• Nuclear Engineering and Technology
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• v.52 no.11
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• pp.2594-2600
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• 2020

A gamma camera system using radionuclide has a functional imaging technique and is frequently used in the field of nuclear medicine. In the gamma camera, it is extremely important to improve the image quality to ensure accurate detection of diseases. In this study, we designed a blind-deconvolution framework after a noise-reduction algorithm based on a non-local mean, which has been shown to outperform conventional methodologies with regard to the gamma camera system. For this purpose, we performed a simulation using the Monte Carlo method and conducted an experiment. The image performance was evaluated by visual assessment and according to the intensity profile, and a quantitative evaluation using a normalized noise-power spectrum was performed on the acquired image and the blind-deconvolution image after noise reduction. The result indicates an improvement in image performance for gamma camera images when our proposed algorithm is used.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.1
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• pp.8-14
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• 2004

As the number of offshore structure is glowing in deep waters, there have been increased damages of it. These floating structures in offshore locations exposed to harsh environmental conditions. In recent years, there has been a slowing attention around damages on bow and deck on FPSO caused by waves in steep storm condition. This paper describes a study of the water on deck due to the dynamic behavior of a FPSO with turret mooring system. The nonlinear motions of the FPSO are simulated under external forces due to wave, current, wind, and mooring forces in the time domain. The direct integration method is employed to estimate low frequency drift wave forces. The current forces are calculated by using slow motion maneuvering equations in the horizontal plane. The coefficients of a model for wind forces are calculated from Isherwood's experimental data and the variation of wind speed is estimated by wind spectrum according to the guidelines of API-RP2A.

• Journal of electromagnetic engineering and science
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• v.13 no.2
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• pp.63-72
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• 2013

The ultra-wideband (UWB) spectrum available for commercial applications has offered us an opportunity to achieve high-speed wireless communications and high-accuracy location applications. As one of key research areas in UWB technology, a lot of innovative broadband and miniaturization techniques for UWB antennas have been greatly invented and developed for years. This paper reviews the development of UWB antenna design in the past decade. Starting with a brief introduction of the specific requirements and promising applications of UWB systems, the unique design challenges of UWB antennas are highlighted. Next, the important milestones of UWB antenna designs are briefed. After that, a variety of planar UWB antennas invented for broadband operation, miniaturization, and multiple functions are introduced. Last, the comments on the development of UWB antennas in future are shared.

• Bulletin of the Korean Chemical Society
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• v.25 no.12
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• pp.1757-1763
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• 2004

A new series of nickel(II), cobalt(II)/(III) and copper(II) complexes of 14, 15 and 16-membered of macrocyclic ligands have been prepared and characterized by elemental analyses, IR, UV-VIS and $^1H-NMR$ spectra, magnetic susceptibilities, conductivities, DTA and ESR measurements. Molar conductances in DMF solution indicate that, the complexes are nonelectrolytes except (9-12) complexes. The electronic spectra show that, all complexes are square planar or distorted octahedral geometry. The ESR spectra of solid complexes (4), (8) and (11) show square planar of axial type symmetry $(d_{x2-y2})$ with considerable covalent bond character. However, complex (12) shows a spectrum of octahedral geometry with $d_{z2}$ ground state. Complex (12) shows exploitation in reducing the amount of electron adducts formed in DNA during irradiation with low radiation products.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.9
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• pp.1517-1523
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• 2003

Deep X-ray lithography (DXRL), a fabrication method for the production of microstructures with a high aspect ratio, plays an important role in the subsequent electroplanting process. However, secondary radiation is generated during X-ray exposure and damages the resist adhesion to the metal layer. To solve adhesion problems, we modified the conventional DXRL process, changing the sequence of polymer adhesion in DXRL process. With optimized X-ray exposure and development conditions based on a calculated and modified X-ray power spectrum, we fabricated various polymer microstructures and achieved a maximum aspect ratio of 40.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.6
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• pp.111-117
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• 2002

The high quality and a nearly stoichometric growth of $Cd_{1-y} Zn_y$/Te(y＝0.04) epilayers have been successfully grown on GaAs substrate by hot wall epitaxy (HWE) by optimizing the growth condition including the preheating treatment and Cd reservoir temperature. The relationship between quality and thickness was examined and best value of FWHM from X-ray rocking curve of 121 arcsec are obtained. Also, emission peaks related to the recombination of free excitons such as the ground state and the first excited state were observed in the PL spectrum at 4.2K. The ($A^0$, X) emission related to Cd vacancy and deep level emission was not measured. These results indicated that the grown CZT/GaAs epilayer was high qualify and purity.

• Journal of the Optical Society of Korea
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• v.18 no.1
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• pp.15-22
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• 2014

We present a novel bandwidth measurement scheme for multimode optical fibers. Amplified spontaneous emission (ASE) radiation was utilized for a source of intrinsically modulated light with a wide modulation bandwidth. In our measurement scheme, the continuous-wave (CW) ASE light that passed through a multimode fiber (MMF) under test was analyzed by the fourth-order power with a high-speed photodetector and an electric spectrum analyzer. The modulation transfer function of the multimode fiber could be directly measured with the photoelectric spectra in the modulation frequency domain. The measurement result of our method was experimentally compared to that of the conventional measurement scheme based on the impulse response measurement. It has been found that our scheme provides a stable measurement means of MMF characterization that is suitable for the field testing due to the simplicity of the system.

• Journal of the Korean Institute of Telematics and Electronics
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• v.3 no.3
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• pp.14-21
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• 1966

In this article, a recording system for nuclear radiation detection by means of circular radial deflection as an instrument and its applications are described. In the electronic circuit of the instrument, the linearity of a deflected pulse on a circular sweep is especially contribed by employing a multiplying circuit, not to mention the one of a circular time base itself. A sequence of random pulses was recorded on a circular sweep of the CRT screen by means of one cycle unblanking due to a logic circuit. It seems that the intrument is suitable for measuring a decay curve of a short-lived nuclide and its pulse spectrum

• Journal of The Korean Astronomical Society
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• v.28 no.2
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• pp.109-117
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• 1995

The morphology and strength of the primordial magnetic field which is generated spontaneously in the early universe are studied for three models: (1) inflation (2) primordial magnetized bubble and (3) primordial turbulence models, We calculate the power spectra of magnetic field that are scale-free and proportional to $k^{1.5},k^{3{\sim}4}$ and $k^{2/3}$, respectively. The configurations of magnetic field having these power spectra are visualized. To constrain the present strength of the primordial magnetic field we calculate the anisotropy of the microwave background radiation in Bianchi type I universe with globally homogeneous magnetic field. From the COBE limit of the quadrupole moment of $({\delta}T/T)_{l=2}$ the present strength of horizen-scale magnetic fields $B_p$ is constrained to be less than $9{\times}10^{-8}G$.

• Publications of The Korean Astronomical Society
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• v.11 no.1
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• pp.221-229
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• 1996

We have developed a measurement system with which harmful radio noise can be detected. It was designed to cover 1GHz band width centered at l.5GHz and 22.2GHz ($H_2O$ line).The system consists of pyramid horn antennas, receivers, equatorial tracking system, spectrum analyzer, and PC for the control of the servo and data taking. As a test of the system, the site of Taeduk Radio Astronomy Observatory (TRAO) was investigated to see if there is any harmful radio interference. It is found that in 22GHz band there is no significant radio noise, but there are identified and unidentified artificial radio signals in 1-2GHz range. However a simple calculation of radiation power shows that it is week enough not to affect the observations in TRAO.