Flow Induced Spring Coefficients of Labyrinth Seals for Application in Rotor Dynamics

Flow induced aerodynamic spring coefficients of labyrinth seals are discussed and the restoring force in the deflection plane of the rotor and the lateral force acting perpendicularly to it are also considered. The effects of operational conditions on the spring characteristics of these components are examined, such as differential pressure, speed, inlet flow conditions, and the geometry of the labyrinth seals. Estimation formulas for the lateral forces due to shaft rotation and inlet swirl, which are developed through experiments, are presented. The utilization of the investigations is explained and results of stability calculations, especially for high pressure centrifugal compressors, are added. Suggestions are made concerning the avoidance of exciting forces in labyrinths

Mechanisms for vestibular disorders in space flight. Facts and hypotheses

This article discusses the vestibular disorders associated with space flight. It is found there is still no complete understanding of the changes occurring in the sensory systems of the body during weightlessness. Results of studies are presented, including results of a ground model

Bending Frustration of Lipid-Water Mesophases Based on Cubic Minimal Surfaces

Inverse bicontinuous cubic phases are ubiquitous in lipid-water mixtures and consist of a lipid bilayer forming a cubic minimal surface, thereby dividing space into two cubic networks of water channels. For small hydrocarbon chain lengths, the monolayers can be modeled as parallel surfaces to a minimal midsurface. The bending energy of the cubic phases is determined by the distribution of Gaussian curvature over the minimal midsurfaces which we calculate for seven different structures (G, D, P, I-WP, C(P), S and F-RD). We show that the free-energy densities of the structures G, D and P are considerably lower than those of the other investigated structures due to their narrow distribution of Gaussian curvature. The Bonnet transformation between G, D, and P implies that these phases coexist along a triple line, which also includes an excess water phase. Our model includes thermal membrane undulations. Our qualitative predictions remain unchanged when higher order terms in the curvature energy are included. Calculated phase diagrams agree well with the experimental results for 2:1 lauric acid/dilauroyl phosphatidylcholine and water.Comment: Revtex, 23 pages with 9 postscript figures included, to appear in Langmui

Periodic minimal surfaces of cubic symmetry

A survey of cubic minimal surfaces is presented, based on the concept of fundamental surface patches and their relation to the asymmetric units of the space groups. The software Surface Evolver has been used to test for stability and to produce graphic displays. Particular emphasis is given to those surfaces that can be generated by a finite piece bounded by straight lines. Some new varieties have been found and a systematic nomenclature is introduced, which provides a symbol (a ‘gene’) for each triply-periodic minimal surface that specifies the surface unambiguously

The Labyrinth as Heart and Holder of Personal Pilgrimage

Labyrinths have woven a meandering path through the human psyche for thousands of years. From ancient Ariadne and Medieval cathedral pilgrimage floors to modern movies and computer games, labyrinths are often at the heart of the quest for self-knowledge, creative awakening, personal integration, community building and transcendence. The labyrinth as a metaphor for the journey of life could be considered a localized concentrated pilgrimage and alternative exploration to exotic travel and the physical challenge usually required for breakdown/breakthrough growth. Unicursal, single pathway designs, like the seven-circuit Classical Cretan and the eleven-circuit Chartres, engage the body while freeing the mind. The physical turnings of the path, alternating right and left, disorient so the walker must quickly surrender control of the experience and trust the journey. Most labyrinth walkers find themselves in a heightened state of receptive discovery very similar to pilgrimage. Walking the labyrinth in a state of focused contemplation while holding a question or an intention of quiet attentiveness is a core pilgrimage practice. Both can evoke an almost visceral recognition of one’s own truth, a profound surprise of the potential for reimagining one’s life as a coherent story of meaningful events and cohesive purpose. We are called to the journey. Walking the labyrinth as personal pilgrimage is a powerful practice to find our way home

Contact Instability in Adhesion and Debonding of Thin Elastic Films

Based on experiments and 3-D simulations, we show that a soft elastic film during adhesion and debonding from a rigid flat surface undergoes morphological transitions to pillars, labyrinths and cavities, all of which have the same lateral pattern length scale, close to \lambda/H ~ 3 for thick films, H > 1 micrometer. The linear stability analysis and experiments show a new thin film regime where \lambda/H \approx 3+ 2 (\gamma/3 \mu H)^(1/4) (\gamma is surface tension, \mu is shear modulus) because of significant surface energy penalty (for example, \lambda/H = 6 for H = 200 nm; \mu = 1MPa).Comment: Accepted for publication in Phys. Rev. Let

Modification of vestibular sensitivity in the rat

Vestibular sensitivity and associated locomotor responses of rats in rotating environmen