Spiral Section Research Articles

Free vibration analysis of cylindrical panels with spiral cross section

In this paper, free vibration of open noncircular cylinders with spiral cross section are studied under arbitrary boundary conditions. For deriving the strain energy function, Kirchhoff-Love hypotheses are employed. To obtain the solutions, Rayleigh-Ritz technique is implemented by selecting Chebyshev orthogonal polynomials of first kind as admissible displacement functions in three directions. Convergence of the proposed formulation is verified for spiral cylindrical panel and the results are compared with those of ABAQUS. Parametric study is undertaken to highlight the effect of inner radius, separation distance, subtended angle, thickness, and length of the spiral cylinders on the free vibration characteristics. Results obtained in this research are the first step toward modeling spiral cylinders and can be used for comparison in future studies. Finally, the design strategy for the spiral cylinders with specific vibration characteristics is presented. The results imply that spiral cylinder with specific vibration characteristics can be designed using equivalent open circular cylinder.

On the detonation propagation behavior in hydrogen-oxygen mixture under the effect of spiral obstacles

Detonation propagation velocity behavior and cellular structure of stoichiometric hydrogen-oxygen mixture in spiral obstacles with four roughness (ξ = 0.133, 0.231, 0.4, 0.625) are systematically examined, at the conditions outside-, near- and within the propagation limits. The experimental results indicate that, at p0 = 10 kPa (outside the limits), spirals with roughness smaller than 0.4 facilitate the initiation of detonation, but ξ = 0.625 spiral causes the detonation quench earlier than that in smooth tube without spiral, and suggests it has prohibiting effect on the detonation propagation. At p0 = 12 kPa (near the detonation limits), spirals with ξ = 0.133 and 0.231 extend the detonation limits and therefore they have the facilitating effect on the detonation propagation, but this positive effect is not obvious in the spiral with larger roughness (i.e., ξ = 0.4 and 0.625). As the initial pressure is higher than 15 kPa, under such condition detonations are well within the limits, the dual effects of promoting and prohibiting of the spiral on the detonation propagation are more obvious, which are confirmed by the cellular structures obtained from smoked foil. The ZND induction zone length (ΔI) analysis confirms ΔI is shorter at higher initial pressure, under this condition detonation is more sensitive and easier to survive from failure as it enters into the spiral section.

Surgical approach to cochlear implantation in patients with cochlear ossification

Cochlear spiral canal ossification is one of the most critical issues in cochlear implantation. The article suggests a method of atraumatic drilling of the ossified spiral canal section and demonstrates the results of 45 surgical interventions performed according to this method. The experimental part of the study provides the inner ear structures syntopy presenting the results of topographic anatomical measurements which justify the application of the suggested method.

Structure of ordered coaxial and scroll nanotubes: general approach.

The explicit formulas for atomic coordinates of multiwalled coaxial and cylindrical scroll nanotubes with ordered structure are developed on the basis of a common oblique lattice. According to this approach, a nanotube is formed by transfer of its bulk analogue structure onto a cylindrical surface (with a circular or spiral cross section) and the chirality indexes of the tube are expressed in the number of unit cells. The monoclinic polytypic modifications of ordered coaxial and scroll nanotubes are also discussed and geometrical conditions of their formation are analysed. It is shown that tube radii of ordered multiwalled coaxial nanotubes are multiples of the layer thickness, and the initial turn radius of the orthogonal scroll nanotube is a multiple of the same parameter or its half.

The process analysis of seeding-grain selection and its effect on stray grain and orientation control

A combined technique denoted as seeding-grain selection (SGS) was designed for fabricating single crystal turbine blades. The microstructural evaluation during SGS process was metallographically analyzed in both starter section and spiral section of this technique. Four zones with distinct dendritic morphologies were identified in seed melt back region. After epitaxial propagating from melted seed and branching through the spiral passage, the lined-up dendritic pattern was observed at the outlet of the passage. The effectiveness of the technique on stray grain and orientation control was also assessed by Electron Back-Scattering Diffraction (EDSD) technique. The results indicated that the technique can control stray grain with no detrimental effect on crystal orientation.

Abnormal Calcium Metabolism in the Living Human Inner Ear Disorders

Aims1) What kinds of metabolic abnormalities were caused by the inner ear disorders such as presbycusis, sudden deafness, tinnitus, BPPV, and Meniere's disease? 2) To investigate an imaging method of abnormal calcium oxide concentrated in the inner ear used by a conventional spiral CT.Subjects6 normal ears of adolescence, 6 normal ears of elderlies, 3 ears of sudden deafness, 3 ears of BPPV, 6 ears of tinnitus, and 3 ears of Meniere's disease. Every cases were undergone follow‐up exams after medical treatments.Methods3D virtual histology of the inner ear used by the volume rendering technique was reconstructed by a conventional temporal HR‐CT. For the imaging study of calcium oxide in the desiccant, quantitative analysis based on 3D volume rendering technique used by a spiral thin section CT.imageResults6 normal adolescent ears showed no image of calcium oxide. Meniere's disease, tinnitus originating from the ear, sudden deafness, and BPPV and aging changes revealed abnormal deposited of calcium oxide at the cochlea and saccule. For tinnitus originating from the ear, the calcium oxide deposited in the cochlea. Otherwise, tinnitus from brain did not deposit in the inner ear. Aging change showed calcium oxide deposited in the cochlea and vestibule in correlation with their aging.imageConclusionAll inner ear disorders and aging changes showed abnormal images of calcium oxide like figure 2. But, tinnitus originating from brain showed no calcium oxide deposited in the cochlea. These facts implicated that inner ear disorders and aging change were caused by unbalance metabolism between calcium ion and oxygen. But we cannot deny the existence of calcium peroxide (CaO2) that was produced by free radical action.

Dual-Band Operation of Relativistic BWO With Linearly Polarized Gaussian Output

We demonstrate the dual-band operation of a relativistic backward wave oscillator (RBWO) whose output is a linearly polarized TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> -mode. The RBWO consists of two cylindrical sections with sinusoidal corrugations where the downstream section is axisymmetric and the upstream section has combined left- and right-single-fold spiral corrugations. We show that generation of 10 GHz is realized when the axisymmetric section operates as a BWO with the operating TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> -mode and the combined spiral section operates as a Bragg reflector that converts the backward TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> -mode to a linearly polarized forward TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> -mode. For the same electron beam parameters, generation of 7 GHz is realized when the combined spiral section operates as a BWO with the operating TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> -mode. We also present the possibility to change the duration of generation at each frequency within a microwave pulse by changing the electron beam current. In addition, one can change the output frequency by changing the values of the guide magnetic field near the region of cyclotron absorption.

Detonation engine fed by acetylene–oxygen mixture

The advantages of a constant volume combustion cycle as compared to constant pressure combustion in terms of thermodynamic efficiency has focused the search for advanced propulsion on detonation engines. Detonation of acetylene mixed with oxygen in various proportions is studied using mathematical modeling. Simplified kinetics of acetylene burning includes 11 reactions with 9 components. Deflagration to detonation transition (DDT) is obtained in a cylindrical tube with a section of obstacles modeling a Shchelkin spiral; the DDT takes place in this section for a wide range of initial mixture compositions. A modified ka-omega turbulence model is used to simulate flame acceleration in the Shchelkin spiral section of the system. The results of numerical simulations were compared with experiments, which had been performed in the same size detonation chamber and turbulent spiral ring section, and with theoretical data on the Chapman–Jouguet detonation parameters.

Shock tube design for high intensity blast waves for laboratory testing of armor and combat materiel

Shock tubes create simulated blast waves which can be directed and measured to study blast wave effects under laboratory conditions. It is desirable to increase available peak pressure from ~1 MPa to ~5 MPa to simulate closer blast sources and facilitate development and testing of personal and vehicle armors. Three methods were investigated to increase peak simulated blast pressure produced by an oxy-acetylene driven shock tube while maintaining suitability for laboratory studies. The first method is the addition of a Shchelkin spiral priming section which works by increasing the turbulent flow of the deflagration wave, thus increasing its speed and pressure. This approach increased the average peak pressure from 1.17 MPa to 5.33 MPa while maintaining a relevant pressure-time curve (Friedlander waveform). The second method is a bottleneck between the driving and driven sections. Coupling a 79 mm diameter driving section to a 53 mm driven section increased the peak pressure from 1.17 MPa to 2.25 MPa. Using a 103 mm driving section increased peak pressure to 2.64 MPa. The third method, adding solid fuel to the driving section with the oxy-acetylene, resulted in a peak pressure increase to 1.70 MPa.

Air Suspension System Model Coupled With Leveling and Differential Pressure Valves for Railroad Vehicle Dynamics Simulation

In this investigation, a nonlinear air suspension system model that accounts for the coupling between air springs, leveling valves, and differential pressure valves is developed and integrated into general-purpose multibody dynamics computer algorithms. It is demonstrated that the proposed model can capture highly nonlinear air suspension characteristics resulting from the coupling with leveling and differential pressure valves, and good agreements are obtained between the numerical and on-track test results. Furthermore, the effect of flow characteristics of leveling valves on the wheel load unbalance on spiral curve sections is discussed. The numerical results obtained by the proposed model clearly indicate the importance of modeling the nonlinear flow characteristics of the leveling and differential pressure valves for assessing the vehicle safety in low speed operations on a small radius curved track.

PLANAR RECONFIGURABLE MULTIFUNCTIONAL ANTENNA FOR WLAN/WIMAX/UWB/PCSDCS/UMTS APPLICATIONS

A wideband slotted multifunctional reconflgurable an- tenna is proposed for WLAN/WiMAX/UWB/PCS-DCS/UMTS appli- cations. The proposed antenna consists of monopole and spiral sections and microstrip feeding. A microstrip patch on FR4 substrate provides wideband return loss for each application. Total area of the antenna is 34£45mm 2 that satisfles all the requirements for difierent applications in a low proflle structure. Reconflgurable design is used in this antenna using RF MEMS switches. The proposed antenna has a nearly omni- directional radiation patterns (doughnut shape) in difierent frequency bands. The notch is embedded in the ground plane to improve the impedance matching, and the dimensions of this notch are optimized. Moreover, the variation of group delay is about §2ns in UWB applica- tion. Also a prototype of the proposed antenna is fabricated, and the results are compared with those obtained from simulations. Measured return losses are in good agreement with simulated ones. The proposed antenna has the advantages of multifunctional operation, low proflle, low cost and omnidirectional pattern.

Single-mode quantum cascade lasers employing a candy-cane shaped monolithic coupled cavity

We demonstrate single-mode quantum cascade lasers emitting at ∼4.5 μm by employing a monolithic “candy-cane” shaped coupled-cavity consisting of a straight section connecting at one end to a spiral section. The fabrication process is identical to those for simple Fabry-Perot-type ridge lasers. Continuously tunable single-mode emission across ∼8 cm−1 with side mode suppression ratio up to ∼25 dB and a single-mode operating current range of more than 70% above the threshold current is achieved when the lasers are operated in pulsed-mode from 80 K to 155 K.

Anonymous Function Method and its Application in Screw Pump’s Design and Processing

Matlab anonymous function method combining graph with analytical method was proposed in this paper, which was based on the low solving efficiency and low precision of trigonometry transcendental equation for shape line design and sectional profile calculation of screw pump rotor. Parameters of anonymous function can be nested within each other to solve enveloping conditional formula of shape design or intersecting line of sectional profile design for screw pump, the process of which only took several seconds with high precision of 10E-08mm. What’s more, this method could also be adopted in the forming tool design with spiral cross section, which could largely improve design efficiency and calculation precision.

Study of the effect of the spiral geometry on wheel/rail contact forces

Spiral sections are used in the construction of railroad tracks in order to achieve a smooth change in the curvature. In order to satisfy the kinematic conditions at the position, velocity, and acceleration levels in railroad vehicle dynamics computational algorithms based on the constraint contact formulations; third-order derivatives of the wheel/rail contact constraint functions with respect to the wheel and rail geometric surface parameters must be evaluated. Discontinuities in these higher derivatives can produce jumps in the wheel/rail contact forces at the spiral entries and exits. This paper develops a simple procedure that can be applied online to ensure that the curvature and its derivative of the rail space curve are continuous at the spiral entries and exits. Because continuity of the space curve geometric variables does not ensure continuity of these variables on the rail surface, the effect of the proposed procedure on the contact forces is examined. The constraint and elastic wheel/rail contact formulations are first reviewed in order to show the degree of continuity required and the basic kinematic conditions used to search online for the wheel/rail contact points. The rigid track geometry is described using the absolute nodal coordinate formulation (ANCF), which employs a geometric description that ensures the continuity of the position and gradient vectors at the track nodes. In order to ensure the continuity of the curvature vector and its derivative at the intersection of the spirals with the tangent and curve segments, a set of linear conditions are developed and solved online, allowing for implicit elimination of track nodal variables. These conditions are not considered as kinematic constraints imposed on the system motion since they are mainly used to improve the rigid track geometric description and do not involve the system generalized coordinates or their time derivatives. The procedure described in this investigation does not require making changes in the description of the track geometry and does not require the use of higher order derivatives of the track node angles in order to achieve the desired degree of continuity. Because higher degree of continuity achieved for the rail space curve does not ensure a similar degree of continuity on the surface where the wheel/rail contact occurs; the effect of the change of the degree of continuity of the space curve at the spiral entries and exits on the rail surface geometry is also discussed in this paper. The results presented in this study show that the proposed procedure can lead to improvement in the wheel/rail contact force results in some simulation scenarios. The results, obtained using the proposed procedure, are compared with the results obtained using local mesh refinements.

A BURROW CAST WITH LYSTROSAURUS SKELETAL REMAINS FROM THE LOWER TRIASSIC OF SOUTH AFRICA

Abstract We report on a large burrow cast with skeletal contents from Lower Triassic strata of the Palingkloof Member of the Balfour Formation, which forms the lowermost portion of the Lystrosaurus Assemblage Zone (LAZ) of South Africa. The burrow cast is similar to large burrow casts previously described from the LAZ that were identified as large-scale Scoyenia domichnia. It is the first large burrow cast from the LAZ found to contain diagnostic fossil bone. The burrow cast is a relatively straight, subhorizontal (inclined ∼12°), dorsoventrally compressed tube consisting of an entry ramp and living chamber; the entrance to the burrow is not preserved and there is no evidence that the ramp formed a spiral section. The skeletal material comprises a single, partial, disarticulated skeleton of a juvenile animal that can be assigned with confidence to the dicynodont genus Lystrosaurus. Whereas similar large-diameter burrow casts from strata slightly higher in the LAZ have been attributed to Lystrosaurus, we p...

Accurate Representation of the Rail Geometry for Multibody System Applications

The objective of this study is to examine the geometric description of the spiral sections of railway track systems, in order to correctly define the relationship between the geometry of the right and left rails. The geometry of the space curves that define the rails are expressed in terms of the geometry of the space curve that defines the track center curve. Industry inputs such as the horizontal curvature, grade, and superelevation are used to define the track centerline space curve in terms of Euler angles. The analysis presented in this study shows that, in the general case of a spiral, the profile frames of the right and left rails that have zero yaw angles with respect to the track frame have different orientations. As a consequence, the longitudinal tangential creep forces acting on the right and left wheels, in the case of zero yaw angle, are not in the same direction. Nonetheless, the orientation difference between the profile frames of the right and left rails can be defined in terms of a single pitch angle. In the case of small bank angle that defines the superelevation of the track, one can show that this angle directly contributes to the track elevation. The results obtained in this study also show that the right and left rail longitudinal tangents can be parallel only in the case of a constant horizontal curvature. Since the spiral is used to connect track segments with different curvatures, the horizontal curvature cannot be assumed constant, and as a consequence, the right and left rail longitudinal tangents cannot be considered parallel in the spiral region. Numerical examples that demonstrate the effect of the errors that result from the assumption that the right and left rails in the spiral sections have the same geometry are presented. The numerical results obtained show that these errors can have a significant effect on the quality of the predicted creep contact forces.

Women who experienced repeated IVF/ICSI implantation failures show a relative excess of soluble VEGF-R1 before conception

OBJECTIVE: To document simultaneously the microvessels density through a local vascular mapping of the endometrium in the luteal phase and to confront data with the documentation of VEGF and its receptor both at protein and mRNA level among patients which failed to implant compared to fertile ones. Local angiogenesis occurring in the middle luteal phase appears as essential to prepare the endometrium to uterine receptivity.DESIGN: Analytic study, European Network of researchMATERIALS AND METHODS: 38 women participated to this protocol, 13 were fertile control women and 25 were women with repeated and unexplained failures of in vitro fertilization (IVF) attempts. Three-dimensional ultrasound with power angiography was performed to record the sub-endometrial vascular flow index (Sub-VFI) before an endometrial biopsy at day 21-23 of a monitored natural cycle. Datation, semi-quantitative evaluation of spiral arteries section, immunostaining of VEGF, VEGF-R1 and R-2 and quantitative Real time PCR for mRNA expression VEGF-A, VEGF-R1, VEGF-R2 and sVEGF-R1 were performedRESULTS: The Sub-VFI was significantly lower in case of implantation failures. Quantification of spiral arteries sections confirmed the ultrasonographic vascular imaging data. For VEGF, IF patient showed a stronger staining for VEGF and VEGF-R1 than observed in control group and a slightly lower VEGF-R2 immunostaining. The mRNA levels for VEGF, VEGFR-1 and VEGFR-2 were significantly lower in the IF group and the ratio sVEGFR-1/VEGFR-1 significantly higher in context of implantation failure. The Sub-endometrial VFI did not correlate with the mRNA expressions of either VEGF and/or its receptors VEGF-R1 and -2.CONCLUSIONS: The endometrial VEGF system is dysregulated before conception in patients with history of implantation failure and show a preconceptional relative excess of the mRNA expression of sVEGF-R1. OBJECTIVE: To document simultaneously the microvessels density through a local vascular mapping of the endometrium in the luteal phase and to confront data with the documentation of VEGF and its receptor both at protein and mRNA level among patients which failed to implant compared to fertile ones. Local angiogenesis occurring in the middle luteal phase appears as essential to prepare the endometrium to uterine receptivity. DESIGN: Analytic study, European Network of research MATERIALS AND METHODS: 38 women participated to this protocol, 13 were fertile control women and 25 were women with repeated and unexplained failures of in vitro fertilization (IVF) attempts. Three-dimensional ultrasound with power angiography was performed to record the sub-endometrial vascular flow index (Sub-VFI) before an endometrial biopsy at day 21-23 of a monitored natural cycle. Datation, semi-quantitative evaluation of spiral arteries section, immunostaining of VEGF, VEGF-R1 and R-2 and quantitative Real time PCR for mRNA expression VEGF-A, VEGF-R1, VEGF-R2 and sVEGF-R1 were performed RESULTS: The Sub-VFI was significantly lower in case of implantation failures. Quantification of spiral arteries sections confirmed the ultrasonographic vascular imaging data. For VEGF, IF patient showed a stronger staining for VEGF and VEGF-R1 than observed in control group and a slightly lower VEGF-R2 immunostaining. The mRNA levels for VEGF, VEGFR-1 and VEGFR-2 were significantly lower in the IF group and the ratio sVEGFR-1/VEGFR-1 significantly higher in context of implantation failure. The Sub-endometrial VFI did not correlate with the mRNA expressions of either VEGF and/or its receptors VEGF-R1 and -2. CONCLUSIONS: The endometrial VEGF system is dysregulated before conception in patients with history of implantation failure and show a preconceptional relative excess of the mRNA expression of sVEGF-R1.

On the Rapid Collapse and Evolution of Molecular Clouds

Stars generally form faster than the ambipolar diffusion time, suggesting that several processes short-circuit the delay and promote a rapid collapse. These processes are considered here, including turbulence compression in the outer parts of giant molecular cloud (GMC) cores and GMC envelopes, GMC core formation in an initially supercritical state, and compression-induced triggering in dispersing GMC envelopes. The classical issues related to star formation timescales are addressed: high molecular fractions, low efficiencies, long consumption times for CO and HCN, rapid GMC core disruption and the lack of a stable core, long absolute but short relative timescales with accelerated star formation, and the slow motions of protostars. We consider stimuli to collapse from changes in the density dependence of the ionization fraction, the cosmic ray ionization rate, and various dust properties at densities above ~105 cm-3. We favor the standard model of subcritical GMC envelops and suggest they would be long-lived if not for disruption by rapid star formation in GMC cores. The lifecycle of GMCs is illustrated by a spiral arm section in the Hubble Heritage image of M51, showing GMC formation, star formation, GMC disruption with lingering triggered star formation, and envelope dispersal. There is no delay between spiral arm dust lanes and star formation; the classical notion results from heavy extinction in the dust lane and triggered star formation during cloud dispersal. Differences in the IMF for the different modes of star formation are considered.

Improved Design of Shearing Sections with New Calculation Models Based on 3D Finite‐Element Simulations

AbstractNew models for the Maddock and spiral shearing sections have been developed, employing three‐dimensional finite element analysis (3D FEA). These models describe the pressure‐throughput and power consumption behavior of the shearing sections for both the extrusion and the injection molding process and have been implemented in the REX 6.0 and PSI 4.0 simulation software. As a consequence it is now possible to describe the process behavior of these shearing sections within just a few seconds with the accuracy of FEA calculations. Actual Maddock shearing section (left) and actual spiral shearing section (right).magnified imageActual Maddock shearing section (left) and actual spiral shearing section (right).

Approximate method for calculating the characteristics of a radial flow pump

Similarity in flow patterns between fans and pumps provides the possibility of suggesting an approximate method for calculating radial flow pump characteristics. The proposed method uses relations expressing the energy balance of real fluids. Calculations of velocity triangles are given for a flow ahead of an impeller operating in sections with half-output, recognized as an average value. The results followed the expression within blade theory for radial impellers. While the exit angle helps to understand the blade shape at the no-lift position, the impeller losses, on the other hand, are related in a certain way to the angle of incidence. Losses at different elements of the pump are treated, at a selected point of operation, as having a constant coefficient of loss. Values of losses are calculated from the actual pressure heads. The flow through spiral bodies takes an approximate kinetic model. A spiral section having the shape of a circle provides the suitable conditions guaranteeing the operation of a single impeller along its circumference while still having the same optimum value of pump efficiency. The illustrated figures are the result of calculations made on radial impellers measured from several pump investigations.