Spiral Sheet Research Articles

Strengthening of reinforced concrete columns incorporating different configurations of stainless-steel plates

Reinforced concrete columns may need to be strengthened to support additional load arising from structural upgrades of existing structures or for retrofitting purposes. There is an increasing demand for sustainable and durable construction materials and techniques for strengthening and retrofitting purposes. Existing studies proposed additional jacketing using steel tubes or fiber-reinforced polymer (FRP). However, steel tubes can corrode when exposed to harsh environments whereas jacketing using FRP is very expensive. This study proposes innovative strengthening techniques using exterior bonding of stainless-steel plates (SSP) strips. SSP offers higher strength and corrosion resistance compared to steel and FRP materials. This paper presents an experimental and numerical study on strengthening reinforced concrete columns by innovative exterior bonding of SSP strips. A total of nine reinforced concrete column specimens are experimentally tested under axial compression loading to failure. The columns are strengthened using two different innovative techniques namely bonding stainless-steel plates to the exterior of the columns in flat as well as spirally wrapped around the columns. The cracking load, ultimate load and energy absorption capacity of the strengthened columns are found to be increased within a range of 45%− 162%, 26%− 112% and 34%− 190%, respectively when compared to the unstrengthened control column. The spacing of the SSP significantly effects the performance of strengthened columns. The ultimate load of the columns with reduced spacing increased as high as 44.9%. Additionally, employing a continuous full-height stainless steel spiral sheet yielded the most significant ultimate strength gains, calculated as high as 112% compared to the unstrengthened column although this led to an increase in the cost of the columns. A nonlinear finite element model (FEM) is also performed of the tested columns and validated the numerical prediction against the test results. The FEM is found to accurately predict the performance of such a column experimentally observed. This study provides crucial knowledge to understand the behavior of such a column and provides numerical tools for design engineers.

Lagrangian dynamics and regularity of the spin Euler equation

We derive the spin Euler equation for ideal flows by applying the spherical Clebsch mapping. This equation is based on the spin vector, a unit vector field encoding vortex lines, instead of the velocity. The spin Euler equation enables a feasible Lagrangian study of fluid dynamics, as the isosurface of a spin-vector component is a vortex surface and material surface in ideal flows. We establish a non-blowup criterion for the spin Euler equation, suggesting that the Laplacian of the spin vector must diverge if the solution forms a singularity at some finite time. The direct numerical simulations (DNS) of three ideal flows – the vortex knot, the vortex link and the modified Taylor–Green flow – are conducted by solving the spin Euler equation. The evolution of the Lagrangian vortex surface illustrates that the regions with large vorticity are rapidly stretched into spiral sheets. The DNS result exhibits a pronounced double-exponential growth of the maximum norm of Laplacian of the spin vector, showing no evidence of the finite-time singularity formation if the double-exponential growth holds at later times. Moreover, the present criterion with Lagrangian nature appears to be more sensitive than the Beale–Kato–Majda criterion in detecting the flows that are incapable of producing finite-time singularities.

Dual-Scale Spiral Material for Balancing High Load Bearing and Sound Absorption.

Porous materials with sound absorption and load-bearing capabilities are in demand in engineering fields like aviation and rail transportation. However, achieving both properties simultaneously is challenging due to the trade-off between interconnected pores for sound absorption and mechanical strength. Inspired by quilling art, a novel design using spiral material formed by rolling planar materials into helical structures is proposed. Experimental results show high structural strength through self-locking mechanisms, while double porosities from interlayer spiral slits and aligned submillimeter pores provide excellent sound absorption. These spiral sheets surpass foam aluminum in specific strength (up to 5.1MPa) and approach aerogels in sound absorption (average coefficient of 0.93 within 0-6400Hz). With its adaptability to various planar materials, this spiral design allows for hybrid combinations of different materials for multi-functionality, paving the way for designing advanced, lightweight porous materials for broad applications.

Behavior of Square Reinforced Concrete Columns Strengthened by Different Layers of Glass Frp Sheets

The behavior of reinforced square concrete columns strengthened by specific layers of glass fiber reinforced polymer (FRP) sheets were investigated through an experiment by testing of thirteen variety of concrete columns that were axially loaded at their ends. The most variable thought of during this study were the quantity or number of layers of glass fiber reinforcement polymer sheets and also the effect of confinement techniques (fully wrapped, strip ties and spiral sheets). The test values were compared with the proposed equation of ACI 440.2R-02, for samples strengthened by one layer of GFRP sheet can upgrade the load carrying capacity of columns in numerous ways of strengthening (fully wrapped, strip ties and spirally) by 25.5%, 6.7% and 29.5% respectively compared to the control (unstrengthen) column. Be that as a result of it would, for columns strengthen by 2 layers of GFRP sheets (fully wrapped, strip ties and spirally) the load carrying capacity increases by 36.5%, 19.6% and 29.8% respectively. While, for 3 layers of strengthen sample the percent of enhancement in the load carrying capacity increases by 38.2%, 20.1% and 30.7% respectively. Finally, the load carrying capacity increases by 43.2%, 29.2% and 33.2% for different confinement techniques (fully wrapped, strip ties and spiral sheets) respectively if they are strengthened by 4 layers of GFRP sheets.

An improved method of crafting a multi-electrode spiral cuff for the selective stimulation of peripheral nerves

This article reviews an improved methodology and technology for crafting a multi-electrode spiral cuff for the selective activation of nerve fibres in particular superficial regions of a peripheral nerve. The analysis, structural and mechanical properties of the spot welds used for the interconnections between the stimulating electrodes and stainless-steel lead wires are presented. The cuff consisted of 33 platinum electrodes embedded within a self-curling 17-mm-long silicone spiral sheet with a nominal internal diameter of 2.5 mm. The weld was analyzed using scanning electron microscopy and nanohardness tests, while the interconnection was investigated using destructive load tests. The functionality of the cuff was tested in an isolated porcine vagus nerve. The results of the scanning electron microscopy show good alloying and none of the typical welding defects that occur between the wire and the platinum foil. The results of the destructive load tests show that the breaking loads were between 3.22 and 5 N. The results of the nanohardness testing show that the hardness of the weld was different for the particular sites on the weld sample. Finally, the results of the functional testing show that for different stimulation intensities both the compound action potential deflection and the shape are modulated.

In-Plane Anisotropic Thermally Conductive Nanopapers by Drawing Bacterial Cellulose Hydrogels.

We developed flexible polymeric "heat-guiding materials" by simply drawing bacterial cellulose (BC) hydrogels to align the cellulose nanofibers and form "nanopapers" with anisotropic thermal conductivity. The in-plane anisotropy of thermal conductivity between the drawn and transverse directions increased as the draw ratio increased. For the drawn BC nanopapers, the coefficient of thermal expansion was found to be inversely correlated with the thermal diffusivity. We fabricated a planar spiral sheet by assembling the drawn BC strips to visualize the "heat flux controllability". The coexistence of heat-diffusing and heat-insulating capacities within the single nanopaper plane could help to cool future thin electronics.

Supramolecular control of self-assembling terthiophene–peptide conjugates through the amino acid side chain

The self-assembly of oligothiophene-peptide conjugates can be directed through the systematic variation of the peptide sequence into different nanostructures, including flat spicules, nanotubes, spiral sheets, and giant, flat sheets. Furthermore, the assembly of these molecules is not controlled by steric interactions between the amino acid side chains.

Analysis of the three-phase induction motor with spiral sheet rotor

The improvements obtained on the torque with low currents using rotor with spiral sheets are analyzed in this paper. To have a complete study, several rotors and stators have been built to verify the electromagnetic variations on the three-phase asynchronous motors where they combine different constructive and mechanical characteristics of the related elements: changing inertias, constructive materials, and the geometrical shapes and disposition of the sheets. These different types of motors have been first tested in the laboratory, then, are simulated using computer aided tools (Matlab–Simulink). In particular four stators (1000, 1500, 1500-type A, and 3000 rpm) having the same constructive parameters, have been tested with the following rotors: solid rotor, solid rotor with diamagnetic rings, drag cup, and simple and double squirrel cage rotor. All these results have been compared to those obtained with the seven variants of spiral sheet rotor, presented in this paper.

General Analysis of the Three-Phase Asynchronous Motor With Spiral Sheet Rotor: Operation, Parameters, and Characteristic Values

The objectives of this paper arise through the investigation of a motor with a high starting torque, although with limited intensities, weak intensity variations depending on the load, controlled losses in no-load tests, and an acceptable performance in steady state, and with a good response in transient periods. All these requirements would have to be obtained without the help of power electronics; in this way, the motor would be more robust, longer lasting, and without the need for auxiliary equipment. In this paper, the operation principle, the characteristic parameters, and the obtained results for the spiral sheet motor are analyzed for three speed regimes, namely, 1000, 1500, and 3000 r/min. In addition, the spiral sheet motor is compared with the squirrel cage rotor, the solid rotor with rings, the wound rotor with additional resistances in the rotor circuit, and the hollow diamagnetic rotor.

Experimental analysis of the three-phase induction motor with spiral sheet rotor

The objectives of this article arise through the investigation of a motor with a high starting torque although with limited intensities, weak intensity variations depending on the load, controlled losses in no-load tests, an acceptable performance in steady state and with a good response in transient periods. All these requirements would have to be obtained without the help of power electronics, in this way the motor would be more robust, longer lasting and without the need for auxiliary equipment. In this article, the results for the sheet rotor type A are analyzed, and a comparison made with the squirrel cage rotor, the solid rotor with rings and finally with the hollow diamagnetic rotor, all working at 1,500 and 3,000 rpm.

Behavior of the Three-Phase Induction Motor With Spiral Sheet Rotor

Improvements in torque at low currents using a rotor with spiral sheets are analyzed. Several rotors and stators have been built combining different constructive and mechanical characteristics of the related elements: inertias, constructive materials, geometrical shapes of the sheets, and geometrical disposition of the sheets. These different types of motors have been simulated using computer-aided tools and then tested in the laboratory. Finally, four stators (1000, 1500, 1500-type A, and 3000 r/min), with the same constructive parameters, have been simulated and tested with the following rotors types: solid rotor, solid rotor with diamagnetic rings, drag cup, and simple and double squirrel cage rotor; the results have been compared to those obtained with the seven variants of the spiral sheet rotor presented in this paper.

The multi-mode stretched spiral vortex in homogeneous isotropic turbulence

The stretched spiral vortex is identified using direct numerical simulation (DNS) data for homogeneous isotropic turbulence and its properties are studied. Its genesis, growth and annihilation are elucidated, and its role in the generation of turbulence is shown. Aside from the two symmetric modes of configurations with regard to the vorticity alignment along two spiral sheets and the vortex tube in the core region studied in previous works, a third asymmetric mode is found. One of the two symmetric modes and the asymmetric mode are created not by a conventional rolling-up of a single vortex sheet but through the interaction among several sheets. The stagnation flow caused by the two sheets converges to form recirculating flow through its interaction with the vortex along the third sheet. This recirculating flow strains and stretches the sheets. The vortex tube is formed by axial straining, lowering of pressure and the intensification of the swirling motion in the recirculating region. As a result of the differential rotation induced by the tube and that self-induced by the sheet, the vortex sheets are entrained by the tube and form spiral turns. The transition between the three modes is examined. The initial configuration is in one of two symmetric modes, but it is transformed into another set of two modes due to the occurrence of reorientation in the vorticity direction along the stretched sheets. The symmetric mode tends to be more persistent than the asymmetric mode, among the two transformed modes. The tightening of the spiral turns of the spiral sheets produces a cascade of velocity fluctuations to smaller scales and generates a strongly intermittent dissipation field. To precisely capture the spiral turns, a grid resolution with at least $k_{\rm max} \overline{\eta} \,{\approx}\, 4.0$ (kmax is the largest wavenumber, $\overline{\eta}$ is the averaged Kolmogorov scale) is required. At a higher Reynolds number, self-similar spiral vortices are successively produced by the instability cascade along the stretched vortex sheets. A cluster consisting of spiral vortices with an extensive range of length scales is formed and this cluster induces an energy cascade.

Lactic Acid Production from Cheese Whey by Immobilized Bacteria

The performance of immobilized Bifidobacterium longum in sodium alginate beads and on a spiral-sheet bioreactor for the production of lactic acid from cheese whey was evaluated. Lactose utilization and lactic acid yield of B. longum were compared with those of Lactobacillus helveticus. B. longum immobilized in sodium alginate beads showed better performance in lactose utilization and lactic acid yield than L. helveticus. In the spiral-sheet bioreactor, a lactose conversion ratio of 79% and lactic acid yield of 0.84 g of lactic acid/g of lactose utilized were obtained during the first run with the immobilized L. helveticus. A lactose conversion ratio of 69% and lactic acid yield of 0.51 g of lactic acid/g of lactose utilized were obtained during the first run with immobilized B. longum in the spiral-sheet bioreactor. In producing lactic acid L. helveticus performed better when using the Spiral Sheet Bioreactor and B. longum showed better performance with gel bead immobilization. Because B. longum is a very promising new bacterium for lactic acid production from cheese whey, its optimum fermentation conditions such as pH and metabolic pathway need to be studied further. The ultrafiltration tests have shown that 94% of the cell and cheese whey proteins were retained by membranes with a mol wt cutoff of 5 and 20 KDa.

Isolation and characterization of an unusual bacterium, allied to the soil bacteriumBacillus benzoevorans,from feedlot manure pads in Australia

Strains of bacteria were obtained by anaerobic enrichment from feedlot manure pads and were phenotypically characterized. Colonies had a cotton wool or hairy appearance. When cultures grown in liquid media were exposed to a drying atmosphere, they produced a pellicle comprised of a cross-meshed array of cells. Colonies on agar media also produced spiral sheets of cells held well above the agar surface. The strains were Gram positive, according to ultrastructural features from transmission electron micrographs and KOH solubility, but Gram negative by Gram stain. The 16S rDNA from strain YEO5 was determined and is 99·3% similar to the type strain of Bacillus benzoevorans. The inability of our strains to grow aerobically and lack of endospores differentiated them from previously isolated strains of B. benzoevorans. In freshly broken feedlot pad material, a white, hairy coating of the exposed surface appeared within a few hours. We hypothesize that this is due to the insoluble extracellular matrix material produced by this Bacillus sp. to avoid desiccation and, additionally, the bacterial covering is responsible for retaining odours within the pad material.

Magnetic field analysis of coupling transformers for electric vehicle using 3-D finite element method

The 3-D analysis is useful for the optimum design of high frequency coupling transformers which have complex structures. It is difficult to predict the current distributions taking into account eddy currents in sheet coils. In this paper, the current density vector analysis and the magnetic field analysis taking into account eddy currents in the spiral sheet coils are coupled. The exciting current characteristics and copper loss are calculated by our method. It is shown that the load characteristics can be accurately calculated by comparison with measurements. The copper loss distributions taking into account eddy currents in the coils are also shown quantitatively.

Comment on ‘‘Is intermittent motion of outer flow in the turbulent boundary layer deterministic chaos?’’ [Phys. Fluids A 3, 1941 (1991)

Recently, Tsuji et al. [Phys. Fluids A 3, 1941 (1991)] presented measurements of the probability density of sizes of laminar regions in the upper portion of a turbulent boundary layer. This size distribution was shown to have a power-law decay exponent close to −4/3, and it was shown that certain one-dimensional chaotic maps have the same property. Here, it is argued that the experimental observations can also be explained by two different paradigms for the interface separating turbulent from irrotational fluid. The first is that of a globally self-similar fractal surface of Hausdorff dimension DH=7/3. The second is that of a power-law spiral sheet with a box dimension of the same value. Both are consistent with other experimental evidence to date, as well as with the Kolmogorov scaling of turbulent velocity fluctuations.

Outer acrosomal membrane of guinea pig spermatozoa: isolation and structural characterization.

We describe a protocol to isolate a highly enriched fraction of outer acrosomal membrane from guinea pig spermatozoa and present new data on the ultrastructure of this membrane domain. Cauda epididymal spermatozoa were suspended into a low ionic strength buffer and subjected to brief homogenization; this stripped the plasma membrane from the spermatozoa and severed the acrosomal apical segment from the spermatozoon. The crescent-shaped apical segments retained the outer acrosomal membrane and specific components of the acrosomal matrix. Enriched fractions of apical segments were isolated on discontinuous sucrose gradients and the outer acrosomal membrane purified by subsequent centrifugation onto Percoll density gradients. The isolated outer acrosomal membrane did not form vesicles, but instead rolled up into spiral sheets. Both thin section and negatively stained specimens revealed a paracrystalline arrangement of filaments associated with the luminal surface of the membrane. The isolated outer acrosomal membrane revealed a limited number of polypeptides by SDS-PAGE, and the polypeptide pattern was distinct from the plasma membrane fraction. The isolated acrosomal membranes possessed no ouabain sensitive Na+,K+-ATPase activity, whereas about 20% of the ATPase activity of the plasma membrane enriched fraction was inhibited by ouabain. The potential function of the structural differentiations of the outer acrosomal membrane in the membrane fusion events of the acrosome reaction is discussed.

Inviscid evolution of stretched vortex arrays

The nonlinear evolution of an array of pairs of inviscid counter-rotating vortices, subjected to an applied stretching strain field, has been studied numerically using the contour-dynamics method. The array configuration is effectively the Corcos-Lin model of streamwise vortices in the braid region of a nominally two-dimensional mixing layer. For each individual vortex the simulations elucidate the strong interaction between the vortex self-induction, the vorticity amplification of the stretching strain, and the local in-plane strain applied by all other members of the array. When the initial vorticity distribution is modelled by a non-uniform piece-wise-constant vorticity field defined over a nested set of non-intersecting contours, the dynamical evolution reveals fine structure consisting of strong vortex roll-up accompanied by trailing, filament-like spiral vortex sheets, and the presence of tertiary instabilities. It is shown by a particular example that these features are largely absent in an equivalent computation in which array members are modelled by the commonly used uniform-vortex approximation.

Calculation of heat exchange in pipes with spiral sheet intensifiers

A method of calculating the heat exchange in pipes with spiral sheet intensifiers is developed on the basis of a superposition of the effects of the separation and swirled motions of streams.

On the importance of advection in determining the local isotopic composition of the mantle

The equations for isotopic evolution in a deforming medium are derived and used to show that the local isotopic composition of the mantle depends primarily on the advection of heterogeneities by the flow field. Various examples of the role of advection are given using a two-scale model of mantle convection. The effect of small-scale flows, which have dimensions smaller than the plates themselves, is to convert any initially localized heterogeneity into thin spiral sheets. The isotopic properties of erupted lavas will depend on the relative size of the zone of partial melt to the spacing between such sheets. An idealized model for 87Sr/ 86Sr variations from Pacific islands and the covariation of 143Nd/ 144Nd- 87Sr/ 86Sr is based on the combined effect of isotopic fluxes at subduction zones and advection by the return flow under the moving lithospheric plates.