1,416 research outputs found
Cosmology-Independent Distance Moduli of 42 Gamma-Ray Bursts between Redshift of 1.44 and 6.60
This report is an update and extension of our paper accepted for publication
in ApJ (arXiv:0802.4262). Since objects at the same redshift should have the
same luminosity distance and the distance moduli of type Ia supernovae (SNe Ia)
obtained directly from observations are completely cosmology independent, we
obtain the distance modulus of a gamma-ray burst (GRB) at a given redshift by
interpolating or iterating from the Hubble diagram of SNe Ia. Then we calibrate
five GRB relations without assuming a particular cosmological model, from
different regression methods, and construct the GRB Hubble diagram to constrain
cosmological parameters. Based upon these relations we list the
cosmology-independent distance moduli of 42 GRBs between redshift of 1.44 and
6.60, with the 1- uncertainties of 1-3%.Comment: 6 pages, 2 figures, 3 tables. To appear in the proceedings of "2008
Nanjing GRB conference", Nanjing, 23-27 June 200
GRO J1655-40: from ASCA and XMM-Newton Observations
We have analysed four ASCA observations (1994--1995, 1996--1997) and three
XMM-Newton observations (2005) of this source, in all of which the source is in
high/soft state. We modeled the continuum spectra with relativistic disk model
kerrbb, estimated the spin of the central black hole, and constrained the
spectral hardening factor f_col and the distance. If kerrbb model applies, for
normally used value of f_col, the distance cannot be very small, and f_col
changes with observations.Comment: 2 pages, 1 figure, Conference proceedings to appear in "The Central
Engine of Active Galactic Nuclei", ed. L. C. Ho and J.-M. Wang (San
Francisco: ASP
Study on Distortional Buckling of Cold-Formed Stainless Steel Beams
In the current research, distortional buckling of cold-formed stainless steel open-section beams was investigated. Four-point bending tests of eight C-section stainless steel beams, made of S30401 alloy, were carried out with global and local buckling precluded by careful design of specimen and test rigs. A detailed finite element model based on ABAQUS was developed and verified against test data. Parametric study was carried out with the verified model, covering four types of sections (C, Z, SupaCee, and SupaZed), three stainless steel alloys (S30401, S44330, S32101), and a series of section slenderness. A convenient method to identify distortional buckling point in either experimental or numerical study was discussed. Existing design formula for stainless steel and steel structure were assessed with the available data. Revised formula based on Direct Strength Method was proposed
A Preliminary Study on Stainless Steel Hollow Flange Beams Featuring Lateral-Distortional Buckling
To explore the potential of using stainless steel structurally, extensive research has been carried out to study the structural behavior of stainless steel member as associated with the nonlinear stress-strain relationship. Hollow flange sections feature improved structural efficiency and a unique issue of web distortion. Steel hollow flange sections have been studied and commercially distributed (e.g. the very first HFB section and lately LSB section). As a proactive study, this paper investigates stainless steel hollow flange beams of double-symmetric section with numerical modeling and parametric analysis. The validity of the idealized FE model was verified with existing study on steel counterparts. Specifically, three alloys (S30401, S44330, S32101) and a series of sections and membe
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