• Title/Summary/Keyword: Dominant Properties

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Microstructure and Mechanical Properties of High Mn TWIP Steels (고 Mn계 TWIP 강의 미세조직과 기계적 성질)

  • Jung, J.K.;Lee, O.Y.;Park, Y.K.;Kim, D.E.;Jin, K.G.;Kim, S.K.;Song, K.H.
    • Korean Journal of Metals and Materials
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    • v.46 no.10
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    • pp.627-633
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    • 2008
  • The austenitic Fe-Mn alloys have received considerable attention as a possible candidate for the automotive structural materials due to their high strength and high formability with high elongation. This research investigates the effect of alloying elements on the phase transformation, deformation behavior and mechanical properties in high Mn steels for the development of a high strength high ductility steel. The mechanical stability of austenitic phases is very important for high ductility and it depends largely on the composition of carbon, manganese and aluminum. The dominant deformation mode shifts from TRIP to TWIP mode as the amount of C, Mn and Al is increased. Especially, even a small amount of Al addition facilitates significantly TWIP deformation due to the increase of stacking fault energy in Fe-Mn alloys, this leads to increase the ductility and also decrease the crack sensitivity.

Thermoelectric Properties of AlN-doped SiC Ceramics (AlN 첨가 SiC 세라믹스의 열전변환특성)

  • Pai, Chul-Hoon
    • Korean Journal of Metals and Materials
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    • v.50 no.11
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    • pp.839-845
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    • 2012
  • The effect of an AlN additive on the thermoelectric properties of SiC ceramics was studied. Porous SiC ceramics with 48-54% relative density were fabricated by sintering the pressed ${\alpha}-SiC$ powder compacts with AlN at $2100-2200^{\circ}C$ for 3 h in an Ar atmosphere. In the undoped specimens, the Seebeck coefficients were positive (p-type semiconducting) possibly due to a dominant effect of the acceptor impurities (Al, Fe) contained in the starting powder. With AlN addition, the reverse phase transformation of 6H-SiC to 4H-SiC was observed during the sintering process. The electrical conductivity of the AlN doped specimen was larger than that of the undoped specimen under the same conditions, which might be due to a reverse phase trans-formation. The Seebeck coefficient of the AlN doped specimen was also larger than that of the undoped specimen. The density of specimen and the amount of addition had significant effects on the thermoelectric properties.

Qantum Transition properties of Si in Electron Deformation Potential Phonon Interacting Qusi Two Dimensional System (준 2차원 시스템에서 전자 변위 포텐셜 상호 작용에 의한 Si의 양자 전이 특성)

  • Joo, Seok-Min;Cho, Hyun-Chul;Lee, Su-Ho
    • Journal of IKEEE
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    • v.23 no.2
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    • pp.502-507
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    • 2019
  • We investigated theoretically the quantum optical transition properties of qusi 2-Dinensinal Landau splitting system, in Si. We apply the Quantum Transport theory (QTR) to the system in the confinement of electrons by square well confinement potential. We use the projected Liouville equation method with Equilibrium Average Projection Scheme (EAPS). In order to analyze the quantum transition, we compare the temperature and the magnetic field dependencies of the QTLW and the QTLS on two transition processes, namely, the phonon emission transition process and the phonon absorption transition process. Through the analysis of this work, we found the increasing properties of QTLW and QTLS of Si with the temperature and the magnetic fields. We also found the dominant scattering processes are the phonon emission transition process.

Effect of Seawater Temperature on the Cyclic Potentiodynamic Polarization Characteristics and Microscopic Analysis on Damage Behavior of Super Austenitic Stainless Steel (슈퍼오스테나이트 스테인리스강의 순환동전위 분극특성에 미치는 해수온도의 영향과 손상 거동에 관한 미시적 분석)

  • Hwang, Hyun-Kyu;Kim, Seong-Jong
    • Corrosion Science and Technology
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    • v.20 no.6
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    • pp.412-425
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    • 2021
  • Because austenitic stainless steel causes localized corrosion such as pitting and crevice corrosion in environments containing chlorine, corrosion resistance is improved by surface treatment or changes of the alloy element content. Accordingly, research using cyclic potentiodynamic polarization experiment to evaluate the properties of the passivation film of super austenitic stainless steel that improved corrosion resistance is being actively conducted. In this investigation, the electrochemical properties of austenitic stainless steel and super austenitic stainless steel were compared and analyzed through cyclic potentiodynamic polarization experiment with varying temperatures. Repassivation properties were not observed in austenitic stainless steels at all temperature conditions, but super austenitic stainless steels exhibited repassivation behaviors at all temperatures. This is expressed as α values using a relational formula comparing the localized corrosion rate and general corrosion rate. As the α values of UNS S31603 decreased with temperature, the tendency of general corrosion was expected to be higher, and the α value of UNS N08367 increased with increasing temperatures, so it is considered that the tendency of localized corrosion was dominant.

Analysis of the integral fuel tank considering hygrothermal enviornmental factors (열습도 환경요소를 고려한 일체형 복합재 연료탱크의 해석)

  • Moon, Jin-Bum;Kim, Soo-Hyun;Kim, Chun-Gon
    • Composites Research
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    • v.20 no.5
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    • pp.64-69
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    • 2007
  • Matrix dominant properties of composites are largely degraded under harmful environments such as temperature and humidity. Therefore we should consider the harmful environmental factors in the design of an UAV integral fuel tank subjected to high temperature and high humidity. The harmful environment experiment was performed for carbon/epoxy composites made of a unidirectional prepreg USN175B, and a plain woven fabric prepreg WSN3. The immersion experiment was performed under $90^{\circ}C$. The specimens were tested when the weight gam of specimen was saturated. The specimens were tested under $74^{\circ}C$ to obtain tensile and inplane shear properties. The results showed that the matrix dominant properties were extremely degraded by hygrothermal environment. To consider the variability of load, the anti-optimization method was applied. By using this method, the worst load case was found by comparing the load convex model and stability boundary. The stability boundary was obtained by analysis of the integral wing fuel tank of UAV using degraded properties. To do this, it was known that the worst load case of the integral wing fuel tank was the hovering mode load case.

Electronic, Optical and Electrical Properties of Nickel Oxide Thin Films Grown by RF Magnetron Sputtering

  • Park, Chanae;Kim, Juhwan;Lee, Kangil;Oh, Suhk Kun;Kang, Hee Jae;Park, Nam Seok
    • Applied Science and Convergence Technology
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    • v.24 no.3
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    • pp.72-76
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    • 2015
  • Nickel oxide (NiO) thin films were grown on soda-lime glass substrates by RF magnetron sputtering method at room temperature (RT), and they were post-annealed at the temperatures of $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$ and $400^{\circ}C$ for 30 minutes in vacuum. The electronic structure, optical and electrical properties of NiO thin films were investigated using X-ray photoelectron spectroscopy (XPS), reflection electron energy spectroscopy (REELS), UV-spectrometer and Hall Effect measurements, respectively. XPS results showed that the NiO thin films grown at RT and post annealed at temperatures below $300^{\circ}C$ had the NiO phase, but, at $400^{\circ}C$, the nickel metal phase became dominant. The band gaps of NiO thin films post annealed at temperatures below $300^{\circ}C$ were about 3.7 eV, but that at $400^{\circ}C$ should not be measured clearly because of the dominance of Ni metal phase. The NiO thin films post-annealed at temperatures below $300^{\circ}C$ showed p-type conductivity with low electrical resistivity and high optical transmittance of 80% in the visible light region, but that post-annealed at $400^{\circ}C$ showed n-type semiconductor properties, and the average transmittance in the visible light region was less than 42%. Our results demonstrate that the post-annealing plays a crucial role in enhancing the electrical and optical properties of NiO thin films.

Effects of salt water environment on the mechanical behavior of composites (복합재료의 기계적 거동에 염수환경이 미치는 영향에 관한 연구)

  • Moon, Jin-Bum;Kim, Soo-Hyun;Kim, Chun-Gon
    • Composites Research
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    • v.23 no.1
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    • pp.44-50
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    • 2010
  • In this paper, two different experiments, namely, salt water spray and salt water immersion, were performed to reproduce the contact of composites with the seawater for three kinds of woven fabric composite material systems which would be used for the WIG(wing in ground effect)craft. After aging 140 days in the salt water environment, material properties of carbon/epoxy and glass/epoxy composite such as tensile, compressive and shear stiffness and strength, and inter-laminar shear strength (ILSS) were measured. By comparing baseline material properties with degraded ones, the effects of the salt water environment on the composite mechanical properties were evaluated. From the experiments, it was confirmed that the difference in aging conditions had very small influence on composite properties. And it was found that tensile strength of carbon/epoxy composites showed little degradation, but much more degradation was observed in glass/epoxy composites. And large degradations on matrix dominant properties were observed. The salt water could damage the fiber-matrix interface, matrix properties and the glass fiber.

Petrologic and Geomorphologic Characteristics of Micrographic Granite in the Ijin-ri Area, Ulsan (울산 이진리 미문상화강암의 암석학적 및 지형학적 특성 연구)

  • Kim, Sun-Woong;Kim, Haang-Mook;Hwang, Byoung-Hoon;Yang, Kyoung-Hee;Kim, Jin-Seop
    • The Journal of the Petrological Society of Korea
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    • v.18 no.3
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    • pp.211-221
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    • 2009
  • This study illustrates the relationship between the petrographic characteristics of micrographic granite and the topographic features around Ijin-ri. Light-brown to light- gray granite is composed of intergrown fine-grained quartz + orthoclase, displaying micrographic textures. Miarolitic cavities are abundant. Many micro-landforms including tor, tafoni, and gnamma occurred in the micrographic granite of the study area. Tafoni is dominant in the north and gnamma is dominant in south. From our study of the occurrence and textural properties, two alteration zones were clearly identified; one is an external zone (A) characterized by abundant of small sized miarolitic cavities and the other is an internal zone (B) having them less than zone A. The former is dominant in north, and the latter is dominant in south. Particular geomorphologic features such as fluting cores and raised rims are present in the Ijin-ri area. This suggests that development of miarolitic cavities played an important role in the formation of the various geomorphologic features. Consequently, the petrogenesis of the micrographic granite is related to geomorphologic features in the external zone typified by abundant tafoni such as the tiger rock, and the formation of a platform as micro-landforms is influenced by thetextural differences of host rock in the internal zone.

Characteristics of Phosphorus Accumulation in Organic Farming Fields (유기농업실천농가 포장내 인산의 분포특성)

  • Kim, Pil-Joo;Lee, Sang-Min;Yoon, Hong-Bae;Park, Yang-Ho;Lee, Ju-Young;Kim, Suk-Chul;Choe, Suk-Chul
    • Korean Journal of Soil Science and Fertilizer
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    • v.33 no.4
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    • pp.234-241
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    • 2000
  • Organic farming (OF) is regarded as alternative farming types against general farming system for sustainable agriculture, recently. However, there is little information on effects of OF on soil properties and watershed condition. In order to determine the effects of OF on soil properties, 36, 10 and 8 sites of organic farming (OF) fields of plastic film houses, paddy and orchard were selected in the national scale, respectively, to evaluate their chemical properties and phosphorus distributing characteristics. The average organic matter (OM) contents in organic farming fields were with $44g\;kg^{-1}$ in plastic film houses, $26g\;kg^{-1}$ in paddies and $39g\;kg^{-1}$ in orchard soils higher than the average OM contents in conventional farming (CF) soils. Available phosphates were accumulated to 986 in plastic film house soils and $754mg\;kg^{-1}$ in orchard soils, respectively, over the optimum range. Furthermore, total P (T-P) reached to $2.973mg\;kg^{-1}$ in plastic film houses and $2303mg\;kg^{-1}$ in orchards in OF soils. It could be attained by applying repeatedly low N/P ratio of manure-based compost. In two types of soils inorganic P was dominant with the ratio of 62~80% of T-P, and then residual and organic Ps followed. However. residual-P was dominant in paddy soils with the rate of 50% of T-P. Fractionation of soil extractable P showed that Ca-P was dominant with about $1,330mg\;kg^{-1}$ in upland soils in OF fields, which is affected by high soil pH of over 6.0. However. Fe-P of extractable P was dominant in paddy soils. Water-soluble P was very high with 65 and $26mg\;kg^{-1}$ in plastic film house and orchard soils in OF. From this results. OF regarded as an environment-friendly farming system may cause serious soil deterioration by accumulated phosphorus and may also cause water pollution.

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Progression of Restoration of Soil Physical Properties and Vegetation in Logging Roads - In Case of 9 Years Results after Construction of Logging Road - (벌채지내(伐採地內) 운재로(運材路)의 토양물리성(土壤物理性) 및 식생(植生)의 회복과정(回復過程) - 운재로(運材路) 개설(開設)이후 9년 경과의 경우 -)

  • Woo, Bo-Myeong;Kim, Kyung-Hoon;Park, Jae-Hyeon;Choi, Hyung-Tae
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.1 no.1
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    • pp.18-27
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    • 1998
  • To investigate the restoration progression on soil physical properties and vegetation at the surface of logging road affected by timber harvesting operation. This study was carried out at logging roads constructed from 1989 to 1994 in Mt. Baekwoon, Kwangyang, Chollanam-do. Judging from the analysis of soil hardness, there were significant changes in the depth of soil between 5 and 10cm. Soil hardness was recovered from the compacted condition to the natural forest condition after 9 years passed. Soil macroporous ratio (pF2.7) of topsoil was higher than that of deep soil. Soil moisture retention of topsoil was more improved than that of deep soil. From the view of soil bulk density, the necessary time for recovering to the undisturbed condition of forest soil was about 10 years in the logging road left. Soil physical properties such as soil bulk density and porous ratio were recovered as time passed. Improved soil physical properties promoted the plant recovery on the logging road surface. The dominant species on the logging roads were Comus kousa, Prunus sargentii as overstory species, Rubus crataegifolius, Lespedeza bicolor as understory species, and Saussurea gracilis, Pteridium aquilinum var. latiusculum as herbaceous species. The plant recovery of bank-slopes was faster than that of cut-slopes and road surface. In progress of year, average plant coverage were 70 to 90% in cut- and bank-slopes and 30 to 60% on the logging road, surface which was elapsed 9 years after logging road construction. Therefore, additional planting and seeding work could be effective to the soil condition and vegetation restoration.

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