• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.729-737
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• 2014

A study has been carried out that effectively controls the vibration of asymmetric cable-stayed bridges caused by earthquakes with MR dampers. In order to enhance the practical serviceability of MR dampers, an asymmetric cable-stayed bridge structure has been designed and produced, and a MR damper has been produced so as to have this bridge structure controlled appropriately. An experiment that controls vertical and horizontal vibrations has been carried out by exciting the asymmetric cable-stayed bridge in the horizontal direction with the El-centro seismic wave. The control performance of the MR damper has been evaluated under the five control conditions in the experiments of vibration control in each direction. As a result of the experiment, MR dampers were proved to control vibrations more effectively when either Lyapunov control algorithm or Clipped-optimal control algorithm was used to control vibrations of the asymmetric cable-stayed bridge caused by earthquakes. In addition, different controlling effects were found in vibration controls in vertical and horizontal directions due to the asymmetry of the structure and the horizontal excitation. With such controlling effects, semi-active MR dampers are evaluated to effectively control vibrations caused by earthquakes in flexible and asymmetric structures such as asymmetric cable-stayed bridges.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.7
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• pp.713-718
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• 2006

Supersonic jet fighter aircraft have several different weapon loading configuration to support air-to-air combat and air-to-ground delivery of weapon modes. Especially, asymmetric loading configurations could result in decreased handling qualities for the pilot maneuvering of the aircraft. The design of the T-50 lateral-directional roll axis control laws change from beta-betadot feedback structure to simple roll rate feedback structure and gains such as F-16 in order to improve roll-off phenomena during pitch maneuver in asymmetric loading configuration. Consequently, it is found that the improved control law decreases the roll-off phenomenon in lateral axes during pitch maneuver, but initial roll response is very fast and wing pitching moment is increased. In this paper, we propose the lateral control law blending between beta-betadot and simple roll rate feedback system in order to decreases the roll-off phenomenon in lateral axes during pitch maneuver without degrading of roll performance.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.11
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• pp.713-719
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• 2000

This paper presents an approach toward improving the performance of Moving Coil Type Linear Oscillatory Actuator (MC-LOA) with the application of Finite Element Method (FEM) to a simple control system. MC-LOA has an unbalanced magnetic circuit due to its asymmetric structure and there is a different flux distribution on the air-gap along the current direction. The interaction driven by two fluxes between the Permanent Magnet (PM) and the current causes the unbalanced thrust and interferes with the proper oscillation of MC-LOA. In order to solve the above problems and improve the driving performance, it is necessary to analyze the rate of the unbalanced thrust according to the current direction by using FEM. Then, the analysis results are used to determine the input currents for both directions. Controlling the input currents can be easily achieved by a simple control system, such as Pulse Width Modulation (PWM), without complex units. The validity of the approach is verified by the experimental results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.8
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• pp.1416-1421
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• 2008

A 10 dB branch line hybrid coupler included with defected ground structure (DGS) is proposed. In this contribution, a contact between the grounded metal housing and DGS is avoided, which has been a serious problem in applying DGS to high frequency circuits. An isolation between the metal housing and the DGS pattern is provided by inserting additional substrate between DGS and the metal package. Therefore, it is possible to design branch line hybrid couplers having highly asymmetric power dividing ratio using these DGS structure, which is demonstrated in this paper. The designed and fabricated branch line hybrid coupler using DGS is well packaged in a metal housing without touching the ground metal directly. The measurement is performed under realistic practical operating situations because it is packaged in a metal housing. The measured performances of the fabricated 10dB coupler shows a 1:9 asymmetric power dividing ratio at output ports, as predicted. In addition, the measured performances in terms of matching, isolation, and phase difference are in excellent agreement with the simulated characteristics.

• Proceedings of the Membrane Society of Korea Conference
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• 1997.10a
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• pp.81-82
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• 1997

1. Introduction : The growth of membrane science was initiated by the invention of asymmetric membrane which can be formed by the technique known as phase inversion. The basic procedure of phase inversion involves casting a thin film of polymer solution onto a suitable substrate followed by immersion in a coagulation bath (quench step). Therefore, events occurring during the quench period, at which time solvent-nonsolvent exchange and eventual polymer precipitation take place, can play a controlling role in the determination of ultimate membrane structure.

• ETRI Journal
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• v.29 no.6
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• pp.811-813
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• 2007

We report on a ridge waveguide laser diode with laterally tapered waveguides fabricated in a single growing step using a double patterning method. In this structure, nearly constant output power is obtained with the change of the lower tapered waveguide width, and the facet power ratio of 1.4 to 1.5 is observed over the current range. The asymmetric facet power property is also investigated.

• Structural Engineering and Mechanics
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• v.66 no.5
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• pp.637-648
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• 2018

When the centers of mass and stiffness of a building do not coincide, the structure experiences torsional responses. Such systems can consist of the underlying soil and the super-structure. The underlying soil may modify the earthquake input motion and change structural responses. Specific effects of the input motion shall also not be ignored. In this study, seismic demands of asymmetric buildings considering soil-structure interaction (SSI) under near-fault ground motions are evaluated. The building is modeled as an idealized single-story structure. The soil beneath the building is modeled by non-linear finite elements in the two states of loose and dense sands both compared with the fixed-base state. The infinite boundary conditions are modelled using viscous boundary elements. The effects of traditional and yield displacement-based (YDB) approaches of strength and stiffness distributions are considered on seismic demands. In the YDB approach, the stiffness considered in seismic design depends on the strength. The results show that the decrease in the base shear considering soft soil induced SSI when the YDB approach is assumed results only in the center of rigidity to control torsional responses. However, for fixed-base structures and those on dense soils both centers of strength and rigidity are controlling.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.5
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• pp.10-15
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• 2012

In this work, we proposed the asymmetric MQW structure with gradually increased or decreased well thickness from n-layers to p-layers in order to improve the performance of DUV-LEDs. We report the simulation results of electrical/optical characteristics by using the SimuLED program. From the simulation results, we found that B structure with thickness of the wells gradually increased from the n-side to the p-side has the same forward voltage(Vf) as standard structure, but the light output power (Pout) was improved by a factor of 1.17 at 20mA compared with those of the standard structure.

• Earthquakes and Structures
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• v.23 no.2
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• pp.169-181
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• 2022

To research the dynamic response of the high-rise structure under the rocking ground motion, which we believed that the effect cannot be ignored, especially accompanied by vertical ground motion. Theoretical analysis and shaking table seismic simulation tests were used to study the response of a high-rise structure to excitation of a H-V-R ground motion that included horizontal, vertical, and rocking components. The use of a wavelet analysis filtering technique to extract the rocking component from data for the primary horizontal component in the first part, based on the principle of horizontal pendulum seismogram and the use of a wavelet analysis filtering technique. The dynamic equation of motion for a high-rise structure under H-V-R ground motion was developed in the second part, with extra P-△ effect due to ground rocking displacement was included in the external load excitation terms of the equation of motion, and the influence of the vertical component on the high-rise structure P-△ effect was also included. Shaking table tests were performed for H-V-R ground motion using a scale model of a high-rise TV tower structure in the third part, while the results of the shaking table tests and theoretical calculation were compared in the last part, and the following conclusions were made. The results of the shaking table test were consistent with the theoretical calculation results, which verified the accuracy of the theoretical analysis. The rocking component of ground motion significantly increased the displacement of the structure and caused an asymmetric displacement of the structure. Thus, the seismic design of an engineering structure should consider the additional P-△ effect due to the rocking component. Moreover, introducing the vertical component caused the geometric stiffness of the structure to change with time, and the influence of the rocking component on the structure was amplified due to this effect.

• Structural Engineering and Mechanics
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• v.33 no.1
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• pp.95-107
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• 2009

A method for vibration analysis of asymmetric shear wall and Thin walled open section structures is presented in this paper. The whole structure is idealized as an equivalent bending-warping torsion beam in this method. The governing differential equations of equivalent bending-warping torsion beam are formulated using continuum approach and posed in the form of simple storey transfer matrix. By using the storey transfer matrices and point transfer matrices which consider the inertial forces, system transfer matrix is obtained. Natural frequencies can be calculated by applying the boundary conditions. The structural properties of building may change in the proposed method. A numerical example has been solved at the end of study by a program written in MATLAB to verify the presented method. The results of this example display the agreement between the proposed method and the other valid method given in literature.