• Title, Summary, Keyword: 파괴메카니즘

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Cyclic Seismic Performance of Reduced Beam Section Steel Moment Connections: Effects of Panel Zone Strength and Beam Web Connection Type (패널존 강도 및 보 웨브 접합방식이 RBS 철골 모멘트접합부의 내진거동에 미치는 영향에 관한 연구)

  • Lee, Cheol-Ho;Jeon, Sang-Woo;Kim, Jin-Ho
    • Journal of the Earthquake Engineering Society of Korea
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    • v.7 no.3
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    • pp.69-77
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    • 2003
  • This paper presents test results on eight reduced beam section(RBS) steel moment connections. The testing program addressed bolted versus welded web connection and panel zone(PZ) strength as key variables, Specimens with medium PZ strength were designed to promote energy dissipation from both PZ and RBS regions such that the requirement for expensive doublet plates could be reduced. Both strong and medium PZ specimens with a welded web connection were able to provide satisfactory connection rotation capacity for special moment-resisting frames. On the other hand, specimens with a bolted web connection performed poorly due to premature brittle fracture of the beam flange of the weld access hole. If fracture within the beam flange groove weld was avoided using quality welding, the fracture tended to move into the beam flange base metal of the weld access hole. Plausible explanation of a higher incidence of base metal fracture in bolted web specimens was presented. The measured strain data confirmed that the classical beam theory dose not provide reliable shear transfer prediction in the connection. The practice of providing web bolts uniformly along the beam depth was brought into question. Criteria for a balanced PZ strength improves the plastic rotation capacity while reduces the amount of beam distortion ore also proposed.

Quaternary Geology and Paleoecology of Hominid Occupation of Imjin Basin (임진강유역 구석기 공작의 고생태학적 배경)

  • Seonbok Yi
    • The Korean Journal of Quaternary Research
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    • v.2 no.1
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    • pp.25-50
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    • 1988
  • The survival of rich evidence of palaeolithic occupation found in the Imjin-Hant'an River basin was possible due to many fortuitous geological conditions provided there. Formation of the basalt plain in a narrow valley system which developed during the late Mesozoic insured the appearance of a basin of sedimentation in which archaeological sites would be preserved with relatively minor post-depositional disturbance. Geomagnetic and K-Ar dating indicates that lava flows occurred during the Brunes Normal Epoch. During and after the process of basin sedimentation, erosion of the plain was confined to the major channel of the present river system which developed along the structural joints formed by the lava flow. Due to characteristic columnar structure and platy cleavage of the basalt bedrock, erosion of the basalt bedrock occurred mainly in vertical direction, developing deep but narrow entrenched valleys cut into the bedrock. Consequently, the large portion of the site area remained intact. Cultural deposits formed on top of the basalt plain were left unmodified by later fluvial disturbances due to changes in the Hant'an River base-level, since they were formed about 20 to 40m above the modern floodplain. Sedimentological evidence of cultural deposits and palynological analysis of lacustrine bed formed in the tributary basin of the Hant'an River indicate that hominid occupation occurred in this basin under rapidly deteriorating climatic conditions. From three thermoluminescence dates, the timing of hominid occupation as represented by 'Acheulian-like' bifaces apparently occur sometime during 45,000 BP. Thus, deposition of cultural layers in this basin approximately coincides with the beginning of the second stadial of the final glacial, during which the Korean Peninsula must have had provided a sanctuary for prolonged human occupation.

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Growth of Zeolite-X Crystals on Metal Sieves Surface by Continuous Crystallization Method (연속적인 결정화 방법에 의한 금속 지지체상에서 Zeolite-X의 결정성장)

  • Park, Jeong-Hwan;Suh, Jeong-Kwon;Jeong, Soon-Yong;Lee, Jung-Min;Doh, Myung-Ki
    • Applied Chemistry for Engineering
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    • v.8 no.6
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    • pp.939-944
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    • 1997
  • The films of zeolite X on the surface of metal sieve were prepared by continuous crystallization method. It is known that the growth of zeolite crystal on the surface of metal is mainly dependent on the surface composition of metal sieve. In the present work, the zeolite nuclei could be easily formed as Cr content on the metal surface was removed by acid treatment. In order to investigate the proedure growing of zeolite crystal by the continuous crystallization method, the composition of zeolite X($6.36Na_2O-Al_2O_3-5.3SiO_2-190.8H_2O$)was supplied every 12hour. Then the mechanism and inter-relationship between the metal surface and nucleation are investigated. The results show that as the content of silica increases in the gel mixture, the nuclei of zeoilite are easily formed on the metal surface. Also, it was confirmed that the particle of zeolite stuck on the metal surface continues the linear growth. The particles are combined by the reaction of polycondensation, and finally become the shape of crystal. The sample synthesized by the film type was confirmed as zeolite X by the analyses of SEM and XRD.

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Development of numerical model for estimating thermal environment of underground power conduit considering characteristics of backfill materials (되메움재 특성을 고려한 전력구 열환경 변화 예측 수치해석모델 개발)

  • Kim, Gyeonghun;Park, Sangwoo;Kim, Min-Ju;Lee, Dae-Soo;Choi, Hangseok
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.19 no.2
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    • pp.121-141
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    • 2017
  • The thermal analysis of an underground power conduit for electrical cables is essential to determine their current capacity with an increasing number of demands for high-voltage underground cables. The temperature rises around a buried cable, caused by excessive heat dissipation, may increase considerably the thermal resistance of the cables, leading to the danger of "thermal runaway" or damaging to insulators. It is a key design factor to develop the mechanism on thermal behavior of backfilling materials for underground power conduits. With a full-scale field test, a numerical model was developed to estimate the temperature change as well as the thermal resistance existing between an underground power conduit and backfill materials. In comparison with the field test, the numerical model for analyzing thermal behavior depending on density, moisture content and soil constituents is verified by the one-year-long field measurement.

Seismic Performance of Gravity-Load Designed Post-Tensioned Flat Plate Frames (중력하중으로 설계된 포스트텐션 플랫플레이트 골조의 내진성능)

  • Han, Sang-Whan;Park, Young-Mi;Rew, Youn-Ho
    • Journal of the Earthquake Engineering Society of Korea
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    • v.14 no.3
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    • pp.31-38
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    • 2010
  • The purpose of this study is to evaluate the seismic performance of gravity-designed post tensioned (PT) flat plate frames with and without slab bottom reinforcement passing through the column. In low and moderate seismic regions, buildings are often designed considering only gravity loads. This study focuses on the seismic performance of gravity load designed PT flat plate frames. For this purpose, 3-, 6- and 9-story PT flat plate frames are designed considering only gravity loads. For reinforced concrete flat plate frames, continuous slab bottom reinforcement (integrity reinforcement) passing through the column should be placed to prevent progressive collapse; however, for the PT flat plate frames, the slab bottom reinforcement is often omitted since the requirement for the slab bottom reinforcement for PT flat plates is not clearly specified in ACI 318-08. This study evaluates the seismic performance of the model frames, which was evaluated by conducting nonlinear time history analyses. For conducting nonlinear time history analyses, six sets of ground motions are used as input ground motions, which represent two different hazard levels (return periods of 475 and 2475 years) and three different locations (Boston, Seattle, and L.A.). This study shows that gravity designed PT flat plate frames have some seismic resistance. In addition, the seismic performance of PT flat plate frames is significantly improved by the placement of slab bottom reinforcement passing through the column.

Characteristics of Rainfall, Geology and Failure Geometry of the Landslide Areas on Natural Terrains, Korea (우리나라 자연사면 산사태지역의 강우, 지질 및 산사태 기하형상 고찰)

  • Kim, Won-Young;Chae, Byung-Gon
    • The Journal of Engineering Geology
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    • v.19 no.3
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    • pp.331-344
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    • 2009
  • Large landslides occurred since 1990 on natural terrain, Korea were reviewed with the existing data to characterize them in terms of the condition of rainfall, geology and geometry. Ten landslide areas over the nationwide are selected for this study. Among them, five areas consist of granite basement, four areas of granite and metamorphic rocks and the remaining an area of gabbro. The basement lithology on which landslides most dominantly occurred is granite, on which 58% of landslides among the total 3,435 are taken place, the next dominant one is metamorphic rocks where 24% of landslides are occurred, and the remaining 18% are on the areas of volcanic and sedimentary rocks which are partly distributed in some areas. The landslide occurrences may depend on the rainfall intensities rather than durations. We applied the theories of Caine's threshold and Olivier's final response coefficient to the Korean cases. The rainfall conditions at the landslide areas were all satisfied enough with the landslide triggering conditions suggested by Caine and Olivier. The triggering mechanism and type of landslides may largely depend on the weathering and geomorphic characteristics of basement lithology. The granite areas are characterized by being relatively shallow but consistent weathering profiles and almost no outcrop, and therefore, shallow translational slides are dominant. Whereas metamorphic areas are characterized by consisting of steep slope, weathered outcrops on ridges and partly on flanks and irregular weathering profiles, and relatively large debris flows are dominant.

Reliability Design of the Hinge Kit System in Common Refrigerator Under Repetitive Load (상용 냉장고에서 반복 하중을 받는 힌지 키트 시스템(HKS)의 신뢰성 설계 연구)

  • Woo, Seong-woo;Lee, Jongkil
    • 대한공업교육학회지
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    • v.33 no.2
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    • pp.312-324
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    • 2008
  • To improve the newly designed HKS(hinge kit system) in common refrigerators, it was investigated the new robust methodologies. There were the study of failure modes, mechanisms in the marketplace, and the design parameters of HKS with various improvements using accelerated life testing. Based on the claimed marketplace product returns and 1st ALT reproduction, the fracturing and cracking occur in the housing of the HKS. The missing design parameters of the failed HKS in the design phase of the refrigerator was the housing hinge kit structure. The corrective action plans are the modifications of the housing hinge kit structure from the open supporting to all supporting structure. Based on 2nd ALTs, the fracturing and cracking occur in the torsion shaft. The missing design parameter was the roundness of torsion shaft. After a sequence of ALT testing, the levels of the missing design parameters were setup. The yearly failure rate and B1 life of the redesigned HKS, based on the results of ALT, were over 0.01 percent and 10 years, respectively. The parameter design through the inspection of the failed product, load analysis, and three rounds of ALT, was very effective in the new robust design methodologies of the mechanical system and this method can be applied to other design system.

Tension Test on the Bar-type Anti-buoyancy Anchors in the Weathered Rock (풍화암에 시공된 Bar Type 부력저항 앵커의 인장 시험)

  • Park, Chan-Duk;Lee, Kyu-Hwan;Ryu, Nam-Jae;Lee, Song
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.8 no.1
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    • pp.175-181
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    • 2004
  • This study is about a section where underground water level occurs at the underground 5m depth by the excavation of the ground, as a stream is adjacent to a excavation section of High Speed Railway ${\bigcirc}{\bigcirc}$ Station construction sections and a reservoir being always full of water is located at the left side of the construction section. Therefore this test is executed for the design and construction of buoyance anchors able to permanently prevent buoyance by the underground water level at working and for the stable construction and permanent smooth maintenance of structures. In this test, bar type anchors are divided according to their length and standard to execute test-anchor test, and In spot test, 9 test-anchors test, proof test to construction process, suitability test and acceptance test are executed 4 times to 9 test-anchors by dividing anchors according to the length of permanent anchor, the outer diameter of bar and boring diameter. Standard motion characteristic centering on load transmission and break mechanism of bar-type anchors for the prevention of buoyance will be showed in the thesis.

Flavonoid Biosynthesis: Biochemistry and Metabolic Engineering (Flavonoid 생합성:생화학과 대사공학적 응용)

  • Park, Jong-Sug;Kim, Jong-Bum;Kim, Kyung-Hwan;Ha, Sun-Hwa;Han, Bum-Soo;Kim, Yong-Hwan
    • Journal of Plant Biotechnology
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    • v.29 no.4
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    • pp.265-275
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    • 2002
  • Flavonoid biosynthesis is one of the most extensively studied areas in the secondary metabolism. Due to the study of flavonoid metabolism in diverse plant system, the pathways become the best characterized secondary metabolites and can be excellent targets for metabolic engineering. These flavonoid-derived secondary metabolites have been considerably divergent functional roles: floral pigment, anticancer, antiviral, antitoxin, and hepatoprotective. Three species have been significant for elucidating the flavonoid metabolism and isolating the genes controlling the flavonoid genes: maize (Zea mays), snapdragon (Antirrhinum majus) and petunia (Prtunia hybrida). Recently, many genes involved in biosynthesis of flavonoid have been isolated and characterized using mutation and recombinant DNA technologies including transposon tagging and T-DNA tagging which are novel approaches for the discovery of uncharacterized genes. Metabolic engineering of flavonoid biosynthesis was approached by sense or antisense manipulation of the genes related with flavonoid pathway, or by modified expression of regulatory genes. So, the use of a variety of experimental tools and metabolic engineering facilitated the characterization of the flavonoid metabolism. Here we review recent progresses in flavonoid metabolism: confirmation of genes, metabolic engineering, and applications in the industrial use.