• Title, Summary, Keyword: Super stability

Search Result 130, Processing Time 0.042 seconds

Surface roughness and color stability of various composite resins (수종의 복합 레진의 표면 거칠기와 색 안정성)

  • Lee, Sung-Yi;Kim, Hyeon-Cheol;Hur, Bock;Park, Jeong-Kil
    • Restorative Dentistry and Endodontics
    • /
    • v.32 no.6
    • /
    • pp.542-549
    • /
    • 2007
  • The purpose of this study was to evaluate the difference in the surface roughness after polishing and to evaluate the difference in color stability after immersion in a dye solution among four types of composite resin materials. Four light-polymerized composite resins(Shade A2) with different sized filler content(a nanofilled, a hybrid, a microfilled, a flowble) were used. Average surface roughness (Ra) was measured with a surface roughness tester (Surftest Formtracer) before and after polishing with aluminum oxide abrasive discs(Super-Snap). Color of specimens before and after staining with 2% methylene blue solution were measured using spectrophotometer(CM-3700d) with SCI geometries. The results of Ra and ${\Delta}E$ were analyzed by one-way analysis of variance(ANOVA), a Scheffe multiple comparison test and Student t-test(p=0.05). After polishing, Ra values were decreased regardless of type of composite resins. In surface roughness after polishing and color stability after staining, nanofilled composite resin was not different with other composite resins except flowable resins.

Trend on Development of Low Molecular Weight Organosilicone Surfactants (Part II) (저분자 유기실리콘 계면활성제의 개발 동향 (제2보))

  • Rang, Moon Jeong
    • Journal of the Korean Applied Science and Technology
    • /
    • v.34 no.3
    • /
    • pp.461-477
    • /
    • 2017
  • Organosilicone-based surfactants, consisting of hydrophobic organosilicone groups coupled to hydrophilic polar groups, have been widely used in many industrial fields starting from polyurethane foam to construction materials, cosmetics, paints & inks, agrochemicals, etc., because of their low surface tension, lubricity, spreading, water repellency and thermal and chemical stability, resulted from the unique properties of organosilicone. Especially, organosiloxane surfactants, having low molecular weight siloxane as hydrophobe, exhibit low surface tension and excellent wettability and spreadability, leading to their applications as super wetter/super spreader, but have the disadvantage of vulnerability to hydrolysis. A variety of low molecular weight siloxane surfactant structures are required to provide the functional improvement and the defect resolution for reflecting the necessities in the various applications. This review includes the synthetic schemes of reactive tetrasiloxanes and disiloxanes as hydrophobic siloxane backbones, the main reaction schemes, such as hydrosilylation reaction, for coupling reactive tetrasiloxanes or disiloxanes to hydrophilic groups, and the main synthetic schemes of the tetra- and di-siloxane surfactants having polyether-, carbohydrate-, gemini-, bola-type surfactant structures.

Mixed Carbon/Polypyrrole Electrodes Doped with 2-Naphthalenesulfonic Acid for Supercapacitor (2-Naphthalenesulfonic Acid로 도핑된 혼합카본/폴리피롤을 이용한 Supercapacitor용 전극)

  • Jang, In-Young;Kang, An-Soo
    • Korean Chemical Engineering Research
    • /
    • v.43 no.3
    • /
    • pp.425-431
    • /
    • 2005
  • New type of supercapacitor using high surface area activated carbons mixed with high conductivity polypyrrole (Ppy) has been prepared in order to achieve low impedance and high energy density. Mixed carbons of BP-20 and MSP-20 were used as the active electrode material, and polypyrrole doped with 2-naphthalenesulfonic acid (2-NSA) and carbon black (Super P) as conducting agents were added to activated carbons in order to enhance good electric conductivity. Electrodes prepared with the activated electrode materials and the conducting agents were added to a solution of organic binder [P(VdF-co-HFP) / NMP]. The ratio of optimum electrode composition was 78 : 17 : 5 wt.% of (MSP20 : BP-20=1 : 1), (Super P : Ppy=10 : 7) and P(VdF-co-HFP) respectively. The performance of unit cell with addition of 7 wt% Ppy have shown specific capacitance of 28.02 F/g, DC-ESR of $1.34{\Omega}$, AC-ESR of $0.36{\Omega}$, specific energy of 19.87 Wh/kg and specific power of 9.77 kW/kg. With addition of Ppy, quick charge-discharge of unit cell was possible because of low ESR, low charge transfer resistance and quick reaction rate. And good stability up to 500 chargedischarge cycles were retained about 80% of their original capacity. It was concluded that the specific capacitance originated highly from compound phenomena of the pseudocapacitance by oxidation-reduction of polypyrrole and the nonfaradaic capacitance by adsorption-desorption of activated carbons.

Design and Operation Characteristics of a Two-Stage Compressor (이단 압축기의 동력학적 설계 및 운전 특성에 관한 연구)

  • Lee, Yong-Bok;Kim, Tae-Ho;Kim, Chang-Ho;Lee, Nam-Soo;Choi, Dong-Hoon
    • The KSFM Journal of Fluid Machinery
    • /
    • v.5 no.1
    • /
    • pp.55-61
    • /
    • 2002
  • The feasibility of an oil-free, motor-driven, two-stage centrifugal compressor supported by air bump bearings is investigated. This centrifugal compressor is driven by a 75 kW motor at an operating speed of 39,000 RPM, and a pressure ratio of the compressor is set up to 4. The analysis is performed by using bearing equilibrium position, heaving stillness, Campbell diagram, unbalance response, and stability. It is demonstrated in this paper that air bump bearings can be adopted well to an oil-free, motor-driven, centrifugal compressor. Specially, Cu-coated bump bearings have enough damping force to reduce a synchronous unbalance for rigid modes of the two-stage compressor. Futhermore, this concept may be applied to the flexible rotor system such as high speed turbomachinery with a super critical speed.

A STUDY ON THE COLOR STABILITY AND SHEAR BOND STRENGTH OF DENTURE REPAIR RESINS (의치 수리용 레진의 색안정성과 결합강도에 관한 연구)

  • Jin, Tai-Ho
    • The Journal of Korean Academy of Prosthodontics
    • /
    • v.33 no.1
    • /
    • pp.24-31
    • /
    • 1995
  • This study was performed to investigate the color stability and shear bond strength of denture repair resins. The denture base resins used in this study were Premium Super-20(Lang Dental Mfg. Co., Inc.,.U.S.A.) as heat curing resin, Triad VLC Denture Base(Dentsply/York Division, U.S.A.), Triad Reline Material(Dentsply/York Division, U.S.A.), Repair Acrylic(Lang Dental Mfg. Co., Inc.,. U.S.A.), Toughron Rebase (MikiChemical Product, Kyoto, Japan), and Tokuso Rebase(Tokuyama Soda Co., Ltd., Japan) as denture repair resin. After fabrication of specimens, they stored for 20 months, then color changes and shear bond strength were measured by colorimeter(Model TC-6FX, Tokyo Denshoku Co.) and Instron Universial Test Machine. The results were as follows : 1. There were changes of $L^{\ast},\;a^{\ast},\;b^{\ast}$ and $DE^{\ast}$ in Triad VLC Denture Base after 20 months. 2. There were changes of $a^{\ast}$ in Toughron Rebase and Tokuso Rebase, and $b^{\ast}$ in Tokuso Rebase after 20 months. 3. The shear bond strength of Repair Acrylic and Toughron Rebase were higher than that of Tokuso Rebase and Triad Reline Material.

  • PDF

Study on the Mechanical Properties of Polyketone Fiber according to Dyeing and Finishing Process (폴리케톤 섬유의 염색 및 후가공 처리에 따른 기계적 물성에 관한 연구)

  • Kim, Sang Yong;Kim, Kyung Min;Lee, Won;Lee, Deuk Jin;Whang, Sun Dong;Yang, Sung Yong
    • Textile Coloration and Finishing
    • /
    • v.29 no.2
    • /
    • pp.97-103
    • /
    • 2017
  • Polyketone fiber, a newly developed high strength fiber, has a tenacity and modulus similar to the p-aramid fiber, and can be used for reinforcing mechanical rubber goods(MRG), such as tires, hoses, and technical textiles. It will be expected for replacement of super fiber such as aramids and increasing the technical textile market share. This paper surveys the mechanical properties of polyketone fiber for technical textiles. For this purpose, dyed polyketone fabric is prepared, mechanical properties of coated and uncoated polyketone fabrics such as tensile strength, elongation and tear strength were examined before and after weather resistance test(temperature $63{\pm}3^{\circ}C$, humidity 60%, amount of power $0.35w/m^2$). The differences of mechanical properties between uncoated and coated fabrics for high functional technical textiles and composite materials are estimated through this study. The UV-stability of polyketone fabric showed obvious improvement after coating. After 168h(7day) of UV exposure, the coated fabric showed less deterioration in mechanical properties with the retained tensile strength and elongation at break greater than 22 and 17% of the uncoated polyketone fabrics values, respectively.

Study on the Mechanical Properties of Polyketone Fiber according to Coating Process for Technical Textile (산업용 폴리케톤 섬유의 코팅 가공에 따른 기계적 물성에 관한 연구)

  • Kim, Sang Yong;Jeon, Jae Woo;Kwak, Dong Sub;Lee, Won;Lee, Deuk Jin;Whang, Sun Dong;Do, Sung Jun
    • Textile Coloration and Finishing
    • /
    • v.27 no.4
    • /
    • pp.334-339
    • /
    • 2015
  • Polyketone fiber, a newly developed high strength fiber, has a tenacity and modulus similar to the paramid fiber, and can be used for reinforcing mechanical rubber goods(MRG), such as tires, hoses, and technical textiles. In addition, aliphatic polyketone, which has excellent strength, modulus, chemical stability and reasonable price, is being developed only in South Korea. It will be expected for replacement of super fiber such as aramids and increasing the technical textile market share. This paper surveys the mechanical properties of polyketone fiber yarn for technical textiles. For this purpose, two kinds of yarns are prepared, mechanical properties of coated and uncoated polyketone yarns such as tensile strength, elongation and modulus were examined before and after weather resistance test(temperature $60^{\circ}C$, humidity 60%, amount of power $0.67w/m^2$). The differences of mechanical properties between uncoated and coated yarns for high functional technical textiles and composite materials are estimated through this study.

Current Situation and Overview of Biodiesel over the Global View (글로벌 측면에서 본 바이오디젤의 현황과 전망)

  • Lee, Moon-Yong;Lee, Jin-Hui;Kwak, Jung-Min;Kim, Jae-Kon
    • Journal of the Korean Applied Science and Technology
    • /
    • v.30 no.3
    • /
    • pp.528-539
    • /
    • 2013
  • Biodiesel is one of the most important renewable energy, since it is one of the most important alternative and eco-friendly energy source compared to fossil energy, especially for diesel engineequipped vehicles. It is now coming up for preparation of biodiesel as the alternative that applies the hetrogeneous catalyst, super critical state and various methods used in order to reduce the stages of the processes be converted and separation stages started from oil and fat which are originated from animals and wastes, and those new methods bring eco-friendly as well, though some of those are stand on research step so far. It is necessary that nation provides the tax exemption program for the supplier and strengthen the research system for the farming crops relate to fat and oil. It can improve the development of biodiesel which sustains stability against oxidation and keeps good mobility over the low temperatures in the winter season by new additives and develops new processes to show good harmony with diesel engine.

Deformation and failure mechanism exploration of surrounding rock in huge underground cavern

  • Tian, Zhenhua;Liu, Jian;Wang, Xiaogang;Liu, Lipeng;Lv, Xiaobo;Zhang, Xiaotong
    • Structural Engineering and Mechanics
    • /
    • v.72 no.2
    • /
    • pp.275-291
    • /
    • 2019
  • In a super-large underground with "large span and high side wall", it is buried in mountains with uneven lithology, complicated geostress field and developed geological structure. These surrounding rocks are more susceptible to stability issues during the construction period. This paper takes the left bank of Baihetan hydropower station (span is 34m) as a case study example, wherein the deformation mechanism of surrounding rock appears prominent. Through analysis of geological, geophysical, construction and monitoring data, the deformation characteristics and factors are concluded. The failure mechanism, spatial distribution characteristics, and evolution mechanism are also discussed, where rock mechanics theory, $FLAC^{3D}$ numerical simulation, rock creep theory, and the theory of center point are combined. In general, huge underground cavern stability issues has arisen with respect to huge-scale and adverse geological conditions since settling these issues will have milestone significance based on the evolutionary pattern of the surrounding rock and the correlation analyses, the rational structure of the factors, and the method of nonlinear regression modeling with regard to the construction and development of hydropower engineering projects among the worldwide.

Development of lapping wheel for Electrolytic Dressing and evaluation of performance (전해 드레싱용 래핑지석의 개발 및 성능평가)

  • 송지복;이은상;최재영
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • /
    • pp.858-861
    • /
    • 2000
  • Application of ceramics, carbide, ferrite has grown considerably due to significant improvement in their mechanical properties such as light weight chemical stability super wear resistance and electronical. Despite these character, the use of hi-tech material has not increased because of poor machinability. The method of using of metal bond wheel was proposed. But it is difficult that metal bond wheel can be dressed. Recently, the technology of in-process electrolytic dressing is developed to solve this problem. This method need wheel for electrolytic dressing, power supply and electrolyte. But development of wheel for electrolytic dressing is the most need. The aim of this study is development of wheel for electrolytic and appraisement of CIB-diamond lapping wheel

  • PDF