• 대한한방내과학회지
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• 제30권2호
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• pp.422-430
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• 2009

Background : Stroke is the second leading cause of death in Korea, following cancer. Stroke consists of ischemic and hemorrhagic stroke, and ischemic stroke can be largely classified as atherothrombotic stroke or embolic stroke. Carotid intima-media thickness (IMT) is an indicator of atherosclerosis used commonly as a screening test for abnormalities of the coronary artery. 24-hour ambulatory ECG is widely used to screen for underlying diseases that causes syncope, palpitation, arrhythmia, etc. Objectives : Since both carotid IMT and 24-hour ambulatory ECG are used to screen for cardiac problems, we endeavored to explore the correlation between carotid IMT and 24-hour ambulatory ECG of stroke patients. Methods : The records of ischemic stroke patients who were admitted to Kyunghee Medical Center Oriental Hospital ward from March 2006 to May 2009 were reviewed. 28 patients who had both carotid Doppler US and 24-hour ambulatory ECG test undertaken during their admission were analyzed. The relationship of abnormal ambulatory results and common carotid artery(CCA) IMT were statistically analyzed using Fisher's exact test and t-test. Results : The mean age of the abnormal ambulatory group was older than the normal group (74${\pm}$ 8.0 vs. 61${\pm}$12.1, p=0.0098). Although insignificant, the abnormal ambulatory group showed much thicker CCA-IMT than normal ambulatory group (2.l7${\pm}$ 1.16 vs. 1.51${\pm}$0.97. p=0.l389). Conclusion: No significant correlation was observed between abnormal ambulatory results and CCA-IMT. However, the difference in CCA-IMT between the two groups was too big to be ignored and further investigation with larger and better controlled trials are warranted.

• 대한전자공학회논문지TC
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• 제40권11호
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• pp.1-9
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• 2003

본 논문에서는 유전체 위에 도체 평판 상의 주기적 술롯이 배열된 다중 스크린 구조에 대한 전자파 해석 방법을 제시하였다. 이런 다중스크린 구조는 위상 변위 벽으로 둘려 싸여진 마이크로웨이브 도파관처럼 볼 수 있어, 모드 해석 방법으로 각 불연속면에서 산란행렬을 구하고 도파 구간에는 전송 산란행렬을 구하여 직렬 연산하여 다중스크린의 전체 산란행렬을 계산하는 방법을 사용하였다. 본 해석 방법을 검증하기 위해 단일스크린 구조에서 기존의 모멘트 방법으로 계산한 결과와 비교하였으며 타당함을 확인하였다. 본 해석의 적용 예로 공간여파기를 설계하여 각도와 주파수에 따른 투과 및 반사 계수의 특성을 분석하였다.

• 한국전기전자재료학회논문지
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• 제26권4호
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• pp.330-334
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• 2013

We developed a package of remote phosphor structure having blue LED chips and phosphors physically separated, and the characteristics were evaluated according to different classifications of phosphor coatings. Remote phosphor was produced by screen printing coating on glass substrate with phosphor content rated paste and heat treatment. After mounting Remote phosphor, which has been classified according to number of coatings, on top of blue LED chips, luminous flux, luminous efficacy, CCT and CRI were measured. The measurement results showed the most suitable characteristics of white LED package as a general light source when the content rate of phosphor in Remote phosphor was 80 wt.% with 3 layers of coatings and thickness over $12{\mu}m$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.366-369
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• 2002

At present, the study of direct digital X-ray detector and indirect digital X-ray detector proceed actively. But it needs high thickness and high voltage in selenium for high ionization rate. Therefore, we carried out the study of electric characteristics of a-Se with additive ratio of Iodine in drafting study for developing Hybrid X -ray Sensor for complementing direct digital X -ray detector and indirect digital X-ray detector in this paper. On this, there are formed Amorphous selenium multi-layers by sticking phosphor layer$(Gd_{2}O_{2}S(Eu^{2+}))$ using optical adhesives of EFIRON Co. Amorphous selenium multi-layers having dielectric layer(parylene) has characteristics of low dark-current, high X-ray sensitivity. So we can acquired a enhanced signal to noise ratio. We make Amorphous selenium multi-layers with $30{\mu}m$ thickness on glass.

• Steel and Composite Structures
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• 제46권1호
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• pp.15-31
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• 2023

Organic solar cells utilized natural polymers to convert solar energy to electricity. The demands for green energy production and less disposal of toxic materials make them one of the interesting candidates for replacing conventional solar cells. However, the different aspects of their properties including mechanical strength and stability are not well recognized. Therefore, in the present study, we aim to explore the chaotic responses of these organic solar cells. In doing so, a specific type of organic solar cell constructed from layers of material with different thicknesses is considered to obtain vibrational and chaotic responses under different boundaries and initial conditions. A square plate structure is examined with first-order shear deformation theory to acquire the displacement field in the laminated structure. The bounding between different layers is considered to be perfect with no sliding and separation. On the other hand, nonlocal elasticity theory is engaged in incorporating the structural effects of the organic material into calculations. Hamilton's principle is adopted to obtain governing equations with regard to boundary conditions and mechanical loadings. The extracted equations of motion were solved using the perturbation method and differential quadrature approach. The results demonstrated the significant effect of relative glass layer thickness on the chaotic behavior of the structure with higher relative thickness leading to less chaotic responses. Moreover, a comprehensive parameter study is presented to examine the effects of nonlocality and relative thicknesses on the natural frequency of square organic solar cell structure.

• 한국결정성장학회지
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• 제31권6호
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• pp.282-286
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• 2021

Laser-carburized TiZrN 코팅의 침탄 공정에서 탄소 페이스트 두께에 따른 탄소의 침투 깊이 및 압축잔류응력 변화를 탄소 포텐셜 측면으로 비교·고찰하였다. 스크린 프린팅과 스핀 코팅 방법을 이용하여 각각 1.1 mm와 0.4 mm의 두께로 탄소 페이스트를 도포하고, 동일한 레이저 조사 조건에서 레이저 침탄을 실시하였다. 탄소 페이스트가 두꺼워질수록 침탄된 TiZrN 시료의 회절 패턴이 더 저각으로 이동하였으며, 고용체 강화 및 격자 왜곡의 심화를 나타내었다. TEM을 이용한 미세구조 분석에서도 두꺼운 페이스트로부터 침탄된 TiZrN 내 결정질 결함이 증가하고 높은 탄소 농도를 보였으며, 이는 페이스트 두께가 두꺼워질수록 탄소 포텐셜도 높아짐을 의미하였다. XPS depth profile 분석에서도 두꺼운 페이스트를 통해 침탄된 TiZrN 시료에서 높은 탄소 농도 및 탄화물 형성을 보이면서, 탄소 페이스트 두께 조절에 의해 침탄에서 표면 탄소농도와 탄소 포텐셜 증가가 일어남을 나타내었다. 아울러, 탄소 농도의 증가는 표면의 압축잔류응력 증가(3.67 GPa에서 4.58 GPa로)에 기여하였음을 확인하였다.

• 한국인쇄학회지
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• 제29권1호
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• pp.23-33
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• 2011

This experimental focus to characterize luminescence properties related to CNT (Carbon Nano Tube) element dispersedly implanted in ZnS-based phosphor thin film panel fabricated by a screen printing method. More specifically FE-SEM measurements, L-V(Luminescence vs. Voltage) and photo luminescence were carried out to determine an optimum value of CNT concentration and film thickness for the thin film structure of CNT-ZnS:(Cu, Al) by the screen printing method. We confirmed that an optimum value of CNT concentration in the ZnS:(Cu, Al) film panel is about 0.75 wt% resulting that the electric conductivity is 1.6 times higher than that of pure CNT sample and showing that the luminescence intensity is increasing until the optimum concentration. Clearly, CNT is presenting in the luminescence process providing a pathway for the creation of hot electron and a channel for the electron-hole recombination but overly inserted CNT may hinder to produce the hot electron for making an avalanching process. In case of the overly doped CNT 1.0 wt% in the ZnS-based phosphor, the luminescence intensity is decreasing although the electric conductivity is exponentially increasing. Based on these results, we realized that hot electron occurred by the external electric field or exciton arose by the external photon source are reduced dramatically over the critical value of CNT concentration because CNT element provide various isolated residues in the composites of ZnS based phosphor rather than pathway or channel for the D-A(Donnor to Acceptor) pair transition or the radiative recombination of electron-hole.

• 한국표면공학회지
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• 제42권1호
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• pp.21-25
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• 2009

Using an evaporation system, $SiO_2$ was deposited as a buffer layer between a PET substrate and a ITO layer and then ITO/$SiO_2$/PET layers were annealed for 1.5 hours at the temperature of $180^{\circ}C$. Adhesion and electro-optical properties of ITO films were studied with thickness variance of a $SiO_2$ buffer layer. As a result of introduction of the $SiO_2$ buffer layer, sheet resistance and resistivity increased and a ITO film with optimum sheet resistance ($529.3{\Omega}/square$) for an upper ITO film of resistive type touch panel could be obtained when $SiO_2$ of $50{\AA}$ was deposited. And it was found that ITO films with $SiO_2$ buffer layer have higher transmittance of $88{\sim}90%$ at 550 nm wavelength than ITO films with no buffer layers and the transmittance was enhanced as $SiO_2$ thickness increased from $50{\AA}$ to $100{\AA}$. Adhesion property of ITO films with $SiO_2$ buffer layers became better than ITO films with no buffer layers and this property was independent of $SiO_2$ thickness variance ($50{\sim}100{\AA}$). By depositing a $SiO_2$ buffer layer of $50{\AA}$ on the PET substrate and sputtering a ITO thin film on the layer, a ITO film with enhanced adhesion, electro-optical properties could be obtained.

• Journal of the Korean Wood Science and Technology
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• 제18권4호
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• pp.53-64
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• 1990

This study was carried out to develop the traditional korean paper changphanji from the bast fiber of paper mulberry The results obtained were as follows: 1. The variations in the basis weight were remarkable, but there were no significant adverse effects on the tensile strength and thickness. 2. The stamping have contributed to the improvement of smoothness and the control of thickness. The automatic pressing system recommended to obtain good control of thickness. 3. The average density of the traditional korean paper changphanji was 1.06g/$cm^3$. 4. The changphanji developed in this study gave a clude, but excellent toughness and warm feeling. Some fiber lumps, dark spots and bamboo, screen marks were also obserded. 5. The tensile strength of four-fold sheet changphanji is highest and those of two-fold sheet changphanji is lowest. the lengthwise tensile strength was higher than crosswise one due to the fiber. 6. The elongation of three-fold sheet changphanji was highest 7. The water absorption of all products ranged from 11.3g/$m^2$ to 17.5g/$m^2$. 8. The wight loss by abrasion was 34.0%(four-fold sheet) 31.6%(three fold sheet), 31.0% (two-fold sheet)respectively. 9. Based on the results obtained. tensile strength and elongation, the four-fold sheet was excellent. the use of the bast fiber of paper mulberry as a raw material is attractive point which can not obtained from the commercial changphanji made from other raw materials.

• 비파괴검사학회지
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• 제14권4호
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• pp.228-236
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• 1995

본 연구에서는 비파괴검사 방법의 하나인 gamma scanning test에 의한 대단위 차폐체의 결함을 평가하는 방법을 제시하고 방사선 차폐를 해석하는 유용한 방법중의 하나인 Monte Carlo 코드로 이에 대한 검증을 하였다. Gamma scanning test로 차폐체의 결함을 평가하기 위한 모델은 원통형 차폐체를 대상으로 하였다. 먼저 방사성물질 운반용기에 대한 설계기준에 따라 기준차폐체를 설치하여 Co-60 선원과 섬광계수기로 기준치를 측정하고, 그 다음 실물의 원통형 차폐체를 측정하였다. 기준치로 원통형 차폐체의 납두께를 환산한 결과 결함두께는 최대 12mm로 평가되었다. 이를 검증하기 위한 MCNP 코드의 계산에서는 결함두께가 실험적 결과에 비해 4.1%에 해당하는 최대 11.6mm를 나타내었으며, 두 결과가 만족할 정도로 일치함을 보여주고 있다. 따라서 이러한 평가방법은 방사성물질을 사용하는 시설에 설치되는 대단위 방사선 차폐체나 대용량의 운반용기 차폐능 검사시 현장에서 적용시킬 수 있으며 측정치의 신뢰도를 제고할 수 있다. 앞으로 보다 정확한 측정을 위하여 차폐체의 두께 측정결과가 화면에 직접 표시되는 측정장치의 연구 개발이 요구된다.