps using parametric(binary logit model-BLM)and non-parametric(support vector machines-SVM)techniques gives critical gap values at 15 th,50 th and 85 th percentile speeds.The evaluation of spatial critical gap with respect to major road vehicle(conflicting vehicle)speed makes it easier to understand the impact of variation in speed on spatial gaps accepted by the drivers on the minor road.The logit models developed revealed that the probability of accepting gap decreases with increase in the speed of the conflicting vehicle and it increases with increase in the distance of conflicting vehicle.The spatial critical gaps estimated using support vector machines were found in close approximation with those estimated using binary logit model.The study results showed that SVMs have very good potential to be an alternative tool for the estimation of driver's critical gap.The spatial critical gaps corresponding to 15 th,50 th and 85 th percentile speeds for medium speed intersections were 32 m,38 m and 46 m respectively and for high speed intersections these values were 64 m,76 m and 104 m respectively.The increase in the magnitude of gap value with respect to the percentile speed clearly states the effect of speed on spatial gaps.The insights from the study can be used to suggest various measures to improve the safety of crossing drivers at uncontrolled intersections.

关键词： Traffic engineering Spatial critical gaps Uncontrolled intersections Logit model SVM Driver behavior

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Reconfigurable control as actuator fault-tolerant control design for power oscillation damping

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Protection and Control of Modern Power Systems 2020年第1期5卷 70-81页

作者： digvijay V.Nair MSR Murty Faculty of Science&Technology IFHE HYDERABADShankerpally Road501203 HyderabadIndia Dept.of EEE CMR College of Engineering&TechnologyMedchal Road501401 HyderabadIndia

This paper presents design of an self contained actuators unit in wide area damping control of power system in stabilizing system response for both nominal system condition and during actuator faults.First it is presented that use of multiple actuators in wide area control aid in improving damping in power system.A wide area damping controller feeding multiple actuators to satisfy multiple objectives in wide area damping control of power system is designed.Minimization of infinity norm of closed loop transfer function of power system with wide area controller in feedback path&closed loop poles placement techniques are used in controller synthesis.Second a reconfigurable control on the lines of fault hiding principle is added to the controller design to maintain system damping to pre-fault level in case of actuator faults.A reconfiguration component(RC)is activated on occurrence of actuator fault thereby reconfiguring system dynamics and redistributing wide area control signal among remaining active actuators.RC together with remaining active actuators and under same wide area damping controller maintains system damping to pre-fault level thereby preserving system dynamic response.In the reconfigurable control design presented here no new actuators outside the unit of actuators designed for wide area damping control is required.This makes for an self contained actuators unit in wide area damping control of power system both for nominal system condition and for system affected by actuator faults.A two area power system model is considered here for demonstrating effectiveness of designed robust damping controller with multiple outputs feeding multiple actuators in wide area control and illustrating the idea of self contained actuators unit for maintaining system damping in case of actuator faults.

关键词： Wide area control Robust damping controller Actuator fault Reconfigurable control Reconfiguration component Self contained actuators unit Power oscillations

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Electro-optically tunable self-focusing and self-defocusing in KTP crystals by a cascaded second-order process

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Chinese Optics Letters 2016年第12期14卷 103-107页

作者： Ruma Debnath digvijay Singh Hada Susheel Kumar Beda Ardhendu Saha Department of Electrical Engineering National Institute of TechnologyAgartala

We report the transformation of a linear electro-optically tunable non-phase-matched second-order nonlinear process into a cascaded second-order nonlinear process in a bulk KTP crystal to generate the effect of electrooptically tunable Kerr-type nonlinearity. By applying an electric field on the x–y plane, parallel to the z-axis of the crystal, phase mismatch is created, which introduces a nonlinear phase shift between the launched and reconverted fundamental waves from the generated second harmonic wave. Due to the nonuniform radial intensity distribution of a Gaussian beam, a curvature will be introduced into the fundamental wavefront, which focuses or defocuses the incident beam while propagating through the crystal.

关键词： tunable cascaded optically focusing wavefront applying nonlinearity created harmonic matching

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