Degree Bend Research Articles

Two‐ and Three‐Phase Flow Through a 90 Degree Bend

AbstractData are presented for two‐phase air/water pipeflow and three‐phase air/oil/water in a 0.026 m i.d. pipe and elbow bend (R/d = 0.654) for vertical to horizontal flow. The two‐phase results were shown to be dependant on the flow regimes present in the system. The elbow bend acted either to smooth the transition from vertical to horizontal flow when the liquid rate was below the bubble rise velocity in the inlet leg (when negative bend pressure losses were achieved), or to generate droplets and increase the bend pressure drop substantially at higher fluid rates.Three‐phase data also showed significant but not such dramatic differences, depending on the combined liquid rate being above or below the bubble rise velocity in the inlet leg. Again the variation of pressure drop for the system could be qualitatively explained by the observed flow regimes.For both two‐phase and three‐phase systems, the observed bend pressure drop could be correlated using a Lockhart‐Martinelli approach based on the single‐phase flow data for the bend.

Three-dimensional analysis of a hybrid photonic crystal-conventional waveguide 90 degree bend.

We present a three-dimensional (3D) analysis of a hybrid photonic crystal-conventional waveguide 90 degree bend proposed previously [Opt. Express 10, 1334 (2002)] as an ultracompact component for large-scale planar lightwave circuit integration. Both rigorous 3D finite-difference time-domain modeling and a simple perfect mirror model analysis were carried out for different Si post heights in the photonic crystal region. Results show that the bend efficiency increases rapidly with Si post height. For a post height of 6.5 microm, this structure yields a bend efficiency of 97.3% at a wavelength of 1.55 microm for 90 degree bends in 2 microm x 2 microm square channel conventional waveguides with a refractive index contrast of 3.55%, which is very close to the bend efficiency of 98.2% for the corresponding two-dimensional problem. Our 3D analysis permits the examination of issues such as out-of-plane scattering loss and the effects of finite Si post height that are not considered in two dimensions.

Effect of Curvature Ratio on Thermal Mixing Characteristics in a T-Junction Area Which Has a 90-Degree Bend in the Upstream Area

Thermal mixing characteristics in a T-junction area which has different type of 90-degree bend in the upstream area are evaluated in order to clarify the effect of the curvature ratio on the fluid mixing and wall-temperature fluctuation. The fluid mixing states at some velocity ratios are visualized with PIV measuring system first and its characteristics are associated with the temperature fluctuation data in the vicinity of wall measured with thin thermocouples. It is clarified that the curvature ratio of 90-degree bend strongly affects the thermofluid mixing state, and different effects on the temperature fluctuation depending on the curvature ratio are confirmed. Especially, there is a possibility that the low curvature ratio of bend, in which a separation occurs, is useful for the control of the wall temperature fluctuation due to the strong turbulent mixing effect

Unsteady Decay Behaviour of Secondary Flow Generated in 90-Degee Bends

Decay processes of secondary flow generated in 90-degree bends are visualized by using a PIV measurement system. The main parameters are a Re number and a curvature ratio of the bend, and three kinds of the 90-degree bend are prepared. It is confirmed that symmetrical and apparent secondary flow, which is a twin-vortex, is formed in a cross section of the pipe shortly after the bend outlet for each curvature ratio where the flow field is analyzed in the time average. However, it is clarified that this secondary flow unsteadily and intensely fluctuates in the cross section regardless of the curvature ratio. Especially, where the curvature ratio is the lowest of 1.0, it is confirmed that the flow field is even more complex and its flow pattern rapidly disappears in more downstream area by the interaction between the secondary flow formed by a centrifugal force and newly generated separation vortex.

Fluid Flow through 90 Degree Bends

AbstractPressure drop measurement and prediction in curved pipes and elbow bends is reviewed for both laminar and turbulent single‐phase fluid flow. For curved pipe under laminar flow, the pressure loss can be predicted both theoretically and using empirical relations. The transitional Reynolds number can be predicted from an empirical relation. Turbulent flow in curved pipes can only be theoretically predicted for large bends but there are a large number of empirical relations that have proved to be accurate. Elbow bends have proven to be difficult to both measure and represent the pressure loss. Methods of overcoming such problems are outlined. There was no reliable method of theoretically predicting pressure drop in elbow bends. Experimental measurements showed considerable scatter unless care was taken to eliminate extraneous effects. Reliable data are highlighted and an empirical method is proposed for calculation of pressure drop in elbow bends.

Bending Properties of Nanocrystalline Ni-18 at% W Alloy Produced by Electrodeposition

A nanocrystalline Ni-18 at% W alloy with the grain size of 5.3 nm was produced by an electrodeposition method and its bending properties were investigated in the temperature range between room temperature and 673 K. At room temperature and 373 K, the nanocrystalline Ni-W alloy could be bent to an angle of 180 degrees without fracturing. At 423 K and above, the alloy fractured before reaching 180 degree during bending. Significant springback behavior was observed after 180 degree bending at room temperature under the condition that a compressive load of 9 N was applied during bending. As the compressive load was increased from 30 N to 135 N, the magnitude of springback decreased. Thus, the nanocrystalline Ni-W alloy exhibited excellent bendability at room temperature.

Broadband photonic crystal waveguide 60� bend obtained utilizing topology optimization

Topology optimization has been used to design a 60 degrees bend in a single-mode planar photonic crystal waveguide. The design has been realized in a silicon-on-insulator material and we demonstrate a record-breaking 200-nm transmission bandwidth with an average bend loss of 0.43+/-0.27 dB for the TE polarization. The experimental results agree well with 3D finite-difference-time-domain simulations.

412 異径双ロールキャスターによるAl合金板の作製(OS 溶融加工(1))

Purpose: of this paper is to clear the property and ability of an unequal diameter twin roll caster to cast commercial size strip. Therefore, 400mm-width strip was cast as first step. Surface-condition, microstructure and mechanical property of the strip was investigated. Design/methodology/approach: Method used in the present study was an unequal diameter twin roll caster. This method was devised to realize easy operation of the twin roll casting and increase of casting speed. Findings: are that 400-width-strip of 3084, 5182 and 6022 could be cast at speed of 20 m/min. This strip was about 4 mm-thick. There were some defects on the surface. As cast strip could be cold-rolled down to sheet of 1 mm-thick. 180 degrees bending test was operated on the 6022 sheet after T4 heat treatment. Crack did not occurred at the outer surface when strip was bent at width-direction. Research limitations/implications: is that the quantity of the melt was 21kg and investigation of the properties was not enough for practical use. The larger weight of melt must be cast for production. Practical implications: are as below. The 400mm-width strip can be cast easily by the unequal diameter twin roll caster. This caster can be adapted to 3083, 5182 and 6022. Originality/value: as below. The economy sheet with 400mm width can be produced by the unequal diameter twin roll caster. 3083, 5182 and 6022 can be cast at the speed of 20m/min. The thickness of the strip was about 4mm.

Optimizing bending efficiency of self-collimated beams in non-channel planar photonic crystal waveguides

In this paper, we propose a device to bend light in non-channel planar photonic crystal (PhC) waveguides using the self-collimation phenomenon. The mode distribution in a non-channel planar PhC waveguide is investigated in detail in order to help understand the proposed bending mechanism. Three-dimensional finite-difference time-domain simulations show an over 80% bending efficiency for a 90 degree bend. As the first proposal for bending light in a non-channel planar PhC waveguide, the presented device enables the application of routing in non-channel planar PhC waveguides.

Drag Reduction in a 90-degree Bend Pipe with a Half-Trip.

In order to reduce pressure loss and asymmetry, a flow control device was applied to the complex flow field in a 90-degree bend pipe : a trip wire was attached on the inside wall of the curve at appropriate upstream position to the 90-degree bend. The trip device spans half circumferential length, that is, it is called as in the present experiment. To see ability of the device to control the complex flow, pressure loss, axial mean velocity profile and secondary current were measured for Reynolds number range Re=50000-82000. The experiment was made with relatively small rate of curvature to pipe radius 2R/D=1.43. Wall static pressure measurements certainly show that the half-trip is effective to reduce pressure loss as well as asymmetry of the axial mean velocity at exit of the bend pipe. The maximum reduction rates of pressure loss coefficient is 23% for trip device height k=3.0mm and 5.0mm. A possible mechanism is discussed with available experimental evidences of axial velocity, secondary velocity vectors and oil film pattern observations.

Hybrid integration of conventional waveguide and photonic crystal structures

We propose the hybrid integration of conventional index-guided waveguides (CWGs) and photonic crystal (PhC) regions of very limited spatial extent as a promising path toward large-scale planar lightwave circuit (PLC) integration. In CWG/PhC structures the PhC regions do not perform the function of waveguiding, but instead augment the CWGs to permit a drastic reduction in the size of photonic components. For single mode waveguides with a refractive index contrast of only 2.3%, simulation results show a 90 degree bend with 98.7% efficiency, a compact beamsplitter with 99.4% total efficiency, and a planar Mach-Zender interferometer (MZI) with 97.8% efficiency. The MZI occupies an area of only 18microm m x 18 microm.

Effect of Close-Coupled Bends in Pneumatic Conveying

Pressure drop in a close-coupled double bend in pneumatic conveying of fly ash is studied. Tests are carried out with a 6.35 cm (2.5 in) diameter 169.8 m (557 ft) long pipeline with various combinations of airflow, ash flow, phase density, and conveying velocity. The pressure drop across two close-coupled 90-degree bends is compared to the pressure drop in an isolated single 90-degree bend. Six ash samples of different physical and chemical compositions are used in the tests. Resulting bend pressure drops are correlated to the corresponding phase density and superficial air velocity at the bend inlet. The correlation pattern represented by the relationship {\\Delta P_{solids} \\over {SLR}} = Y1 \\cdot V^{Y2} is established and found to vary with ash properties. For both single and close-coupled double bends and operating test conditions with \\Delta {\\rm P}_{\\rm solids} / {\\rm SLR} 0.15 at the bend entry, 86% of the measured test points fall within the range of - 20% of the \\Delta {\\rm P}_{\\rm solids} / SLR calculated point. Below this threshold, the test results show that the pressure drops due to solids flow through a close-coupled double bend and single bends are often indistinguishable. Consequently, the loss through a close-coupled double bend cannot be considered as the cumulative effect of two isolated single bends.

Crystal structure of the intein homing endonuclease PI-SceI bound to its recognition sequence.

The first X-ray structures of an intein-DNA complex, that of the two-domain homing endonuclease PI-SceI bound to its 36-base pair DNA substrate, have been determined in the presence and absence of Ca(2+). The DNA shows an asymmetric bending pattern, with a major 50 degree bend in the endonuclease domain and a minor 22 degree bend in the splicing domain region. Distortions of the DNA bound to the endonuclease domain cause the insertion of the two cleavage sites in the catalytic center. DNA binding induces changes in the protein conformation. The two overlapping non-identical active sites in the endonucleolytic center contain two Ca(+2) ions that coordinate to the catalytic Asp residues. Structure analysis indicates that the top strand may be cleaved first.

Threonine 79 Is a Hinge Residue That Governs the Fidelity of DNA Polymerase β by Helping to Position the DNA within the Active Site

DNA polymerase beta (pol beta) is an ideal system for studying the role of its different amino acid residues in the fidelity of DNA synthesis. In this study, the T79S variant of pol beta was identified using an in vivo genetic screen. T79S is located in the N-terminal 8-kDa domain of pol beta and has no contact with either the DNA template or the incoming dNTP substrate. The T79S protein produced 8-fold more multiple mutations in the herpes simplex virus type 1-thymidine kinase assay than wild-type pol beta. Surprisingly, T79S is a misincorporation mutator only when using a 3'-recessed primer-template. In the presence of a single nucleotide-gapped DNA substrate, T79S displays an antimutator phenotype when catalyzing DNA synthesis opposite template C and has similar fidelity as wild type opposite templates A, G, or T. Threonine 79 is located directly between two helix-hairpin-helix motifs located within the 8-kDa and thumb domains of pol beta. As the pol beta enzyme closes into its active form, the helix-hairpin-helix motifs appear to assist in the production and stabilization of a 90 degrees bend of the DNA. The function of the bent DNA is to present the templating base to the incoming nucleotide substrate. We propose that Thr-79 is part of a hydrogen bonding network within the helix-hairpin-helix motifs that is important for positioning the DNA within the active site. We suggest that alteration of Thr-79 to Ser disrupts this hydrogen bonding network and results in an enzyme that is unable to bend the DNA into the proper geometry for accurate DNA synthesis.

Crystal structure of the Lactococcus lactis formamidopyrimidine-DNA glycosylase bound to an abasic site analogue-containing DNA.

The formamidopyrimidine-DNA glycosylase (Fpg, MutM) is a bifunctional base excision repair enzyme (DNA glycosylase/AP lyase) that removes a wide range of oxidized purines, such as 8-oxoguanine and imidazole ring-opened purines, from oxidatively damaged DNA. The structure of a non-covalent complex between the Lactoccocus lactis Fpg and a 1,3-propanediol (Pr) abasic site analogue-containing DNA has been solved. Through an asymmetric interaction along the damaged strand and the intercalation of the triad (M75/R109/F111), Fpg pushes out the Pr site from the DNA double helix, recognizing the cytosine opposite the lesion and inducing a 60 degrees bend of the DNA. The specific recognition of this cytosine provides some structural basis for understanding the divergence between Fpg and its structural homologue endo nuclease VIII towards their substrate specificities. In addition, the modelling of the 8-oxoguanine residue allows us to define an enzyme pocket that may accommodate the extrahelical oxidized base.

Interaction between a DNA oligonucleotide and a dinuclear iron(II) supramolecular cylinder; an NMR and molecular dynamics study.

A tetracationic supramolecular cylinder, [Fe(2)L(3)](4+) (L=C(25)H(20)N(4)), with a triple-helical architecture, is just the right size to fit into the major groove of DNA but too big to fit into the minor groove. A detailed NMR spectroscopic analysis supported by molecular dynamics (MD) calculations shows unambiguously the close fit between the cylinder and a duplex oligonucleotide, [d(GACGGCCGTC)(2)]. Furthermore, only the left-handed enantiomer of the cylinder seems to fit the groove geometry. With both free and complexed species of [Fe(2)L(3)](4+) and DNA in solution, the NMR spectra are too complicated for a detailed structure determination. Based on differences in chemical shifts and extensive MD calculations, a realistic qualitative picture of the DNA-cylinder adduct is presented. Several sets of chemical shifts assigned to the protons of the three ligand strands in the cylinder indicate that the iron complex situated in the major groove exhibits restricted rotation on the NMR timescale around the cylindrical axis. The NMR NOE data support a model where the cylinder undergoes both a translational and rotational oscillation in the major groove. The results of an NOE restrained MD calculation indicates that the cylinder induces a 40 degrees bend of the double helix, in accordance with linear dichroism measurements. Other distinct features to be noticed are the very low value of the helical twist (16 degrees) induced at the G(4)C(5) step.

A design for a wide-aperture 90° bending magnet for heavy-ion cancer therapy

A description of a wide-aperture 90-degree bending magnet is presented. This magnet was designed as a part of a beam delivery system of the heavy-ion therapy facility developed in GSI, Darmstadt, Germany. A concept of the almost window frame magnet with the air slots in a yoke ensures a homogeneous field (/spl Delta/B/B</spl plusmn/0.01%) over the area of 200/spl times/200 mm/sup 2/ in the central part of the magnet in a wide range of the flux density variation. The expected integral field homogeneity of the magnet is better than /spl plusmn/0.02% and corresponds to the required beam positioning accuracy of /spl plusmn/1 mm. The dynamic behavior of the magnet is investigated. The main time constant of the magnet is calculated.

摩擦圧接の接合メカニズムに関する研究 ３ 低入熱摩擦圧接における摩擦時間，摩擦トルクと継手特性の関係

In the previous reports 1 and 2, the authors have clarified the joining mechanism in the first phase of friction stage during friction welding process. The present paper describes the relationship between the friction time, friction torque, and joint properties of friction welding for a low heat input friction welding method. The materials joined were mild steels (same materials), and a brake type friction welding machine was used for joining. In actual experiment, i.e., the low heat input friction welding method (LHI method), the electromagnetic clutch was used in order to exclude braking deformation at rotation stopping. The following are concluded. (1) The joints obtained only in the first stage (up to initial peak torque) had 100% joint efficiency and 90 degrees bend ductility with no crack. It was determined that friction welded joints with 100% joint efficiency and good bend ductility could be obtained by using only the friction stage up to initial peak torque and without the need for the forging (upsetting) stage. (2) The fracture occurred at the substrates (not at the welded interface) in welded joints when friction torque was close to initial peak torque. It was clarified that those joints has less width of heat affected zone and less width of hardening. (3) It was clarified that the friction welded joints without using the forging stage (the friction welded joints by using the LHI method) have same mechanical properties as those welded by the conventional friction welding process including that stage. The LHI method has more advantages, i.e., less burn-off and less burr.

Polarization dependence in Ti-diffused LiNbO3 directional couplers.

The effect of design and fabrication parameters on the dependence on polarization of the splitting ratio in directional couplers produced by Ti diffusion in LiNbO3 has been investigated experimentally at a wavelength of 1.54 microm. The parametric study was carried out at a diffusion temperature of 1025 degrees C, which was found to suppress outdiffusion effects. The directional couplers were produced by use of various combinations of waveguide separation, Ti film thickness, and diffusion time. Of particular interest was the identification of parameter sets for which the sum of TE and TM splitting ratios equals unity, as required for electro-optic and acousto-optic tunable filter designs with relaxed beam-splitter requirements. Directional couplers that closely match this criterion were obtained by diffusion of 3.5-mm-long, 7-microm-wide Ti strips separated by 11 microm for 11 h. It was found that a bending angle of 0.6 degrees for input and output waveguides produces lower transmission loss for both polarizations than a 1.0 degree bend angle (>1-dB loss reduction).

Ultrasonic wedges for elastic wave bending and splitting without requiring a full band gap.

We present a novel twinned-square periodic structure for ultrasonic wave bending and splitting that does not require the existence of a complete band gap and plays the role of an ultrasonic wedge. The device allows 45 degrees bending of waves and by adequately switching the twinned structure to an ultrasonic crystal 90 degrees bending is achieved. An extreme refraction law at the grain boundaries is experimentally observed.