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Effect of sample size on the fluid flow through a single fractured granitoid

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Journal of Rock Mechanics and Geotechnical Engineering 2016年第3期8卷 329-340页

作者： Kunal kumar Singh devendra Narain Singh Ranjith Pathegama Gamage Geohazards and Engineering Geology Division Geological Survey of India Bandlaguda Hyderabad 500068 India Geotechnical Engineering Division Department of Civil Engineering Indian Institute of Technology Bombay Powai Mumbai 400076 India Department of Civil Engineering Monash University Clayton Melbourne Vic 3800 Australia

Most of deep geological engineered structures, such as rock caverns, nuclear waste disposal repositories, metro rail tunnels, multi-layer underground parking, are constructed within hard crystalline rocks because of their high quality and low matrix permeability. In such rocks, fluid flows mainly through fractures. Quantification of fractures along with the behavior of the fluid flow through them, at different scales, becomes quite important. Earlier studies have revealed the influence of sample size on the confining stress-permeability relationship and it has been demonstrated that permeability of the fractured rock mass decreases with an increase in sample size. However, most of the researchers have employed numerical simulations to model fluid flow through the fractureJfracture network, or laboratory investigations on intact rock samples with diameter ranging between 38 mm and 45 cm and the diameter-to-length ratio of 1：2 using different experimental methods. Also, the confining stress, 03, has been considered to be less than 30 MPa and the effect of fracture roughness has been ignored. In the present study, an extension of the previous studies on ＂laboratory simulation of flow through single fractured granite＂ was conducted, in which consistent fluid flow experiments were performed on cylindrical samples of granitoids of two different sizes （38 mm and 54 mm in diameters）, containing a ＂rough walled single fracture＂. These experiments were performed under varied confining pressure （03 - 5-40 MPa）, fluid pressure （fp ≤ 25 MPa）, and fracture roughness. The results indicate that a nonlinear relationship exists between the discharge, Q, and the effective confining pressure, σeff., and Q decreases with an increase in σeff.. Also, the effects of sample size and fracture roughness do not persist when O＇eff. ≥ 20 MPa. It is expected that such a study will be quite useful in correlating and extrapolating the laboratory scale investigations to in-situ scale and further imp

关键词： Rock massSingle fractureFluid flowSample sizeSize effectFracture roughness

Numerical modeling and optimization of process parameters in continuous extrusion process through response surface methodology, artificial neural network & genetic algorithm

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International Journal of Modeling, Simulation, and Scientific Computing 2021年第6期12卷 230-248页

作者： Tariku Desta devendra kumar Sinha Perumalla Janaki Ramulu Ram Sewak Singh Mechanical Design and Manufacturing Engineering Department School of Mechanical Chemical and Materials Engineering Adama Science and Technology UniversityAdamaEthiopia Department of Electronics Engineering School of Electrical Electronics and Computing Adama Science and Technology University Adama Ethiopia

The product of high complex profile,high strength,high productivity and excellent material properties with infinite length can be produced by Continuous Extrusion(CE)*** numerical simulation of Aluminum(AA 1100)feedstock material at different wheel velocities,product diameter,feedstock temperature,die temperature and friction condition has been carried out using 3D simulation tool Design Environment for Forming(DEFORM-3D)in this *** development of mathematical model is carried out to investigate the influence of wheel velocity,extrusion ratio,feedstock temperature,die temperature and friction conditions on total load required for the deformation and extrusion of feedstock material through Response Surface Methodology(RSM).The statistical significance of mathematical model is verified through analysis of variance(ANOVA).The most optimum value of extrusion load has been found to be 136.4 kN through iterative process of Genetic Algorithm(GA)using Artificial Neural Network(ANN).The optimized value of input process variables for minimum value of extrusion load obtained has been found to be 13 Revolutions per Minute(RPM)as wheel velocity,5 mm as product diameter,0.95 as friction condition,650◦C as feedstock temperature and 550◦C as die *** paper with proposed methodology will be helpful for industries working in the area of CE in terms of minimizing energy consumption during production process of bus bars,tubes,wires,cables,sheets,plates,strips,etc.

关键词： Continuous extrusion DEFORM-3D AA1100 response surface methodology artificial neural network genetic algorithm

Structural-Nanomechanical Property Correlation of Shallow Water Shrimp （Pandalus platyceros） Exoskeleton at Elevated Temperature

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Journal of Bionic Engineering 2014年第3期11卷 360-370页

作者： devendra Verma Vikas Tomar School of Aeronautics and Astronautics Purdue University West Lafayette IN 47907 USA

This investigation reports the nanomechanical properties of shallow water shrimp exoskeleton at temperatures ranging from 30 ℃ to 80 ℃ measured using nanoindentation experiments. Scanning Electron Microscopy （SEM） measurements suggest that the shrimp exoskeleton has the Bouligand structure in its layers, a key characteristic of the crustaceans. The thickness of the layers and packing density are found to be different from that of lobsters and crabs reported earlier in the literature. Mechanical properties at high temperatures are determined using micro materials nanoindentation test set up combined with the hot stage. The properties measured during nanoindentation test are corrected for the creep and thermal drift during the experiments. The reduced modulus values are found to be around 28 GPa at 30 ℃ that reduces to approximately 24 GPa at 80 ℃. The hardness values also decrease from 1.6 GPa at 30 ℃ to around 1.2 GPa at 80 ℃. The indentation size effect is found to be absent at all temperatures. Creep mechanisms of polymers like materials and its temperature dependence are discussed to give more insight into the deformation mechanism.

关键词： fresh water shrimp nanomechanics temperature dependence creep mechanism

On the Growth Properties of Solutions for a Generalized Bi-Axially Symmetric Schr?dinger Equation

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Journal of Mathematical Research with Applications 2017年第2期37卷 214-222页

作者： devendra kumar Payal BISHNOI Mohammed HARFAOUI Department of Mathematics Faculty of Sciences Al-Baha University Department of Mathematics M.M.H. College University Hassan II-Casablanca Laboratory of MathematicsCryptography and MechanicsF.S.T

In this paper, we have considered the generalized bi-axially symmetric Schr?dinger equation ?;φ/?x;+?;φ/?y;+（2ν/x）?φ/?x+（2μ/y）?φ/?y+ {K;- V（r）}φ = 0,where μ, ν≥ 0, and r V（r） is an entire function of r = +（x;+ y;）;corresponding to a scattering potential V（r）. Growth parameters of entire function solutions in terms of their expansion coefficients, which are analogous to the formulas for order and type occurring in classical function theory, have been obtained. Our results are applicable for the scattering of particles in quantum mechanics.

关键词： Schro?dinger equation scattering potential Jacobi polynomials order and type

Well-Defined Fluorinated Copolymers:Current Status and Future Perspectives

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Accounts of Materials Research 2021年第4期2卷 242-251页

作者： Subrata Dolui devendra kumar Sanjib Banerjee Bruno Ameduri Department of Chemistry Indian Institute of Technology BhilaiRaipur 492015ChhattisgarhIndia ICGM Universitéde MontpellierCNRSENSCMMontpellierFrance

Well-defined fluoropolymers exhibit unique properties such as excellent oil and water repellency,satisfactory thermal stability,a low refractive index,and low surface *** origin of these properties is attributed to the presence of a strong electronegative and low polarizable fluorine atom in the backbone of such polymers,which leads to a strong C−F bond(with a high bond dissociation energy of 485 kJ mol−1).Because of these features,these polymers have found applications as functional coatings,thermoplastics,biomedical items,separators,and binders for Li ion batteries,fuel cell membranes,piezoelectric devices,high-quality wires and cables,and so ***,fluoropolymers are synthesized by the conventional radical(co)polymerization of fluoroalkenes,which leads to the production of(co)polymers with an ill-defined end group,uncontrolled molar mass,and high dispersity *** the last two decades,significant developments of various reversible deactivation radical polymerization(RDRP)techniques have helped the design of macromolecular architectures(including block,graft,star,and dendrimers)on ***,for relevant new applications,well-defined fluoropolymers with controlled macromolecular architectures(e.g.,block copolymers as thermoplastic elastomers and electroactive polymers or graft copolymers for fuel cell membranes)are *** RDRP methods,developed in the last two decades,have paved the way for the synthesis of(co)polymers with well-defined molar mass,dispersity,chain end-functionality,and macromolecular *** of these RDRP techniques have been successfully employed for the synthesis of well-defined fluorinated *** techniques include iodine-transfer polymerization(ITP),reversible addition−fragmentation chain-transfer(RAFT)polymerization,organometallic-mediated radical polymerization(OMRP),and,to a lesser extent,nitroxide-mediated polymerization(NMP).Impressive control of the molar mass parameters of the fluoropo

关键词： polymerization molar reversible

Potentials and challenges of using co-design in health services research in low-and middle-income countries

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Global Health Research and Policy 2023年第1期8卷 514-521页

作者： devendra Raj Singh Rajeeb kumar Sah Bibha Simkhada Zoe Darwin School of Human and Health Sciences University of HuddersfieldHuddersfieldUK

Co-design with people having poor access to health services and fragile health systems in low-and middle-income countries can be momentous in bringing service users and other stakeholders together to improve the delivery and utilisation of health *** is ample of evidence from high-income countries regarding how co-design can translate available evidence into developing acceptable,feasible,and adaptable health solutions in different ***,there is limited literature on co-design in health research in the context of low-and middle-income ***,it is crucial to understand how knowledge about collaborative working can be translated into policy and practice in the context of low-and middle-income ***,this paper discusses the concept of co-design,co-production,and co-creation in health and the potentiality and challenges of using co-design in health services research in low-and middle-income *** the challenges,the co-design research has considerable potential to encourage the meaningful engagement of service users and other stakeholders in developing,implementing,and evaluating real-world solutions in low-and middle-income *** is essential to balance power dynamics in a co-design process through mutual recognition and respect,participant diversity,and reciprocity and flexibility in *** inclusive and collaborative approach to working is complex due to existing rigid hierarchical structures,socio-cultural beliefs,political interference and working ***,this could be minimised by developing transparent terms of reference that reflect the value and benefits of equal partnership in particular co-design work.

关键词： Co-design Potentials Challenges Health services research Low-middle-income countries

Currencies of greater interest for central Asian economies:an analysis of exchange market pressure amid global and regional interdependence

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Financial Innovation 2023年第1期9卷 1275-1292页

作者： devendra kumar Jain Naqeeb Ur‑Rehman Omonjon Ganiev Kapil Arora Flame School of Business Flame UniversityPuneIndia School of Economics Westminster International UniversityTashkentUzbekistan School of Business&Economics Westminster International University in TashkentTashkentUzbekistan Alliance School of Business Alliance UniversityBangaloreIndia

Central Asian Economies(CAEs)have diverse exchange rate *** have recorded higher volatility in the foreign exchange market since *** volatility of the transition era has drifted these economies towards partial *** authorities in CAEs,(already have a challenge of maintaining monetary policy autonomy)have a gigantic task of price stability and stopping the spread of *** study is directed towards assessing the drivers and the determinants of foreign exchange market pressure in *** results,based on panel data analysis and the System GMM model,have provided useful insights about the exchange market pressure determinants particularly USD,Euro,Ruble,and *** results show that China and Russia exchange market pressure has a negative effect on the exchange market pressure of *** the dollar index shows a positive impact on the exchange market pressure of ***,the findings imply that China and Russia currency appreciation results in a trade deficit across *** policy implication suggests that the floating exchange rate regime(inflation targeting regime)is not in favor of CAEs,and they must use managed-float to reduce their trade deficits.

关键词： Exchange market pressures Central Asian economies Exchange markets Financial market Interdependence Transition economies

Strength and elongation of spray formed Al–Si–Pb alloys

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International Journal of Minerals,Metallurgy and Materials 2014年第12期21卷 1222-1227页

作者： Aruna Tomar Rashmi Mittal devendra Singh Department of Metallurgical and Materials Engineering Indian Institute of Technology Roorkee

The strength and elongation to fracture of spray deposited Al-Si-Pb alloys were studied as a function of lead content, silicon content, and distance from the centre to periphery of the deposit. It is found that the ultimate tensile strength, proof stress and elongation to fracture decrease, linearly and exponentially, with the increase in lead content and porosity of the deposit, respectively. Both the strengths and elongation to fracture linearly increase with increasing distance from the centre to periphery of the deposit. The ultimate tensile strength and proof stress are higher at a higher silicon content and they have a linear relationship with the hardness of the deposit.

关键词： aluminum silicon alloys spray forming tensile strength proof stress elongation

Effects of stenoses on non-Newtonian flow of blood in blood vessels

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International Journal of Biomathematics 2015年第1期8卷 123-135页

作者： Om Prakash O. D. Makinde S. P. Singh Nidhi Jain devendra kumar School of Basic and Applied Sciences Galgotias University Greater Noida Uttar Pradesh India Faculty of Military Science Stellenbosch University Private Bag X2 Saldanha 7395 South Africa Department of Mathematics DEI Dayalbagh Agra Uttar Pradesh India Department of Mathematics Sachdeva Institute of Technology Farah Mathura Uttar Pradesh India

In this paper, a mathematical model for steady blood flow through blood vessels with uniform cross-section in stenoses arteries has been proposed. Blood is assumed to be non- Newtonian, incompressible and homogeneous fluid. Blood in human artery is represented as Bingham plastic fluid. Expressions for flow rate, wall shear stress, and resistance to flow against stenoses size have been obtained. Obtained results indicate that stenoses size decreases the flow rate and increases the wall shear stress as well as resistance to flow.

关键词： Stenoses wall shear stress resistance to flow flow rate non-Newtonian fluid