Global ETD Search

1	Combinatorial Considerations on Two Models from Statistical Mechanics Thapper, Johan January 2007 (has links) Interactions between combinatorics and statistical mechanics have provided many fruitful insights in both fields. A compelling example is Kuperberg’s solution to the alternating sign matrix conjecture, and its following generalisations. In this thesis we investigate two models from statistical mechanics which have received attention in recent years. The first is the fully packed loop model. A conjecture from 2001 by Razumov and Stroganov opened the field for a large ongoing investigation of the O(1) loop model and its connections to a refinement of the fully packed loop model. We apply a combinatorial bijection originally found by de Gier to an older conjecture made by Propp. The second model is the hard particle model. Recent discoveries by Fendley et al. and results by Jonsson suggests that the hard square model with cylindrical boundary conditions possess some beautiful combinatorial properties. We apply both topological and purely combinatorial methods to related independence complexes to try and gain a better understanding of this model. fully packed loop model rhombus tilings hard particle model independence complex discrete morse theory Discrete mathematics Diskret matematik
2	Combinatorial Considerations on Two Models from Statistical Mechanics Thapper, Johan January 2007 (has links) <p>Interactions between combinatorics and statistical mechanics have provided many fruitful insights in both fields. A compelling example is Kuperberg’s solution to the alternating sign matrix conjecture, and its following generalisations. In this thesis we investigate two models from statistical mechanics which have received attention in recent years.</p><p>The first is the fully packed loop model. A conjecture from 2001 by Razumov and Stroganov opened the field for a large ongoing investigation of the O(1) loop model and its connections to a refinement of the fully packed loop model. We apply a combinatorial bijection originally found by de Gier to an older conjecture made by Propp.</p><p>The second model is the hard particle model. Recent discoveries by Fendley et al. and results by Jonsson suggests that the hard square model with cylindrical boundary conditions possess some beautiful combinatorial properties. We apply both topological and purely combinatorial methods to related independence complexes to try and gain a better understanding of this model.</p> fully packed loop model rhombus tilings hard particle model independence complex discrete morse theory Discrete mathematics Diskret matematik
3	Study of Mechanical Performance of Stent Implants Using Theoretical and Numerical Approach Yang, Hua, (Mechanical engineer) 08 1900 (has links) The coronary heart disease kills more than 350,000 persons/year and it costs $108.9 billion for the United States each year, in spite of significant advancements in clinical care and education for public, cardiovascular diseases (CVD) are leading cause of death and disability to the nation. A cardiovascular disease involves mainly heart or blood vessels (arteries, veins and capillaries) or both, and then mainly occurs in selected regions and affects heart, brain, kidney and peripheral arteries. As a surgical interventions, stent implantation is deployed to cure or ameliorate the disease. However, the high failure rate of stents used in patients with peripheral artery diseases has lead researchers to give special attention towards analyzing stent structure and characteristics. In this research, the mechanical properties of a stent based on the rhombus structure were analyzed and verified by means of analytical and numerical approaches. Theoretical model based on the beam theory were developed and numerical models were used to analyze the response of these structures under various and complex loading conditions. Moreover, the analysis of the stent inflation involves a model with large deformations and large strains, nonlinear material properties need to be considered to accurately capture the deformation process. The maximum stress values were found to occur in localized regions of the stent. These regions were generally found along the inner radii of each of the connected links connecting each of the longitudinal struts. Stress values throughout the whole stent were typically much lower. The peak engineering stress values were found to be less than the material ultimate strength (limit stress 515Mpa), indicating a safe stent design throughout expansion range. Lastly, the rheological behavior of blood can be quantified by non-Newtonian viscosity. Carreau model is introduced and simulates the situation in the artery, then the available shear stress in the model would help to the future analysis in the contact analysis of stent and the artery. Stent implants rhombus structure cardiovascular disease non-Newtonian flow Cardiovascular system -- Surgery. Heart -- Surgery.
4	Metrical Problems in Minkowski Geometry Fankhänel, Andreas 19 October 2012 (has links) (PDF) In this dissertation we study basic metrical properties of 2-dimensional normed linear spaces, so-called (Minkowski or) normed planes. In the first chapter we introduce a notion of angular measure, and we investigate under what conditions certain angular measures in a Minkowski plane exist. We show that only the Euclidean angular measure has the property that in an isosceles triangle the base angles are of equal size. However, angular measures with the property that the angle between orthogonal vectors has a value of pi/2, i.e, a quarter of the full circle, exist in a wider variety of normed planes, depending on the type of orthogonality. Due to this we have a closer look at isosceles and Birkhoff orthogonality. Finally, we present results concerning angular bisectors. In the second chapter we pay attention to convex quadrilaterals. We give definitions of different types of rectangles and rhombi and analyse under what conditions they coincide. Combinations of defining properties of rectangles and rhombi will yield squares, and we will see that any two types of squares are equal if and only if the plane is Euclidean. Additionally, we define a ``new\'\' type of quadrilaterals, the so-called codises. Since codises and rectangles coincide in Radon planes, we will explain why it makes sense to distinguish these two notions. For this purpose we introduce the concept of associated parallelograms. Finally we will deal with metrically defined conics, i.e., with analogues of conic sections in normed planes. We define metric ellipses (hyperbolas) as loci of points that have constant sum (difference) of distances to two given points, the so-called foci. Also we define metric parabolas as loci of points whose distance to a given point equals the distance to a fixed line. We present connections between the shape of the unit ball B and the shape of conics. More precisely, we will see that straight segments and corner points of B cause, under certain conditions, that conics have straight segments and corner points, too. Afterwards we consider intersecting ellipses and hyperbolas with identical foci. We prove that in special Minkowski planes, namely in the subfamily of polygonal planes, confocal ellipses and hyperbolas intersect in a way called Birkhoff orthogonal, whenever the respective ellipse is large enough. Winkelmaß Birkhoff-Orthogonalität Codis Kegelschnitt gleichschenklig-rechtwinklig metrische Ellipse metrische Hyperbel metrische Parabel metrisches Parallelogramm Minkowski-Ebene normierte Ebene Parallelogramm Radon-Ebene Rechteck Rhombus glatte Ebene Quadrat streng konvexe Ebene angular measure Birkhoff orthogonality codis conic section isosceles orthogonality metric ellipse metric hyperbola metric parabola metric parallelogram Minkowski plane normed plane parallelogram Radon plane rectangle rhombus smooth plane square strictly convex plane ddc:516 Minkowski-Geometrie Kegelschnitt Viereck Winkel
5	Metrical Problems in Minkowski Geometry Fankhänel, Andreas 07 June 2012 (has links) In this dissertation we study basic metrical properties of 2-dimensional normed linear spaces, so-called (Minkowski or) normed planes. In the first chapter we introduce a notion of angular measure, and we investigate under what conditions certain angular measures in a Minkowski plane exist. We show that only the Euclidean angular measure has the property that in an isosceles triangle the base angles are of equal size. However, angular measures with the property that the angle between orthogonal vectors has a value of pi/2, i.e, a quarter of the full circle, exist in a wider variety of normed planes, depending on the type of orthogonality. Due to this we have a closer look at isosceles and Birkhoff orthogonality. Finally, we present results concerning angular bisectors. In the second chapter we pay attention to convex quadrilaterals. We give definitions of different types of rectangles and rhombi and analyse under what conditions they coincide. Combinations of defining properties of rectangles and rhombi will yield squares, and we will see that any two types of squares are equal if and only if the plane is Euclidean. Additionally, we define a ``new\'\' type of quadrilaterals, the so-called codises. Since codises and rectangles coincide in Radon planes, we will explain why it makes sense to distinguish these two notions. For this purpose we introduce the concept of associated parallelograms. Finally we will deal with metrically defined conics, i.e., with analogues of conic sections in normed planes. We define metric ellipses (hyperbolas) as loci of points that have constant sum (difference) of distances to two given points, the so-called foci. Also we define metric parabolas as loci of points whose distance to a given point equals the distance to a fixed line. We present connections between the shape of the unit ball B and the shape of conics. More precisely, we will see that straight segments and corner points of B cause, under certain conditions, that conics have straight segments and corner points, too. Afterwards we consider intersecting ellipses and hyperbolas with identical foci. We prove that in special Minkowski planes, namely in the subfamily of polygonal planes, confocal ellipses and hyperbolas intersect in a way called Birkhoff orthogonal, whenever the respective ellipse is large enough.:1 Introduction 2 On angular measures 3 Types of convex quadrilaterals 4 On conic sections info:eu-repo/classification/ddc/516 ddc:516

1

Page generated in 0.02 seconds