• Title/Summary/Keyword: Block Wall

검색결과 332건 처리시간 0.025초

Navier-Stokes Analysis of Pitching Delta Wings in a Wind Tunnel

  • Lee, Yung-Gyo
    • International Journal of Aeronautical and Space Sciences
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    • 제2권2호
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    • pp.28-38
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    • 2001
  • A numerical method for the assessment and correction of tunnel wall interference effects on forced-oscillation testing is presented. The method is based on the wall pressure signature method using computed wall pressure distributions. The wall pressure field is computed using unsteady three-dimensional full Navier-Stokes solver for a 70-degree pitching delta wing in a wind tunnel. Approximately-factorized alternate direction implicit (AF-ADI) scheme is advanced in time by solving block tri-diagonal matrices. The algebraic Baldwin-Lomax turbulence, model is included to simulate the turbulent flow effect. Also, dual time sub-iteration with, local, time stepping is implemented to improve the convergence. The computed wall pressure field is then imposed as boundary conditions for Euler re-simulation to obtain the interference flow field. The static computation shows good agreement with experiments. The dynamic computation demonstrates reasonable physical phenomena with a good convergence history. The effects of the tunnel wall in upwash and blockage are analyzed using the computed interference flow field for several reduced frequencies and amplitudes. The corrected results by pressure signature method agree well with the results of free air conditions.

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경정맥(經靜脈) 내적(內的) Pacemaker 이식후(移植後) 발생(發生)한 복잡한 감염합병증(感染合?症)의 1치험례(治驗例) (Complicated Wound Infection Following Transvenous Endocardial Pacemaker)

  • 이두연;윤여준;조범구;홍승록
    • Journal of Chest Surgery
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    • 제9권2호
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    • pp.265-270
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    • 1976
  • Implantation of a permanent pacemaker is a widely accepted procedure for the patient with complete heart block.As a result of these device, the prognosis for patients with Adams-Stokes syndrome caused by complete A-V block and other cardiac arrhythmia have become much more optimistic. Permanent pacemaker implantation by means of a transvenous approach has made the operative risk much less and the procedure simpler. However, a number of complications have been reported in the literature regarding transvenous endocardial pacemaker implantation during the last a decade. The patient presented in this paper is a 26-year old girl who was implanted with a permanent pacemaker at 14 years of age because of a congenital A-V block. Following first exchange of pulse generator, the electrode (lead) was fractured, so that by the pulse generator, a change to the transvenous technique of implantation was made, After this, there were episodes of recurrent wound infection on three occasions, even though the site of pulse generator implantation was exchanged to the contralateral side of chest wall, massive doses of antibiotics were administered and sensitivity tests for coagulase positive staphylococcal infection were performed. Though there was no definite evidence of blood stream infection by blood culture, we decided not to use the transvenous technique and not to implant the pulse generator in the chest wall because the venous system and the entire anterior chest wall appeared to be diseased or contaminated by virulent pyogenic organisms. Finally this intractable systemic and local wound infection was successfully controlled by myocardial lead implantation via a subxiphoid approach and implantation of the pulse generator far down in the abdominal wall. The causes and routes of recurrent wound infection and possible blood born infection in this particular patient are still obscure. We strongly believe that myocardial pacemaker implantation is much safer than transvenous endocardial pacemaker implantation & myocardial pacemaker implantation is a definite method for controlling such an intractable wound infection. following transvenous pacemaker implantation.

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경계요소법에 의한 터보과급 가솔린기관 실린더블럭의 열전도 해석 (Analysis of heat conduction of cylinder block of turbocharged gasoline engine by boundary element method)

  • 김은태;최영돈;홍진관
    • 오토저널
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    • 제11권2호
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    • pp.41-54
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    • 1989
  • In this study, steady state heat conduction problems of the cylinder block of turbocharged gasoline engine were solved by the boundary element method. Surface of the cylinder block was divided by the triangular cells with constant potential. Temperature distribution, effective heat transfer coefficient of the cylinder block were investigated with variation of equivalence ratio, engine speed and boost pressure. The results show that maximum temperature of cylinder block increase rapidly with increasing engine speed and boost pressure. The monolithic structure of cylinder block results in sever inhomogeneity of inner wall temperature at the high engine speed and boost pressure.

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토목섬유 보강토옹벽의 기술현황 및 개발동향 (Current State and Technical Development of Geosynthetics-Reinforced Earth Wall)

  • 조삼덕;이광우
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2008년도 추계 학술발표회
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    • pp.141-157
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    • 2008
  • Since 1984, block-type reinforced earth wall with geogrid reinforcement has been widely used for retaining wall applications till now in Korea. The use of geogrid as a reinforcement in the reinforced earth wall is steadily increased in an amount over $6,500,000m^2$ in a year. However, still need exists that some problems in design and construction practices should be made to review. Therefore, this paper reviewed current state and development items of geosynthetics-reinforced earth wall technology on design and construction point of view.

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열복사에 의한 고체연료 점화 연구 (Ignition of a solid fuel by thermal radiation)

  • 김명효;백승욱
    • 대한기계학회논문집B
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    • 제22권3호
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    • pp.294-302
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    • 1998
  • Ignition characteristics of a vertical solid fuel plate with block have been investigated experimentally. For low radiant heat flux, ignition does not occur in a vertical solid fuel plate without block. In the case with the block on a vertical fuel plate, however, ignition can occur by increasing the residence time and the time to absorb the incident radiation flux by fuel vapor in gas phase. The ignition occurs below block and the point varies according to the block location and the block height. As the block height increases, the block locates at higher position, and the hot wall temperature increases, the ignition delay time decreases. Also as the initial temperature of fuel plate rises, the ignition delay time of the solid fuel plate decreases. The temperature distribution of solid fuel plate with block is nearly proportional to the radiant heat flux distribution. Therefore, the effect temperature by natural convection heat transfer is of the same order as that of inhibition of temperature increase by pyrolysis.

파괴면을 고려한 블록식 보강토 옹벽의 거동 특성 연구 (A Study on the Characteristics of Behavior of Block-type Reinforced Earth Retaining Wall Considering Failure Surface)

  • 윤원섭;박준규;채영수
    • 한국지반신소재학회논문집
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    • 제15권3호
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    • pp.13-26
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    • 2016
  • 본 연구에서는 최근 보강토 옹벽의 보강재와 시공법에 대한 국산화에 대한 요구로 전면벽체나 토목섬유 등을 대체할 수 있는 공법에 대한 개발 수요가 많아짐에 따라 경제적이고, 안정한 블록식 보강토 옹벽의 개발을 실시하고, 새롭게 고안된 블록식 보강토 옹벽에 대해 수치해석을 실시하여 거동특성에 대해 분석하였다. 제안된 보강토 옹벽은 첫째, 블록에 전단키를 두어 벽체를 일체화 하였으며, 둘째, 이론적인 파괴면에 보강재를 집중적으로 시공하여 전단 파괴면을 보강함으로써 옹벽의 안정성을 만족시키는 공법이다. 블록식 옹벽의 거동 특성을 분석하기 위해 해석에서 보강재의 사용 요소는 cable 요소와 strip 요소에 대해 수치해석을 실시하였으며, 보강재 길이, 간격, 블록의 일체화의 조건을 변화하여 해석하였다. 이러한 조건으로 해석한 결과 파괴면만 보강하는 경우보다 전면 벽체 블록과 체결을 위해 긴 보강재를 설치하는 경우가 보강효과를 증가시키고, 변위를 많이 구속할 수 있는 것으로 판단되었으며, 전면 벽체와 체결과 함께 일체화를 고려하기 위해 전단키를 설치하는 경우가 벽체를 개별요소로 해석한 경우보다 변위 구속효과가 있었다. 또한, 긴 보강재를 1간격과 2간격으로 시공한 경우의 발생 변형량은 AASHTO의 시공중 허용 발생변형량에 비해 작게 발생되어 본 연구에서 제안한 공법은 구조물의 중요도에 따라 보강재의 간격을 달리하여 현장에 적용할 수 있는 안정한 공법으로 판단된다.

경추 신경 손상에 의한 하지 강직 치료 시 초음파를 이용한 양측폐쇄신경차단술 -증례보고- (Ultrasound Guided both Obturator Nerve Block for Patient with Adductor Thigh Muscle Spasm -A case report-)

  • 권태명;김현주;문지연;서정훈;이평복
    • The Korean Journal of Pain
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    • 제22권1호
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    • pp.78-82
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    • 2009
  • Obturator nerve block has been used for analgesia of hip pain, relaxation of adductor muscle spasm related to cerebral palsy or paraplegia and in urologic surgery to prevent inadvertent obturator activity during lateral wall cystoscopy. Recently, ultrasound guidance has gained popularity in the field of peripheral nerve block and have been reported in some benefits. We describe here successfully performed both obturator nerve block under ultrasound guidance.

The Organization of Nanoporous Structure Using Controlled Micelle Size from MPEG-b-PDLLA Block Copolymers

  • Chang, Jeong-Ho;Kim, Kyung-Ja;Shin, Young-Kook
    • Bulletin of the Korean Chemical Society
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    • 제25권3호
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    • pp.351-356
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    • 2004
  • Selected MPEG-b-PDLLA block copolymers have been synthesized by ring-opening polymerization with systematic variation of the chain lengths of the resident hydrophilic and hydrophobic blocks. The size and shape of the micelles that spontaneously form in solution are then controlled by the characteristics of the block copolymer template. All the materials prepared in this study showed the tunable pore size of 20-80 ${\AA}$ with the increase of hydrophobic chain lengths and up to 660 $m^2$/g of specific surface area. The formation mechanism of these nanoporous structures obtained by controlling the micelle size has been confirmed using both liquid and solid state $^{13}C\;and\;^{29}Si$ NMR techniques. This work verifies the formation mechanism of nanoporous structures in which the pore size and wall thickness are closely dependent on the size of hydrophobic cores and hydrophilic shells of the block copolymer templates.