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Microstructure and mechanical properties of Al-Zr nanocomposite materials
Srinivasarao, B.,Suryanarayana, C.,Oh-ishi, K.,Hono, K. Elsevier Sequoia 2009 Materials science & engineering. properties, micro Vol.518 No.1
Three different processing routes were explored to develop Al-Zr nanocomposite alloys using mechanical alloying and spark plasma sintering methods. Depending on the route of milling adopted, the powder in the as-milled condition consisted of either a solid solution of Zr in Al or a mixture of Al-solid solution and Al<SUB>3</SUB>Zr (L1<SUB>2</SUB>) phases. The alloys after sintering consisted of Al and Al<SUB>3</SUB>Zr (L1<SUB>2</SUB>) with grain sizes of less than 100nm. These nanocomposite alloys exhibited a high compressive strength of 1GPa with 10% plasticity. The high strength observed in these alloys was explained on the basis of the retention of nanometer sized grains and also the fine dispersion of the L1<SUB>2</SUB> phase. On the other hand, the good amount of plasticity was explained to be due to excellent bonding between the powder particles and the presence of coarse Al grains in the matrix.
Stretchable graphene and carbon nanofiber capacitive touch sensors for robotic skin applications
Srinivasarao Yaragalla,Simeone Dussoni,Muhammad Zahid,Marco Maggiali,Giorgio Metta,Athanassia Athanasiou,Ilker S. Bayer 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.101 No.-
Stretchable capacitive tactile sensors are crucial for the current and future soft robotic technology, particularlyfor designing artificial electronic skin for robots. In this study, we fabricated stretchable electronictactile sensors by spray coating of conductive graphene nanoplatelets (GNPs) or carbonnanofibers (CNFs) with liquid natural rubber (NR) binder over stretchable nitrile rubber (NBR) sheets. CNF-based coatings showed remarkably low sheet resistance of 30 X sq 1 and much better current transmissionpatterns under elongation, with ~50% current transmission reduction under 50% elongation,compared to GNP-based coatings with 600 X sq 1 resistance and ~99% current transmission reductionunder 50% elongation. Structural damages/cracks within the coatings due to repeated stretch-releasecycles could be healed by a rapid convective heat annealing process, restoring to initial current. Hapticsensing properties of the fabricated flexible capacitive device based on CNFs-coated nitrile rubber wereevaluated by connecting it to a printed circuit board (PCB). The device could easily sense tactile forcesfrom tens of mN to a few N, corresponding to (10 2–10) kPa pressure range over curvilinear surfacesor under elongation.
Bimodally grained high-strength Fe fabricated by mechanical alloying and spark plasma sintering
Srinivasarao, B.,Oh-ishi, K.,Ohkubo, T.,Hono, K. Elsevier Science 2009 Acta materialia Vol.57 No.11
Nanocrystalline iron containing a certain fraction of coarse grains with nanosized oxide dispersoids has been processed by mechanically milling Fe powder and subsequent spark plasma sintering. Sintered samples exhibited a high tensile strength of 2100MPa with 5% ductility; by optimizing the sintering conditions, it was possible to tune the strength-ductility balance. The optimally sintered material showed a tensile strength of 1500MPa and 15% elongation. The microstructure consists of nanograined (<100nm) as well as coarse-grained regions (>1μm) with uniform dispersion of nanosized chromium oxide particles (∼10nm). The strength and elongation show strong dependence on the volume fraction of the coarse grains, and the high strength can be attributed to the ultrafine grain size of the nanograined regions and precipitation hardening by the oxide dispersoids. The ductility is considered to be due to the presence of coarse grains.
On a Symbolic Method for Fully Inhomogeneous Boundary Value Problems
Thota, Srinivasarao Department of Mathematics 2019 Kyungpook mathematical journal Vol.59 No.1
This paper presents a symbolic method for solving a boundary value problem with inhomogeneous Stieltjes boundary conditions over integro-differential algebras. The proposed symbolic method includes computing the Green's operator as well as the Green's function of the given problem. Examples are presented to illustrate the proposed symbolic method.
On A Symbolic Method for Error Estimation of a Mixed Interpolation
Thota, Srinivasarao Department of Mathematics 2018 Kyungpook mathematical journal Vol.58 No.3
In this paper, we present a symbolic formulation of the error obtained due to an approximation of a given function by the mixed-interpolating function. Using the proposed symbolic method, we compute the error evaluation operator as well as the error estimation at any arbitrary point. We also present an algorithm to compute an approximation of a function by the mixed interpolation technique in terms of projector operator. Certain examples are presented to illustrate the proposed algorithm. Maple implementation of the proposed algorithm is discussed with sample computations.
Symbolic Algorithm for a System of Differential-Algebraic Equations
Thota, Srinivasarao,Kumar, Shiv Datt Department of Mathematics 2016 Kyungpook mathematical journal Vol.56 No.4
In this paper, a symbolic algorithm for solving a regular initial value problem (IVP) for a system of linear differential-algebraic equations (DAEs) with constant coeffcients has been presented. Algebra of integro-differential operators is employed to express the given system of DAEs. We compute a canonical form of the given system which produces another simple equivalent system. Algorithm includes computing the matrix Green's operator and the vector Green's function of a given IVP. Implementation of the proposed algorithm in Maple is also presented with sample computations.