HPOTP low-speed flexible rotor balancing, phase 1

A method was developed that shows promise in overcoming many balancing limitations. This method establishes one or more windows for low speed, out-of-housing balancing of flexible rotors. These windows are regions of speed and support flexibility where two conditions are simultaneously fulfilled. First, the rotor system behaves flexibly; therefore, there is separation among balance planes. Second, the response due to balance weights is large enough to reliably measure. The analytic formulation of the low-speed flexible rotor balancing method is described. The results of proof-of-principle tests conducted under the program are presented. Based on this effort, it is concluded that low speed flexible rotor balancing is a viable technology. In particular, the method can be used to balance a rotor bearing system at low speed which results in smooth operation above more than one bending critical speed. Furthermore, this balancing methodology is applicable to SSME turbopump rotors

A Benchmark for Image Retrieval using Distributed Systems over the Internet: BIRDS-I

The performance of CBIR algorithms is usually measured on an isolated workstation. In a real-world environment the algorithms would only constitute a minor component among the many interacting components. The Internet dramati-cally changes many of the usual assumptions about measuring CBIR performance. Any CBIR benchmark should be designed from a networked systems standpoint. These benchmarks typically introduce communication overhead because the real systems they model are distributed applications. We present our implementation of a client/server benchmark called BIRDS-I to measure image retrieval performance over the Internet. It has been designed with the trend toward the use of small personalized wireless systems in mind. Web-based CBIR implies the use of heteroge-neous image sets, imposing certain constraints on how the images are organized and the type of performance metrics applicable. BIRDS-I only requires controlled human intervention for the compilation of the image collection and none for the generation of ground truth in the measurement of retrieval accuracy. Benchmark image collections need to be evolved incrementally toward the storage of millions of images and that scaleup can only be achieved through the use of computer-aided compilation. Finally, our scoring metric introduces a tightly optimized image-ranking window.Comment: 24 pages, To appear in the Proc. SPIE Internet Imaging Conference 200

Energy-stable linear schemes for polymer-solvent phase field models

We present new linear energy-stable numerical schemes for numerical simulation of complex polymer-solvent mixtures. The mathematical model proposed by Zhou, Zhang and E (Physical Review E 73, 2006) consists of the Cahn-Hilliard equation which describes dynamics of the interface that separates polymer and solvent and the Oldroyd-B equations for the hydrodynamics of polymeric mixtures. The model is thermodynamically consistent and dissipates free energy. Our main goal in this paper is to derive numerical schemes for the polymer-solvent mixture model that are energy dissipative and efficient in time. To this end we will propose several problem-suited time discretizations yielding linear schemes and discuss their properties

The Unevolved Main Sequence of Nearby Field Stars and the Open Cluster Distance Scale

The slope and zero-point of the unevolved main sequence as a function of metallicity are investigated using a homogeneous catalog of nearby field stars with absolute magnitudes defined with revised Hipparcos parallaxes, Tycho-2 photometry, and precise metallicities from high-dispersion spectroscopy. (B-V)-temperature relations are derived from 1746 stars between [Fe/H] = -0.5 and +0.6 and 372 stars within 0.05 dex of solar abundance; for T_e = 5770 K, the solar color is B-V= 0.652 +/- 0.002 (s.e.m.). From over 500 cool dwarfs between [Fe/H] = -0.5 and +0.5, Delta(B-V)/Delta[Fe/H] at fixed M_V = 0.213 +/- 0.005, with a very weak dependence upon the adopted main sequence slope with B-V at a given [Fe/H]. At Hyades metallicity this translates into Delta M_V/Delta[Fe/H] at fixed B-V = 0.98 +/- 0.02, midway between the range of values empirically derived from smaller and/or less homogeneous samples and model isochrones. From field stars of similar metallicity, the Hyades ([Fe/H] = +0.13) with no reddening has (m-M)_0 = 3.33 +/- 0.02 and M67, with E(B-V) = 0.041, A_V = 3.1E(B-V), and [Fe/H] = 0.00, has (m-M)_0 = 9.71 +/- 0.02 (s.e.m), where the errors quoted refer to internal errors alone. At the extreme end of the age and metallicity scale, with E(B-V) = 0.125 +/- 0.025 and [Fe/H] = +0.39 +/- 0.06, comparison of the fiducial relation for NGC 6791 to 19 field stars with (B-V) above 0.90 and [Fe/H] = +0.25 or higher, adjusted to the metallicity of NGC 6791, leads to (m-M)_0 = 13.07 +/- 0.09, internal and systematic errors included.Comment: 32 pages, 8 eps figures, latex; accepted for PAS

Isospin emission and flows at high baryon density: a test of the symmetry potential

High energy Heavy Ion Collisions (HIC) are studied in order to access nuclear matter properties at high density. Particular attention is paid to the selection of observables sensitive to the poorly known symmetry energy at high baryon density, of large fundamental interest, even for the astrophysics implications. Using fully consistent transport simulations built on effective theories we test isospin observables ranging from nucleon/cluster emissions to collective flows (in particular the elliptic, squeeze out, part). The effects of the competition between stiffness and momentum dependence of the Symmetry Potential on the reaction dynamics are thoroughly analyzed. In this way we try to shed light on the controversial neutron/proton effective mass splitting at high baryon and isospin densities. New, more exclusive, experiments are suggested.Comment: 10 pages, 16 figures, new figure added, accepted for publication in Phys.Rev.

Isospin emission and flows at high baryon density: a test of the symmetry potential

High energy Heavy Ion Collisions (HIC) are studied in order to access nuclear matter properties at high density. Particular attention is paid to the selection of observables sensitive to the poorly known symmetry energy at high baryon density, of large fundamental interest, even for the astrophysics implications. Using fully consistent transport simulations built on effective theories we test isospin observables ranging from nucleon/cluster emissions to collective flows (in particular the elliptic, squeeze out, part). The effects of the competition between stiffness and momentum dependence of the Symmetry Potential on the reaction dynamics are thoroughly analyzed. In this way we try to shed light on the controversial neutron/proton effective mass splitting at high baryon and isospin densities. New, more exclusive, experiments are suggested.Comment: 10 pages, 16 figures, new figure added, accepted for publication in Phys.Rev.

Achievable bisimilar behaviour of abstract state systems

Given a plant system and a desired system, we study conditions for which there exists a controller that interconnected with the plant, yields a system that is bisimilar to the desired system. Some sufficient and some necessary conditions are provided in the general case of (non-deterministic) abstract state systems and stronger results are obtained for the special classes of autonomous abstract state systems, finite abstract state systems, and non-deterministic linear dynamical systems

Identification of the Coronal Sources of the Fast Solar Wind

The present spectroscopic study of the ultraviolet coronal emission in a polar hole, detected on April 6-9, 1996 with the Ultraviolet Coronagraph Spectrometer aboard the SOHO spacecraft, identifies the inter-plume lanes and background coronal hole regions as the channels where the fast solar wind is preferentially accelerated. In inter-plume lanes, at heliocentric distance 1.7 \rsun, the corona expands at a rate between 105 km/s and 150 km/s, that is, much faster than in plumes where the outflow velocity is between 0 km/s and 65 km/s. The wind velocity is inferred from the Doppler dimming of the O VI $\lambda\lambda$ 1032, 1037 \AA lines, within a range of values, whose lower and upper limit corresponds to anisotropic and isotropic velocity distribution of the oxygen coronal ions, respectively.Comment: 14 pages, 4 figures, 3 tables, Accepted by ApJ Letter

Bisimulation theory for switching linear systems

A general notion of hybrid bisimulation is proposed and related to the notions of algebraic, state-space and input-output equivalences for the class of switching linear systems. An algebraic characterization of hybrid bisimulations and a procedure converging in a finite number of steps to the maximal hybrid bisimulation are derived. Bisimulation-based reduction and simulation-based abstraction are defined and characterized. Connections with observability are investigated