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Artykuły w czasopismach na temat "Conical form of breakdow"
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Moise, Pradeep, i Joseph Mathew. "Bubble and conical forms of vortex breakdown in swirling jets". Journal of Fluid Mechanics 873 (24.06.2019): 322–57. http://dx.doi.org/10.1017/jfm.2019.401.
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Experimental investigations of laminar swirling jets had revealed a new form of vortex breakdown, named conical vortex breakdown, in addition to the commonly observed bubble form. The present study explores these breakdown states that develop for the Maxworthy profile (a model of swirling jets) at inflow, from streamwise-invariant initial conditions, with direct numerical simulations. For a constant Reynolds number based on jet radius and a centreline velocity of 200, various flow states were observed as the inflow profile’s swirl parameter $S$ (scaled centreline radial derivative of azimuthal velocity) was varied up to 2. At low swirl ($S=1$) a helical mode of azimuthal wavenumber $m=-2$ (co-winding, counter-rotating mode) was observed. A ‘swelling’ appeared at $S=1.38$, and a steady bubble breakdown at $S=1.4$. On further increase to $S=1.5$, a helical, self-excited global mode ($m=+1$, counter-winding and co-rotating) was observed, originating in the bubble’s wake but with little effect on the bubble itself – a bubble vortex breakdown with a spiral tail. Local and global stability analyses revealed this to arise from a linear instability mechanism, distinct from that for the spiral breakdown which has been studied using Grabowski profile (a model of wing-tip vortices). At still higher swirl ($S=1.55$), a pulsating type of bubble breakdown occurred, followed by conical breakdown at 1.6. The latter consists of a large toroidal vortex confined by a radially expanding conical sheet, and a weaker vortex core downstream. For the highest swirls, the sheet was no longer conical, but curved away from the axis as a wide-open breakdown. The applicability of two classical inviscid theories for vortex breakdown – transition to a conjugate state, and the dominance of negative azimuthal vorticity – was assessed for the conical form. As required by the former, the flow transitioned from a supercritical to subcritical state in the vicinity of the stagnation point. The deviations from the predictions of the latter model were considerable.
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Rajamanickam, Kuppuraj, i Saptarshi Basu. "Insights into the dynamics of conical breakdown modes in coaxial swirling flow field". Journal of Fluid Mechanics 853 (22.08.2018): 72–110. http://dx.doi.org/10.1017/jfm.2018.549.
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The main idea of this paper is to understand the fundamental vortex breakdown mechanisms in the coaxial swirling flow field. In particular, the interaction dynamics of the flow field is meticulously addressed with the help of high fidelity laser diagnostic tools. Time-resolved particle image velocimetry (PIV) (${\sim}1500~\text{frames}~\text{s}^{-1}$) is employed in $y{-}r$ and multiple $r{-}\unicode[STIX]{x1D703}$ planes to precisely delineate the flow dynamics. Experiments are carried out for three sets of co-annular flow Reynolds number $Re_{a}=4896$, 10 545, 17 546. Furthermore, for each $Re_{a}$ condition, the swirl number ‘$S_{G}$’ is varied independently from $0\leqslant S_{G}\leqslant 3$. The global evolution of flow field across various swirl numbers is presented using the time-averaged PIV data. Three distinct forms of vortex breakdown namely, pre-vortex breakdown (PVB), central toroidal recirculation zone (CTRZ; axisymmetric toroidal bubble type breakdown) and sudden conical breakdown are witnessed. Among these, the conical form of vortex breakdown is less explored in the literature. In this paper, much attention is therefore focused on exploring the governing mechanism of conical breakdown. It is should be interesting to note that, unlike other vortex breakdown modes, conical breakdown persists only for a very short band of $S_{G}$. For any small increase/decrease in $S_{G}$ beyond a certain threshold, the flow spontaneously reverts back to the CTRZ state. Energy ranked and frequency-resolved/ranked robust structure identification methods – proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) respectively – are implemented over instantaneous time-resolved PIV data sets to extract the dynamics of the coherent structures associated with each vortex breakdown mode. The dominant structures obtained from POD analysis suggest the dominance of the Kelvin–Helmholtz (KH) instability (axial $+$ azimuthal; accounts for ${\sim}80\,\%$ of total turbulent kinetic energy, TKE) for both PVB and CTRZ while the remaining energy is contributed by shedding modes. On the other hand, shedding modes contribute the majority of the TKE in conical breakdown. The frequency signatures quantified from POD temporal modes and DMD analysis reveal the occurrence of multiple dominant frequencies in the range of ${\sim}10{-}400~\text{Hz}$ with conical breakdown. This phenomenon may be a manifestation of high energy contribution by shedding eddies in the shear layer. Contrarily, with PVB and CTRZ, the dominant frequencies are observed in the range of ${\sim}20{-}40~\text{Hz}$ only. We have provided a detailed exposition of the mechanism through which conical breakdown occurs. In addition, the current work explores the hysteresis (path dependence) phenomena of conical breakdown as functions of the Reynolds and Rossby numbers. It has been observed that the conical mode is not reversible and highly dependent on the initial conditions.
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KALKHORAN, I. M., M. K. SMART i F. Y. WANG. "Supersonic vortex breakdown during vortex/cylinder interaction". Journal of Fluid Mechanics 369 (25.08.1998): 351–80. http://dx.doi.org/10.1017/s0022112098001566.
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The head-one interaction of a supersonic streamwise vortex with a circular cylinder reveals a vortex breakdown similar in many ways to that of incompressible vortex breakdown. In particular, the dramatic flow reorganization observed during the interaction resembles the conical vortex breakdown reported by Sarpkaya (1995) at high Reynolds number. In the present study, vortex breakdown is brought about when moderate and strong streamwise vortices encounter the bow shock in front of a circular cylinder at Mach 2.49. The main features of the vortex/cylinder interaction are the formation of a blunt-nosed conical shock with apex far upstream of the undisturbed shock stand-off distance, and a vortex core which responds to passage through the apex of the conical shock by expanding into a turbulent conical flow structure. The geometry of the expanding vortex core as well as the location of the conical shock apex are seen to be strong functions of the incoming vortex strength and the cylinder diameter. A salient feature of the supersonic vortex breakdown is the formation of an entropy-shear layer, which separates an interior subsonic zone containing the burst vortex from the surrounding supersonic flow. In keeping with the well-established characteristics of the low-speed vortex breakdown, a region of reversed flow is observed inside the turbulent subsonic zone. The steady vortex/cylinder interaction flow fields generated in the current study exhibit many characteristics of the unsteady vortex distortion patterns previously observed during normal shock wave/vortex interactions. This similarity of the instantaneous flow structure indicates that the phenomenon previously called vortex distortion by Kalkhoran et al. (1996) is a form of supersonic vortex breakdown.
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Shtern, Vladimir, i Fazle Hussain. "Hysteresis in swirling jets". Journal of Fluid Mechanics 309 (25.02.1996): 1–44. http://dx.doi.org/10.1017/s0022112096001541.
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This paper explains hysteretic transitions in swirling jets and models external flows of vortex suction devices. Toward this goal, the steady rotationally symmetric motion of a viscous incompressible fluid above an infinite conical stream surface of a half-angle θc is studied. The flows analysed are generalizations of Long's vortex. They correspond to the conically similar solutions of the Navier-Stokes equations and are characterized by circulation Γc given at the surface and axial flow force J1. Asymptotic analysis and numerical calculations show that four (for θc ≤ 90°) or five (for θc > 90°) solutions exist in some range of Γc and J1.The solution branches form hysteresis loops which are related to jump transitions between various flow regimes. Four kinds of jump are found: (i) vortex breakdown which transforms a near-axis jet into a two-cell flow with a reverse flow near the axis and an annular jet fanning out along conical surface θ = θs < θc (ii) vortex consolidation causing a reversal of (i); (iii) jump flow separation from surface θ = θc and (iv) jump attachment of the swirling jet to the surface. As Γc and/or J1 decrease, the hysteresis loops disappear through a cusp catastrophe. The physical reasons for the solution non-uniqueness are revealed and the results are discussed in the context of vortex breakdown theories. Vortex breakdown is viewed as a fold catastrophe. Two new striking effects are found: (i) there is a pressure peak of O(Γ2c) inside the annular swirling jet; and (ii) a consolidated swirling jet forms with a reversed (‘anti-rocket’) flow force.
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Qin, Wei, Ira M. Cohen i P. S. Ayyaswamy. "Fixed Wand Electronic Flame-Off for Ball Formation in the Wire Bonding Process". Journal of Electronic Packaging 116, nr 3 (1.09.1994): 212–19. http://dx.doi.org/10.1115/1.2905688.
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In the latest generation of wire bonders, the cycle is so short that the wand electrode is kept stationary and the electronic flame off (EFO) discharge is from the side of the wire. This is the discharge that heats and melts the wire causing roll up into a ball that is pressed down onto the chip to form a ball bond. The balls must be perfectly formed with defects in the few ppm range. In the first part of the paper, the fixed, conically shaped side wand and the improved ring wand design are studied by considering the electrostatic field before the breakdown. In the second part of the paper, discharge development starting from the initial electrostatic field between a wire and a ring wand up to the breakdown, and ionization growth in the gap between the electrodes are both examined by numerical simulations. In the computations, the conservation equations for ions and electrons and Poisson’s equation have been employed for the self-consistent electric field. Based on sensitivity to wire length and wire deflection, the results show that the ring wand is a better design than the conical side wand electrode for ball formation and wire bonding. Also, positive wire polarity is preferred over negative wire polarity.
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Domenicucci, A. "Image Processing Methodology for Determining SI Precipitate Size and Density in Oxide Layers from Conical Dark Field TEM Micrographs". Microscopy and Microanalysis 7, S2 (sierpień 2001): 832–33. http://dx.doi.org/10.1017/s1431927600030233.
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Image processing techniques have been used for decades in many branches of science. with the advent of low cost, highresolution CCD cameras and the advances in personal computing, techniques previously used in other disciplines are increasingly being applied by transmission electron microscopists. The present paper gives an example of using image processing techniques for characterizing the number and size of second phase precipitates in an oxide matrix.Si inclusions in the form of Si precipitates can occur in silicon dioxide films. The inclusions are contained within the films and effectively reduce the local thickness of the oxide. This thinning results in a reduction in the voltage necessary to cause oxide breakdown; the larger is the precipitate, the lower the breakdown voltage. Knowledge of the precipitate size and density is therefore important when assessing the dielectric integrity of these films. The Si precipitates are crystalline and more or less randomly oriented within the matrix.
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Rohlena, Karel, i Martin Mašek. "Ambient fields generated by a laser spark". Nukleonika 61, nr 2 (1.06.2016): 119–24. http://dx.doi.org/10.1515/nuka-2016-0021.
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Abstract The electric and magnetic fields surrounding a laser spark formed after an optical breakdown due to a focused nanosecond laser beam in a gaseous environment are examined in order to assess their possible influence on the processes going on in the gas medium, mainly chemical reactions triggered by the spark plasma radiation. The magnetic field is generated by the standard mechanism of crossed electron density and temperature gradients, the electric field is supposed to be produced by the plasma polarization due to its radial expansion across the self-generated magnetic field. A simple model of spark plasma formation near the tip of the focal cone is assumed, with a delayed breakdown, which allows the focused laser light to sweep the whole volume of the forming spark right down to the focal caustic and thus to form a centimeter long plasma cone. In this conical geometry, the value of plasma electric dipole moment is evaluated as a measurable quantity as well as approximate values of the electric and magnetic field near the focal caustic, where they both tend to grow in magnitude.
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Posmituha, Olexander, Svyatoslav Kravets, Volodymyr Suponyev i Kazimir Glavatsky. "Determination of equivalent and optimal sizes of wedge tip from flange for the static perforation of soil". MATEC Web of Conferences 230 (2018): 01011. http://dx.doi.org/10.1051/matecconf/201823001011.
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The purpose of the study is to create a new design of the working tip for the perforation of the soil when laying two or more buildings trenchless way and determine its rational parameters. Method. It is known that for static perforation in the formation of cavities in the soil for communication is traditionally used cone-shaped working elements, which is the most common, cheap and reliable. However, the study revealed inefficiency. The design of the working elements of the soil perforation for trenchless laying of two or more buildings simultaneously in the form of a tip, which consists of a wedge-shaped part and a control part in the form of a rectangle with half-cylinders. The basic principles and mathematical dependences of determining the size of the working body are described. Scientific novelty. Regularities of changes in soil pressure on the lateral, conical and wedge surface, flat and cylindrical part of the tip, allowed to obtain an analytical dependence for the calculation of the resistance force depending on the physical and mechanical properties of the soil, the diameter and the number of cases established simultaneously. Also, when comparing the cone-cylindrical and flat tips, it can be argued that the breakdown force of the flat tip decreases from 1.2 to 1.7 times.
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BILLANT, PAUL, JEAN-MARC CHOMAZ i PATRICK HUERRE. "Experimental study of vortex breakdown in swirling jets". Journal of Fluid Mechanics 376 (10.12.1998): 183–219. http://dx.doi.org/10.1017/s0022112098002870.
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The goal of this study is to characterize the various breakdown states taking place in a swirling water jet as the swirl ratio S and Reynolds number Re are varied. A pressure-driven water jet discharges into a large tank, swirl being imparted by means of a motor which sets into rotation a honeycomb within a settling chamber. The experiments are conducted for two distinct jet diameters by varying the swirl ratio S while maintaining the Reynolds number Re fixed in the range 300<Re<1200. Breakdown is observed to occur when S reaches a well defined threshold Sc≈1.3–1.4 which is independent of Re and nozzle diameter used. This critical value is found to be in good agreement with a simple criterion derived in the same spirit as the first stage of Escudier & Keller's (1983) theory. Four distinct forms of vortex breakdown are identified: the well documented bubble state, a new cone configuration in which the vortex takes the form of an open conical sheet, and two associated asymmetric bubble and asymmetric cone states, which are only observed at large Reynolds numbers. The two latter configurations differ from the former by the precession of the stagnation point around the jet axis in a co-rotating direction with respect to the upstream vortex flow. The two flow configurations, bubble or cone, are observed to coexist above the threshold Sc at the same values of the Reynolds number Re and swirl parameter S. The selection of breakdown state is extremely sensitive to small temperature inhomogeneities present in the apparatus. When S reaches Sc, breakdown gradually sets in, a stagnation point appearing in the downstream turbulent region of the flow and slowly moving upstream until it reaches an equilibrium location. In an intermediate range of Reynolds numbers, the breakdown threshold displays hysteresis lying in the ability of the breakdown state to remain stable for S<Sc once it has taken place. Below the onset of breakdown, i.e. when 0<S<Sc, the swirling jet is highly asymmetric and takes the shape of a steady helix. By contrast above breakdown onset, cross-section visualizations indicate that the cone and the bubble are axisymmetric. The cone is observed to undergo slow oscillations induced by secondary recirculating motions that are independent of confinement effects.
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KITA, Naoaki, i HIsao HASEGAWA. "810 Interface Stresses between an Elastic Conical-form Solid and a Rigid Conical-form Hole". Proceedings of The Computational Mechanics Conference 2005.18 (2005): 245–46. http://dx.doi.org/10.1299/jsmecmd.2005.18.245.
Pełny tekst źródłaRozprawy doktorskie na temat "Conical form of breakdow"
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Randolph, Joel Howard. "Studies in Conical Form". Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/84482.
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The design of a conical room for experiencing a fleeting moment was developed through a series of demonstrative studies. The desired effect of a momentary appearance of a ray of light striking a reflective surface in a room based on the predicted relative position of the sun at set times determined the form, shape, proportions, and surface conditions of the room.Master of Architecture
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Gillis, Carole. "Minoan conical cups : form, function and significance /". Göteborg : P. Aströms, 1990. http://catalogue.bnf.fr/ark:/12148/cb388953629.
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Schlachter-Townsend, Jessica O. "Form Through Fire". Kent State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=kent1210294330.
Pełny tekst źródłaKsiążki na temat "Conical form of breakdow"
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Gillis, Carole. Minoan conical cups: Form, function, and significance. Göteborg: Paul Åströms, 1990.
Znajdź pełny tekst źródłaCzęści książek na temat "Conical form of breakdow"
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Krainer, Thomas, i Bert-Wolfgang Schulze. "On the Inverse of Parabolic Systems of Partial Differential Equations of General Form in an Infinite Space-Time Cylinder". W Parabolicity, Volterra Calculus, and Conical Singularities, 93–278. Basel: Birkhäuser Basel, 2002. http://dx.doi.org/10.1007/978-3-0348-8191-3_3.
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"CLOSED-FORM EXPRESSION OF THE CONICAL VOLUME". W Ice Microdynamics, 249–51. Elsevier, 2002. http://dx.doi.org/10.1016/b978-012734603-8/50033-8.
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Singh, Shivendra, Gurinder Singh Brar i Ashu Kumar. "A Numerical Study on Conventional Tube Flaring Process". W Advances in Transdisciplinary Engineering. IOS Press, 2022. http://dx.doi.org/10.3233/atde220735.
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Tube flaring process involves a conical tool of a certain length which is displaced to get an end flared tube, which is utilized to form a tight seal between pipes or tubes. Tube flaring refers to a kind of forging which is often a cold working operation. The tube forming process is widely used in several industries to form condenser pipes, car seat structures, exhaust piping, etc. Thin-walled tubes were used in automobiles to reduce the total weight for better performance. A conical tool is used for tube end forming in which the tool is moved into the tube known as conventional tube flaring. In this work, a numerical study was directed using FEA software ANSYS/Implicit which is used to analyze the stress conditions involved in tube flaring. Here, the tool is considered rigid and displaced by using displacement control by 25 mm, and other parameters were studied at this displacement. Effects of different semi-cone angles were also considered for the study.
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Sönmez, Barış Emre. "Roman Period Glass Unguentariums at the Hacibektas Veli Archeology Museum". W Current Approaches in Social Sciences. Özgür Yayınları, 2023. http://dx.doi.org/10.58830/ozgur.pub167.c752.
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The aim of this study is to examine the glass unguentariums from the Roman Period in Hacibektas Veli Archeology Museum in terms of technique and form. The glass unguentariums in Hacibektas Veli Archeology Museum are classified as tube, bulbous, conical and candelabra. There are 12 glass unguentariums from the Roman Period in total in the museum. 11 of them were brought to the museum by purchasing; One of them was found around Suluca Karahöyük and brought to the museum. Of the glass unguentarium, 6 are tubular in shape, 1 are candelabra in shape, 3 are bulbous in shape and 2 are conical in shape. The lengths of tubular unguentariums vary between 9.1 cm and 13.4 cm; The length of the candelabra-shaped unguentarium is 13 cm, the length of the bulbous-shaped unguentarium is between 10.3 cm and 17.6 cm, and the length of the conical unguentarium is 9.3 cm. Glass unguentariums consist of dark green, colorless transparent, pale green, light green, light blue-green, blue-green colors. The earliest glass unguentarium belongs to the middle of the 1st century AD, and the latest glass unguentarium is dated to the 3rd century AD.
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"An analytical, closed-form stiffness model for preloaded conical rubber mounting in the audible frequency range". W Constitutive Models for Rubber IV, redaktorzy M. Coja i L. Kari, 501–6. Routledge, 2017. http://dx.doi.org/10.1201/9781315140216-85.
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Rocco Jr., Leopoldo. "Disintegration of Liquid Sheet Produced by Swirl Injector". W Energetic Materials Research, Applications, and New Technologies, 133–45. IGI Global, 2018. http://dx.doi.org/10.4018/978-1-5225-2903-3.ch006.
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The development of liquid sheets that emerges from nozzles is influenced mainly by their initial speed and by the physical properties of the liquid and the ambient gas. A minimum speed of the sheet is necessary for its enlargement against the superficial tension that tends to contract the surface. As this speed increases, the sheet expands until a main extremity is formed, where balance exists among the superficial tension and the inertial forces. The form and regularity of the sheet's disintegration process has influence in the size distribution of the produced drop and in the Sauter mean diameter (SMD). The initial thickness of the produced liquid sheet is important to determine the medium size of obtained drops. It was observed that thicker films produce thicker ligaments and larger drops. The medium drop diameter produced in conical sheets of pressurized swirl atomizers is calculated according to the thickness of the sheets and in the wavelength for the maximum growth tax.
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Singh, Jyoti, Niteen P. Borane i Rajamouli Boddula. "Milestone Developments and New Perspectives of Nano/Nanocrystal Light Emitting Diodes". W Light-Emitting Diodes - New Perspectives [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.108907.
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Light emitting diode (LED) is a one type of p/n junction semiconductor device which is used in less energy consumption for numerous lighting functions. Because of their high performance and long existence, their eye-catching application is getting increasing numbers in recent times. LEDs are nowadays defined as using the “ultimate light bulb”. In a previous couple of years, its efficiency has been multiplied through converting it to nano size. This new light-emitting has a nano-pixel structure and it affords high-resolution performance and the geometry of the pixel is cylindrical or conical form. Due to the fact that the previous few years, a few impurity-doped nanocrystal LEDs are varying a good deal in trend. Its performance is very excessive and consumes a smaller amount of voltage. Its monochromatic behavior and indicator excellent are shown publicly demanded in the market and in this work, it’s covered evaluations of the fundamental’s standards of LEDs and the specific mixed metallic and nanocrystal shape of emitters. In addition, it covers the upcoming challenges that the current trend is working to resolve to get efficient materials to fulfill the future energy crisis.
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Orde, Sam. "Strain imaging in right ventricle assessment". W Oxford Textbook of Advanced Critical Care Echocardiography, redaktorzy Anthony McLean, Stephen Huang i Andrew Hilton, 343–50. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780198749288.003.0027.
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The right ventricle is now recognized as being integral to cardiac mechanics and analysis of its function is an essential part of any echocardiogram performed in the critically ill patient. However, it has a complex triangular conical shape and is located retrosternally making it difficult to image. Unlike the left ventricle (LV) with its myocardial fibres in many different directions, the right ventricle (RV) has a predominance of longitudinal fibres with most of its movement being in a basal to apex direction. This makes it sensitive to analysis with speckle tracking echocardiography analysis of longitudinal strain: commonly reported as right ventricle free wall strain. Strain is a measure of relative myocardial deformation analysed through tracking of the speckles that make up the myocardium on the two-dimensional B-mode image. It is a postprocessing imaging tool and experience in echocardiography is required before tackling this form of assessment. Strain is sensitive, reproducible, angle independent, not prone to translational error like other conventional echocardiography tools and most importantly can recognize cardiac dysfunction and mechanics that cannot be described by other non-invasive imaging techniques. No echocardiography parameter used to assess right ventricle function is perfect, including right ventricle strain assessment. However its advantages are witnessed by the fact that it has entered clinical practice (exclusively to cardiology departments at this stage) in many larger centres around the world.
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Dalton, David R. "Drinking the Wine". W The Chemistry of Wine. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190687199.003.0035.
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The bottled beverage before you is to be opened. This work has already described the bottle (colorless or not), the closure (screw cap, synthetic cork and cork), and the contents (the wine). If the wine is not a table wine (vin ordinaire or vin de pays) which is simply enjoyed in a family or informal surrounding where the details of the container into which it is poured are less important, then it is generally found that: (a) clear colorless glass or crystal is used so that the visual appeal of the beverage can be enjoyed; (b) the bowls of wine glasses (except for sparkling wines and dessert wines) will be tapered upward from the stem into a bulbous shape which diminishes again at the top; and (c) the rim of the glass will be thin enough to allow it to be unnoticed when the wine is sipped. It is held that these are important, and in particular, the shape of the glass helps retain the more volatile constituents for the consumer’s enjoyment. Bowls used in glasses for red wines are more rounded so that when half full, the surface area is large. For white wines, this is considered less important, and of course, for Champagne and other sparkling wines, where conical flutes are used, a small surface area is avoided to enhance the flow of bubbles. As the wine briefly stands, perhaps having been swirled, it is often found that “legs” or “tears” of wine are seen to form on the wall above the surface. Their appearance is, in part, a function of temperature as well as the alcohol content of the wine and the resulting surface tension of the liquid. Then, using capillary action, the liquid climbs the side of the glass. Both alcohol and water evaporate, but the alcohol evaporates faster, so more liquid is drawn up from the bulk. The wine thus moves up the side of the glass and forms droplets that run back down the glass.
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Robinson, Max, Keith Hunter, Michael Pemberton i Philip Sloan. "Diseases of the teeth and supporting structures". W Soames' & Southam's Oral Pathology. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199697786.003.0010.
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A wide variety of processes can affect the formation of teeth during development. The number, size, shape, and quality of dental hard tissue may be abnormal and teeth may erupt early or be prematurely shed or resorbed. When a child presents with a tooth abnormality, the clinical and radiographic features are often distinctive and management depends on diagnosis (Box 5.1). Broadly, developmental abnormalities of the teeth can be either genetically determined or acquired as a result of injurious processes affecting the developing teeth. It can be problematic to make a diagnosis, particularly when teeth initially erupt. Sometimes pathological examination of a shed or extracted tooth by ground sectioning (for enamel) or conventional sectioning of a decalcified tooth can provide a diagnosis. Research has provided insights into the genetic and structural basis of dental anomalies, and has resulted in a complex and extensive classification of subtypes. Minor abnormalities, such as failure of development of a few teeth or enamel erosion in adult life, may be dealt with in general dental practice, but it is advisable to refer younger patients with more complex or extensive dental abnormalities to a specialist in child dental health, with links to expert diagnostic facilities and input from orthodontic and restorative colleagues. The publically available Online Mendelian Inheritance in Man (OMIM) database provides an invaluable resource for genetic disorders, including dental abnormalities. Supernumerary teeth are common and may be rudimentary in form or of normal morphology, when they are referred to as supplemental teeth. The most common supernumerary tooth occurs in the mid- line of the maxillary alveolus and is referred to as a mesiodens, which usually has a conical shape. Eruption of adjacent normal successor teeth may be impeded by a mesiodens, which is an indication for its removal. Most supernumerary teeth occur as a sporadic event in development, but multiple extra teeth can be found in certain developmental disorders. Failure of development of tooth germs results in teeth missing from the dental arch and is referred to as hypodontia. Most often the missing teeth are third molars, second premolars, and upper lateral incisors. Hypodontia is more common in the permanent dentition than in the primary teeth.
Streszczenia konferencji na temat "Conical form of breakdow"
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Duwig, Christophe, Laszlo Fuchs, Arnaud Lacarelle, Matthias Beutke i Christian Oliver Paschereit. "Study of the Vortex Breakdown in a Conical Swirler Using LDV, LES and POD". W ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27006.
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Modeling and understanding the vortex breakdown is a key issue of modern Lean Premixed Combustors. The main difficulty of the problem is the unsteady behavior of this type of flow: Large structures resulting from vortex breakdown and the swirling shear-layers, affect directly the flame stabilization leading to heat-release fluctuations and combustion instabilities. Consequently, one needs to capture and understand turbulent coherent structures dynamics for designing efficient burners. This task is particularly challenging since it deals with capturing coherent motions within a chaotic system and should be done using state-of-the art numerical and experimental techniques. The present work focuses on the experimental and numerical study of iso-thermal vortex breakdown in a conical swirler. Experimental investigations were performed with 2D Laser Doppler Velocimetry (LDV) and Hotwire Anemometry at the outlet of the combustor model. Averaged velocity fields and RMS values are showing a strong central recirculation zone. In addition, characteristic frequencies of the flow have been exhibited showing the strong influence of large scale turbulent fluctuation on the flow pattern. These measurements showed also the impact of different outlet geometries on the strength and position of the coherent structures of the flow. Further, Large Eddy Simulation (LES) has been used to obtain a 4D description of the flow. Comparison with LDV profiles showed a good agreement, indicating that the LES tool captures accurately the flow. The LES results were then processed for capturing and identifying the coherent structures. Firstly, characteristic frequencies were analyzed. Here also a good agreement with the experimental data was achieved. Secondly the cores of the vortices were visualized providing a good insight into the unsteady flow pattern. Finally, Proper Orthogonal Decomposition (POD) was applied to the 4D field in order to identify the contribution of different large scale fluctuation modes. The presence of the Precessing Vortex Core (PVC) corresponding to a pair of helical structures was captured.
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Fang, Yang, Zhang Peng, Guo Chen Jiang i Xu Jia Dong. "Analysis and synthesis of a multi-arm conical spiral antenna to form shaped-conical radiation patterns". W 2006 7th International Symposium on Antennas, Propagation & EM Theory. IEEE, 2006. http://dx.doi.org/10.1109/isape.2006.353455.
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Burmberger, Stephan, Christoph Hirsch i Thomas Sattelmayer. "Designing a Radial Swirler Vortex Breakdown Burner". W ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90497.
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Most gas turbine premix burners without centrebody employ the breakdown of a swirling flow at the transition between the mixing section and the combustor for aerodynamic flame stabilization [1]. As the formation of the desired vortex breakdown pattern depends very sensibly on the distribution of axial and azimuthal velocity in the mixing section, the design of suitable swirlers is usually a cumbersome iterative process. The presented burner design was found through the implementation of design guidelines derived from CFD-calculations and on the basis of analytical considerations [5]. The swirling flow is generated by a radial swirler with tangential inlets. In order to stabilize the flow pattern, the swirling flow confines a slow non-swirling flow on the centreline. The centre flow being set into azimuthal motion creates increasing azimuthal velocity in streamwise direction in the vortex core. This process is reinforced by a conical nozzle and leads to the production of positive azimuthal vorticity inside the nozzle which stabilizes the flow field. First atmospheric test runs and Large Eddy Simulations of the isothermal as well as reactive flow field prove that the design goals have been reached: The burner creates stable vortex breakdown in the primary zone of the combustion chamber without flame flashback or backflow on the centreline over the entire operating range and even for difficult fuels like hydrogen containing gases. This finding indicates that reliable vortex breakdown burners with remarkable fuel flexibility can be designed using the guidelines presented in [5].
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Allwright, J. C. "Positive semidefinite matrices, conical hulls, m-form numerical ranges and stabilization". W 29th IEEE Conference on Decision and Control. IEEE, 1990. http://dx.doi.org/10.1109/cdc.1990.203731.
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Bautista-Clemente, Francisco Javier, Manuel Campos-García, Daniel Aguirre, Dulce Gonzalez-Utrera i Brenda Villalobos-Mendoza. "Conical null-screen design for evaluating fast free-form convex surfaces". W Optical Measurement Systems for Industrial Inspection XIII, redaktorzy Peter Lehmann, Wolfgang Osten i Armando Albertazzi Gonçalves. SPIE, 2023. http://dx.doi.org/10.1117/12.2673860.
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Burmberger, Stephan, Christoph Hirsch i Thomas Sattelmayer. "Design Rules for the Velocity Field of Vortex Breakdown Swirl Burners". W ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90495.
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Most gas turbine premix burners without centrebody employ the breakdown of a swirling flow at the transition between the mixing section and the combustor for aerodynamic flame stabilization. As the formation of the desired vortex breakdown pattern depends very sensibly on the shape of the axial and azimuthal velocity profiles in the mixing section, the design of suitable swirlers is typically a cumbersome process and requires an iterative approach consisting of numerical as well as experimental development steps to be iteratively applied until a geometry is found, that provides a spatially as well as temporarily stable vortex breakdown in the primary zone of the combustion chamber without backflow on the centerline of the vortex into the swirler. These difficulties stem from the lack of generally applicable aerodynamic design criteria. The paper attempts to contribute to the development of such design guidelines, which lead quickly to successful swirler designs without need for an excessive number of iterations. For this purpose a family of swirl profiles was generated and the corresponding axial velocity profiles were calculated assuming several radial total pressure distributions. In the next step, the flows were calculated using CFD in order to find out, which velocity profiles produce stable vortex breakdown bubbles at the burner exit. This study reveals that the stable breakdown of the vortex can be achieved for a wide range of velocity distributions, if the radial total pressure distribution is properly selected. However, the radial total pressure distribution in the vortex core is essential for the robustness of the design. Interestingly, velocity profiles with constant total pressure do not show a stable transition of the velocity field at the cross-sectional area change at the entrance of the combustion chamber. In addition, theoretical considerations reveal that an increase of the azimuthal velocity in the vortex core in streamwise direction avoids backflow on the centreline as well as flame flashback. This increase can be achieved using a slightly conical nozzle and introducing a swirl free jet on the centreline upstream of the mixing zone. All effects are explained using the vorticity transport equation.
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Mori, Toshihiko, Kunihiko Nakashima i Petros Abraha. "Thread Formation Mechanism by Planetary Conical Rolling". W ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-1028.
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Abstract Planetary conical rolling, PCR, is a large deformation tube forming process that produces high accuracy products. PCR process can therefore be used to produce features on the surface of tubes without an overall distortion. In this research, forming of a thread feature on the surface of thin tubes is experimentally examined. The results show thread forming process is composed of three step by step stages that form a high precision tube surface features.
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Vallecchi, Andrea. "Rigorous closed-form formulas for the scattering from plane angular sectors with conical-section boundaries". W 2006 1st European Conference on Antennas and Propagation (EuCAP). IEEE, 2006. http://dx.doi.org/10.1109/eucap.2006.4585082.
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Liepins, Atis A., i Javier Arnez. "Lateral Influence Coefficients for a Thin Conical Shell Frustum". W ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45298.
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Thin conical shell components are often used in vertical process vessels, bins, and water storage tanks. When exposed to the elements, such structures may be subjected to lateral wind forces and seismic accelerations. For calculations of lateral response of such structures with simplified models, in the form of vertical beams, lateral influence coefficients for thin conical frustum shells are useful. To compute lateral influence coefficient for conical frusta, asymmetric solutions of shell equations for cones are needed. The literature on asymmetric solutions for conical shells is sparse. Hoff [1] derived equations suitable over a limited range of parameters for asymmetric response of conical shells and indicated possible solutions using Fourier and power series. In his discussion of Hoff’s work, Pohle [2] indicated that an asymptotic solution of the equations is useless because of its validity over an impractical range of parameters. Seide [3] derived equations that removed the limitations of Hoff’s equations. Wilson [4] proposed solutions by separation of variables and power series. The slowly converging power series were summed using a computer for a conical panel under distributed loading. Chandrashekhar and Karekar solved the equations for a conical frustum under wind loading by expanding the solution in Fourier series in the circumferential direction, and applying finite differences in the meridional direction. The difference equations were solved using a computer. Derived here are closed-form expressions for thin conical shell frusta based on the membrane theory of shells. These influence coefficients are compared with finite element results for a conical shell, with specific geometry and material properties, for which wall bending is included.
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Gurunathan, B., i S. G. Dhande. "A Computer Aided Geometric Method for Development of Conical Convolutes". W ASME 1987 Design Technology Conferences. American Society of Mechanical Engineers, 1987. http://dx.doi.org/10.1115/detc1987-0047.
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Abstract Convolutes are single curved, ruled surfaces formed by moving a plane tangent to two curves called the directrices. Conical convolutes are one form of convolutes. If atleast one of the two planar directrices is a super-ellipse, then the surface is called a super-conical convolute. Necessary mathematical expressions for the geometrical details as well as the development of the super-conical convolute surface are given in this paper. Also a suitable algorithm for the development of the surface is given. An illustrative case study is presented.