• Title/Summary/Keyword: 구조적 안정도

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A Study of Temperature Transform Algorithm of Distinguished Grids between Thermal and Structural Mesh for Satellite Design (인공위성 설계를 위한 열-구조 이종 격자 간 온도변환 알고리즘 연구)

  • Kim, Min Ki
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.43 no.9
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    • pp.805-813
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    • 2015
  • This paper introduces the development of temperature mapping code between thermal mesh and structural mesh in KARI Satellite Design Software. Generally, temperature distribution of a satellite varies with the time by the space environment of the orbit, so thermal expansion of the structure should be analysed in design of the satellite. For the sake of the coupled thermal structural analysis, an interpolation algorithm between two finite element heterogeneous grids has been proposed by which temperature transfer is successively conducted.

A Case Study on Design of Slope Failure in Expressway (고속도로 붕괴 절토 비탈면의 설계사례)

  • Yu, Byeong-Ok;Jang, Hyeon-Ik;Sim, Jae-Won;Han, Won-Jun;Na, Gwang-Hui
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.09a
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    • pp.713-727
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    • 2009
  • 절토비탈면의 붕괴는 주로 지질구조 적으로 취약한 구간에서 강우, 지진, 발파진동, 굴착 등의 외적인 요인이 작용하였을 때 비탈면의 붕괴가 수반되는 경우가 많으며 내적인 요인으로 작용하는 지질구조는 구조선의 종류에 따라 붕괴규모나 붕괴양상에서 상당한 차이를 보이는 특성을 보인다. 특히, 비탈면 붕괴는 단층이나 점토가 충전된 구조선에서 문제가 많이 발생되고 방향성이 뚜렷한 엽리 및 절리에서 붕괴가 빈번한 실정이다. 단층은 일반적으로 모든 암종에서 나타나는 지질구조이나 특히, 변성암중 편마암에서 붕괴빈도가 빈번하게 발생되고 점토층이 수반되는 경우에 심하다. 본 논문은 공사당시 비교적 규모가 크게 붕괴가 발생된 붕적층 절토 비탈면과 단층파쇄대 및 암질불량의 비탈면의 붕괴사례의 안정검토 사례를 소개하고자 한다.

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A Continuous Sliding Surface Transformed VSS by Saturation Function for MIMO Uncertain Linear Plants (다입출력 불확실 선형 플랜트를 위한 포화함수에 의한 연속 슬라이딩 면 변환 가변구조시스템)

  • Lee, Jung-Hoon
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.7
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    • pp.127-134
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    • 2015
  • In this note, a continuous sliding surface transformed variable structure systems by the saturation function is presented for MIMO uncertain linear plants. A discontinuous sliding surface transformed VSS is proposed theoretically. The closed loop exponential stability together with the MIMO existence condition of the sliding mode on the predetermined sliding surface is investigated. For practical applications, a continuous approximation of the discontinuous VSS is made by means of the saturation function. The discontinuity of the control input as the inherent property of the VSS is much improved in view of the practical aspects. Through a design example and simulation studies, the usefulness of the proposed continuous transformed VSS controller is verified.

Thermo-chemical Cycle with $NiFe_2O_4$ for Water-Splitting to Produce Hydrogen ($NiFe_2O_4$ 금속산화물의 열화학싸이클에 의한 물분해 수소생산기술)

  • Han, Sang-Bum;Kang, Tae-Bum;Joo, Oh-Shim;Jung, Kwang-Deog
    • Journal of Hydrogen and New Energy
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    • v.19 no.2
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    • pp.132-138
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    • 2008
  • 금속산화물의 열화학싸이클에 의한 수소생산 소재중 안정성이 우수하고 물분해 수소생산능이 비교적 우수한 $NiFe_2O_4$를 합성하여 열화학수소생산공정 적용시 최적화의 조건에 대하여 검토하였다. 합성한 $NiFe_2O_4$는 격자상수가 $8.34\;{\AA}$이었고, 뫼스바우어에 의해 구조는 Ni이 페라이트 구조인 $AB_2O$의 B위치에 주로 위치하는, A 및 B의 상대적 흡수강도가 57.9:42.1인 역스피넬구조를 보이고 있다. 이러한 구조의 $NiFe_2O_4$의 열적환원은 $610^{\circ}C$부터 시작하여 $1200^{\circ}C$에 이르는 동안 약 1.1 wt%의 무게감소가 관찰된다. 물에 의한 산화과정에서 수소가 발생하게 되는데, $1200^{\circ}C$이하의 환원온도에서 가능한 수소생산량은 약 $0.45\;cm^3/g{\codt}cycle$ 이었다. 산화 환원의 반복과정에서 $NiFe_2O_4$의 XRD에 의한 구조변화는 관찰되지 않아 매우 안정한 구조를 갖는다는 것을 보여주었다. 수소생산을 위한 무게당 싸이클당 수소생산양은 산화 환원과정의 온도범위가 가장 중요하였고 물의 접촉시간은 중요한 요소가 되지 않았다. 열적 환원과정에서 많은 양의 수소생산성능을 보이기 위해서는 $1200^{\circ}C$이상의 고온을 필요로 하는 것을 보여주었다.

Restoration design of step-pool sequence in mountain streams (산지하천의 스텝-풀 연속체 복원설계)

  • Kim, Ki Heung
    • Journal of Korea Water Resources Association
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    • v.53 no.1
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    • pp.29-43
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    • 2020
  • The purpose of this study is to propose the design criteria and detailed design model by reviewing the issues related to geometry, formation process, destruction process, hydraulic function, restoration and ecological function of the step-pool from the existing research results, to apply the step-pool sequences to river restoration. Based on the analysis and review results, the design criteria for the structure and size of the step-pool are presented as ratio of the step spacing and the channel width, ratio of the unit step slope and channel slope, and ratio of step height and the particle size. To ensure structural stability of the step, stability analysis method of overturning based on the keystone theory was proposed as a design criterion. As a detailed design concept, a layout model was proposed by applying the imbricating structure of keystones and arch stones to the planar, longitudinal and transverse configurations of the step-pool.

Abnormality of P2O5-Na2O-MgO Glasses by Raman and Infrared Spectroscopy (라만과 적외선 분광기를 이용한 P2O5-Na2O-MgO 유리의 이상성에 관한 연구)

  • Lee, Byung-Chul;Kwon, Young-Jun;Ryu, Bong-Ki
    • Journal of the Korean Ceramic Society
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    • v.39 no.3
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    • pp.265-271
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    • 2002
  • Density, water resistance, Raman and infrared spectroscopy were used to investigate the change of structural characteristics with the composition of phosphate galss samples made by melting method. The structural abnormality of the density and water resistance were rapidly increased and shown near the 60mol% of $P_2O_5$. This result could be explained by the structural changes owing to the strong shrinkage of glass network by the coordination of DBO(Double-Bonded Oxygen) around $Mg^{2+}$ cations. In addition, it seems that the DBOs coordinating $Mg^{2+}$ cations lose its characteristics of double bonding and resonate with other NBOs(Non-Bonding Oxygen).

Numerical Analysis of Concrete Lining and Rockbolt Behavior of the Tunnel Associated with Blast-induced Vibration (발파진동으로 인한 터널 콘크리트 라이닝과 록볼트 거동의 수치해석적 분석)

  • Jeon, Sang-Soo;Jang, Yang-Won
    • Journal of the Korean Society of Hazard Mitigation
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    • v.9 no.5
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    • pp.69-78
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    • 2009
  • Since the blast vibration induced by explosives of the powder possibly provide damage of the nearby structures adjacent to the tunnel, the stability of the nearby structures should be estimated. In this study, the stability of the tunnel based on the allowable peak particle velocity of the structures as well as allowable stress of the structures presented in the concrete structural design standard was estimated with respect to the stress of the concrete lining and axial force of the rockbolt during the blasting operation at the ground surface of the pre-existing tunnel. The analyses were carried out by using $FLAC^{2D}$ which is one of the programs developed based on the finite difference method. The bending compressive stress and shear stress of the concrete lining and axial force of the rockbolt were rapidly increased when the blasting operation was conducted near the tunnel.

A proposed model of limit equilibrium analysis for stability assessment of underground structure in liquefied ground during earthquakes (지진 시 액상화된 지반 내 지중 구조물의 안정성 평가를 위한 한계평형해석 모델 제안)

  • Ju-Young Oh;Jaehwan Lee;Seokbue Chang
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.26 no.5
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    • pp.435-448
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    • 2024
  • Liquefaction of the ground caused by earthquakes results in significant damage to underground structures such as tunnels, pipelines, manholes, and underground tanks. The uplift of underground structures due to liquefaction has been identified as a major cause of this damage. However, current design practices have not adequately considered the upward displacement of underground structures. This paper proposes an analytical solution based on the limit equilibrium method for cut-and-cover tunnels. Using this solution, a sensitivity analysis was performed on soil cover height, liquefaction depth, ground improvement, and ledge. It was confirmed that the contribution of each factor to the safety factor can be reasonably derived through changes in the safety factor. Although there are still many assumptions and uncertainties that need to be reviewed for their appropriateness, a conservative approach appears to mitigate a significant portion of these uncertainties. This study is meaningful as a stability evaluation method considering the uplift behavior characteristics of underground structures.

공정위, 1998년도 시장지배적사업자 지정$\cdot$고시

  • 한국공정경쟁연합회
    • Journal of Korea Fair Competition Federation
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    • no.29
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    • pp.35-44
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    • 1998
  • 공정거래위원회는 지난 ''97년 12월 29일 1998년도에 적용될 시장지배적사업자로 128개 품목의 311개 사업자(순사업자:188개)를 지정하고 ''98년 1월 1일부터 시행에 들어갔다. ''98년도에는 ''97년도 지정품목 및 사업자 중 13개 품목, 50개 사업자가 신규로 지정된 반면 14개 품목, 45개 사업자가 지정제외되어 지난해인 ''97년도에 비해 시장지배적사업자는 5개 증가한 반면, 시장지배적품목은 1개가 감소하였다. 이번에 공정위가 시장지배적품목 및 사업자의 변동상황을 분석한 결과, ''98년도에 신규로 시장지배적품목으로 지정된 품목은 주로 매출액의 증가에 따른 자연증가가 많았던 반면, 지정제외품목은 대부분 시장집중도 완화에 기인하고 있는 것으로 나타났다. 또한 시장지배적품목으로 계속 지정된 품목의 경우에도 사업자간의 시장점유율 순위와 상위 3사가 변동한 품목이 $32.3\%$에 달한 것으로 나타나 전반적으로 시장경쟁이 촉진되고 있는 것으로 분석되었다. 시장지배적품목의 시장집중도의 경우에는 1사 지배품목의 수와 3사 지배품목 중 $90\%$ 이상의 고집중품목의 수가 감소한 것으로 나타났다. 공정위는 앞으로 시장지배적사업자에 대하여는 최근의 경제상황을 감안하여 물가와 민생안정에 역점을 두고 공정거래법을 집행해 나갈 계획으로 있다. 이를 위해 가격남용, 출고조절, 공동행위 등 물가안정을 저해하는 시장지배적사업자의 법위반행위에 대한 감시를 강화하고, 특히 휘발유, 맥주, 라면 등 물가와 서민생활에 큰 영향을 미치는 독과점품목에 대하여 철저히 감시할 계획이며, 독과점시장 구조개선시책의 일환으로 ''96년부터 추진하고 있는 26개 우선개선대상품목의 경쟁촉진방안을 적극적으로 추진할 계획으로 있다고 밝혔다.

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Numerical Analysis of the Visco-plastic Behavior of Rock Mass Considering Continuum Joints and Rock Bolt Elements (연속체 절리와 록볼트 요소를 고려한 암반의 점소성 거동에 관한 수치해석)

  • 노승환;이정인;이연규
    • Tunnel and Underground Space
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    • v.14 no.3
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    • pp.215-228
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    • 2004
  • Rock mass contains discontinuities such as faults and joints, and their mechanical properties and spatial distribution dominate the stability of rock mass. Because the deformation of rock mass occurs discontinuities in many cases. However in the case of poor quality rock mass under high stresses, the deformation along intact rock can also influence the structure's stability. In this study, two dimensional finite element program was developed with a rheological model to analyze the stability of the structure excavated in jointed rock mass. The “equivalent material” approach was used assuming intact rock, joints and rock bolts as visco-plastic materials. The program was verified by analysing an intact rock model, a jointed rock mass model and a reinforced jointed rock mass model. The displacement was examined in each model with changing the intact rock behaviour as elastic and visco-plastic. In the case of poor quality rock mass under high stresses, e assumption of visco-plastic behaviour of intact rock resulted in larger displacement than when assuming elastic behaviour for intact rock. Therefore it is recommended to add intact rock's visco-plastic behaviour to the existing model, which only assumes visco-plastic behaviour of joints and rock bolts.