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Journal articles on the topic 'Spiral'

Author: Grafiati

Published: 4 June 2021

Last updated: 25 July 2025

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1

Pan, Hongjun. "Introduction of New Spiral Formulas from ROTASE Model and Application to Natural Spiral Objects." Academic Journal of Applied Mathematical Sciences, no. 72 (February 5, 2021): 66–76. http://dx.doi.org/10.32861/ajams.72.66.76.

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A new set of spiral formulas is introduced as a new member of the spiral formulas’ family, people with interest in mathematics and natural spirals may use the new spiral formulas to simulate natural spiral objects or generate their own spirals. The new formulas are derived from a proposed new hypothesis called Rotating Two Arm Sprinkler Emission model (ROTASE) for the formation of spiral galaxies. In this paper, the derivation of the new spiral formulas is illustrated with boats moving across a circular river from central round island. The formulas have only one parameter and one variable, the

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Tamura, Kenichi, and Keiichiro Yasuda. "Spiral Dynamics Inspired Optimization." Journal of Advanced Computational Intelligence and Intelligent Informatics 15, no. 8 (2011): 1116–22. http://dx.doi.org/10.20965/jaciii.2011.p1116.

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We recently proposed a new multipoint search method for 2-dimensional continuous optimization problems based on an analogy of spiral phenomena called 2-dimensional spiral optimization. Focused spiral phenomena, which appear frequently in nature, are approximated to logarithmic spirals. Two-dimensional spiral optimization used a feature of logarithmic spirals. In this paper, we proposen-dimensional spiral optimization by extending the 2-dimensional one. The n-dimensional spiral model is constructed based on rotation matrices defined inn-dimensional space. Simulation results for different benchm

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Zhu, Zhaohuan, and Raymond M. Zhang. "A simple time-dependent method for calculating spirals: applications to eccentric planets in protoplanetary discs." Monthly Notices of the Royal Astronomical Society 510, no. 3 (2021): 3986–99. http://dx.doi.org/10.1093/mnras/stab3641.

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ABSTRACT Spirals in protoplanetary discs have been used to locate the potential planet in discs. Since only the spiral shape from a circularly orbiting perturber is known, most previous works assume that the planet is in a circular orbit. We develop a simple semi-analytical method to calculate the shape of the spirals launched by an eccentric planet. We assume that the planet emits wavelets during its orbit, and the wave fronts of these propagating wavelets form the spirals. The resulting spiral shape from this simple method agrees with numerical simulations exceptionally well. The spirals exc

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Bidnichenko, Helen. "FEATURES OF THE GEOMETRY OF SPIRALS AND THEIR NATURAL AND PRACTICAL APPLICATION." APPLIED GEOMETRY AND ENGINEERING GRAPHICS, no. 107 (February 26, 2025): 3–20. https://doi.org/10.32347/0131-579x.2024.107.3-20.

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This work is devoted to the topical issue of geometric modeling of some types of spirals and their practical application in nature and various areas of human activity. A geometric and practical study of Archimedes' spiral and its inversion with respect to the pole - a hyperbolic spiral, as well as Fermat's spiral and its inversion on a circle of unit radius - lituus, was carried out. A mathematical description of spirals is presented and their geometric models are developed: definitions and equations in polar coordinates are provided, graphic formation schemes and algorithms for their construc

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Pan, Hongjun. "Special Spirals are Produced by the ROTASE Galactic Spiral Equations with the Sequential Prime Numbers." Academic Journal of Applied Mathematical Sciences, no. 84 (August 25, 2022): 69–77. http://dx.doi.org/10.32861/ajams.84.69.77.

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In this paper, the sequential prime numbers are used as variables for the galactic spiral equations which were developed from the ROTASE model. Special spiral patterns are produced when prime numbers are treated with the unit of radian. The special spiral patterns produced with the first 1000 prime numbers have 20 spirals arranged in two groups. The two groups have perfect central symmetry with each other and are separated with two spiral gaps. The special spiral pattern produced with natural numbers from 1 to 7919 shows 6 spirals in the central area and 44 spirals in the outer area. The whole

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6

Broerse, Jack, Peter Dodwell, and Boris Crassini. "Anomalous Spiral Aftereffects: A New Twist to the Perception of Rotating Spirals." Perception 21, no. 2 (1992): 195–99. http://dx.doi.org/10.1068/p210195.

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Stationary spirals viewed after inspecting rotating sectored disks appear to rotate and to expand or contract radially, even though the rotating disks contain no perceptible components of radial motion. Moreover, the relative directions of illusory rotation and radial motion observed in these instances are ‘impossible’ under the stimulus constraints normally imposed by the geometry of a spiral under rotation: the stationary spirals appeared to expand/contract in directions opposite to those normally observed under conditions of actual spiral rotation, and under conditions of illusory spiral ro

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Pişmiş, Paris, and Edmundo Moreno. "Formation of Bi-Polar Spiral Features in Galactic Nuclei." Symposium - International Astronomical Union 134 (1989): 488–89. http://dx.doi.org/10.1017/s0074180900141774.

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In earlier communications we have called attention to the existence of very tight spiral formations in the nuclei of some galaxies, particularly of the early type barred spirals, proposing a mechanism for their formation (Pişmiş and Moreno 1984). These kiloparsec-scale structures are loosely termed “rings” but their overall morphology suggests strongly that the image is a tightly wound double spiral usually delineated by knots of emitting material, “hot-spots”. A striking characteristic of these spirals is their very high luminosity compared to the outer regions of the galaxy. 26 galaxies with

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8

Fakih, Ali, Frederic Cordier, and Yvan Maillot. "Piecewise Reconstruction of 3D Euler Spirals From Planar Polygonal Curves." International Journal of Computer Science, Engineering and Information Technology 13, no. 5 (2023): 01–19. http://dx.doi.org/10.5121/ijcseit.2023.13501.

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In this article, we propose a method for reconstructing approximate piecewise 3D Euler spirals from planar polygonal curves. The method computes the 3D coordinates of approximate Euler spiral such that its orthogonal projection onto the 2D plane is the closest possible to the input curve. To achieve this, a dataset is created, comprising Euler spiral segments and their orthogonal projections. Given an input curve, it is sampled and split into segments. Each segment is matched with the closest Euler spiral segments from the dataset, forming a pool of candidates. The optimal set of connected Eul

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9

Zhou, Yuxuan, Yajuan Li, and Chongyang Deng. "G2 Hermite Interpolation by Segmented Spirals." Mathematics 10, no. 24 (2022): 4757. http://dx.doi.org/10.3390/math10244757.

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A curve with single-signed, monotonically increasing or decreasing curvatures is referred to as a planar spiral. G2 Hermite data are spiral G2 Hermite data for which only interpolation by a spiral is possible. In this study, we design segmented spirals to geometrically interpolate arbitrary C-shaped G2 Hermite data. To separate the data into two or three spiral data sets, we add one or two new points, related tangent vectors and curvatures. We provide different approaches in accordance with the various locations of the external homothetic centers of two end-curvature circles. We then match new

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10

Sturm, J. A., G. P. Rosotti, and C. Dominik. "Dust dynamics in planet-driven spirals." Astronomy & Astrophysics 643 (November 2020): A92. http://dx.doi.org/10.1051/0004-6361/202038919.

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Context. Protoplanetary disks are known to host spiral features that are observed in scattered light, the ALMA continuum, and more recently in CO gas emission and gas dynamics. However, it is unknown whether spirals in gas and dust trace the same morphology. Aims. We aim to study the morphology and amplitude of dusty spirals as function of the Stokes number and the underlying mechanisms that cause a difference between dusty spirals and gas spirals. We then construct a model to relate the deviation from Keplerian rotation in the gas to a perturbation in surface density of the gas and dust. Meth

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11

Held, Martin, and Stefan de Lorenzo. "On the generation of spiral-like paths within planar shapes." Journal of Computational Design and Engineering 5, no. 3 (2017): 348–57. http://dx.doi.org/10.1016/j.jcde.2017.11.011.

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Abstract We simplify and extend prior work by Held and Spielberger [CAD 2009, CAD&A 2014] to obtain spiral-like paths inside of planar shapes bounded by straight-line segments and circular arcs: We use a linearization to derive a simple algorithm that computes a continuous spiral-like path which (1) consists of straight-line segments, (2) has no self-intersections, (3) respects a user-specified maximum step-over distance, and (4) starts in the interior and ends at the boundary of the shape. Then we extend this basic algorithm to double-spiral paths that start and end at the boundary, and s

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Savchenko, Sergey, Alexander Marchuk, Aleksandr Mosenkov, and Konstantin Grishunin. "A multiwavelength study of spiral structure in galaxies. I. General characteristics in the optical." Monthly Notices of the Royal Astronomical Society 493, no. 1 (2020): 390–409. http://dx.doi.org/10.1093/mnras/staa258.

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ABSTRACT Different spiral generation mechanisms are expected to produce different morphological and kinematic features. In this first paper in a series, we carefully study the parameters of spiral structure in 155 face-on spiral galaxies, selected from the Sloan Digital Sky Survey, in the three gri bands. We use a method for deriving a set of parameters of spiral structure, such as the width of the spiral arms, their fraction to the total galaxy luminosity, and their colour, which have not been properly studied before. Our method is based on an analysis of a set of photometric cuts perpendicul

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Bekki, K. "Quantifying the fine structures of disk galaxies with deep learning: Segmentation of spiral arms in different Hubble types." Astronomy & Astrophysics 647 (March 2021): A120. http://dx.doi.org/10.1051/0004-6361/202039797.

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Context. Spatial correlations between spiral arms and other galactic components such as giant molecular clouds and massive OB stars suggest that spiral arms can play vital roles in various aspects of disk galaxy evolution. Segmentation of spiral arms in disk galaxies is therefore a key task when these correlations are to be investigated. Aims. We therefore decomposed disk galaxies into spiral and nonspiral regions using the code U-Net, which is based on deep-learning algorithms and has been invented for segmentation tasks in biology. Methods. We first trained this U-Net with a large number of

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14

DELLNITZ, MICHAEL, MARTIN GOLUBITSKY, ANDREAS HOHMANN, and IAN STEWART. "SPIRALS IN SCALAR REACTION–DIFFUSION EQUATIONS." International Journal of Bifurcation and Chaos 05, no. 06 (1995): 1487–501. http://dx.doi.org/10.1142/s0218127495001149.

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Spiral patterns have been observed experimentally, numerically, and theoretically in a variety of systems. It is often believed that these spiral wave patterns can occur only in systems of reaction–diffusion equations. We show, both theoretically (using Hopf bifurcation techniques) and numerically (using both direct simulation and continuation of rotating waves) that spiral wave patterns can appear in a single reaction–diffusion equation [ in u(x, t)] on a disk, if one assumes "spiral" boundary conditions (ur = muθ). Spiral boundary conditions are motivated by assuming that a solution is infin

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15

Hou, Chongchi, Wenzhong Zheng, and Wei Chang. "BEHAVIOUR OF HIGH-STRENGTH CONCRETE CIRCULAR COLUMNS CONFINED BY HIGH-STRENGTH SPIRALS UNDER CONCENTRIC COMPRESSION." JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 26, no. 6 (2020): 564–78. http://dx.doi.org/10.3846/jcem.2020.12913.

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This paper tested the behaviour of 32 high-strength concrete columns confined by high-strength spirals under concentric compression. The test parameters included unconfined concrete compressive strength, spiral yield strength, volumetric ratio, and spiral spacing. The results showed that bulging and shear sliding were the two characteristic types of failure patterns of the thirty-two confined columns, depending on spiral spacing and concrete strength. Moreover, the spiral in most specimens did not yield at the confined concrete compressive strength. An analytical confinement model for high-str

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16

Abrahamsen, Mikkel. "Spiral tool paths for high-speed machining of 2D pockets with or without islands." Journal of Computational Design and Engineering 6, no. 1 (2018): 105–17. http://dx.doi.org/10.1016/j.jcde.2018.01.003.

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Abstract We describe new methods for the construction of spiral tool paths for high-speed machining. In the simplest case, our method takes a polygon as input and a number δ&gt;0 and returns a spiral starting at a central point in the polygon, going around towards the boundary while morphing to the shape of the polygon. The spiral consists of linear segments and circular arcs, it is G1 continuous, it has no self-intersections, and the distance from each point on the spiral to each of the neighboring revolutions is at most δ. Our method has the advantage over previously described methods th

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17

Díaz-García, S., H. Salo, J. H. Knapen, and M. Herrera-Endoqui. "The shapes of spiral arms in the S4G survey and their connection with stellar bars." Astronomy & Astrophysics 631 (October 28, 2019): A94. http://dx.doi.org/10.1051/0004-6361/201936000.

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Context. Spiral galaxies are very common in the local Universe, but their formation, evolution, and interplay with bars remain poorly understood after more than a century of astronomical research on the topic. Aims. We use a sample of 391 nearby galaxies from the S4G survey to characterise the winding angle and amplitude of spiral arms as a function of disc properties, such as bar strength, in all kinds of spirals (grand-design, multi-armed, and flocculent). Methods. We derived global pitch angles in 3.6 μm de-projected images from (i) average measurements of individual logarithmic spiral segm

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18

Broscăţeanu, Ștefan Cezar. "Special Curves in Engineering. Surfaces Generated by the Logarithmic Spiral." Modelling in Civil Environmental Engineering 17, no. 1 (2022): 1–6. http://dx.doi.org/10.2478/mcee-2022-0001.

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Abstract The logarithmic spiral is one of the most known curves with applications in engineering. We consider product of the logarithmic spiral with a real line and tensor product of two logarithmic spirals and investigate their minimality or flatness. The Vrănceanu surface, with c 1 a logarithmic spiral, is also considered.

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19

SPÍCHAL, LUDĚK. "Gielis Transformation of the Archimedean Spiral." Kragujevac Journal of Mathematics 49, no. 3 (2024): 431–42. http://dx.doi.org/10.46793/kgjmat2503.431s.

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The article shows that the Archimedean spiral, usually described as a smooth spiral, can be transformed in many diﬀerent shapes. The main part of the article concentrates on the curvature of the transformed spirals. It will also be shown that the shape some of them is an approximation of spiral antennas.

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20

Speedie, Jessica, Richard A. Booth, and Ruobing Dong. "Observing Planet-driven Dust Spirals with ALMA." Astrophysical Journal 930, no. 1 (2022): 40. http://dx.doi.org/10.3847/1538-4357/ac5cc0.

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Abstract Atacama Large Millimeter/submillimeter Array (ALMA) continuum observations of thermal emission from the dust component of protoplanetary disks have revealed an abundance of substructures that may be interpreted as evidence for embedded planets, but planet-driven spiral arms—perhaps one of the most compelling lines of evidence—have proven comparatively elusive. In this work, we test the capabilities of ALMA to detect the planet-driven spiral signal in continuum emission. Carrying out hydrodynamic simulations and radiative transfer calculations, we present synthetic Band 7 continuum ima

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21

Singh, Manju, and Vijay Khare. "Detection of Parkinson’s Disease Using the Spiral Diagram and Convolutional Neural Network." Ingénierie des systèmes d information 27, no. 6 (2022): 991–97. http://dx.doi.org/10.18280/isi.270616.

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This study intends to propose a PD detection using spiral sketching and CNN. The fundamental idea is to analyze a person's spiral drawings and classify them as healthy or having Parkinson's disease. Spiral sketches drawn by healthy people look almost like standard spiral shapes. However, the spirals drawn by people with Parkinson's disease look distorted because they deviate significantly from their perfect spiral shape due to slow movement, and poor hand-brain coordination. In this paper Convolution, Neural Network is used to detect Parkinson’s, and 83.6% classification accuracy is obtained.

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Fridman, A. M., A. G. Morozov, M. V. Nezlin, et al. "On the Hydrodynamical Conception of the Spiral Structure in Galaxies with a Velocity “Kink” on the Rotation Curve (Theory, Laboratory Experiments, Numerical Simulation, Observations)." Symposium - International Astronomical Union 121 (1987): 147–57. http://dx.doi.org/10.1017/s0074180900155068.

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The hydrodynamical conception of the spiral structure generation in the galaxies with a “kink” on the rotation curve is discussed. It treats the spirals as density waves in gas component of galactic disks. The main results of the fifteen-year study are presented. References are made to the papers of authors that prove a) the “gas” conception of the Galaxy spiral structure, b) the identity of equations for rotating shallow water and galactic gas disk, c) the method of laboratory modelling of galactic spirals induced by hydrodynamical mechanisms in shallow water experiments with the “Spiral” set

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23

Liu, Can Ming, Yan Li, and Yu Mei Cui. "Application of Spirals in Fashion Design." Advanced Materials Research 627 (December 2012): 506–9. http://dx.doi.org/10.4028/www.scientific.net/amr.627.506.

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This paper gives the definition and forms of expression of “the spiral” and expounds the methods of application and variation of the spiral in fashion design. Different expressive forms of different spirals are analyzed and sorted out, and experimental creation is carried out. Finally, combing knowledge of fabrics, of draping and of design techniques, an analysis is made of the effect of the use of different fabrics and draping on spiral forms to achieve the best three-dimensional effects. Comparative research and literature referencing are used for this paper. Case study is also made of parti

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Francis, Charles, and Erik Anderson. "Galactic spiral structure." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 465, no. 2111 (2009): 3425–46. http://dx.doi.org/10.1098/rspa.2009.0036.

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We describe the structure and composition of six major stellar streams in a population of 20 574 local stars in the New Hipparcos Reduction with known radial velocities. We find that, once fast moving stars are excluded, almost all stars belong to one of these streams. The results of our investigation have led us to re-examine the hydrogen maps of the Milky Way, from which we identify the possibility of a symmetric two-armed spiral with half the conventionally accepted pitch angle. We describe a model of spiral arm motions that matches the observed velocities and compositions of the six major

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Нevko, Ivan, Andrii Diachun, Taras Dubynyak, Oleg Stibailo, and Andriі Gupka. "Technological Features of the Production of Shredder Knives on Screw Spirals." Central Ukrainian Scientific Bulletin. Technical Sciences 1, no. 11(42) (2025): 75–83. https://doi.org/10.32515/2664-262x.2025.11(42).1.75-83.

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Screw working bodies equipped with chopper knives and similar blade elements are used in various sectors of the economy, such as construction, food and processing, mining, road construction, etc. Their use often provides a combination of various technological operations related to the transformation of agricultural and other products, in particular grinding, mixing and moving. However, they found the widest use in the means for the production of materials, compound feed and other agricultural feed for feeding cattle, pigs, other animals and poultry. And taking into account the significant cost

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Sarkar, Suman, Biswajit Pandey, and Apashanka Das. "On the origin of red spirals: does assembly bias play a role?" Journal of Cosmology and Astroparticle Physics 2022, no. 03 (2022): 024. http://dx.doi.org/10.1088/1475-7516/2022/03/024.

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Abstract The formation of the red spirals is a puzzling issue in the standard picture of galaxy formation and evolution. Most studies attribute the colour of the red spirals to different environmental effects. We analyze a volume limited sample from the SDSS to study the roles of small-scale and large-scale environments on the colour of spiral galaxies. We compare the star formation rate, stellar age and stellar mass distributions of the red and blue spirals and find statistically significant differences between them at 99.9% confidence level. The red spirals inhabit significantly denser regio

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Bidnichenko, Helen. "LOGARITHMIC SPIRAL AS A GEOMETRIC FORM AND ITS NATURAL AND PRACTICAL APPLICATION." APPLIED GEOMETRY AND ENGINEERING GRAPHICS, no. 108 (July 3, 2025): 3–17. https://doi.org/10.32347/0131-579x.2025.108.3-17.

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This work is devoted to the topical issue of analyzing the geometric features of the logarithmic spiral. Its theoretical and practical aspects and its natural practical application are considered. A mathematical description of the logarithmic spiral is given and its geometric model is developed: the spiral equations are given in polar coordinates and in parametric form, flat geometric models are constructed, and its geometric properties are investigated, which allow the use of this particular form in various technical areas of activity, in particular in mechanical engineering, as well as in as

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Mengistu, Petra, and Karen L. Masters. "Mass and Color Dependence of the Hubble Spiral Sequence." Research Notes of the AAS 7, no. 3 (2023): 35. http://dx.doi.org/10.3847/2515-5172/acc032.

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Abstract In the classic Hubble spiral sequence, arm windiness correlates with bulge size; Sa type spiral galaxies with larger bulges also have the most tightly wound spirals. Exceptions to this have long been known, and in recent work using Galaxy Zoo morphologies no strong correlation was seen in a volume limited sample. In this Research Note, we explore the impact of galaxy mass and integrated color upon this correlation in the Galaxy Zoo sample, finding that bluer and lower mass spirals show the “expected” correlation; however, it becomes slightly negative for redder and/or more massive spi

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Cameron, Vinoo. "The Inverse Infinite Spiral Placement of Prime Numbers and Their Derivatives at the Cone of Pythagoras 1:3." JOURNAL OF ADVANCES IN PHYSICS 16, no. 1 (2019): 355–61. http://dx.doi.org/10.24297/jap.v16i1.8437.

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All mathematics of placement in this paper is mathematically absolute and precise by clear mathematics. This paper(section1) is the very basic “synopsis” of an upcoming book by the author “The God of Papa Einstein and Sir Isaac Newton “. It delineates the predictable expanding spirals of the prime numbers and their derivatives, by two cords, that hug the half-line of the 1:3 Pythagoras inverse cone. The inner spiral of all predictable spirals of prime numbers and their derivatives and the outer spiral at the predictable template of a spiral of prime number 5(+10,+20 alternate), which is the ex

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Wang, Chunni, Jun Ma, Bolin Hu, and Wuyin Jin. "Formation of multi-armed spiral waves in neuronal network induced by adjusting ion channel conductance." International Journal of Modern Physics B 29, no. 07 (2015): 1550043. http://dx.doi.org/10.1142/s0217979215500435.

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The Hodgkin–Huxley neuron model is used to describe the local dynamics of nodes in a two-dimensional regular network with nearest-neighbor connections. Multi-armed spiral waves emerge when a group of spiral waves rotate the same core synchronously. Here we have numerically investigated how multi-armed spiral waves are formed in such a system. Under the appropriate conditions, multi-armed spiral waves were able to develop as a result of adjusting the conductance of ion channels of particular neurons in the network. In a realistic neuron model, it can be practiced by blocking potassium of ion ch

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Koprowski, Arkadiusz, Dominik Gotowski, Romuald Rządkowski, and Ryszard Szczepanik. "Various inlet spiral geometries in 1MW steam turbine." E3S Web of Conferences 137 (2019): 01038. http://dx.doi.org/10.1051/e3sconf/201913701038.

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In small turbines, inlets can be designed using an inlet spiral. This paper analyses the efficiency of eight turbine variants, including seven with three stator and rotor blades and inlet spirals of various geometries, and one variant with a spiral, three stages and an outlet. This involves a 3D steady viscous flow using ANSYS CFX. The analysis shows that the spiral has a considerable influence on turbine efficiency.

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Нevko, Ivan, Roman Leshchuk, Andriy Briksa, Oleg Stibailo, and Serhiy Koval. "Features of structures and technological design of working bodies of bladed screw mixers." Central Ukrainian Scientific Bulletin. Technical Sciences 2, no. 8(39) (2023): 24–34. http://dx.doi.org/10.32515/2664-262x.2023.8(39).2.24-34.

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Blade screw mixers are typical tools for mixing building materials, compound feed, various types of products in the food industry, etc. The principle of their operation uses a combination of the operation of moving multicomponent mixtures with the operation of mixing them. Features of bladed screw working bodies of mixers are the arrangement of blades along a helical line along the axis of the shaft, on which they are, as a rule, immovably fixed. However, separate structures of working bodies can be located on the shaft with the possibility of rotation. The production of the working body of th

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Shields, Deanna, Benjamin Boe, Casey Pfountz, et al. "Spirality: A Novel Way to Measure Spiral Arm Pitch Angle." Galaxies 10, no. 5 (2022): 100. http://dx.doi.org/10.3390/galaxies10050100.

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We present the MATLAB code Spirality, a novel method for measuring spiral arm pitch angles by fitting galaxy images to spiral templates of known pitch. Computation time is typically on the order of 2 min per galaxy, assuming 8 GB of working memory. We tested the code using 117 synthetic spiral images with known pitches, varying both the spiral properties and the input parameters. The code yielded correct results for all synthetic spirals with galaxy-like properties. We also compared the code’s results to two-dimensional Fast Fourier Transform (2DFFT) measurements for the sample of nearby galax

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Mahajan, Smriti, Kriti Kamal Gupta, Rahul Rana, et al. "Galaxy And Mass Assembly (GAMA): properties and evolution of red spiral galaxies." Monthly Notices of the Royal Astronomical Society 491, no. 1 (2019): 398–408. http://dx.doi.org/10.1093/mnras/stz2993.

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ABSTRACT We use multiwavelength data from the Galaxy And Mass Assembly (GAMA) survey to explore the cause of red optical colours in nearby (0.002 < z < 0.06) spiral galaxies. We show that the colours of red spiral galaxies are a direct consequence of some environment-related mechanism(s) that has removed dust and gas, leading to a lower star formation rate. We conclude that this process acts on long time-scales (several Gyr) due to a lack of morphological transformation associated with the transition in optical colour. The specific star formation rate (sSFR) and dust-to-stellar mass rati

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Gobato, Ricardo, Abhijit Mitra, and Poulomi Mullick. "Extratropical cyclone in the South Georgia and south sandwich islands and double spiral galaxies." Physics & Astronomy International Journal 7, no. 3 (2023): 157–61. http://dx.doi.org/10.15406/paij.2023.07.00303.

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The work is focused on the comparative analysis of the shape of spiral galaxies and the subtropical cyclone that formed north of Georgia Island and passed north of the South Sandwich Islands, in the South Atlantic Ocean. Subtropical cyclones with double spirals appear to be common in these areas of the South Atlantic. A subtropical cyclone is a weather system that has some characteristics of a tropical cyclone and some characteristics of an extratropical cyclone. They can form between the equator and the 50th parallel. In mathematics, a spiral is a curve, which emanates from a point, moving fa

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STEINBOCK, O., and S. C. MÜLLER. "MULTI-ARMED SPIRALS IN A LIGHT-CONTROLLED EXCITABLE REACTION." International Journal of Bifurcation and Chaos 03, no. 02 (1993): 437–43. http://dx.doi.org/10.1142/s0218127493000325.

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The dynamics and geometry of multi-armed spirals in the light-sensitive ruthenium-catalyzed Belousov-Zhabotinsky reaction were investigated experimentally. The patterns were generated by a novel technique based on laser illumination, which allows the formation, control and annihilation of spiral waves. The rotation of n-armed spirals (n≤6) is stabilized by an unexcitable disk, created by a green laser beam. After switching off the laser, the central disk region becomes excitable again and individual cores are formed for each spiral arm. A symmetric collision structure appears periodically in t

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Korzinov, Lev, Andrej Nikulin, and Mihail Rabinovich. "Dynamics of defects in target pattern and origin of spirals with a high topological charge." Izvestiya VUZ. Applied Nonlinear Dynamics 2, no. 2 (1994): 73–80. https://doi.org/10.18500/0869-6632-1994-2-2-73-80.

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Recently, Ahlers and his group demonstrated remarkable experiments on the convection of gaseous CO2 in a large aspect ratio cylindrical cell. They discovered formation of stable multiarmed spirals (with the topological charge from 1 to 13). In this work it is shown that the multiarmed spiral is a result of the evolution of defects against the background of a cylindrical target. As a result of the interaction of the defects with the cylindrical structure and with each other the defects come to the target center and a stable multiarmed spiral is formed. The topological charge of this spiral depe

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Troy, William C. "Logarithmic spiral solutions of the Kopell–Howard lambda–omega reaction–diffusion equations." Chaos: An Interdisciplinary Journal of Nonlinear Science 32, no. 5 (2022): 053104. http://dx.doi.org/10.1063/5.0082736.

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Our investigation of logarithmic spirals is motivated by disparate experimental results: (i) the discovery of logarithmic spiral shaped precipitate formation in chemical garden experiments. Understanding precipitate formation in chemical gardens is important since analogous precipitates form in deep ocean hydrothermal vents, where conditions may be compatible with the emergence of life. (ii) The discovery that logarithmic spiral shaped waves of spreading depression can spontaneously form and cause macular degeneration in hypoglycemic chick retina. The role of reaction–diffusion mechanisms in s

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Kulikov, Y. I., Y. Vinogradova, A. W. Miles, and G. Giddins. "Optimal configuration of the spiral linking technique for tendon repair. Biomechanical evaluation." Journal of Hand Surgery (European Volume) 36, no. 3 (2010): 210–14. http://dx.doi.org/10.1177/1753193410390759.

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A previous study described a new spiral linking technique for tendon repairs and demonstrated that it was strong enough to be used in clinical practice as an alternative to the Pulvertaft tendon weave repair. However the repairs were less stiff, needed slightly more tendon length for the same repair and were a little bulkier. In this study two variables have been changed with a view to improving the spiral technique. At first the number of spirals was reduced consecutively, keeping the same number of standard mattress sutures. Once the optimal number of spirals had been identified, repairs wit

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BURSILL, L. A., and FAN XUDONG. "CLOSE-PACKING OF GROWING DISCS." Modern Physics Letters B 02, no. 11n12 (1988): 1245–52. http://dx.doi.org/10.1142/s0217984988001193.

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Spiral lattices are derived by allowing growing discs to aggregate under a close-packing rule. Both Fibonacci and Lucas numbers of visible spirals arise naturally, dependent only on the choice of growth centre. Both the rate of convergence towards an ideal spiral, and chirality, are determined by the initial placement of the first few discs (initial conditions). Thus the appearance of spiral packings is no more or less mysterious than the appearance of hexagonal packed arrays of equal discs.

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Martínez-García, Eric E., and Rosa Amelia González-Lópezlira. "Signatures of long-lived spiral patterns: The color gradient trend." Proceedings of the International Astronomical Union 10, H16 (2012): 323. http://dx.doi.org/10.1017/s1743921314005870.

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AbstractBased both on observations and simulations, recent works propose that the speed of the spiral pattern in disk galaxies may decrease with increasing radius; the implications are that patterns are actually short-lived, and that the azimuthal color/age gradients across spiral arms predicted by density wave theory could not be produced. We, however, have consistently found such gradients, and measured spiral pattern speeds by comparing the observations with stellar population synthesis models (González & Graham 1996; Martínez-García et al. 2009a, b; Martínez-García & González-López

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OIDA, KAZUMASA. "THE BIRTH AND DEATH PROCESSES OF HYPERCYCLE SPIRALS." Advances in Complex Systems 06, no. 04 (2003): 515–35. http://dx.doi.org/10.1142/s0219525903001018.

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The behavior of hypercycle spirals in a two-dimensional cellular automaton model is analyzed. Each spiral can be approximated by an Archimedean spiral with center, width, and phase change according to Brownian motion. A barrier exists between two spirals if the phase synchronization hypothesis is taken into account, and the occurrence rate of pair decay (simultaneous disappearance of two spirals) can be explained through a random walk simulation with the barrier. Simulation experiments show that adjacent species violation is necessary to create new spirals. A hypercycle system can live for a l

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BIKTASHEVA, I. V., A. V. HOLDEN, and V. N. BIKTASHEV. "LOCALIZATION OF RESPONSE FUNCTIONS OF SPIRAL WAVES IN THE FITZHUGH–NAGUMO SYSTEM." International Journal of Bifurcation and Chaos 16, no. 05 (2006): 1547–55. http://dx.doi.org/10.1142/s0218127406015490.

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Dynamics of spiral waves in perturbed, e.g. slightly inhomogeneous or subject to a small periodic external force, two-dimensional autowave media can be described asymptotically in terms of Aristotelean dynamics, so that the velocities of the spiral wave drift in space and time are proportional to the forces caused by the perturbation. The forces are defined as a convolution of the perturbation with the spirals Response Functions, which are eigenfunctions of the adjoint linearized problem. In this paper we find numerically the Response Functions of a spiral wave solution in the classic excitabl

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Lieb, Emma, Angela Collier, and Ann-Marie Madigan. "Bar-driven leading spiral arms in a counter-rotating dark matter halo." Monthly Notices of the Royal Astronomical Society 509, no. 1 (2021): 685–92. http://dx.doi.org/10.1093/mnras/stab2904.

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ABSTRACT An overwhelming majority of galactic spiral arms trail with respect to the rotation of the galaxy, though a small sample of leading spiral arms has been observed. The formation of these leading spirals is not well understood. Here we show, using collisionless N-body simulations, that a barred disc galaxy in a retrograde dark matter halo can produce long-lived (∼3 Gyr) leading spiral arms. Due to the strong resonant coupling of the disc to the halo, the bar slows rapidly and spiral perturbations are forced ahead of the bar. We predict that such a system, if observed, will also host a d

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Margalef-Bentabol, Berta, Christopher J. Conselice, Boris Haeussler, et al. "Observations of the initial formation and evolution of spiral galaxies at 1 < z < 3 in the CANDELS fields." Monthly Notices of the Royal Astronomical Society 511, no. 1 (2022): 1502–17. http://dx.doi.org/10.1093/mnras/stac080.

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ABSTRACT Many aspects concerning the formation of spiral and disc galaxies remain unresolved, despite their discovery and detailed study over the past 150 yr. As such, we present the results of an observational search for proto-spiral galaxies and their earliest formation, including the discovery of a significant population of spiral-like and clumpy galaxies at z &gt; 1 in deep Hubble Space Telescope CANDELS imaging. We carry out a detailed analysis of this population, characterizing their number density evolution, masses, star formation rates (SFR), and sizes. Overall, we find a surprisin

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Khoperskov, Sergey, and Giuseppe Bertin. "Spiral patterns beyond the optical radius: numerical simulations and synthetic HI observations." Proceedings of the International Astronomical Union 11, S321 (2016): 81–83. http://dx.doi.org/10.1017/s1743921316009078.

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AbstractThe outer parts of many galaxy disks exhibit extended spiral arms far beyond the optical radius. To understand the nature and the origin of such outer spiral structure, we investigate the propagation in the outer gaseous regions of large-scale spiral density waves excited in the bright optical disk. By means of 3D hydrodynamical simulations, we show that spiral density waves, penetrating in the gas through the outer Lindblad resonance, can indeed give rise to relatively regular patterns outside the bright optical stellar disk. The amplitude of spiral structure increases rapidly with ra

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Fuchs, B., V. Friese, H. Reffert, and R. Wielen. "Interaction of Disks and Dark Haloes of Dwarf Spirals." Symposium - International Astronomical Union 171 (1996): 171–74. http://dx.doi.org/10.1017/s0074180900232312.

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In a number of dwarf spiral galaxies the HI-emission has been studied with sufficient resolution to derive the rotation curves of the galaxies. These show that the disks of dwarf spirals are imbedded in extended haloes of dark matter, quite similar to the disks of giant spiral galaxies.

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Tadaki, Ken-ichi, Masanori Iye, Hideya Fukumoto, et al. "Spin parity of spiral galaxies II: a catalogue of 80 k spiral galaxies using big data from the Subaru Hyper Suprime-Cam survey and deep learning." Monthly Notices of the Royal Astronomical Society 496, no. 4 (2020): 4276–86. http://dx.doi.org/10.1093/mnras/staa1880.

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ABSTRACT We report an automated morphological classification of galaxies into S-wise spirals, Z-wise spirals, and non-spirals using big image data taken from Subaru/Hyper Suprime-Cam (HSC) Survey and a convolutional neural network (CNN)-based deep learning technique. The HSC i-band images are about 36 times deeper than those from the Sloan Digital Sky Survey (SDSS) and have a two times higher spatial resolution, allowing us to identify substructures such as spiral arms and bars in galaxies at z &gt; 0.1. We train CNN classifiers by using HSC images of 1447 S-spirals, 1382 Z-spirals, and 51

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Crilly, Tony. "A family of discrete spirals." Mathematical Gazette 104, no. 560 (2020): 215–24. http://dx.doi.org/10.1017/mag.2020.43.

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Most spirals are continuous spirals, certainly those famous in history such as the traditional Archimedean spiral (r = a + bθ) and the logarithmic spirals (r = aebθ. Here we consider ‘discrete spirals’.

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FELLI, M., R. CAMUSSI, and F. DI FELICE. "Mechanisms of evolution of the propeller wake in the transition and far fields." Journal of Fluid Mechanics 682 (May 31, 2011): 5–53. http://dx.doi.org/10.1017/jfm.2011.150.

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In the present study the mechanisms of evolution of propeller tip and hub vortices in the transitional region and the far field are investigated experimentally. The experiments involved detailed time-resolved visualizations and velocimetry measurements and were aimed at examining the effect of the spiral-to-spiral distance on the mechanisms of wake evolution and instability transition. In this regard, three propellers having the same blade geometry but different number of blades were considered. The study outlined dependence of the wake instability on the spiral-to-spiral distance and, in part

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