• Composites Research
• /
• v.31 no.5
• /
• pp.246-250
• /
• 2018

In this paper, laser ultrasonic rotation scanning method was proposed to inspect and visualize defects in corner section of curved composite structure. L-shaped composite specimen with defects in its corner section were inspected using laser ultrasonic rotation scanning method. L-shaped specimens had artificial defects at three different depths to simulate delamination damage. All artificial defects were detected clearly in different time-of-flight according to their depths. Inspection result showed that the proposed method is suitable to inspect round corner section of curved composite structure without any special tools.

• Journal of Institute of Control, Robotics and Systems
• /
• v.13 no.3
• /
• pp.249-255
• /
• 2007

Under the situation of a fire, it is difficult for a rescue robot to use sensors such as vision sensor, ultrasonic sensor or laser distance sensor because of diffusion, refraction or block of light and sound by dense smoke. But, braille blocks that are installed for the visaully impaired at public places such as subway stations can be used as a map for autonomous mobile robot's localization and navigation. In this paper, we developed a laser sensor stan device which can detect braille blcoks in spite of dense smoke and integrated the device to the robot developed to carry out rescue mission in various hazardous disaster areas at KIST. We implemented MCL algorithm for robot's attitude estimation according to the scanned data and transformed a braille block map to a topological map and designed a nonlinear path tracking controller for autonomous navigation. From various simulations and experiments, we could verify that the developed laser sensor device and the proposed localization method are effective to autonomous tracking of braille blocks and the autonomous navigation robot system can be used for rescue under fire.

• Journal of the Korean Society for Precision Engineering
• /
• v.29 no.3
• /
• pp.334-338
• /
• 2012

Electrical isolation of Ag nanowire, which is one of the candidates as electrode for display devices, on polymer with femtosecond pulse laser has been investigated. Line patterning to Ag nanowire with various pulse energy and scan speed were experimented. Duo to the results of the line patterning experiment, we fabricated the isolated squares and measured electrical resistance. The profile of the selectively ablated area was analyzed with AFM(Atomic Force Microscope). The width of the patterned line was $1.8\;{\mu}m$ and the depth was $1.6\;{\mu}m$. We demonstrated electrical isolation of the Ag nanowire using femtosecond laser by evaluating the electrical resistance of the sample between isolated and opened area.

• Nuclear Engineering and Technology
• /
• v.46 no.4
• /
• pp.521-528
• /
• 2014

The surface modification of engineering materials by laser beam scanning (LBS) allows the improvement of properties in terms of reduced wear, increased corrosion resistance, and better strength. In this study, the laser beam scan method was applied to produce an oxide dispersion strengthened (ODS) structure on a zirconium metal surface. A recrystallized Zircaloy-4 alloy sheet with a thickness of 2 mm, and $Y_2O_3$ particles of $10{\mu}m$ were selected for ODS treatment using LBS. Through the LBS method, the $Y_2O_3$ particles were dispersed in the Zircaloy-4 sheet surface at a thickness of 0.4 mm, which was about 20% when compared to the initial sheet thickness. The mean size of the dispersive particles was 20 nm, and the yield strength of the ODS treated plate at $500^{\circ}C$ was increased more than 65 % when compared to the initial state. This strength increase was caused by dispersive $Y_2O_3$ particles in the matrix and the martensite transformation of Zircaloy-4 matrix by the LBS.

• Journal of Institute of Control, Robotics and Systems
• /
• v.11 no.5
• /
• pp.406-410
• /
• 2005

A depth measurement system that consists of a single camera, a laser light source and a rotating mirror is investigated. The camera and the light source are fixed, facing the rotating mirror. The laser light is reflected by the mirror and projected to the scene objects whose locations are to be determined. The camera detects the laser light location on object surfaces through the same mirror. The scan over the area to be measured is done by mirror rotation. Advantages are 1) the image of the light stripe remains sharp while that of the background becomes blurred because of the mirror rotation and 2) the only rotating part of this system is the mirror but the mirror angle is not involved in depth computation. This minimizes the imprecision caused by a possible inaccurate angle measurement. The detail arrangement and experimental results are reported.

• The Journal of Natural Sciences
• /
• v.7
• /
• pp.11-17
• /
• 1995

The optical nonlinear refractive index of $Bil_3$ semiconductor microcluster colloid has been measured by the Z-scan method with circular symmetric beam. The value of nonlinear refractive index was -1.53 x $10^12($cm^2/W) at $0.532\mum$and the nonlinearities were mainly due to thermal effect induced by 20 ns laser pulse. And the absorption coefficient was measured to be -$10^8$(cm/W)

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2003.10a
• /
• pp.39-42
• /
• 2003

In order to Impose an effective check on the existing methode of measurement, this study make an attempt to attach sensor on a structure, which can perceive a laser beam sent out from a light source at any place. This system makes it possible to measure an absolute of dynamic displacement according to accurately survey an amount of fluctuation in process of time. This result of experiment to compare the products by means of each method was satisfactory for identification. Accordingly these facts attest to the possibility of accurate measurement owing to gauge an dynamic displacement amount of structure.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2004.08a
• /
• pp.153-156
• /
• 2004

A newly developed flexible active-matrix (AM-) electrophoretic display (EPD) is reported. The AM-EPD features: (1) low-temperature polycrystalline silicon (LTPS) thin film transistor (TFT) technology, (2) fully integrated scan- and data-drivers, (3) flexibility and light-weight realized by transferring the whole circuits onto a plastic substrate using $SUFTLA^{TM}$ (Surface Free Technology by Laser Annealing/Ablation) process. A large storage capacitor is formed in each pixel so that driving electric field can be kept sufficiently strong during a writing period Two-phase driving scheme, a reset-phase which erases a previous image and a writing-phase for writing a new image, was chosen to cope with EPD's high driving voltage. The flexible AM-EPD has been successfully operated with a driving voltage of 8.5 V.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.32 no.3
• /
• pp.274-279
• /
• 2008

Roll to roll (R2R) manufacturing process, also known as 'web processing', has been tried for producing electronic devices on a flexible plastic or metal foil. To increase the performance and productivity the R2R process, effective control and on-line supervision for web quality becomes very important. Wrinkle is one of the defects, which is incurred due to compressive stresses. A system for on-line measurement of wrinkle is developed using area scan camera and machine vision laser. The 2D image, obtained by area scan camera, is produced by Gaussian regression method to characterize the wrinkle on a transparent web. The experiment proves that 0.3mm wrinkle height can be measured successfully with 74fps.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.05a
• /
• pp.241-246
• /
• 2002

Usually vibration properties are obtained from frequency response functions or impulse response functions of a system. Since the contact type sensors can affect the characteristics of vibrating systems, the non-contact type sensors such as laser Doppler vibrometer (LDV) are being widely used. Currently researches are being carried out in terms of modal analysis using a scanning vibrometer. For the continuous scan; the Chebyshev demodulation (or polynomial) is apparently suggested to extract the mode shapes. With single frequency sinusoidal excitation, this approach is well fitted. In this research, the Chebyshev demodulation technique has been applied to the impact excitation case. The vibration of the tested structure is modeled using impulse response functions. The technique is also adopted to the random excitation case. In order to verify the technique, a simply supported beam was chosen as the test rig. The calculation modules are developed by using MATLAB$\^$(R)/ in WindowsNT$\^$(R)/ environment.