• Title/Summary/Keyword: Laminar flow

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Accessory penis: A rare method of peno-urethral separation of sexual function and voiding following successful complex hypospadias reconstruction with a free ileum flap

  • Elia, Rossella;Pafitanis, Georgios;Ciudad, Pedro;Chen, Hung-Chi
    • Archives of Plastic Surgery
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    • v.46 no.4
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    • pp.381-385
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    • 2019
  • Hypospadias is a congenital malformation of the male genitalia. The reconstructive objectives are to obtain voiding with laminar flow and satisfactory sexual function. Several urethroplasty techniques have been described, but for perineal or revisional cases no single technique has shown robust success. In this study, we describe the expanded use of intestinal flaps for urethral reconstruction and report a peculiar request from a patient to undergo peno-urethral separation after successful hypospadias repair with a free ileum flap. A 51-year-old male patient with perineal hypospadias underwent several urethral reconstructive procedures with poor outcomes. A free ileum flap was attempted as a substitute for the urethra. Following successful reconstruction, separation of the neo-urethra (ileum) from the penile body was performed to address the patient's sexual expectations. A free ileum flap proved to be a reliable urethral substitute in perineal hypospadias reconstruction, with a successful outcome. The peno-urethral separation with the creation of an "accessory penis," however peculiar, optimized the results in terms of both sexual and urinary function. Anatomical restoration of the urethra and patient-reported expectations are the key to successful hypospadias reconstructive procedures. Sexual function outcomes and the patient's perception of success should not be underestimated, even when urinary function has been restored.

Cryopreservation of Hevea brasiliensis zygotic embryos by vitrification and encapsulation-dehydration

  • Nakkanong, Korakot;Nualsri, Charassri
    • Journal of Plant Biotechnology
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    • v.45 no.4
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    • pp.333-339
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    • 2018
  • The mature zygotic embryos of the Hevea brasiliensis were cryopreserved through the use of the vitrification and encapsulation/dehydration techniques. In all the experiments, the zygotic embryos were pre-cultured for three days in the MS medium supplemented with 0.3 M sucrose before they were used for the cryopreservation technique. In the vitrification procedure, the effect of the plant vitrification solutions (PVS2 and PVS3) and exposure time were studied. The highest survival rate (88.87%) and regrowth (66.33%) were achieved when the precultured zygotic embryos were incubated in a loading solution for 20 minutes at $0^{\circ}C$. They were subsequently exposed to PVS2 for 120 minutes at $0^{\circ}C$ and plunged directly into liquid nitrogen. Cryopreservation by the encapsulation-dehydration method was successfully done by leaving the encapsulated zygotic embryos in a laminar flow for 4 hours prior to plunging into a LN. The survival rate and regrowth of the encapsulated zygotic embryos were 37.50% and 27.98%, respectively. The cryopreserved zygotic embryos were able to develop into whole plants.

Estimation on Affecting Factors and Contribution Rate for Air Permeability of Sawdust as Bulking Agent on Composting (퇴비화 첨가재인 톱밥의 공기투과성에 미치는 영향요인 및 기여도 평가에 관한 연구)

  • Kim, Byung Tae
    • Journal of the Korea Organic Resources Recycling Association
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    • v.23 no.4
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    • pp.52-62
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    • 2015
  • This study estimated the contribution rates of inlet air flow, moisture content, air-filled porosity and particle size on the total pressure drop for the sawdust used as the bulking agent in the composting. The statistical model for pressure drop including the affecting factors was proposed.($R^2=0.998{\sim}0.950$) While the laminar air flow(v) and particle size(SIZE*v) had the positive relations to the total pressure drop, the turbulent air flow($v^2$), moisture content(MC*v) and air-filled porosity(AFP*v) had the negative relations. Total pressure drop sharply increased with increasing of the inlet air flow. And the most significant factors affecting to total pressure drop were the particle size(SIZE*v) as positive factor and air-filled porosity(AFP*v) as negative factor. The contribution rate to total pressure drop by the particle size(SIZE*v) was continuously increased with increasing of the inlet air flow, but the contribution rate by air-filled porosity(AFP*v) was decreased. And total pressure drop was little changed even though the increasing of moisture content above the range of dry moisture content 0.25. The contribution rates of affecting factors had the different tendencies with increasing of the moisture content, especially in the negative factors as air-filled porosity(AFP*v) and moisture content(MC*v). For effective composting process, it is preferable to select the sawdust with higher air-filled porosity as bulking agent to enhance the air permeability.

A Numerical Study on the Flow and Heat Transfer Characteristics of Aluminum Pyramidal Truss Core Sandwich (알루미늄 피라미드 트러스 심재 샌드위치의 열유동 특성에 관한 수치해석 연구)

  • Kang, Jong-Su;Kim, Sang-Woo;Lim, Jae-Yong
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.3
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    • pp.638-644
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    • 2019
  • In this study, the fluid flow and heat transfer characteristics within sandwich panels are investigated using computational fluid dynamics. Within the sandwich panels having periodic cellular cores, air can freely move inside the core section so that the structure is able to perform multi-functional roles such as simultaneous load bearing and heat dissipation. Thus, there needs to examine the thermal and flow analysis with respect to design variables and various conditions. In this regard, ANSYS Fluent was utilized to explore the flow and heat transfer within the pyramidal truss sandwich structures by varying the truss angle and inlet velocity. Without the entry effect in the first unitcell, the constant rate of pressure and the constant rate of Nusselt number was observed. As a result, it was demonstrated that Nusselt number increases and friction factor decreases as the inlet velocity increases. Moreover, the rate of Nusselt number and friction factor was appreciable in the range of V=1-5m/s due to the transition from laminar to turbulent flow. Regarding the effect of design variable, the variation of truss angle did not significantly influence the characteristics.

An Analytic Study on Laminar Film Condensation along the Interior Surface of a Cave-Shaped Cavity of a Flat Plate Heat Pipe

  • Lee, Jin-Sung;Kim, Tae-Gyu;Park, Tae-Sang;Kim, Choong-Sik
    • Journal of Mechanical Science and Technology
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    • v.16 no.7
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    • pp.966-974
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    • 2002
  • An analytic approach has been employed to study condensate film thickness distribution inside cave-shaped cavity of a flat plate heat pipe. The results indicate that the condensate film thickness largely depends on mass flow rate and local velocity of condensate. The increasing rate of condensate film for circular region reveals about 50% higher value than that of vertical region. The physical properties of working fluid affect significantly the condensate film thickness, such as the condensate film thickness for the case of FC-40 are 5 times larger than that of water. In comparison with condensation on a vertical wall, the average heat transfer coefficient in the cave-shaped cavity presented 10∼15% lower values due to the fact that the average film thickness formed inside the cave-shaped cavity was larger than that of the vertical wall with an equivalent flow length. A correlation formula which is based on the condensate film analysis for the cave-shaped cavity to predict average heat transfer coefficient is presented. Also, the critical minimum fill charge ratio of working fluid based on condensate film analysis has been predicted, and the minimum fill charge ratios for FC-40 and water are about Ψ$\_$crit/=3∼7%, Ψ$\_$crit/=0.5∼1.3% respectively, in the range of heat flux q"=5∼90kW/㎡.

Numerical Modelling of Vertical Drains Installed in Soft Deposit under Embankment (성토재 아래의 연약지반에 설치된 연직배수재의 수치모델링)

  • 이승래;김윤태
    • Geotechnical Engineering
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    • v.12 no.6
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    • pp.127-138
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    • 1996
  • The in-situ consolidation behavior of drainage system-installed deposits has three dimensional characteristics. Therefore, for an approximate 2-D plane strain consolidation analysis, it is necessary to convert the 3-D spatial flow of actual cases into the laminar flow simulated by the 2-D plane strain model. . In this paper, in order to properly model the effect of three dimensional characteristics, an equivalent and efficient model has been applied in a finite element technique for the analysis of the drainage system-installed soil deposits. The equivalent two dimensional model involves equivalent permeabilities and drainage widths. To validate the equivalent two dimensional model, three dimensional analyses were per formed by using the ABAQUS program and the results of 3-D analyses were compared with those of the 2-D analyses. By using the proposed equivalent model, one may be able to appropriately predict the consolidation behavior of drainage system-installed soft deposits.

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Behaviors of Premixed Flames and Triple Flames with its Concentration Difference in a Slot Burner (슬롯버너에서 농도차이에 따른 예혼합화염과 삼지화염의 거동)

  • Kim, Tae-Kwon;Jang, Jun-Young;Park, Jeong;Jun, Seong-Hwa;Miwa, Kei
    • 한국연소학회:학술대회논문집
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    • 2004.11a
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    • pp.85-90
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    • 2004
  • We have presented characteristics of a transitional behavior from a premixed flame to a triple flame in a lifted flame according to the change of equivalence ratio. The experimental apparatus consisted of a slot burner and a contraction nozzle for a lifted flame. As concentration difference of the both side of slot burner increases, the shape of flame changed from a premixed flame to a triple flame, and the liftoff height is decreased to the minimum value and then increase again. Around this minimum point, it is confirmed a transition regime from premixed flame to triple flame. Consequently, the experimental results of the liftoff height, flame curvature and luminescence intensity showed that the stabilized laminar lifted flame regime is categorized by regimes of premixed flame, triple flame and critical flame. In the visualization experiment of smoke wire, the flow divergence and redirection reappeared in premixed flame as well as triple flame. Thus we cannot express the flame front of lifted flame has a behavior of triple flame with only flow divergence and redirection. To differentiate triple flame and premixed flame, ${\Phi}$ value of partially premixed fraction is employed. The partially premixed fraction ${\Phi}$ was constant in premixed flame. In critical flame small gradient appears over the whole regime. In triple flame, typical diffusion flame shape is obtained as parabolic distribution type due to diffusion flame trailing.

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COMBUSTION CHARACTERISTICS OF HOMOGENEOUS CHARGED METHANE-AIR MIXTURE IN A CONSTANT VOLUME COMBUSTION CHAMBER

  • CHOI S. H.;CHO S. W.;JEONG D. S.;JEON C. H.;CHANG Y. J.
    • International Journal of Automotive Technology
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    • v.6 no.4
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    • pp.323-332
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    • 2005
  • A cylindrical constant volume combustion chamber was used to investigate the flow characteristics at the spark electrode gap and the combustion characteristics of a homogeneous charged methane-air mixture under various overall charge pressures, excess air ratios and ignition times. The flow characteristics, including the mean velocity and turbulence intensity, were analyzed with a hot wire anemometer. Combustion pressure development measured by piezoelectric pressure transducer, a flame propagation image acquired by ICCD camera and exhaust emissions measured by 2-valve gas chromatography were used to investigate effects of initial pressures, excess air ratios and ignition times on the combustion characteristics. It was found that the mean velocity and turbulence intensity had the maximum value around 200-300 ms and then decreased gradually to a near-zero value after 3000 ms and that the combustion duration was shorten and the flame speed and laminar burning velocity had the highest value under the condition of an excess air ratio of 1.1, an overall charge pressure of 0.15 MPa and an ignition time of 300 ms in the present study. The $CO_2$ concentration was proportional to the ignition time and overall charge pressure, the $CO_2$ concentration was proportional to the excess air ratio, and the UHC concentration was inversely proportional to the ignition time and overall charge pressure.

A Model-Analysis for Removal of Fire Fumes in a Road Tunnel during a Fire Disaster (도로터널내 화재 발생시 매연 제거를 위한 모델 해석)

  • 윤성욱;이희근
    • Tunnel and Underground Space
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    • v.7 no.2
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    • pp.100-107
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    • 1997
  • In case of a fire outbreak in a uni-directional road tunnel, the flow of traffic immediately behind the fire disaster will be stalled all the way back to the entrance of the tunnel. Furthermore, when the vehicle passengers try to flee away from the fire toward the entrance of the tunnel, the extremely hot fume that propagates in the same direction will be fatal to the multitudes evacuating, but may also cause damage to the ventilation equipments and the vehicles, compounding the evacuation process. This paper will present the 3-dimensional modelling analysis of the preventive measures of such a fume propagation in the same direction as the evacuating passengers. For the analysis, the fire hazard was assumed to be a perfect combustion of methane gas injected through the 1 m X 2 m nozzle in the middle of the tunnel, and the product of $CO_2$ as the indicator of the fume propagation. From the research results, when the fire hazard occurred in middle of the 400 m road tunnel, the air density decreased around the fire point, and the maximum temperatures were 996 K and 499 K at 210 m and 350 m locations, respectively, 60 seconds after fire disaster occurred, when the fumes were driven out only towards the exit-direction of the tunnel. By tracing the increase of $CO_2$ level over 1% mole fraction, the minimum longitudinal ventilation velocity was found to be 2.40 m/sec. Furthermore, through Analysis of the temperature distribution graphs, and observation of the cross-sectional distribution of $CO_2$ over 1% mole fraction, it was found that the fume did not mix with the air, but rather moved far in a laminar flow towards exit of the tunnel.

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Numerical Study of Thermo-Fluid Features of Electrically Conducting Fluids in Tube Bank Heat Exchangers Exposed to Uniform Magnetic Fields (관군 열교환기에서 균일 자기장에 의한 전기 전도성 유체의 열유동 특성에 관한 수치해석 연구)

  • Oh, Jin Ho;Kang, Namcheol;Park, Il Seouk
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.41 no.10
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    • pp.659-665
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    • 2017
  • When an electrically conducting fluid flows through a staggered tube bank, the heat transfer and fluid flow features are changed by the externally introduced magnetic field. This study provides a numerical investigation of this phenomenon. Heat and fluid flows are investigated for unsteady laminar flows at Reynolds numbers of 50 and 100 with the Hartmann number gradually increasing from zero to 100. As the Hartmann number increases, and owing to the effects of the introduced magnetic field, the velocity boundary layer near the tube wall is thinned, the flow separation is delayed downstream, and the shrinkage of a recirculation zone formed near the rear side is observed. Based on these thermo-fluid deformations, the resulting changes in the local and average Nusselt number are investigated.