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Effect of Post Heat Treatment on Corrosion Resistance of Phytic Acid Conversion Coated Magnesium

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Journal of Materials Science & Technology 2013年第2期29卷 180-186页

作者： R.k. gupta k. Mensah-Darkwa D. kumar Engineering Research Center for Revolutionizing Metallic Biomaterials (ERC-RMB) Department of Mechanical Engineering North Carolina A&T State University 1601 East Market Street Greensboro NC 27411 USA

An environment friendly chemical conversion coating for magnesium was obtained by using a phytic acid solution. The effect of post-coating 1heat treatment on the microstructures and corrosion properties of phytic acid conversion coated magnesium was investigated. It was observed that the microstructure and corrosion resistive properties were improved for the heat treated samples. The corrosion current density for bare magnesium, phytic acid conversion coated magnesium, and post-coating heat treated magnesium was calculated to be 2.48 ×10^-5, 1.18×10^-6, and 9.27 × 10^7 A/cm^2, respectively. The lowest corrosion current density for the heat treated sample indicated its highest corrosion resistive effect for the magnesium. The maximum corrosion protective nature of the heat treated sample was further confirmed by the largest value of impedance in electrochemical impedance spectroscopy studies.

关键词： Magnesium Phytic acid Corrosion Impedance spectroscopy Scanning electron microscopy

Corrosion Protective Conversion Coatings on Magnesium Disks Using a Hydrothermal Technique

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Journal of Materials Science & Technology 2014年第1期30卷 47-53页

作者： R.k.gupta k.Mensah-Darkwa D.kumar Department of Chemistry Pittsburg State University Engineering Research Center for Revolutionizing Metallic Biomaterials(ERC-RMB) Department of Mechanical EngineeringNorth Carolina A&T State University

A uniform, compact, and well adherent conversion coating of magnesium hydroxide has been formed on bioresorbable magnesium disks by means of a hydrothermal technique. Electrochemical results indicate that the coating brings about a significant reduction in magnesium corrosion in phosphate buffered saline （PBS） solution. It is also observed that corrosion resistance of the coating increases with an increase in treatment time, which in turn, increases the coating thickness. The protective behavior of magnesium hydroxide coating is attributed to its chemical inertness in PBS solution. The coatings are found to be free from pores that reduce the direct contact between corroding media and underlying magnesium.

关键词： Magnesium Polarization Electrochemical impedance spectroscopy (EIS) Scanning electron microscopy (SEM) Conversioncoating Corrosion

Skew t distribution and its moments

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Progress in Natural Science:Materials International 2006年第10期16卷 1033-1037页

作者： Saralees NADARAJAH Arjun k.gupta Department of Statistics University of NebraskaLincolnNE 68583USA Department of Mathematics and Statistics Bowling Green State UniversityBowling GreenOH 43403USA

A random variable X is said to have the skew-t distribution if its pdf is f(x) = 2g(x) G(λx ), where g(·) and G (·), respectively, denote the pdf and the cdf of the Student' s t distribution with degrees of freedom v. The moments of this distribution appear not to have been studied in detail. In this paper, we derive general expressions for the nth moment of X by considering the cases v odd and v even separately. These expressions turn out to involve sums of the Gauss hypergeometric function. We also provide closed form expressions for the moments of X for the particular cases v = 2,66666, 10.

关键词： complete elliptical integral of the first kind complete elliptical integral of the second kind Gauss hypergeometric function moments skew t distribution.

Generalized Multiobjective Symmetric Duality under Second-Order(F, α, ρ, d)-Convexity

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Acta Mathematicae Applicatae Sinica 2015年第2期31卷 529-542页

作者： S.k.gupta D.Dangar Department of Mathematics Indian Institute of Technology Roorkee Department of Mathematics and Humanities IT Nirma University

In this paper, we first formulate a second-order multiobjective symmetric primal-dual pair over arbitrary cones by introducing two different functions f ： R^n × R^m → Rk and g ： R^n × R^m → R^l in each k-objectives as well as l-constraints. Further, appropriate duality relations are established under second-order（F, α, ρ, d）-convexity assumptions. A nontrivial example which is second-order（F, α, ρ, d）-convex but not secondorder convex/F-convex is also illustrated. Moreover, a second-order minimax mixed integer dual programs is formulated and a duality theorem is established using second-order（F, α, ρ, d）-convexity assumptions. A self duality theorem is also obtained by assuming the functions involved to be skew-symmetric.

关键词： multiobjective symmetric duality second-order(F α ρ d)-convex duality theorems minimax self duality

Soft tissue compartment bleed-the iceberg phenomenon:a case report

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Emergency and Critical Care Medicine 2023年第1期3卷 32-35页

作者： ramesh Vaidyanathan Parvez Mohi Ud Din Dar Dinesh Bagaria Amit gupta Division of Trauma Surgery and Critical Care Jai Prakash Narayan Apex Trauma CenterAll India Institute of Medical SciencesNew DelhiIndia Department of Trauma and Emergency Medicine All India Institute of Medical SciencesVijaypurJammuJammu and KashmirIndia

Introduction:Hemorrhage control is the essence of trauma *** teaching is 1 on the floor(ie,external bleeding)and 4 more(thoracic cavity,abdomen,retroperitoneum,and long bones).In this case report,we present a unique case with concealed bleeding into the soft tissue compartment leading to *** case triggered to consider the soft tissue compartment as the sixth potential bleeding site in trauma patients in hemorrhagic *** presentation:We present the case with concealed bleeding into the soft tissue compartment posing a challenge in *** presentation,he had a pulse rate of 117 beats/min,a blood pressure of 90/60mmHg,and a Glasgow Coma Scale(GCS)score of *** resuscitation,the patient's blood pressure dropped to 70/46 mmHg with a GCS of 7 of *** was then intubated and ***-enhanced computed tomography of the torso revealed a right scapular fracture with a large soft tissue hematoma along the right side of the neck and chest wall,extending up to the right lumbar ***:We suggest that the soft tissue compartment is the sixth potential site of internal bleeding in trauma patients,which should not be overlooked after having ruled out the other 5 sites.

关键词： Case report Hemorrhage Shock Soft tissue injury Trauma

Comparative study of travelling-wave and numerical solutions for the coupled short pulse (CSP) equation

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Chinese Physics B 2013年第5期22卷 60-66页

作者： Vikas kumar R. k. gupta Ram Jiwari School of Mathematics and Computer Applications Thapar University

The Lie symmetry analysis is performed for the coupled short plus （CSP） equation. We derive the infinitesimals that admit the classical symmetry group. Five types arise depending on the nature of the Lie symmetry generator. In all types, we find reductions in terms of system of ordinary differential equations, and exact solutions of the CSP equation are derived, which are compared with numerical solutions using the classical fourth-order Runge-kutta scheme.

关键词： coupled short pulse (CSP) equation Lie symmetric analysis Runge-kutta scheme exact solutions

Painlev Analysis,Lie Symmetries and Exact Solutions for Variable Coefficients Benjamin-Bona-Mahony-Burger (BBMB) Equation

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Communications in Theoretical Physics 2013年第8期60卷 175-182页

作者： Vikas kumar R.k.gupta Ram Jiwari School of Mathematics and Computer Applications Thapar UniversityPatiala147004PunjabIndia

In this paper, a variable-coefficient Benjarnin-Bona-Mahony-Burger （BBMB） equation arising as a math- ematical model of propagation of small-amplitude long waves in nonlinear dispersive media is investigated. The inte- grability of such an equation is studied with Painlevd analysis. The Lie symmetry method is performed for the BBMB equation and then similarity reductions and exact solutions are obtained based on the optimal system method. Further- more different types of solitary, periodic and kink waves can be seen with the change of variable coefficients.

关键词： BBMB equation Painleve analysis Lie symmetric analysis exact solutions

Trend in Observed and Projected Maximum and Minimum Temperature over N-W Himalayan Basin

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Journal of Mountain Science 2015年第2期12卷 417-433页

作者： Dharmaveer SINGH Sanjay k JAIN Rajan Dev gupta GIS Cell Motilal Nehru National Institute of Technology Allahabad Water Resources Systems Division National Institute of Hydrology Department of Civil Engineering Motilal Nehru National Institute of Technology Allahabad

Recently, study in past trends of climate variables gained significant consideration because of its contribution in adaptions and mitigation strategies for potential future changes in climate, primarily in the area of water resource management. Future interannual and inter-seasonal variations in maximum and minimum temperature may bring significant changes in hydrological systems and affect regional water resources. The present study has been performed to observe past(1970-2010) as well as future(2011-2100)spatial and temporal variability in temperature(maximum and minimum) over selected stations of Sutlej basin located in North-Western Himalayan region in India. The generation of future time series of temperature data at different stations is done using statistical downscaling technique. The nonparametric test methods, modified Mann-kendall test and Cumulative Sum chart are used for detecting monotonic trend and sequential shift in time series of maximum and minimum temperature. Sen's slope estimator test is used to detect the magnitude of change over a period of time on annual and seasonal basis. The cooling experienced in annual TMax and TMin at kasol in past(1970-2010) would be replaced by warming in future as increasing trends are detected in TMax during 2020 s and 2050 s and in TMin during 2020 s, 2050 s and 2080 s under A1 B and A2 scenarios. Similar results of warming are also predicted at Sunnifor annual TMin in future under both scenarios which witnessed cooling during 1970-2010. The rise in TMin at Rampur is predicted to be continued in future as increasing trends are obtained under both the scenarios. Seasonal trend analysis reveals large variability in trends of TMax and TMin over these stations for the future periods.

关键词： Statistical downscaling model Canadian Coupled Global Climate Model Temperature Mannkendall test Sen’s slope estimator

Propagation of P-and S-waves in initially stressed gravitating half space

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Applied Mathematics and Mechanics(English Edition) 2013年第7期34卷 847-860页

作者： S. gupta S. k. VISHWAkARMA Department of Applied Mathematics Indian School of Mines

The present paper contributes in studying the phase velocities of P- and S-waves in a half space subjected to a compressive initial stress and gravity field. The density and acceleration due to gravity vary quadratically along the depth. The dispersion equation is derived in a closed form. It is shown that the phase velocities depend not only on the initial stress, gravity, and direction of propagation but also on the inhomogeneity parameter associated with the density and acceleration due to gravity. Various particular cases are obtained, and the results match with the classical results. Numerical investigations on the phase velocities of P- and S-waves against the wave number are made for various sets of values of the material parameters, and the results are illustrated graphically. The graphical user interface model is developed to generalize the effect.

关键词： P-wave S-wave initial stress gravity half space graphical user interface