65 research outputs found
S-Structures for k-linear categories and the definition of a modular functor
Motivated by ideas from string theory and quantum field theory new invariants
of knots and 3-dimensional manifolds have been constructed from complex
algebraic structures such as Hopf algebras (Reshetikhin and Turaev), monoidal
categories with additional structure (Turaev and Yetter), and modular functors
(Walker and Kontsevich). These constructions are very closely related. We take
a unifying categorical approach based on a natural 2-dimensional generalization
of a topological field theory in the sense of Atiyah and Segal, and show that
the axioms defining these complex algebraic structures are a consequence of the
underlying geometry of surfaces. In particular, we show that any linear
category over a field with an action of the surface category is semi-simple and
Artinian.Comment: Accepted for publication in the Journal of the LMS, April 199
Divisible convex sets with properly embedded cones
In this article we construct many examples of properly convex irreducible
domains divided by Zariski dense relatively hyperbolic groups in every
dimension at least 3. This answers a question of Benoist. Relative
hyperbolicity and non-strict convexity are captured by a family of properly
embedded cones (convex hulls of points and ellipsoids) in the domain. Our
construction is most flexible in dimension 3 where we give a purely topological
criterion for the existence of a large deformation space of geometrically
controlled convex projective structures with totally geodesic boundary on a
compact 3-manifold.Comment: 90 pages. Comments are welcome
REINFORCED CONCRETE AND STONE STRUCTURES
The textbook provides main information about construction materials (concrete, reinforced concrete, stone), their physical and mechanical properties, analysis of reinforced concrete and stone structures for strength, rigidity and crack resistance
REINFORCED CONCRETE AND STONE STRUCTURES
У підручнику розглянуто загальні відомості про матеріали (бетон, арма-
турну сталь, камінь) та їхні фізико-механічні властивості; основи розрахунку
залізобетонних та кам’яних конструкцій за міцністю, жорсткістю, тріщино-
стійкістю і способи їх конструювання.
Для студентів вищих навчальних закладів авіаційного та будівельного
профілю, а також спеціалістів, магістрів з проектування, будівництва аеро-
портів, промислового та цивільного будівництва.The textbook provides main information about construction materials (concrete,
reinforced concrete, stone), their physical and mechanical properties, resistance
calculation of reinforced concrete and stone structures for strength, rigidity and
crack endurance
A Geometrical Construction of Rational Boundary States in Linear Sigma Models
Starting from the geometrical construction of special Lagrangian submanifolds
of a toric variety, we identify a certain subclass of A-type D-branes in the
linear sigma model for a Calabi-Yau manifold and its mirror with the A- and
B-type Recknagel-Schomerus boundary states of the Gepner model, by reproducing
topological properties such as their labeling, intersection, and the
relationships that exist in the homology lattice of the D-branes. In the
non-linear sigma model phase these special Lagrangians reproduce an old
construction of 3-cycles relevant for computing periods of the Calabi-Yau, and
provide insight into other results in the literature on special Lagrangian
submanifolds on compact Calabi-Yau manifolds. The geometrical construction of
rational boundary states suggests several ways in which new Gepner model
boundary states may be constructed.Comment: 45 pages, 8 Postscript figures, LaTeX2e. v2: the construction
reproduces a larger set of CFT boundary states; clarified discussion of
instanton contributions and moduli; other minor improvements; references
added . v3: version accepted for publication in Nuclear Physics B (minor
changes
In-situ deformation monitoring of aerospace qualified composites with embedded improved draw tower fibre Bragg gratings
Aerospace certified fibre reinforced plastics (FRPs) are extreme performing construction materials, which today are increasingly applied in primary structures of the new generation aircrafts (e.g. Boeing 787, Airbus 350, Bombardier C-Series), such as the fuselage, the wings and the fin. An interesting aspect on the technological point of view of sensing is that airplane manufacturers such as Airbus and Boeing are looking at incorporating health-monitoring systems (such as optical fibre sensors, especially fibre Bragg gratings) that will allow the airplane to self-monitor and report maintenance requirements to ground-based computer systems. However, one has to realize that the mechanical behaviour of anisotropic FRPs is significantly different compared to conventional isotropic construction materials.
In this dissertation, the author focuses on monitoring the strain and (permanent) deformation in carbon reinforced plastic laminates with embedded fibre Bragg gratings. The research is divided in two main parts.
In the first part of this research, the existing fibre draw tower technology is utilized, to manufacture an improved version of the existing in-line high quality, draw tower fibre Bragg gratings (DTG®s). With respect to accurate measurements and structural integrity, the research focuses on reducing the total diameter of the optical fibre, so the incorporation in the reinforcement fibres is enhanced and the distortion in the composite is reduced. The author elaborates in detail the methods of strain and temperature calibrations and the different setups which are applied. Additionally, with respect to the high temperatures during the composite manufacturing process, the thermal stability of the DTG®s is studied at elevated temperatures (>300°C).
In the second part, the author embeds the DTG®s in specific types of thermoset and thermoplastic carbon reinforced plastic laminates. The author applies the embedded DTG®s in several stages of the composite lifetime. Starting with the monitoring of the composite manufacturing process and ending with fatigue testing until failure of the composite laminates. During the different experiments, the sensors are subjected to high temperatures, high pressures, extreme longitudinal strains and transverse strains and in the mean time, they are employed to very accurately measure (multi-axial) strains inside composites at microstrain level (~10 6)
- …