• 제목/요약/키워드: opening phenomenon

검색결과 124건 처리시간 0.031초

인장-압축하중 하의 파괴저항곡선의 감소현상 해석 (Analyses of the Decrease Phenomenon of Fracture Resistance Curve Under Tension-Compression Loading)

  • 윤병곤;석창성
    • 대한기계학회논문집A
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    • 제24권2호
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    • pp.378-385
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    • 2000
  • Fracture resistance (J-R) curves, which are used for elastic-plastic fracture mechanics analyses, decreased under tension-compression loading condition. This phenomenon was proved by several former researches, but the causes have not been clear yet. The objective of this paper is to investigate the cause of this phenomenon. On the basis of fracture resistance curve test results, strain hardening hypothesis, stress redistribution hypothesis and crack opening hypothesis were built. In this study, hardness tests, Automated Ball Indentation(ABI) tests, theoretical stress field analyses, and crack opening analyses were performed to prove the hypotheses. From this study, strain-hardening of material, generation of tensile residual stress at crack tip, and crack opening effects are proved as the causes of the decrease hypothesis.

음압격리병실에서의 병실 문의 개폐속도에 따른 실간 압력변동 및 공기교환량에 대한 해석적 연구 (A Numerical Study on Pressure Fluctuation and Air Exchange Volume of Door Opening and Closing Speeds in Negative Pressure Isolation Room)

  • 김준영;홍진관
    • 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
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    • 제24권1호
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    • pp.51-58
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    • 2018
  • Purpose: In this study, through the comparison of the pressure fluctuation and air exchange volume in negative isolation room according to the type of the door and door opening/closing speeds, which is one of the main factors causing the cross contamination of the negative pressure isolation room, establishes standard operating procedures to prevent cross contamination in high risk infectious diseases and isolation room design. Methods: In this study, the air flow each of the room is analyzed using ANASYS CFX CODE for flow analysis. In addition, the grid configuration of the door is constructed by applying Immersed Solid Methods. Results: The pressure fluctuation due to the opening and closing of the hinged door was very large when the moment of the hinged door opened and closed. Especially, at the moment when the door is closed, a pressure reversal phenomenon occurs in which the pressure in the isolation room is larger than the pressure in the anteroom. On the other hand, the pressure fluctuation due to the opening and closing of the sliding door appeared only when the door was closed, but the pressure reversal phenomenon not occurred at the moment when the sliding door was closed, unlike the hinged door. As the opening and closing speed of the hinged door increases, the air exchange volume is increased. However, as the opening and closing speed of the sliding door is decreased, the air exchange volume is increased. Implications: According to the results of this study, it can be concluded that the pressure fluctuation due to the opening and closing of the hinged door is greater than the pressure fluctuation due to the opening and closing of the sliding door. In addition, it can be confirmed that the pressure reversal phenomenon, which may cause to reduce the containment effect in negative pressure isolation room, is caused by the closing of the hinged door. Therefore, it is recommended to install a sliding door to maintain a stable differential pressure in the negative isolation room. Also, as the opening and closing speed of the hinged door is slower and the opening and closing speed of the sliding door is faster, the possibility of cross contamination of the room can be reduced. It is therefore necessary to establish standard operating procedures for negative isolation room for door opening and closing speeds.

소나무 구과의 열개 현상에 대한 비교형태학적 연구 (Comparative Morphological Aspects for the Opening Phenomenon in the Cone of Pinus densiflora)

  • 임동옥;김철환
    • 환경생물
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    • 제20권4호
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    • pp.386-390
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    • 2002
  • 소나무 구과의 열개현상을 비교형태학적 형질을 통해 관찰하였다. 어린 구과에서는 조직의 분화가 완전하게 일어나지 않았지만 각 기관으로 분화되는 과정임을 알 수 있었다. 성숙한 구과와 동일 크기의 녹색 구과에서 유관속다발과 보강조직의 수축률은 각각 1.0∼l.5%와 14.0∼l6.0%였다 실편의 종단부는 유조직과 보강세포로만 구성되어 있었고, 중앙부는 종단부와 기부 두께가 비슷하였다. 기부는 실편과 실편 받침이 있어 더욱 두꺼웠으며, 유관속다발보다 보강조직이 2배 이상 두껍게 나타났다. 결론적으로 구과가 완전 성숙하여 건조됨에 따라, 종단부는 보강조직으로만 구성되어있어 조직내 수축만 일어나고 중앙부는 두 조직간 두께가 비슷해 밖으로 휘지 않는다. 그러나 실편내 기부에서 배축면에 위치한 보강조직이 두껍고, 유관속다발보다 보강조직에서 수축률이 훨씬 크므로 실편의 기부가 밖으로 펴지게 되어 구과는 열개된다.

해양구조물용 TMCP강의 피로균열진전거동에 미치는 용접이방성 및 과대하중의 영향 (The effect of the excessive loading and welding anisotropy on the fatigue crack propagation behavior of TMCP steel for offshore structure)

  • 최성대;이종형
    • 한국생산제조학회지
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    • 제9권6호
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    • pp.82-88
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    • 2000
  • The effect of the welding for the offshore structure in the TMCP steel on the fatigue crack propagation rate and crack opening-and-closure behavior was examined. The welding anisotropy of the TMCP steel and crack propagation characteristics of the excessive loading were reviewed. (1) It seemed that a heat which was generated by the welding made a compressive residual stress over the base metal, so fatigue crack propagation rate was placed lower than in case of the base metal. (20 In the base metal, an effect of the anisotropy which has an effect of fatigue crack propagation rate of the excessive load and the constant amplitude laos was not found but in the welding material case, fatigue crack propagation rate of the excessive load in the specimen of the width direction was located in the retard side as compared with a specimen rolling direction. (3) A crack opening ratio of the used TMCP stel in this study was not changed after excessive loading but a retard phenomenon of crack propagation was observed. Consequently, it was thought that all of the retard phenomenon of crack propagation did not only a cause of the crack opening-and-closure phenomenon.

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고제어 성능을 가진 버터플라이밸브의 개도각에 따른 유체유동에 대한 연구 (A Study on the Fluid Flow According to the Opening Angle of a Butterfly Valve with High Control Performance)

  • 유성훈;박상희;황정규;양희조
    • 한국산업융합학회 논문집
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    • 제24권5호
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    • pp.617-623
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    • 2021
  • The objective of this study is to simulate valve flow coefficient and flow characteristics such as velocity and pressure distribution for butterfly valve. The size of the valve used in this study is 125A. The range of the valve opening angle was α=15°~70°, and it was changed by 5°. At the range of α=15°~30°, the valve flow coefficient K𝜐 gradually increased, and after α=30°, it increased rapidly. In the range of α=20°~70°, the pressure change in the -2.9cm~+2.9cm region in the pipe greatly depended on the opening angle and the position within the pipe. However, after +2.9cm, the pressure at the rear end of the valve was shown to depend only on the opening angle. At α=20°, Vortex shedding occurred for the first time at time t=0.25sec and continuously occurred in rear end of the valve over time. After α=45°, in the flow pattern at the rear end of the valve, the upward flow at the lower end of the valve and the flow at the upper end met each other to form a mixed flow. This flow phenomenon was shown to form a more intense mixed flow in the rear end region as the opening angle increased. Vortex flow occurred for the first time at α=15°, and the opening angle increased, the occurrence and disappearance of this flow phenomenon occurred periodically according to the certain flow region. The pattern of the pressure distribution in the region at the rear end of the valve showed a tendency to agree well with the results of the vorticity distribution.

매입형 영구자석 전동기에서 무부하시 공극 자속밀도 분포에 대한 Slot-Opening Effect를 고려한 보조 모델 (Assistant Model For Considering Slot-Opening Effect on No-load Air-gap Flux Density Distribution in Interior-type Permanent Magnet Motor)

  • 방량;김도진;홍정표
    • 전기학회논문지
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    • 제60권4호
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    • pp.759-765
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    • 2011
  • This paper proposes an effective assistant model for considering the stator slot-opening effect on air gap flux density distribution in conventional interior-type permanent magnet (IPM) motor. Different from the conventional slot-opening effect analysis in surface-type PM (SPM) motor, a composite effect of slot-opening uniquely existing in IPM motor, which additionally causes enhancement of air gap flux density due to magnet flux path distortion in iron core between the buried PM and rotor surface. This phenomenon is represented by a proposed assistant model, which simply deals with this additional effect by modifying magnetic pole-arc using an effective method. The validity of this proposed analytical model is applied to predict the air gap flux density distribution in an IPM motor model and confirmed by finite element method (FEM).

소아 피부 경화증 환자의 치험례 (LOCALIZED SCLERODERMA IN A CHILD : CASE REPORT)

  • 김은영;유승훈;김종수
    • 대한소아치과학회지
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    • 제32권2호
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    • pp.256-261
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    • 2005
  • 피부 경화증(scleroderma)은 만성 결체조직 질환으로 정확한 원인은 밝혀지지 않았으나 자가 면역 질환으로 알려져 있다. 대개 $30{\sim}50$세의 여성에서 호발하며 소아에서는 매우 드물다. 장기의 이환여부에 따라 국소성과 전신성 피부 경화증으로 분류할 수 있다. 국소적 형태는 예후가 양호하고 피부에만, 또는 피하 근육까지 이환되며, 내부 장기에는 이환되지 않는다. 전신적인 형태는 피부와 구강점막 및 위장계, 호흡계, 심혈관계 등을 포함하늘 전신 다발적 발생 (multisystemic involvement)이 특징적이다. 안면피부 이환시 작고 예리한 코, 무표정한 응시 (expressionless stare), 좁아진 입모양(narrow oral aperture) 등이 특징적이다. 대개 레이노 현상(Raynaud's phenomenon)이 존재하며 질환이 진행되면서 개구장애와 혀, 치은의 경화가 나타나게 된다. 피부 석회증(calcinosis cutis), 레이노현상(Raynaud's phenomenon). 식도 기능부전(esophageal dysfunction), 공지증(sclerodactyly), 모세혈관 확장증(telangioectasia)이 복합된 질환을 크레스트 증후군(CREST syndrome)이라 부른다. 피부 경화증의 치료는 국소적 및 전신적 스테로이드 치료, collagen cross-link inhibitor (D-penicillamine), 면역억제제 등을 사용한다. 개구제한의 치료는 설압자를 이용한 mouth stretching exercise를 통해 개선될 수 있다. 본 증례에서는 국소성 피부 경화증으로 진단되고 개구제한이 있는 6세 남아에게 아산화질소와 enflurane을 이용한 깊은 진정요법을 이용하여 상하악 제 1, 2 유구치의 우식치료 치험례를 보고한다.

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판상형 아파트의 창문개폐율에 따른 열쾌적도 분석 (Study on Thermal Comfort in according to Rate of Opening Windows of Flat-type Apartment)

  • 김성길
    • KIEAE Journal
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    • 제13권6호
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    • pp.93-98
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    • 2013
  • The purpose of this study is to analyze the rate of opening windows that makes residents of a flat-type apartment feel pleasant in summer time. A few conditions were simulated on the wind flow that pass through internal and external spaces of the flat-type apartment, utilizing CFX program. The simulation was made with the criteria for the rates of opening window at 20%, 50%, 70% and 100%. When the rate of window opening was more 50%, the wind speed(more than 1m/s) that makes the residents feel pleasant was observed in more 60% of the internal space. When the all windows of the apartments were opened, the heat island phenomenon was almost disappeared and the pleasant wind flow was more evenly distributed in the external spaces. If residents of apartments recognize the result of this study and practice in agrement on opening windows in summer, it is expected to contribute to minimizing the energy consumption for air conditioning.

Wind tunnel study on fluctuating internal pressure of open building induced by tangential flow

  • Chen, Sheng;Huang, Peng;Flay, Richard G.J.
    • Wind and Structures
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    • 제32권2호
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    • pp.105-114
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    • 2021
  • This paper describes a wind tunnel test on a 1:25 scale model of TTU building with several adjustable openings in order to comprehensively study the characteristics of fluctuating internal pressures, especially the phenomenon of the increase in fluctuating internal pressures induced by tangential flow over building openings and the mechanism causing that. The effects of several factors, such as wind angle, turbulence intensity, opening location, opening size, opening shape and background porosity on the fluctuating internal pressures at oblique wind angles are also described. It has been found that there is a large increase in the fluctuating internal pressures at certain oblique wind angles (typically around 60° to 80°). These fluctuations are greater than those produced by the flow normal to the opening when the turbulence intensity is low. It is demonstrated that the internal pressure resonances induced by the external pressure fluctuations emanating from flapping shear layers on the sidewall downstream of the windward corner are responsible for the increase in the fluctuating internal pressures. Furthermore, the test results show that apart from the opening shape, all the other factors influence the fluctuating internal pressures and the internal pressure resonances at oblique wind angles to varying degrees.

짧은 피로균열의 랜덤하중하의 균열닫힘 및 진전거동(Part II : 진전거동 및 진전수명예측) (Crack Closure and Growth Behavior of Short Fatigue Cracks under Random Loading (Part II : Growth Behavior and Growth Life Prediction))

  • 이신영;송지호
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2000년도 추계학술대회논문집A
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    • pp.141-146
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    • 2000
  • Crack closure and growth behavior of physically short fatigue cracks under random loading are investigated by performing narrow- and wide-band random loading tests for various stress ratios. The importance of the crack closure phenomenon is examined by predicting the growth lives of short cracks using obtained crack opening behavior. Artificially prepared two-dimensional, short through-thickness cracks are used. The crack opening load of short cracks is much lower under random loading than under constant-amplitude loading corresponding to the largest load cycle in a random load history. This result indicates that the largest load cycle in a random load history has an effect to enhance crack opening of short cracks. Most of the life prediction ratios are within the factor of 2 scatter band except several data at very short crack sizes, indicating that crack growth predictions based on the measured crack opening data are excellent. From the results obtained in this study, it can be concluded that crack closure is the primary factor governing fatigue crack growth of short cracks under random loading as well as under constant-amplitude loading.

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