• Title/Summary/Keyword: 유동륜

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Three-dimensional Reconstruction of Tricuspid Annulus with the Duran Ring (Duran Ring을 이용한 삼천판륜의 삼차원적 재건술)

  • Yoo Dong Gon;Kim Chong Wook;Park Chong Bin;Choo Suk Jung;Lee Jae Won
    • Journal of Chest Surgery
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    • v.38 no.1 s.246
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    • pp.88-90
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    • 2005
  • Tricuspid annuloplasty with the flexible Duran ring may result in a physiologic repair while maintaining the dynamic morphology of the tricuspid annulus. A method for a durable three-dimensional tricuspid annular reconstruction, which retains the plasticity and orifice area of the tricuspid annulus, is described.

Analysis of Compliance of Planetary Gears based on Floating Intermediate Rings (유성 기어 유동 중개륜의 컴플라이언스 해석)

  • Cho, Ihnsung
    • Tribology and Lubricants
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    • v.29 no.6
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    • pp.378-385
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    • 2013
  • An epicyclic gearing system is compact and lightweight. However, it is difficult to share the driving force equally because the system has closed gear trains with multiple driving points, and it always has geometrical errors in the elements. Thus, in the case of planetary gears, the first problem is how to distribute the load evenly to the numerous planets. The method widely used abroad for this purpose is to utilize the elastic deformation of the components of the structure. However, the deflection is very complicated, and it is very easy for vibration problems to occur because of the decrease in the natural frequencies. Therefore, to equalize the load on the planets, this paper discusses the principle and theory behind the functioning of a floating intermediate ring. This magnifies the displacement of a planet's center arising from the equilibrium of the load and the lubricating film pressure, which improves the compliance of the planets. The results show that load equalization of the planets is possible through this improvement in their compliance.

Effects of Flow Uniformity on Exhaust Pulsation Pressure in Catalytic Converter for Motorcycle (2륜 자동차용 촉매변환기내 배기맥동압력이 유동균일도에 미치는 영향)

  • Yi, Chung-Seub;Chung, Han-Shik;Jeong, Hyo-Min;Lee, Cheol-Jae;Bae, Tae-Yeol
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.4
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    • pp.108-114
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    • 2007
  • This research represents the catalytic converter for application in the motorcycle. We have to consider about catalytic converter for reducing exhaust gas strength regarding the displacement volume enlargement. The catalytic converter has been widely used to satisfy the regulations of pollutant emissions from automobiles. Recently, all catalytic converter researches are about automobile. Study about motorcycle catalytic converter has not been conducted yet. In this study, flow uniformity and pressure distribution were simulated in the monolithic inlet of catalytic converter for motorcycle. Exhaust pulsation pressure was set as transient condition about. It was found that flow uniformity shown in base model (0.85) was lower than megaphone model (0.98).

Numerical Analysis on the Pressure Characteristic and Flow Uniformity in a Ceramic Catalytic Converter for Motorcycle (2륜 자동차용 세라믹 촉매변환기내 압력특성과 유동균일도에 관한 수치해석)

  • Yi, Chung-Seub;Lee, Yonghun;Jeong, Hyomin;Chung, Han-Shik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.31 no.4
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    • pp.376-383
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    • 2007
  • This research represents the catalytic converter for application in the motorcycle. We have to consider about catalytic converter for reducing exhaust gas strength regarding the displacement volume enlargement. The catalytic converter has been widely used to satisfy the regulations of pollutant emissions from automobiles. Recently, all catalytic converter researches are about automobile. Study about motorcycle catalytic converter has not been conducted yet. In this study, flow uniformity and pressure distribution were simulated in the monolithic inlet of catalytic converter for motorcycle. Exhaust pulsation pressure was set as transient condition about. It was found that flow uniformity shown in base model (0.85) was lower than megaphone model (0.98).

Finite Element Analysis for the Prediction of Durability of Idler Wheel of Tracked Vehicle (궤도차량용 휠의 내구성 예측을 위한 유한요소 해석 기법 연구)

  • Lee, Kyoung-Ho;Roh, Keun-Lae;Lee, Young-Shin
    • Journal of the Korea Institute of Military Science and Technology
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    • v.12 no.5
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    • pp.676-682
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    • 2009
  • The idler wheel installed at the front side of the newly developed tracked vehicle didn't meet the durability requirement by showing the crack failure near the jointed region at the wheel during the field test. To find the crack developing mechanism we constructed finite element model for the idler wheel representing the behavior of interface between each suspension units, material properties from the material test data and actual loading conditions. This paper shows a result that maximum von Mises stress near the bolt hole on the outer rim is higher than inner idler coressponding to the actual test result and that result was reversed by adopting the reinforcement outside of the outer rim.

A Simulation on the Thermal and Fluid about Motorcycle Muffler (모터사이클 머플러 내부 열.유동에 관한 시뮬레이션)

  • Yi, Chung-Seub;Ji, Myoung-Kuk;Shim, Kyu-Jin;Chung, Han-Shik;Lee, Cheol-Jae;Bae, Jae-Young
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.2642-2647
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    • 2007
  • This study represents numerical study on the thermal and fluid flow characteristics of exhaust gas in a motorcycle muffler. The reference engine was used 124.cc small displacement. Numerical analysis with computational fluid dynamics(CFD) was carried out to investigate the exhaust gas that flow into a motorcycle muffler. The STAR-CD S/W used to three dimensional steady state CFD analysis in a muffler. And than We got the information of static pressure it is used to structural analysis ant the first baffle plate using the commercial CAE code ANSYS workbench. Exhaust gas flow third chamber from frist chamber and running second chamber. A simulation result shows that each chamber of muffler temperature is about 460 K, 445 and 463K and pressure is about 22,000 Pa, 16,000 Pa and 10,000 Pa.

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Aberrant Right Subclavian Artery with Dysphagia and Recurrent Pneumonia -A case report - (연하곤란 및 반복괵인 폐렴를 동반한 이상우쇄골하동맥 - 1예 보고 -)

  • 장원채;임영혁;임성철;오봉석
    • Journal of Chest Surgery
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    • v.37 no.3
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    • pp.282-285
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    • 2004
  • Aberrant right subclavian artery (ARSA) is an anomaly with a reported incidence of 0.5% to 2%. Most patients with an ARSA remain asymptomatic; however about to% of adult patients have compressive symptoms. A case is reported of a 64-year old female patient who had a few years of history of dysphagia and recurrent pneumonia. Angiography was performed, which demonstrated an ARSA with common origin of the right and left carotid arteries. Surgical correction was performed via right thoracotomy. The proximal aberrant artery was mobilized behind the esophagus. The distal, right subclavian artery was exposed, transected, and transposed with reimplantation into the aortic root by graft bypass.

A Study on the Geometry Decision of Catalytic Converter for Motorcycle (2륜 자동차 적용을 위한 촉매변환기 형상결정에 관한 연구)

  • Yi, Chung-Seub;Chung, Han-Shik;Jeong, Hyo-Min;Suh, Jeong-Se;Lee, Cheol-Jae
    • Transactions of the Korean Society of Automotive Engineers
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    • v.14 no.6
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    • pp.137-142
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    • 2006
  • This research represents the catalytic converter for application in the motorcycle. Present research model type is monolithic catalytic converter and this type have been widely used for satisfaction on and the regulations of pollutant emissions in automobiles. The flow characteristics in a single monolith automotive catalytic converter were investigated by using a computational simulation method without chemical reaction. So we limit the discussion to the effect of flow uniformity in the catalytic converter. Simulation result shows that the flow uniformity of megaphone type catalytic converter is higher than that of a base type. Therefore, the megaphone type is more suitable to motorcycle.

The Heat Transfer Performance of a Heat Pipe for Medium-temperature Solar Thermal Storage System (중온 태양열 축열조용 히트파이프의 열이송 성능)

  • Park, Min Kyu;Lee, Jung Ryun;Boo, Joon Hong
    • 한국신재생에너지학회:학술대회논문집
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    • 2011.05a
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    • pp.69-69
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    • 2011
  • 태양열 발전 플랜트에 사용되는 중고온 범위의 축열조에 고체-액체간 상변화를 수행하는 용융염을 축열물질로 사용하면 액체상 또는 고체상만으로 된 열저장 매체에 비해 축열조의 규모를 축소함과 동시에 축열온도의 균일성 향상에 기여할 수 있다. 중온인 $250{\sim}400^{\circ}C$ 범위에서 이용 가능한 용융염으로는 질산칼륨($KNO_3$), 질산리튬($LiNO_3$)등이 있다. 그러나 이러한 용융염의 가장 큰 단점은 열전도율이 매우 낮다는 것이며, 이로 인해 요구되는 열전달률을 성취하기 위해서는 많은 열접촉면적이 필요하다는 것이다. 이러한 단점을 극복하는 방법을 도입하지 않고서는 축열시스템의 소규화를 성취하는데 큰 효과를 가져올 수 없다. 한편 열수송 성능이 탁월한 히트파이프를 사용하면 열원 및 열침과 축열물질 사이의 열전달 효율을 증가시켜 시스템의 성능 향상과 동시에 소규모화에 기여할 수 있다. 중온 범위 히트파이프의 작동유체로서 다우섬-A(Dowtherm-A)는 $150^{\circ}C$이상 $400^{\circ}C$까지의 범위에서 소수에 불과한 선택적 대안 중 하나이다. 따라서 본 연구에서는 용융염을 사용하는 중온 태양열축열조에 적용 가능한 다우섬-A 히트파이프의 성능을 파악하여 기술적 자료를 제시하고자 하였다. 열원으로는 고온 고압의 과열증기, 그리고 열침으로는 중온의 포화증기를 고려하였다. 용융염 축열조를 수직으로 관통하는 히트파이프는 하단부에서 열원 증기와 열교환 가능하며, 중앙부에서 축열물질과 열교환하고, 상단부에서는 중온 증기와 접촉할 수 있도록 배치하였다. 축열모드에서는 히트파이프의 하단부가 증발부로 작동하고, 중앙부가 응축부로 작동하여 용융염으로 열을 방출하면 용융염의 온도가 상승하고 용융점에 도달하면 액상으로의 상변화가 진행되면서 축열이 활성화된다. 축열모드에서 히트파이프의 상단부는 단열부로 작동한다. 방열과정에서는 히트파이프의 하단부가 단열된 상태이고, 중앙부는 용융염으로부터 열을 받아 증발부로 작동하며, 상단부는 중온 증기로 열을 방출하므로 응축부로 작동한다. 즉, 축열시스템의 작동모드에 따라 하나의 히트파이프에서 증발부, 응축부, 단열부의 위치가 변하게 된다. 특히, 히트파이프의 중앙 부분이 응축부에서 증발부로 전환될 때에도 작동이 보장되려면 내부 작동유체의 연속적인 재순환이 가능해야 하므로, 일반 히트파이프에서와는 달리 초기 작동액체의 충전량을 증발부 전체의 체적보다 더 많이 과충전해야 한다. 이러한 히트파이프의 성능 파악을 위한 실험에서 고려한 변수들은 열부하, 작동액체의 충전률, 작동온도 등이며, 열수송 성능의 지표로서는 유효열전도율과 열저항을 이용하였다. 중온범위에서 적정한 작동온도를 성취하기 위해 실험에서는 전압 조절기로 열부하를 조절하는 동시에 항온조로 응축부의 냉각수 입구 온도를 제어하였다. 하나의 히트파이프에 대해서 최대 1 kW까지의 열부하에서 냉각수 입구 온도를 $40^{\circ}C$에서 $80^{\circ}C$ 범위로 변화시키면 히트파이프 작동온도를 약 $250^{\circ}C$ 내외로 조절 가능하였다. 히트파이프 작동액체 충전률은 윅구조물의 공극 체적을 기준으로 372%에서 420%까지 변화 시켰다. 실험 결과를 토대로 열저항과 유효 열전도율을 각각 입력 열유속, 작동온도, 작동액체 충전률 등의 함수로 제시했다. 동일한 냉각수 온도에서는 충전률이 높을수록 히트파이프의 작동온도가 감소하였다. 열저항 값의 범위는 최소 $0.12^{\circ}C/W$에서 최대 $0.15^{\circ}C/W$까지로 나타났으며 유효 열전도율의 값은 최소 $7,703W/m{\cdot}K$에서 최대 $8,890W/m{\cdot}K$까지 변화했다. 최소 열저항은 충전률 420%인 경우에 나타났는데 이때의 작동온도는 약 $262^{\circ}C$이었다. 히트파이프의 작동한계로서 드라이아웃(dry-out)은 충전률 372%의 경우에 열부하 950 W에서 발생하였으나, 그 이상의 충전률에서는 열부하 1060 W까지 작동한계 발생이 관찰되지 않았다. 실험 결과 본 연구에서의 히트파이프는 중온 태양열 축열조에 적용되어 개당 약 1 kW의 열부하를 이송하면서 축열물질 및 축방열 대상 유동매체와 열교환을 하는데 사용하는데 충분할 것이라 판단된다.

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Analysis of Recurred Mitral Regurgitation after Mitral Repair according to Procedure or Valve Related Causes (승모판막 성형술 후 재발의 원인에 대해 술기와 판막 요인에 대한 분석)

  • Shin Hong Ju;Yoo Dong Gon;Lee Yong Jik;Park Soon Ik;Choo Suk Jung;Song Hyun;Chung Cheol Hyun;Song Meong Gun;Lee Jae Won
    • Journal of Chest Surgery
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    • v.38 no.2 s.247
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    • pp.132-138
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    • 2005
  • Background: Mitral valve repair (MVP) is the optimal procedure for mitral regurgitation (MR), however, failure and subsequent reoperations are the limitations. The current study assessed the procedure in relation to the primary valve related causes of recurrent MR. Material and Method: MR was treated in 493 patients undergoing MVP from January of 1994 to January of 2002. The causes of MR were degenerative $(n=252,\;51.5\%),$ rheumatic $(n=156,\; 31.6\%),$ and others $(n=85,\; 16.9\%).$ Surgery comprised 446 ring annuloplasties $(90.5\%),$ 227 new chordae formations $(46\%),$ 125 quadriangular resections $(25.3\%),$ 28 chordae transfers $(5.7\%),$ and 8 Alfieri's stitches $(1.6\%).$ The mean follow up was $29.04\pm22.81$ months. Result: There were 5 early $(1.01\%)$, and 5 late deaths $(1.01\%).$ The reoperation rate was $1.42\%$. There were 45 $(9.1\%)$ recurrent MR (grade III or IV). Of these, 24 were procedure related including incomplete repair (n=14), discordant new chordae length (n=8) and others (n=2). In 21 patients, the cause was valve related including rheumatic disease progression (n=10), recurrent chordae elongation or prolapse (n=5) and others (n=6). Severe MR was higher after incomplete repair (p < 0.001), and valve related failure strongly correlated with rheumatic progression (p < 0.05). Conclusion: Since completeness of operation is the prime risk factor that determine the repair durability, intra-operative assessment of the initial repair with trans-esophageal echocardiography is essential.