Spiral Surface Research Articles

On-chip centrifuge using spiral surface acoustic waves on a ZnO/glass substrate

On-chip centrifuges based on acoustic methods have promising applications in biomedicine, environmental protection, and food testing. Glass materials are ideal for microfluidics because of their low cost, chemical inertness, thermal stability, and excellent optical transmission. This paper demonstrates a glass-based, efficient, and controllable particle centrifuge. A circular interdigital transducer with spiral electrodes was fabricated on a composite substrate of ZnO film and quartz glass (QG), generating an omnidirectional spiral surface acoustic wave field. A vorticity field was generated in a sessile droplet, and controlled concentrations of polystyrene particles with different diameters and Hela cells in the droplet were achieved. A linear relationship was observed between the driving voltage and the field amplitude, and in turn, between the voltage and the streaming velocity. The performance of the device can be improved by tuning the driving voltage or the recipe of the solvent. The ZnO/QG-based centrifuge shows good performance in enriching micron/submicron particles and cells and is compatible with optical tools, offering good promise in enriching low abundance micro- and nanoparticles, especially in rare samples.

A direct preset method for solving ease-off tooth surface of spiral bevel gear

In order to realize the global integrated control of spiral bevel gear tooth surface, this paper presents a direct preset method for solving ease-off tooth surface of spiral bevel gear. This method integrates the preset contact path (CP), geometric transmission error (TE) and curvature of difference curve at the contact point (CDC), which is called CPTE-CDC. Based on the relationship between ease-off and tooth surface planning grid, CPTE-CDC is used to establish a nonlinear overdetermined equations to solve ease-off surface equation. According to the ease-off surface obtained from the solution, the ease-off target tooth surface of pinion related to cuttting parameters is established, and its optimal machining parameters are solved based on Levenberg–Marquardt (LM) algorithm. Finally, a numerical example is created using TCA and LTCA techniques. The results show that the tooth surface obtained by CPTE-CDC method not only meets the preset contact characteristics, but also meets the design requirements, which proves the correctness of the proposed method. CPTE-CDC method can be used as a theoretical basis for improving the global control of spiral bevel gear tooth surface.

Periodic Spiral Ripples on VS2 Flakes: A Tip-Enhanced Raman Investigation.

Using atmospheric-pressure chemical vapor deposition, we have synthesized vanadium disulfide (VS2) flakes with a metallic 1T phase that display nanoscale spiral surface ripples. To understand the origin of these chiral patterns in these transition metal dichalcogenides, tip-enhanced Raman spectroscopy and Kelvin probe force microscopies were jointly used to investigate their crystal structure, possible oxidation, and electronic properties, respectively. We found that the surface corrugation consists of small crystalline domains with distinct orientations. The change in local orientation is observed concomitantly with a spectral shift of the lattice modes of VS2 and results in the formation of grain boundaries between the domains with distinct orientation. Additionally, the periodic surface structure is modulating the work function of VS2 by 14 meV.

Stability Analysis of Pile-Supported Embankments over Soft Clay Considering Soil Failure between Piles Based on Upper Bound Theorem

Most analytical methods used to analyze the stability of pile-supported embankments are based on shear and bending failure of piles. However, the centrifuge test and practical engineering show that rigid pile-supported embankments have a failure mode of soil sliding around piles. Therefore, the stability analysis method of the pile-supported embankment under the failure mode of the soil sliding around piles based on the upper bound theorem is given in this study. First, the failure mechanism is assumed to be a rigid body and slide along two logarithmic spiral surfaces in the embankment and soft soil. The rate of external work and internal energy dissipation of the failure mechanism are further obtained, wherein the internal energy dissipation rate of piles is obtained based on the limit state of soil sliding around piles. Secondly, according to the equation formed by the upper bound theorem, the optimization model of the safety factor function when the potential slip surface is passing through different pile rows is obtained. Then, the algorithm of solving the model is given and the overall safety factor of the pile-supported embankment is obtained. Compared with other methods, the advantage of this method is that it considers the influence of embankment soil property and the width perpendicular to the two-dimensional plane on the pile load and the influence of the soil internal friction angle on the slip surface. Finally, it can be concluded from parametric analysis that: with the increase of the horizontal distance from piles to the slope toe, the reinforcement effect of piles first increases and then decreases; with the decrease of the embankment height and the increase of the soft soil cohesion and internal friction angle, the overall safety factor of the embankment increases.

Experimental and numerical investigation of flow over spiral grooved cylinders

This study experimentally and numerically investigates the performance of a circular cylinder with a spiral grooved surface in terms of reducing wind drag. Its application in the overhead high-power conductor plays a vital role, especially in typhoon conditions. Wind tunnel tests have shown that at the critical Reynolds number (Re), the coefficients of wind drag decrease to a greater extent in a spiral grooved cylinder than in a smooth circular one. Moreover, a cylinder with a shallow groove and a small number of spirals could reduce the coefficient of drag in typhoon conditions. To gain an insight into the underlying fluid mechanism, a large-eddy simulation of turbulent flow from a critical to a super-critical Re has been carried out to approximate the flow separation and turbulent eddies over the spiral grooved cylinder. The results of the wind tunnel test have been used as a benchmark for the numerical results. The flow characteristics have been established about the near-wall flow separation and far wake flow, the pressure coefficient, the skin-friction coefficient, drag coefficient, and Q-criterion field.

Optimization of high-efficiency tooth surface accuracy of spiral bevel gears considering machine-tool motion errors

With the continuous improvement of the requirements of spiral bevel gear transmission for low noise and high precision, the optimization of high-efficiency tooth surface accuracy considering the motion axis error of machining machine tool has become a key point in the process of designing and manufacturing spiral bevel gear. Based on the theory of the multi-body dynamics system and the principle of gear meshing, a new tooth surface error model of spiral bevel gear considering the error of machine-tool moving axis is proposed and optimized, so as to obtain higher tooth surface accuracy and meshing efficiency. Firstly, according to the motion and machining principle of spiral bevel gear NC grinding machine, the corresponding relationship between the motion error of each axis of the NC gear grinding machine and the variation of cutting parameters of spiral bevel gear is analyzed, and the geometric motion error model of spiral bevel gear grinding machine is given; secondly, the tooth surface equation of the spiral bevel gear considering the machine-tool motion axis error is established; then, in view of Powell's dog leg optimization algorithm, the tooth surface considering the motion axis error of the machine tool is optimized, and the optimal cutting parameters of spiral bevel gear tooth surface machining are obtained. Finally, the simulation results show that the difference between the peak and peak values of transmission error and the maximum contact stress of the tooth surface is reduced by 72.6% and 1.62%, respectively, and the meshing efficiency is improved from 0.9798 to 0.9803 after optimization; by comparing the rolling experiment and simulation results, the maximum error between the quantitative parameters of the two groups of tooth surface contact marks is no more than 9%, which verifies the effectiveness and feasibility of this method, and provides a certain theoretical basis for practical production and processing.

Experiments on three-dimensional flaw dynamic evolution of transparent rock-like material under osmotic pressure

The dynamic evolution mechanism of intrinsic crack propagation in rocks is a topical and difficult problem in rock mechanics and engineering. Numerous examples of rock mass engineering disasters indicate that the three-dimensional (3D) flaw propagation and evolution process are the internal factors causing geological disasters. A persistent puzzle is the effect of osmotic pressure on the spatial form of crack propagation in compressed rock mass. As the naked eye cannot observe the dynamic evolution process of internal natural crack propagation, we experimented with transparent specimens that have brittle fracture properties similar to those of a rock-like material under frozen conditions. We prefabricated elliptical open cracks in the specimens, on which were applied osmotic pressure through a high-pressure osmotic injection equipment. Through uniaxial and biaxial compression tests, we established a set of compression test steps and methods for intrinsic open-type prefabricated crack specimens under osmotic pressure. Further, we analyzed and compared with the dynamic evolution law of the entire stress–strain process of 3D flaw under osmotic pressure, exploring the effects of different osmotic pressures and crack forms on the crack initiation, penetration, and peak strengths of elliptical open-type cracks. Consequently, the fan-shaped and spiral surface cracks formed by 3D flaw propagation were found for the first time without osmotic pressure. Meanwhile, osmotic pressure accelerated the growth of wrapping wing cracks and inhibited the growth of petal cracks and wrapping anti-wing cracks. Lateral pressure suppressed the vertical propagation of the wing cracks, increased the crack stress and peak strength, and reduced the initial propagation angle of the wing cracks at the long axis end of the prefabricated crack. These findings provide an important basis for expanding the initiation, propagation, evolution, and failure mechanism of 3D flaw under osmotic pressure in natural rock mass.

Numerical study on mixed thermal-elastohydrodynamic lubrication of grease lubricating lubricated spiral bevel gear for heavy-duty unmanned aerial vehicle

Aiming to solve the problem of the gear lubrication of unmanned aerial vehicles (UVAs), a grease mixed Thermal-elastohydrodynamic lubrication (TEHL) model is established, and the lubrication state of the gearbox of oil-powered heavy-duty UAVs is numerically analyzed. In this study, grease is regarded as a non-Newtonian fluid whose properties change nonlinearly with respect to pressure, temperature, and other conditions. The complex meshing state of a spiral bevel gear tooth surface is analyzed using the loaded tooth contact analysis (LTCA) method, and three points on the tooth surface are selected as samples to describe the lubrication state of the entire tooth surface. The thickness of grease film and the temperature rise of the tooth surface are studied in detail, considering the natural roughness of the tooth surface and influence of different greases. The results show that the established model agrees with results from the literature. The dangerous point of tooth surface lubrication is at the meshing midpoint. Under cruise conditions, the lubricating grease viscosity significantly influences the temperature rise of the tooth surface.

Experimental analysis of water and slurry flows in gravity-driven helical mineral separators

This paper aims to provide essential information of the water and slurry flow behaviour in a popular full-scale mineral separation spiral. Besides critical measurements of the free surfaces, the wall roughness and wall contact angle, novel measurements and assessment of the commonly encountered ‘bubble line’ are provided herein. The free surface shapes of three flows: water-only, chromite slurry and magnetite slurry are compared for the first time, which highlights operational spiral phenomena. The research provides insight into the mechanics behind the ‘wetting-in’ process by showing that this process affects the wall contact angle more than the surface roughness. The most representative roughness height of the spiral trough was found to be 138.4 μm and the wall contact angle of the spiral surface was 88.14°, measured in the water phase. The experiments showed that the free surface shape and the position and width of the bubble line in a water-only flow reached a steady state after 1.25 spiral turns. The results and findings are applicable to spirals of other makes and models and can validate future spiral fluid flow simulations.

Molecularly imprinted polymer enhances affinity and stability over conventional aptasensor for blood clotting biomarker detection on regimented carbon nanohorn and gold nanourchin hybrid layers

This study aims to develop a rapid and sensitive biomimetic biosensor for the early detection of bleeding disorders by sensing human blood clotting factor IX protein (FIX). Authors used a dual sensitive detection strategy to identify FIX deficiency in human plasma, by incorporating aptamer recognition mechanism with molecular imprinted polymer (MIP) technology. Amino-modified truncated 2′ fluoro-RNA aptamer was used as macro-monomer in MIP synthesis. Produced MIP nanoparticles were immobilized through carbodiimide on Archimedean spiral interdigitated electrode surface for the electrical detection. The sensitivity was enhanced by surface modification using carbon nanohorn and gold nanourchin. Incorporating these hybrid materials and MIP, the enhanced FIX sensor sensitivity was at 6.06E-6 µA fM−1 µm−2. It was found that MIP incorporated sensor has 3-folds enhanced sensitivity with 40 fM detection limit compared to the conventional aptasensor. Validations have been given by sensing FIX level from human plasma serum with 10.7 pM sensitivity and by enzyme-linked apta-sorbent assay at 8 pM as a sensitivity. Moreover, the specificity of sensor also has proven with discrimination of the analogues. This research produced a novel biosensor for FIX detection and justifies that aptamer embedded MIP plays a crucial role for high-performance protein recognition in bleeding diathesis.

Development of deeply focused microwave lens applicator for efficient hyperthermia treatment

In this paper, a deeply focused microwave lens applicator is investigated for hyperthermia treatment. The lens applicator consists of a double spiral antenna (DSA) and frequency selective surface (FSS) as superstrate. The double spiral structure is designed on the top of the upper substrate (Substrate-1), the slotted ground plane is placed between the upper and lower substrate (Substrate-2), and the microstrip feed line is printed on the bottom of the lower substrate. The overall size of the proposed antenna is 32 × 32 × 3.27 mm3. Moreover, an FSS structure (as superstrate) is designed, which has a size of 64 × 64 mm2 (consists of a 4 × 4 unit cell). The FSS structure behaves as a lens that converts the bidirectional field pattern of DSA into the unidirectional pattern, which improves the focusing ability of the proposed applicator towards the phantom. The lens applicator is simulated with heterogeneous phantom (layers of skin, fat, and muscles), and the performance of the applicator is evaluated in terms of specific absorption rate (SAR), penetration depth (PD), and effective field size (EFS). The lens applicator is fabricated and experimentally validated in the presence of an artificial phantom. The measured results are in close agreement with the simulated one. Further, the performance of the applicator is analyzed for a deeply placed irregular-shaped tumor (at 15 mm from the skin surface). The study of temperature distribution is done, and the peak value of temperature is obtained as 43 °C with 2.5 W of microwave power given to the antenna. The temperature value around the tumor is obtained in the range of 41–45 °C, which is suitable for effective hyperthermia treatment.

Conversion of a Helical Surface Plasmon Polariton into a Spiral Surface Plasmon Polariton at the Outlet of a Metallic Nanohole.

The conversion of a helical surface plasmon polariton (SPP) creeping out of a circular nanohole in a thick metal (Ag or Au) film into a spiral (Hankel type) SPP outward propagating at the film’s interface is studied theoretically. The dispersion relations of SPPs of various modes in a nanohole, calculated from a transcendental equation, show that the propagation length of an SPP of mode 1 is much larger than the other modes in a specific frequency band, which is dependent on the nanohole size. In this band, the streamlines of the Poynting vector (energy flux) of mode-1 SPP in nanohole exhibit helixes; the surface component of the energy flux is perpendicular to the phase front of the SPP. Numerical results show that, after a helical SPP tunnels through a nanohole, most of the energy flux fans out at the outlet as a dipole radiation. The spatial phase distribution of Ez above the interface indicates that the transmission light carries orbital angular momentum with a topological charge of 1. Additionally, a part of the helical SPP creeping along the edge of an outlet naturally converts into a spiral (Hankel type of order 1) SPP outward propagating at the film’s interface; both SPPs have the same handedness. Moreover, the interferences of multi SPPs generating from two nanoholes and even from a two-dimensional nanohole array are also related to the spiral SPP.

A topological flank modification method based on contact trace evaluated genetic algorithm in continuous generating grinding

A method for topological modification of gear flanks in continuous generating grinding based on contact trace evaluated genetic algorithm (CTEGA) has been proposed to solve the problem of flank twist caused by lead modifications of gear flanks. Firstly, according to the theory of conjugate surface, a mathematical model calculating the generating surfaces of worm wheel as well as representing the wheel as two-parametric form spiral surface has been established. Secondly, by representing the radial, axial, and tangential feed of worm wheel in forms of polynomials of the axial feed of worm wheel, a mathematical model of generating gear grinding process has been established where the axis linkage relationship in CNC machine is intentionally changed for topological modification of target tooth surface. Finally, the validity of the proposed topological modification method was numerically demonstrated using a helical gear made by the CNC continuous generating grinding machine. The method proposed in this paper can realize the topological modification of gear flanks by only adjusting motions of numerically controlled axes in the grinding process without adopting a specific dressing of the grinding wheel.

Load-dependent stiffness model and experimental validation of four-station rotary tool holder

The four-station rotary tool holder is used to clamp multiple turning tools and realize automatic tool change on a lathe. For the accurate estimation of structural stiffness, a deeper understanding of mechanical behavior within locking tool holder is needed. This paper is the first attempt to introduce a theoretical vertical stiffness model of tool holder. The rough surface joint effect is characterized by fractal geometry theory, including lower-upper tool holder plane joint, gear plate joint with trapezoidal tooth, screw spiral surface joint. The interface base bulk stiffness and the support bearing deformation are also unified in the stiffness modeling. Through the force interaction, the nonlinear relationship of load–displacement is established. The bidirectional static loading test under various locking forces is conducted using a commercial tool holder. The different intercepts of load-dependent displacement curve for various preloads are experimentally captured. The vertical stiffness under compression load is higher than that under tensile load. The predicted values agree well with experimental results by the micro-topography characterization of surface joints. The numerical simulation shows that vertical stiffness increases with the increase of compression load, locking force, fractal parameter D, nominal area of surface joints, and the decrease of dragged load, fractal parameter G.

Characteristic parameterizations of surfaces with a constant ratio of principal curvatures

Motivated by applications in architectural geometry, we study and compute surfaces with a constant ratio of principal curvatures (CRPC surfaces) based on their characteristic parameterizations. For negative Gaussian curvature K, these parameterizations are asymptotic. For positive K they are conjugate and symmetric with respect to the principal curvature directions. CRPC surfaces are described by characteristic parameterizations whose parameter lines form a constant angle. We use them to derive characteristic parameterizations of rotational CRPC surfaces in a simple geometric way. Pairs of such surfaces with principal curvature ratio κ1/κ2=±a can be seen as equilibrium shapes and reciprocal force diagrams of each other. We then introduce discrete CRPC surfaces, expressed via discrete isogonal characteristic nets, and show how to efficiently compute them through numerical optimization. In particular, we derive discrete helical and spiral CRPC surfaces. We provide various ways how these and other special types of CRPC surfaces can serve as a basis for computational design of more general CRPC surfaces. Our computational tools may also serve as an experimental basis for mathematical studies of the largely unexplored class of CRPC surfaces.

Theoretical model analysis and case simulation of spherical involute surface

The theoretical model of a spherical involute surface is the premise and foundation of the 3D modelling design technology of spiral bevel gear. The forming process of the surface is also the forming process of its mathematical model. Based on the generating principle of spherical involute on cone and surface analysis, the system model is gradually divided into blocks from curve to surface, and the surface of the bevel gear is obtained by parameter coupling. The modelling process of curve, surface or initial spiral can be independently referenced. It can realise the precise modelling of complex spiral profile surfaces such as variable spiral angles. In this paper, the mathematical model of spiral bevel gear was simulated and analysed on the MATLAB2019b platform. The simulation results verified the correctness of the algorithm of the spiral bevel gear model and the practicability of design optimisation.

Spiral structure of the galactic disk and its influence on the rotational velocity curve

AbstractMost spiral galaxies have a flat rotational velocity curve, according to the different observational techniques used in several wavelengths domain. In this work, we show that nonlinear terms are able to balance the dispersive effect of the wave, thus reviving the observed rotational curve profiles without the inclusion of any other but baryonic matter concentrated in the bulge and disk. To prove that the considered model is able to restore a flat rotational curve, Milky Way has been chosen as the best‐mapped galaxy, to apply on. Using the gravitational N‐body simulations with up to particles, we test this dynamical model in the case of the Milky Way with two different approaches. Within the direct approach, as an input condition in the simulation runs, we set the spiral surface density distribution which is previously obtained as an explicit solution to nonlinear Schrödinger equation (instead of a widely used exponential disk approximation). In the evolutionary approach, we initialize the runs with different initial mass and rotational velocity distributions, in order to capture the natural formation of spiral arms and to determine their role in the disk evolution. In both cases, we are able to reproduce the stable and nonexpanding disk structures at the simulation end times of years, with no halo inclusion. Although the given model does not take into account the velocity dispersion of stars and finite disk thickness, the results presented here still imply that nonlinear effects can significantly alter the amount of dark matter which is required to keep the galactic disk in a stable configuration.

Flow analysis in seamless hot-extruded pipes with helical inner ribbing surface

The article is devoted to numerical simulation of heat transfer processes occurring during the flow of a coolant in seamless hot-extrusion pipes with a spiral inner fin surface (TMK-IRS). A description of the numerical modeling technique is given along with the interface of the program used to create different types of internal fins. Thermohydraulic analysis of finned pipes for transient, turbulent and laminar flow regimes has been carried out. An estimate of the critical Reynolds number characterizing the transition to a turbulent regime, the nature of the transient flow regime in comparison with other classical cases is given.

Modified pseudo-dynamic analysis of slope considering logarithmic spiral failure surface with numerical solution

ABSTRACT A methodology for the analysis of soil slope made up of c-ϕ soil using a modified pseudo-dynamic approach is tried to develop here. In this study, the slope is divided into a number of vertical slices and the failure surface of the slope is assumed to be logarithmic spiral. The suggested modified pseudo-dynamic approach satisfies the zero-stress boundary condition at the free ground surface and considers the damping properties of the materials. Results of the present analysis are presented in tabular form. The effects of the variation of different parameters like horizontal and vertical seismic acceleration, slope angle, soil friction angle, damping ratio, frequency ratio, cohesion and surcharge on the FOS are shown graphically. Consequently, required reinforcement strength is evaluated to ensure the safety of the slope under seismic loading conditions. The results obtained from the present method are compared with the results of the available literature and also a numerical validation of the model is given using PLAXIS 2D.

Integrated roughing, finishing and chamfering turning process of toroidal worm manufacture on a general CNC lathe

The toroidal worm drives are widely used in heavy-duty transmission systems, such as the solar tracker. However, the existing manufacturing methods cannot meet the mass manufacture of toroidal worms and lack flexibility, which prevents the popularization and application of toroidal worm drives. Hence, this paper presented an integrated roughing, finishing and chamfering turning method for any type of toroidal worm manufacturing on a general CNC lathe. Firstly, CL (cutter location) data of flexible rough turning of the toroidal worm were calculated according to the internal profile on the symmetry shaft section of the enveloped gear tooth. The top circle, root circle, dual internal tooth profile, and the tool parameters were included to ensure the uniformity of rough turning CL data. Secondly, the grid data matrix of the tooth surface was constructed based on accurate spiral surfaces of the toroidal worm. Spatial discrete points were converted to polar coordinates and were projected to the symmetry shaft section by a rotational matrix to calculate the finish turning CL data. Thirdly, the intersecting line between the spiral tooth surface and the outline surface of a semi-finished product was iteratively calculated. The characteristic curve of chamfering was defined and subdivided on the symmetry shaft section. Then the CL data of chamfering were obtained by connecting the sequential and biased chamfering discrete points. At last, the NC roughing, finishing, and chamfering turning codes were generated with the taper thread turning instruction and the CL data of different stages. Simulation and experiment have been conducted on a general CNC lathe, the results show that the integrated method is effective and applicable in automatic toroidal worm turning. The method proposed in this paper can greatly improve the manufacturing efficiency of any type of hourglass worm, without a special four-axis linkage machine tool.