Entire Radius Research Articles

Mass-plate impact parameters for the elastic range

When an impact load is applied laterally to a plate, the deflection gradually spreads over time until the entire plate radius is affected. The determination of effects for a short-duration impact presents substantial mathematical difficulties. The normal-mode superposition is not only awkward but it does not lead to closed-form solutions. Some of the past works gave a possibility of such a solution by assuming a certain flexural wave spreading from the impact point. The complexity involved in that was simplified in this paper. This main part of this work is based on a shear wave approach, by relating the lateral stiffness to the propagation of a shear wave from impact point. This, along with some other simplifications, makes it possible to obtain the peak contact force by using compact expressions. The development is limited to impactor mass not exceeding one-half of the plate mass. The evaluation of rebound velocity or the coefficient of restitution was successfully resolved for only a limited range of parameters. The other subtopic is the quantification of the contact problem itself, which is nonlinear by nature. A transparent method of linearization is proposed, based either on experiment or on Hertzian formulation. The results presented in this paper are compared with the answers from finite-element simulations, physical experiments and with some cases available from literature.

Theory and kinematic measurements of the mechanics of stable electrospun polymer jets

We present a simplified approach to understanding the mechanics of stable electrospinning jets based on electrohydrodynamic theory that explicitly incorporates the extensional rheology of polymeric fluids. Flow regimes of electrospun jets are identified by analogy to uniaxial extension of a fluid jet. These flow regimes predict the limiting kinematics of electrospinning jets and identify dimensionless parameters important to the control and operation of electrospinning processes. In situ kinematic measurements validate model assumptions and scaling predictions, and allow the reduction of entire jet radius and velocity profiles to several key parameters. The model predictions are shown to hold both above and below the entanglement concentration, as well as for solutions with added electrolyte and increased conductivity. The analysis also enables direct measurement of the apparent extensional viscosity of solutions at the high extension rates experienced during electrospinning. Finally, dimensional analysis of the model yields a correlation for electrospun fiber diameter in terms of measurable fluid properties, controlled process parameters, and measured jet variables, demonstrating the influence of mechanics in the straight portion of the jet on ultimate fiber morphology.

Madelung’s Deformity: A Spectrum of Presentation

To evaluate the hypotheses that all Madelung's deformity subjects have dyschondrosteosis (defined as short stature and mesomelia, in addition to Madelung's deformity) and to evaluate the concept that Madelung's deformity may affect the entire radius. A radiographic and medical records review was performed for 26 subjects (46 extremities) with Madelung's deformity. The radiographs were assessed for radius and ulna length, sagittal radial bow, severity of the Madelung deformity, and radiocapitellar joint space. The sagittal radial bow and the radiocapitellar joint space were used to classify subjects according to whether the Madelung deformity was limited to the distal radius or involved the entire radius. Thirty-one extremities in 18 subjects were classified as having a distal radius Madelung deformity and 15 extremities in 8 subjects were classified as having an entire radius Madelung deformity. The radius and ulna length and subject height were significantly decreased compared with age- and height-matched normal values in both groups; the entire radius group was more severely affected. In addition, the entire radius group had more severe deformities with respect to lunate subsidence and ulnar tilt. All of the entire radius subjects and 9 of 14 of the distal radius subjects had dyschondrosteosis. Madelung's deformity presents as a spectrum. It may affect the entire radius or it may affect only the distal radius. Extremities with involvement of the entire radius have a shorter radius and ulna, decreased height, and a more severe deformity than extremities with involvement of only the distal radius. Additionally, most subjects with Madelung's deformity have dyschondrosteosis.

On the existence and structure of a mush at the inner core boundary of the Earth

It has been suggested about 20 years ago that the liquid close to the inner core boundary (ICB) is supercooled and that a sizable mushy layer has developed during the growth of the inner core. The morphological instability of the liquid–solid interface which usually results in the formation of a mushy zone has been intensively studied in metallurgy, but the freezing of the inner core occurs in very unusual conditions: the growth rate is very small, and the pressure gradient has a key role, the newly formed solid being hotter than the adjacent liquid. We investigate the linear stability of a solidification front under such conditions, pointing out the destabilizing role of the thermal and solutal fields, and the stabilizing role of the pressure gradient. The main consequence of the very small solidification rate is the importance of advective transport of solute in liquid, which tends to remove light solute from the vicinity of the ICB and to suppress supercooling, thus acting against the destabilization of the solidification front. For plausible phase diagrams of the core mixture, we nevertheless found that the ICB is likely to be morphologically unstable, and that a mushy zone might have developed at the ICB. The thermodynamic thickness of the resulting mushy zone can be significant, from ∼ 100 km to the entire inner core radius, depending on the phase diagram of the core mixture. However, such a thick mushy zone is predicted to collapse under its own weight, on a much smaller length scale ( ≲ 1 km). We estimate that the interdendritic spacing is probably smaller than a few tens of meter, and possibly only a few meters.

Comparison Between Experimental Measurements and Numerical Simulations of Spheromak Formation in SSPX

Data from a recently installed insertable magnetic probe array in the Sustained Spheromak Physics Experiment (SSPX) [E. B. Hooper et al., Nucl. Fusion 39, 863 (1999)] is compared against NIMROD [C. R. Sovinec et al., J. Comp. Phys. 195, 355 (2004)], a full 3D resistive magnetohydrodynamic code that is used to simulate SSPX plasmas. The experiment probe consists of a linear array of chip inductors arranged in clusters that are spaced every 2 cm, and spans the entire machine radius at the flux conserver midplane. Both the experiment and the numerical simulations show the appearance, shortly after breakdown, of a column with a hollow current profile that precedes magnetic reconnection, a process essential to the formation of closed magnetic flux surfaces. However, there are differences between the experiment and the simulation in how the column evolves after it is formed. These differences are studied to help identify the mechanisms that eventually lead to closed-flux surfaces (azimuthally averaged) and flux amplification, which occur in both the experiment and the simulation.

Charging apparatus with a revolving distributor: Five years of successful operation on blast furnace No. 3 at the Bhilai Metallurgical Plant

A rotary charging apparatus (RCA) has been in use on 1033-m3 at the Bhilai Metallurgical Plant (in India) since 1998. The RCA is a new type of charging apparatus in which the main working element is a five-vane revolving charge distributor that provides for multi-flow, multi-layered distribution of the charge materials in the top of the furnace. The revolving distributor makes it possible to flexibly and efficiently regulate the distribution of the materials over the entire radius of the top by changing the speed and direction of rotation of the rotor. The operational and design features of the RCA ensure a higher quality distribution of the materials in the top, which in turn leads to a significant savings of coke and an increase in furnace productivity. The total cost of maintaining and repairing the RCA is proving to be substantially lower than the corresponding costs for standard double-bell-and-hopper and chute-type charging apparatuses. The investment in the RCA is recovered in six months or less.

The stability of ballooning modes in tokamaks with internal transport barriers

Modern tokamaks can produce transport barriers (TBs)—localized regions with an increased energy confinement. Previous studies have been unable to examine the stability of internal TBs to radially extended short-wavelength magnetohydrodynamic instabilities (“ballooning modes”), for the usual case with a sheared plasma flow and a magnetic shear that passes through zero near the TB. An established technique is adapted to study this situation, finding instability if (1) there is a low-pressure gradient, and if (2) the nearest “resonant surface” at which a Fourier mode is resonant, is sufficiently close. Surprisingly, flow shear is no more stabilizing than for magnetic shears of order one. This is explained. Without a strongly stabilizing mechanism, ballooning modes will fundamentally limit a TB's radial extent, preventing them from extending across the entire plasma radius.

Active beam spectroscopy diagnostics for ITER: Present status (invited)

An overview is given of the present design of the active beam spectroscopy diagnostics for the ITER. Present spatial resolution and signal-to-noise indicate that, in principle, all proposed measurements are possible covering the entire plasma minor radius. Calculations show that the mirror based periscopes and the impurity coating of the first mirror affect the signal strength and the polarization characteristics of the measured spectra having an impact in the measurement accuracy. On-line calibration techniques and methods to access the first mirror status are addressed.

Design study for International Thermonuclear Experimental Reactor high resolution x-ray spectroscopy array

The impurity line and continuum emission for International Thermonuclear Experimental Reactor (ITER) reference H-mode and Internal Transport Barrier (ITB) plasmas were modeled using the SANCO impurity transport code. Using the instrument sensitivity for a spatially resolving crystal spectrometer array with doubly-curved crystals and two-dimensional detectors, signals, and signal-to-noise ratios were calculated for impurities including argon, iron, and krypton. These were shown to have lines suitable for the measurement of the ion temperature (0.5–30 keV) and the rotation over almost the entire plasma minor radius. The main contribution to the signal-to-noise is the plasma continuum radiation on which the lines are superimposed. The tolerable impurity concentration is limited by the incremental radiated power ΔPrad, there being a broad operating range between about 100 kW and 10 MW. The spectrometer array has now been integrated into the ITER design. A quasitomographic technique to reconstruct the Ti and rotation profiles, is reported by Ingesson et al. [C. Ingesson, these proceedings].

Iteration method for the inversion of simulated multiwavelength lidar signals to determine aerosol size distribution

A new method is proposed to derive the size distribution of aerosol from the simulated multiwavelength lidar extinction coefficients. The basis for this iteration is to consider the extinction efficiency factor of particles as a set of weighting function covering the entire radius region of a distribution. The weighting functions are calculated exactly from Mie theory. This method extends the inversion region by subtracting some extinction coefficient. The radius range of simulated size distribution is 0.1–10.0μm, the inversion radius range is 0.1–2.0μm, but the inverted size distributions are in good agreement with the simulated one.

The Axial α-Helices and Radial Spokes in the Core of the Cryo-negatively Stained Complex Flagellar Filament of Pseudomonas rhodos: Recovering High-resolution Details from a Flexible Helical Assembly

Of the two known “complex” flagellar filaments, those of Pseudomonas are far more flexible than those of Rhizobium. Their diameter is larger and their outer three-start ridges and grooves are more prominent. Although the symmetry of both complex filaments is similar, the polymer's linear mass density and the flagellin molecular mass of the latter are lower. A recent comparison of a three-dimensional reconstruction of the filament of Pseudomonas rhodos to that of Rhizobium lupini indicates that the outer flagellin domain (D3) is missing in R.lupini. Here, we concentrate on the structure of the inner core of the filament of P.rhodos using field emission cryo-negative staining electron microscopy and a hybrid helical/single particle reconstruction technique. Averaging 158 filaments caused the density band corresponding to the radial spokes to nearly average out due to their variability and inferred flexibility. Treating the Z=0 cross-sections through the aligned individual three-dimensional density maps as images, classifying them by correspondence analysis (using a mask containing the radial spokes domain) and re-averaging the subclasses (using helical reconstruction techniques) allowed a recovery of the radial spokes and resolved the α-helices in domain D0 and the triple α-helical bundles in domain D1 at a resolution of 1/7Å−1. Although the perturbed components of the helical lattice are present along the entire filament's radius, the interior of the complex filament is similar to that of the plain one, whereas it's exterior is altered. Reconstructions of vitrified and cryo-negatively stained plain, right-handed filaments of Salmonella typhimurium SJW1655 prepared and imaged under conditions identical with those used for P.rhodos confirm the similarity of their inner cores and that the secondary structures in the interior of the flagellar filament can, under critical conditions of image recording and correction, be resolved in negative stain.

Templated synthesis of inorganic hollow spheres with a tunable cavity size onto core-shell gel particles.

Titania/polymer capsules and hollow titania spheres are prepared by using sulfonated-polystyrene core–shell gel particles as templates. The titania shell thickness and the cavity size are controlled in the entire particle radius range. If an electric field is applied during synthesis, hollow spheres with pillared surfaces (depicted) are produced.

Suitability of CAE neural networks and FEM for prediction of wear on die radii in hot forging

Prediction of tool wear in hot die forging along the entire arbor radius by wear models known so far is a very difficult task. On these parts of tools significant changes of contact pressure and sliding lengths occur along the die curvature during the plastic flow of material formed. A new approach presented in the paper combines the use of a conditional average estimator neural network (CAE NN) with the exploitation of results obtained by the finite element method (FEM) and also data from other sources. Consequently new parameters as well as the results of experimental work can be taken into account. In this paper a brief overview of models for prediction of tool (die) wear are discussed. The theoretical background of CAE NN, as well as its application to the modeling of the tool wear phenomenon, is presented. Some results of FEM analysis of the hot forging process that serve as input parameters in the CAE NN model are also briefly discussed. Two relevant practical applications are shown. In the first example, tool wear was modeled at a higher number of strokes (blows), by knowing wear at a lower number of strokes. In the second example, the number of strokes was the output parameter—the number of strokes causing predetermined wear at any point of the tool engraving curvature (arbor radius) was predicted. A comparison between the measured and predicted values of wear demonstrated good agreement that was assessed by a corresponding coefficient of determination.

Characterization of dynamic three-dimensional strain fields in the canine radius

This note describes a method to approximate the 3-D mechanical environment of a long bone during a normal daily activity. Our specific goal was to characterize the temporal and spatial strain distributions in the mid-shaft region of the canine radius during gait. Direct measurement of strains along the entire surface of in vivo bone is not feasible, so we employed a combination of experimental measurements and numerical interpolation techniques to approximate the time-varying longitudinal strain distribution. Using standard in vivo strain gauging techniques, we measured dynamic strains at nine locations (three locations on each of three cross sections, data pooled from two experimental animals) on the canine radius during trotting gait. These in vivo strain measurements were then used to approximate the time course of the strain field for the entire radius mid-shaft region using a 3-D numerical interpolation scheme using finite element basis functions. Despite limitations in the present implementation of the method, the results show that there are considerable time-dependent variations in the strain distribution occurring at different transverse sections along the length of the diaphysis with substantial anteroposterior bending and rotation of neutral axis locations during the gait cycle.

Production Functions of Film Drops by Bursting Bubbles

Abstract Experimental results of Blanchard and Syzdek and of Resch and Afeti on the production of film drops by bubbles bursting at the surface of seawater were parameterized earlier by Wu. More recently, comprehensive observations have been carried out by Spiel. All these measurements, covering different size ranges of film drops, are shown to quantitatively complement each other. Through combining these results, the production of film drops has been quantified, in terms of both number and size distribution, over the entire radius range 0.01–250 μm. The average size of film drops is about 25 μm in radius, which is much larger than the commonly cited radius for film drops of 5 μm. In addition, all the results are shown to follow a simple rule; that is, the ratio between the total surface area of film drops and the surface area of their parent bubble is a constant.

Self-similar evolution of wind-blown bubbles with mass loading by hydrodynamic ablation

We present similarity solutions for adiabatic bubbles that are blown by winds having time independent mechanical luminosities and that are each mass-loaded by the hydrodynamic ablation of distributed clumps. The mass loading is “switched-on” at a specified radius (with free-expansion of the wind interior to this point) and injects mass at a rate per unit volume proportional to Mr where δ = 4/3 (1) if the flow is subsonic (supersonic) with respect to the clumps. In the limit of negligible mass loading a similarity solution found by Dyson (1973) for expansion into a smooth ambient medium is recovered. The presence of mass loading heats the flow, which leads to a reduction in the Mach number of the supersonic freely-expanding flow, and weaker jump conditions across the inner shock. In solutions with large mass loading, it is possible for the wind to connect directly to the contact discontinuity without first passing through an inner shock, in agreement with previous hydrodynamic simulations. In such circumstances, the flow may or may not remain continuously supersonic with respect to the clumps. For a solution that gives the mass of swept-up ambient gas to be less than the sum of the masses of the wind and ablated material, λ ∼ −2, meaning that the exponent of the density profile of the interclump medium must be at most slightly positive, with negative values preferred. Maximum possible values for the ratio of ablated mass to wind mass occur when mass loading starts very close to the bubble center and when the flow is supersonic with respect to the clumps over the entire bubble radius. Whilst mass loading always reduces the temperature of the shocked wind, it also tends to reduce the emissivity in the interior of the bubble relative to its limb, whilst simultaneously increasing the central temperature relative to the limb temperature. The maximum temperature in the bubble often occurs near the onset of mass loading, and in some cases can be many times greater than the post-inner-shock temperature. Our solutions are potentially relevant to a wide range of astrophysical objects, including stellar wind-blown bubbles, galactic winds, starburst galaxy superwinds, and the impact of an AGN wind on its surrounding environment. This work complements the earlier work of Pittard et al. (2001) in which it was assumed that clumps were evaporated through conductive energy transport.

Threshold gain and single-mode oscillation of two-dimensional photonic bandgap defect lasers

Defect laser behavior was simulated as a function of various parameters. When the crystal size was increased from 8/spl times/8 to 12/spl times/12 cylinders, the quality factor of the defect cavity increased from 6/spl times/10/sup 3/ to 5/spl times/10/sup 6/ while the threshold gain decreased by two orders of magnitude, It was predicted that a triangular-lattice photonic defect laser would be polarized in the /spl Gamma/-M direction. The defect laser studied usually showed multi-mode oscillation with a large defect radius, where the threshold gain was small. When the refractive indices of the cylinders and the defect, surrounded by air, were both 3.5, single-mode oscillation and a small threshold gain (4 cm/sup -1/) were, nevertheless, achieved at suitable device parameters that made the side-mode suppression ratio sufficiently large at 10/sup 3/. A single-mode oscillation and a small threshold gain (less than 20 cm(/sup -/1)) were also predicted over the entire defect radius range when the defect refractive index was decreased from 3.5 to 1.5.

Frequency dependent effects in helicon plasmas

Variations in the plasma parameters of a large volume, helicon source as a function of applied rf power (0–2 kW), driving frequency (8–18 MHz), magnetic field (0–1.4 kG) and fill pressure (2–10 mTorr) have been studied. The transitions between the capacitive, inductive, and resonant helicon mode are consistent with previous experiments. Our data indicate that the transition to the helicon mode occurs at a unique magnetic field, independent of the driving frequency. Based on the helicon wave dispersion relation, from which helicon wavelengths can be calculated, the observed variations in plasma density as a function of driving frequency suggest that the wavelength of the helicon wave is a weak function of driving frequency. Calculation of the electron energies which correspond to the phase velocity of the driving wave (i.e., Landau damping) suggest that either Landau damping cannot be responsible for the efficient ionization of helicon sources, or that the helicon portion of the discharge does not extend over the entire radius of the apparatus.

An inversion technique to obtain full poloidal velocity profiles in a tokamak plasma

An inversion technique has been developed to calculate local poloidal rotation velocities of impurity ions from line-integrated measurements of an extended emission source in a tokamak plasma. This technique can recover radial spatial resolution that is lost due to the curvature of the field lines. With charge exchange emission from neutral beams, it can be used to obtain poloidal velocity profiles across the entire minor radius of the plasma without requiring restricted neutral beam height to localize the emission. The technique consists of two Abel-like matrix inversions to obtain the emissivity and the velocity-weighted emissivity from which the velocity is obtained. Use of the neutral beams breaks the assumed symmetry, but knowledge of the beam deposition and geometry allow analogous matrices to be generated. The inversion technique is demonstrated with a simulation of a poloidal rotation diagnostic for the TFTR tokamak with tangential neutral beams with a height of 80 cm. Two opposing vertical views are required to handle effects of the charge exchange cross section, which can cause apparent velocities greatly in excess of expected poloidal velocities. The simulated errors due to the inversion process are about 1.5 km/s near the plasma center.

An inversion technique to obtain full poloidal velocity profiles in a tokamak plasma (abstract)

An inversion technique has been developed to calculate local poloidal rotation velocities of impurity ions from line-integrated measurements of an extended emission source in a tokamak plasma. This technique can recover radial spatial resolution that is lost due to the curvature of the field lines. With charge exchange emission from neutral beams, it can be used to obtain poloidal velocity profiles across the entire minor radius of the plasma without requiring restricted neutral beam height to localize the emission. The technique consists of two Abel-like matrix inversions to obtain the emissivity and the velocity-weighted emissivity from which the velocity is obtained. Use of the neutral beams breaks the assumed symmetry, but knowledge of the beam deposition and geometry allow analogous matrices to be generated. The inversion technique is demonstrated with a simulation of a poloidal rotation diagnostic for the TFTR tokamak with tangential neutral beams with a height of 80 cm. Two opposing vertical views are required to handle effects of the charge exchange cross section which can cause apparent velocities greatly in excess of expected poloidal velocities. The simulated errors due to the inversion process are about 1.5 km/s near the plasma center.