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.

Oxygen Isotope Profile and Age Determination of venus Clam Mercenaria stimpsoni (Bivalvia: Veneridae) from the East Sea

Khim, Boo-Keun,Je Jong-Geel,Han, Sang-Joon,Woo, Kyung-Sik,Park, Yong-ahn 江原大學校 附設 環境硏究所 1999 環境硏究 Vol.16 No.-

동해 연안에서 채취된 뷔나스백합(Mercenaria stimpsoni)의 연령과 성장률을 이매패의 표면에서 확인된 연륜과 이매패 각질에서 분석된 산소동위원소비의 성장에 따른 변화를 이용하여 비교 하였다. 뷔닉스백합의 산소동위원소상은 일련의 주기적인 변화를 뚜렷하게 보여주며 이러한 변화 진폭은 이매패가 성장한 해수의 온도변화에 일차적으로 제어된다. 산소동위원소상의 주기와 연륜의 관계로부터 뷔나스백합의 연륜이 해마다 여름철에 형성됨을 보여준다. 해수 온도의 계절적 변화와 · 산소 동위원소비에서 얻어진 예측 온도와의 비교로부터, 뷔나스백합은 겨울철에 성장이 멈추는 것으로 사료된다. 또한 산소동위원소비는 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.

High Performance and Stable N-Channel Organic Field-Effect Transistors by Patterned Solvent-Vapor Annealing

Khim, Dongyoon,Baeg, Kang-Jun,Kim, Juhwan,Kang, Minji,Lee, Seung-Hoon,Chen, Zhihua,Facchetti, Antonio,Kim, Dong-Yu,Noh, Yong-Young American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.21

<P>We report the fabrication of high-performance, printed, <I>n</I>-channel organic field-effect transistors (OFETs) based on an <I>N</I>,<I>N</I>-dialkyl-substituted-(1,7&1,6)-dicyanoperylene-3,4:9,10-bis(dicarboximide) derivative, PDI-RCN2, optimized by the solvent-vapor annealing (SVA) process. We performed a systematic study on the influence of solubility and the chemical structure of a solvent used for the SVA process on the ordering and orientation of PDI-RCN2 molecules in the thin film. The PDI-RCN2 film showed improved crystallinity under vapor annealing with the aliphatic 1,2-dichloroethane (DCE) as a marginal solvent. The <I>n</I>-type OFETs with DCE-vapor-annealed PDI-RCN2 show highly improved charge-carrier mobility of ∼0.5 cm<SUP>2</SUP> V<SUP>–1</SUP> s<SUP>–1</SUP> and higher stability under gate bias stress than the pristine OFETs. This large performance improvement was mainly attributed to increased crystallinity of the semiconductor thin film, enhancing π–π stacking. We also introduced a new method to pattern crystallinity of a certain region in the semiconducting film by selective exposure to the solvent vapor using a shadow mask. The crystal-patterned PDI-RCN2 OFETs exhibit decreased off-currents by ∼10× and improved gate bias stability by minimizing crosstalk, reducing leakage current between devices, and reducing the density of charge trap states of the organic semiconductor.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-21/am4029075/production/images/medium/am-2013-029075_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am4029075'>ACS Electronic Supporting Info</A></P>

Efficiency of Empirical Estimator in Estimating Pr(X₁< Y < X₂)

Khim,Seong-yeon 東亞大學校 大學院 1986 大學院論文集 Vol.11 No.-

서로 독립인 分布旣知의 스트레스 확률변수 사이에 스트레스와는 독립인 分布未知인 스트레스 확률변수가 놓여 잇을 확률에 대한 經驗的 推定量의 效率性을 最尤推定量 및 最小分散不偏 推定量과 비교하여 그 장단점을 살펴보는데 본 논문의 목적이 있다. 그런데 최우추정량과 최소분산불편추정량은 구하기가 일반적으로 힘들 뿐 아니라 존재하지 않는 경우가 많으므로 그 분산을 구하는 것 또한 용이하지가 않다. 그리하여 본 논문에서는 지수분포의 예를 들어 시뮬레이션을 통하여 세 推定量사이의 效率性을 검토해 보았다. 그 결과 經驗的 推定量은 다른 추정량들보다 相대的으로 效率性은 열등하나 반면 분산의 상한이 주어지고 또한 구하기가 용이함으로써 실용적인 측면에서는 우월한 점이 많다는 것을 알 수 있다. 결론적으로 經驗的 推定量은 구하기가 수월할 뿐 아니라 불편성과 분산의 상한을 지니고 있으므로 일반적으로 얻기가 힘든 最尤推定量 및 最小分散不偏 推定量을 대신 할 수 있으며 또한 標本의 크기가 크면 매우 좋은 效率性을 갖게 된다.

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

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

Integrated assessment of trace pollutants associated with the Korean coastal environment: Exampled from the sediment TIE and triad approaches

Khim, J. S.,Koh, C. H. SPRINGER 2011 Toxicology and Environmental Health Sciences Vol.3 No.2

Reconstruction of surface water conditions in the central region of the Okhotsk Sea during the last 180kyrs

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>

Highly stable printed polymer field-effect transistors and inverters <i>via</i> polyselenophene conjugated polymers

Khim, Dongyoon,Lee, Woo-Hyung,Baeg, Kang-Jun,Kim, Dong-Yu,Kang, In-Nam,Noh, Yong-Young The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.25

<P>We report the use of two polyselenophene-based conjugated polymers, poly(3,3′′-didodecyl-2,2′:5,2′′-terselenophene) (<B>P3Se</B>) and poly(3,3′′,3′′′,3′′′′-tetradodecyl-2,5′:2′,2′′:5′′,2′′′-pentaselenophene) (<B>P5Se</B>), as an active layer of printed p-channel organic field-effect transistors (OFETs). Top-gate/bottom-contact (TG/BC) <B>P5Se</B> OFETs showed a high-saturation hole mobility of up to ∼0.1 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP> and a high on/off ratio of ∼10<SUP>5</SUP> with no hysteresis. In addition, polyselenophene-based OFETs exhibited a much better bias and ambient stability when compared with poly(3-hexylthiophene)-based OFETs. The excellent air stability of those polyselenophenes enables the realization of complementary metal-oxide semiconductor (CMOS) inverters <I>via</I> extended periods of ink-jetting under ambient conditions. CMOS inverters were demonstrated using p-[<B>P5Se</B>] and n-channel [poly{[<I>N</I>,<I>N</I>′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-<I>s</I>,6-diyl]-<I>alt</I>-5,5′-(2,2′-dithiophene)}] ([P(NDI2OD-T2)], Polyera ActivInk N2200/OFETs) by inkjet printing of conjugated polymers. Printed CMOS inverters exhibited a stable voltage transfer characteristic with negligible hysteresis, a DC voltage gain of ∼10, and a power consumption of ∼0.025 mW at <I>V</I><SUB>DD</SUB> = −60 V.</P> <P>Graphic Abstract</P><P>We report the use of two polyselenophene-based conjugated polymers, poly(3,3′′-didodecyl-2,2′:5,2′′-terselenophene) (<B>P3Se</B>) and poly(3,3′′,3′′′,3′′′′-tetradodecyl-2,5′:2′,2′′:5′′,2′′′-pentaselenophene) (<B>P5Se</B>), as an active layer of printed p-channel organic field-effect transistors (OFETs). <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm16546e'> </P>

Stable Oxygen and Carbon Isotope Profiles of the Bivalve Shells collected from Coastal Regions of Korea: Comparison of the Coastal Water Properties

Khim, Boo-Keun The Korean Society of Oceanography 1997 Journal of the Korean Society of Oceanography Vol.32 No.1

Two marine bivalve shells were collected from the eastern and western coastal regions of Korea, respectively. Stable oxygen and carbon isotope profiles are constructed using the incremental sampling along the axis of maximum growth to provide the continuous ${\delta}^{18}$O and ${\delta}^{13}$C records, which register the physical, biological and chemical properties of seawater where the organisms live. Cycles in the ${\delta}^{18}$O profiles are interpreted as annual along with the identification of annual growth bands; the maximum ${\delta}^{18}$O values correspond with the coldest temperature of seawater whereas the minimum ${\delta}^{18}$O values with the warmest temperature. The primary control on the amplitude of the ${\delta}^{18}$O profiles is seasonal variation of seawater temperature. The offset of the baseline between ${\delta}^{18}$O values of the two specimens is attributed to differences in both temperature and seawater ${\delta}^{18}$O values between two localities. The ${\delta}^{13}$C profiles show the similar seasonality of carbon cycling associated with phytoplankton productivity. The offset in the ${\delta}^{13}$C profiles between two specimens may be, as in the case of oxygen isotope profile, attributed to the different ${\delta}^{13}$C value of the seawater DIC (dissolved inorganic carbon) between the western coast and the eastern coast. Relationships between the shell isotopic composition and the coastal water properties of shell growth are readily interpreted from the ${\delta}^{18}$O-${\delta}^{13}$C pair diagram of the shell isotope data, similar to the use of salinity-${\delta}^{18}$O diagram for identifying water masses. The preliminary stable isotope results of this study suggest that mollusk shell isotope geochemistry may be useful to monitor the properties of water masses in the coastal and inner shelf setting around Korea and improve the interpretation of paleoceanography, provided the fossil mollusks are well preserved.