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K.-H. IM,N.-S. PARK,Y.-N. KIM,L.-Y. YANG 한국자동차공학회 2003 International journal of automotive technology Vol.4 No.4
This paper describes a method for a falling weight impact test to estimate the impact energy absorbing characteristics and impact strength of CFRP (Carbon-fiber reinforced plastics) laminate plates based on considerations of stress wave propagation theory, which were converted to measurements of load and displacement verses time. The delamination area of impacted specimens for the different ply orientations was measured with an ultrasonic C-scanner to determine the correlation between impact energy and delamination area. The energy absorbed by a quasi-isotropic specimen having four interfaces was higher than that of orthotropic laminates with two interfaces. The more interfaces, the greater the energy absorbed. The absorbed energy of a hybrid specimen embedding GFRP (Glass-fiber reinforced plastics) layer was higher than that of normal specimens. Also, a falling weight impact tester was built to evaluate the characteristics and impact strength of CFRPs.
Electrical conductivity enhancement of epitaxially grown TiN thin films
Khim Yeong Gwang,Park Beomjin,Heo Jin Eun,Khim Young Hun,Khim Young Rok,Gu Minseon,Rhee Tae Gyu,Chang Seo Hyoung,Han Moonsup,Chang Young Jun 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.82 No.5
Titanium nitride (TiN) presents superior electrical conductivity with mechanical and chemical stability and compatibility with the semiconductor fabrication process. Here, we fabricated epitaxial and polycrystalline TiN (111) thin flms on MgO (111), sapphire (001), and mica substrates at 640℃ and room temperature by using a DC sputtering, respectively. The epitaxial flms show less amount of surface oxidation than the polycrystalline ones grown at room temperature. The epitaxial flms show drastically reduced resistivity (~ 30 micro-ohm-cm), much smaller than the polycrystalline flms. Temperature-dependent resistivity measurements show a nearly monotonic temperature slope down to low temperature. These results demonstrate that high-temperature growth of TiN thin flms leads to signifcant enhancement of electrical conductivity, promising for durable and scalable electrode applications.
Khim, B.K.,Shim, J.,Yoon, H.I.,Kang, Y.C.,Jang, Y.H. Academic Press in association with the Estuarine a 2007 Estuarine, coastal and shelf science Vol.73 No.1-2
<P><B>Abstract</B></P><P>Particulate suspended material was recovered over a 23-month period using two sediment traps deployed in shallow water (∼30m deep) off the King Sejong Station located in Marian Cove of King George Island, West Antarctica. Variability in seasonal flux and geochemical characteristics of the sediment particles highlights seasonal patterns of sedimentation of both lithogenic (terrigenous) and biogenic particles in the coastal glaciomarine environment. All components including total mass flux, lithogenic particle flux and biogenic particle flux show distinct seasonal variation, with high recovery rates during the summer and low rates under winter fast ice. The major contributor to total mass flux is the lithogenic component, comprising from 88% during the summer months (about 21gm<SUP>−2</SUP>d<SUP>−1</SUP>) up to 97% during the winter season (about 2gm<SUP>−2</SUP>d<SUP>−1</SUP>). The lithogenic particle flux depends mainly on the amount of snow-melt (snow accumulation) delivered into the coastal region as well as on the resuspension of sedimentary materials. These fine-grained lithogenic particles are silt-to-clay sized, composed mostly of clay minerals weathered on King George Island. Biogenic particle flux is also seasonal. Winter flux is ∼0.2gm<SUP>−2</SUP>d<SUP>−1</SUP>, whereas the summer contribution increases more than tenfold, up to 2.6gm<SUP>−2</SUP>d<SUP>−1</SUP>. Different biogenic flux between the two summers indicates inter-annual variability to the spring–summer phytoplankton bloom. The maximum of lithogenic particle flux occurs over a short period of time, and follows the peak of biogenic particle flux, which lasts longer. The seasonal warming and sea-ice retreat result in change in seawater nutrient status and subsequent ice-edge phytoplankton production. Meanwhile, the meltwater input to Marian Cove from the coastal drainage in January to February plays a major role in transporting lithogenic particles into the shallow water environment, although the tidal currents may be the main agents of resuspension in this kind of sheltered bay.</P>
Control of Threshold Voltage for Top-Gated Ambipolar Field-Effect Transistor by Gate Buffer Layer
Khim, Dongyoon,Shin, Eul-Yong,Xu, Yong,Park, Won-Tae,Jin, Sung-Ho,Noh, Yong-Young American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.27
<P>The threshold voltage and onset voltage for p-channel and n-channel regimes of solution-processed ambipolar organic transistors with top-gate/bottom-contact (TG/BC) geometry were effectively tuned by gate buffer layers in between the gate electrode and the dielectric. The work function of a pristine Al gate electrode (-4.1 eV) was modified by cesium carbonate and vanadium oxide to 2.1 and 5.1 eV, respectively, which could control the flat -band voltage, leading to a remarkable shift of transfer curves in both negative and positive gate voltage directions without any side effects. One important feature is that the mobility of transistors is not very sensitive to the gate buffer layer. This method is simple but useful for electronic devices where the threshold voltage should be precisely controlled, such as ambipolar circuits, memory devices, and light -emitting device applications.</P>
Khim, Boo-Keun,Yoon, Ho-Il,Kang, Cheon-Yun,Zhao, Junlin Korea Institute of Ocean ScienceTechnology 2004 Ocean and Polar Research Vol.26 No.3
A sediment core drilled from Lake langer on King George Island was analyzed for a variety of textural md geochemical properties along with $^{14}C$ age dates. These data were combined with published records of other cores to provide a detailed history of Holocene variation of total organic carbon (TOC) contents with respect to terrestrial paleoclimate change. The lithologic contrast of the lower diamicton and upper fine-grained sediments shows the glacier activity and subsequent lake formation. Low TOC contents fluctuated during the diamicton deposition whereas the increase of TOC began with the lake formation during the postglacial period that started about 5,000 yr B.p More notable are the distinct TOC peaks that may imply enhanced primary productivity during the warm period. The uniform and low TOC contents may reflect the limited productivity during the evolution of the lake. However, the recent TOC readvance clearly indicates gradual warming on King George Island. However, the paleoclimatic signature in the terrestrial lake environment during the Holocene seems to be subtle and less distinct, compared to the marine environment.
On the Structure of the AGN Torus through the Fraction of Optically Selected Type 1 AGNs
Khim, Honggeun,Yi, Sukyoung K. American Astronomical Society 2017 The Astrophysical journal Vol.846 No.2
<P>The ratio in number between unobscured (type 1) and obscured (type 2) active galactic nuclei (AGNs) is often used to explore the structure of the torus in the unified scheme for AGNs. Oh et al. (2015) investigated the type 1 AGN fraction on two-dimensional space in terms of black hole mass (M-BH) and bolometric luminosity (L-bol) and found that the fraction changes depending on both M-BH and L-bol, forming a ridge-shaped distribution. In this study, based on the up-to-date type 1 AGN catalog of Oh et al. (2015), we examine how the trend of the type 1 AGN fraction in the M-BH-L-bol plane is affected by the different methods used to derive M-BH and L-bol, and suggest an analytic model to explain the observations. We use galaxies from the Sloan Digital Sky Survey Data Release 7 in the redshift range 0.01 <= z <= 0.2. In estimating L-bol, we employ two different methods using [O III] and/or [O I] emission lines, and find that the L-bol values obtained from the two methods agree well. We consider the M-BH-s* relation, the M-BH-L-bulge relation, and the single-epoch H alpha-based M-BH estimate in calculating M-BH. We find that the trends of the type 1 AGN fraction with respect to M-BH and L-bol are similar for the different methods of deriving L-bol but different when using different methods to derive M-BH. We present a model based on the clumpy-torus scheme that reproduces the ridge-shaped distribution of the fraction parallel to the iso-Eddington ratio lines.</P>