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Side Walls (side + wall)
Selected AbstractsFull-scale study on combustion characteristics of an upholstered chair under different boundary conditions,Part 1: Ignition at the seat centerFIRE AND MATERIALS, Issue 6 2009Q. Y. Xie Abstract The objective of this work is to investigate the effects of boundary conditions on the combustion characteristic of combustible items in a room. A series of full-scale experiments were carried out in the ISO 9705 fire test room with an upholstered chair at four typical locations, i.e. at the middle of side wall, at the center of the room with the seat toward the door, at the center of the room with the seat toward inside of the room, at the room corner, respectively. Ignition was achieved through a BS No.7 wooden crib at the geometric center of the seat surface for each test. Besides the heat release rate (HRR), four thermocouple trees were placed around the chair to monitor detailed temperature distributions during the combustion process of an upholstered chair. The results indicated that the boundary conditions had some effects on the combustion behavior of a chair in a room. It was shown that there were clearly two main peak HRRs for the cases of a chair being clung to the side wall or at the corner. However, there was only one main peak HRR when the chair was placed at the center of the room, either outwards or inwards. In addition, the results of the two cases of chairs being at the center indicate that the maximum HRR (about 829,kW) for the chair seat toward the door was relatively larger than the maximum HRR (about 641,kW) for the chair seat toward inside of the room. It was suggested that the special complex structure of a chair was also a considerable factor for the effect of boundary conditions on the combustion behavior of a chair in an enclosure. Furthermore, the measured temperature distributions around the chair also illustrated the effects of boundary condition on the combustion behavior of a chair in a room. It was suggested that although HRR was one of the most important fire parameters, HRR mainly represented the comprehensive fire behavior of a combustible item. In order to develop more suitable room fire dynamic models, more detailed information such as the surrounding temperature distributions measured by the thermocouple trees are useful. Copyright © 2009 John Wiley & Sons, Ltd. [source] Heat transfer in high-aspect-ratio rectangular passage with skewed ribsHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 2 2002Takanari Okamura Abstract The heat transfer characteristics and flow behavior in a rectangular passage with two opposite 45° skewed ribs for turbine rotor blade have been investigated for Reynolds numbers from 7800 to 19,000. In this blade, the spanwise coolant passage at the trailing edge region whose thickness is very thin is chosen, so the channel aspect ratio (=width/height of channel) is extremely high, 4.76. Therefore the heat transfer experiment in the high-aspect-ratio cooling channel was performed using thermochromic liquid crystal and thermocouples. Furthermore, the calculation of flow and heat transfer was carried out using CFD analysis code to understand the heat transfer experimental results. The enhanced heat transfer coefficients on the smooth side wall at the rib's leading end were the same level as those on the rib-roughened walls. © 2002 Scripta Technica, Heat Trans Asian Res, 31(2): 89,104, 2002; DOI 10.1002/htj.10018 [source] Prediction of entrance length and mass suction rate for a cylindrical sucking funnelINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2010Dipti Prasad Mishra Abstract Conservation equations for mass, momentum and energy have been solved numerically for a cylindrical funnel with louvers (lateral openings on the side wall of the cylindrical funnel through which air can come into it) to compute the suction rate of air into the funnel. The nozzle placed centrally at the bottom of the cylinder ejects high-velocity hot gaseous products so that atmospheric air gets sucked into the funnel. The objective of the work is to compute the ratio of the rate of mass suction to that of the mass ejected by the nozzle for different operating conditions and geometrical size of the funnel. From the computation it has been found that there exists optimum funnel diameter and optimum funnel height for which the mass suction is the highest. The protruding length of the nozzle into the funnel has almost no effect on the mass suction rate after a certain funnel height. The louvers opening area has a very high impact on the mass suction rate. The entrance length for such a sucking funnel is strikingly much lower compared with a simple cylindrical pipe having uniform flow at the inlet at same Reynolds number. A new correlation has been developed to propose the entrance length for a sucking pipe, the rate of mass suction into it and the exhaust plume temperature over a wide range of operating parameters that are normally encountered in a general funnel operations of naval or merchant ship. Copyright © 2009 John Wiley & Sons, Ltd. [source] Hydrodynamics and mass transfer of gas,liquid flow in a falling film microreactorAICHE JOURNAL, Issue 5 2009Haocui Zhang Abstract In this article, flow pattern of liquid film and flooding phenomena of a falling film microreactor (FFMR) were investigated using high-speed CCD camera. Three flow regimes were identified as "corner rivulet flow," "falling film flow with dry patches," and "complete falling film flow" when liquid flow rate increased gradually. Besides liquid film flow in microchannels, a flooding presented as the flow of liquid along the side wall of gas chamber in FFMR was found at high liquid flow rate. Moreover, the flooding could be initiated at lower flow rate with the reduction of the depth of the gas chamber. CO2 absorption was then investigated under the complete falling flow regime in FFMR, where the effects of liquid viscosity and surface tension on mass transfer were demonstrated. The experimental results indicate that kL is in the range of 5.83 to 13.4 × 10,5 m s,1 and an empirical correlation was proposed to predict kL in FFMR. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Morphology control of GaN nanowires by vapor-liquid-solid growthPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008Y. Inoue Abstract We synthesized GaN nanowires on sapphire substrate by metal organic chemical vapour deposition. The GaN nanowires were grown via vapor-liquid-solid (VLS) growth catalyzed with Ni thin film. Shape of nanowires depended on the substrate temperature and the growth pressure. The wire-like structure with high aspect ratio changed into the tapered structure with increasing substrate temperature, and with increasing the growth pressure. This dependency was attributed to the change of the surface diffusion length of source atoms. The VLS growth of GaN nanowire was revealed that the source species, absorbed at the eutectic droplet, came along the side wall of the nanowire as well as other semiconductor nanowires. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Preparation of three-dimensional structure controllable nanofibers by electrospinningPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2008Jian-Feng Zhang Abstract The size of "bowl-like" structures woven by nanofibers could be controlled by adjusting the distance from the nozzle to a modified collector and the voltage applied to the electrospinning device. More interestingly, the nanofibers in the side wall of the "bowl" could vibrate up and down with the changing of the voltage. This voltage-induced vibration might have potential applications for bio-mimic process and micro-motor devices. Copyright © 2008 John Wiley & Sons, Ltd. [source] A Novel Femoral Arterial Cannula to Prevent Limb Ischemia During Cardiopulmonary Support: Preliminary Report of Experimental and Clinical ExperiencesARTIFICIAL ORGANS, Issue 7 2006Yoshiro Matsui Abstract:, Distal limb ischemia may occur as a serious complication related to the use of femoral cannulation during veno-arterial cardiopulmonary support (CPS). We developed a simple cannula for femoral arterial cannulation with two holes in the side wall, which could provide the distal limb blood flow without additional cannulation or surgical procedure. This cannula can be inserted into the femoral artery by routine Seldinger technique. The distal blood flow from the side holes can be confirmed by Doppler detector without specialized techniques. In porcine experimental model, the distance between the position where the blood flow was first detected and those where the blood leakage took place was at least more than 10 mm. When this cannula and its side holes were adequately positioned, the mean distal limb flow ranged from 75 to 90 mL/min under CPS at a flow of 1.5 L/min. We employed this cannula for six patients in clinical settings. Three patients showed a good distal limb blood flow at the introduction position without its adjustment. The other three patients showed distal limb ischemia at the introduction position, but the limb ischemia was soon recovered after a slight adjustment of its position. There was no blood leakage from the percutaneous entry into the artery in all cases. We currently use this cannula as the first choice for patients undergoing a prolonged CPS. [source] The interaction of ground, TBM and segment lining with closed shield machines / . Interaktion Untergrund, Tunnelvortriebsmaschine und Tübbingausbau bei geschlossenen SchildmaschinenGEOMECHANICS AND TUNNELLING, Issue 5 2010Dipl.-Ing. Mechanised tunnelling - Maschineller Vortrieb Abstract The article explains the interaction of the overall system of ground, TBM and segment lining based on recent experience of projects using TBMs with active face support in Austria and abroad. The alternating dependencies and their consequences for tunnel construction are discussed in more detail. Of particular interest is the influence of the support medium and how it functions at the face and the tunnel side walls. The interaction of support pressure, thrust force and the centre of gravity of the TBM and its effect on steering behaviour are also considered. The effects of the compression of the segment tube by the TBM (prestress) are considered in relation to the improvement of the bedding and the problem of floating. Der Beitrag beleuchtet die Interaktion des Gesamtsystems "Untergrund , Tunnelvortriebsmaschine , Tübbingausbau" basierend auf aktuellen Erfahrungen zuletzt realisierter Projekte im In- und Ausland bei TVM-Einsätzen mit aktiver Ortsbruststützung. Dabei wird insbesondere auf die wechselweisen Abhängigkeiten und deren Auswirkungen auf die Tunnelherstellung eingegangen. Ein Schwerpunkt liegt beim Einfluss des Stützmediums und der zugehörigen Wirkungsweise an der Ortsbrust und der Tunnellaibung. Berücksichtigung findet die Wechselwirkung von Stützdruck, Vortriebskraft und der Schwerpunktlage der TVM auf deren Steuerverhalten. Die Auswirkung des Zusammendrückens der Tübbingröhre durch die TVM (Vorspannung) wird in Bezug auf die Bettungsverbesserung und die Problematik des Aufschwimmens betrachtet. [source] An efficient finite difference scheme for free-surface flows in narrow rivers and estuariesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2003XinJian ChenArticle first published online: 13 MAY 200 Abstract This paper presents a free-surface correction (FSC) method for solving laterally averaged, 2-D momentum and continuity equations. The FSC method is a predictor,corrector scheme, in which an intermediate free surface elevation is first calculated from the vertically integrated continuity equation after an intermediate, longitudinal velocity distribution is determined from the momentum equation. In the finite difference equation for the intermediate velocity, the vertical eddy viscosity term and the bottom- and sidewall friction terms are discretized implicitly, while the pressure gradient term, convection terms, and the horizontal eddy viscosity term are discretized explicitly. The intermediate free surface elevation is then adjusted by solving a FSC equation before the intermediate velocity field is corrected. The finite difference scheme is simple and can be easily implemented in existing laterally averaged 2-D models. It is unconditionally stable with respect to gravitational waves, shear stresses on the bottom and side walls, and the vertical eddy viscosity term. It has been tested and validated with analytical solutions and field data measured in a narrow, riverine estuary in southwest Florida. Model simulations show that this numerical scheme is very efficient and normally can be run with a Courant number larger than 10. It can be used for rivers where the upstream bed elevation is higher than the downstream water surface elevation without any problem. Copyright © 2003 John Wiley & Sons, Ltd. [source] Metal Corrosion and its Impact on Glass Tempering Furnace DesignINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2010Peter Tiernan A reliable well-designed tempering furnace is considered to be the cornerstone of any modern glass-processing facility. This paper addresses a series of engineering anomalies encountered during the commissioning of such a glass-processing furnace. Following the installation of a furnace in a European facility, small black deposits were noticed on both the silica-fused rollers used to transport the glass through the hearth of the furnace and on the processed glass surface itself. EDAX and scanning electron microscopy investigations indicated conclusively that the deposits were primarily constituted of sodium sulfate and trace elements consistent with stainless steel (chromium, iron, and nickel). Traditionally, high-density glass fiber was used to insulate the roof walls and side walls of tempering furnaces; however, it was noticed in this particular case that rolled stainless steel sheeting (SS316) was used. Chemical and X-ray diffraction analyses were used to pinpoint the origin of the deposits. It was determined that poor material selection choices taken during the design stage of the furnace in question were at fault. The combination of stainless steel and sulfur dioxide (SO2 is used as a lubricant to prevent scuffing) at elevated temperatures (>650°C) generated droplets of sodium sulfate, which condensed due to the convectional flow of the heat currents within the oven. These droplets scorched the glass surface and destroyed the fused silica rollers. As a recommendation, the usage of stainless steel and other nonrefractory metals should be avoided in the design of any future glass tempering furnaces. [source] Numerical study of solid particle erosion on the tubes near the side walls in a duct with flow past an aligned tube bankAICHE JOURNAL, Issue 1 2010Zeli Wang Abstract Computational fluid dynamic (CFD) tool has been applied to investigate the erosion of duct walls and that of tubers (10 × 10 aligned tube bank in the duct) near side walls, which is caused by coal ash particle impaction. The flow field is obtained by using direct numerical simulation (DNS) method. The coupling between tubes and flows are made through the immersed boundary technique. Particles are tracked by using Lagrangian approach and further coupled with gas phase. Four coal ash particles are considered 6.2, 20, 80, and 200 ,m. In the end, the erosion of the duct walls and that of the tubes near side walls has been well predicted and characterized. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Simulation of an aperture in the thick metallic screen that gives high intensity and small spot size using surface plasmon polaritonJOURNAL OF MICROSCOPY, Issue 3 2003K. Tanaka Summary The optical wave behaviour around a subwavelength aperture in a thick metallic screen is examined through three-dimensional computer simulation. Treating the metallic screen as a dielectric slab with complex-valued permittivity, it is possible to design an aperture that simultaneously provides high intensity and small spot size through the excitation of surface plasmon polaritons on the side walls of the aperture. [source] A model of stomatal conductance to quantify the relationship between leaf transpiration, microclimate and soil water stressPLANT CELL & ENVIRONMENT, Issue 11 2002Q. Gao Abstract A model of stomatal conductance was developed to relate plant transpiration rate to photosynthetic active radiation (PAR), vapour pressure deficit and soil water potential. Parameters of the model include sensitivity of osmotic potential of guard cells to photosynthetic active radiation, elastic modulus of guard cell structure, soil-to-leaf conductance and osmotic potential of guard cells at zero PAR. The model was applied to field observations on three functional types that include 11 species in subtropical southern China. Non-linear statistical regression was used to obtain parameters of the model. The result indicated that the model was capable of predicting stomatal conductance of all the 11 species and three functional types under wide ranges of environmental conditions. Major conclusions included that coniferous trees and shrubs were more tolerant for and resistant to soil water stress than broad-leaf trees due to their lower osmotic potential, lignified guard cell walls, and sunken and suspended guard cell structure under subsidiary epidermal cells. Mid-day depression in transpiration and photosynthesis of pines may be explained by decreased stomatal conductance under a large vapour pressure deficit. Stomatal conductance of pine trees was more strongly affected by vapour pressure deficit than that of other species because of their small soil-to-leaf conductance, which is explainable in terms of xylem tracheids in conifer trees. Tracheids transport water by means of small pit-pairs in their side walls, and are much less efficient than the end-perforated vessel members in broad-leaf xylem systems. These conclusions remain hypothetical until direct measurements of these parameters are available. [source] Double-helix structure in multiwall boron nitride nanotubesACTA CRYSTALLOGRAPHICA SECTION A, Issue 6 2005Ayten Celik-Aktas A new nanotube structural form is reported that resembles a double helix in multiwall boron nitride nanotubes (MW-BNNT) grown by a carbon-free chemical-vapor-deposition process as documented by evidence obtained by transmission electron diffraction and microscopy. The double-helix structure is found in MW-BNNTs exhibiting the same chirality in its different walls. The MW-BNNTs deviate from the structure of ideal nested coaxial cylindrical tubes. Most significantly, bright- and dark-field electron imaging reveals regular zigzag dark and bright spots on the side walls of the nanotubes. The repeating distance between the bright, or dark, spots is related to the chiral angle of the nanotube. Electron diffraction patterns recorded from individual nanotubes show additional diffraction spots belonging to the ,201, zone axes, which are not allowed in a perfectly cylindrical nanotube. These additional diffraction spots become asymmetrical as smaller sections of the nanotube are probed. A series of diffraction patterns recorded along the tube axis showed that the imperfections giving rise to these spots move in a regular fashion around the circumference of the tube. It is shown that all experimental evidence supports the structure model of two helices; one is polygonal in cross section and highly crystalline and the other is circular and less ordered. It is further suggested that the double-helix structure is a result of stronger wall,wall interactions associated with the ionic bonding in boron nitride. [source] Evaluation of several strategies to increase the residence time of Episyrphus balteatus (Diptera, Syrphidae) releases in sweet pepper greenhousesANNALS OF APPLIED BIOLOGY, Issue 3 2008A. Pineda Abstract We have investigated several factors affecting the augmentation of the aphidophagous syrphid Episyrphus balteatus in Mediterranean sweet pepper greenhouses. First, the effectiveness of releases has been assessed by recording the larva and pupa number. The abundance of E. balteatus varied between greenhouses, which was not observed to be a release effect. Second, two experiments were performed to assess the effect of three biological control management strategies on the release residence time. In the first experiment, the greenhouse ventilation was shown to have a significant influence on the adult population residence time, which was higher when the side walls were closed rather than open. The introduction of additional floral resources (sweet alyssum and coriander) did not have a significant effect on the release residence time. In the second experiment, the age of the released adults was assessed, and 2-day-old adults stayed longer in the greenhouse than 7-day-old adults, but the 7-day-old adults had more time to lay eggs. Although syrphids are effective aphid natural enemies, the release methodology of introducing pupae appears not to be effective in Mediterranean greenhouses. In this paper, we propose changing the methodology of releasing E. balteatus. [source] Zum Kontaktverhalten zwischen suspensionsgestützten Ortbetonwänden und dem anstehenden BodenBAUTECHNIK, Issue 11 2007Anna Arwanitaki Dipl.-Ing. Eingangsparameter für analytische und numerische Berechnungen eines Baugrubenverbaus ist der Wandreibungswinkel. Dieser beschreibt die Fähigkeit, wieviel Schubspannungen aus dem Boden an der Grenzfläche Boden,Verbauwand von der Verbauwand bei einer vorgegebenen Normalspannung aufgenommen werden können. Die national gültigen Normen und Empfehlungen geben für Berechnungen im GZ1 einen Wandreibungswinkel von |,| , ,/2 vor. Für den Nachweis der Gebrauchstauglichkeit GZ2 hat sich die Methode der Finiten Elemente etabliert. Mit zunehmender Verfeinerung der Berechnungen stellt sich somit die Frage, ob der Ansatz von |,| , ,/2 noch zutreffend ist. Bei der Herstellung von Schlitzwänden sowie von unverrohrten Bohrpfahlwänden erfolgt der Bodenaushub im Schutze einer Stützflüssigkeit aus Wasser und Bentonit. Nach Erreichen der Schlitzendtiefe wird im Kontraktorbetonverfahren die Stützsuspension von unten nach oben verdrängt. Dabei können Reste der Suspension oder des entstehenden Filterkuchens in der Kontaktfläche Boden,Verbauwand verbleiben und den Wandreibungswinkel beeinflussen. In-situ-Proben des Filterkuchens einer Schlitzwandbaugrube zeigten, dass die Filterkuchenfestsubstanz ein Gemisch aus Bentonit und dem anstehenden Boden ist. Durch die Aushubarbeiten vermischt sich der anstehende Boden mit der Suspension, wobei die feinen Kornfraktionen durch die Fließgrenze der Suspension in Schwebe gehalten werden. Der durch den Filtrationsprozess an der Erdwandung entstehende Filterkuchen kann daher nicht mehr als Schmierschicht aus Bentonit bezeichnet werden, sondern besitzt eine beachtliche Scherfestigkeit. Dieser Beitrag stellt Ergebnisse von Baustellen- und Laboruntersuchungen zur Beschaffenheit des Filterkuchens und zur Ermittlung des Kontaktverhaltens des Boden-Schlitzwand-Systems vor. Skin friction of cast-in-place walls. Analytical and numerical calculations of retaining structures require the wall friction angle as an input parameter. It is specified as the maximal shear strength of the concrete-soil interface due to normal effective load. For the design of diaphragm walls the national engineering standards recommend an angle of wall skin friction of |,| , ,/2. In the framework of present design numerical calculations are performed to determine the deformation behaviour of structures, so that the contact formulation becomes fundamental. Bentonite suspensions are used to support the sides of excavation for diaphragm walls and uncased cast-in-place piles. When concrete is cast by tremie methods the filter cake remains adhering on side walls and becomes part of the concrete-soil interface and influences the characteristics of wall skin friction. In-situ specimens of the filter cake were taken from a diaphragm wall and examinations reveal that the filter cake consists of bentonite and fine soil particles. Due to the excavation process fine particles from the soil are suspended into the supporting fluid due to the liquid limit of the bentonite slurry. Thus, the suspension, in a process of filtration into the surrounding soil, forms a filter cake with a certain shear strength caused by the fine soil particles. This paper presents the results of field and laboratory tests for the investigation of the effective contact behaviour between cast-in-place walls and the surrounding soil. [source] | ||||||||||||||||||||||