• 제목/요약/키워드: K3 surface

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Numerical Simulation of Tribological Phenomena Using Stochastic Models

  • Shimizu, T.;Uchidate, M;Iwabuchi, A.
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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    • pp.235-236
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    • 2002
  • Tribological phenomena such as wear or transfer are influenced by various factors and have complicated behavior. Therefore, it is difficult to predict the behavior of the gribological phenomena because of their complexity. But, those tribological phenomena can be considered simply as to transfer micro material particles from the sliding interface. Then, we proposed the numerical simulation method for tribological phenomena such as wear of transfer using stochastic process models. This numerical simulation shows the change of the 3-D surface topography. In this numerical simulation, initial 3-D surface toughness data are generated by the method of non-causal 2-D AR (autoregressive) model. Processes of wear and transfer for some generated initial 3-D surface data are simulated. Simulation results show successfully the change of the 3-D surface topography.

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The Effects of LaF3 Coating on the Electrochemical Property of Li[Ni0.3Co0.4Mn0.3]O2 Cathode Material

  • Yun, Su-Hyun;Kim, Seuk-Buom;Park, Yong-Joon
    • Bulletin of the Korean Chemical Society
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    • 제30권11호
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    • pp.2584-2588
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    • 2009
  • The effect of $LaF_3$ coating on the structural and electrochemical properties of $Li[Ni_{0.3}Co_{0.4}Mn_{0.3}]O_{2}$ cathodes was investigated using XRD, SEM, TEM, and a cycler. The coating layer consisted of nano-sized particles attached nonuniformly to the surface of pristine powder. Despite the surface coating treatment, phase difference by $LaF_3$ coating was not detected. The discharge capacities of coated electrodes were a little lower than that of pristine sample at a 1 C rate. However, as the C rate increases, the capacity retention of the coated sample becomes obviously superior to that of the pristine sample. The cyclic performances of the electrodes in the voltage range of 4.8 $\sim$ 3.0 V were also improved by the surface coating. Such enhancement is attributed to the presence of the $LaF_3$ coating layer, which effectively suppressd the reaction between electrodes and electrolytes on the surface of the $Li[Ni_{0.3}Co_{0.4}Mn_{0.3}]O_{2}$ electrode.

Growth of Al2O3/Al Composite by Directed Metal Oxidation of Al Surface Doped with Sodium Source

  • Park, Hong Sik;Kim, Dong Seok;Kim, Do Kyung
    • 한국세라믹학회지
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    • 제50권6호
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    • pp.439-445
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    • 2013
  • Both an unreinforced $Al_2O_3$/Al matrix and a ${\alpha}-Al_2O_3$ particulate reinforced composite have been produced by the oxidation of an Al surface doped with NaOH in the absence of any other dopant. Fabrication of the matrix was initiated by the formation of $NaAlO_2$, which provides a favorable surface structure for the matrix formation by breaking the protective $Al_2O_3$ layer on Al. During the matrix growth, the external surface of the growth front was covered with a very thin sodium-rich oxide. A cyclic formation process of the sodium-rich oxide on the growth surface was proposed for the sodium-induced directed metal oxidation process. This process involves dissolution of the sodium-rich oxide, motion of Na to the growth front, and re-formation of the oxide on the surface. Near-net-shape composites were fabricated by infiltrating an $Al_2O_3$/Al matrix into a ${\alpha}-Al_2O_3$ particulate preform, without growth barrier materials. The infiltration distance increased almost linearly in the NaOH-doped preform.

Derivation of Surface Temperature from KOMPSAT-3A Mid-wave Infrared Data Using a Radiative Transfer Model

  • Kim, Yongseung
    • 대한원격탐사학회지
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    • 제38권4호
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    • pp.343-353
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    • 2022
  • An attempt to derive the surface temperature from the Korea Multi-purpose Satellite (KOMPSAT)-3A mid-wave infrared (MWIR) data acquired over the southern California on Nov. 14, 2015 has been made using the MODerate resolution atmospheric TRANsmission (MODTRAN) radiative transfer model. Since after the successful launch on March 25, 2015, the KOMPSAT-3A spacecraft and its two payload instruments - the high-resolution multispectral optical sensor and the scanner infrared imaging system (SIIS) - continue to operate properly. SIIS uses the MWIR spectral band of 3.3-5.2 ㎛ for data acquisition. As input data for the realistic simulation of the KOMPSAT-3A SIIS imaging conditions in the MODTRAN model, we used the National Centers for Environmental Prediction (NCEP) atmospheric profiles, the KOMPSAT-3Asensor response function, the solar and line-of-sight geometry, and the University of Wisconsin emissivity database. The land cover type of the study area includes water,sand, and agricultural (vegetated) land located in the southern California. Results of surface temperature showed the reasonable geographical pattern over water, sand, and agricultural land. It is however worthwhile to note that the surface temperature pattern does not resemble the top-of-atmosphere (TOA) radiance counterpart. This is because MWIR TOA radiances consist of both shortwave (0.2-5 ㎛) and longwave (5-50 ㎛) components and the surface temperature depends solely upon the surface emitted radiance of longwave components. We found in our case that the shortwave surface reflection primarily causes the difference of geographical pattern between surface temperature and TOA radiance. Validation of the surface temperature for this study is practically difficult to perform due to the lack of ground truth data. We therefore made simple comparisons with two datasets over Salton Sea: National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory (JPL) field data and Salton Sea data. The current estimate differs with these datasets by 2.2 K and 1.4 K, respectively, though it seems not possible to quantify factors causing such differences.

RBM 표면 임플란트와 산부식 표면 임플란트의 3년 생존율에 대한 비교 연구 (3-Year Survival Analysis of RBM and Acid-Etched Surface Implants)

  • 윤대웅;김문섭;장한성;진수영;마득현;정경달;박현춘;김희중;김학균
    • 구강회복응용과학지
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    • 제27권4호
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    • pp.393-403
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    • 2011
  • 이 연구의 목적은 임상적으로 사용되는 RBM과 산부식 임플란트의 3년 생존율을 비교, 분석하기 위한 것이다. 총 152개의 RBM 임플란트를 식립하였고, 이 중 1개의 임플란트에서 실패가 발생하였는데, 원인은 식립체의 파절이었다. 또한 총 152개의 산부식 표면 임플란트를 식립하였는데, 이 중 7개의 임플란트에서 실패를 하였으며, 원인으로는 과열, 감염, 초기고정 불량 등이었다. RBM 임플란트의 생존율은 99.34%, 산부식 임플란트의 생존율은 95.39%로 두 가지 임플란트 모두 양호한 생존율을 보였으나, RBM 임플란트에서 다소 높은 생존율을 나타내었다.

HELICOIDAL SURFACES AND THEIR GAUSS MAP IN MINKOWSKI 3-SPACE

  • Choi, Mie-Kyung;Kim, Young-Ho;Liu, Huili;Yoon, Dae-Won
    • 대한수학회보
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    • 제47권4호
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    • pp.859-881
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    • 2010
  • The helicoidal surface is a generalization of rotation surface in a Minkowski space. We study helicoidal surfaces in a Minkowski 3-space in terms of their Gauss map and provide some examples of new classes of helicoidal surfaces with constant mean curvature in a Minkowski 3-space.

A study on the coating of silver nanoparticles on fabric surfaces with 3-Mercaptopropyltrimethoxysilane(MPTMS)

  • Park, Jeong-Eun;Jung, Da-Un;Lee, Jae-Woong;Kim, Sam-Soo
    • 한국염색가공학회:학술대회논문집
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    • 한국염색가공학회 2009년도 학술발표대회
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    • pp.110-111
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    • 2009
  • A solution containing 3-Mercaptopropyltr-imethoxysilane(MPTMS) was employed to modify surface of cotton fabrics with a silver colloid. Silver nanoparticles were applied on cotton fabrics via treatment with 3-MPTMS. The rate of silver nanoparticles on the fabric surface were measured with Energy Dispersive Spectroscopy(EDS). EDS results confirm the silver atom on the cotton surface.

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수용액 내 캐올리나이트와 할로이사이트의 표면화학 특성: 표면복합반응 모델링 (Surface Chemical Properties of Aqueous Kaolinite and Halloysite: Surface Complexation Modeling)

  • 장세정;김수진
    • 한국광물학회지
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    • 제17권2호
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    • pp.157-168
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    • 2004
  • 수용액 내 캐올리나이트와 할로이사이트의 표면화학 특성을 전위차 적정 실험과 FITEQL3.2 프로그램을 이용하여 연구하였다. 표면복합반응 모델 중 일정용량 모델을 적용하였으며, 표면을 사면체 자리와 팔면체 자리로 나누어 설정한 2 sites - 3 $pK_{a/s}$ 모델은 캐올리나이트와 할로이사이트의 표면화학 특성을 설명하는데 적합하였다. 두 점토광물 표면은 pH 4 이상에서 음전하를 띄며 pH가 높아질수록 양성자 표면 전하 밀도는 낮아진다. 산성 및 중성 영역에선 Si 사리(≡$SiO^{-}$ )가, 염기성 영역에선 Al 자리(≡$AlO^{-}$)가 양이온을 흡착하는데 중요한 역할을 할 것으로 예상된다. 모델링 결과 캐올리나이트의 경우 $pK_{a2(si)}$ /$^{int}$, p $K_{al(Al) }$ /$^{int}$ /, $pK_{a2}$ $(Al)^{int}$ /는 각각 4.436. 4.564, 및 8.461이며, 할로이사이트의 경우는 각각 7.852, 3.885, 7.084이다. 캐올리나이트의 총 Si 표면자리 농도와 총 Al 표면자리 농도는 0.215와 0.148 mM이며, 할로이사이트의 경우는 0.357과 0.246 mM이다 두 광물 모두 Si 표면자리 밀도 : Al 표면자리 밀도가 1 : 0.69로 비슷하다. 캐올리나이트의 총 표면자리 밀도는 3.774 sites/$nm^2$로 할로이사이트의 2.292 sites/n $m^2$ 값보다 약 1.6배정도 높다.다.

Multinuclear Solid-state NMR Investigation of Nanoporous Silica Prepared by Sol-gel Polymerization Using Sodium Silicate

  • Kim, Sun-Ha;Han, Oc-Hee;Kim, Jong-Kil;Lee, Kwang-Ho
    • Bulletin of the Korean Chemical Society
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    • 제32권10호
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    • pp.3644-3649
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    • 2011
  • Multinuclear solid-state nuclear magnetic resonance (NMR) experiments were performed to investigate the local structure changes of nanoporous silica during hydrothermal treatment and surface modification with 3-aminopropyltriethoxysilane (3-APTES). The nanoporous silica was prepared by sol-gel polymerization using inexpensive sodium silicate as a silica precursor. Using $^1H$ magic angle spinning (MAS) NMR spectra, the hydroxyl groups, which play an important role in surface reactions, were probed. Various silicon sites such as $Q^2$, $Q^3$, $Q^4$, $T^2$, and $T^3$ were identified with $^{29}Si$ cross polarization (CP) MAS NMR spectra and quantified with $^{29}Si$ MAS NMR spectra. The results indicated that about 25% of the silica surface was modified. $^1H$ and $^{29}Si$ NMR data proved that the hydrothermal treatment induced dehydration and dehyroxylation. The $^{13}C$ CP MAS and $^1H$ MAS NMR spectra of 3-APTES attached on the surface of nanoporous silica revealed that the amines of the 3-aminopropyl groups were in the chemical state of ${NH_3}^+$ rather than $NH_2$.