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Microstructure,mechanical and corrosion behavior of high strength AA7075aluminium alloy friction stir welds-Effect of post weld heat treatment

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Defence Technology（防务技术） 2015年第4期11卷 362-369页

作者： P.vijaya kumar G.Madhusudhan Reddy k.Srinivasa Rao Department of Mechanical Engineering R.I.T. Defence Metallurgical Research Laboratory Department of Metallurgical Engineering Andhra University

High strength aluminium alloy AA7075(Al-Zn-Mg-Cu) is a precipitate hardenable alloy widely used in the aerospace,defense,marine and automobile *** of the heat treatable aluminium alloys in all these sectors is ever-increasing owing to their excellent strength-toweight ratio and reasonably good corrosion *** shortage in corrosion resistance,however,usually poses negative concern about their reliability and lifetime when they service in the variable marine *** alloys also exhibit low weldability due to poor solidification microstructure,porosity in fusion zone and lose their mechanical properties when they are welded by fusion welding *** stir welding(FSW) is a reliable technique to retain the properties of the alloy as the joining takes place in the solid *** welds are susceptible to corrosion due to the microstructural changes in the weld nugget during *** this work,the effect of post weld treatments,viz.,peak aging(T6) and retrogression & reaging(RRA),on the microstructure,mechanical properties and pitting corrosion has been *** stir welding of 8 mm-thick AA7075 alloy was carried *** microstructural changes of base metal and nugget zone of friction stir welds were studied using optical microscopy,scanning electron microscopy and transmission electron *** and hardness test of base metal and welds has been carried *** corrosion resistance was determined through dynamic polarization *** was observed that the hardness and strength of weld were observed to be comparatively high in peak aged(T6) condition but the welds showed poor corrosion *** resistance to pitting corrosion was improved and the mechanical properties were maintained by RRA *** resistance to pitting corrosion was improved in RRA condition with the minimum loss of weld strength.

关键词： 7075铝合金高强度铝合金搅拌摩擦焊耐腐蚀性热处理效果微观结构焊缝机械性能

Microstructure and pitting corrosion of armor grade AA7075 aluminum alloy friction stir weld nugget zone-Effect of post weld heat treatment and addition of boron carbide

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Defence Technology（防务技术） 2015年第2期11卷 166-173页

作者： P.vijaya kumar G.MADHUSUDHAN REDDY k.SRINIVASA RAO Department of Mechanical Engineering R.I.T. Defence Metallurgical Research Laboratory Department of Metallurgical Engineering Andhra University

Friction stir welding(FSW) of high strength aluminum alloys has been emerged as an alternative joining technique to avoid the problems during fusion *** recent times FSW is being used for armor grade AA7075 aluminum alloy in defense,aerospace and marine applications where it has to serve in non uniform loading and corrosive *** though friction stir welds of AA7075 alloy possess better mechanical properties but suffer from poor corrosion *** present work involves use of retrogression and reaging(RRA) post weld heat treatment to improve the corrosion resistance of welded joints of aluminum *** attempt also has been made to change the chemical composition of the weld nugget by adding B4C nano particles with the aid of the FSW on a specially prepared base metal plate in butt *** effects of peak aged condition(T6),RRA and addition of B4C nano particles on microstructure,hardness and pitting corrosion of nugget zone of the friction stir welds of AA7075 alloy have been *** though RRA improved the pitting corrosion resistance,its hardness was slightly *** improvement in pitting corrosion resistance was achieved with addition of boron carbide powder and post weld heat treatment of RRA.

关键词： 7075铝合金搅拌摩擦焊焊后热处理碳化硼颗粒抗点蚀微观结构装甲 7075合金

Control of BLDC motor using MRPID controller with modified landsman converter

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International Journal of Intelligent Computing and Cybernetics 2021年第4期14卷 664-685页

作者： Murali Dasari A.Srinivasula Reddy M.vijaya kumar Electrical Engineering Jawaharlal Nehru Technological University AnantapuramuAnanthapurIndia CMR Engineering College SecunderabadIndiaand Electrical and Electronics Engineering Jawaharlal Nehru Technological University AnantapuramuAnanthapurIndia

Purpose-The principal intention behind the activity is to regulate the speed,current and commutation of the brushless DC(BLDC)***,the authors can control the ***/methodology/approach-In order to regulate the current and speed of the motor,the Multiresolution PID(MRPID)controller is *** altered Landsman converter is utilized in this proposed suppression circuit,and the obligation cycle is acclimated to acquire the ideal DC-bus voltage dependent on the speed of the BLDC *** adaptive neuro-fuzzy inference system-elephant herding optimization(ANFISEHO)calculation mirrors the conduct of the procreant framework in ***-Brushless DC motor’s dynamic properties are created,noticed and examined by MATLAB/Simulink *** performance will be compared with existing genetic ***/value-The presented approach and performance will be compared with existing genetic algorithms and optimization of different structure of BLDC motor.

关键词： Brushless DC(BLDC)motors Elephant herding optimization(EHO) Adaptive neuro-fuzzy inference system(ANFIS) Landsman converter

Design of a robust PID-PSS for an uncertain power system with simplified stability conditions

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Protection and Control of Modern Power Systems 2020年第1期5卷 222-237页

作者： vijaya Lakshmi A.S.V Ramalinga Raju Manyala Siva kumar Mangipudi Department of EEE G.V.P College of Engineering for WomenVisakhapatnamIndia Department of EEE JNTU KakinadaKakinadaIndia Department of EEE Gudlavalleru Engineering CollegeGudlavalleruAndhra PradeshIndia

In a deregulated power system uncertainty exists and lack of sufficient damping can lead to Low FrequencyOscillations (LFO). The problem can be addressed using robust Power System Stabilizers (PSS). In this paper, anoptimal procedure to design a robust PID-PSS using interval arithmetic for the Single Machine Infinite Bus (SMIB)power system is proposed. The interval modelling captures the wide variations of operating conditions in boundsof system coefficients. In the proposed design procedure, simple and new closed loop stability conditions for anSMIB interval system are developed and are used to design an optimum PID-PSS for improving the performance ofan SMIB system. The optimum PID-PSS is attained by tuning the parameters using the FMINCON tool provided inMATLAB. The robustness of the proposed PID-PSS design is validated and compared to other notable methods inthe literature when the system is subjected to different uncertainties. The simulation results and performance errorvalues show the effectiveness of the proposed robust PID-PSS controller.

关键词： Low frequency oscillations Uncertainty Power system stabilizer Robust controller Interval systems

Novel benzimidazole derived naphthalimide triazoles: synthesis, antimicrobial activity and interactions with calf thymus DNA

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Science China Chemistry 2015年第3期58卷 483-494页

作者： Yun-Lei Luo kishore Baathulaa vijaya kumar kannekanti Cheng-He Zhou Gui-Xin Cai key Laboratory of Applied Chemistry of Chongqing Municipality Institute of Bioorganic & Medicinal Chemistry School of Chemistry and Chemical Engineering Southwest University Department of Chemistry Kakatiya University Indian Institute of Chemical Technology

A novel series of benzimidazole derived naphthalimide triazoles and some corresponding triazoliums have been successfully synthesized and characterized by 1H NMR, 13 C NMR, 1H-1H COSY, IR and HRMS spectra. All the new compounds were screened for their antimicrobial activities in vitro by two-fold serial dilution. 2-Chlorobenzyl triazolium 8g and compound 9b with octyl group exhibited the best antibacterial activities among all the tested compounds, especially against S. aureus with inhibitory concentration of 2 μg/mL which was equipotent potency to Norfloxacin(MIC=2 μg/mL) and more active than Chloromycin(MIC=7 μg/mL). Triazoliums 8g and 8f bearing 3-fluorobenzyl moiety displayed the best antifungal activities(MIC=2-19 μg/mL) against all the tested fungal strains without being toxic to PC12 cell line within concentration of 128 μg/m L. Further investigations by fluorescence and UV-Vis spectroscopic methods revealed that the compound 8g could effectively intercalate into calf thymus DNA to form the 8g-DNA complex which could block DNA replication, exerting powerful antimicrobial activities.

关键词： naphthalimide benzimidazole triazole antibacterial antifungal calf thymus DNA

Coumarin-derived azolyl ethanols:synthesis,antimicrobial evaluation and preliminary action mechanism

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Science China Chemistry 2016年第7期59卷 878-894页

作者： Xin-Mei Peng kannekanti vijaya kumar Guri L.V. Damu Cheng-He Zhou Institute of Bioorganic & Medicinal Chemistry Key Laboratory of Applied chemistry of Chongqing MunicipalitySchool of Chemistry and Chemical EngineeringSouthwest UniversityChongqing 400715China

A series of coumarin-derived azolyl ethanols including imidazolyl,triazolyl,tetrazolyl,benzotriazolyl,thiol-imidazolyl and thiol-triazolyl ones were conveniently synthesized and characterized by IR,~1H NMR,^(13)C NMR and high-resolution mass spectra(HRMS) *** of the prepared compounds showed appropriate logP_(ow) values and effective antibacterial and antifungal ***,compound 14 with bis-triazolyl ethanol group exhibited low minimal inhibitory concentration(MIC)value of 8 μg/mL against MRSA,which was comparable or even superior to reference drugs Norfloxacin(MIC=8μg/mL)and Chloramphenicol(MIC=16μg/mL).It could also effectively inhibit the growth of the tested fungal strains compared to *** binding studies of coumarin 14 with calf thymus DNA were investigated by UV-Vis absorption and fluorescence *** was found that compound 14 could interact with calf thymus DNA by groove binding to form14-DNA complex via both hydrogen bonds and van der Waals force,which might be the factor to exert the powerful antimicrobial activity.

关键词： coumarin imidazole triazole tetrazole antibacterial antifungal calf thymus DNA

Influence of Thermophoresis and Brownian Motion of Nanoparticles on Radiative Chemically-Reacting MHD Hiemenz Flow over a Nonlinear Stretching Sheet with Heat Generation

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Fluid Dynamics & Materials Processing 2023年第4期19卷 855-868页

作者： S.Mohammed Ibrahim P.vijaya kumar G.Lorenzini Department of Engineering Mathematics College of EngineeringKoneru Lakshmaiah Education FoundationVaddeswaramAndhra Pradesh522302India Department of Mathematics GITAM(Deemed to be University)VisakhapatnamAndhra Pradesh530045India Department of Industrial Engineering University of Parma-Parco Area Delle ScienzeParma43124Italy

In this study,a radiative MHD stagnation point flow over a nonlinear stretching sheet incorporating thermophoresis and Brownian motion is *** a similarity method to reshape the underlying Partial differential equations into a set of ordinary differential equations(ODEs),the implications of heat generation,and chemical reaction on the flow field are described in *** a Homotopy analysis method(HAM)is used to interpret the related *** is found that an increase in the magnetic and velocity exponent parameters can damp the fluid velocity,while thermophoresis and Brownian motion promote specific thermal *** results also demonstrate that as the Brownian motion parameter is increased,the concentration values become smaller.

关键词： Hiemenz flow MHD thermal radiation nonlinear stretching chemical reaction HAM

Layered Potassium Titanium Niobate/Reduced Graphene Oxide Nanocomposite as a Potassium‑Ion Battery Anode

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Nano-Micro Letters 2024年第1期16卷 1-16页

作者： Charlie A.F.Nason Ajay Piriya vijaya kumar Saroja Yi Lu Runzhe Wei Yupei Han Yang Xu Department of Chemistry University College London20 Gordon StreetLondon WC1H 0AJUK

With graphite currently leading as the most viable anode for potassium-ion batteries(kIBs),other materials have been left relatively *** metal oxides are among these,with many positive attributes such as synthetic maturity,longterm cycling stability and fast redox ***,to address this research deficiency we report herein a layered potassium titanium niobate kTiNbO5(kTNO)and its rGO nanocomposite(kTNO/rGO)synthesised via solvothermal methods as a high-performance anode for *** effective distribution across the electrically conductive rGO,the electrochemical performance of the kTNO nanoparticles was *** potassium storage performance of the kTNO/rGO was demonstrated by its first charge capacity of 128.1 mAh g^(−1) and reversible capacity of 97.5 mAh g^(−1) after 500 cycles at 20 mA g^(−1),retaining 76.1%of the initial capacity,with an exceptional rate performance of 54.2 mAh g^(−1)at 1 A g^(−1).Furthermore,to investigate the attributes of kTNO in-situ XRD was performed,indicating a low-strain ***-situ X-ray photoelectron spectra further investigated the mechanism of charge storage,with the titanium showing greater redox reversibility than the *** work suggests this lowstrain nature is a highly advantageous property and well worth regarding kTNO as a promising anode for future high-performance kIBs.

关键词： Potassium-ion batteries Intercalation Transition metal oxides Anodes Nanocomposite

Effect of exhaust gas recirculation and ethyl hexyl nitrate additive on biodiesel fuelled diesel engine for the reduction of NOx emissions

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Frontiers in Energy 2012年第3期6卷 304-310页

作者： k. VENkATESWARLU B. S. R. MURTHY V. V. SUBBARAO k. vijaya kumar Mechanical Engineering Department K.L University Guntur 522502India Mechanical Engineering Department Q.I.S College of Engineering and Technology Ongole 523272 India Mechanical Engineering Department J.N.T.U Kakinada Kakinada533033 India

Cetane improvers reduce the ignition delay, which in turn reduces the combustion temperatures thereby reduce NOx emissions. Exhaust gas recirculation （EGR） proved to be an effective way to reduce the NOx emissions. In this present experimental work, a combination of exhaust gas recirculation and cetane improver ethyl hexyl nitrate （EHN） is used to investigate the performance and exhaust emissions of a single cylinder four stroke naturally aspirated direct injection and air cooled diesel engine. Test results show that the brake thermal efficiency increases with the increase in the percentage of EGR which is accompanied by a reduction in brake specific fuel consumption and exhaust gas temperatures, and that bio- diesel with cetane improver under 20% EGR reduces NOx emissions by 33% when compared to baseline fuel without EGR. However carbon monoxide （CO）, hydro carbon （HC） and smoke emissions increase with an increase in percentage of EGR.

关键词： additive exhaust gas recirculation (EGR),emissions ethyl hexyl nitrate (EHN) performance