• Smart Structures and Systems
• /
• 제21권5호
• /
• pp.677-686
• /
• 2018

The structural responses are often used to identify the structural local damages. However, it is usually difficult to gain the responses of the track, as the sensors cannot be installed on the track directly. The vehicles running on a track excite track vibration and can also serve as response receivers because the vehicle dynamic response contains the vibration information of the track. A damage identification method using the vehicle responses and sensitivity analysis is proposed for the vehicle-track coupling system in this paper. Different from most damage identification methods of vehicle-track coupling system, which require the structural responses, only the vehicle responses are required in the proposed method. The local damages are identified by a sensitivity-based model updating process. In the vehicle-track coupling system, the track is modeled as a discrete point supported Euler-Bernoulli beam, and two vehicle models are proposed to investigate the accuracy and efficiency of damage identification. The measured track irregularity is considered in the calculation of vehicle dynamic responses. The measurement noises are also considered to study their effects to the damage identification results. The identified results demonstrate that the proposed method is capable to identify the local damages of the track accurately in different noise levels with only the vehicle responses.

• Structural Engineering and Mechanics
• /
• 제22권1호
• /
• pp.85-105
• /
• 2006

Control of structural response due to seismic excitation in a manner of coupling adjacent buildings has been actively developed, and most attention focused on those buildings of similar height. However, with the rapid development of some modern cities, multi-story buildings constructed with an auxiliary low-rise podium structure to provide extra functions to the complex become a growing construction scheme. Being inspired by the positively examined coupling control approach for buildings with similar height, this paper aims to provide a comprehensive analytical study on control effectiveness of using friction dampers to link the two buildings with significant height difference to supplement the recent experimental investigation carried out by the writers. The analytical model of a coupled building system is first developed with passive friction dampers being modeled as Coulomb friction. To highlight potential advantage of coupling the main building and podium structure with control devices that provide a lower degree of coupling, the inherent demerit of rigid-coupled configuration is then evaluated. Extensive parametric studies are finally performed. The concerned parameters influencing the design of optimal friction force and control efficiency include variety of earthquake excitation and differences in floor mass, story number as well as number of dampers installed between the two buildings. In general, the feasibility of interaction control approach applied to the complex structure for vibration reduction due to seismic excitation is supported by positive results.

• Journal of Power Electronics
• /
• 제19권3호
• /
• pp.637-644
• /
• 2019

Wireless power transfer (WPT) technology with various transfer mechanisms such as inductive coupling, magnetic resonance and capacitive coupling is being widely researched. Until now, power transfer efficiency (PTE) and power transfer capability (PTC) have been the primary concerns for designing and developing WPT systems. Therefore, a lot of studies have been documented to improve PTE and PTC. However, power consumption in the standby mode, also defined as the no-load mode, has been rarely studied. Recently, since the number of WPT products has been gradually increasing, it is necessary to develop techniques for reducing the standby power consumption of WPT systems. This paper investigates the standby power consumption of commercial WPT products. Moreover, a standby power reduction technique for WPT systems via magnetic resonance coupling (MRC) with a parallel resonance type resonator is proposed. To achieve a further standby power reduction, the voltage control of an AC/DC travel adapter is also adopted. The operational principles and characteristics are described and verified with simulation and experimental results. The proposed method greatly reduces the standby power consumption of a WPT system via MRC from 2.03 W to 0.19 W.

• 한국광학회지
• /
• 제21권1호
• /
• pp.26-32
• /
• 2010

플라스틱 광섬유의 주기적인 bending을 이용한 누설광섬유에 기반을 둔 라인램프를 제안하고, 그 핵심요소로서 높은 광결합효율을 갖는 LED-광섬유 결합기를 설계 및 해석하였다. Monte Carlo photon simulation 기법을 이용하여 해석한 결과, 결합기의 광결합효율은 반사컵 옆면의 기울기각 $\theta_w$와 반사컵의 반사도 $\rho_{ref}$에 대해 상대적으로 민감하게 영향을 받는 사실을 확인할 수 있었다. 광결합효율은 $\theta_w=60^{\circ}C$ 근처에서 최대가 되었는데, 이 값은 일반적인 LED 램프에서 흔히 사용하는 반사컵 옆면의 기울기각 $\theta_w=45^{\circ}$보다 상당히 큰 값이다. 그리고 반사컵의 반사도 $\rho_{ref}$가 0.8정도 이상이 되면, 광결합효율은 보통의 LD-광섬유 결합기에서 얻을 수 있는 광결합효율인 80% 정도를 뛰어 넘었다.

• Tribology and Lubricants
• /
• 제34권1호
• /
• pp.23-32
• /
• 2018

Coupling is a mechanical component that transmits rotational force by connecting two shafts. Curvic coupling is widely used in high-performance systems because of its excellent power transmission efficiency and easy machining. However, coupling applications change dynamic behavior by reducing the stiffness of an entire system. Contact surface stiffness is an important parameter that determines the dynamic behavior of a system. In addition, the roughness profile of a contact surface is the most important parameter for obtaining contact stiffness. In this study, we theoretically establish the process of contact and bending stiffness analysis by considering the rough surface contact at Curvic coupling. Surface roughness parameters are obtained from Nayak's random process, and the normal contact stiffness of a contact surface is calculated using the Greenwood and Williamson model in the elastic region and the Jackson and Green model in the elastic-plastic region. The shape of the Curvic coupling contact surface is obtained by modeling a machined shape through an actual machining tool. Based on this modeling, we find the maximum number of gear teeth that can be machined according to the contact angle. Curvic coupling stiffness is calculated by considering the contact angle, and the calculation process is divided into stick and slip conditions. Based on this process, we investigate the stiffness characteristics according to the contact angle.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제54권7호
• /
• pp.343-350
• /
• 2005

Conventionally, for transferring the primary power to the secondary one, the high frequency series resonant converter has been widely used for the contactless power supply system. However, the high frequency series resonant converter has the disadvantages such as the low efficiency, the high voltage gain characteristics and deviation of the phase angle in the overall load range. To improve this disadvantages, In this paper, the characteristics of the high efficiency and unit voltage gain as well as in-phase are revealed in the proposed three-level LCLC (Inductor-Capacitor- Inductor-Capacitor) resonant converter. The results are verified on the simulation based on the theoretical analysis and the 4kW experimental Prototype.

• 한국식품영양학회지
• /
• 제12권2호
• /
• pp.191-191
• /
• 1999

A Purge & Trap Concentrator was used to analyze various volatile organic compounds(VOCs) in wat-er. The object of this study was to observe the purge efficiency of 40 VOCs in water according to the change of parameters (purge time drypurge time sample temperature) and to determine the optimum condition for VOCs using the purge & Trap concentrator interfaced with a narrow capillary connected to a gas chromatography/mass spectrometry. The optimum condition of purge and trap is as follows: purge time at 11min drypurge time at 5min sample temperature at 6$0^{\circ}C$ at constant purge flow (40mol/min) constant desorption flow(20ml/min) desorption temperature(2$25^{\circ}C$) and desorption time (1min) At this analytical condition the detection limits of VOCs was in the range of 0.1~0.5$\mu$g/ml and the purge efficiency of each compound was over 70%.

• 한국진공학회지
• /
• 제7권3호
• /
• pp.273-276
• /
• 1998

안테나에 따른 플라즈마 밀도의 균일도 연구를 위해 병렬 안테나를 설계하고 이중 랑뮤어 탐침과 자기장 측정 탐침을 이용하여 각각의 플라즈마 밀도와 자기장의 세기를 측정 하였다. 나비형 안테나를 사용했을 때 플라즈마 밀도가 ~$2\times10^{11}(\textrmcm^{-3})$로 다른 두 안테나를 사용했을 때보다 높았으며, 전자의 온도는 2eV 이하로 동일한 조건에서의 나선형 안테나보 다 낮게 나왔다. 또 전류의 방향이 서로 다른 두 개의 안테나선이 가까이 있거나 안테나 성 분끼리 양성 결합(positive coupling)을 하는 경우에는 동력 효율(power efficiency)이 매우 낮아졌다.

• Journal of the Optical Society of Korea
• /
• 제20권1호
• /
• pp.13-21
• /
• 2016

Since the direct-gradient (DG) method uses the Shack-Hartmann wave front sensor (SH-WFS), based on the phase-conjugation principle, for atmospheric compensation in free-space optical (FSO) communication, it cannot effectively correct high-order aberrations. While the stochastic parallel gradient descent (SPGD) can compensate the distorted wave front, it requires more calculations, which is sometimes undesirable for an FSO system. A hybrid compensation (HC) method is proposed by properly using the DG method and SPGD algorithm to improve the performance of FSO communication. Simulations show that this method can well compensate wave-front aberrations and upgrade the coupling efficiency with few computations, preferable correction results, and rapid convergence rate.

• Journal of the Optical Society of Korea
• /
• 제11권1호
• /
• pp.1-5
• /
• 2007

We investigate the efficiency of an optical intensity modulator based on an electrically tunable $LiNbO_3$ reflection grating. Assuming a grating coupling coefficient and the waveguide propagation loss, waveguide length is varied to find its effect on the modulator slope efficiency and the device capacitance. With the low propagation loss of the $LiNbO_3$ waveguide, a very efficient optical intensity modulator can be achieved for a low frequency (${\sim}1GHz$) as long as the requirement for the grating coupling coefficient is satisfied.