• 제목/요약/키워드: Open-tube

검색결과 311건 처리시간 0.027초

Internal Flow Analysis on an Open Ducted Cross Flow Turbine with Very Low Head

  • Wei, Qingsheng;Hwang, Yeong-Cheol;Choi, Young-Do
    • 한국유체기계학회 논문집
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    • 제17권5호
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    • pp.67-71
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    • 2014
  • Recently, the cross flow turbine attracts more and more attention for its good performance over a large operating regime at off design point. This study adopts a very low head cross flow turbine that has barely been studied before, and investigates the effect of air layer on the performance of the cross flow turbine. As open duct is applied in this study and free surface model is used between the air layer and water, an engineering definition of efficiency, instead of traditional definition of efficiency, is used. As torque at the runner fluctuates up and down at a reasonable limit, statistical method is used. Pressure and water volume fraction contours are shown to present the characteristics of air-water flow. With constant air suction in the runner chamber, the water level gradually drops below the runner and efficiency of the turbine can be raised by 10 percent. All considered, the effect of air layer on the performance of turbine is considerable.

농흉의 외과적 치료330 (Surgical Management of Thoracic Empyema.* - 330 cases -)

  • 김치경
    • Journal of Chest Surgery
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    • 제20권1호
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    • pp.65-70
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    • 1987
  • Empyema thoracis following pneumonia, pulmonary tuberculosis, trauma and surgical procedures continues to be a source of major morbidity and mortality. We retrospectively reviewed the hospital records of 330 patients [child:87, adult243] treated for empyema thoracis at Catholic Medical Center between 1964 and 1986. The causes of empyema in these patients were as follows: pneumonia [C***:66%, A***:30%], pulmonary tuberculosis [C:2%, A:20%], lung abscess [C:3%, A:5%], postoperative complication [C:0%, A:13%], trauma [C:1%, A:4%] and unknown origin [C:23%, A:17%]. Three patients in this series died of sepsis from necrotizing pneumonia. Staphylococcus [29.3%], Streptococcus [8.8%], E. coli [8%], Mycobacterium tuberculosis [7.9%], Klebsiella [7.4%], Pseudomonas [6.4%], Bacteroides [3.4%] were the organisms most commonly isolated. Bacterial isolates were single in 68.3%, multiple 7.5% and absent 24.2%. The type of organism did not correlate with severity of disease or eventual requirement for closed thoracotomy drainage, open thoracotomy drainage [Modified Eloesser*s procedure], thoracoplasty, decortication or pleuropneumonectomy. Successful methods of treatment included aspiration in 44%, tube thoracotomy in 66%, open thoracotomy drainage in 98.7%, thoracoplasty in 98%, decortication in 96% and pleuropneumonectomy in 73%. Initial mode of management in empyema thoracis are thoracentesis and closed thoracotomy drainage. If the initial management was failed, we performed another surgical procedures. Before 1973, we manage with Schede`s thoracoplasty in the postpneumonectomy empyema patients. But thoracoplasty, with or without the use of muscle flaps, is a hazardous operation in the poor-risk patients. The permanent, open thoracotomy drainage is a relatively minor operation which is well tolerated even by cachexic, septic patients. It controls infection, and sometimes results in the bronchopleural fistula closing spontaneously.

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Effect of open Mg sintering ambiance on the in-field critical current density of ex-situ MgB2

  • Sinha, Bhavesh B.;Jang, S.H.;Chung, Kookchae
    • 한국초전도ㆍ저온공학회논문지
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    • 제14권4호
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    • pp.12-15
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    • 2012
  • $MgB_2$ superconductor is highly sensitive to the Mg content. Even if the samples are synthesized with the appropriate looking stoichiometric ratio, the heat treatment leads to the loss of Mg either to ambiance or to MgO. To avoid it, either excess Mg is added in the starting powder or sealed ampoule annealing is employed. In this paper the effect of open Mg sintering ambiance on the ex-situ $MgB_2$ was studied to enhance its superconducting properties. The open Mg ambiance was created to avoid any overpressure of Mg by providing a hole in Fe tube used as sample holder. The decrease in resistivity of the synthesized sample was observed through the increased temperature dependence of electron-phonon interactions. A clear enhancement in the superconducting cross-sectional area and hence the in-field critical current density is obtained.

개수로 내 식생구간의 흐름저항 및 흐름특성에 관한 실험적 고찰 (Experimental Study of Flow Resistance and Flow Characteristics over Flexible Vegetated Open Channel)

  • 여홍구;박문형;강준구;김태욱
    • 한국환경복원기술학회지
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    • 제7권6호
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    • pp.61-74
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    • 2004
  • Hydraulic engineers and scientists working on river restoration recognize the need for a deeper understanding of natural streams as a complex and dynamic system, which involves not only abiotic elements(flow, sediments) but also biotic components. From this point of view, the role played by riverine vegetation dynamics and flow conditions becomes essential. Hydro-mechanic interaction between flow and flexible plants covering a river bed is studied in this paper and some previous works are discussed. Measurements of turbulence and flow resistance in vegetated open channel were performed using rigid and flexible tube. Measuring detailed turbulent velocity profiles within and above submerged and flexible stems allowed to distinguish different turbulent regimes. Some interesting relationships were obtained between the velocity field and the deflected height of the plants, such as a reduced drag coefficient in the flexible stems. Turbulent intensities and Reynolds stresses were measured showing two different regions : above and inside the vegetation domain. In flexible vegetated open channel, the maximum values of turbulent intensities and Reynolds stresses appear above the top of canopy. Method to predict a flow resistance in flexible vegetated open channel is developed by modifying an analytical model proposed by Klopstra et al. (1997). Calculated velocity profiles and roughness values correspond well with flume experiments. These confirm the applicability of the presented model for open channel with flexible vegetation. The new method will be verified in the real vegetated conditions in the near future. After these verifications, the new method should be applied for nature rehabilitation projects such as river restorations.

Outcomes of laparoscopic choledochotomy using cholangioscopy via percutaneous-choledochal tube for the treatment of hepatolithiasis and choledocholithiasis: A preliminary Vietnamese study

  • Loi Van Le;Quang Van Vu;Thanh Van Le;Hieu Trung Le;Khue Kim Dang;Tuan Ngoc Vu;Anh Hoang Ngoc Nguyen;Thang Manh Tran
    • 한국간담췌외과학회지
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    • 제28권1호
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    • pp.42-47
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    • 2024
  • Backgrounds/Aims: Hepatolithiasis and choledocholithiasis are frequent pathologies and unfortunately, with the current treatment strategies, the recurrence incidence is still high. This study aimed to assess the outcomes of laparoscopic choledochotomy using cholangioscopy via the percutaneous-choledochal tube for the treatment of hepatolithiasis and choledocholithiasis in Vietnamese patients. Methods: A cross-sectional study of patients with hepatolithiasis and/or choledocholithiasis who underwent laparoscopic choledochotomy using intraoperative cholangioscopy via percutaneous-choledochal tube at the Department of Hepatopancreatobiliary Surgery, 108 Military Central Hospital, from June 2017 to March 2020. Results: A total of 84 patients were analyzed. Most patients were females (56.0%) with a median age of 55.56 years. Among them, 41.8% of patients had previous abdominal operations, with 33.4% having choledochotomy. All patients underwent successful laparoscopic common bile duct exploration followed by T-tube drainage without needing to convert to open surgery. Most patients (64.3%) had both intrahepatic and extrahepatic stones. The rate of stones ≥ 10 mm in diameter was 64.3%. Biliary strictures were observed in 19.1% of patients during cholangioscopy. Complete removal of stones was achieved in 54.8% of patients. Intraoperative complications were encountered in two patients, but there was no need to change the strategy. The mean operating time was 121.85 ± 30.47 minutes. The early postoperative complication rate was 9.6%, and all patients were managed conservatively. The residual stones were removed through the T-tube tract by subsequent choledochoscopy in 34/38 patients, so the total success rate was 95.2%. Conclusions: Laparoscopic choledochotomy combined with cholangioscopy through the percutaneous-choledochal tube is a safe and effective strategy for hepatolithiasis and/or choledocholithiasis, even in patients with a previous choledochotomy.

다이오드 검출기를 이용한 초소형 X선관(Miniature X-ray Tube)의 반가층 측정 (HVL Measurement of the Miniature X-Ray Tube Using Diode Detector)

  • 김주혜;안소현;오윤진;지윤서;허장용;강창무;서현숙;이레나
    • 한국의학물리학회지:의학물리
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    • 제23권4호
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    • pp.279-284
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    • 2012
  • X선은 방사선 진단과 치료 분야에 있어서 다양하고 광범위하게 이용되고 있으며, 최근에는 방사선 치료용 초소형 X선관이 개발되었다. 초소형 X선관은 조사 목적 부위에 직접 삽입하여 사용되므로 제작 시준기에 따라 다양한 각도로 X선 조사가 가능하고, 검사 목적 외의 환자 피폭선량을 최소화한다. 이러한 초소형 X선관의 장점을 이용해서 X선 영상을 획득하는데 적용한다면 X선 진단 분야의 새로운 장을 열 것으로 기대된다. 하지만 초소형 X선관은 본래 치료용으로 설계되었기 때문에 진단용 장비에 적합한 시준기, 필터(added filter) 등이 필요하다. 따라서 자체 제작한 시준기와 필터를 적용하여 초소형 X선관의 빔 특성이 진단용에 적합한지 평가 하였고, 이를 위해서 다이오드 검출기를 이용하여 반가층을 측정하고 측정의 가능성을 평가하였다. 본 연구에서는 Si PIN Photodiode type인 Piranha 검출기(Piranha, RTI, Sweden)를 사용하여 필터 적용 유무에 따른 초소형 X선관의 반가층을 측정하고, 알루미늄 필터를 사용한 측정을 통하여 Piranha 검출기의 반가층 측정의 정확성을 평가하였다. 측정 결과에 따르면 초소형 X선관의 반가층은 필터의 장착에 따라 약 1.9배 증가하여 진단용 방사선 발생 장치의 적합성을 확인하였다. Piranha 검출기의 반가층 자동 측정값은 필터를 미장착한 경우에 실제 반가층 측정값에 비해 50% 높게 측정되어 적용이 불가능하나, 필터를 장착한 경우에는 실제 반가층 측정값과 약 15%의 차이로 감소되었다. 따라서 진단용 필터를 적용했을 경우는 Piranha 검출기의 반가층 자동측정이 가능하여 kV-X선 특성평가를 수월하게 수행할 것으로 기대된다.

Intact and Perforated Pulmonary Hydatid Cyst: A Comparative Study from Damascus, Syria

  • Almess, Mohammad;Ahmad, Basel;Darwish, Bassam
    • Journal of Chest Surgery
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    • 제53권6호
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    • pp.387-391
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    • 2020
  • Background: Hydatidosis is a major health problem around the world, especially in the Mediterranean region. Cysts can break open or develop secondary bacterial infections, altering the clinical presentation. Methods: Patients who underwent hydatid cyst surgery at Al-Mouassat University Hospital in Damascus, Syria between January 2006 and December 2017 were evaluated. Cases involving isolated hepatic cysts were excluded. The patients were divided into those with perforated hydatid cysts (group 1) and those with intact hydatid cysts (group 2). Results: This study included 224 cases: 113 in group 1 (50.4%) and 111 in group 2 (49.6%). The median chest tube duration, hospitalization time, and postoperative complication rate were higher in group 1 than in group 2 (p=0.003, p=0.002, and p=0.006, respectively). In both groups, the most common symptom was cough (present in 178 patients in total [79.5%]), while chest pain (121 patients [54%]) and dyspnea (113 patients [50.4%]) were also common. Cough, hemoptysis, fever, and expectoration of cystic contents were significantly more frequent in group 1 than in group 2 (p<0.001). Conclusion: The early discovery and treatment of intact pulmonary hydatid cysts reduced the hospitalization time, chest tube duration, and postoperative complication rate. Relative to intact cysts, perforated cysts are more complex and are associated with more expensive and time-consuming surgical treatment.

수직갱을 이용한 터널내 비정상 압축파의 피동제어 (Passive control of unsteady compression wave using vertical bleed ducts)

  • 김희동
    • 대한기계학회논문집B
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    • 제21권9호
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    • pp.1095-1104
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    • 1997
  • When a high-speed railway train enters a tunnel, a compression wave is generated ahead of the train and propagates along the tunnel, compressing and accelerating the rest air in front of the wave. At the exit of the tunnel, an impulsive wave is emitted outward toward the surrounding, which causes a positive impulsive noise like a kind of sonic boom produced by a supersonic aircraft. With the advent of high-speed train, such an impulsive noise can be large enough to cause the noise problem, unless some attempts are made to alleviate its pressure levels. For the purpose of the impulsive noise reduction, the present study investigated the effect of a vertical bleed duct on the compression wave propagating into a model tunnel. Numerical results were obtained using a Piecewise Linear Method and testified by experiment of shock tube with an open end. The results showed that the vertical bleed duct reduces the maximum pressure gradient of compression wave front by about 30 percent, compared with the straight tunnel without the bleed duct. As the width of the vertical bleed duct becomes larger, reduction of the impulsive noise is expected to be greater. However the impulsive noise is independent of the height of the vertical bleed duct.

곡관출구로부터 방출되는 펄스파에 관한 연구 (A Study on the Impulse Wave Discharged from the Exit of a Right-Angle Pipe Bend)

  • 이동훈;허성춘;권용훈;김희동
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 추계학술대회논문집B
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    • pp.634-639
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    • 2001
  • The current study addresses experimental and computational work of impulse wave discharged from the exit of two kinds of right-angle pipe bends, which are attached to the open end of a simple shock tube. The weak normal shock wave with its magnitude of Mach number from 1.02 to 1.20 is employed to obtain the impulse wave propagating outside the exit of the pipe bends. A Schlieren optical system visualizes the impulse wave discharged from the exit of the pipe bends at an instant. The experimental data of the magnitude of the impulse wave and its propagating directivity are analyzed to characterize the impulse waves discharged from the exit of the pipe bends and compared with those discharged from a straight pipe. Computational results well predict the experimented dynamic behaviors of the impulse wave. The results obtained show that a right-angle miter bend considerably reduces the magnitude of the impulse wave and its directivity toward to the pipe axis, compared with the straight pipe and right-angle smooth bend. It is believed that the right-angle miter bend pipe can playa role of a passive control against the impulse wave.

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Energy Balance by Carbon and Nitrogen Balance Technique in White Leghorn and Rhode Island Red Hens Fed Maize- and Broken Rice-Based Diets

  • Jadhao, S.B.;Tiwari, C.M.;Chandramoni, Chandramoni;Khan, M.Y.
    • Asian-Australasian Journal of Animal Sciences
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    • 제12권7호
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    • pp.1080-1084
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    • 1999
  • Carbon (C) and nitrogen (N) balance technique was used to determine energy balance in Rhode Island Red (RIR) and White Leghorn (WL) laying hens fed maize-and broken rice (BR)- based diets. Carbon and nitrogen intake and outgo were determined for three days on ad libitum fed diets followed by 2/3 of ad libitum intake for next three days. Carbon analysis was done by using four 'U' tubes in which carbon dioxide released during bomb calorimetry was absorbed on drierite in tube 1 and 2 whereas tube 3 and 4 contained sodalime self indicating granule. Carbon in $CO_2$ was determined by an open circuit respiration system. Energy retention (E, kcal) was calculated as E = 12.386 C (g) - 4.631 N (g). By regressing metabolisable energy (ME) intake on energy balance, maintenance ME requirement of RIR was 128 whereas, that of WL hens was $144kcal/kg\;W^{0.75}/d$. Effciency of utilization of ME for maintenance from BR-based diet in RIR hens was equal but in WL hens it was 11% less than maize-based diet.