• Applied Microscopy
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• v.41 no.2
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• pp.81-88
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• 2011

Even though importance of nano-scale structure and compositional analysis have been getting increased, existing analysis tools have been reached to their limitations. Recent development of Atom Probe Tomography (APT), providing 3-dimensional elemental distribution and compositional information with sub-nm scale special resolution and tens of ppm detection limit, is one of key technique which can overcome these limitations. However, due to the fact that APT is not well known yet in the domestic research area, it has been rarely utilized so far. Therefore, in this article, the theoretical background of APT was briefly introduced with sample preparation to help understanding APT analysis.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.12
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• pp.1070-1074
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• 2002

We have carried out two-beam interference experiments to form holographic gratings on As$_{40}$ Se$_{15}$ S$_{35}$Ge$_{10}$ single layer, Ag/As$_{40}$ Se$_{15}$ S$_{35}$Ge$_{10}$ multi-layer. In this study, holographic gratings have been formed using He-Ne laser(632.8nm) under different polarization combinations(intensity polarization holography, phase polarization holography). The diffraction efficiency was obtained by the +lst order intensity. The maximum diffraction efficiency of As$_{40}$ Se$_{15}$ S$_{35}$Ge$_{10}$ single layer, As$_{40}$ Se$_{15}$ S$_{35}$Ge$_{10}$ and MgF$_2$/As$_{40}$ Se$_{15}$ S$_{35}$Ge$_{10}$ multi-layer were 0.8%, 1.4% and 3.1% under intensity polarization holography, respectively.

• Transactions on Electrical and Electronic Materials
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• v.8 no.6
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• pp.250-254
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• 2007

Applying the moving photo-carrier grating(MPG) technique and time-of-flight(TOF) measurements, we studied the transport properties of stabilized amorphous selenium typical of the material used in direct conversion X-ray imaging devices. For MPG measurement, we obtained electron and hole mobility and the recombination lifetime of $\alpha-Se$ films with arsenic(As) additions. We found an apparent increase in hole drift mobility and recombination lifetime, especially when 0.3 % As was added into $\alpha-Se$ film, whereas electron mobility decreased with the addition of As due to the defect density. For TOF measurement, a laser beam with pulse duration of 5 ns and wavelength of 350 nm was illuminated on the surface of $\alpha-Se$ with a thickness of 400 ${\mu}m$. The measured hole and electron transit times were about 8.73 ${\mu}s$ and 229.17 ${\mu}s$, respectively.

• Journal of ILASS-Korea
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• v.7 no.2
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• pp.7-15
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• 2002

A particle flow visualization, electrostatic charging measurement and separation of triboelectrically charged particles in the external electric field by a fluidized bed tribocharger are conducted for the removal of PVC particles from mixed waste plastics. The laboratory-scale triboelectrostatic separation system consists of the fluidized bed tribocharger, a separation chamber, a collection chamber and a controller. PVC and PET particles can be imparted negative and positive surface charges respectively due to the difference of triboelectric charging series between particles and particles in the fluidized bed tribocharger, and can be separated by passing them through an external electric field. To visualize these charged particles, He-Ne laser is used with cylindrical lenses to generate a sheet beam. In the charging measurement, the particle motion analysis system (PMAS), capable of determining particle velocity and diameter. is used to non-intrusively measure particle behavior in high strength electric field. The average charge-to-mass ratios of PVC and PET particles are $1.4\;and\;1.2{\mu}C/kg$, respectively. The highly concentrated PVC (91.9%) can be recovered with a yield of about 96.1% from the mixture of PVC and PET materials for a single-stage processing. The triboelectrostatic separation system using the fluidized tribocharger shows the potential to be an effective method for removing PVC from mixed plastics for waste plastic recycling.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.4
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• pp.22-25
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• 2008

The dynamic response of the head arm assembly (HAA) of a hard disk drive to an impact load was obtained from a 3D non-linear finite element model using ANSYS/LS-DYNA and from experiments using a modified levitation mass method (LMM). In the finite element model, the impact load was created by modeling the mass as a rigid body and making it collide with the HAA. The velocity, displacement, acceleration, and inertial force of the mass were then obtained from the time history data of the finite element analysis. In the LMM, a mass that was levitated with an aerostatic linear bearing, and hence encountered negligible friction, was made to collide with the actuator arm, resulting in a dynamic bending test for the arm. During the collision, the Doppler frequency shift of the laser beam reflected from the mass was accurately measured with an optical interferometer. The velocity, displacement, acceleration, and inertial force of the mass were accurately calculated from the measured time-varying Doppler frequency shift. A good correlation between the experimental data and FEA results was observed. The FEA was also used to investigate the dynamic response of the HAA to impact by different masses.

• Journal of the Optical Society of Korea
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• v.13 no.4
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• pp.468-471
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• 2009

We propose a simple nondestructive method to obtain refractive-index profiles of a graded-index (GRIN) light-focusing rod by means of a diffraction grating. In our proposed method, a laser beam is illuminated through a diffraction grating perpendicular to the axis of the GRIN lens and the separation between the zeroth and first-order diffraction peaks is measured and analyzed. The results demonstrate that the refractive-index profiles of commercially available GRIN lenses can be successfully reconstructed.

• Korean Journal of Optics and Photonics
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• v.12 no.4
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• pp.300-304
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• 2001

We suggest a method to measure and correct bending deformation in piezoelectric ceramics displacement. The angle and direction of the bending deformation are measured by monitoring the position of a laser beam reflected on a mirror which is attached to the piezoelectric ceramics with the uncertainty of the angle measurement of $0.36\mu$rad. We divided the electrode of a piezoelectric ceramic into 3 parts and connected 3 capacitors to each electrode in order to apply different voltage to each electrode with one voltage supplier. The deformation was corrected by adjusting the capacitance of each capacitor and was reduced to 6.3%, comparing to the uncorrected case. By using this corrected piezoelectric ceramic to modulate the length of the ringdown cavity, the fluctuation of the decay time caused by the change in optic axis of the cavity was removed.emoved.

• Korean Journal of Optics and Photonics
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• v.18 no.1
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• pp.44-49
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• 2007

We have transferred a narrow-linewidth $1.5{\mu}m$ laser beam through a 525 m fiber network with excellent transfer stability. The fiber-induced optical phase noise during the fiber transmission is cancelled by configuring a noise-canceling servo. The transfer instability was $2{\times}10^{-17}$ at 1 s of averaging time. We quantitatively analyzed the transferred optical frequency in the frequency domain and in the time domain.

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.605-610
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• 2014

Clouds play an important role in climate change, in the prediction of local weather, and also in aviation safety when instrument assisted flying is unavailable. Presently, various ground-based instruments used for the measurements of the cloud base height or velocity. Lidar techniques are powerful and have many applications in climate studies, including the clouds' temperature measurement, the aerosol particle properties, etc. Otherwise, it is very circumscribed in cloud velocity measurements because there is no Doppler effect if the clouds move in the perpendicular direction to the laser beam path of Doppler lidar. In this paper, we present a method for the measurement of cloud velocity using lidar's range detection and DIC (Digital Image Correlation) system to overcome the disadvantage of Doppler lidar. The lidar system acquires the distance to the cloud, and the cloud images are tracked using the developed fast correlation algorithm of DIC. We acquired the velocities of clouds using the calculated distance and DIC algorithm. The measurement values had a linear distribution.

• Journal of Magnetics
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• v.2 no.4
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• pp.147-156
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• 1997

An artificially modulated magnetic Co/Pd multilayer is one of the promising candidates for high density magneto-optic (MO) recording media, due to a large Kerr rotation angle in the wavelength of a blue laser beam. However, since multilayer structure, as well as amorphous structure, is a non-equilibrium state in terms of free energy and a MO recording technology is a kind of thermal recording which is conducted around Curie temperature (Tc) of the recording media, when the Co/Pd mulilayer is used for the MO recording media, changes in the magnetic properties are occurred as the amorphous structure do. Therefore, the assessment of the magnetic properties in the Co/Pd multilayer during interdiffusion is crucially important both for basic research and applications. As the parameter of the magnetic properties in this research, saturation magnetization and perpendicular magnetic anisotropy energy of the Co/Pd multilayer are measured in terms of Ar sputtering pressure and heat treatment temperature. Form the results of the research, we find out that the magnetic exchange energy between Co and Pd sublayers strongly affects the changes in the magnetic properties of the Co/Pd multilayers during the interdiffusion in ferromagnetic state. This discovery will provide the understanding of the magnetic exchange energy in the Co/Pd multilayer structure and suggest the operating temperature range for MO recording in the Co/Pd multilayer for the basic research and applications, respectively.