A STUDY ON IMPACT CHARACTERISTICS OF THE STACKING SEQUENCES IN CFRP COMPOSITES SUBJECTED TO FALLING-WEIGHT IMPACT LOADING

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.

Chemical-, site-, and taxa-dependent benthic community health in coastal areas of the Bohai Sea and northern Yellow Sea: A sediment quality triad approach

Khim, Jong Seong,Park, Jinsoon,Song, Sung Joon,Yoon, Seo Joon,Noh, Junsung,Hong, Seongjin,Kwon, Bong-Oh,Ryu, Jongseong,Zhang, Xiaowei,Wang, Tieyu,Lu, Yonglong,Giesy, John P. Elsevier 2018 The Science of the total environment Vol.645 No.-

<P><B>Abstract</B></P> <P>To investigate benthic ecological quality associated with coastal pollution in the Bohai Sea and northern Yellow Sea, a sediment quality triad (SQT) approach was applied. Chemical (six groups of persistent toxic substances (PTSs) and 8 metals and metalloids), toxicological (AhR-mediated potency), and ecological (bacterial and meiofaunal communities) elements were selected and used in an integrated sediment assessment. The benthic meiofaunal community was newly analyzed and used as an additional component of the infaunal community during the SQT. Concentrations of chemicals and potential toxicity in sediments both indicated moderate to severe pollution in the study area, characterized by site-specific and land-uses. In particular, As, DDTs, and bioassay-derived dioxin equivalents exceeded corresponding sediment quality guidelines at nearly all locations. Limited occurrences of meiofaunal taxa (mean = 5.2) and relatively low species diversity, mainly comprised of nematodes (75.3%) and copepods (14.6%), among locations was generally consistent with pollution. The benthic community was consistent with compound-specific responses to gradients of contamination, particularly for As. Densities of two taxa, Nematoda and Nemertea exhibited strong negative correlations with concentrations of As. Compound-, site-, and taxa-specific variability of pollution of sediments was further supported by results of cluster analysis (CA) and nonmetric multidimensional scaling (NMDS). Finally, assessment integrating five benthic quality elements, including: 1) PTSs; 2) metals and metalloids; 3) sediment toxicity; 4) sediment microbiome; and 5) benthic meiofaunal community, explained contamination of sediments associated with land-uses, locality, or habitat. Status of the benthic community could not be explained by single component and their associations were not quantitative. Results of the integrated assessment, considering multiple benthic quality elements were useful to address overall quality of sediment, and were consistent with chemical-, species-, or site-dependent pollution of sediments in the Bohai and Yellow Seas.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Extended-sediment quality triad was applied to enhance typical benthic assessment. </LI> <LI> Sediment toxicity might be over- or under-estimate chemical pollution and benthic health. </LI> <LI> Meiofaunal abundance would be a good ecological indicator of pollution by arsenic. </LI> <LI> Moderate to severe pollution evidenced in over half of the sampling locations. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

δ¹³C and δ¹⁵N Values of Sediment-trap Particles in the Japan and Yamato Basins and Comparison with the Core-top Values in the East/Japan Sea

Khim, Boo-Keun,Otosaka, Shigeyoshi,Park, Kyung-Ae,Noriki, Shinichiro Korean Ocean Research & Development Institute and 2018 OCEAN SCIENCE JOURNAL Vol.53 No.1

Investigation of sediment-trap deployments in the East/Japan Sea (EJS) showed that distinct seasonal variations in particulate organic carbon (POC) fluxes of intermediate-water sediment-traps clearly corresponded to changes in chlorophyll <TEX>${\alpha}$</TEX> concentrations estimated from SeaWiFS data. The prominent high POC flux periods (e.g., March) were strongly correlated with the enhanced surface-water phytoplankton blooms. Deep-water sediment-traps exhibited similar variation patterns to intermediate-water sediment-traps. However, their total flux and POC flux were higher than those of intermediate-water sediment-traps during some months (e.g., April and May), indicating the lateral delivery of some particles to the deep-water sediment-traps. Distinct seasonal <TEX>${\delta}^{13}C$</TEX> and <TEX>${\delta}^{15}N$</TEX> variations in settling particles of the intermediate-water sediment-traps were observed, strongly supporting the notion of seasonal primary production. Seasonal variations in <TEX>${\delta}^{13}C$</TEX> and <TEX>${\delta}^{15}N$</TEX> values from the deep-water sediment-traps were similar to those of the intermediate-water sediment-traps. However, the difference in <TEX>${\delta}^{13}C$</TEX> and <TEX>${\delta}^{15}N$</TEX> values between the intermediate-water and the dee-pwater sediment-traps may be attributed to degradation of organic matter as it sank through the water column. Comparison of flux-weighted <TEX>${\delta}^{13}C$</TEX> and <TEX>${\delta}^{15}N$</TEX> mean values between the deep-water sediment-traps and the core-top sediments showed that strong selective loss of organic matter components (lipids) depleted in <TEX>$^{13}C$</TEX> and <TEX>$^{15}N$</TEX> occurred during sediment burial. Nonetheless, the results of our study indicate that particles in the deep-water sediment-trap deposited as surface sediments on the seafloor preserve the record of surface-water conditions, highlighting the usefulness of sedimentary <TEX>${\delta}^{13}C$</TEX> and <TEX>${\delta}^{15}N$</TEX> values as a paleoceanographic application in the EJS.

Surface water productivity and sediment transport by Bering Strait throughflow in the Chukchi Shelf (the western Arctic Ocean) during the Holocene

Khim, Boo-Keun,Lee, Mi Jung,Cho, Hyen Goo,Park, Kwangkyu SAGE Publications 2018 The Holocene Vol.28 No.5

A comparative review and analysis of tentative ecological quality objectives (EcoQOs) for protection of marine environments in Korea and China

Khim, Jong Seong,Hong, Seongjin,Yoon, Seo Joon,Nam, Jungho,Ryu, Jongseong,Kang, Seong-Gil Elsevier Science B.V., Amsterdam. 2018 Environmental pollution Vol.242 No.no.pb

A Vacuum-Compatible Air Bearing: Design Analysis and Optimization

Khim, G.H.,Park, Chun Hong,Lee, H.S.,Kim, S.W. Trans Tech Publications, Ltd. 2007 Key Engineering Materials Vol.339 No.-

<P>This paper describes the vacuum-compatible air bearing designed with a cascaded exhaust scheme to minimize the leakage of air in a vacuum environment. The design of the air bearing, including the differential exhaust system, required great care because several design parameters, such as the number of exhaust stages, diameter and length of the exhaust tube, pumping speed and ultimate pressure of the vacuum pump, and seal length and gap greatly influenced the leakage of air and thus the degree of vacuum. A leakage analysis was performed to estimate the chamber pressure and an optimization method based on the genetic algorithm was proposed under several constraint conditions. The results showed that the degree of vacuum improved dramatically compared to the initial design, and that the distribution of the spatial design parameters and technical limit of the pumping speed were well achieved.</P>

Mahatma's Struggle for Human Rights - Spirit of Our Epoch -

Khim, Suk-jin 한인문화연구원 2000 한인문화논총 Vol.14 No.-

Sediment properties of lithologic units and their correlation within the lower delta plain of the Nakdong River Delta, southeast Korea

Khim, Boo-Keun,Shin, Seungwon,Kim, Jin Cheul,Takata, Hiroyuki,Hyun, Sangmin,Cheong, Daekyo Elsevier 2019 QUATERNARY INTERNATIONAL Vol.519 No.-

<P><B>Abstract</B></P> <P>Multi-proxy sediment properties reveal that three cores (ND-01, ND-02, and ND-03) from the lower delta plain of the Nakdong River Delta, southeast Korea, are characterized by the same stratigraphic lithologic successions consisting of a upper sand unit (10–15 m thick and <1 ka), a middle mud unit (∼20 m thick and 1–9 ka), a lower sand unit (6–9 m thick and 9–10 ka), and a lower mud unit (10–15 m thick and >10 ka) overlying weathered gravelly fluvial sediments and weathered bedrock. The sediment properties of each lithologic unit are controlled by the balance between the marine influence from Holocene sea level rise and the freshwater influence from Nakdong River discharge. In particular, the middle mud unit is characterized by distinct peaks in CaCO<SUB>3</SUB> content, P/T ratios (the ratio of planktonic foraminifera to the sum of benthic and planktonic foraminifera), total organic carbon and total nitrogen contents, and δ<SUP>13</SUP>C<SUB>org</SUB> values at 7–8 ka, which indicates that the maximum marine forcing during the sea level rising and the greatest influence of the Tsushima Warm Current during the evolution of the river-mouth coastal depositional system from an estuarine to a deltaic environment. Although the vertical stacking of lithologic successions is stratigraphically consistent within the lower delta plain, the precise temporal evaluation and comprehensive depositional evolution in the Nakdong River Delta including the upper delta plain and the prodelta zones remain a topic of future investigation.</P>

Graphical Displays for Multiple Comparisons

khim,Seong-Yeon 東亞大學校 經營問題硏究所 1985 經營論叢 Vol.8 No.-

관찰대상이 되는 경영현상에 있어서, 모집단이 일정한 기준에 의해 몇몇의 부모집단으로 분할되어 어떤 성질이 그 각각의 부모집단에서 동일한 정도로 현현하느냐에 연구촛점이 맞추어 질 경우(가령 어떤 상품의 대학 학년에 따른 선호도 차이의 문제 또는 A, B, C, 각각의 생산라인에서 산출된 제품의 불량품율의 차이에 관한 문제 등등) 그 동일성 문제의 검정에 관한 통계적 처리를 도표화함으로써 일목요연하게 그 결과를 파악할 수 있게끔 하는 평균비교의 도표화 과정에 관한 논문이다. 즉 이를 엄밀히 표현하면 일원배치에 있어서 k개의 수준에서의 평균을 비교하기 위한 도표화 과정에 관한 고찰이다. 반복수가 다른 일원배치의 평균비교에 있어서는 튜키-크래머 방법(Tukey-Kramer Method)을 직접 적용하여 도표화하기는 불가능하므로, 그것을 중심으로 1) 단순보존적인 과정(simple conservative procedure)과 2) 가브리엘-제바의 변형과정(Gabriel-Gheva modified simple conservative procedure) 그리고 3) 최량보존적인 과정(the best conservative procedure)에 의한 접근으로부터 구한 도표화 과정을 상호 비교하여 보았다. 그 결과 단순성에 있어서는 1), 2), 3)의 순서로 우월하였으며 정도(precision)에 있어서는 그 역순이었다.