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Shock wave mitigation using zig-zag structures and cylindrical obstructions

Defence Technology（防务技术） 2021年第6期17卷 1840-1851页

作者： Arun kumar r Vaibhav Pathak Department of Mechanical Engineering Indian Institute of Technology Jodhpur(IITJ)JodhpurRajasthan342037India

The present study focuses on the mitigation of shock wave using novel geometric passages in the flow *** strategy is to produce multiple shock reflections and diffractions in the passage with minimum flow obstruction,which in turn is expected to reduce the shock wave strength at the target *** the present study the interaction of a plane shock front(generated from a shock tube)with various geometric designs such as,1)zig-zag geometric passage,2)staggered cylindrical obstructions and 3)zigzag passage with cylindrical obstructions have been investigated using computational *** is seen from the numerical simulation that,among the various designs,the maximum shock attenuation is produced by the zig-zag passage with cylindrical obstructions which is then followed by zig-zag passage and staggered cylindrical obstructions.A comprehensive investigation on the shock wave reflection and diffraction phenomena happening in the proposed complex passages have also been carried *** the new zig-zag design,the initial shock wave undergoes shock wave reflection and diffraction process which swaps alternatively as the shock front moves from one turn to the other *** cyclic shock reflection and diffraction process helps in diffusing the shock wave energy with practically no obstruction to the flow *** is found that by combining the shock attenuation ability of zig-zag passage(using shock reflection and diffraction)with the shock attenuation ability of cylindrical blocks(by flow obstruction),a drastic attenuation in shock strength can be achieved with moderate level of flow blocking.

关键词： Blast wave mitigation Blockage ratio Geometric obstructions Shock wave reflection and diffraction Zig-zag structure

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Optimal treatment of stratified Carreau and Casson nanofluids flows in Darcy-Forchheimer porous space over porous matrix

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Applied Mathematics and Mechanics(English Edition) 2020年第11期41卷 1651-1670页

作者： r.kumar r.kumar S.A.SHEHZAD A.J.CHAMKHA Department of Mathematics Central University of Himachal PradeshDharamshala 273001India Department of Mathematics COMSATS University IslamabadSahiwal 57000Pakistan Institute of research and Development Duy Tan UniversityDa Nang 550000Vietnam Institute of Theoretical and Applied research(ITAr) Duy Tan UniversityHanoi 100000Vietnam

A comparative three-dimensional(3D)analysis for Casson-nanofluid and Carreau-nanofluid flows due to a flat body in a magnetohydrodynamic(MHD)stratified environment is *** is estimated to be suspended in a Darcy-Forchheimer *** and Dufour responses are also accommodated in the flow field.A moving(rotating)coordinate system is exercised to examine the bidirectionally stretched flow fields(flow,heat transfer,and mass transfer).Nanofluid is compounded by taking ethylene glycol/sodium alginate as base fluid and ferric-oxide(Fe3O4)as *** equations are handled by the application of optimal homotopy asymptotic method(OHAM),where convergence parameters are optimized through the classical least square *** novel mechanism(hidden physics)due to appearing parameters is explored with the assistance of tabular and graphical *** reveal the double behavior state for temperature field with thermal stratification/Dufour number,and for concentration field with Soret number due to the presence of turning points.

关键词： thermal-solutal stratification Soret-Dufour effect Casson-Carreau nanofluid model porous matrix

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Poverty alleviation and resource conservation through development of cost effective technology at foot hill of Shivalik - A case study

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International Journal of Agricultural and Biological Engineering 2013年第3期6卷 34-40页

作者： r kumar P K Singh B A Langoo Division of Agricultural Engineering Sher-e-Kashmir Univeristy of Agricultural Sciences and Techonology of KashmirSrinagar(J&K)India Department of soil and water Engineering College of Technology and EngineeringUdaipur(Raj)India

The study revealed the development of cost effective technology utilized as a practical tool for treatment of seasonal torrent and addressing erosion problems and land use *** was implemented in a small agricultural watershed located in foot hill of Shivalik,India,to assess its prediction capacity of runoff,peak runoff flow and sediment *** effective technology was evaluated at the event scale by using a database of hydrological,geomorphologic and land use data collected during a two-year *** the catchment,the gullies which are small to medium in size were treated with gully plugging by erecting loose boulder check dams and erected with different species of *** types of spur were constructed with vegetative reinforcement for channelization of stream *** sediments deposited in the first year at downstream was recorded 0.09-81.0 tons,while in the second year it was reduced up to 0.07-16.7 ***,up stream sediment deposition was recorded 1.0-72.0 tons and 0.37-13.1 tons in two consecutive *** D-50 analysis of sediment deposited was carried in three different places of torrent and it was found that deposited particle size material decreased after treatment undertaken in the torrent ***,the mechanical as well as vegetative measures helped in the channelization of water course towards the central line with the tune of 10-100 m,stabilization of torrent bed and reclamation of degraded land.

关键词： Integrated watershed management mechanical measures D-50 vegetative measures

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Influence of Spark Plasma Sintering Temperature on the Densification, Microstructure and Mechanical Properties of Al-4.5 wt.%Cu Alloy

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Acta Metallurgica Sinica(English Letters) 2013年第6期26卷 761-771页

作者： S.Devaraj S.Sankaran r.kumar Department of Metallurgical and Materials Engineering Indian Institute of Technology Madras (IIT Madras)

The effect of sintering temperature on the densification mechanisms, microstructural evolution and mechanical properties of spark plasma sintered （SPS） compacts of a gas atomized Al-4.5 wt.%Cu alloy was investigated. The powder particles whose size varied between 10 to 500μm was subjected to SPS at 400, 450 and 500℃ at a pressure of 30 MPa. The compact sintered at 500℃ exhibited fully dense microstructure which was characterized by a uniform distribution of the secondary phase, free of dendrites and micro-porosity. Microscopy and the SPS data reveal that the events such as particle rearrangement, localized deformation and bulk deformation appear to be the sequence of sintering mechanisms depending on the size range of powder particles used for consolidation. The compact sintered at 500℃ exhibited the highest hardness and compression strength since the microstructure was characterized by fine distribution of precipitates, large fraction of submicron grains and complete metallurgical bonding.

关键词： Spark plasma sintering Sintering mechanisms Precipitation Compression strength

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Deep Neural Network Driven Automated Underwater Object Detection

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Computers, Materials & Continua 2022年第3期70卷 5251-5267页

作者： Ajisha Mathias Samiappan Dhanalakshmi r.kumar r.Narayanamoorthi Department of Electronics and Communication Engineering SRMInstitute of Science and TechnologyKattankulathurChennai603203India Department of Electrical and Electronics Engineering SRMInstitute of Science and TechnologyKattankulathurChennai603203India

Object recognition and computer vision techniques for automated object identification are attracting marine biologist’s interest as a quicker and easier tool for estimating the fish abundance in marine ***,the biggest problem posed by unrestricted aquatic imaging is low luminance,turbidity,background ambiguity,and context camouflage,which make traditional approaches rely on their efficiency due to inaccurate detection or elevated false-positive *** address these challenges,we suggest a systemic approach to merge visual features and Gaussian mixture models with You Only Look Once(YOLOv3)deep network,a coherent strategy for recognizing fish in challenging underwater *** an image restoration phase,pre-processing based on diffraction correction is primarily applied to *** YOLOv3 based object recognition system is used to identify fish *** objects in the background that are camouflaged are often overlooked by the YOLOv3 model.A proposed Bi-dimensional Empirical Mode Decomposition(BEMD)algorithm,adapted by Gaussian mixture models,and integrating the results of YOLOv3 improves detection efficiency of the proposed automated underwater object detection *** proposed approach was tested on four challenging video datasets,the Life Cross Language Evaluation Forum(CLEF)benchmark from the F4K data repository,the University of Western Australia(UWA)dataset,the bubble vision dataset and theDeepFish *** accuracy for fish identification is 98.5 percent,96.77 percent,97.99 percent and 95.3 percent respectively for the various datasets which demonstrate the feasibility of our proposed automated underwater object detection method.

关键词： Underwater images diffraction correction marine object recognition gaussian mixture model image restoration YOLO

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An Interacting Gauge Field Theoretic Model for Hodge Theory: Basic Canonical Brackets

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Communications in Theoretical Physics 2014年第6期61卷 715-728页

作者： r.kumar S.Gupta r.P.Malik Department of Physics Centre of Advanced Studies Banaras Hindu University DST Centre for Interdisciplinary Mathematical Sciences Faculty of Science Banaras Hindu University

We derive the basic canonical brackets amongst the creation and annihilation operators for a two(1 + 1)-dimensional(2D) gauge field theoretic model of an interacting Hodge theory where a U(1) gauge field(Aμ) is coupled with the fermionic Dirac fields(ψ andˉψ). In this derivation, we exploit the spin-statistics theorem, normal ordering and the strength of the underlying six infinitesimal continuous symmetries(and the concept of their generators) that are present in the theory. We do not use the definition of the canonical conjugate momenta(corresponding to the basic fields of the theory) anywhere in our whole discussion. Thus, we conjecture that our present approach provides an alternative to the canonical method of quantization for a class of gauge field theories that are physical examples of Hodge theory where the continuous symmetries(and corresponding generators) provide the physical realizations of the de rham cohomological operators of differential geometry at the algebraic level.

关键词： continuous symmetries 2D QED with fermionic Dirac fields symmetry principles basic canoni-cal (anti)commutators creation and annihilation operators conserved charges as generators derham cohomological operators Hodge theory

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Magnetohydrodynamic flow and heat transfer of a hybrid nanofluid over a rotating disk by considering Arrhenius energy

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Communications in Theoretical Physics 2021年第4期73卷 9-20页

作者： M Gnaneswara reddy Naveen kumar r B C Prasannakumara N G rudraswamy K Ganesh kumar Department of Mathematics Acharya Nagarjuna University CampusOngole-523001India Department of Studies and research in Mathematics Davangere UniversityShivagangothriDavangere-577007KarnatakaIndia Department of Mathematics P.C.Jabin Science CollageHubballi-580031India

This research work explores the effect of hybrid nanoparticles on the flow over a rotating disk by using an activation energy ***,we considered molybdenum disulfide and ferro sulfate as nanoparticles suspended in base fluid *** magnetic field is pragmatic normal to the hybrid nanofluid flow *** derived nonlinear ordinary differential equations are non-dimensionalized and worked out numerically with the help of Maple software by the rKF-45 *** scientific results for a non-dimensionalized equation are presented for both nanoparticle and hybrid nanoparticle *** of various predominant restrictions on flow and thermal fields are *** estimation for friction factor,local Nusselt number and Sherwood number are also *** reveal that the reduction of the heat transfer rate is greater in hybrid nanoparticles when compared to nanoparticles for increasing values of Eckert Number and the thermal field enhances for the enhanced values of volume fraction.

关键词： porous medium MHD hybrid nanoparticles activation energy

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Multi objective prediction and optimization of control parameters in the milling of aluminium hybrid metal matrix composites using ANN and Taguchi-grey relational analysis

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Defence Technology（防务技术） 2019年第4期15卷 545-556页

作者： S.Ajith Arul Daniel r.Pugazhenthi r.kumar S.Vijayananth Department of Mechanical Engineering Vels Institute of ScienceTechnology and Advanced Studies

This study aims to optimize the input parameters such as mass fraction and particle size of SiC along with depth of cut,feed and cutting speed in the milling of Al5059/SiC/*** hybrid metal matrix composites are generally fabricated by reinforcing of different sizes(10,20,40 μm)of SiC with aluminium at a different levels(5%,10%& 15%)whereas the MoS2 addition is fixed as 2%.The effect of each control factor on response variables are analyzed through Taguchi S/N ratio ***,the most significant method for prediction of response parameters is satisfied by ANN model than the regression *** of variance(ANOVA)results envisage that mass fraction of SiC,feed rate is the most domineering factor on response variable.

关键词： Silicon carbide Temperature Surface roughness Cutting forces Artificial neural network Grey relational analysis

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Natural Convection of Fe_3O_4-Ethylene Glycol Nanofluid under the Impact of Electric Field in a Porous Enclosure

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Communications in Theoretical Physics 2018年第6期69卷 667-675页

作者： M.Sheikholeslami S.A.Shehzad r.kumar Department of Mechanical Engineering Babol Noshirvani University of Technology Department of Mathematics COMSATS Institute of Information Technology Department of Mathematics Central University of Himachal Pardesh

Free convection of FeaO4-Ethylene glycol nanofluid in existence of Coulomb forces is studied. Effect of thermal radiation is taken into account. Properties of nanofluid are varied with supplied voltage and shape of nanoparticles. The bottom wall is considered as positive electrode. Control Volume based Finite Element Method is used to obtain the results, which are the roles of Darcy number （Da）, radiation parameter （rd）, rayleigh number （ra）, nanofluid volume fraction （qS）, and supplied voltage （△φ）. results indicate that Nusselt number is an enhancing function of supplied voltage and Darcy number. Maximum values for temperature gradient are occurred for platelet shape nanoparticles.

关键词： electric field thermal radiation nanofluid shape of nanoparticles porous media

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Experimental investigation of Tie6Ale4V titanium alloy and 304L stainless steel friction welded with copper interlayer

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Defence Technology（防务技术） 2015年第1期11卷 65-75页

作者： r.kumar M.BALASUBrAMANIAN Mechanical Engineering SKP Institute of Technology rMK College of Engineering and Technology

The basic principle of friction welding is intermetallic bonding at the stage of super plasticity attained with self-generating heat due to friction and finishing at upset pressure. Now the dissimilar metal joints are especially popular in defense, aerospace, automobile, bio-medical,refinery and nuclear engineerings. In friction welding, some special alloys with dual phase are not joined successfully due to poor bonding strength. The alloy surfaces after bonding also have metallurgical changes in the line of interfacing. The reported research work in this area is scanty. Although the sound weld zone of direct bonding between Tie6Ale4 V and SS304 L was obtained though many trials, the joint was not successful. In this paper, the friction welding characteristics between Tie6Ale4 V and SS304 L into which pure oxygen free copper(OFC) was introduced as interlayer were investigated. Boxe Behnken design was used to minimize the number of experiments to be performed. The weld joint was analyzed for its mechanical strength. The highest tensile strength between Tie6Ale4 V and SS304 L between which pure copper was used as insert metal was acquired. Micro-structural analysis and elemental analysis were carried out by EDS, and the formation of intermetallic compound at the interface was identified by XrD analysis.

关键词： Friction welding Tie6Ale4V SS304L Oxygen free copper Interlayer Microstructure Interface

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