• Title/Summary/Keyword: 변위손상

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A Numerical Analysis on the Shear and Hydraulic behavior of Single Rock Joint with Roughness (거칠기를 고려한 단일 절리의 전단, 수리적 거동에 대한 수치해석)

  • 이희석;이연규
    • Tunnel and Underground Space
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    • v.10 no.3
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    • pp.366-377
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    • 2000
  • The development of proper joint model, which can describe real phenomena exactly and still can be used easily, is one of the most important element for the analysis of the mechanical and hydraulic behavior of discontinuous rock mass. In this study, an elasto-plastic constitutive model of joint behavior considering asperity degradation was extended with the concept of first and second order asperities. The proposed model was implemented to numerical code with discrete finite joint element. The parametric study with the various asperity angles and degradation coefficients showed that the model can reproduce the shear behavior of typical rough joints well. Results of laboratory monotonic and cyclic shear tests were compared with those of numerical tests to validate the model. The hydraulic model considering the relations between gouge production and aperture was introduced to the mechanical mode1. In an attempt to examine the performance of the model, comparative numerical test was conducted. Permeability between joint surfaces increased rapidly at the first stage, but became nearly constant with increasing shear displacement due to gouge production and uniform variation of aperture distribution.

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Traumatic Contusion of ICR Mouse Brain by FPI : $^{1}\textrm{H}$ MR Spectroscopic Study (유체타진손상기법에 의한 ICR 쥐의 뇌손상: 자기공명분광법)

  • Park, Chi-Bong;Kim, Hwi-Yool;Jeun, Sin-Soo;Han, Young-Min;Han, Duk-Young;Kang, Young-Woon;Choe, Bo-Young
    • Progress in Medical Physics
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    • v.14 no.4
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    • pp.259-267
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    • 2003
  • In vivo $^1$H magnetic resonance spectroscopy (MRS) at 4.7 T was applied to investigate the cerebral metabolite changes of mice brain before and after experimental brain trauma. In vivo $^1$H MR spectra were acquired from a voxel covering right parietal cortex in normal brain, used as control subjects. After experimental brain trauma using the fluid percussion injury (FPI) method, $^1$H MR spectra were acquired from the same lesion three days after trauma. Metabolite ratios of the injured lesion were compared to those of controls. After trauma, N-acetylaspartate (NAA)/creatine (Cr) ratio, as a neuronal marker was decreased significantly versus controls, indicating neuronal loss. The ratio of NAA/Cr in traumatic brain contusion was 0.90$\pm$0.11, while that in normal control subjects was 1.13$\pm$0.12 (P=0.001). Choline (Cho)/Cr ratio had a tendency to rise in experimental brain contusion (P=0.02). Cho/Cr ratio after trauma was 0.91$\pm$0.17 while that before traumas was 0.76$\pm$0.15. Cho/Cr ratio was increased and this might indicate a inflammatory activity. However, no significant difference of [(glutamate+glutamine) (Glx)]/Cr was established between experimental traumatic brain injury models and normal controls. Lactate (Lac)/Cr ratio was appeared as a sign of shifted posttraumatic energy metabolism and increased versus controls. These findings strongly suggest that in vivo $^1$H MRS may be a useful modality for clinical evaluation of traumatic contusion and could aid in better understanding the neuropathologic process of traumatic contusion induced by FPI. In the present study, in vivo $^1$H MRS was proved to be a useful non-invasive method for in vivo diagnosis and monitoring of posttraumatic metabolism in models of brain contusion.

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DEVELOPMENTAL DISTURBANCES OF SUCCESSIVE PERMANENT TEETH BY TRAUMA TO THE PRIMARY TEETH (유치의 외상에 의한 계승 영구치의 발육 장애)

  • Kim, Ji-Young;Kim, Young-Jin;Kim, Hyun-Jung;Nam, Soon-Hyeun
    • Journal of the korean academy of Pediatric Dentistry
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    • v.37 no.2
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    • pp.260-266
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    • 2010
  • Trauma to the primary teeth may have an effect on the successive permanent teeth. Thus, the treatment plans should be focused on safety of their permanent teeth. The degree of developmental disturbances in those permanent teeth depends upon many factors including the age of the children, developmental conditions of the affected teeth, types and severities of trauma and time interval from the moment of trauma to the initial treatment the patients received. The complications of the effected permanent teeth vary from the mild enamel hypoplasia to the premature finishing of teeth development. In this study, children whose ages were 33 months, 5 years, and 26 months presented the developmental disturbances to their permanent teeth, which resulted from the trauma to the primary teeth: the intrusion, the avulsion, and the subluxation. There showed a mild complication in the case of subluxation resulting in enamel hypoplasia, but, the more severe complication of the root dilacerations occurred in the case of intrusion. Furthermore, the 5-year-old patient whose primary dentition was near in transition period to the permanent one, the more complicated problem such as stop of root development of the permanent teeth was resulted from the avulsion. Thus, one should assume that the types of trauma and the age of the children at the moment of trauma have different effects on those successive permanent teeth. In conclusion, when the trauma that causes changes in the position of primary teeth happened, it is important to arrange an appropriate treatment procedure considering the types of trauma and the developmental conditions of the permanent teeth.

Defining the hydraulic excavation damaged zone considering hydraulic aperture change (수리적 간극변화를 고려한 수리적 굴착손상영역의 정의에 관한 연구)

  • Park, Jong-Sung;Ryu, Chang-Ha;Lee, Chung-In;Ryu, Dong-Woo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.9 no.2
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    • pp.133-141
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    • 2007
  • The excavation damaged zone (EDZ) is an area around an excavation where in situ rock mass properties, stress condition, displacement, groundwater flow conditions have been altered due to the processes induced by the excavation. Various studies have been carried out on EDZ, but most studies have focused on the mechanical bahavior of EDZ by in situ experiment. Even though the EDZ could potentially form a high permeable pathway of groundwater flow, only a few studies were performed on the analysis of groundwater flow in EDZ. In this study, the 'hydraulic EDZ' was defined as the rock zone adjacent to the excavation where the hydraulic aperture has been changed due to the excavation by using H-M coupling analysis. Fundamental principles of distinct element method (DEM) were used in the analysis. In the same groundwater level, the behavior of hydraulic aperture near the cavern was analyzed for different stress ratios, initial apertures, fracture angles and fracture spacings by using a two-dimensional DEM program. We evaluate the excavation induced hydraulic aperture change. Using the results of the study, hydraulic EDZ was defined as an elliptical shape model perpendicular to the joint.

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Investigations of Vulnerable Members and Collapse Risk for System Support Based on Damage Scenarios (손상시나리오 기반 시스템 동바리 취약부재 도출 및 붕괴 위험성 분석)

  • Park, Sae In;Park, Ju-Hyun;An, Hyojoon;Lee, Jong-Han
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.1
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    • pp.33-40
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    • 2021
  • In recent years, many construction projects become large and complicated, and construction accidents also steadily increase, which grows interest in the safety and maintenance during construction. Many of the construction accidents are related to temporary construction and structures, but the safety evaluation and management during construction are unclear and indefinite due to the short operating period and continuous change in the formation of the temporary structure. The system support, which is one of the temporary structures to support the pouring load of concrete, was proposed to easily install and dismantle members with connection parts pre-manufactured. The use of the system support is increasing to improve the safety of the temporary structure during construction. However, the system support, which consists of multiple members, still has uncertainties in connectivity between members and supports of vertical members. Therefore, this study analyzed the structure, load, and accident cases of the system support to define the damage scenarios for member connection, support condition, and lateral displacement. The decrease rate of the critical load was analyzed according to the damage scenarios based on the defined unit structure of the system support. In addition, this study provided vulnerable members for each damage scenario, which could induce instability of the temporary structures during design, construction, and operation of the structure.

Seismic Fragility Evaluation of Bridges Considering Rebar Corrosion (철근 부식을 고려한 교량의 지진취약도 평가)

  • Shin, Soobong;Kong, Sina;Moon, Jiho;Song, Jong-Keol
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.34 no.4
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    • pp.231-241
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    • 2021
  • Although the deterioration of bridges may occur due to various causes, one of the representative causes is that the chloride used for deicing in the winter penetrates bridge members and results in corrosion. This study aims to quantify the ageing degree resulting from the corrosion of a bridge, apply it to the inelastic dynamic analysis model of the bridge, perform a seismic fragility analysis, and evaluate the relationship between the ageing degree and the seismic fragility curve. It is important to appropriately define the threshold values for each damage state in seismic fragility analyses considering the ageing degree. The damage state was defined using the results of existing experimental studies on the characteristics of the deterioration in the displacement ductility capacity of the pier, according to the ageing degree. Based on the seismic fragility analyses of six types of bridges divided by three types of bearing devices and two pier heights, it was found that the seismic vulnerability tends to increase with the ageing degree. The difference in seismic vulnerability with respect to the ageing degree exhibits a tendency to increase as the damage state progresses from slight to moderate, severe, and collapse.

Design and Characteristic Analysis of Snubber Circuits for IGBT devices (IGBT 소자를 위한 스너버회로 특성해석 및 설계)

  • Kim, Yoon-Ho;Lee, Jang-Sun;Kim, Yun-Bok;Ryu, Hong-Woo;Kim, Chan-Ki
    • Proceedings of the KIEE Conference
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    • 1997.07f
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    • pp.2227-2229
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    • 1997
  • IGBT는 턴-오프 동안 높은 dv/dt를 재인가하면 기생적 NPN 트랜지스터를 강제로 도전시킬 수 있는 변위전류를 유기하는데 이것은 제어의 손실과 잠재적인 디바이스의 손상을 가져오므로 적절한 스너버회로의 설계가 필요하다. 본 논문에서는 IGBT의 SPICE 모델을 이용하여 스위칭 특성을 해석하고, 적절한 스너버 회로의 설계 방식을 제시하였다.

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A Study of Crack Growth Behavior of Al2024 (Al2024의 균열성장거동에 관한 연구)

  • Lee, Won-Seok;Lee, Hyun-Woo
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.10
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    • pp.49-55
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    • 2000
  • This study describes the fatigue characteristics for Al2024 alloy, which is aircraft structure material. For this work, the plane-strain fracture toughness test, the plane-stress fracture toughness test and the crack growth rates test were conducted under the standard testing method. Test equipment is a computer-controlled closed-loop fatigue testing machine. The data of each test result is very important to aircraft structure reliability estimation, life prediction, design analysis, endurance analysis and damage tolerance analysis. In addition, the fatigue crack growth threshold($\DeltaKth$) value decreased as the stress ratio increased. Also, $\DeltaKth$ decreased as the thickness increased in LT, TL directions.

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Fatigue Life Evalution for Composite Blade by Using the Measured Load Spectrum and S-N Linear Damage Method (측정 하중 스펙트럼과 S-N 선형 손상 방법을 이용한 복합재 회전날개의 피로 수명 평가)

  • 공창덕;방조혁;김종식
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 1998.10a
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    • pp.20-20
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    • 1998
  • 풍력발전용 회전날개의 구조설계 요구조건은 크게 제한 강도 요구조건(Limit strength requirement), 강성도 요구조건(Stiffness requirement), 피로수명 요구조건(Fatigue life requirement)의 세 가지를 들 수 있다. 첫째로 제한 강도 요구조건은 운용기간 중에 발생할 수 있는 최대하중에 견딜 수 있어야 하며, 폭풍이나 돌풍의 상황에 대한 안전성을 의미한다. 둘째로 강성도 요구조건은 운용 중 공진을 피하기 위한 고유진동 수확보, 타워와의 충돌을 피하기 위한 변위의 제한, 공력성능의 변화를 피하기 위한 비틀림각의 제한등이 있다 셋째로 피로수명에 대한 요구조건은 요구피로수명 동안에 예상되는 반복하중에 견딜 수 있어야 한다.

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Structural Damage Detection Based on Composite Data of Static and Modal Test (정적변위와 진동모우드 특성치의 합성자료를 이용한 구조물의 손상도 추정)

  • 정범석;한종석
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1996.10a
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    • pp.147-155
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    • 1996
  • The purpose of present study is to propose a improved damage detection and assessment algorithm that has its basis on the method of system identification. In this approach, the complete sets of modes or displacements are not needed since the error response function involves only the difference between components of those vectors. The present approach also allows the use of composite data which is constitute of static displacements and eigenmodes. The effectiveness of the proposed statistical system identification method is investigated through simulated studies. A series of tests for predetermined damaged cantilever beam and bowstring truss structure have been conducted to verify the proposed method.

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