Resonant and Antiresonant Frequencies of Thick Disks and Thick Rods

1968 ◽  
Vol 43 (6) ◽  
pp. 1324-1328 ◽  
Author(s):  
George K. Lucey
Keyword(s):  
Thick Disks ◽  
Resonant And Antiresonant Frequencies

scholarly journals Exact general relativistic thick disks

2004 ◽  
Vol 69 (4) ◽  
Author(s):  
Guillermo A. González ◽  
Patricio S. Letelier
Keyword(s):  
General Relativistic ◽  
Thick Disks

scholarly journals Clumpy Galaxies in the Early Universe

2006 ◽  
Vol 2 (S235) ◽  
pp. 376-380 ◽  
Author(s):  
Debra Meloy Elmegreen
Keyword(s):  
Star Formation ◽  
Early Universe ◽  
Spiral Galaxies ◽  
Star Forming ◽  
Wide Range ◽  
Thick Disks ◽  
Hubble Ultra Deep Field

AbstractClumpy galaxies are prominent in the early Universe. We present morphological and photometric properties of a wide range of galaxy types and their star-forming clumps in the Hubble Ultra Deep Field. Sizes, scale lengths, and scale heights suggest that galaxies grow by a factor of 2 fromz= 4 to the present, and that thick disks are present in the early Universe. The largest clumps of star formation are 107–109M⊙in different galaxies, much more massive than large star-forming complexes in local galaxies. Dissolved clumps may account for both the exponential disks and the early thick disks of spirals and proto-spiral galaxies.

High pressure combustion synthesis of aluminum nitride

1991 ◽  
Vol 6 (11) ◽  
pp. 2397-2402 ◽  
Author(s):  
Marc Costantino ◽  
Carlo Firpo
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Aluminum Nitride ◽  
Combustion Synthesis ◽  
Theoretical Density ◽  
High Porosity ◽  
Thick Disks ◽  
Initial Results

We report initial results on the synthesis of monolithic aluminum nitride by burning Al–AlN mixtures in high pressure nitrogen. The objective is to synthesize economically large, near-theoretical density AlN parts. In this work, we begin with compacted mixtures of 10 μm Al and 3 μm AlN powder formed into 7.62 cm diameter by 3.81 cm thick disks having densities up to 60% of theoretical. Then, at N2 pressures up to 180 MPa (26 000 psi), we ignite the disk on one face. The fraction of Al converted to AlN, density, and severity of macroscopic cracking vary with N2 pressure and heat transfer from the sample. Presently, products are inhomogeneous, showing regions of relatively high porosity, regions with no porosity but with AlN in a matrix of Al, and regions of nearly theoretical density AlN.

scholarly journals Kinematical & Chemical Characteristics of the Thin and Thick Disks

2008 ◽  
Vol 4 (S254) ◽  
pp. 179-190 ◽  
Author(s):  
Rosemary F. G. Wyse
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Observational Evidence ◽  
Chemical Characteristics ◽  
Chemical Abundance ◽  
The Galaxy ◽  
History Of ◽  
Thin And Thick Disks ◽  
Thick Disks

AbstractI discuss how the chemical abundance distributions, kinematics and age distributions of stars in the thin and thick disks of the Galaxy can be used to decipher the merger history of the Milky Way, a typical large galaxy. The observational evidence points to a rather quiescent past merging history, unusual in the context of the ‘consensus’ cold-dark-matter cosmology favoured from observations of structure on scales larger than individual galaxies.

Estimation of Distributed Unbalance of Rotors

2001 ◽  
Author(s):  
Tachung Yang ◽  
Chunyi Lin
Keyword(s):  
Finite Element ◽  
Singular Value Decomposition ◽  
Element Model ◽  
Singular Value ◽  
Lumped Mass ◽  
Piecewise Polynomials ◽  
Mass Unbalance ◽  
Thick Disks ◽  
Value Decomposition ◽  
Thin Disks

Mass unbalance commonly causes vibration of rotor-bearing systems. Lumped mass modeling of unbalance was adapted in most previous research. The lumped unbalance assumption is adequate for thin disks or impellers, but not for thick disks or shafts. Lee et al. (1993) proposed that the unbalance of shafts should be continuously distributed. Balancing methods based on discrete unbalance models may not be very appropriate for rotors with distributed unbalance. A better alternative is to identify the distributed unbalance of shafts before balancing. In this study, the eccentricity distribution of the shaft is assumed in piecewise polynomials. A finite element model for the distributed unbalance is provided. Singular value decomposition is used to identify the eccentricity curves of the rotor. Numerical validation of this method is presented and examples are given to show the effectiveness of the identification method.

Thick Disks?

Science News ◽  
1984 ◽  
Vol 125 (18) ◽  
pp. 275
Author(s):  
John R. Gustafson
Keyword(s):  
Thick Disks

scholarly journals ON THE FORMATION OF GALACTIC THICK DISKS

2015 ◽  
Vol 804 (1) ◽  
pp. L9 ◽  
Author(s):  
I. Minchev ◽  
M. Martig ◽  
D. Streich ◽  
C. Scannapieco ◽  
R. S. de Jong ◽  
...  
Keyword(s):  
Thick Disks

scholarly journals The chemical fingerprints of the thin and the thick disk

2008 ◽  
Vol 4 (S254) ◽  
pp. 197-202
Author(s):  
Sofia Feltzing ◽  
Sally Oey ◽  
Thomas Bensby
Keyword(s):  
Past History ◽  
Thick Disk ◽  
Chemical Abundance ◽  
Dwarf Stars ◽  
Abundance Patterns ◽  
The Galaxy ◽  
Thin And Thick Disks ◽  
Thick Disks ◽  
Definition Of ◽  
Galactic Stellar Populations

AbstractThe past history and origin of the different Galactic stellar populations are manifested in their different chemical abundance patterns. We obtained new elemental abundances for 553 F and G dwarf stars, to more accurately quantify these patterns for the thin and thick disks. However, the exact definition of disk membership is not straightforward. Stars that have a high likelihood of belonging to the thin disk show different abundance patterns from those for the thick disk. In contrast, we show that stars for the Hercules Stream do not show unique abundance patterns, but rather follow those of the thin and thick disks. This strongly suggests that the Hercules Stream is a feature induced by internal dynamics within the Galaxy rather than the remnant of an accreted satellite.

scholarly journals Twodimensional Axialsymmetrical Hydrodynamical Simulations of PN-Evolution

1993 ◽  
Vol 155 ◽  
pp. 373-373
Author(s):  
J. Zweigle ◽  
M. Bremer ◽  
M. Grewing
Keyword(s):  
Numerical Method ◽  
Central Star ◽  
Density Contrast ◽  
Initial Model ◽  
Cylindrical Coordinates ◽  
Model Parameter ◽  
Thick Disks ◽  
Red Giant ◽  
Hydrodynamical Simulations ◽  
Key Parameter

In order to investigate the early evolution of planetary nebulae (PNe) we solved numerically the hydrodynamical equations in cylindrical coordinates (r, z) assuming azimutal symmetry. The numerical method used is described in detail by Mair et al. (1988). Our simulations model the interaction of a fast, tenuous, spherical symmetrical central star wind with a slow, dense, aspherical Red Giant Envelope (RGE) expelled from the progenitor star. For the aspherical RGE with a polar/equatorial density contrast we used the initial model given by Mellema et al. (1991) in cylindrical coordinates. We have investigated the influence of each initial model parameter upon the evolution of PNe. Thereby we confirm that the polar/equatorial density contrast in the RGE and the thickness of the RGE-disk play an important role for the morphology of PNe. In agreement with the results from Mellema et al. (1991). The polar/equatorial density contrast in the RGE influences the ratio of the distances of the bright inner rim to the central star in z- and r-direction. This ratio increases with decreasing polar/equatorial density contrast. We find the thickness of the RGE-disk to be a key parameter for getting an elliptical or a butterfly PN: thin RGE-disks produce the first type of nebulae, thick disks the latter. We thank G. Mair, E. Müller and W. Hillebrandt for making available to us a copy of the SADIE code.

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