Get Our Extension

Logarithmic spiral

From Wikipedia, in a visual modern way
Logarithmic spiral (pitch 10°)
Logarithmic spiral (pitch 10°)
A section of the Mandelbrot set following a logarithmic spiral
A section of the Mandelbrot set following a logarithmic spiral

A logarithmic spiral, equiangular spiral, or growth spiral is a self-similar spiral curve that often appears in nature. The first to describe a logarithmic spiral was Albrecht Dürer (1525) who called it an "eternal line" ("ewige Linie").[1][2] More than a century later, the curve was discussed by Descartes (1638), and later extensively investigated by Jacob Bernoulli, who called it Spira mirabilis, "the marvelous spiral".

The logarithmic spiral can be distinguished from the Archimedean spiral by the fact that the distances between the turnings of a logarithmic spiral increase in geometric progression, while in an Archimedean spiral these distances are constant.

Discover more about Logarithmic spiral related topics

Self-similarity

Self-similarity

In mathematics, a self-similar object is exactly or approximately similar to a part of itself. Many objects in the real world, such as coastlines, are statistically self-similar: parts of them show the same statistical properties at many scales. Self-similarity is a typical property of fractals. Scale invariance is an exact form of self-similarity where at any magnification there is a smaller piece of the object that is similar to the whole. For instance, a side of the Koch snowflake is both symmetrical and scale-invariant; it can be continually magnified 3x without changing shape. The non-trivial similarity evident in fractals is distinguished by their fine structure, or detail on arbitrarily small scales. As a counterexample, whereas any portion of a straight line may resemble the whole, further detail is not revealed.

Curve

Curve

In mathematics, a curve is an object similar to a line, but that does not have to be straight.

Spiral

Spiral

In mathematics, a spiral is a curve which emanates from a point, moving farther away as it revolves around the point. It is a subtype of whorled patterns, a broad group that also includes concentric objects.

Albrecht Dürer

Albrecht Dürer

Albrecht Dürer, sometimes spelled in English as Durer or Duerer, was a German painter, printmaker, and theorist of the German Renaissance. Born in Nuremberg, Dürer established his reputation and influence across Europe in his twenties due to his high-quality woodcut prints. He was in contact with the major Italian artists of his time, including Raphael, Giovanni Bellini, and Leonardo da Vinci, and from 1512 was patronized by Emperor Maximilian I.

René Descartes

René Descartes

René Descartes was a French philosopher, scientist, and mathematician, widely considered a seminal figure in the emergence of modern philosophy and science. Mathematics was central to his method of inquiry, and he connected the previously separate fields of geometry and algebra into analytic geometry. Descartes spent much of his working life in the Dutch Republic, initially serving the Dutch States Army, later becoming a central intellectual of the Dutch Golden Age. Although he served a Protestant state and was later counted as a Deist by critics, Descartes was Roman Catholic.

Jacob Bernoulli

Jacob Bernoulli

Jacob Bernoulli was one of the many prominent mathematicians in the Bernoulli family. He was an early proponent of Leibnizian calculus and sided with Gottfried Wilhelm Leibniz during the Leibniz–Newton calculus controversy. He is known for his numerous contributions to calculus, and along with his brother Johann, was one of the founders of the calculus of variations. He also discovered the fundamental mathematical constant e. However, his most important contribution was in the field of probability, where he derived the first version of the law of large numbers in his work Ars Conjectandi.

Archimedean spiral

Archimedean spiral

The Archimedean spiral is a spiral named after the 3rd-century BC Greek mathematician Archimedes. It is the locus corresponding to the locations over time of a point moving away from a fixed point with a constant speed along a line that rotates with constant angular velocity. Equivalently, in polar coordinates (r, θ) it can be described by the equation

Geometric progression

Geometric progression

In mathematics, a geometric progression, also known as a geometric sequence, is a sequence of non-zero numbers where each term after the first is found by multiplying the previous one by a fixed, non-zero number called the common ratio. For example, the sequence 2, 6, 18, 54, ... is a geometric progression with common ratio 3. Similarly 10, 5, 2.5, 1.25, ... is a geometric sequence with common ratio 1/2.

Definition

In polar coordinates the logarithmic spiral can be written as[3]

or
with being the base of natural logarithms, and , being real constants.

Discover more about Definition related topics

In Cartesian coordinates

The logarithmic spiral with the polar equation

can be represented in Cartesian coordinates by
In the complex plane :

Spira mirabilis and Jacob Bernoulli

Spira mirabilis, Latin for "miraculous spiral", is another name for the logarithmic spiral. Although this curve had already been named by other mathematicians, the specific name ("miraculous" or "marvelous" spiral) was given to this curve by Jacob Bernoulli, because he was fascinated by one of its unique mathematical properties: the size of the spiral increases but its shape is unaltered with each successive curve, a property known as self-similarity. Possibly as a result of this unique property, the spira mirabilis has evolved in nature, appearing in certain growing forms such as nautilus shells and sunflower heads. Jacob Bernoulli wanted such a spiral engraved on his headstone along with the phrase "Eadem mutata resurgo" ("Although changed, I shall arise the same."), but, by error, an Archimedean spiral was placed there instead.[4][5]

Discover more about Spira mirabilis and Jacob Bernoulli related topics

Latin

Latin

Latin is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area around present-day Rome, but through the power of the Roman Republic it became the dominant language in the Italian region and subsequently throughout the Roman Empire. Even after the fall of Western Rome, Latin remained the common language of international communication, science, scholarship and academia in Europe until well into the 18th century, when other regional vernaculars supplanted it in common academic and political usage, and it eventually became a dead language in the modern linguistic definition.

Jacob Bernoulli

Jacob Bernoulli

Jacob Bernoulli was one of the many prominent mathematicians in the Bernoulli family. He was an early proponent of Leibnizian calculus and sided with Gottfried Wilhelm Leibniz during the Leibniz–Newton calculus controversy. He is known for his numerous contributions to calculus, and along with his brother Johann, was one of the founders of the calculus of variations. He also discovered the fundamental mathematical constant e. However, his most important contribution was in the field of probability, where he derived the first version of the law of large numbers in his work Ars Conjectandi.

Self-similarity

Self-similarity

In mathematics, a self-similar object is exactly or approximately similar to a part of itself. Many objects in the real world, such as coastlines, are statistically self-similar: parts of them show the same statistical properties at many scales. Self-similarity is a typical property of fractals. Scale invariance is an exact form of self-similarity where at any magnification there is a smaller piece of the object that is similar to the whole. For instance, a side of the Koch snowflake is both symmetrical and scale-invariant; it can be continually magnified 3x without changing shape. The non-trivial similarity evident in fractals is distinguished by their fine structure, or detail on arbitrarily small scales. As a counterexample, whereas any portion of a straight line may resemble the whole, further detail is not revealed.

Nautilus

Nautilus

The nautilus is a pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina.

Headstone

Headstone

A headstone, tombstone, or gravestone is a stele or marker, usually stone, that is placed over a grave. It is traditional for burials in the Christian, Jewish, and Muslim religions, among others. In most cases, it has the deceased's name, date of birth, and date of death inscribed on it, along with a personal message, or prayer, but may contain pieces of funerary art, especially details in stone relief. In many parts of Europe, insetting a photograph of the deceased in a frame is very common.

Eadem mutata resurgo

Eadem mutata resurgo

Eadem mutata resurgo is a Latin phrase that literally translates to "Although changed, I arise the same".

Archimedean spiral

Archimedean spiral

The Archimedean spiral is a spiral named after the 3rd-century BC Greek mathematician Archimedes. It is the locus corresponding to the locations over time of a point moving away from a fixed point with a constant speed along a line that rotates with constant angular velocity. Equivalently, in polar coordinates (r, θ) it can be described by the equation

Properties

Definition of slope angle and sector
Definition of slope angle and sector
Animation showing the constant angle between an intersecting circle centred at the origin and a logarithmic spiral.
Animation showing the constant angle between an intersecting circle centred at the origin and a logarithmic spiral.

The logarithmic spiral has the following properties (see Spiral):

  • Polar slope:
    with polar slope angle (see diagram and animation).
    (In case of angle would be 0 and the curve a circle with radius .)
  • Curvature:
  • Arc length:
    Especially: , if .
    This property was first realized by Evangelista Torricelli even before calculus had been invented.[6]
  • Sector area:
  • Inversion: Circle inversion () maps the logarithmic spiral onto the logarithmic spiral
Examples for 
  
    
      
        a
        =
        1
        ,
        2
        ,
        3
        ,
        4
        ,
        5
      
    
    {\displaystyle a=1,2,3,4,5}
Examples for
  • Rotating, scaling: Rotating the spiral by angle yields the spiral , which is the original spiral uniformly scaled (at the origin) by .
    Scaling by gives the same curve.
  • Self-similarity: A result of the previous property:
    A scaled logarithmic spiral is congruent (by rotation) to the original curve.
    Example: The diagram shows spirals with slope angle and . Hence they are all scaled copies of the red one. But they can also be generated by rotating the red one by angles resp.. All spirals have no points in common (see property on complex exponential function).
  • Relation to other curves: Logarithmic spirals are congruent to their own involutes, evolutes, and the pedal curves based on their centers.
  • Complex exponential function: The exponential function exactly maps all lines not parallel with the real or imaginary axis in the complex plane, to all logarithmic spirals in the complex plane with centre at :
    The polar slope angle of the logarithmic spiral is the angle between the line and the imaginary axis.

Discover more about Properties related topics

Spiral

Spiral

In mathematics, a spiral is a curve which emanates from a point, moving farther away as it revolves around the point. It is a subtype of whorled patterns, a broad group that also includes concentric objects.

Evangelista Torricelli

Evangelista Torricelli

Evangelista Torricelli was an Italian physicist and mathematician, and a student of Galileo. He is best known for his invention of the barometer, but is also known for his advances in optics and work on the method of indivisibles. The Torr is named after him.

Calculus

Calculus

Calculus is the mathematical study of continuous change, in the same way that geometry is the study of shape, and algebra is the study of generalizations of arithmetic operations.

Self-similarity

Self-similarity

In mathematics, a self-similar object is exactly or approximately similar to a part of itself. Many objects in the real world, such as coastlines, are statistically self-similar: parts of them show the same statistical properties at many scales. Self-similarity is a typical property of fractals. Scale invariance is an exact form of self-similarity where at any magnification there is a smaller piece of the object that is similar to the whole. For instance, a side of the Koch snowflake is both symmetrical and scale-invariant; it can be continually magnified 3x without changing shape. The non-trivial similarity evident in fractals is distinguished by their fine structure, or detail on arbitrarily small scales. As a counterexample, whereas any portion of a straight line may resemble the whole, further detail is not revealed.

Congruence (geometry)

Congruence (geometry)

In geometry, two figures or objects are congruent if they have the same shape and size, or if one has the same shape and size as the mirror image of the other.

Involute

Involute

In mathematics, an involute is a particular type of curve that is dependent on another shape or curve. An involute of a curve is the locus of a point on a piece of taut string as the string is either unwrapped from or wrapped around the curve.

Evolute

Evolute

In the differential geometry of curves, the evolute of a curve is the locus of all its centers of curvature. That is to say that when the center of curvature of each point on a curve is drawn, the resultant shape will be the evolute of that curve. The evolute of a circle is therefore a single point at its center. Equivalently, an evolute is the envelope of the normals to a curve.

Pedal curve

Pedal curve

In mathematics, a pedal curve of a given curve results from the orthogonal projection of a fixed point on the tangent lines of this curve. More precisely, for a plane curve C and a given fixed pedal point P, the pedal curve of C is the locus of points X so that the line PX is perpendicular to a tangent T to the curve passing through the point X. Conversely, at any point R on the curve C, let T be the tangent line at that point R; then there is a unique point X on the tangent T which forms with the pedal point P a line perpendicular to the tangent T – the pedal curve is the set of such points X, called the foot of the perpendicular to the tangent T from the fixed point P, as the variable point R ranges over the curve C.

Exponential function

Exponential function

The exponential function is a mathematical function denoted by or . Unless otherwise specified, the term generally refers to the positive-valued function of a real variable, although it can be extended to the complex numbers or generalized to other mathematical objects like matrices or Lie algebras. The exponential function originated from the notion of exponentiation, but modern definitions allow it to be rigorously extended to all real arguments, including irrational numbers. Its ubiquitous occurrence in pure and applied mathematics led mathematician Walter Rudin to opine that the exponential function is "the most important function in mathematics".

Special cases and approximations

The golden spiral is a logarithmic spiral that grows outward by a factor of the golden ratio for every 90 degrees of rotation (polar slope angle about 17.03239 degrees). It can be approximated by a "Fibonacci spiral", made of a sequence of quarter circles with radii proportional to Fibonacci numbers.

In nature

An extratropical cyclone over Iceland shows an approximately logarithmic spiral patternThe arms of spiral galaxies often have the shape of a logarithmic spiral, here the Whirlpool Galaxy
An extratropical cyclone over Iceland shows an approximately logarithmic spiral pattern
An extratropical cyclone over Iceland shows an approximately logarithmic spiral patternThe arms of spiral galaxies often have the shape of a logarithmic spiral, here the Whirlpool Galaxy
The arms of spiral galaxies often have the shape of a logarithmic spiral, here the Whirlpool Galaxy
Cutaway of a nautilus shell showing the chambers arranged in an approximately logarithmic spiral.  The plotted spiral (dashed blue curve) is based on growth rate parameter 
  
    
      
        b
        =
        0.1759
      
    
    {\displaystyle b=0.1759}
  
, resulting in a pitch of 
  
    
      
        arctan
        ⁡
        b
        ≈
        
          10
          
            ∘
          
        
      
    
    {\displaystyle \arctan b\approx 10^{\circ }}
  
.
Cutaway of a nautilus shell showing the chambers arranged in an approximately logarithmic spiral. The plotted spiral (dashed blue curve) is based on growth rate parameter , resulting in a pitch of .

In several natural phenomena one may find curves that are close to being logarithmic spirals. Here follow some examples and reasons:

  • The approach of a hawk to its prey in classical pursuit, assuming the prey travels in a straight line. Their sharpest view is at an angle to their direction of flight; this angle is the same as the spiral's pitch.[7]
  • The approach of an insect to a light source. They are used to having the light source at a constant angle to their flight path. Usually the sun (or moon for nocturnal species) is the only light source and flying that way will result in a practically straight line.[8]
  • The arms of spiral galaxies.[9] Our own galaxy, the Milky Way, has several spiral arms, each of which is roughly a logarithmic spiral with pitch of about 12 degrees.[10] However, although spiral galaxies have often been modeled as logarithmic spirals, Archimedean spirals, or hyperbolic spirals, their pitch angles vary with distance from the galactic center, unlike logarithmic spirals (for which this angle does not vary), and also at variance with the other mathematical spirals used to model them.[11]
  • The nerves of the cornea (this is, corneal nerves of the subepithelial layer terminate near superficial epithelial layer of the cornea in a logarithmic spiral pattern).[12]
  • The bands of tropical cyclones, such as hurricanes.[13]
  • Many biological structures including the shells of mollusks.[14] In these cases, the reason may be construction from expanding similar shapes, as is the case for polygonal figures.
  • Logarithmic spiral beaches can form as the result of wave refraction and diffraction by the coast. Half Moon Bay (California) is an example of such a type of beach.[15]

Discover more about In nature related topics

Extratropical cyclone

Extratropical cyclone

Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of producing anything from cloudiness and mild showers to severe gales, thunderstorms, blizzards, and tornadoes. These types of cyclones are defined as large scale (synoptic) low pressure weather systems that occur in the middle latitudes of the Earth. In contrast with tropical cyclones, extratropical cyclones produce rapid changes in temperature and dew point along broad lines, called weather fronts, about the center of the cyclone.

Iceland

Iceland

Iceland is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which is home to about 36% of the population. Iceland is the largest part of the Mid-Atlantic Ridge that rises above sea level, and its central volcanic plateau is erupting almost constantly. The interior consists of a plateau characterised by sand and lava fields, mountains, and glaciers, and many glacial rivers flow to the sea through the lowlands. Iceland is warmed by the Gulf Stream and has a temperate climate, despite a high latitude just outside the Arctic Circle. Its high latitude and marine influence keep summers chilly, and most of its islands have a polar climate.

Nautilus

Nautilus

The nautilus is a pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina.

Hawk

Hawk

Hawks are birds of prey of the family Accipitridae. They are widely distributed and are found on all continents except Antarctica.The subfamily Accipitrinae includes goshawks, sparrowhawks, sharp-shinned hawks and others. This subfamily are mainly woodland birds with long tails and high visual acuity. They hunt by dashing suddenly from a concealed perch. In America, members of the Buteo group are also called hawks; this group is called buzzards in other parts of the world. Generally, buteos have broad wings and sturdy builds. They are relatively larger-winged, shorter-tailed and fly further distances in open areas than accipiters. Buteos descend or pounce on their prey rather than hunting in a fast horizontal pursuit.

Galaxy

Galaxy

A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek galaxias (γαλαξίας), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. Galaxies, averaging an estimated 100 million stars, range in size from dwarfs with less than a hundred million stars, to the largest galaxies known – supergiants with one hundred trillion stars, each orbiting its galaxy's center of mass. Most of the mass in a typical galaxy is in the form of dark matter, with only a few percent of that mass visible in the form of stars and nebulae. Supermassive black holes are a common feature at the centres of galaxies.

Milky Way

Milky Way

The Milky Way is the galaxy that includes the Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. The term Milky Way is a translation of the Latin via lactea, from the Greek γαλακτικὸς κύκλος, meaning "milky circle". From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Doust Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies.

Archimedean spiral

Archimedean spiral

The Archimedean spiral is a spiral named after the 3rd-century BC Greek mathematician Archimedes. It is the locus corresponding to the locations over time of a point moving away from a fixed point with a constant speed along a line that rotates with constant angular velocity. Equivalently, in polar coordinates (r, θ) it can be described by the equation

Hyperbolic spiral

Hyperbolic spiral

A hyperbolic spiral is a plane curve, which can be described in polar coordinates by the equation

Cornea

Cornea

The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is approximately 43 dioptres. The cornea can be reshaped by surgical procedures such as LASIK.

Biology

Biology

Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary information encoded in genes, which can be transmitted to future generations. Another major theme is evolution, which explains the unity and diversity of life. Energy processing is also important to life as it allows organisms to move, grow, and reproduce. Finally, all organisms are able to regulate their own internal environments.

Mollusca

Mollusca

Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks. Around 85,000 extant species of molluscs are recognized. The number of fossil species is estimated between 60,000 and 100,000 additional species. The proportion of undescribed species is very high. Many taxa remain poorly studied.

Half Moon Bay (California)

Half Moon Bay (California)

Half Moon Bay is a bay of the Pacific Ocean on the coast of San Mateo County, California. The bay is approximately semi-circular, hence the name half moon, with sea access to the south. Coastal towns located there are Princeton-by-the-Sea, Miramar, El Granada, and the city of Half Moon Bay.

In engineering applications

A kerf-canceling mechanism leverages the self similarity of the logarithmic spiral to lock in place under rotation, independent of the kerf of the cut.[16]A logarithmic spiral antenna
A kerf-canceling mechanism leverages the self similarity of the logarithmic spiral to lock in place under rotation, independent of the kerf of the cut.[16]
A kerf-canceling mechanism leverages the self similarity of the logarithmic spiral to lock in place under rotation, independent of the kerf of the cut.[16]A logarithmic spiral antenna
A logarithmic spiral antenna
  • Logarithmic spiral antennas are frequency-independent antennas, that is, antennas whose radiation pattern, impedance and polarization remain largely unmodified over a wide bandwidth.[17]
  • When manufacturing mechanisms by subtractive fabrication machines (such as laser cutters), there can be a loss of precision when the mechanism is fabricated on a different machine due to the difference of material removed (that is, the kerf) by each machine in the cutting process. To adjust for this variation of kerf, the self-similar property of the logarithmic spiral has been used to design a kerf cancelling mechanism for laser cutters.[18]
  • Logarithmic spiral bevel gears are a type of spiral bevel gear whose gear tooth centerline is a logarithmic spiral. A logarithmic spiral has the advantage of providing equal angles between the tooth centerline and the radial lines, which gives the meshing transmission more stability.[19]

Source: "Logarithmic spiral", Wikipedia, Wikimedia Foundation, (2023, January 28th), https://en.wikipedia.org/wiki/Logarithmic_spiral.

Enjoying Wikiz?

Enjoying Wikiz?

Get our FREE extension now!

See also
References
  1. ^ Albrecht Dürer (1525). Underweysung der Messung, mit dem Zirckel und Richtscheyt, in Linien, Ebenen unnd gantzen corporen.
  2. ^ Hammer, Øyvind (2016). "Dürer's dirty secret". The Perfect Shape: Spiral Stories. Springer International Publishing. pp. 173–175. doi:10.1007/978-3-319-47373-4_41.
  3. ^ Priya Hemenway (2005). Divine Proportion: Φ Phi in Art, Nature, and Science. Sterling Publishing Co. ISBN 978-1-4027-3522-6.
  4. ^ Livio, Mario (2002). The Golden Ratio: The Story of Phi, The World's Most Astonishing Number. New York: Broadway Books. ISBN 978-0-7679-0815-3.
  5. ^ Yates, R. C.: A Handbook on Curves and Their Properties, J. W. Edwards (1952), "Evolutes". p. 206.
  6. ^ Carl Benjamin Boyer (1949). The history of the calculus and its conceptual development. Courier Dover Publications. p. 133. ISBN 978-0-486-60509-8.
  7. ^ Chin, Gilbert J. (8 December 2000), "Organismal Biology: Flying Along a Logarithmic Spiral", Science, 290 (5498): 1857, doi:10.1126/science.290.5498.1857c, S2CID 180484583
  8. ^ John Himmelman (2002). Discovering Moths: Nighttime Jewels in Your Own Backyard. Down East Enterprise Inc. p. 63. ISBN 978-0-89272-528-1.
  9. ^ G. Bertin and C. C. Lin (1996). Spiral structure in galaxies: a density wave theory. MIT Press. p. 78. ISBN 978-0-262-02396-2.
  10. ^ David J. Darling (2004). The universal book of mathematics: from Abracadabra to Zeno's paradoxes. John Wiley and Sons. p. 188. ISBN 978-0-471-27047-8.
  11. ^ Savchenko, S. S.; Reshetnikov, V. P. (September 2013). "Pitch angle variations in spiral galaxies". Monthly Notices of the Royal Astronomical Society. 436 (2): 1074–1083. doi:10.1093/mnras/stt1627.
  12. ^ C. Q. Yu CQ and M. I. Rosenblatt, "Transgenic corneal neurofluorescence in mice: a new model for in vivo investigation of nerve structure and regeneration," Invest Ophthalmol Vis Sci. 2007 Apr;48(4):1535-42.
  13. ^ Andrew Gray (1901). Treatise on physics, Volume 1. Churchill. pp. 356–357.
  14. ^ Michael Cortie (1992). "The form, function, and synthesis of the molluscan shell". In István Hargittai and Clifford A. Pickover (ed.). Spiral symmetry. World Scientific. p. 370. ISBN 978-981-02-0615-4.
  15. ^ Allan Thomas Williams and Anton Micallef (2009). Beach management: principles and practice. Earthscan. p. 14. ISBN 978-1-84407-435-8.
  16. ^ "kerf-canceling mechanisms". hpi.de. Retrieved 2020-12-26.
  17. ^ Mayes, P.E. (1992). "Frequency-independent antennas and broad-band derivatives thereof". Proceedings of the IEEE. 80 (1): 103–112. Bibcode:1992IEEEP..80..103M. doi:10.1109/5.119570.
  18. ^ Roumen, Thijs; Apel, Ingo; Shigeyama, Jotaro; Muhammad, Abdullah; Baudisch, Patrick (2020-10-20). "Kerf-Canceling Mechanisms: Making Laser-Cut Mechanisms Operate across Different Laser Cutters". Proceedings of the 33rd Annual ACM Symposium on User Interface Software and Technology. Virtual Event USA: ACM: 293–303. doi:10.1145/3379337.3415895. ISBN 978-1-4503-7514-6. S2CID 222805227.
  19. ^ Jiang, Jianfeng; Luo, Qingsheng; Wang, Liting; Qiao, Lijun; Li, Minghao (2020). "Review on logarithmic spiral bevel gear". Journal of the Brazilian Society of Mechanical Sciences and Engineering. 42 (8): 400. doi:10.1007/s40430-020-02488-y. ISSN 1678-5878.
External links

The content of this page is based on the Wikipedia article written by contributors..
The text is available under the Creative Commons Attribution-ShareAlike Licence & the media files are available under their respective licenses; additional terms may apply.
By using this site, you agree to the Terms of Use & Privacy Policy.
Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization & is not affiliated to WikiZ.com.