• Title, Summary, Keyword: Super stability

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Mock-up Test of Improving Super Retarding Concrete to Control of Hydration Heat Crack of Foundation Mat Mass Concrete (기초매트 매스콘크리트의 수화열 균열제어로서 초지연콘크리트 활용에 관한 Mock-up 실험)

  • Lee, Jae-Sam;Bae, Yeoun-Ki;Noh, Sang-Kyun;Kim, Suk-Il;Chung, Sung-Jin;Han, Cheon-Goo
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.777-780
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    • 2008
  • According to the recent tendency that the buildings in the downtown are gradually Manhattanized, the very thick massive concrete is selected as the foundation of architectures. By the way, because this mass concrete cannot be simultaneously pour in a great quantity due to the circumstance at the field, not only the questions on the unification between the concretes pour on the upper layer and the lower layer are presented but also the cracks by the internal force from the difference of hydration exothermic period are occurred, which are pointed out as the problems. Thus, this study performed Mock-up test to apply the hydration heat controlling method of massive concrete for horizontal partition pouring construction to the building sites for the purpose of securing the stability on the cracks by the internal force from the difference of hydration exothermic period on the upper layer and the lower layer of massive concrete and checked the efficiency. As the results of test, in case of setting time difference method by super retarder with 2 layers and 4 layers, the effect that temperature gaps between upper part and lower part were lowered and the possibility of crack occurrence was decreased as the peak time of the heat of hydration became delayed to the latter term could be confirmed.

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THE INFLUENCE OF THE DIE HARDENER ON GYPSUM DIE (석고 다이에 대한 다이 강화제의 영향)

  • Kim, Young-Rim;Park, Ju-Mi;Song, Kwang-Yeob
    • The Journal of Korean Academy of Prosthodontics
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    • v.45 no.4
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    • pp.546-554
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    • 2007
  • Statement of problem: Die materials require abrasion resistance, dimensional stability with time, and high surface wettability for adequate material properties. Wear of gypsum materials is a significant problem in the fabrication of accurately fitting cast prosthetic devices. So It has been recommended that the use of die hardener before carving or burnishing of the wax pattern. Purpose: The purpose of this study was to compare the abrasion resistance and surface microhardness(Knoop) with 3 commonly used gypsum die materials(MG Crystal Rock, Super plumstone, GC $FUJIROCK^{(R)}$ EP) with and without the application of 2 die hardeners. Material and methods: Three die materials were evaluated for abrasion resistance and surface microhardness after application of 2 die hardeners(Die hardener and Stone die & plaster hardener). Thirty specimens of each gypsum material were fabricated using an impression of resin die(Pattern resin; GC Corporation, Japan) with 1-mm high ridges, sloped 90 degrees. Gypsum materials were mixed according to manufacturer's recommendations and allowed to set 24 hours before coating. Specimens were arbitrary assigned to 1 of 3 treatment subgroups (n=10/subgroup): no treatment(control), coated with Die hardener, and coated with Stone die & plaster hardener. Abrasion resistance(measured by weight loss) was evaluated using device in 50g mass perpendicular to the ridges. Knoop hardness was determined by loading each specimen face 5 times for 15 seconds with a force of 50g. A scanning electron microscope was used to evaluate the surface of specimens in each treatment subgroup. Conclusions: The obtained results were as follows: 1. 3 types of die stone evaluated in this study did not show significant differences in surface hardness and abrasive resistance(P<.05). 2. In the abrasive resistance test, there were no significant differences between GC $FUJIROCK^{(R)}$ EP and MG Crystal Rock with or without 2 die hardener(P<.05). 3. Super plumstone treated with Stone die & plaster hardener showed increased wear loss(P<.05) 4. Die hardener coatings used in this study decreased the surface hardness of the gypsum material(P<.05).

Physical Properties of Hybrid Boards Composed of Green Tea, Charcoals and Wood Fiber (녹차-숯-목재섬유 복합보드의 물리적 특성)

  • Park, Han-Min;Heo, Hwang-Sun;Sung, Eun-Jong;Nam, Kyeong-Han;Lim, Jae-Seop
    • Journal of the Korean Wood Science and Technology
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    • v.40 no.6
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    • pp.406-417
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    • 2012
  • In this study, eco-friendly hybrid composite boards were manufactured from green tea, three kinds of charcoals and wood fiber for developing interior materials to reinforce the functionalities such as the deodorization and the absorbability on the green tea-wood fiber hybrid boards in the previous researches. The effects of kind of raw materials and the component ratio of raw materials on dimensional stability, deodorization and emission of formaldehyde were investigated. Thickness swelling of the hybrid composite boards increased with increasing of component ratio of green tea and charcoals, but the values were markedly lower than that of Korean standard (KS) for commercial medium density fiber board (MDF), except for hybrid composite boards composed of greed tea, activated charcoal and wood fiber. Reduction rate of ammonia gas for the hybrid composite boards composed of green tea, activated charcoal and wood fiber showed a high value of 96% after 30 minute from the beginning of the test, and the other hybrid boards also showed a high value of about 95% after one hour. Emission amount of formaldehyde was similar to that of $E_0$ grade in case of using $E_1$ grade urea resin, and was similar to that of super $E_0$ grade in case of using $E_0$ grade urea resin.

'Lip Smile'- A New Calla Cultivar with Light Yellow and Reddish Purple Colors and a Large Spathe for Cut Flowers (연노랑 바탕 적자색으로 화형이 큰 절화용 유색칼라 신품종 'Lip Smile' 육성)

  • Ko, Jae Young;Kim, Young Jin;Choi, Kang Jun;Byon, Sun Bae;Park, Ji Eun;Bang, Soon Bae
    • FLOWER RESEARCH JOURNAL
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    • v.26 no.3
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    • pp.152-156
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    • 2018
  • A colored calla (Zantedeschia spp.) cultivar 'Lip Smile' was bred from the cross between Zantedeschia spp. 'Super Gem' with a rose-pink to lavender spathe and 'Black Magic' with a light yellow spathe at the Gangwon Provincial Agricultural Research and Extension Services in Korea. The cross was performed in 2003. In 2006, 'GZ0616' was selected as a good color and flower type by screening the flowering characteristics. In 2007, it was selected for the second stage after characterization of growth rate, plant height, and initial stage. From 2013 to 2015, uniformity and stability were confirmed through characterization and cultivation tests, and it was finally selected as 'GanggyoC4-6'. In February 2017, this cultivar was registered as 'Lip Smile'. The main outside spathe color is light yellow and reddish pink (Y2C+RP79C). The spathe height is 8.5 cm and the width is 6.2 cm. The flowering time is 64.3 days, the plant height is 66.0 cm, and the tuber fresh weight is 80.0 g. Consumer preference for this cultivar is higher than that for the reference cultivar 'Captain Rosette'. 'Lip Smile' is mainly available for cut flowers.

U.S. and China's Military Competition in east-Asia and Korea's Security (동아시아에서의 미국과 중국의 군사경쟁과 한국안보)

  • Park, Eung-soo;Ko, Kwang-soop
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.214-218
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    • 2012
  • China has definitely been arising as the world's most powerful nation. By looking at general national power it seems that China's national prestige in 2011 is already way beyond Asia and even it closely catches up with the United States which is the most powerful nation over the world. The United states-centered world political order has begun to struggle by China's growth. Moreover, there has been an earnest competition arisen for the east-Asia sea supremacy between previous U.S. hegemony and arising China's power. East-Asia's ocean is the stage for this strife and it grows more serious. At this point, South Korea, one of the east-Asia country seeking the nation's stability and prosperity through its ocean, has come under the influence of this strife among the super powers of the world. The Author will closely examine the backgrounds and future opportunities of military competition between U.S. and China to analyze the influence of the power competition towards the security status of east-Asia especially South Korea.

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High alcohol-soluble MoOx gel for interfacial layer in organic solar cells

  • Xiong, Jian;He, Zhen;Zhan, Shiping;Yang, Bingchu;Zhang, Xiaowen;Cai, Ping;Xu, Cong;Xue, Xiaogang;Zhang, Jian
    • Current Applied Physics
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    • v.17 no.8
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    • pp.1021-1028
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    • 2017
  • Water-free solvent soluble, low-temperature processed metal oxides are important for preparing efficient and stable electronic devices, as well as the convenience in simplifying the device production process. Here we reported a facile approach with the features of low-temperature and solution-based process for the formation of a $MoO_x$ ($s-MoO_x$) film as interface layer in polymer solar cells (PSCs). The absorbability, elementary composition, electronic property and surface microstructure of the $s-MoO_x$ are investigated in detail by ultraviolet-visible spectrophotometer (UV-vis), X-ray photoelectron spectrometry (XPS), ultraviolet photo-electron spectrometer (UPS) and atomic force microscopy (AFM). These investigations confirmed that such $MoO_x$ xerogel has high solubility in the organic alcohol solvents, such as ethanol and methanol. Meanwhile, this $s-MoO_x$ can be applied as the interfacial layer in organic solar cells via a low-temperature treatment (about $100^{\circ}C$) due to its proper physical properties, and a power conversion efficiency (PCE) over 3% was achieved. In addition, the devices with $s-MoO_x$ shows excellent air-stability, and the PCE efficiency can maintain about 84% of its initial value after 100 h exposure in air, which is dramatically enhanced comparing with the common devices with PEDOT:PSS layer.

Eicosapentaenoic Acid (EPA) Biosynthetic Gene Cluster of Shewanella oneidensis MR-1: Cloning, Heterologous Expression, and Effects of Temperature and Glucose on the Production of EPA in Escherichia coli

  • Lee, Su-Jin;Jeong, Young-Su;Kim, Dong-Uk;Seo, Jeong-Woo;Hur, Byung-Ki
    • Biotechnology and Bioprocess Engineering:BBE
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    • v.11 no.6
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    • pp.510-515
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    • 2006
  • The putative EPA synthesis gene cluster was mined from the entire genome sequence of Shewanella oneidensis MR-1. The gene cluster encodes a PKS-like pathway that consists of six open reading frames (ORFs): ORFSO1602 (multi-domain beta-ketoacyl synthase, KS-MAT-4ACPs-KR), ORFSO1600 (acyl transferase, AT), ORFSO1599 (multi-domain beta-ketoacyl synthase, KS-CLF-DH-DH), ORFSO1597 (enoyl reductase, ER), ORFSO1604 (phosphopentetheine transferase, PPT), and ORFSO1603 (transcriptional regulator). In order to prove involvement of the PKS-like machinery in EPA synthesis, a 20.195-kb DNA fragment containing the genes was amplified from S. oneidensis MR-1 by the long-PCR method. Its identity was confirmed by the methods of restriction enzyme site mapping and nested PCR of internal genes orfSO1597 and orfSO1604. The DNA fragment was cloned into Escherichia coli using cosmid vector SuperCos1 to form pCosEPA. Synthesis of EPA was observed in four E. coli clones harboring pCosEPA, of which the maximum yield was 0.689% of the total fatty acids in a clone designated 9704-23. The production yield of EPA in the E. coli clone was affected by cultivation temperature, showing maximum yield at $20^{\circ}C$ and no production at $30^{\circ}C$ or higher. In addition, production yield was inversely proportional to glucose concentration of the cultivation medium. From the above results, it was concluded that the PKS-like modules catalyze the synthesis of EPA. The synthetic process appears to be subject to regulatory mechanisms triggered by various environmental factors. This most likely occurs via the control of gene expression, protein stability, or enzyme activity.

Application of Soil-Cement Piles to the Ground Improvement of Harbor Structures (소일-시멘트 파일을 이용한 항만구조물의 말뚝식 지반개량 적용성)

  • Lee, Seong-Hun;Kwon, Oh-Yeob;Shin, Jong-Ho
    • Journal of the Korean Geotechnical Society
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    • v.29 no.11
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    • pp.29-47
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    • 2013
  • This study undertook research on the sections of 90 harbor structures which applied a pile-type soil improvement using the soil-cement pile and then, determined the minimum replacement rate for each section, showing sufficient stability in all relevant studies including numerical analysis. The reliability of the numerical analysis was verified by a centrifuge model test. As a result of the study, it was revealed that when the foundation soil is too soft ($s_u$ = under 15 kPa), it is unsuitable to apply a pile-type ground improvement to a soil improvement regardless of types of super structures. And a pile-type soil improvement was found to be suitable for a harbor structure with the relative stiffness ratio (n) of less than 50~75 at a maximum and the 2~3 MPa strength of the soil-cement pile. Furthermore the governing factor for the minimum replacement rate for the pile-type soil improvement was turned out to be the allowable horizontal displacement. Therefore, the primary review to see the applicability of the pile-type soil improvement requires the evaluation of horizontal displacements.

Wear Resistance of c-BN Surface Modified 316L Austenitic Stainless Steel by R.F. Sputtering (R.F. sputtering 방법에 의해 c-BN 표면처리된 316L 오스테나이트계 스테인리스 강의 내마모특성 향상)

  • Lee, Kwang-Min;Jeong, Se-Hoon;Park, Sung-Tae
    • Korean Journal of Materials Research
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    • v.20 no.4
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    • pp.194-198
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    • 2010
  • Cubic boron nitride (c-BN) is a promising material for use in many potential applications because of its outstanding physical properties such as high thermal stability, high abrasive wear resistance, and super hardness. Even though 316L austenitic stainless steel (STS) has poor wear resistance causing it to be toxic in the body due to wear and material chips, 316L STS has been used for implant biomaterials in orthopedics due to its good corrosion resistance and mechanical properties. Therefore, in the present study, c-BN films with a $B_4C$ layer were applied to a 316L STS specimen in order to improve its wear resistance. The deposition of the c-BN films was performed using an r.f. (13.56 MHz) magnetron sputtering system with a $B_4C$ target. The coating layers were characterized using XPS and SEM, and the mechanical properties were investigated using a nanoindenter. The friction coefficient of the c-BN coated 316L STS steel was obtained using a pin-on-disk according to the ASTM G163-99. The thickness of the obtained c-BN and $B_4C$ were about 220 nm and 630 nm, respectively. The high resolution XPS spectra analysis of B1s and N1s revealed that the c-BN film was mainly composed of $sp^3$ BN bonds. The hardness and elastic modulus of the c-BN measured by the nanoindenter were 46.8 GPa and 345.7 GPa, respectively. The friction coefficient of the c-BN coated 316L STS was decreased from 3.5 to 1.6. The wear property of the c-BN coated 316L STS was enhanced by a factor of two.

A Study on Characteristic of Superconductivity and Microstructure of $Y_1Ba_2Cu_3O_{7-y}$-Ag ($Y_1Ba_2Cu_3O_{7-y}$-Ag의 초전도성과 미세구조의 특성 연구)

  • Kim, Chae-Ok;Park, Jeong-Su;Yu, Deok-Su
    • Korean Journal of Materials Research
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    • v.5 no.7
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    • pp.786-793
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    • 1995
  • Ag-doped $Y_1$Ba$_2$Cu$_3$O$_{7-y}$ samples have been prepared by solid state reaction. High-Tc super conductivity, microstructure and mechanical property of the Ag-doped $Y_1$Ba$_2$Cu$_3$O$_{7-y}$ samples have been studied. As the Ag content increased, the grain size of $Y_1$Ba$_2$Cu$_3$O$_{7-y}$, increased and connectivity between the grains was improved, and the sample becomed denser and harder than the undoped. From the result, it is concluded that Ag addition reduced weak link and weak coupling between grains and led to the strong coupling. Furthermore, the anisotropy of crytstal structure was decreased and thermal stability, mechanical property of $Y_1$Ba$_2$Cu$_3$O$_{7-y}$-Ag were improved.mproved.

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