• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.168-168
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• 2004

본 논문은 헤테로다인 간섭계를 이용한 레이저 진동 측정기에 대해 기술하고 있다. 상용 레이저 진동 측정기가 대부분 AOM을 이용하여 주파수 천이를 일으키는 반면, 본 연구에서는 Zeeman 안정화 He-Ne 레이저를 사용하므로써, 서로 다른 주파수를 가지는 레이저를 동시에 얻을 수 있었다. 따라서, Zeeman 안정화 He-Ne 레이저를 사용하는 진동측정기의 경우 간섭계 구성을 위해 사용되는 비용을 현저히 줄일 수 있다. 또한, AOM의 고주파 신호를 처리하기 위해서는 RE 대역의 신호처리 회로 설계가 필요하지만, Zeeman 안정화 레이저의 주파수 천이가 낮으므로, 제안된 진동측정기의 신호처리가 용이하다.(중략)

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2562-2564
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• 2002

This paper presents an auxiliary beam-assisted adaptive compensation technique applied to alleviate the problem of LDV's body vibration. The LMS algorithm is applied to adaptively compensate the body vibration utilizing the reference signal provided by the auxiliary beam. The usefulness of the proposed technique is verified via computer simulations performed for diverse types of target signals and body vibration.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.4
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• pp.81-89
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• 1996

In the present study, the unsteady in a square-selctional 180.deg. curved duct are experimentally investigated. The experimental study using air in a square-sectional 180.deg. curved duct is carried out to measure axial velocity distributions with data acquisition and processing system. In this system, Rotating Machinery Resolver(RMR) and PHASE Software are used to obtain the results of unsteady flows. In conclusion, the exact measurement of unsteady flow using LDV system depends upon uniformity of metreials, duct thickness, and scattered particles.

• Bulletin of the Korean Chemical Society
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• v.16 no.3
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• pp.256-260
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• 1995

Laser induced fluorescence spectra of OH produced from photodissociation of $H_2O_2$ at 280-290 nm in the gas phase have been observed. By analyzing the Doppler profiles, the anisotropy parameter($\beta$ =-0.7) and the center of mass translational energy of the fragments have been measured. The measured energy distribution is well described by an impulsive model. The excited state leading to dissociation is found to be of 1Au symmetry. The dissociation from this state is prompt and direct with the fragment OH rotating in the plane perpendicular to the O-O bond axis.

• Smart Structures and Systems
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• v.26 no.5
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• pp.657-666
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• 2020

A rotational pulse-echo ultrasonic propagation imager that can inspect cylindrical specimens for material nondestructive evaluations is proposed herein. In this system, a laser-generated ultrasonic bulk wave is used for inspection, which enables a clear visualization of subsurface defects with a precise reproduction of the damage shape and size. The ultrasonic waves are generated by a Q-switched laser that impinges on the outer surface of the specimen walls. The generated waves travel through the walls and their echo is detected by a Laser Doppler Vibrometer (LDV) at the same point. To obtain the optimal Signal-to-Noise Ratio (SNR) of the measured signal, the LDV requires the sensed surface to be at a right angle to the laser beam and at a predefined constant standoff distance from the laser head. For flat specimens, these constraints can be easily satisfied by performing a raster scan using a dual-axis linear stage. However, this arrangement cannot be used for cylindrical specimens owing to their curved nature. To inspect the cylindrical specimens, a circular scan technology is newly proposed for pulse-echo laser ultrasound. A rotational stage is coupled with a single-axis linear stage to inspect the desired area of the specimen. This system arrangement ensures that the standoff distance and beam incidence angle are maintained while the cylindrical specimen is being inspected. This enables the inspection of a curved specimen while maintaining the optimal SNR. The measurement result is displayed in parallel with the on-going inspection. The inspection data used in scanning are mapped from rotational coordinates to linear coordinates for visualization and post-processing of results. A graphical user interface software is implemented in C++ using a QT framework and controls all the individual blocks of the system and implements the necessary image processing, scan calculations, data acquisition, signal processing and result visualization.

• Journal of ILASS-Korea
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• v.11 no.2
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• pp.81-88
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• 2006

The spray characteristics of the rotating fuel injection system were investigated. The special test rig was devised to get the spatial and momentary droplet information. This experimental apparatus consists of a high-speed motor, a shaft, a rotating fuel nozzle and an acrylic case. Spray droplet size and velocity were measured by PDPA(Phase Doppler Particle Analyzer) and instantaneous velocity field was measured by 1'IV (Particle Image Velocimetry) system. At the same time, spray visualization was performed by using ND-YAG laser-based flash photography. From these two different laser diagnostic techniques, we could get spatial and instantaneous spray information fur rotating fuel injection system. The results presented in this paper indicate that spray characteristics such as droplet size, velocity and spray pattern were strongly influenced by rotational speed.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.539-544
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• 2001

The holographic measurement techniques can be applied to various industrial fields such as automobile, airplane, construction, electronics, medical, mechanics and physics. The visualization of fluids is very important in aerodynamics, heat transfer and stress analysis. There are classically optical methods such as shadowgraph, schlieren method, and Mach-Zehnder interferometry for visualizing the fluid flow phenomena. But, it is difficult to understand the continuous state of fluids well in those methods. In this study, the real-time holographic interferometer with high-speed camera is applied to the flow visualization. In addition, collimated laser beam and rotating wedge are used for recording and formation of carrier fringes, respectively.

• Journal of Power System Engineering
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• v.13 no.1
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• pp.33-38
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• 2009

In this study, the nose of cam in the automobile engine was modelled into circular disk to analyze the torsional vibration of the cam shaft. The distance between disks was fixed, but the diameter of disks was changed. The torsional vibration of the cam shaft was studied experimentally by the motion of the modelled disk with changing the disk diameter. And the sizes of the modelled disk were selected not to show the natural frequencies over all the experimental ranges. The torsional vibration meter used in this study has a laser system with non-contact measurement method, which can measure both torsional angular vibration velocity and torsional angular vibration displacement simultaneously. The Experimental analysis shows that the characteristics of the torsional vibration in the horizontal rotating shaft can be considerably affected by the arrangement of the modelled disks.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.6
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• pp.272-277
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• 2002

This paper deals with the vibration deflection shape measurement technique for a sinusoidally excited structure using a continuously scanning laser Doppler vibrometer (CSLV). The CSLV output signal is an amplitude-modulated vibration in which the excitation signal is modulated by the deflection shapes, and thus the deflection shapes of vibration defined along a scan line can be derived by the envelop and the phase information of the CSLV output signal. In this work, a Hilbert transform based approach has been proposed for measurement of deflection shapes. This technique is as simple as the demodulation technique and allows more convenient experimental settings than the Fourier transform approach. The feasibility of the proposed technique is illustrated along with results of experiment.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.501-506
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• 1997

This paper presents the hydraulic characteristics measured by using LDV(Laser Doppler Velocimetry) in subchannels of a HANARO, KAERI research reactor, fuel bundle. The fuel bundle consists of 18 axially finned rods with 3 spacer grids, which are arranged in cylindrical configuration. The effects of the spacer grids on the turbulent flow were investigated by the experimental results. Pressure drops fer each component of the fuel bundle were measured, and the friction factors of fuel bundle and loss coefficients for the spacer grids were estimated from the measured pressure drops. Implications regard ins the turbulent thermal mixing were discussed. Vibration test results measured by using laser vibrometer were presented.