DOCSLIB.ORG

On Helices and Bertrand Curves in Euclidean 3-Space

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
On Helices and Bertrand Curves in Euclidean 3-Space ON HELİCES AND BERTRAND CURVES IN EUCLİDEAN 3-SPACE Murat Babaarslan Department of Mathematics, Faculty of Science and Arts Bozok University, Yozgat, Turkey [email protected] Yusuf Yaylı Department of Mathematics, Faculty of Science Ankara University, Tandoğan, Ankara, Turkey [email protected] Abstract- In this article, we investigate Bertrand curves corresponding to spherical images of the tangent indicatrix, binormal indicatrix, principal normal indicatrix and Darboux indicatrix of a space curve in Euclidean 3-space. As a result, in case of a space curve is general helix, we show that curve corresponding to spherical images of its tangent indicatrix and binormal indicatrix are circular helices and Bertrand curves. Similarly, in case of a space curve is slant helix, we demonstrate that the curve corresponding to spherical image of its principal normal indicatrix is circular helix and Bertrand curve. Key Words- Helix, Bertrand curve, Spherical Images 1. INTRODUCTION In the differential geometry of a regular curve in Euclidean 3-space E3 , it is well known that, one of the important problems is characterization of a regular curve. The curvature and the torsion of a regular curve play an important role to determine the shape and size of the curve 1,2. Natural scientists have long held a fascination, sometimes bordering on mystical obsession for helical structures in nature. Helices arise in nanosprings, carbon nonotubes, helices, DNA double and collagen triple helix, the double helix shape is commonly associated with DNA, since the double helix is structure of DNA 3 . This fact was published for the first time by Watson and Crick in 1953 4. They constructed a molecular model of DNA in which there were two complementary, antiparallel (side-by-side in opposite directions) strands of the bases guanine, adenine, thymine and cytosine, covalently linked through phosphodiesterase bonds 5,6 . Helix is one of the most fascinating curve in science and nature. Also we can see the helix curve or helical structures in fractal geometry, for instance hyperhelices 7. From the view of differential geometry, a helix is a geometric curve with non-vanishing constant curvature and with non-vanishing constant torsion 8 . The helix may be called a circular helix or W-curve 9,10 . Circular helix is the simplest three- dimensional spirals. One of the most interesting spiral examples are k -Fibonacci 1 spirals. These curves appear naturally from studying the -Fibonacci numbers F k k ,nn0 and the related hyperbolic k -Fibonacci function. Fibonacci numbers and the related Golden Mean or Golden section appear very often is theoretical physics and physics of the high energy particles 11,12. Three-dimensional k Fibonacci spirals were studied from a geometric point of view in 13 . A classical result about helix stated by Lancret in 1802 and first proved by Saint Venant in 1845 (see 14 for details). Thereafter Bertrand curves discovered by J. Bertrand in 1850 are one of the important and interesting topic of classical special curve theory. A Bertrand curve is defined as a special curve which shares its principal normals with another special curve (called Bertrand mate). Note that Bertrand mates are particular examples of offset curves used in computer-aided design 15 . The relationships among the curves are very important in differential geometry and mathematical physics. For example, Izumiya and Takeuchi 16 have shown that cylindrical helices can be constructed from plane curves and Bertrand curves can be constructed from spherical curves. Kula and Yaylı 17 have studied spherical images of tangent indicatrix and binormal indicatrix of a slant helix and they have shown that spherical images are spherical helix. Yalınız and Hacısalihoğlu 18 find the relation of between Frenet frame, slope axis and the curvature , torsion of null generalized helix in 4 -dimensional Lorentzian space. Camcı, İlarslan, Kula and Hacısalihoğlu 3 have given some characterizations for a non-degenerate curve to be a generalized helix by using harmonic curvatures of the curve in n -dimensional Euclidean space E n . The aim of this paper is to investigate Bertrand curves corresponding to spherical images of the tangent indicatrix, binormal indicatrix, principal normal indicatrix and Darboux indicatrix of a space curve in Euclidean 3-space. In case of a space curve is general helix, we show that curve corresponding to spherical images of its tangent indicatrix and binormal indicatrix are circular helices and Bertrand curves. Similarly, in case of a space curve is slant helix, we demonstrate that the curve corresponding to spherical image of its principal normal indicatrix is circular helix and Bertrand curve. 2. PRELIMINARIES We now recall basic concept on classical differential geometry of space curves and the definitions of spherical images, general helix, circular helix, slant helix and Bertrand curve in Euclidean 3-space. After that, we describe the method to construct Bertrand curves from spherical curves. A curve : IR 3 with unit speed, is a general helix if there is some constant vector u, so that T u cos is constant along the curve, where T (s) ~(s) and we call T (s) a unit tangent vector of ~ at s. We define the curvature of ~ by (s) ~(s) . If (s) 0, then the unit principal normal vector N(s) of curve ~ at s is given by ~(s) (s)N(s) . 2 The unit vector B(s) T(s) N(s) is called the unit binormal vector of ~ at s. For the derivations of the Frenet frame the Frenet-Serret formulae hold: T(s) (s)N(s) N(s) (s)T (s) (s)B(s) (1) B(s) (s)N(s) where (s) is the torsion of the curve ~ at s. For any unit speed curve ~ : I R3 , we call W (s) (s)T (s) (s)B(s) the Darboux vector field of ~ . Spherical images(indicatrix) are well-known in classical differential geometry of curves. Let us W (s) define the curve C on S 2 by the help of vector field C(s) . This curve is W (s) called the spherical Darboux image or the Darboux indicatrix of ~ . Similarly, the unit tangent vectors along the curve ~ generate a curve (T) on S 2 . The curve (T) is called the spherical indicatrix of T or more commonly. (T) is called tangent indicatrix of the curve ~ . If ~ ~(s) is a natural representation of ~ , then (T) T(s) will be a representation of (T). One considers the principal normal indicatrix (N) N(s) and binormal indicatrix (B) B(s) 14 . For a general parameter t of a space curve ~ , we can calculate the curvature and torsion as follows: ~ ~ (t) (t) det(~ (t),~(t),~(3) (t)) (t) , (t) (2) ~ ~ 3 / 2 2 ( (t) (t)) ~ (t)~(t) It has been known that the curve ~ is a general helix if and only if (s) const. If both of (s) 0 and (s) are constant, we call it as a circular helix. A curve ~ with (s) 0 is called a slant helix if the principal normal line of ~ make a constant angle with a fixed direction. ~ is a slant helix if and only if the geodesic curvature of the spherical image of the principal normal indicatrix (N) of ~ 2 (s) (s) (3) ( 2 2 )3 / 2 is a constant function 20 . On the other hand, : IR 3 with (s) 0 is called a Bertrand curve if there exists a curve : IR 3 such that the principal normal lines of : IR 3 and at s I are equal. In this case is called a Bertrand mate of ~ . For a space curve ~(s) with (s) 0, the curve ~ is a Bertrand curve if and only if there exist nonzero real numbers A, B such that A(s) B (s) 1 for any s I 1, 19 . So a circular helix is a Bertrand curve. 3 Now we give a new frame different from Frenet frame. Let : IS 2 be unit speed spherical curve. We denote as the arc-lenght parameter of . Let us denote d t( ) ( ), and we call t( ) a unit tangent vector of at , where . d We now set a vector s( ) ( ) t( ) . By definition, we have an orthonormal frame ( ),t( ),s( ) along . This frame is called the Sabban frame of 21 . Then we have the following spherical Frenet-Serret formulae of : ( ) t( ) t( ) ( ) g ( )s( ) (4) s( ) g ( )t( ) 2 where g ( ) is the geodesic curvature of the curve in S which is given by g ( ) det( ( ),t( ),t( )). We now define a space curve ~( ) a ( )d acot s( )d c (5) 0 0 where a, are constant numbers and c is a constant vector 16 . The following theorem and its result are key in this article. Theorem 1. Under the above notation, ~ is a Bertrand curve. Moreover, all Bertrand curves can be constructed by the above method 16 . Corollary 1. The spherical curve is a circle if and only if the corresponding Bertrand curves are circular helices 16 . 3. HELİCES AND BERTRAND CURVES IN EUCLİDEAN 3-SPACE In this section, we investigate Bertrand curves corresponding to spherical images of the tangent indicatrix, binormal indicatrix, normal indicatrix and Darboux indicatrix of a space curve in Euclidean 3-space and give some results about helices and Bertrand curves. Moreover an example spherical image of tangent indicatrix of space curve and Bertrand curve is presented. Theorem 2. Let be a space curve parametrized by s arc-length parameter. Then ~( ) a T( )d acot B( )d c (6) 0 0 is a Bertrand curve, where a, are constant numbers, c is a constant vector and s T(s) ds . 0 Proof. We denote spherical image of tangent indicatrix of space curve by (T). Then by Theorem 1, Bertrand curve corresponding to (T) is ~( ) a T( )d acot T( )T( )d c .
Load more

Recommended publications
  • Engineering Curves – I
    Engineering Curves – I 1. Classification 2. Conic sections - explanation 3. Common Definition 4. Ellipse – ( six methods of construction) 5. Parabola – ( Three methods of construction) 6. Hyperbola – ( Three methods of construction ) 7. Methods of drawing Tangents & Normals ( four cases) Engineering Curves – II 1. Classification 2. Definitions 3. Involutes - (five cases) 4. Cycloid 5. Trochoids – (Superior and Inferior) 6. Epic cycloid and Hypo - cycloid 7. Spiral (Two cases) 8. Helix – on cylinder & on cone 9. Methods of drawing Tangents and Normals (Three cases) ENGINEERING CURVES Part- I {Conic Sections} ELLIPSE PARABOLA HYPERBOLA 1.Concentric Circle Method 1.Rectangle Method 1.Rectangular Hyperbola (coordinates given) 2.Rectangle Method 2 Method of Tangents ( Triangle Method) 2 Rectangular Hyperbola 3.Oblong Method (P-V diagram - Equation given) 3.Basic Locus Method 4.Arcs of Circle Method (Directrix – focus) 3.Basic Locus Method (Directrix – focus) 5.Rhombus Metho 6.Basic Locus Method Methods of Drawing (Directrix – focus) Tangents & Normals To These Curves. CONIC SECTIONS ELLIPSE, PARABOLA AND HYPERBOLA ARE CALLED CONIC SECTIONS BECAUSE THESE CURVES APPEAR ON THE SURFACE OF A CONE WHEN IT IS CUT BY SOME TYPICAL CUTTING PLANES. OBSERVE ILLUSTRATIONS GIVEN BELOW.. Ellipse Section Plane Section Plane Hyperbola Through Generators Parallel to Axis. Section Plane Parallel to end generator. COMMON DEFINATION OF ELLIPSE, PARABOLA & HYPERBOLA: These are the loci of points moving in a plane such that the ratio of it’s distances from a fixed point And a fixed line always remains constant. The Ratio is called ECCENTRICITY. (E) A) For Ellipse E<1 B) For Parabola E=1 C) For Hyperbola E>1 Refer Problem nos.
    [Show full text]
  • A Characterization of Helical Polynomial Curves of Any Degree
    A CHARACTERIZATION OF HELICAL POLYNOMIAL CURVES OF ANY DEGREE J. MONTERDE Abstract. We give a full characterization of helical polynomial curves of any degree and a simple way to construct them. Existing results about Hermite interpolation are revisited. A simple method to select the best quintic interpolant among all possible solutions is suggested. 1. Introduction The notion of helical polynomial curves, i.e, polynomial curves which made a constant angle with a ¯xed line in space, have been studied by di®erent authors. Let us cite the papers [5, 6, 7] where the main results about the cubical and quintic cases are stablished. In [5] the authors gives a necessary condition a polynomial curve must satisfy in order to be a helix. The condition is expressed in terms of its hodograph, i.e., its derivative. If a polynomial curve, ®, is a helix then its hodograph, ®0, must be Pythagorean, i.e., jj®0jj2 is a perfect square of a polynomial. Moreover, this condition is su±cient in the cubical case: all PH cubical curves are helices. In the same paper it is also stated that not only ®0 must be Pythagorean, but also ®0^®00. Following the same ideas, in [1] it is proved that both conditions are su±cient in the quintic case. Unfortunately, this characterization is no longer true for higher degrees. It is possible to construct examples of polynomial curves of degree 7 verifying both conditions but being not a helix. The aim of this paper is just to show how a simple geometric trick can clarify the proofs of some previous results and to simplify the needed compu- tations to solve some related problems as for instance, the Hermite problem using helical polynomial curves.
    [Show full text]
  • Linguistic Presentation of Objects
    Zygmunt Ryznar dr emeritus Cracow Poland [email protected] Linguistic presentation of objects (types,structures,relations) Abstract Paper presents phrases for object specification in terms of structure, relations and dynamics. An applied notation provides a very concise (less words more contents) description of object. Keywords object relations, role, object type, object dynamics, geometric presentation Introduction This paper is based on OSL (Object Specification Language) [3] dedicated to present the various structures of objects, their relations and dynamics (events, actions and processes). Jay W.Forrester author of fundamental work "Industrial Dynamics”[4] considers the importance of relations: “the structure of interconnections and the interactions are often far more important than the parts of system”. Notation <!...> comment < > container of (phrase,name...) ≡> link to something external (outside of definition)) <def > </def> start-end of definition <spec> </spec> start-end of specification <beg> <end> start-end of section [..] or {..} 1 list of assigned keywords :[ or :{ structure ^<name> optional item (..) list of items xxxx(..) name of list = value assignment @ mark of special attribute,feature,property @dark unknown, to obtain, to discover :: belongs to : equivalent name (e.g.shortname) # number of |name| executive/operational object ppppXxxx name of item Xxxx with prefix ‘pppp ‘ XXXX basic object UUUU.xxxx xxxx object belonged to UUUU object class & / conjunctions ‘and’ ‘or’ 1 If using Latex editor we suggest [..] brackets
    [Show full text]
  • INTRODUCTION to ALGEBRAIC GEOMETRY, CLASS 25 Contents 1
    INTRODUCTION TO ALGEBRAIC GEOMETRY, CLASS 25 RAVI VAKIL Contents 1. The genus of a nonsingular projective curve 1 2. The Riemann-Roch Theorem with Applications but No Proof 2 2.1. A criterion for closed immersions 3 3. Recap of course 6 PS10 back today; PS11 due today. PS12 due Monday December 13. 1. The genus of a nonsingular projective curve The definition I’m going to give you isn’t the one people would typically start with. I prefer to introduce this one here, because it is more easily computable. Definition. The tentative genus of a nonsingular projective curve C is given by 1 − deg ΩC =2g 2. Fact (from Riemann-Roch, later). g is always a nonnegative integer, i.e. deg K = −2, 0, 2,.... Complex picture: Riemann-surface with g “holes”. Examples. Hence P1 has genus 0, smooth plane cubics have genus 1, etc. Exercise: Hyperelliptic curves. Suppose f(x0,x1) is a polynomial of homo- geneous degree n where n is even. Let C0 be the affine plane curve given by 2 y = f(1,x1), with the generically 2-to-1 cover C0 → U0.LetC1be the affine 2 plane curve given by z = f(x0, 1), with the generically 2-to-1 cover C1 → U1. Check that C0 and C1 are nonsingular. Show that you can glue together C0 and C1 (and the double covers) so as to give a double cover C → P1. (For computational convenience, you may assume that neither [0; 1] nor [1; 0] are zeros of f.) What goes wrong if n is odd? Show that the tentative genus of C is n/2 − 1.(Thisisa special case of the Riemann-Hurwitz formula.) This provides examples of curves of any genus.
    [Show full text]
  • Algebraic Geometry Michael Stoll
    Introductory Geometry Course No. 100 351 Fall 2005 Second Part: Algebraic Geometry Michael Stoll Contents 1. What Is Algebraic Geometry? 2 2. Affine Spaces and Algebraic Sets 3 3. Projective Spaces and Algebraic Sets 6 4. Projective Closure and Affine Patches 9 5. Morphisms and Rational Maps 11 6. Curves — Local Properties 14 7. B´ezout’sTheorem 18 2 1. What Is Algebraic Geometry? Linear Algebra can be seen (in parts at least) as the study of systems of linear equations. In geometric terms, this can be interpreted as the study of linear (or affine) subspaces of Cn (say). Algebraic Geometry generalizes this in a natural way be looking at systems of polynomial equations. Their geometric realizations (their solution sets in Cn, say) are called algebraic varieties. Many questions one can study in various parts of mathematics lead in a natural way to (systems of) polynomial equations, to which the methods of Algebraic Geometry can be applied. Algebraic Geometry provides a translation between algebra (solutions of equations) and geometry (points on algebraic varieties). The methods are mostly algebraic, but the geometry provides the intuition. Compared to Differential Geometry, in Algebraic Geometry we consider a rather restricted class of “manifolds” — those given by polynomial equations (we can allow “singularities”, however). For example, y = cos x defines a perfectly nice differentiable curve in the plane, but not an algebraic curve. In return, we can get stronger results, for example a criterion for the existence of solutions (in the complex numbers), or statements on the number of solutions (for example when intersecting two curves), or classification results.
    [Show full text]
  • Trigonometry Cram Sheet
    Trigonometry Cram Sheet August 3, 2016 Contents 6.2 Identities . 8 1 Definition 2 7 Relationships Between Sides and Angles 9 1.1 Extensions to Angles > 90◦ . 2 7.1 Law of Sines . 9 1.2 The Unit Circle . 2 7.2 Law of Cosines . 9 1.3 Degrees and Radians . 2 7.3 Law of Tangents . 9 1.4 Signs and Variations . 2 7.4 Law of Cotangents . 9 7.5 Mollweide’s Formula . 9 2 Properties and General Forms 3 7.6 Stewart’s Theorem . 9 2.1 Properties . 3 7.7 Angles in Terms of Sides . 9 2.1.1 sin x ................... 3 2.1.2 cos x ................... 3 8 Solving Triangles 10 2.1.3 tan x ................... 3 8.1 AAS/ASA Triangle . 10 2.1.4 csc x ................... 3 8.2 SAS Triangle . 10 2.1.5 sec x ................... 3 8.3 SSS Triangle . 10 2.1.6 cot x ................... 3 8.4 SSA Triangle . 11 2.2 General Forms of Trigonometric Functions . 3 8.5 Right Triangle . 11 3 Identities 4 9 Polar Coordinates 11 3.1 Basic Identities . 4 9.1 Properties . 11 3.2 Sum and Difference . 4 9.2 Coordinate Transformation . 11 3.3 Double Angle . 4 3.4 Half Angle . 4 10 Special Polar Graphs 11 3.5 Multiple Angle . 4 10.1 Limaçon of Pascal . 12 3.6 Power Reduction . 5 10.2 Rose . 13 3.7 Product to Sum . 5 10.3 Spiral of Archimedes . 13 3.8 Sum to Product . 5 10.4 Lemniscate of Bernoulli . 13 3.9 Linear Combinations .
    [Show full text]
  • Helical Curves and Double Pythagorean Hodographs
    Helical polynomial curves and “double” Pythagorean-hodograph curves Rida T. Farouki Department of Mechanical & Aeronautical Engineering, University of California, Davis — synopsis — • introduction: properties of Pythagorean-hodograph curves • computing rotation-minimizing frames on spatial PH curves • helical polynomial space curves — are always PH curves • standard quaternion representation for spatial PH curves • “double” Pythagorean hodograph structure — requires both |r0(t)| and |r0(t) × r00(t)| to be polynomials in t • Hermite interpolation problem: selection of free parameters Pythagorean-hodograph (PH) curves r(ξ) = PH curve ⇐⇒ coordinate components of r0(ξ) comprise a “Pythagorean n-tuple of polynomials” in Rn PH curves incorporate special algebraic structures in their hodographs (complex number & quaternion models for planar & spatial PH curves) • rational offset curves rd(ξ) = r(ξ) + d n(ξ) Z ξ • polynomial arc-length function s(ξ) = |r0(ξ)| dξ 0 Z 1 • closed-form evaluation of energy integral E = κ2 ds 0 • real-time CNC interpolators, rotation-minimizing frames, etc. helical polynomial space curves several equivalent characterizations of helical curves • tangent t maintains constant inclination ψ with fixed vector a • a · t = cos ψ, where ψ = pitch angle and a = axis vector of helix • fixed curvature/torsion ratio, κ/τ = tan ψ (Theorem of Lancret) • curve has a circular tangent indicatrix on the unit sphere (small circle for space curve, great circle for planar curve) • (r(2) × r(3)) · r(4) ≡ 0 — where r(k) = kth arc–length derivative
    [Show full text]
  • Study of Spiral Transition Curves As Related to the Visual Quality of Highway Alignment
    A STUDY OF SPIRAL TRANSITION CURVES AS RELA'^^ED TO THE VISUAL QUALITY OF HIGHWAY ALIGNMENT JERRY SHELDON MURPHY B, S., Kansas State University, 1968 A MJvSTER'S THESIS submitted in partial fulfillment of the requirements for the degree MASTER OF SCIENCE Department of Civil Engineering KANSAS STATE UNIVERSITY Manhattan, Kansas 1969 Approved by P^ajQT Professor TV- / / ^ / TABLE OF CONTENTS <2, 2^ INTRODUCTION 1 LITERATURE SEARCH 3 PURPOSE 5 SCOPE 6 • METHOD OF SOLUTION 7 RESULTS 18 RECOMMENDATIONS FOR FURTHER RESEARCH 27 CONCLUSION 33 REFERENCES 34 APPENDIX 36 LIST OF TABLES TABLE 1, Geonetry of Locations Studied 17 TABLE 2, Rates of Change of Slope Versus Curve Ratings 31 LIST OF FIGURES FIGURE 1. Definition of Sight Distance and Display Angle 8 FIGURE 2. Perspective Coordinate Transformation 9 FIGURE 3. Spiral Curve Calculation Equations 12 FIGURE 4. Flow Chart 14 FIGURE 5, Photograph and Perspective of Selected Location 15 FIGURE 6. Effect of Spiral Curves at Small Display Angles 19 A, No Spiral (Circular Curve) B, Completely Spiralized FIGURE 7. Effects of Spiral Curves (DA = .015 Radians, SD = 1000 Feet, D = l** and A = 10*) 20 Plate 1 A. No Spiral (Circular Curve) B, Spiral Length = 250 Feet FIGURE 8. Effects of Spiral Curves (DA = ,015 Radians, SD = 1000 Feet, D = 1° and A = 10°) 21 Plate 2 A. Spiral Length = 500 Feet B. Spiral Length = 1000 Feet (Conpletely Spiralized) FIGURE 9. Effects of Display Angle (D = 2°, A = 10°, Ig = 500 feet, = SD 500 feet) 23 Plate 1 A. Display Angle = .007 Radian B. Display Angle = .027 Radiaji FIGURE 10.
    [Show full text]
  • The Ordered Distribution of Natural Numbers on the Square Root Spiral
    The Ordered Distribution of Natural Numbers on the Square Root Spiral - Harry K. Hahn - Ludwig-Erhard-Str. 10 D-76275 Et Germanytlingen, Germany ------------------------------ mathematical analysis by - Kay Schoenberger - Humboldt-University Berlin ----------------------------- 20. June 2007 Abstract : Natural numbers divisible by the same prime factor lie on defined spiral graphs which are running through the “Square Root Spiral“ ( also named as “Spiral of Theodorus” or “Wurzel Spirale“ or “Einstein Spiral” ). Prime Numbers also clearly accumulate on such spiral graphs. And the square numbers 4, 9, 16, 25, 36 … form a highly three-symmetrical system of three spiral graphs, which divide the square-root-spiral into three equal areas. A mathematical analysis shows that these spiral graphs are defined by quadratic polynomials. The Square Root Spiral is a geometrical structure which is based on the three basic constants: 1, sqrt2 and π (pi) , and the continuous application of the Pythagorean Theorem of the right angled triangle. Fibonacci number sequences also play a part in the structure of the Square Root Spiral. Fibonacci Numbers divide the Square Root Spiral into areas and angle sectors with constant proportions. These proportions are linked to the “golden mean” ( golden section ), which behaves as a self-avoiding-walk- constant in the lattice-like structure of the square root spiral. Contents of the general section Page 1 Introduction to the Square Root Spiral 2 2 Mathematical description of the Square Root Spiral 4 3 The distribution
    [Show full text]
  • (Spiral Curves) When Transition Curves Are Not Provided, Drivers Tend To
    The Transition Curves (Spiral Curves) The transition curve (spiral) is a curve that has a varying radius. It is used on railroads and most modem highways. It has the following purposes: 1- Provide a gradual transition from the tangent (r=∞ )to a simple circular curve with radius R 2- Allows for gradual application of superelevation. Advantages of the spiral curves: 1- Provide a natural easy to follow path such that the lateral force increase and decrease gradually as the vehicle enters and leaves the circular curve 2- The length of the transition curve provides a suitable location for the superelevation runoff. 3- The spiral curve facilitate the transition in width where the travelled way is widened on circular curve. 4- The appearance of the highway is enhanced by the application of spiral curves. When transition curves are not provided, drivers tend to create their own transition curves by moving laterally within their travel lane and sometimes the adjoining lane, which is risky not only for them but also for other road users. Minimum length of spiral. Minimum length of spiral is based on consideration of driver comfort and shifts in the lateral position of vehicles. It is recommended that these two criteria be used together to determine the minimum length of spiral. Thus, the minimum spiral length can be computed as: Ls, min should be the larger of: , , . Ls,min = minimum length of spiral, m; Pmin = minimum lateral offset (shift) between the tangent and circular curve (0.20 m); R = radius of circular curve, m; V = design speed, km/h; C = maximum rate of change in lateral acceleration (1.2 m/s3) Maximum length of spiral.
    [Show full text]
  • A Gallery of De Rham Curves
    A Gallery of de Rham Curves Linas Vepstas <[email protected]> 20 August 2006 Abstract The de Rham curves are a set of fairly generic fractal curves exhibiting dyadic symmetry. Described by Georges de Rham in 1957[3], this set includes a number of the famous classical fractals, including the Koch snowflake, the Peano space- filling curve, the Cesàro-Faber curves, the Takagi-Landsberg[4] or blancmange curve, and the Lévy C-curve. This paper gives a brief review of the construction of these curves, demonstrates that the complete collection of linear affine deRham curves is a five-dimensional space, and then presents a collection of four dozen images exploring this space. These curves are interesting because they exhibit dyadic symmetry, with the dyadic symmetry monoid being an interesting subset of the group GL(2,Z). This is a companion article to several others[5][6] exploring the nature of this monoid in greater detail. 1 Introduction In a classic 1957 paper[3], Georges de Rham constructs a class of curves, and proves that these curves are everywhere continuous but are nowhere differentiable (more pre- cisely, are not differentiable at the rationals). In addition, he shows how the curves may be parameterized by a real number in the unit interval. The construction is simple. This section illustrates some of these curves. 2 2 2 2 Consider a pair of contracting maps of the plane d0 : R → R and d1 : R → R . By the Banach fixed point theorem, such contracting maps should have fixed points p0 and p1. Assume that each fixed point lies in the basin of attraction of the other map, and furthermore, that the one map applied to the fixed point of the other yields the same point, that is, d1(p0) = d0(p1) (1) These maps can then be used to construct a certain continuous curve between p0and p1.
    [Show full text]
  • Chapter 2. Parameterized Curves in R3
    Chapter 2. Parameterized Curves in R3 Def. A smooth curve in R3 is a smooth map σ :(a, b) → R3. For each t ∈ (a, b), σ(t) ∈ R3. As t increases from a to b, σ(t) traces out a curve in R3. In terms of components, σ(t) = (x(t), y(t), z(t)) , (1) or x = x(t) σ : y = y(t) a < t < b , z = z(t) dσ velocity at time t: (t) = σ0(t) = (x0(t), y0(t), z0(t)) . dt dσ speed at time t: (t) = |σ0(t)| dt Ex. σ : R → R3, σ(t) = (r cos t, r sin t, 0) - the standard parameterization of the unit circle, x = r cos t σ : y = r sin t z = 0 σ0(t) = (−r sin t, r cos t, 0) |σ0(t)| = r (constant speed) 1 Ex. σ : R → R3, σ(t) = (r cos t, r sin t, ht), r, h > 0 constants (helix). σ0(t) = (−r sin t, r cos t, h) √ |σ0(t)| = r2 + h2 (constant) Def A regular curve in R3 is a smooth curve σ :(a, b) → R3 such that σ0(t) 6= 0 for all t ∈ (a, b). That is, a regular curve is a smooth curve with everywhere nonzero velocity. Ex. Examples above are regular. Ex. σ : R → R3, σ(t) = (t3, t2, 0). σ is smooth, but not regular: σ0(t) = (3t2, 2t, 0) , σ0(0) = (0, 0, 0) Graph: x = t3 y = t2 = (x1/3)2 σ : y = t2 ⇒ y = x2/3 z = 0 There is a cusp, not because the curve isn’t smooth, but because the velocity = 0 at the origin.
    [Show full text]