• Title, Summary, Keyword: Super stability

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Wear characteristics of boron nitride thin film for durability improvement of ultra- precision component (초정밀 부품의 내구성 향상을 위한 질화붕소 박막의 마멸 특성에 관한 연구)

  • Ku, Kyoung-Jin;Hwang, Byoung-Har;Lin, Li-Yu;Kim, Dae-Eun;Baik, Hong-Koo
    • Transactions of the Society of Information Storage Systems
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    • v.3 no.3
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    • pp.129-134
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    • 2007
  • Boron nitride (BN) is a highly attractive material for wear resistant applications of mechanical components. BN is super hard and it is the second hardest of all known materials. It also has a high thermal stability, high abrasive wear resistance, and in contrast to diamond, BN does not react with ferrous materials. The motivation of this work is to investigate the tribological properties of BN for potential applications in ultra-precision components for data storage, printing, and other precision devices. In this work, the wear characteristics of BN thin films deposited on DLC or Ti buffer layer with silicon substrate using RF-magnetron sputtering technique were analyzed. Wear tests were conducted by using a pin-on-disk type tester and the wear tracks were measured with a surface profiler. Experimental results showed that wear characteristics were dependent on the sputtering conditions and buffer layer. Particularly, BN coated on DLC layer showed better wear resistant behavior. The range of the wear rates for the BN films tested in this work was about 20 to $100{\mu}m^3$/cycle.

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Earthquake Response Analysis of an Offshore Wind Turbine Considering Effects of Geometric Nonlinearity of a Structure and Drag Force of Sea Water (기하 비선형과 항력 효과를 고려한 해상풍력발전기의 지진 응답해석)

  • Lee, Jin Ho;Bae, Kyung Tae;Jin, Byeong Moo;Kim, Jae Kwan
    • Journal of the Earthquake Engineering Society of Korea
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    • v.17 no.6
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    • pp.257-269
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    • 2013
  • In this study, the capability of an existing analysis method for the fluid-structure-soil interaction of an offshore wind turbine is expanded to account for the geometric nonlinearity and sea water drag force. The geometric stiffness is derived to take care of the large displacement due to the deformation of the tower structure and the rotation of the footing foundation utilizing linearized stability analysis theory. Linearizing the term in Morison's equation concerning the drag force, its effects are considered. The developed analysis method is applied to the earthquake response analysis of a 5 MW offshore wind turbine. Parameters which can influence dynamic behaviors of the system are identified and their significance are examined.

A Study on Hybrid Control Unit Using a Smart Control (스마트 제어를 이용한 하이브리드 형 제어장치 연구)

  • Kim, Hee-Chul
    • The Journal of the Korea institute of electronic communication sciences
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    • v.11 no.11
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    • pp.1093-1100
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    • 2016
  • This study is to demonstrate the superiority and stability of the solar - wind power hybrid power generation system for street lamps using super capacitor EDLC(:Electric Double Layer Capacitor). It is aiming to apply the lighting device using LED light source as the load of solar-wind power hybrid power generation system for independent power source and to develop the street light system device with high output power generation system. Unlike conventional controllers, EDLC, which is used as an auxiliary device for storing the developed power in the battery, can guarantee the high output and long life of the battery.

Development of an advanced atmospheric pressure plasma source with high spatial uniformity and selectiveness for surface treatment

  • Im, Yu-Bong;Choe, Won-Ho;Lee, Seung-Hun;Han, U-Yong;Lee, Jong-Hyeon;Lee, Sang-Gyun;Ha, Jeong-Min;Kim, Jong-Hun
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.176-177
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    • 2016
  • In the last few decades, attention toward atmospheric pressure plasma (APP) has been greatly increased due to the numerous advantages of those applications, such as non-necessity of high vacuum facility, easy setup and operation, and low temperature operation. The practical applications of APP can be found in a wide spectrum of fields from the functionalization of material surfaces to sterilization of medical devices. In the secondary battery industry, separator film has been typically treated by APP to enhance adhesion strength between adjacent films. In this process, the plasma is required to have high stability and uniformity for better performance of the battery. Dielectric barrier discharge (DBD) was usually adopted to limit overcurrent in the plasma, and we developed the pre-discharge technology to overcome the drawbacks of streamer discharge in the conventional DBD source which makes it possible to produce a super-stable plasma at atmospheric pressure. Simulations for the fluid flow and electric field were parametrically performed to find the optimized design for the linear jet plasma source. The developed plasma source (Plasmapp LJPS-200) exhibits spatial non-uniformity of less than 3%, and the adhesion strength between the separator and electrode films was observed to increase 17% by the plasma treatment.

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'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.

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.

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).

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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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.