• International Journal of Fluid Machinery and Systems
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• v.2 no.3
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• pp.197-205
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• 2009

Since large-scale commercial wind turbine generator systems such as MW-class wind turbines are becoming widely operated, the vibration and distortion of the blade are becoming larger and larger. Therefore the soft structure design instead of the solid-design is one of the important concepts to reduce the structural load and the cost of the wind turbine rotors. The objectives of the study are development of the fluid-structure coupled analysis code and evaluation of soft rotor-blade design to reduce the unsteady structural blade load. In this paper, fluid-structure coupled analysis for the HAWT rotor blade is performed by free wake panel method coupled with hinge-spring blade model for the flapwise blade motion. In the model, the continuous deflection of the rotor blade is represented by flapping angle of the hinge with one degree of freedom. The calculation results are evaluated by comparison with the database of the NREL unsteady aerodynamic experiment. In the analysis the unsteady flapwise moments in yawed inflow conditions are compared for the blades with different flapwise eigen frequencies.

• Advances in nano research
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• v.13 no.3
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• pp.259-267
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• 2022

Two-dimensional (2D) transition metal carbides/nitrides or "MXenes" belong to a diverse-class of layered compounds, which offer composition- and electric-field-tunable electrical and physical properties. Although the majority of the MXenes, including Ti₃C₂T_x, are metallic, they typically show semiconductor-like behaviour in their percolated thin-film structure; this is also the most common structure used for fundamental studies and prototype device development of MXene. Magnetoconductance studies of thin-film MXenes are central to understanding their electronic transport properties and charge carrier dynamics, and also to evaluate their potential for spin-tronics and magnetoelectronics. Since MXenes are produced through solution processing, it is desirable to develop deposition strategies such as inkjet-printing to enable scale-up production with intricate structures/networks. Here, we systematically investigate the extrinsic negative magnetoconductance of inkjetprinted Ti₃C₂T_x MXene thin-films and report a crossover from weak anti-localization (WAL) to weak localization (WL) near 2.5K. The crossover from WAL to WL is consistent with strong, extrinsic, spin-orbit coupling, a key property for active control of spin currents in spin-orbitronic devices. From WAL/WL magnetoconductance analysis, we estimate that the printed MXene thin-film has a spin orbit coupling field of up to 0.84 T at 1.9 K. Our results and analyses offer a deeper understanding into microscopic charge carrier transport in Ti₃C₂T_x, revealing promising properties for printed, flexible, electronic and spinorbitronic device applications.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.26 no.2
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• pp.96-109
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• 2021

Since terrestrial input plays a major role in coastal primary production, an understanding of land-ocean coupling (LOC) is key to understand coastal ecological changes. In this study, the LOC has been classified into three stages (i.e., the baseflow, plume event and residual flow). In order to characterize its pattern in Nakdong River estuary, multi-platform data were obtained from remote sensing (geostationary ocean color image (GOCI)), in-situ measurement (marine environment information system (MEIS)), on-site measurement (discharge data and meteorological data). The MEIS data were grouped into three stages of LOC using principal component analysis (PCA), and the LOC (2013 ~ 2018) was examined at each stage using multi-platform data. In the Nakdong River estuary, the maximum value of chlorophyll-a (chl-a) was unexpectedly appeared during the plume event. It is assumed that there was no significant increase in turbidity, expected during the typical plume event, together with the weak flushing effect, caused the enhanced phytoplankton growth. Compared with other estuaries, LOC is common in estuaries affected by freshwater inflow, but LOC has different pattern depending on the size of the plume. While estuaries that form small plumes of about 10 km (low freshwater discharge and weak flushing effect) observed high chl-a in the plume event because the phytoplankton can response to the increased nutrient more rapidly. estuaries that form large plumes of more than 100 km est (high freshwater discharge and strong flushing effect) follow the typical LOC pattern conceptualized in this study (high chl-a in the residual flow).

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.1
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• pp.133-139
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• 1987

A phase-locked Channel-Substrate-Planar(CSP) laser arrays is described. Arrays of emitters with weak coupling are operated in a set of discrete modes determined by the number and spacing of the emitters. The interactions between emitters lead to a splitting of the wave-length and gain which are calculated from the coupling strength. Phase-locked arrays has exhibited to CW output-power as high as 80 m W and the highest order mode will have preferred oscillation. A strong hole burning is occurred at p=30m W. The most stable lasing mode is occurred at element spacing S=3.5\ulcornerm and there is no coupling at S>7 \ulcornerm.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.529-534
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• 2000

A finite element analysis for a rotating cantilever beam is presented in this study. Based on a dynamic modelling method using the stretch deformation instead of the conventional axial deformation, three linear partial differential equations are derived from Hamilton's principle. Two of the linear differential equations show the coupling effect between stretch and chordwise deformations. The other equation is an uncoupled one for the flapwise deformation. From these partial differential equations and the associated boundary conditions, are derived two weak forms: one is for the chordwise motion and the other is for the flapwise motion. The weak forms are spatially discretized with newly defined two-node beam elements. With the discretized equations or the matrix-vector equations, the behaviours of the natural frequencies are investigated for the variation of the rotating speed.

• Journal of Aerospace System Engineering
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• v.14 no.1
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• pp.16-20
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• 2020

The fatigue happening during the road riding of the vehicle and for the moment the aircraft lands on the runway is closely related to the life cycle of the landing gear, the airframe, the vehicle's suspension, etc. The multiple loads acting on the wheel are longitudinal, lateral, vertical, and braking forces. To study the dynamic characteristics and fatigue stiffness of the vehicle, the dynamic fatigue simulator generally has been used to represent the real road vibration in the lab. It can save time and cost. In hardware, the critical factor in the hydraulic fatigue simulator structure is to decouple each axis and to endure several load vibration. In this paper, the inverse kinematic analysis method derives the magnitude of movement of the hydraulic servo actuator by the coupling after rendering the maximum movement displacement in the axial direction at the center of the dummy wheel. The result of the analysis is that the coupling between the axes is weak to reproduce the real road vibrations precisely.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.4
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• pp.509-518
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• 2019

Analyses with various Sea Surface Temperature (SST) products indicate that the interannual variability of the area-averaged SST in the East/Japan Sea (EJS) is well correlated to that of Pacific Decadal Oscillation (PDO) during 1979-2018, especially in the autumn. The regression analysis with the wind vectors at 200 hPa, where the strongest jet stream flows, suggests that the long-term variability of the intensity as well as the meridional movement of the jet stream are related to the coupling of the autumn EJS SST and PDO. When the axis of the jet stream moves poleward (equatorward) with its weakening (strengthening), both the EJS SST and North Pacific SST increase (decrease). This suggests that both the intensity and meridional movement of the jet stream are possibly related to the coupling of the autumn EJS SST and PDO. However, effects of a weak jet stream during the summer and the strong East Asian winter monsoon make weak coupling between the EJS SST and PDO.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1006-1007
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• 2015

Recent improvement in semiconductor technology make efficient switching possible at higher frequencies, which benefits the application of wireless inductive energy transfer. However, a higher frequency does not alter the magnetic coupling between energy transmitter and receiver. Due to the still weak magnetic coupling between transmitting and receiving sides that are separated by a substantial air gap, energy circulates in the primary transmitting side without being transferred to the secondary receiving side. This paper proposes an analysis on the system efficiency to determine the optimal impedance requirement for coils, rectifier and DC-DC Converter. A novel Boost DC-DC Converter is designed to provide the optimal impedance matching in WPT(Wireless Power Transfer) system for various loads.

• Journal of the Korean Magnetic Resonance Society
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• v.22 no.4
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• pp.76-81
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• 2018

Investigation of the protein-protein interaction mode at atomic resolution is essential for understanding on the underlying functional mechanisms of proteins as well as for discovering druggable compounds blocking deleteriou interprotein interactions. Solution NMR spectroscopy provides accurate and precise information on intermolecular interactions even for weak and transient interactions, and it is also markedly useful for examining the change in the conformation and dynamics of target proteins upon binding events. In this mini-review, we comprehensively describe three unique and powerful methods of solution NMR spectroscopy, paramagnetic relaxation enhancement (PRE), pseudo-contact shift (PCS), and residual dipolar coupling (RDC), for the study on protein-protein interactions.

• Journal of Korean Society of Steel Construction
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• v.24 no.4
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• pp.371-382
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• 2012

Existing shear wall system may cause ductility fallen to the structure which it is on because relatively weak concrete core would easy to be damaged. In this study, steel hysteresis dampers whose stiffness is higher than existing coupling beam and whose strength is easy to change depending on design load was used in coupling beam. The steel hysteresis damper was proposed for the shape connected in double in series, from this, several static test were conducted to verify structural performance of the damper. FEM analysis was also performed, then design equation were suggested.