• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.171-171
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• 1999

We studied the charge redistribution in the Pt-M (M=Cu, Co) alloys by X-ray Absorption Near Edge Spectroscopy(XANES) and X-ray Photoelectron Spectroscopy(XPS). These analysis tools provide us information about the charge transfer in the valence band of intermetallic bonding. The samples were prepared by arc-melting method. After annealing this samples in vacuum for several hours, we cold get the ordered samples, which were confirmed with XRD analysis. the core and valence level energy shift in these system were investigated by Mg $K\alpha$(1253.6eV) x-ray source for Pt-Co alloys and monochromatized Al $K\alpha$ (1486.6eV) for Pt-Cu alloys. Pt L2, L3-edge, and Cu, Co K-edge XANES spectra were measured with the total electron-yield mode detector at the 3Cl beam line of the PLS (Pohang light source0. from the changes of White line (WL) area and the core level shifts of the each metal sites, we can obtain the information about the electrons participating in the intermetallic bonding of the Pt-Cu and Pt-Co alloys.

• Journal of the Optical Society of Korea
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• v.10 no.3
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• pp.105-111
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• 2006

A novel image quality evaluation method, which is based on combination of the rigorous grating diffraction theory and the ray-optic method, is proposed. It is applied for design optimization and, tolerance analysis of optical imaging systems implementing diffractive optical elements (DOE). The evaluation method can predict the quality and resolution of the image on the image sensor plane through the optical imaging system. Especially, we can simulate the effect of diffraction efficiencies of DOE in the camera lenses module, which is very effective for predicting different color sense and MTF performance. Using this method, we can effectively determine the fabrication tolerances of diffractive and refractive optical elements such as the variations' in profile thickness, and the shoulder of the DOE, as well as conventional parameters such as decenter and tilt in optical-surface alignments. A DOE-based 2M-resolution camera lens module designed by the optimization process based on the proposed image quality evaluation method shows ${\sim}15%$ MTF improvement compared with a design without such an optimization.

• Journal of Korea Game Society
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• v.18 no.1
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• pp.125-134
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• 2018

This paper presents a practical method to efficiently extract the rotational part of a $3{\times}3$ matrix that changes continuously in time. This is the key technique in the corotational FEM and the shape matching deformation popular in physics-based dynamic deformation. Recently, in contrast to the traditional polar decomposition methods independent of time, an iterative method was proposed that formulates the rotation extraction in a physics-based way and exploits an incremental representation of rotation. We develop an optimization method that reduces the number of iterations under the assumption that the maximum magnitude of the incremental rotation vector is limited within ${\pi}/2$. Realistic simulation of dynamic deformation employs a sufficiently small time step, and thus this assumption is not problematic in practice. We demonstrate the efficiency and practicality of our method in various experiments.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.216-221
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• 2024

Ion cyclotron range of frequency (ICRF) heating system is an important auxiliary heating method in the experimental Advanced Superconducting Tokamak (EAST). In EAST, several megawatts of power are transmitted with coaxial transmission lines and coupled to the plasma. For the long pulse and high power operation of the ICRF waves heating system, it is very important to effectively control the power and initial phase of the ICRF signals. In this paper, a power and phase feedback control system is described based on field programmable gate array (FPGA) devices, which can realize complicated algorithms with the advantages of fast running and high reliability. The transmitted power and antenna phase are measured by a power and phase detector and digitized. The power and phase feedback control algorithms is designed to achieve the target power and antenna phase. The power feedback control system was tested on a dummy load and during plasma experiments. Test results confirm that the feedback control system can precisely control ICRF power and antenna phase and is robust during plasma variations.

• Proceedings of the KOSOMBE Conference
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• v.1994 no.12
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• pp.124-127
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• 1994

A technique based on bispectrun averaging is described for generally recovering the signal waveform from a set of noisy signals with variable signal delay. The technique does not require explicit tune alignment of signals and any initial estimate of signal. The new method is suggested and is compared with other methods. This method are numerically investigated using computer generated-data and a physiological signal and noise Some experimental results for the evoked potential studios that demonstrate the technique are given. The results show the effectiveness of the technique: various potential applications of the technique might be expected.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.6
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• pp.2497-2517
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• 2020

For compressed sensing (CS) applications, it is significant to construct deterministic measurement matrices with good practical features, including good sensing performance, low memory cost, low computational complexity and easy hardware implementation. In this paper, a deterministic construction method of bipolar measurement matrices is presented based on binary sequence family (BSF). This method is of interest to be applied for sparse signal restore and image block CS. Coherence is an important tool to describe and compare the performance of various sensing matrices. Lower coherence implies higher reconstruction accuracy. The coherence of proposed measurement matrices is analyzed and derived to be smaller than the corresponding Gaussian and Bernoulli random matrices. Simulation experiments show that the proposed matrices outperform the corresponding Gaussian, Bernoulli, binary and chaotic bipolar matrices in reconstruction accuracy. Meanwhile, the proposed matrices can reduce the reconstruction time compared with their Gaussian counterpart. Moreover, the proposed matrices are very efficient for sensing performance, memory, complexity and hardware realization, which is beneficial to practical CS.

• Journal of the Optical Society of Korea
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• v.3 no.1
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• pp.23-26
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• 1999

A simple technique to measure electro-optic coefficients has been developed. It is based on rotating analyzer polarimetry. With a coaxial configuration of the optically active polarizing devices, the synchronously digitized signals are Fourier analyzed to quantitatively determine the elliptical polarization of light and, hence, the electric field induced birefringence. This technique has the advantage that it does not require waveguiding, and since it is improved from the crossed polarizer method it measures the phase retardation directly. It has been applied for the precise determination of electro-optic coefficients of uniaxial LiNbO3 single crystals. The excellent agreeement with reported values confirms its usefulness toward accurate characterization of electro-optic coefficients of unknown specimens.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.05
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• pp.235-239
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• 1996

In recent years, the optical properties of multiple-scattering media like tissue have been studied for their potential applications in medicine. In this work the optical properties of multiple scattering media were investigated using the time-resolved reflectance measurement. The reflected light was measured by time-correlated single photon counting system. The transport scattering and absorption coefficient are related to the initial rapid decay and the subsequent decay in reflected light, respectively. Also the optical properties of the samples were measured by conventional method, ie., using continuous wave light. When the distance between the light source and the detector is over 8mm, the optical coefficient can be measured accurately using the suggested method.

• Journal of the Korean Society of Visualization
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• v.21 no.1
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• pp.119-126
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• 2023

Acquiring experimental data for PIV verification or machine learning training data is resource-demanding, leading to an increasing interest in synthetic particle images as simulation data. Conventional synthetic particle image generation algorithms do not follow physical laws, and the use of CFD is time-consuming and requires computing resources. In this study, we propose a new method for synthetic particle image generation, based on a Physics-Informed Neural Networks(PINN). The PINN is utilized to infer the flow fields, enabling the generation of synthetic particle images that follow physical laws with reduced computation time and have no constraints on spatial resolution compared to CFD. The proposed method is expected to contribute to the verification of PIV algorithms.

• Current Optics and Photonics
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• v.1 no.2
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• pp.143-149
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• 2017

LED arrays with pixel numbers of $3{\times}3$, $4{\times}4$, and $5{\times}5$ have been studied in this paper in order to enhance the optical output power and decrease heat dissipation of an AlGaInP-based light emitting diode display device (pixel size of $280{\times}280{\mu}m$) fabricated by micro-opto-electro-mechanical systems. Simulation results showed that the thermal resistances of the $3{\times}3$, $4{\times}4$, $5{\times}5$ arrays were $52^{\circ}C/W$, $69.7^{\circ}C/W$, and $84.3^{\circ}C/W$. The junction temperature was calculated by the peak wavelength shift method, which showed that the maximum value appears at the center pixel due to thermal crosstalk from neighboring pixels. The central temperature would be minimized with $40{\mu}m$ pixel pitch and $150{\mu}m$ substrate thickness as calculated by thermal modeling using finite element analysis. The modeling can be used to optimize parameters of highly integrated AlGaInP-based LED arrays fabricated by micro-opto-electro-mechanical systems technology.