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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, Boo-Keun,Sakamoto, Tatsuhiko,Harada, Naomi Elsevier 2012 Deep-sea research. Part II, Topical studies in oce Vol.61 No.-
<P><B>Abstract</B></P><P>Core GC9A, a 6.7m long gravity core collected from the central region of the Okhotsk Sea during Cruise YK0712 on R/V Yokosuka (JAMSTEC), was used to reconstruct the changes in surface water conditions by measuring biogenic components (biogenic opal, CaCO<SUB>3</SUB>, total organic carbon and <I>δ</I><SUP>15</SUP>N of sediment organic matter) of sediment samples. The age of Core GC9A was determined indirectly by graphic correlation comparing the b<SUP>⁎</SUP> (psychometric yellow–blue chromaticness) values with those of well-dated Core MD01-2415, with complement to the tephra layer (K3; 50ka). The bottom age of Core GC9A was estimated to be about 180kyr; therefore it provides the history of surface water conditions from MIS 1 to MIS 6. The biogenic opal, CaCO<SUB>3</SUB>, and TOC contents were high during the interglacial periods as expected, indicating enhanced surface water production under warm climatic conditions. This condition resulted from sufficient nutrient supply to the surface waters by active vertical mixing, which was validated by low δ<SUP>15</SUP>N values of the sediment organic matter. In contrast, surface water productivity was depressed during the colder glacial periods, probably due to the expanded sea-ice distribution and limited nutrient supply. However, the glacial sediments had moderately high δ<SUP>15</SUP>N values, indicating enhanced nitrate utilization resulting from the limited nutrient supply caused by strong stratification of the surface water. High δ<SUP>15</SUP>N values were also observed during the deglaciation, which was attributed to the increased nitrate utilization during enhanced surface water productivity. However, the low δ<SUP>15</SUP>N values during the glacial and deglacial periods may be attributed to the increased supply of terrestrial organic matter. Diatom production was primarily responsible for surface water paleoproductivity during the interglacial periods rather than coccolithophores. However, the succession of glacial to early deglacial coccolithophore production and late deglacial to interglacial diatom production was remarkable, corresponding to the present-day seasonal phytoplankton succession. Such an advanced coccolithophore production relative to diatom production might be attributed to the degree of nutrient availability associated with surface water conditions on the basis of variations in the δ<SUP>15</SUP>N value. Finally, the opal and TOC contents decreased abruptly in conjunction with a gradual decrease in CaCO<SUB>3</SUB> content from about 2ka, which seems to implicate a late Holocene sudden decrease in paleoproductivity in the central region of the Okhotsk Sea. According to the increase in δ<SUP>15</SUP>N values during this interval, nutrient availability appears to be poor, which is likely attributed to the resumed strong stratification that occurred due to the southward shift of the Aleutian Low atmospheric pressure system.</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.
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.
Khim, Boo-Keun,Je, Jong-Geel,Han, Sang-Joon,Woo, Kyung-Sik,Park, Yong-Ahn 한국패류학회 1998 The Korean Journal of Malacology Vol.14 No.1
동해 연안에서 채취된 뷔나스백합(Mercenaria stimpsoni)의 연령과 성장률을 이매패의 표면에서 확인된 연륜과 이매패 각질에서 분석된 산소동위원소비의 성장에 따른 변화를 이용하여 비교하였다. 뷔나스백합의 산소동위원소상은 일련의 주기적인 변화를 뚜렷하게 보여주며 이러한 변화진폭은 이매패가 성장한 해수의 온도변화에 일차적으로 제어된다. 산소동위원소상의 주기화 연륜의 관계로부터 뷔나스백합의 연륜이 해마다 여름철에 형성됨을 보여준다. 해수 온도의 계절적 변화와 산소동위원소비에서 얻어진 예측 온도와의 비교로부터, 뷔나스백합은 겨울철에 성장이 멈추는 것으로 사료된다. 또한 산소도위원소비는 뷔나스백합의 성장에 따른 전형적인 노화현상을 보여준다. 따라서 이매패가 성장하는 해수의 물리화학적 조건에 의해 제어되는 산소동위원소비는 뷔나스백합의 경우 연령과 성장률을 측정하는 독립적인 시간 척도가 될 수 있다.