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High-Velocity Projectile Impact Behaviour of Friction Stir Welded AA7075 Thick Plates

Defence Technology（防务技术） 2023年第11期29卷 153-163页

作者： r.praveen S.r.Koteswara rao G.Selvakumar r.Damodaram Department of robotics and Automation Karpaga Vinayaga College of Engineering and TechnologyChengalpattu603308TamilNaduIndia Department of Mechanical Engineering Sri Sivasubramaniya Nadar College of EngineeringChennai603110TamilNaduIndia

In this study, high velocity impact behaviour of friction stir welded AA7075-T651 25 mm thick plates were investigated using a 7.62 mm × 51 mm lead core and 7.62 mm × 39 mm steel core projectiles. Prior to ballistic trails, mechanical and metallurgical properties of friction stir welded AA 7075-T651 25 mm thick plates were studied. Microstructural and hardness studies revealed that friction stir welds constituted three distinct regions namely Weld Nugget(WN), Thermo-Mechanically Affected Zone(TMAZ) and Heat Affected Zone(HAZ). Base Material(BM) and all three weld regions were ballistically tested as per military standard NIJ.0108.01 using lead and steel core bullets at maximum permissible velocities of 830 ± 20 and 700 ± 30 m/s, respectively. It has been found that base material(AA7075-T651)and all three weld regions of 25 mm thick plates were able to resist perforation by both types of projectiles used. However depth of penetration has been found to increase from BM to WN, HAZ and TMAZ for both types of projectiles. In all cases steel core projectiles caused higher depth of penetration compared to those caused by lead core projectiles. TMAZs of the friction stir welds were found to be the weakest zone. The fracture that occurred in the base material was spall fragmentation indicating brittle failure, whereas all zones of friction stir welded AA7075-T651 targets with a front petalling, indicating ductile failure. The post-ballistic tested samples showed no significant change in the microstructure of the BM and WN. On the other hand, TMAZ and HAZ showed severe grain deformation in the direction of projectile penetration, and the formation of adiabatic shear bands(ASB). This work showed that 25 mm thick friction stir welded AA7075-T651 joints responded well to ballistic impact loads, making them a good choice for light combat vehicles.

关键词： Aluminum alloy Thick plate Friction stir welding Ballistic performance Depth of penetration

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Energy-and trust-aware secure routing algorithm for big data classification using Mapreduce framework in IoT networks

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International Journal of Modeling, Simulation, and Scientific Computing 2021年第2期12卷 80-103页

作者： S.Md.Mujeeb r.praveen Sam K.Madhavi Department of CSE Jawaharlal Nehru Technological University Anantapur(JNTUA)Ananthapuramu-515002 Andhra PradeshIndia Department of Computer Science and Engineering G.Pulla reddy Engineering College(Autonomous)Nandyal road Kurnool 518007Andhra PradeshIndia

Due to the open nature of wireless data transmission,routing and data security pose an important research challenge in the Internet of Things(IoT)-enabled ***,the characteristic features,like constrained resources,heterogeneity,uncontrolled environment,and scalability requirement,make the security issues even more ***,an effective and secure routing protocol named modified Energy Harvesting Trust-aware routing Algorithm(mod-EHTArA)is proposed to increase the energy efficiency and the lifespan of the *** proposed mod-EHTArA is designed by adopting the Link Lifetime(LLT)model with the traditional *** optimal secure routing path is effectively selected by the proposed mod-EHTArA using the cost metric,which considers the factors like delay,LLT,energy,and *** big data classification process is carried out at the Base Station(BS)using the Mapreduce ***,the big data classification is progressed using a stacked autoencoder,which is trained by the Adaptive E-Bat *** Adaptive E-Bat algorithm is developed by integrating the adaptive concept with the Bat Algorithm(BA)and Exponential Weighted Moving Average(EWMA).The proposed mod-EHTArA showed better performance by obtaining a maximal energy of 0.9855.

关键词： Stacked autoencoder big data classification Internet of Things secure routing energy harvesting

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Crimean-Congo hemorrhagic fever:Pathogenesis,transmission and public health challenges

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World Journal of Virology 2025年第1期14卷 63-72页

作者： Sita Kumari Karanam Kandra Nagvishnu praveen Kumar Uppala Sandhya Edhi Srinivasa rao Varri Department of Pharmaceutical Biotechnology Maharajah’s College of PharmacyVizianagaram 535002Andhra PradeshIndia Department of Pharmacology Santhiram Medical College and General HospitalNandyal 518501Andhra PradeshIndia Department of Pharmacology Santhiram Medical College and General HospitalNandyal 518501Andhra PradeshIndia Department of Pharmaceutical AnalysisMaharajah's College of PharmacyVizianagaram 535002Andhra PradeshIndia

The dangerous Crimean-Congo hemorrhagic fever virus(CCHFV),an encapsulated negative-sense rNA virus of the family Nairoviridae,is transmitted from person to person via *** a case fatality rate between 10%to 40%,the most common ways that the disease may spread to humans are via tick bites or coming into touch with infected animals'blood or ***,the transfer of bodily fluids between individuals is another potential route of *** is a wide range of symptoms experienced by patients throughout each stage,from myalgia and fever to extreme bruising and excess *** management measures include minimising the spread of ticks from one species to another and from people to animals via the use of protective clothing,repellents,and proper animal *** order to prevent the spread of illness,healthcare workers must adhere to stringent *** the lack of an authorised vaccine,the main components of treatment now consist of preventative measures and supportive care,which may include the antiviral medicine *** still don't know very much about the virus's mechanisms,even though advances in molecular virology and animal models have improved our understanding of the pathogenesis of CCHFV.A critical need for vaccination that is both safe and effective,as well as for quick diagnosis and efficient treatments to lessen the disease's impact in areas where it is most *** steps towards lowering Crimean-Congo hemorrhagic fever mortality and morbidity rates were to anticipatethe future availability of immunoglobulin products.

关键词： Crimean-congo haemorrhagic fever Tick-borne illness Immunoglobulins Viral hemorrhagic fever Antiviral therapy

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Pile foundation in alternate layered liquefiable and non-liquefiable soil deposits subjected to earthquake loading

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Earthquake Engineering and Engineering Vibration 2024年第2期23卷 359-376页

作者： praveen Huded M Suresh r Dash LEA Associates South East Asia Pvt.Ltd. New Delhi 110044India Indian Institute of Technology Bhubaneswar Khurda 752050India

Pile foundations are still the preferred foundation system for high-rise structures in earthquake-prone *** foundations have experienced failures in past earthquakes due to *** on pile foundations in liquefiable soils has primarily focused on the pile foundation behavior in two or three-layered soil ***,in natural occurrence,it may occur in alternative layers of liquefiable and non-liquefiable ***,the experimental and/or numerical studies on the layered effect on pile foundations have not been widely addressed in the *** of the design codes across the world do not explicitly mention the effect of sandwiched non-liquefiable soil layers on the pile *** the present study,the behavior of an end-bearing pile in layered liquefiable and non-liquefiable soil deposit is studied *** study found that the kinematic bending moment is higher and governs the design when the effect of the sandwiched non-liquefied layer is considered in the analysis as opposed to when its effect is ***,ignoring the effect of the sandwiched non-liquefied layer in a liquefiable soil deposit might be a nonconservative design approach.

关键词： pile foundation liquefaction alternately layered soil fixity effect layered effect

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Thermally insulating robust carbon composite foams with high EMI shielding from natural cotton

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Journal of Materials Science & Technology 2021年第35期94卷 113-122页

作者： A.Chithra praveen Wilson Sujith Vijayan r.rajeev K.Prabhakaran Department of Chemistry Indian Institute of Space Science and TechnologyThiruvananthapuram 695547India Analytical and Spectroscopy Division Vikram Sarabhai Space CentreThiruvananthapuram 695022India

Thermally insulating and fire-resistant carbon composite foams are prepared by consolidating natural cotton fibre dispersed in aqueous sucrose solution by filter-pressing followed by drying and *** compressive strength(5 kPa to 1.4 MPa)and thermal conductivity(0.069 to 0.185 W m^(-1)K^(-1))depend on the foam density(0.06 to 0.31 g cm^(-3))which is modulated by varying the sucrose solutions concentration(100 to 700 g L^(-1)).Partially flexible to the rigid transition of the carbon composite foams occurs at sucrose concentration above 200 g L^(-1).The tubular carbon fibre formed from cotton is welded at their contact points by the amorphous carbon produced from sucrose leading to partial flexibility at low sucrose concentration and advancement of fibre-to-fibre bonding area at higher sucrose concentration results in rigid *** porosity in the inter-fibre space and lumen of the carbonized cotton fibre contributes to the low thermal *** carbon composite foams prepared at a sucrose solution concentration of 500 g L^(-1) and above are amenable to machining using conventional machines and *** rigid carbon foams show EMI shielding effectiveness and specific shielding effectiveness in the ranges of 21.5 to 38.9 d B and 108-138 dB cm^(3) g^(-1),respectively.

关键词： Foams natural fibres thermal properties consolidation mechanical properties emi shielding properties

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Methane hydrates:A future clean energy resource

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Chinese Journal of Chemical Engineering 2019年第9期27卷 2026-2036页

作者： Zhenyuan Yin praveen Linga Department of Chemical and Biomolecular Engineering National University of Singapore117585Singapore Lloyd's register Singapore Pte.Ltd. 138522Singapore

Natural gas has been considered as the best transition fuel into the future carbon constraint *** ever-increasing demand for natural gas has prompted expanding research and development activities worldwide for exploring methane hydrates as a future energy *** its vast global resource volume(~3000 trillion cubic meter CH4)and high energy storage capacity(170 CH4 v/v methane hydrate),recovering energy from naturally-occurring methane hydrate has attracted both academic and industry interests to demonstrate the technical feasibility and economic *** this review paper,we highlight the recent advances in fundamental researches,seminal discoveries and implications from ongoing drilling programs and field production tests,the impending knowledge gaps and the future perspectives of recovering energy from methane *** further emphasize the current scientific,technological and economic challenges in realizing long-term commercial gas production from methane hydrate *** continuous growth of the corresponding experimental studies in China should target these specific challenges to narrow the knowledge gaps between laboratory-scale investigations and reservoir-scale ***,we briefly discuss both the environmental and geomechanical issues related to exploiting methane hydrate as the future energy resource and believe that they should be of paramount importance in the future development of novel gas production technologies.

关键词： Methane hydrates Energy recovery Gas production Energy resource recent advance Future outlook

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Optimal PV Array Configuration for Extracting Maximum Power Under Partial Shading Conditions by Mitigating Mismatching Power Losses

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CSEE Journal of Power and Energy Systems 2022年第2期8卷 499-510页

作者： praveen Kumar Bonthagorla Suresh Mikkili the Electrical and Electronics Engineering Department National Institute of Technology Goa403401India

The grid-connected or standalone PV central inverter architecture is comprised of several PV modules which are connected in different ways to form the PV *** power generation capability of the PV array is primarily affected by partial shading conditions(PSC).Due to PSCs,the power output of the PV array is dramatically reduced,and mismatching losses are induced in the PV *** on the extent of these problems,multiple peaks also appear in the power-voltage(P-V)curve,which makes it very difficult to track the global maximum power point(GMPP).The main objective of this research paper is to model and simulate the series(S),series-parallel(SP),bridge-link(BL),honey-comb(HC),total-cross-tied(TCT)and proposed triple-tied(TT)solar PV array configurations under various partial shading *** performance of all PV configurations is evaluated under a uniform approach,considering eight different shading *** performance of the considered PV configurations is analyzed in terms of their mismatching power losses,fill factors,efficiency,global maximum power points(GMPPs),local maximum power points(LMPPs),voltages and currents at GMPPs,open circuit voltage and short circuit *** above-mentioned PV configurations are modeled and simulated in a Matlab/Simulink environment by considering the KC-200GT module parameters.

关键词： Photo voltaic(PV) PV array configurations triple-tied(TT) maximum power point(MPP) partial shading mismatching power losses fill factor efficiency

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Performance Investigation of Hybrid and Conventional PV Array Configurations for Grid-connected/Standalone PV Systems

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CSEE Journal of Power and Energy Systems 2022年第3期8卷 682-695页

作者： praveen Kumar Bonthagorla Suresh Mikkili Department of Electrical and Electronics Engineering National Institute of TechnologyGoaIndia

Currently,the critical challenge in solar photovoltaic(PV)systems is to make them energy *** of the key factors that can reduce the PV system power output is partial shading conditions(PSCs).The reduction in power output not only depends on a shaded region but also depends on the pattern of shading and physical position of shaded modules in the *** to PSCs,mismatch losses are induced between the shaded modules which can cause several peaks in the output power-voltage(P-V)*** series-parallel(SP),total-cross-tied(TCT),bridge-link(BL),honey-comb(HC),and triple-tied(TT)configurations are considered as conventional configurations,which are severely affected by PSCs and generate more mismatch power losses along with a greater number of local *** reduce the effect of PSCs,hybrid PV array configurations,such as series-parallel:total-cross-tied(SP-TCT),bridge-link:total-cross-tied(BL-TCT),honey-comb:total-cross-tied(HC-TCT)and bridge-link:honey-comb(BL-HC)are *** paper briefly discusses the modeling,simulation and performance evaluation of hybrid and conventional 7×7 PV array configurations during different PSCs in a Matlab/Simulink *** performance of hybrid and conventional PV configurations are evaluated and compared in terms of global maximum power(GMP),voltage and currents at GMP,open and short circuit voltage and currents,mismatch power loss(MPL),fill factor,efficiency,and a number of local maximum power peaks(LMPPs).

关键词： Fill factor global maximum power(GMP) hybrid PV array configuration maximum power point(MPP) mismatch power loss(MPL) partial shading triple-tied(TT)

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Magnetic fabrics in characterization of magma emplacement and tectonic evolution of the Moyar Shear Zone,South India

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Geoscience Frontiers 2013年第1期4卷 113-122页

作者： P.Pratheesh V.Prasannakumar K.r.praveen Department of Geology University of KeralaKariavattom Campus.Thiruvananthapuram 695 581KeralaIndia

The Moyar Shear Zone （MSZ） of the South Indian granulite terrain hosts a prominent syenite pluton （-560 Ma） and associated NW-SE to NE-SW trending mafic dyke swarm （-65 Ma and 95 Ma）. Preliminary magnetic fabric studies in the mafic dykes, using Anisotropy of Magnetic Susceptibly （AMS） studies at low-field, indicate successive emplacement and variable magma flow direction. Magnetic lineation and foliation in these dykes are identical to the mesoscopic fabrics in MSZ mylonites, indicating shear zone guided emplacement. Spatial distribution of magnetic lineation in the dykes suggests a common conduit from which the source magma has been migrated. The magnetic foliation trajectories have a sigmoidal shape to the north of the pluton and curve into the MSZ suggesting dextral sense of shear. Identical fabric conditions for magnetic fabrics in the syenite pluton and measured field fabrics in mylonite indicate syntectonic emplacement along the Proterozoic crustal scale dextral shear zone with repeated reactivation history.

关键词： Magnetic fabrics Moyar Shear Zone Syenite pluton Mafic dykes Tectonic evolution

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Kinetic Energy Preserving and Entropy Stable Finite Volume Schemes for Compressible Euler and Navier-Stokes Equations

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Communications in Computational Physics 2013年第10期14卷 1252-1286页

作者： praveen Chandrashekar TIFr Center for Applicable Mathematics Bangalore 560065India

Centered numerical fluxes can be constructed for compressible Euler equations which preserve kinetic energy in the semi-discrete finite volume *** essential feature is that the momentum flux should be of the form ■ are any consistent approximations to the pressure and the mass *** scheme thus leaves most terms in the numerical flux unspecified and various authors have used simple *** we enforce approximate or exact entropy consistency which leads to a unique choice of all the terms in the numerical *** a consequence novel entropy conservative flux that also preserves kinetic energy for the semi-discrete finite volume scheme has been *** fluxes are centered and some dissipation has to be added if shocks are present or if the mesh is *** construct scalar artificial dissipation terms which are kinetic energy stable and satisfy approximate/exact entropy ***,we use entropy-variable based matrix dissipation flux which leads to kinetic energy and entropy stable *** schemes are shown to be free of entropy violating solutions unlike the original roe *** hypersonic flows a blended scheme is proposed which gives carbuncle free solutions for blunt body *** results for Euler and Navier-Stokes equations are presented to demonstrate the performance of the different schemes.

关键词： Euler equation Navier-Stokes equation finite volumemethod kinetic energy preservation entropy conservation

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