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Spin Torque and Force due to Current for General Spin Textures
Tatara, Gen,Kohno, Hiroshi,Shibata, Junya,Lemaho, Yann,Lee, Kyung-Jin Physical Society of Japan 2007 Journal of the Physical Society of Japan Vol.76 No.5
<P>The nonadiabatic correction to spin transfer torque arising from fast-varying spin texture is calculated treating the conductions electron fully quantum mechanically. The torque is nonlocal in space, and is shown to be equivalent to a force (due to momentum transfer) acting on the center of mass of the texture. Another kind of force exists in the adiabatic regime, and it is identified to be of topological origin. These forces are shown to be the counter-reactions of electric transport properties, resistivity and the Hall effect.</P>
Inverse Faraday Effect Driven by Spin Chirality in Weak Ferromagnets
Katsuhisa Taguchi,Gen Tatara 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.12
We theoretically study the inverse Faraday effect in weak inhomogeneous ferromagnets with noncoplanarmagnetic structures. The effect is driven by a spin chirality of the magnetic structure andgenerates a spin polarization, which is parallel or anti-parallel to the localized magnetic moments,the direction being determined by the helicity of light.
Strouhal number of bridge cables with ice accretion at low flow turbulence
Gorski, Piotr,Pospisil, Stanislav,Kuznetsov, Sergej,Tatara, Marcin,Marusic, Ante Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.22 No.2
The paper concerns with the method and results of wind tunnel investigations of the Strouhal number (St) of a stationary iced cable model of cable-supported bridges with respect to different angles of wind attack. The investigations were conducted in the Climatic Wind Tunnel Laboratory of the Czech Academy of Sciences in $Tel{\check{c}}$. The methodology leading to the experimental icing of the inclined cable model was prepared in a climatic section of the laboratory. The shape of the ice on the cable was registered by a photogrammetry method. A section of an iced cable model with a smaller scale was reproduced with a 3D printing procedure for subsequent aerodynamic investigations. The St values were determined within the range of the Reynolds number (Re) between $2.4{\cdot}10^4$ and $16.5{\cdot}10^4$, based on the dominant vortex shedding frequencies measured in the wake of the model. The model was oriented at three principal angles of wind attack for each of selected Re values. The flow regimes were distinguished for each model configuration. In order to recognize the tunnel blockage effect the St of a circular smooth cylinder was also tested. Good agreement with the reported values in the subcritical Re range of a circular cylinder was obtained. The knowledge of the flow regimes of the airflow around an iced cable and the associated St values could constitute a basis to formulate a mathematical description of the vortex-induced force acting on the iced cable of a cable-supported bridge and could allow predicting the cable response due to the vortex excitation phenomenon.
Structural evaluation of all-GFRP cable-stayed footbridge after 20 years of service life
Piotr Górski,Beata Stankiewicz,Marcin Tatara 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.29 No.4
The paper presents the study on a change in modal parameters and structural stiffness of cable-stayed Fiberline Bridge made entirely of Glass Fiber Reinforced Polymer (GFRP) composite used for 20 years in the fjord area of Kolding, Denmark. Due to this specific location the bridge structure was subjected to natural aging in harsh environmental conditions. The flexural properties of the pultruded GFRP profiles acquired from the analyzed footbridge in 1997 and 2012 were determined through three-point bending tests. It was found that the Young's modulus increased by approximately 9%. Moreover, the influence of the temperature on the storage and loss modulus of GFRP material acquired from the Fiberline Bridge was studied by the dynamic mechanical analysis. The good thermal stability in potential real temperatures was found. The natural vibration frequencies and mode shapes of the bridge for its original state were evaluated through the application of the Finite Element (FE) method. The initial FE model was created using the real geometrical and material data obtained from both the design data and flexural test results performed in 1997 for the intact composite GFRP material. Full scale experimental investigations of the free-decay response under human jumping for the experimental state were carried out applying accelerometers. Seven natural frequencies, corresponding mode shapes and damping ratios were identified. The numerical and experimental results were compared. Based on the difference in the fundamental natural frequency it was again confirmed that the structural stiffness of the bridge increased by about 9% after 20 years of service life. Data collected from this study were used to validate the assumed FE model. It can be concluded that the updated FE model accurately reproduces the dynamic behavior of the bridge and can be used as a proper baseline model for the long-term monitoring to evaluate the overall structural response under service loads. The obtained results provided a relevant data for the structural health monitoring of all-GFRP bridge.
CONTROL STRATEGIES FOR AC/DC MOTOR DRIVES
Susuma TAKAKUMA,Haruo NAITOH,Isao MORI,Shinji TATARA 전력전자학회 1989 ICPE(ISPE)논문집 Vol.- No.-
A survey on the state of art of the application of modern control theory is presented. The historical background and general features of the theory are described as an introduction. It is followed by overview of papers on the subject with respect to various aspects of ac/dc motor drives. Three examples applied to the vector controlled induction motors are briefed for materialized idea.
Strouhal number of bridge cables with ice accretion at low flow turbulence
Piotr Gorski,Stanislav Pospisil,Sergej Kuznetsov,Marcin Tatara,Ante Marusic 한국풍공학회 2016 Wind and Structures, An International Journal (WAS Vol.22 No.2
The paper concerns with the method and results of wind tunnel investigations of the Strouhal number (St) of a stationary iced cable model of cable-supported bridges with respect to different angles of wind attack. The investigations were conducted in the Climatic Wind Tunnel Laboratory of the Czech Academy of Sciences in Telč. The methodology leading to the experimental icing of the inclined cable model was prepared in a climatic section of the laboratory. The shape of the ice on the cable was registered by a photogrammetry method. A section of an iced cable model with a smaller scale was reproduced with a 3D printing procedure for subsequent aerodynamic investigations. The St values were determined within the range of the Reynolds number (Re) between 2.4•104 and 16.5•104, based on the dominant vortex shedding frequencies measured in the wake of the model. The model was oriented at three principal angles of wind attack for each of selected Re values. The flow regimes were distinguished for each model configuration. In order to recognize the tunnel blockage effect the St of a circular smooth cylinder was also tested. Good agreement with the reported values in the subcritical Re range of a circular cylinder was obtained. The knowledge of the flow regimes of the airflow around an iced cable and the associated St values could constitute a basis to formulate a mathematical description of the vortex-induced force acting on the iced cable of a cable-supported bridge and could allow predicting the cable response due to the vortex excitation phenomenon.