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Reconstruction methodology of a Francis runner blade using numerical tools
Giovanni Delgado,Sergio Galván,Francisco Dominguez-Mota,J. C. García,Esteban Valencia 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.3
In a hydraulic turbine, the search of a better energy exchange with the fluid has led to designs of runner blade of geometrical shapes so complex that they are considered as free-form surfaces. Since such blade characteristics are unable to be expressed by analytic functions, its complete and realistic geometrical reconstruction requires an excessive quantity of design parameters. This study proposes a coherent and robust full 3D blade numerical reconstruction methodology in which the geometrical definition of the blade is independent of its design parameters. A quantitative and qualitative fit evaluation shows that the blade surface reconstruction needs an important quantity of discrete data along the spanwise and streamwise direction to achieve a continuous and smooth definition. The results infer that the shape characteristics of damaged and worn blades without an original CAD model could be recovered, making this methodology attractive for industrial and optimization applications.
Lee, Jin Hong,Chu, Kanghyun,Ü,nal, Ahmet A.,Valencia, Sergio,Kronast, Florian,Kowarik, Stefan,Seidel, Jan,Yang, Chan-Ho American Physical Society 2014 Physical review. B, Condensed matter and materials Vol.89 No.14
<P>Phase separation of two different isosymmetric phases can occur as a result of their similar ground state energies. We have found such phase separation in a multiferroic system at a tensile-strain-driven morphotropic phase boundary of rhombohedral and orthorhombic bismuth ferrite. We utilize the emergent phase competition in order to implement three-step electric switching of ferroelectric polarization as well as rotation of the magnetic easy axis using electric fields. This observation provides a pathway to phase-competition-driven magnetoelectric devices.</P>
Lee, Jin Hong,Kim, Kwang-Eun,Jang, Byung-Kweon,Ü,nal, Ahmet A.,Valencia, Sergio,Kronast, Florian,Ko, Kyung-Tae,Kowarik, Stefan,Seidel, Jan,Yang, Chan-Ho American Physical Society 2017 Physical Review B Vol.96 No.6
<P>Implementation of antiferromagnetic compounds as active elements in spintronics has been hindered by their insensitive nature against external perturbations which causes difficulties in switching among different antiferromagnetic spin configurations. Electrically controllable strain gradient can become a key parameter to tune the antiferromagnetic states of multiferroic materials. We have discovered a correlation between an electrically written straight-stripe mixed-phase boundary and an in-plane antiferromagnetic spin axis in highly elongated La-5%-doped BiFeO3 thin films by performing polarization-dependent photoemission electron microscopy in conjunction with cluster model calculations. A model Hamiltonian calculation for the single-ion anisotropy including the spin-orbit interaction has been performed to figure out the physical origin of the link between the strain gradient present in the mixed-phase area and its antiferromagnetic spin axis. Our findings enable estimation of the strain-gradient- induced magnetic anisotropy energy per Fe ion at around 5 x 10(-12) eV m, and provide a pathway toward an electric-field-induced 90 degrees rotation of antiferromagnetic spin axis at room temperature by flexomagnetism.</P>