Wrapping layered graphs

We present additions to the widely-used layout method for directed acyclic graphs of Sugiyama et al. [16] that allow to better utilize a prescribed drawing area. The method itself partitions the graph's nodes into layers. When drawing from top to bottom, the number of layers directly impacts the height of a resulting drawing and is bound from below by the graph's longest path. As a consequence, the drawings of certain graphs are significantly taller than wide, making it hard to properly display them on a medium such as a computer screen without scaling the graph's elements down to illegibility. We address this with the Wrapping Layered Graphs Problem (WLGP), which seeks for cut indices that split a given layering into chunks that are drawn side-by-side with a preferably small number of edges wrapping backwards. Our experience and a quantitative evaluation indicate that the proposed wrapping allows an improved presentation of narrow graphs, which occur frequently in practice and of which the internal compiler representation SCG is one example

Face pairing graphs and 3-manifold enumeration

The face pairing graph of a 3-manifold triangulation is a 4-valent graph denoting which tetrahedron faces are identified with which others. We present a series of properties that must be satisfied by the face pairing graph of a closed minimal P^2-irreducible triangulation. In addition we present constraints upon the combinatorial structure of such a triangulation that can be deduced from its face pairing graph. These results are then applied to the enumeration of closed minimal P^2-irreducible 3-manifold triangulations, leading to a significant improvement in the performance of the enumeration algorithm. Results are offered for both orientable and non-orientable triangulations.Comment: 30 pages, 57 figures; v2: clarified some passages and generalised the final theorem to the non-orientable case; v3: fixed a flaw in the proof of the conical face lemm

Evaluation of Damaged Concrete Members Strengthened with CFRP-Epoxy and HFRP Polyurethane Systems

Fiber reinforced polymer (FRP) composite materials offer economical solutions to repair and rehabilitate the aging civil infrastructure at a fraction of the huge replacement cost. Glass and carbon FRP fabrics, bars, and shapes have been field implemented for the construction and rehabilitation of reinforced concrete (RC) structures. This research work aims at evaluating the mechanical and bond properties of Fiber Reinforced Polymer (FRP) composites for concrete structural applications. Both CFRP and Hybrid Carbon/Glass FRP (HFRP) have been investigated for repair and rehabilitation of civil infrastructure constructed of concrete. Concrete cylinders of different compressive strengths were tested with 1, 2, and 3 layers of confining CFRP and HFRP wraps. Similarly, split-bonded cylinders with adhesive bonding representing cracked and repaired concrete columns were also tested. In addition to cylinder testing, CFRP and HFRP wrapped concrete beams with varying types of damage were tested to find the wrap effectiveness, structural behavior, and flexural strength gains. Analytical modeling results for both concrete cylinders and beams were compared with the experimental results. Results show that both the fabric systems are effective in providing the necessary bond strength, confinement effects and flexural strength enhancement

Random percolation as a gauge theory

Three-dimensional bond or site percolation theory on a lattice can be interpreted as a gauge theory in which the Wilson loops are viewed as counters of topological linking with random clusters. Beyond the percolation threshold large Wilson loops decay with an area law and show the universal shape effects due to flux tube quantum fluctuations like in ordinary confining gauge theories. Wilson loop correlators define a non-trivial spectrum of physical states of increasing mass and spin, like the glueballs of ordinary gauge theory. The crumbling of the percolating cluster when the length of one periodic direction decreases below a critical threshold accounts for the finite temperature deconfinement, which belongs to 2-D percolation universality class.Comment: 20 pages, 14 figure

Automatic Layout of Data Flow Diagrams in KIELER and Ptolemy II

Data flow diagrams are successfully applied in the area of model-based design of complex embedded systems. However, their creation and maintenance can be very time-consuming, because many tools offer little support for the editing and visualization of graphical models. The KIELER project explores new concepts for the pragmatics of graphical modeling and develops algorithms for automatic layout of specific classes of diagrams. These concepts and algorithms are implemented as extensions of the Eclipse framework, which offers generic approaches to create IDEs for graphical modeling. We have developed a specialized layout algorithm for data flow diagrams. In addition to the embedding in KIELER, we applied this algorithm to Ptolemy, a framework for research on models of computation for use in embedded systems. The results show that our algorithm is well suited for the actor oriented diagrams of Ptolemy, and it can serve as a basis to facilitate the editing of Ptolemy diagrams

High-speed IPM Motors with Rotor Sleeve: Structural Design and Performance Evaluation

This paper deals with the structural design of sleeves for high-speed interior permanent magnet (IPM) synchronous machines. Wrapped IPM (WIPM) motors are a new player in the field of high-speed e-machines for traction, where a retaining sleeve is used to hold the magnetic poles in place against centrifugal forces, replacing the role of conventional iron bridges. The wrapping technique, originating from surface-mounted permanent magnet rotors, is believed to push speed limitations to new heights, as demanded by the increasing requirements of the automotive industry. By developing an equivalent rotor geometry of the WIPM rotor, an analytical model is formulated to evaluate the stress in the rotor and to provide a quick and intuitive tool for the sleeve design. The results are successfully validated by structural finite element analysis. Also, the output figures of a WIPM machine are compared to those of an equivalent IPM machine with iron bridges

Robust Multilayer Insulation for Cryogenic Systems

New requirements for thermal insulation include robust Multilayer insulation (MU) systems that work for a range of environments from high vacuum to no vacuum. Improved MLI systems must be simple to install and maintain while meeting the life-cycle cost and thermal performance objectives. Performance of actual MLI systems has been previously shown to be much worse than ideal MLI. Spacecraft that must contain cryogens for both lunar service (high vacuum) and ground launch operations (no vacuum) are planned. Future cryogenic spacecraft for the soft vacuum environment of Mars are also envisioned. Industry products using robust MLI can benefit from improved cost-efficiency and system safety. Novel materials have been developed to operate as excellent thermal insulators at vacuum levels that are much less stringent than the absolute high vacuum requirement of current MLI systems. One such robust system, Layered Composite Insulation (LCI), has been developed by the Cryogenics Test Laboratory at NASA Kennedy Space Center. The experimental testing and development of LCI is the focus of this paper. LCI thermal performance under cryogenic conditions is shown to be six times better than MLI at soft vacuum and similar to MLI at high vacuum. The experimental apparent thermal conductivity (k-value) and heat flux data for LCI systems are compared with other MLI systems