• Title/Summary/Keyword: MPa

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Material Characteristics of Seawater-abrobed Carbon-Epoxy Composite under Hydrostatic Pressure Environment (정수압 환경에서 해수흡수된 Carbon-Epoxy 복합재의 기계적 특성)

  • Lee, Ji-Hoon;Rhee, Kyong-Yop;Park, Hoon-Jae;Lee, Sang-Mok
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.406-409
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    • 2004
  • In this study, we investigated compressive characteristics of seawater-absorbed carbon-epoxy composite under hydrostatic pressure environment. The hydrostatic pressures applied were 0.1 MPa, 100 MPa, 200 MPa, and 270 MPa. The results showed that the compressive elastic modulus increased about 10 % as the hydrostatic pressure increased from 0.1 MPa to 200 MPa. The modulus increased 2.3 % more as the pressure increased to 270 MPa. Fracture strength and fracture strain increased with pressure in a linear fashion. Fracture strength increased 28 % and fracture strain increased 8.5 % as the hydrostatic pressure increased from 0.1 MPa to 270 MPa.

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A Study of the Pressure Effect on the Compressive Fracture Toughness of Quasi-Isotropic Composites (준등방성 적충복합재에 있어 압력이 압축 파괴인성에 미치는 영향에 대한 연구)

  • 이경엽;곽대순;김상녕;이중희
    • Composites Research
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    • v.14 no.3
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    • pp.51-56
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    • 2001
  • It is known that the elastic modulus, maximum stress, and maximum strain of fiber-reinforced polymer composites are affected by high pressure. Fracture behavior is also known to be affected by high pressure. In this work, the pressure effect on the compressive fracture toughness of thick quasi-isotropic composites was investigated. Dog-bone type specimens of stacking sequence, [0$^{\circ}$/$\pm$45$^{\circ}$/90$^{\circ}$]$_{11s}$ were used. Compressive fracture tests were conducted under four pressure levels. The pressure levels applied were 0.1 MPa, 100 MPa, 200 MPa, and 300 MPa. Fracture toughness for each pressure level was determined from the compliance method. The results show that the compressive fracture toughness increases with increasing pressure. Specifically, fracture toughness increases 44% as the pressure increases from 0.1 MPa to 300 MPa.

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The Load Transfer Performance of Post-tension Anchorage with 2,400 MPa Strands (2,400 MPa 강연선용 포스트텐션 정착구의 하중전달성능)

  • Kim, Sun-Woo;Lho, Byeong-Cheol;Lim, Jung-Hoon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.22 no.6
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    • pp.63-71
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    • 2018
  • Strands with ultimate strength of 2,400 MPa was developed and applied in the KCI Code and the KS standard. A high-strength prestressed strand to be applied to a structure, a suitable anchorage system should be used together. Recently, a post tension anchorage for 2,400 MPa strands was developed. but there is not much research on performance evaluation. Therefore, in this study, structural analysis of local zone with 9 strands, 15 strands, and 19 strands anchorage were investigated respectively, which are most widely used for post tensioning anchorages with 2,400 MPa strands, according to PTI anchorage zone design method, and Load transfer performance from ETAG013 and/or KCI-PS101 was evaluated. Furthermore, the adequacy of the test was also analyzed by nonlinear numerical analysis. As results, the anchorages with 2,400 MPa strands satisfied the structural performance of the local area and satisfied the load transfer performance condition.

Comparison Study on Nondestructive Strength Equation Based on Probability for Bridges (확률론적 방법을 적용한 도로교량의 비파괴 압축강도식 평가)

  • Kim, Hun-Kyom
    • International Journal of Highway Engineering
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    • v.20 no.3
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    • pp.39-46
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    • 2018
  • PURPOSES: This study is to estimate nondestructive strength equation based on probability for bridges using field test data. METHODS : In this study, a series of the field inspection and the test have been performed on 297 existing bridges, in order to evaluate the bridges, based on the test results of the in-depth inspection, and the estimated strengths by means of the nondestructive strength equations are analyzed and compared with results of the core specimen strengths. RESULTS : According to results of analyses, In case of standard design compressive strength of concrete is 18MPa, 21MPa, similar reliability of RILEM equation were 0.89~0.90, but in case of standard design compressive strength of concrete is 35MPa, 40MPa were 0.4~0.56. According to standard design compressive strength of concrete is 40MPa, similar reliability of ultrasonic pulse velocity method equation were 0.56. CONCLUSIONS :RILEM equation had high similar reliability than other equation in case of standard design compressive strength of concrete is 18MPa, 21MPa, but had low similar reliability than other equation in case of standard design compressive strength of concrete is 35MPa, 40MPa. and ultrasonic pulse velocity method equation had low similar reliability than other equation in case of standard design compressive strength of concrete is 40MPa.

Key Recommendations for MPA Management in Korea (우리나라 해양보호구역의 효과적 관리를 위한 정책 제안)

  • Chae, Dong-Ryul
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.18 no.3
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    • pp.207-212
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    • 2012
  • The purpose of this paper is to overview Korean MPA, to figure out the problems of current system and to give policy suggestions for effective management for Korean MPAs. Results show that different types of MPAs are established based on different legislations but there is no effective control system for integrated management. In addition, Korean government can not use the function of MPAs due to the insufficient regulation for harmful activities within MPAs. Finally, this paper recommends four policy suggestions for effective management of Korean MPAs; legal requirements of MPA designation, establishment of national authority for MPA management, application of no-take MPAs for fisheries management and establishment of MPA network.

Mechanical Properties and Microstructures of Alumina Composites Reinforced with SiC Whiskers and TiC Particles (SiC 휘스커 및 TiC 입자 강화 알루미나 복합재료의 기계적 성질과 미세조직)

  • 이영규;김준규;조원승;최상욱
    • Journal of the Korean Ceramic Society
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    • v.37 no.8
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    • pp.792-798
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    • 2000
  • Alumina composites reinforced with SiC whiskers only or combinded with TiC particles were prepared by hot-pressing at 1850$^{\circ}C$ for 1h. The mechanical properties and microstructures of composites were investigated in this study. By of addition either 20 vol% SiC whiskers or 20 vol% TiC particles, the flexural strength fo alumina was increased from 360 MPa to 650 MPa or 730 MPa, respectively, and the KIC was also increased from 3.5 MPa$.$m1/2 to 5.5MPa$.$m1/2 or 4.4MPa$.$m1/2, respectively. In the case of composites with 20 vol% SiC whiskers and 2 vol% TiC particles. The flexural strength and KIC showed relatively high value of 800 MPa and 5.3MPa$.$m1/2, respectively. The improvement of mechanical properties was considered to be due to both the smaller average grain size and the crack deflection.

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Effects of Light, Temperature, Water Changes on Physiological Responses of Kalopanax pictus Leaves(V) - Physiological Responses by the Changes of Leaf Water Potential - (광, 온도, 수분 변화에 따른 음나무 엽의 생리반응(V) - 잎의 수분 포텐셜 변화에 따른 생리반응 -)

  • Han, Sang-Sup;Jeon, Doo-Sik;Sim, Joo-Suk;Jeon, Seong-Ryeol
    • Journal of Forest and Environmental Science
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    • v.22 no.1
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    • pp.76-82
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    • 2006
  • 1. This stuty was investigated in 6-year-old Kalopanax leaves in plantation forest. 2. The decrease in net photosynthesis rate began at -0.80 MPa water potential, and then approached zero at -2.50 MPa. The relative net photosynthesis rate which is 50% occurred at -1.70 MPa. The stomatal conductance increased temporarily until -1.00 MPa, and then rapidly decreased. At -2.50 MPa, the relative stomatal conductance was 7% of maximum value. 3. The stomatal transpiration rate increased temporarily until -1.00 MPa, and then rapidly decreased. At -2.50 MPa, the relative stomatal transpiration rate was about 17% of maximum rate. The water use efficiency rapidly decreased with decreasing water potential, and then approached about zero at -2.50 MPa. 4. With decreasing leaf water potential, the $CO_2$ content ratio. $C_i/C_a$ in intercellar rapidly increased. The vapor pressure deficit, VPD gradually increased until -2.00 MPa, and then rapidly increased.

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THE EVALUATION OF PERIODONTAL LIGAMENT CELLS OF RAT TEETH AFTER LOW-TEMPERATURE PRESERVATION UNDER HIGH PRESSURE (고압-저온 보관에 따른 쥐 치아 치주인대세포의 활성도 평가)

  • Chung, Jin-Ho;Kim, Jin;Choi, Seong-Ho;Kim, Eui-Seong;Park, Ji-Yong;Lee, Seung-Jong
    • Restorative Dentistry and Endodontics
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    • v.35 no.4
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    • pp.285-294
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    • 2010
  • The purpose of this study was to evaluate the viability of periodontal ligament cells of rat teeth after low-temperature preservation under high pressure by means of MTT assay, WST-1 assay. 12 teeth of Sprague-Dawley white female rats of 4 week-old were used for each group. Both side of the first and second maxillary molars were extracted as atraumatically as possible under tiletamine anesthesia. The experimental groups were group 1 (Immediate extraction), group 2 (Slow freezing under pressure of 3 MPa), group 3 (Slow freezing under pressure of 2 MPa), group 4 (Slow freezing under no additional pressure), group 5 (Rapid freezing in liquid nitrogen under pressure of 2 MPa), group 6 (Rapid freezing in liquid nitrogen under no additional pressure), group 7 (low-temperature preservation at $0^{\circ}C$ under pressure of 2 MPa), group 8 (low-temperature preservation at $0^{\circ}C$ under no additional pressure), group 9 (low-temperature preservation at $-5^{\circ}C$ under pressure of 90 MPa). F-medium and 10% DMSO were used as preservation medium and cryo-protectant. For cryo-preservation groups, thawing was performed in $37^{\circ}C$ water bath, then MTT assay, WST-1 assay were processed. One way ANOVA and Tukey HSD method were performed at the 95% level of confidence. The values of optical density obtained by MTT assay and WST-1 were divided by the values of eosin staining for tissue volume standardization. In both MTT and WST-1 assay, group 7 ($0^{\circ}C$/2 MPa) showed higher viability of periodontal ligament cells than other group (2-6, 8) and this was statistically significant (p < 0.05), but showed lower viability than group 1, immediate extraction group (no statistical significance). By the results of this study, low-temperature preservation at $0^{\circ}C$ under pressure of 2 MPa suggest the possibility for long term preservation of teeth.

A comparison of fixation methods using three-dimensional finite element analysis following anterior segmental osteotomy

  • Yun, Kyoung In;Park, Min-Kyu;Park, Myung-Kyun;Park, Je Uk
    • Journal of the Korean Association of Oral and Maxillofacial Surgeons
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    • v.38 no.6
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    • pp.332-336
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    • 2012
  • Objectives: This study sought to evaluate fixation methods and determine the best method for the postoperative stabilization of maxillary osteotomy. For our analysis we performed a three-dimensional finite element analysis of stress distribution on the plate, screw, and surrounding bone, as well as displacement onto the plate. Materials and Methods: We generated a model using synthetic skull scan data; an initital surface model was changed to a solid model using software. Modified anterior segmental osteotomy (using Park's method) was made using the program, and four different types of fixation methods were used. An anterior load of 100 N was applied on the palatal surface of two central incisors. Results: The Type 1 (L-shaped) fixation method gave stresses of 187.8 MPa at the plate, 45.8 MPa at the screw, and 15.4 MPa at the bone around the plate. The Type 2 (I-shaped) fixation method gave stresses of 186.6 MPa at the plate, 75.7 MPa at the screw, and 13.8 MPa at the bone around the plate. The Type 3 (inverted L-shaped) fixation method gave stresses of 28.6 MPa at the plate, 29.9 MPa at the screw, and 15.3 MPa at the bone around the plate. The Type 4 (I-shaped) fixation method gave stresses of 34.8 MPa at the plate, 36.9 MPa at the screw, and 14.9 MPa at the bone around the plate. The deflection of the plates for the four fixation methods was 0.014 mm, 0.022 mm, 0.017 mm, and 0.018 mm, respectively. Conclusion: The Type 3 (inverted L-shaped) fixation method offers more stability than the other fixation methods. We therefore recommend this method for the postoperative stabilization of maxillary osteotomy.

A study on the bonding strength of co-cured T800/epoxy composite-aluminum single lap joint according to the forming and additional pressures (동시 경화법으로 제조된 T800/에폭시 복합재료-알루미늄 단면겹치기조인트의 성형압력 및 부가압력에 따른 접착강도에 관한 연구)

  • Son, Dae-Sung;Bae, Ji-Hun;Chang, Seung-Hwan
    • Composites Research
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    • v.24 no.5
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    • pp.23-28
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    • 2011
  • In this paper, the bonding strengths of co-cured T800 carbon/epoxy composite-aluminum single lap joints with and without additional pressures were investigated using the pressure information induced by the fiber tension during a filament winding process. The specimens of all the tests were fabricated by an autoclave vacuum bag de-gassing molding being controlled forming pressures (absolute pressures of 0.1MPa, 0.3MPa and 0.7MPa including vacuum). A special device which can act uniform additional pressures on the joining part of the single lap joint specimen was designed to measure the bonding strengths of composite-aluminum liners of type III hydrogen pressure vessel fabricated by a filament winding process. After the three different additional pressures (absolute pressures of 0.1MPa, 0.3MPa and 0.7MPa) were applied to the specimens the effect of the additional pressures on the bonding strengths of the co-cured single-lap joints were evaluated.