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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, Dongyoon,Baeg, Kang-Jun,Kim, Juhwan,Yeo, Jun-Seok,Kang, Minji,Amegadzea, Paul S. K.,Kim, Mu-Gyeom,Cho, Joonhyuk,Lee, Jung Hun,Kim, Dong-Yu,Noh, Yong-Young The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.33
<P>Here we report the effects of a Cs-salt based charge injection interlayer on the characteristics of top-gate/bottom-contact (TG/BC) ambipolar polymer OFETs with poly(thienylenevinylene-co-phthalimide)s functionalized at the imide nitrogen with dodecyl (PTVPhI-C12). P-channel dominant PTVPhI-C12 ambipolar OFETs showed both an improved electron injection and blocked hole injection properties by insertion of a thermally deposited thin CsF interlayer between Au source/drain electrodes and the organic semiconductor. X-ray and UV photoelectron spectroscopy results exhibited that the work-function of the Au electrode progressively changed from −4.5 eV to −3.9 eV and the Fermi levels of PTVPhI-C12 concomitantly moved towards the LUMO level of the conjugated polymer with an increase of CsF thickness from 0 nm to 1.5 nm, respectively. Both the shifting of Au work-function and the molecular doping of PTVPhI-C12 by insertion of CsF provide an order of magnitude improved n-channel properties in p-channel dominant ambipolar PTVPhI-C12 OFETs. In the end, the characteristics of the PTVPhI-C12 complementary inverter were improved (gain > 23) by a selective deposition and optimization of the CsF interlayer thickness on the n-channel region of ambipolar CMOS inverters.</P> <P>Graphic Abstract</P><P>Here we report the effects of a Cs-salt based charge injection interlayer on the characteristics of top-gate/bottom-contact ambipolar polymer OFETs. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm32721j'> </P>
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>
Analysis of 5-DOF Motion Errors Influenced by the Guide Rails of an Aerostatic Linear Motion Stage
Khim, Gyungho,Oh, Jeong Seok,Park, Chun Hong 한국정밀공학회 2014 International Journal of Precision Engineering and Vol.15 No.2
This paper presents an estimation method for five-degrees-of-freedom (5-DOF) motion errors, which are influenced by the profiles of guide rails of an aerostatic linear motion stage. The transfer function, which is the relationship between the magnitude of the rail form error and the reaction force of a bearing pad, was introduced to simplify and systematize the estimation of the motion errors. The motion errors were calculated from the equilibrium conditions for the forces and moments of the stage using the geometrical relationships between the bearing pads, the transfer function, and rail form errors. Experimental verification of the rail form error was carried out using a porous aerostatic linear motion stage and the mixed sequential two-probe method. The aerostatic feed table of the experimental stage, on which sensors were mounted, was also used as the feed unit for measuring the rail profiles. The 5-DOF motion errors were estimated from the measured rail form errors using the transfer function method. The estimated results were in good agreement with the experiments.
Study on Energy Balance at the Operating Points of Staged Combustion Cycle LRE
Khim Boh Yeon,문인상 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.5
In the present research, liquid rocket engine (LRE) balancing was performed at the design and the off-design points to confirm the characteristics for a 9-tonf staged combustion cycle LRE whose propellant consists of LOx/kerosene. When an LRE is designed, basic specifications, such as combustion pressure and O/F ratio, are predetermined and the corresponding balancing values are decided. Nevertheless, an engine may run over a nominal point in actual operation. Thrust control valve (THCV) and O/F ratio control valve (OFCV) are activated to adjust the engine status in real operation whenever an engine runs out of the design point. The engine power balancing requires thermophysical properties of the LOx and the kerosene for the combustion process and those were adopted from the CEA, which is an open-source code written by NASA. Also, MATLAB was employed and symbolic generation and numeric calculation was proposed to help set up the governing system and to reduce computational load. The off-design points were suggested to be set at ± 7%, ± 5%, ± 3% variance range from the nominal combustion pressure and the O/F ratio. It has been derived from the results that the required power of the pump was greatest at OD3 while least at OD1. If the combustion pressure is higher than DP, the THCV pressure difference should be set lower than DP. If the O/F ratio is higher than DP, the OFCV pressure difference should be set higher than DP. When the combustion pressure is over 100 bar, the TIT is over 700 K. It should be taken carefully in this section for turbine safety.
Khim, Dongyoon,Han, Hyun,Baeg, Kang‐,Jun,Kim, Juhwan,Kwak, Sun‐,Woo,Kim, Dong‐,Yu,Noh, Yong‐,Young WILEY‐VCH Verlag 2013 ADVANCED MATERIALS Vol.25 No.31
<P><B>Large‐area polymer FET arrays and integrated circuits (ICs)</B> are successfully demonstrated via a simple wire‐bar–coating process. Both a highly crystalline conjugated polymer layer and very smooth insulating polymer layer are formed by a consecutive wire‐bar–coating process on a 4‐inch plastic substrate with a short processing time for application as the active and dielectric layers of OFET arrays and ICs.</P>