• Corrosion Science and Technology
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• 제21권4호
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• pp.243-249
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• 2022

The objective of the present study was to perform failure analysis of double-layered bellow (expansion joint), a core part of stress reliever, used to relieve axial stresses induced by thermal expansion of heat-transport pipes in a district heating system. The bellow underwent tensile or compressive stresses due to its structure in terms of position. A leaked position sufferred a fatigue with a tensile component for decades. A cracked bellow contained a higher fraction of martensitic phase because of manufacturing and usage histories, which induced more brittleness on the component. Inclusions in the inner layer of the bellow acted as a site of stress concentration, from which cracks initiated and then propagated along the hoop direction from the inner surface of the inner layer under fatigue loading conditions. As the crack reached critical thickness, the crack propagated to the outer surface at a higher rate, resulting in leakage of the stress reliever.

• Journal of Korean Vacuum Science & Technology
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• 제7권1호
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• pp.8-12
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• 2003

The effects of lattice strain on the magnetic and the transport properties of La$_{0.8}$Sr$_{0.2}$MnO$_3$films grown on a LaAlO$_3$ (001) substrate and on a La$_{0.8}$Sr$_{0.2}$MnO$_3$ layer have been studied. It was observed that the metal-insulator and the ferromagnetic transitions turn out to be at higher temperatures for the film deposited on La$_{0.8}$Sr$_{0.2}$MnO$_3$ layer with respect to that on LaAlO$_3$. The dependence of Curie temperature on the bulk and the Jahn-Teller strains has also been determined. determined.

• 전기화학회지
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• 제2권2호
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• pp.98-105
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• 1999

본 연구에서는 전기장에 의하여 유발되는 자연대류의 영향을 줄이기 위하여 수평 다공성 유체층에 열적 성충화를 유지하여 부력과 유체층의 안정화 효과를 체계적으로 조사하였다. 이를 위하여 수평 다공성 유체층에서 이중확산대류에 의한 물질전달 상관식을 이론적으로 유도하고, 전기화학 실험을 통하여 이론에 의한 모델을 보완하였다. 물질전달 상관식은 다공성 매질층에 대한 유동 방정식으로 Forchheimer모델을 사용하고 미세 난류 모델을 적용하여, 용질 및 열 Darcy-Rayleigh수와 Lewis 수로 유도하였다. 실험에서는 다공성매질에 포화된 황산구리황산용액내의 구리이온을 전기 화학적 방법을 통하여 확산 또는 자연대류에 의한 물질전달 실험을 수행하였다. 이론 및 실험적 해석 결과를 종합하면 다공성 매질 내에서 구리이온의 이중확산대류에 의한 물질전달 상관식은 다음과 같다. $$Sh=\frac{0.03054(Rs_D-LeRa_D)^{1/2}}{1-3.8788(Rs_D-LeRa_D)^{-1/10}}$$ 본 연구의 결과는 실험치와 잘 부합되었으며, 모델식의 원형은 열 및 물질전달계에서 자연대류의 영향을 효과적으로 제어할 수 있는 방안으로 활용될 수 있을 것이다.

• Coupled systems mechanics
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• 제5권3호
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• pp.203-221
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• 2016

The present study deals with the numerical modelling for the one dimensional contaminant transport through saturated homogeneous and stratified porous media using meshfree method. A numerical algorithm based on element free Galerkin method is developed. A one dimensional form of the advectivediffusive transport equation for homogeneous and stratified soil is considered for the analysis using irregular nodes. A Fortran program is developed to obtain numerical solution and the results are validated with the available results in the literature. A detailed parametric study is conducted to examine the effect of certain key parameters. Effect of change of dispersion, velocity, porosity, distribution coefficient and thickness of layer is studied on the concentration of the contaminant.

• Journal of Electrical Engineering and Technology
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• 제4권3호
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• pp.418-422
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• 2009

We synthesized new electroluminescence materials [(1,10-phenanthroline)(8-hydroxyquinoline)] Zn(phen)q and investigated their electron transport properties. We used Zn(phen)q and $Alq_3$ for the conductive materials and measured their electron transport properties as a function of the organic layer thickness. The difference between Zn(phen)q and $Alq_3$ as electron transporting materials suggests that the electrical properties depends on the carrier injection.

• ETRI Journal
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• 제30권3호
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• pp.441-450
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• 2008

The scalable extension of H.264, known as scalable video coding (SVC) has been the main focus of the Joint Video Team's work and was finalized at the end of 2007. Synchronization between media is an important aspect in the design of a scalable video streaming system. This paper proposes an efficient media synchronization mechanism for SVC video transport over IP networks. To support synchronization between video and audio bitstreams transported over IP networks, a real-time transport protocol/RTP control protocol (RTP/RTCP) suite is usually employed. To provide an efficient mechanism for media synchronization between SVC video and audio, we suggest an efficient RTP packetization mode for inter-layer synchronization within SVC video and propose a computationally efficient RTCP packet processing method for inter-media synchronization. By adopting the computationally simple RTCP packet processing, we do not need to process every RTCP sender report packet for inter-media synchronization. We demonstrate the effectiveness of the proposed mechanism by comparing its performance with that of the conventional method.

• Journal of Information Display
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• 제12권4호
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• pp.219-222
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• 2011

Iridium-(III)-bis[(4,6-di-fluorophenyl)-pyridinate-N,$C^2$' ]picolinate-based blue phosphorescent organic light-emitting diodes with different electron transport materials were fabricated. Each electron transport material had different electron mobilities and triplet energies. The device with 1,3,5-tri(m-pyrid-3-yl-phenyl)benzene had the highest external quantum efficiency (20.1%) and luminous current efficiency (33.1 cd/A) due to its high electron mobility and triplet energy. The operational stability of each device was also compared with that of the others. The device with 2,2',2"(1,3,5-benzenetriyl)tris-(1-phenyl-1H-benzimidazole) was found to have a longer lifetime than the other devices.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2003년도 International Symposium on Clean Environment
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• pp.65-68
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• 2003

A quantitative study of the amount of air transported between the boundary layer and the free atmosphere is important for understanding air quality and upper tropospheric ozone, which is a greenhouse gas. Frontal systems are known to be an effective mechanism for the vertical transport of pollutants. Numerical experiments have been performed with a simple two-dimensional front model to simulate vertical transport of trace gases within developing cold fronts. Three different trace gases experiments have been done numerically according to the different initial fields of trace gases such as aerosol, ozone and $H_2O_2$. Trace gas field tilts to the east while the front tilts to the west. Aerosol simulation shows that pollutants can be transported out of the boundary to altitudes of about 10 km. The stratospheric ozone is brought downwards in a tropopause fold behind of the frontal surface. The meridional gradient in trace gas ($H_2O_2$) can cause a complicate structure in the trace field by the meridional advection.

• Computers and Concrete
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• 제16권5호
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• pp.775-793
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• 2015

Moisture transport in concrete in atmospheric environment was studied in this paper. Based on the simplified formula of the thickness of the adsorbed layer, the pore-size distribution function of cement paste was calculated utilizing the water adsorption isotherms. Taking into consideration of the hysteresis effect in cement paste, the moisture diffusivity of cement paste was obtained by the integration of the pore-size distribution. Concrete is regarded as a two-phase composite with cement paste and aggregate, neglecting the moisture diffusivity of aggregate, then moisture diffusivity of concrete was evaluated using the composite theory. Finally, numerical simulation of humidity response during both wetting and drying process was carried out by the finite difference method of partial differential equation for moisture transport, and the numerical results well capture the trend of the measured data.

• 마이크로전자및패키징학회지
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• 제10권1호
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• pp.1-5
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• 2003

본 연구에서는 ITO (indium tin oxide)/glass 투명기판 위에 다층구조의 OELD (organic electroluminescent devices) 소자를 진공 열증착법으로 제작하였다. 발광층 재료로서 Alq$_3$(tris-(8-hydroxyquinoline)aluminum)물질을 사용하였고, 정공수송층으로는 TPD (triphenyl-diamine) 및 $\alpha-NPD$를 사용하였다. 정공주입층 재료로서 CuPc (Copper phthalocyanine)를 사용하였다. 또한 QD2(quinacridone2) 물질을 $Alq_3$ 발광층내에 약 $10\AA$ 두께로 증착하여 발광효율 향상을 시도하였다. 제작된 모든 소자의 발광개시전압은 약 7 V 이었으며, 정공수송층으로 TPD 물질대신에 열적안정성이 우수한 $\alpha-NPD$를 사용한 경우 휘도값과 발광효율이 개선되었다. $Alq_3$ 발광층 사이에 QD2 물질을 적층한 소자에서 발광효율은 1.55 lm/W 값을 나타내어 $Alq_3$ 발광층만을 사용한 경우에 비해 약 8배 발광효율이 향상되었다.