• 대한토목학회논문집
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• 제3권3호
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• pp.107-116
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• 1983

다짐 에너지 변화(變化)에 따르는 화강풍화토의 입도변화(粒度變化) 및 파쇄량(破碎量)이 투수성(透水性)에 미치는 영향에 대해 연구하였다. 토립자(土粒子)의 파쇄(破碎)는 토립자(土粒子)의 표면적비(表面積比)($S_w{^{\prime}}/S_w$)로서 나타냈고, 다짐에너지를 변화(變化)시키면서 실시한 다짐 시험결과(試驗結果) 만들어진 시료(試料)에 변수위투수시험을 행(行)하여 투수계수와 최적함수비(最適含水比)와의 관계를 조사(調査)하였다. 그 결과(結果) 다음과 같은 사항을 알 수 있었다. (1) 다짐에너지의 증대(增大)에 따라 파쇄(破碎)가 커지고 간극비(間隙比)가 감소되고 건조밀도는 영공극곡선(零空隙曲線)에 평행(平行)하게 증대(增大)된다. (2) 표면적비(表面積比)는 다짐회수에 관계없이 $S_w{^{\prime}}/S_w=0.33(P)^{0.96}$로 표시(表示)할 수 있다. (3) 입자파쇄(粒子破碎)가 가장 크게 일어나는 입경(粒徑)은 0.5~1 mm 범위이다. (4) 최적함수비(最適含水比) 상태에서 투수계수 K와 간극비함수(間隙比函數) $\frac{e^3}{1+3}$와의 관계는 양면대수지상(兩面對數紙上)에서 직선 관계가 성립(成立)한다. (5) 최적함수비(最適函數比) 상태에서 다짐에너지가 증가(增加)되면 200번(番)체 통과량(通過量)은 거의 직선적으로 증가(增加)되며 표면적비(表面積比)의 증대(增大)는 투수성(透水性)의 저하(低下)를 갖고온다.

• 한국결정성장학회지
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• 제9권2호
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• pp.162-167
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• 1999

3가지 방향성을 가진 사파이어 기판 위에 GaN 박막을 OMVPE방식으로 증착시켜 증착된 GaN epilayer를 투과전자현미경으로 분석하여 각 미세구조의 차이를 비교분석하였다. 3 가지 방향 모두에서 GaN 증착층이 관찰되어졌으며 그중 가장 좋은 경계면의 상태와 단일결정성을 보여준 것은 사파이어{0001} 방향의 기판을 사용한 경우였다. 결함들도 {0001} 방향의 기판을 사용한 경우에서 가장 적게 나타났다. 모든 경우에서 buffer layer는 발견되어지지 않았고 그럼에도 불구하고 경계면에서의 격자 뒤틀림이 일어나는 지역이 수 나노미터(nanometer) 정도밖에 안되는 우수한 경계면들이 관찰되었다. 따라서 일반적으로 GaN 박막 증착시에 가장 많이 사용되는 사파이어 basal plane 외에도 결함이 많기는 하지만, {1120}와 {1102} plane 위에도 GaN 증착층이 buffer layer 없이 증착 될 수 있다는 사실을 TEM 관찰을 통하여 알 수 있었으며 사파이어 {0001}면를 기판으로 사용한 경우에 미세구조 측면에서 볼 때 hetero-epitaxial한 GaN 박막층을 얻을 수 있는 것을 확인하였다.

• Carbon letters
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• 제22권
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• pp.1-13
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• 2017

Porous materials play a vital role in science and technology. The ability to control their pore structures at the atomic, molecular, and nanometer scales enable interactions with atoms, ions and molecules to occur throughout the bulk of the material, for practical applications. Three-dimensional (3D) porous carbon-based materials (e.g., graphene aerogels/hydrogels, sponges and foams) made of graphene or graphene oxide-based networks have attracted considerable attention because they offer low density, high porosity, large surface area, excellent electrical conductivity and stable mechanical properties. Water pollution and associated environmental issues have become a hot topic in recent years. Rapid industrialization has led to a massive increase in the amount of wastewater that industries discharge into the environment. Water pollution is caused by oil spills, heavy metals, dyes, and organic compounds released by industry, as well as via unpredictable accidents. In addition, water pollution is also caused by radionuclides released by nuclear disasters or leakage. This review presents an overview of the state-of-the-art synthesis methodologies of 3D porous graphene materials and highlights their synthesis for environmental applications. The various synthetic methods used to prepare these 3D materials are discussed, particularly template-free self-assembly methods, and template-directed methods. Some key results are summarized, where 3D graphene materials have been used for the adsorption of dyes, heavy metals, and radioactive materials from polluted environments.

• Journal of the Korean Wood Science and Technology
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• 제35권2호
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• pp.69-78
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• 2007

The mechanical properties of wood flour, Hwangto (325 and 1,400 mesh per 25,4 mm) and coupling agent-reinforced HDPE composites were investigated in this study. Hwangto and maleated polyethylene (MAPE) were used as an inorganic filler and a coupling agent, respectively. The addition of Hwangto and MAPE to virgin HDPE also increased the Young's modulus in the smaller degree. The addition of wood flour and Hwangto to virgin HDPE increased the tensile strength, due to the high uniform dispersion of HDPE by high surface area of Hwangto in HDPE and wood flour. MAPE also significantly increased the tensile strength. When wood flour was added, there was no notable difference on the tensile properties, in terms of Hwangto particle size. Hwangto also improved the flexural modulus and strength of reinforced HDPE composites. With different particle sizes of Hwangto, there was no considerable difference in flexural modulus and strength of reinforced HDPE composites. The addition of Hwangto showed slightly lower impact strength than that of wood flour. However, the particle size of Hwangto showed no significant effect on the impact strength of reinforced composites. In conclusion, reinforced HDPE composites with organic and inorganic fillers provide highly improved mechanical properties over virgin HDPE.

• 대한공간정보학회지
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• 제18권3호
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• pp.11-19
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• 2010

최근 들어 우리나라에서는 지역적인 돌발 및 집중강우패턴으로 인해 산사태 등의 자연재해발생이 증가하고 있다. 이에 따라 산사태를 모니터링하고 관리하기 위하여 최신의 3차원 측량장비인 LiDAR 등으로 취득한 고정밀 고밀도의 수치고도자료를 이용하여 산사태지역에서의 변위탐지와 모니터링을 위한 지면변위 연구가 시도되고 있다. 그러나 대용량의 LiDAR 데이터를 처리하는 상업용 소프트웨어는 고가이며, 산사태 분석과 같은 특화된 업무에 적용하기에 무리가 있다. 또한 산사태와 관련된 다양한 공간정보를 다수의 이용자가 쉽게 접근하여 직관적으로 활용할 수 있는 방안이 없는 실정이다. 따라서 본 연구에서는 시계열 LiDAR 데이터를 처리하여 산사태를 분석할 수 있으며, 해당 지역에서의 지형 및 산사태 관련정보를 다수의 사용자에게 직관적으로 서비스할 수 있는 응용프로그램을 개발하였다. 또한 사례연구를 통해 연구지역에 대한 산사태 현황을 분석할 수 있었으며, 3차원 기반의 산사태 및 지형정보를 직관적으로 서비스할 수 있음을 제시하였다.

• 한국항공우주학회지
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• 제36권11호
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• pp.1056-1062
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• 2008

인공위성의 추력기에서 발생되는 플룸과 기저면의 상호 작용에 관한 연구를 직접모사법을 사용하여 실시하였다. 질소와 수소 분자의 충돌에 의한 회전-병진 에너지의 교환을 정확하게 모사하기 위하여 최근에 연구 되어진 질소와 수소 분자의 회전 에너지 이완 모델을 사용하였다. 추력기 플룸과 기저면의 상호 작용 해석을 위하여 플룸 분자들의 수밀도 분포와 회전, 병진 온도 분포, 열전달량, 압력 등에 대하여 다양한 운영 조건에 맞추어 해석을 실시하였다. 그 결과 기저면에서는 질소 분자보다 수소 분자의 분포가 매우 큰 것과, 분포하는 대부분의 수소 분자가 회전 에너지에 대해 비평형 상태로 분포 하는 것을 확인 하였다. 이는 수소 분자의 정확한 회전 에너지 이완 모델의 필요성을 보여주고 있는 결과이며, 본 연구의 경우 가장 최근의 수소의 회전 에너지에 관련된 모델을 사용함으로써 플룸과 기저면의 상호 작용 해석에 대한 정확도를 증진 시켰다.

• The Korean Journal of Physiology and Pharmacology
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• 제4권6호
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• pp.487-496
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• 2000

Insulin stimulates glucose transport in muscle and fat cells by promoting the translocation of glucose transporter (GLUT4) to the cell surface. Phosphatidylinositide 3-kinase (PI3-kinase) has been implicated in this process. However, the involvement of protein kinase B (PKB)/Akt and $PKC-{\zeta}$, those are known as the downstream target of PI3-kinase in regulation of GLUT4 translocation, is not known yet. An interesting possibility is that these protein kinases phosphorylate GLUT4 directly in this process. In the present study, $PKB-{\alpha}$ and $PKC-{\zeta}$ were added exogenously to GLUT4-containing vesicles purified from low density microsome (LDM) of the rat adipocytes by immunoadsorption and immunoprecipitation for direct phosphorylation of GLUT4. Interestingly GLUT4 was phosphorylated by $PKC-{\zeta}$ and its phosphorylation was increased in insulin stimulated state but GLUT4 was not phosphorylated by $PKB-{\alpha}.$ However, the GST-fusion proteins, GLUT4 C-terminal cytoplasmic domain (GLUT4C) and the entire major GLUT4 cytoplasmic domain corresponding to N-terminus, central loop and C-terminus in tandem (GLUT4NLC) were phosphorylated by both $PKB-{\alpha}$ and $PKC-{\zeta}.$ The immunoblots of $PKC-{\zeta}$ and $PKB-{\alpha}$ antibodies with GLUT4-containing vesicles preparation showed that $PKC-{\zeta}$ was co-localized with the vesicles but not $PKB-{\alpha}.$ From the above results, it is clear that $PKC-{\zeta}$ interacts with GLUT4-containing vesicles and it phosphorylates GLUT4 protein directly but $PKB-{\alpha}$ does not interact with GLUT4, suggesting that insulin-elicited signals that pass through PI3-kinase subsequently diverge into two independent pathways, an Akt pathway and a $PKC-{\zeta}$ pathway, and that later pathway contributes, at least in part, insulin stimulation of GLUT4 translocation in adipocytes via a direct GLUT4 phosphorylation.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.470-470
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• 2012

Organic thin film transistors (OTFTs) backplane constitute the active elements in new generations of plastic electronic devices for flexible display. The overall OTFTs performance is largely depended on the properties and quality of each layers of device material. In solution based process of organic semiconductors (OSCs), the interface state is most impediments to preferable performance. Generally, a threshold voltage (Vth) shift is usually exhibited when organic gate insulators (OGIs) are exposed in an ambient air condition. This phenomenon was caused by the absorbed polar components (i.e. oxygen and moisture) on the interface between OGIs and Soluble OSCs during the jetting process. For eliminating the polar component at the interface of OGI, the role of high vacuum seasoning on an OGI for all solution processable OTFTs were studied. Poly 4-vinly phenols (PVPs) were the material chosen as the organic gate dielectric, with a weakness in ambient air. The high vacuum seasoning of PVP's surface showed improved performance from non-seasoning TFT; a $V_{th}$, a ${\mu}_{fe}$ and a interface charge trap density from -8V, $0.018cm^2V^{-1}s^{-1}$, $1.12{\times}10^{-12}(cm^2eV)^{-1}$ to -4.02 V, $0.021cm^2V^{-1}s^{-1}$, $6.62{\times}10^{-11}(cm^2eV)^{-1}$. These results of OTFT device show that polar components were well eliminated by the high vacuum seasoning processes.

• Corrosion Science and Technology
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• 제7권1호
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• pp.40-44
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• 2008

Passive metal forms an interfacial diffuse layer on the surface of passive film by its reaction with $H^+$ or $OH^-$ ions in solution depending on solution pH. There is a critical pH, called pH point of iso-selectivity ($pH_{pis}$) at which the nature of the diffuse layer is changed from the anion-permeable at pH<$pH_{pis}$ to the cation-permeable at pH>$pH_{pis}$. The $pH_{pis}$ for a passivated Fe was determined by examining the effects of pH on the thickness of passive film and on the dissolution reaction occurring on the passive film under a gavanostatic reduction in borate-phosphate buffer solutions at various pH of 7~11. The steady-state thickness of passive film formed on Fe showed the maximum at pH 8.5~9, and further the nature of film dissolution reaction was changed from a reaction producing $Fe^{3+}$ ion at $pH\leq8.5$ to that producing $FeO_2{^-}$ at $pH\geq9$, suggesting that the $pH_{pis}$ of Fe is about pH 8.5~9. In addition, the passive film formed at pH 8.5~9, $pH_{pis}$, was found to be the most protective with the lowest defect density as confirmed by the Mott-Schottky analysis. Pitting potential was decreased with increasing $Cl^-$ concentration at $pH\leq8.5$ due probably to the formation of anion permeable diffuse layer, but it was almost constant at $pH\geq9$ irrespective of $Cl^-$ concentration due primarily to the formation of cation permeable diffuse layer on the film, confirming again that $pH_{pis}$ of Fe is 8.5~9.

• Journal of Magnetics
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• 제8권4호
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• pp.138-141
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• 2003

$Ni_{0.65}Zn_{0.35}Fe_2O_4$thin films were prepared by using a sol-gel method. Their crystallographic, dielectric and magnetic properties were investigated as a function of Cu contents by means of an X-ray diffractometer (XRD), X-ray reflectivity, LCZ meter (NF2232), a vibrating sample magnetometer (VSM), and an atomic force microscope (AFM). From typical C-V measurements for $Ni_{0.65}Zn_{0.35}Fe_2O_4$ thin films on p-type silicon substrate, the surface charge density was calculated as 1.4 ${\mu}$C/$m^2$. The dielectric constant evaluated from the capacitance at the accumulation state was 28. The high $H_{c}$ and low $M_{sat}$ at x=0.0 and 0.1 were due to the growth of the ${\alpha}$-$Fe_2O_3$ phase having antiferromagnetic properties. The rapidly decreased $H_{c}$ and increased $M_{sat}$ at x=0.2 and 0.3 can be explained that the ${\alpha}$-$Fe_2O_3$ phases have completely disappeared at x=0.3 and so, non-magnetic defects are minimized. The $M_{sat}$ was slightly decreased and the $H_{c}$ was increased above at x=0.3 because the increase of grain boundary due to smaller grain size acts as defects during magnetization process.