• The Journal of the Korea Contents Association
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• v.5 no.6
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• pp.331-342
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• 2005

In this paper, we propose an efficient watermarking algorithm using block indexing. The proposed algorithm is a novel blind watermarking scheme using the indexed watermark value based on the spread spectrum method. The watermark insertion is allocated into index value of each block after dividing original image into sub-blocks. The watermark embedded in mappinged with index values of blocks, And the mappinged blocks convert to DCT and then the PN sequence embedded to middle frequency band. Consequently the watermark is expressed by index value of sub-blocks. The watermark extracted from the correlation of between PN sequence and watermarked image. Experimental results demonstrate that the watermarked image has a good quality in terms of imperceptibility and is robust against various attacks.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.2
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• pp.85-92
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• 2007

In 1980s, a number of bridges with bare concrete deck were constructed on the Korea highway. After 20 years service, many bare concrete decks are still in good condition without special maintenance activity. Therefore, the application of the bare concrete deck is being reestimated from the view of construction and maintenance. As a part of the program, the characteristic of penetration(surface chloride and apparent diffusion coefficient) of de-icing salt into bare concrete bridge deck was analyzed in order to predict the service life of bridge on Korea highway.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3114-3119
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• 2008

Relatively high convective flow exists in the under-rib regions of a gas diffusion layer (GDL) when serpentine flow fields are employed in a PEMFC. This under-rib convection is believed to be favorable for the performance of PEMFCs, by enabling more effective use of catalysts in the under-rib regions. From the fact that the under-rib convection in a GDL is directly proportional to the permeability of the GDL, computational fluid dynamics (CFD) simulations were performed to discover the relationship between the GDL permeability and the PEMFC performance. Single-, triple-, and quintuple-path parallel serpentine flow fields for $9\;cm^2$ active cell area were considered while changing the GDL permeability from $1{\times}10^{-12}$ to $5{\times}10^{-11}m^2$. The results showed that higher GDL permeability generally resulted in better performance of PEMFCs, but the degree of performance enhancement became smaller as the parallel path number increased. The effects of the permeability on the local variables were also discussed.

• Journal of Ocean Engineering and Technology
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• v.32 no.6
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• pp.474-484
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• 2018

In this study, a new numerical modeling system was proposed to predict oil spills, which increasingly occur at sea as a result of abnormal weather conditions such as global warming. The hydrodynamic conditions such as the flow velocity needed to calculate oil dispersion were estimated using a three dimensional hydrodynamic model based on the Navier-Stokes equation, which considered all of the physical variations in the vertical direction. This improved the accuracy compared to those estimated by the conventional shallow water equation. The advection-diffusion model for the spilled oil was combined with the hydrodynamic model to predict the movement and fate of the oil. The effects of absorption, weathering, and wind were also considered in the calculation process. The combined model developed in this study was then applied to various test cases to identify the characteristics of oil dispersion over time. It is expected that the developed model will help to establish initial response and disaster prevention plans in the event of a nearshore oil spill.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.130-131
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• 2003

The magnetic and thermal properties of NiFe/IrMn/CoFe with Mn additions have been studied. As grown CoFe pinned-layers with IrMn-Mn have dominantly larger exchange biasing field( $H_{ex}$) and blocking temperature( $T_{b}$) than when pure I $r_{22}$M $n_{78}$ is used. The magnetic properties improve, $H_{ex}$ and $T_{b}$ improve with 77-78 vol% Mn, but drop considerably with more Mn additions, losing magnetic properties of theb NiFe/IrMn/CoFe with addition 0.6 vol % Mn. The average x-ray diffraction peak ratios fcc (111)CoFe of (111)IrM $n_3$ textures for the Mn inserted total vol of 75, 77, and 79 vol% were about 1.4, 0.8, and 0.6, respectively. For the sample without Mn inserted layer, the $H_{ex}$ between I $r_{22}$M $n_{78}$ and CoFe layers is almost nothing. For two multilayer as-grown samples with ultra-thin Mn layers of 77 vol % and 79 vol %, the $H_{ex}$s are 250 Oe and 150 Oe, respectively. In case of IrMn with 77.5 vol% Mn, the $H_{ex}$ was 444 Oe up to 30$0^{\circ}C$ endured of 363 Oe at 40$0^{\circ}C$, respectively. Mn additions improve the magnetic properties and thermal stabilities of NiFe/IrMn/CoFe. Those increase the $H_{ex}$ and $T_{b}$. In applications where higher $H_{ex}$ and $T_{b}$ are accept, proper concentrations of Mn can be used.n can be used.be used.

• Journal of the Korean Society of Radiology
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• v.12 no.2
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• pp.261-269
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• 2018

The fractional anisotropy value of the basal ganglia fibers in the brain gray matter region was analyzed by Tract-Based Spatial Statics(TBSS) method after acquiring the diffusion tensor image to identify the presence or absence of brain white matter damage to smoking in male. As a result of measurement analysis, the fractional anisotropy measurement value was lower in smokers than non-smokers in all areas, and the FA value was statistically significant. smoking significantly affects all the anatomic micro structural changes in the brain gray matter and damages the nerve fiber tract. As a result, it can affects functional abnormalities related to the minute changes of the brain due to smoking.

• Nuclear Engineering and Technology
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• v.26 no.1
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• pp.90-99
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• 1994

One of the major phenomena occurring in defective fuel rods is the oxidation of UO$_2$ fuel pellets from UO$_2$ to UO$_{2+}$x/ by the oxygen Produced from the dissociation of the steam in the Pellet-to-clad gap, which leads to the enhancement of fission gas release. In this paper, the oxidation kinetics of defective fuel rods was analyzed on the basis of operating conditions of the reactor and defective fuel rod itself. Oxidation kinetics of the fuel pellet was determined under the assumption that the gap is filled with the saturated steam of 150 atm and an enhancement factor for fission gas release was introduced to take into account the effect of fuel oxidation on fission gas release. Comparison with experimental data shows that the enhancement factor predicts well the increased fission gas release due to the oxidation of UO$_2$fuel pellets.

• Investigative Magnetic Resonance Imaging
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• v.18 no.4
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• pp.357-361
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• 2014

Purpose : In a previous report, it took several days for white matter lesions to regress in hypoglycemic encephalopathy. We present a case of rapid diffusion-weighted image (DWI) changes in hypoglycemic encephalopathy. Case Report: A 58-year-old male patient was found semi-comatous with the only abnormality in his laboratory tests showing hypoglycemia (44 mg/dL). After rapid correction of glucose level, immediate brain DWI showed bilateral subcortical white matter lesions. After about 5 hours, follow-up DWI showed resolved subcortical white matter lesions, with newly-appeared bilateral fronto-temporo-parietal cortical lesions. Conclusion: Both white matter and cortex involvement in hypoglycemic encephalopathy has been shown in several reports, but rapid regression of white matter changes in hypoglycemic encephalopathy has been rarely reported. It is important to know that MR imaging changes in hypoglycemic encephalopathy can be made as quick as just a few-hour-long.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.265-265
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• 2014

일반적으로 태양전지 및 반도체 공정에서 불순물 주입 과정인 도핑(Doping)공정은 크게 몇 가지 방법으로 구분해 볼 수 있다. 소성로(Furnace)를 이용하여 열을 통해 불순물을 웨이퍼 내부로 확산시키는 열확산 방법과 진공 챔버 내부에서 전자기장을 걸어 이온을 극도로 가속시켜 진행하는 이온 주입(Ion implantation)이나 이온 샤워(Ion shower)를 이용한 도핑 방법이 있다. 또한 최근 자외영역 파장의 레이저광을 조사하여 광화학 반응에 의해 도펀트 물질를 분해하는 동시에 조사 부분을 용해하여 불순물을 도포하는 기법인 레이져 도핑(Laser doping) 방법이 개발중이다. 그러나 레이져나 이온 도핑 공정기술은 고가의 복잡한 장비가 필요하여 매출 수익성 및 대량생산에 비효율적이며 이온 주입에 의한 박막의 손상을 치료하기 위한 후속 어닐링(Post-annealing) 과정이 요구되는 단점을 가지고 있고 열확산 도핑 방법은 정량적인 불순물 주입 제어가 어렵고 시간 대비 생산량의 한계가 있다. 반면 대기압 플라즈마로 도핑을 할 경우 기존에 진공개념을 벗어나 공정상에서 보다 저가의 생산을 가능케 할 뿐아니라 멀티 플라즈마 소스 개발로 이어진다면 시간적인 측면에서도 단연 단축시킬 수가 있어 보다 대량 생산 공정에 효과적이다. 따라서 본 연구에서는 새로운 도핑 방법인 대기압 플라즈마를 이용한 도핑 공정기술의 가능성을 제안하고자 도핑 공정 시 웨이퍼 내 전류 패스(Current path)에 대한 메카니즘을 연구하였다. 대기압 플라즈마 방전 시 전류가 웨이퍼 내부에 흐를 때 발생되는 열을 이용하여 도핑이 되는 형식이란 점을 가정하고 이 점에 대한 원리를 증명하고자 실험을 진행하였다. 실험 방식은 그라운드(Ground) 내 웨이퍼의 위치와 웨이퍼 내 방전 위치에 따라 적외선 화상(IR image: Infrared image) 화상을 서로 비교하였다. 적외선 화상은 실험 조건에 따라 화상 내 고온의 표식이 상이하게 변하는 경향성을 나타내었다. 이 고온의 표식이 전류 패스라는 점을 증명하고자 시뮬레이션을 통해 자기장의 전산모사를 한 결과 전류 패스의 수직 방향으로 자기장이 형성이 됨을 확인하였으며 이는 즉 웨이퍼 내부 전류 패스에 따라 도핑이 된다는 사실을 명백히 말해주는 것이며 전류 패스 제어의 가능성과 이에 따라 SE(Selective Emitter) 공정 분야 응용 가능성을 보여준다.

• Journal of the Korean Society of Radiology
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• v.12 no.2
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• pp.253-260
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• 2018

Diffusion tensor images were obtained to investigate the damage of brain white matter in non-smokers and an adequate drinking group (less than 10 points) selected by scores of the Korean versions of alcohol use disorders identification test questionnaire. Factional anisotropy (FA) values, according to the variables of age and body mass index (BMI), were not statistically significant in all regions of the brain white matter after measurement of factional anisotropy (FA) values by the tract-based spatial statics (TBSS) method. In other words, age and body mass index (BMI) do not significantly affect the microstructural changes of the brain white matter.