• Smart Structures and Systems
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• 제18권3호
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• pp.471-484
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• 2016

Optical fiber sensors have been proven that they have the potential to detect high-frequency ultrasonic signals, in structural health monitoring field which generally refers to acoustic emission signals from active structural damages and guided waves excited by ultrasonic actuators and propagating in waveguide. In this work, the sensing properties of optical fiber sensors based on Mach-Zehnder interferometer were investigated in the metal plate. Analytical formulas were conducted first to explore the parameters affecting its sensing performances. Due to the simple and definable frequency component, the Lamb wave excited by the piezoelectric wafer was employed to study the sensitivity of the proposed optical fiber sensors with respect to the frequency, rather than the acoustic emission signals. In the experiments, according to above investigations, spiral shape optical fiber sensors with different size were selected to increase their sensitivity. Lamb waves were excited by a circular piezoelectric wafer, while another piezoelectric wafer was used to compare their voltage responses. Furthermore, by changing the excitation frequency, the tuning frequency characteristic of the proposed optical fiber sensor was also investigated experimentally.

• Journal of information and communication convergence engineering
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• 제5권3호
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• pp.223-228
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• 2007

This paper deals with the secondary excited induction generator applied to random wave input generation system. As it is preferred to stabilize the output voltage and frequency in the constant level, microcomputer controlled CSI connected to the secondary windings supplies the secondary current with slip frequency. For testing this method, the input torque simulator is constructed, according to the power flow analysis. The experimental and numerical results show the advantage of secondary excited induction generator system for the random input wave generation system.

• Bulletin of the Korean Chemical Society
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• 제18권12호
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• pp.1281-1285
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• 1997

The time-dependent tracking inversion method is developed to extract the potential of the excited state from frequency-domain measurements, such as the absorption profile. Based on the relay of the regularized inversion procedure and time-dependent wave-packet propagation, the algorithm extract the underlying potential piece by piece by tracking the time-dependent data which can be synthesized from frequency-domain measurements. We have demonstrated the algorithm to extract the potential of excited state for a model diatomic molecule. Finally, we describe the merits of the time-dependent tracking inversion method compared to the time-dependent inversion and discuss several extensions of the algorithm.

• Bulletin of the Korean Chemical Society
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• 제19권12호
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• pp.1359-1363
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• 1998

The p-fluorobenzyl radical was generated from the p-fluorotoluene and vibronically excited in a corona excited supersonic expansion with inert buffer gases. The vibronic emission spectra of the jet cooled p-fluorobenzyl radical in the D1 → D0 transition have been observed in the visible region. The spectra exhibit several low frequency sequence bands in the vicinity of the every strong vibronic band. The characteristics of the sequence bands have been examined by varying the experimental conditions such as carrier gas and nozzle size to identify the origin of the transition in the spectra.

• 대한의용생체공학회:의공학회지
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• 제24권2호
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• pp.121-126
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• 2003

본 연구는 진동형 장치의 활용을 통해 혈관 내 폐 보조장치의 기체전달 효율을 향상시키고자 시도하였으며, 진동에 따른 혈액의 용혈 문제에 있어서 한계 용혈이 발생하는 영역을 선정하고자 하였다. 가진 주파수가 0 Hz일 때를 기준으로 하여 중공사 수의 변화에 따라 산소전달속도를 측정하였다. 최대의 산소전달속도를 나타내는 중공사 모듈에서 가진 주파수의 변화에 따른 산소전달속도를 측정하고 혈액의 용혈도를 측정하였다. 측정결과 액체 유속의 변화에 따라 최대 산소전달속도를 나타내는 중공사 모듈은 type 6으로 이때의 중공사 개수는 675개이다. 또한, 중공사를 가진하지 않았을 때 최대의 산소전달속도를 보여주는 모듈은 type 6이었다. 모듈 type 6의 가진 주파수의 변화에 따른 산소전달속도는 7 Hz에서 최대산소전달속도를 나타내었으며 최대산소전달속도를 나타내는 7 Hz의 가진 주파수에서의 혈액 용혈도를 측정한 결과 혈액의 용혈도는 낮았다. 그러므로 최대 흔들림이 일어나는 7 Hz를 한계 용혈 주파수로 결정할 수 있었다.

• Journal of Power Electronics
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• 제12권4호
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• pp.615-622
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• 2012

The switching frequency of the power electronic devices used in large synchronous motor drives is usually kept low (less than 1 kHz) to reduce the switching losses and to improve the converter power capability. However, this results in a couple of problems, e.g. an increase in the harmonic components of the stator current, and an undesired cross-coupling between the magnetization current component ($i_m$) and the torque component ($i_t$). In this paper, a novel complex matrix model of electrically excited synchronous motors (EESM) was established with a new control scheme for coping with the low switching frequency issues. First, a hybrid observer was proposed to identify the instantaneous fundamental component of the stator current, which results in an obvious reduction of both the total harmonic distortion (THD) and the low order harmonics. Then, a novel complex current controller was designed to realize the decoupling between $i_m$ and $i_t$. Simulation and experimental results verify the effectiveness of this novel control system for EESM drives.

• 한국조명전기설비학회지:조명전기설비
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• 제9권4호
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• pp.78-85
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• 1995

This paper covers stability and stabilization of Multi-Excited Induction Motor used in numberous electric equipment system of industrial field. The induction motor with multi-excitation has tow sets of three-phase system : One is connected to the AC source to supply most power required at the load, and the other is to the inverter for variable frequency and/or magnitude of voltage. The conventional induction motor is operated under single excitation mode only, that is called induction mode. But in multi-excited induction motor both the induction mode and the synchronous mode are possible, and the proposed multi-excited induction motor can be driven as a synchronous motor by the extra three-phase input. At the synchronous mode the efficiency is improved so higher than that at induction mode or conventional induction motor. The rating of the inverter used for speed control of numberous electric equipment system can be reduced upto one-tenth of that for conventional induction motor. Also the cost and maintenance fee of multi-excited induction motor can be reduced compared to any other motor.

• 한국자동차공학회논문집
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• 제11권6호
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• pp.171-182
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• 2003

Tire vibration modes are known to play a key role in vehicle ride and comfort characteristics. Inputs to the tire such as impacts, rough road surface, tire nonuniformities, and tread patterns can potentially excite tire vibration. In this study, experimental modal analysis on the tire in ground contact are performed by a 3-D impact at the center of contact patch to investigate which modes of tire influence the vibration of wheel and axle. Through the experiment, the vibration transmission properties from tire to axle are examined. And we have compared the influential tire modes when the tire is excited by a vertical impact with those when excited by the 3-D impact. Additionally, the modes of ground contact tire are compared with those of the suspended tire.

• Journal of information and communication convergence engineering
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• 제7권1호
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• pp.46-51
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• 2009

In this paper, the two-axis theory is adopted to analyze the secondary excited induction generator applied to random wave input generation system. The analysis by the two-axis theory helps to know the transmitted power of the induction machine. The electric variables, like as primary and secondary currents, voltages, and electric output power, were able to express as equations. These equations are help to simulate the generation system numerical model and to know the transient state of the system. As it is preferred to stabilize the output voltage and frequency in the constant level, microcomputer controlled VSI connected to the secondary windings supplies the secondary current with slip frequency. For testing the appropriateness of this method, the input torque simulator in the laboratory to drive the secondary excited results show the advantage of secondary excited induction generator system for the random input wave generation system.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.I
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• pp.513-514
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• 2005

In plasma processing reactors, it is common practice to control plasma density and ion bombardment energy by manipulating excitation voltage and frequency. In this paper, a dually excited capacitively coupled rf plasma reactor is self-consistently simulated with a three moment model. Effects of phase differences between primary and secondary voltage waves, simultaneously modulated at various combination of commensurate frequencies, on plasma properties are investigated. The simulation results show that plasma potential and density as well as primary self-dc bias are nearly unaffected by the phase lag between the primary and the secondary voltage waves. The results also show that, with the secondary frequency substantially lower than the primary frequency, secondary self-dc bias remains constant regardless of the phase lag. As the secondary frequency approaches to the primary frequency, however, the secondary self-dc bias becomes greatly altered by the phase lag, and so does the ion bombardment energy at the secondary electrode. These results demonstrate that ion bombardment energy can be more carefully controlled through plasma simulation.