• Korean Journal of Materials Research
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• v.2 no.3
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• pp.228-238
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• 1992

An investigation on the step-coverage of PECVD and $O_3$ ThCVD oxides was undertaken to implement into the void-free inter metal dielectric planarization using multi-chamber system for the submicron double level metallization. At various initial aspect ratios the instantaneous aspect ratios were measured through modelling and experiment by depositing the oxides up to $0.9{\mu}m$ in thickness in order to monitor the onset of void formation. The modelling was found to be in a good agreement with the observed instantaneous aspect ratio of TEOS-based PECVD oxide whose re-entrant angle was less than $5^{\circ}$. It is demonstrated that either keeping the instantaneous aspect ratio of PECVD oxide as a first layer less than a factor of 0.8 or employing Ar sputter etch to create sloped oxide edge ensures the void-free planarization after$O_3$ ThCVD oxide deposition whose step-coverage is superior to PECVD oxide. It has been observed that $O_3$ ThCVD oxide etchback scheme has shown higher yield of via contact chain than non etchback process, with resistance per via contact of $0.1~0.3{\Omega}/{\mu}m^2$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.4
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• pp.60-70
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• 2000

An 8$\times$8+20-bit MAC is designed with low power design methodologies at each of the system design levels. At algorithm level, a new method for multipl $y_tract operation is proposed, and it saves the transistor counts over conventional methods in hardware realization. A new Booth selector circuit using NMOS pass-transistor logic is also proposed at circuit level. It is superior to other circuits designed by CMOS in power-delay-product. And at architecture level, we adopted an ELM adder that is known to be the most efficient in power consumption, operating frequency, area and design regularity as the final adder. For registers, dynamic CMOS single-edge triggered flip-flops are used because they need less transistors per bit. To increase the operating frequency 2-stage pipeline architecture is adopted, and fast 4：2 compressors are applied in Wallace tree block. As a simulation result, the designed MAC in 0.6${\mu}{\textrm}{m}$ 1-poly 3-metal CMOS process is operated at 200MHz, 3.3V and consumed 35㎽ of power in multiply operation, and operated at 100MHz consuming 29㎽ in MAC operations, respectively.ly.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.2
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• pp.155-160
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• 2014

There are many image processing based algorithms and applications that fail when illumination change occurs. Therefore, the illumination change has to be detected then the illumination change occurred images need to be enhanced in order to keep the appropriate algorithm processing in a reality. In this paper, a new method for detecting illumination changes efficiently in a real time by using local region information and fuzzy logic is introduced. The effective way for detecting illumination changes in lighting area and the edge of the area was selected to analyze the mean and variance of the histogram of each area and to reflect the changing trends on previous frame's mean and variance for each area of the histogram. The ways are used as an input. The changes of mean and variance make different patterns w hen illumination change occurs. Fuzzy rules were defined based on the patterns of the input for detecting illumination changes. Proposed method was tested with different dataset through the evaluation metrics; in particular, the specificity, recall and precision showed high rates. An automatic parameter selection method was proposed for contrast limited adaptive histogram equalization method by using entropy of image through adaptive neural fuzzy inference system. The results showed that the contrast of images could be enhanced. The proposed algorithm is robust to detect global illumination change, and it is also computationally efficient in real applications.

• Journal of the Korean Chemical Society
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• v.47 no.6
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• pp.553-558
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• 2003

The crystal structure of $[n-Bu_4N]_2[Mo_6O_{19}]$(TBAM) (n-Bu4N=tetrabutylammonium) has been determined by X-ray crystallography. It crystallizes in the monoclinic system, space group C2/c, with lattice parameters ${\alpha}$=16.314(5), b=17.288(5), c=17.776(4)${\AA}$ ${\beta}$=101.47(3), and Z=4. In $[Mo_6O{19}]^{2-}$ anion, Mo atoms occupy six vertices of octahedron and each Mo atom is coordinated by six oxygen atoms to adopt distorted octahedral coordination geometry. The average bond distance of Mo-Ot (terminal), Mo-Ob (bridged) and Mo-Oc (central) are 1.680 ${\AA}$, 1.931 ${\AA}$ and 2.325 ${\AA}$ respectively. In $[n-Bu_4N]^+$ cation, the N atom possesses a slightly distorted tetrahedral geometry. There are some potential extensive C-H ${\cdots}$ O hydrogen bonds in the lattice, by which connecte molecules and stabilize the crystal structure. Thermogravimetric analysis suggests that thermal decomposition of the title compound includes two transitions and it loses weight at 356.0 and 803.5 $^{\circ}$, respectively, and the residue presumable be $Mo_2O_2$. Accordingly, the title compound has high thermal stability.

• Journal of Conservation Science
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• v.34 no.2
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• pp.69-76
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• 2018

Lead-based pigments (Lead White, Massicot, and Red Lead) are known to cause discoloration easily in indoor air environments. This study was conducted to investigate the effect of representative indoor air environment factors ($O_2$, $CO_2$) on lead-based pigments. As a result of the experiment, almost all of the specimens showed changes of more than ${\Delta}E=5.0$ in their values of chromaticity under $O_2$ (99%, RH 99%) and $CO_2$ (36,000 ppm, RH 99%) environments. Scanning electron microscopy also showed that the pigment particles lose sharpness of the edge. Furthermore, under the degradation, the intensities of the characteristic peaks in the X-ray diffraction patterns were decreased, and Lead White, Massicot, and Red Lead exposed to $CO_2$ (36,000 ppm, RH 99%) were shown to include the new material cerussite ($PbCO_3$). In particular, Plattnerite ($PbO_2$) was identified on Massicot, and for white lead, the characteristic peaks disappeared and those of Cerussite were identified. It was confirmed that chemical change with discoloration can occur when these lead-based pigments are exposed to a high-humidity $CO_2$ environment.

• Korean Journal of Optics and Photonics
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• v.30 no.4
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• pp.142-145
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• 2019

Normally, a corner cube retroreflector (CCRR) sheet is used as a retroreflective mirror array (RRMA) in a volumetric display. Each CCRR unit reflects light in the retroreflective direction, which is parallel to the incident light, and it makes a blurred image, as it shifts the position of light within its dimensions. Adopting a "curved planar wall" and "parabolic focusing" (x-axis), a hybrid-t(transverse direction)-RRMA is proposed, to improve the image quality and brightness. The improvement of image contrast is achieved by tuning a "linear v-shaped groove" structure to a "parabolic v-shaped groove". Also, the system has been simplified and the brightness enhanced 4 times by removing the half mirror.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.12
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• pp.889-898
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• 2022

In this paper, parallel computing method on the three-dimensional electromagnetic field is proposed. The present electromagnetic scattering analysis is conducted based on the time-harmonic vector wave equation and the finite element method. The edge-based element and 2^nd -order absorbing boundary condition are used. Parallelization of the elemental numerical integration and the matrix assemblage is accomplished by allocating the partitioned finite element subdomain for each processor. The graph partitioning library, METIS, is employed for the subdomain generation. The large sparse matrix computation is conducted by MUMPS, which is the parallel computing library based on the multi-frontal method. The accuracy of the present program is validated by the comparison against the Mie-series analytical solution and the results by ANSYS HFSS. In addition, the scalability is verified by measuring the speed-up in terms of the number of processors used. The present electromagnetic scattering analysis is performed for a perfect electric conductor sphere, isotropic/anisotropic dielectric sphere, and the missile configuration. The algorithm of the present program will be applied to the finite element and tearing method, aiming for the further extended parallel computing performance.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.1
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• pp.33-40
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• 2023

Todorokite is a manganese oxide mineral containing Mg²⁺ in a tunnel structure in which MnO₆ octahedra share corners. In order to investigate the suitability and efficiency of high temperature-treated todorokite as a material for adsorption and fixation of Cs, Cs was ion exchanged and the amount of leached Cs from todorokite was measured. The todorokite used in this study was synthesized by transforming Na-birnessite to Mg-buserite and used as a precursor. After high temperature treatment, Cs exchanged todorokite changed to birnessite and hausmannite as the temperature increased. The amount of leached Cs was investigated for Cs exchanged todorokite which was reacted with distilled water and 1 M NaCl solution at different reaction times. In general, for the samples reacted with 1 M NaCl solution, the fixation of Cs was quite effective, although the amount of leached Cs was greater due to the ion exchange reaction with Na. As the treatment temperature increased, the amount of leached Cs increased and then decreased again, which was related to the mineral phases formed at each temperature. As birnessite was formed, the amount of leached Cs increased, but as birnessite decreased, that decreased again. As the mineral phase changed to hausemanite, the amount of Cs decreased rapidly. The results of our study show that Cs exchanged todorokite can be used as a material that effectively fixes Cs and prevents its diffusion by high temperature treatment.

• Progress in Medical Physics
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• v.18 no.3
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• pp.179-185
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• 2007

The purpose of this study is to investigate the spectra of a magnetic resonance spectroscopy (MRS) in accordance with the variance of TE and the volumes of metabolites in a localized voxel for the quality assurance using a designed single voxel spectroscopy QA phantom. Because a cone-shade phantom is designed as the volume of metabolite in a localized voxel is changeable, we try to analyze the peaks of each metabolite (NAA, Cr, Cho, Lac, etc.) in accordance with metabolite volume in a localized voxel as well as echo time (TE). All data were obtained using a 3T MRI/MRS machine and analyzed using $jMRUI^{(R)}$. The results of this study show that TE is in inverse proportion to the noise of MRS and the longer TE and the less metabolite volume in the localized voxel, the peak intensities of each metabolite decrease. In case of the lactate, its peak was observed on the all TE only if the greatest metabolite is included in the localized voxel. Then, the intensity of a metabolite is more sensitive to the metabolite volume in the localized voxel than the TE. These obtained in vitro MRS data is provide the guideline that is important for in vivo metabolite quantification. But, in the edge of cone-shape vial air bubbles were observed and spectrum could not obtained. Therefore our cone-shape MRS phantom needs to be modified in order to solve these problems.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.3
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• pp.289-301
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• 2010

A structural model of the SNF(spent nuclear fuel) disposal canister for the PWR(pressurized water reactor) for about 10,000 years long term deposition at a 500m deep granitic bedrock repository has been developed through various structural safety evaluations. The SNF disposal baskets of this canister model have the array type of which four square cross section baskets stand parallel to each other and symmetrically with respect to the center of the canister section. However whether this developed structural model of the SNF disposal canister is best is not determinable yet, because the SNF disposal canister with this parallel array has a limitation in shortening the diameter for the weight reduction due to the shortest distance between the outer corner of the square section and the outer shell. Therefore, the structural safety evaluation of the SNF disposal canister with the rotated basket array which is also symmetric with respect to the canister center planes is very necessary. Even though such a canister model has not been found as yet in the literature, the structural analysis of the canister with the rotated basket array for the PWR is required for the comparative study of the structural safety of canister models. Hence, the structural analysis of the canister with the rotated basket array in which each basket is rotated with a certain amount of degrees around the center of the basket itself and arrayed symmetrically with respect to the center planes is carried out in this paper. The structural analysis result shows that the SNF disposal canister with the rotated basket array in which the SNF disposal basket is rotated as 30~35 degrees around the center of the basket itself is structurally more stable than the previously developed SNF disposal canister with the parallel basket array.