2,960 research outputs found
The Wareham Hotel: adaptive use of a Manhattan, Kansas landmark
Call number: LD2668 .R4 1986 N45Master of Regional and Community Plannin
An approximate buckling analysis for rectangular orthotropic plates with centrally located cutouts
An approximate analysis for predicting buckling of rectangular orthotropic composite plates with centrally located cutouts is presented. In this analysis, prebuckling and buckling problems are converted from a two-dimensional to a one-dimensional system of linear differential equations with variable coefficients. The conversion is accomplished by expressing the displacements as series with each element containing a trigonometric function of one coordinate and a coefficient that is an arbitrary function of the other coordinate. Ordinary differential equations are then obtained from a variational principle. Analytical results obtained from the approximate analysis are compared with finite element analyses for isotropic plates and for specially orthotropic plates with central circular cutouts of various sizes. Experimental results for the specially orthotropic plates are also presented. In nearly all cases, the approximate analysis predicts the buckling mode shapes correctly and predicts the buckling loads to within a few percent of the finite element and experimental results
Nonlinear shell analyses of the space shuttle solid rocket boosters
A variety of structural analyses have been performed on the Solid Rocket Boosters (SRB's) to provide information that would contribute to the understanding of the failure which destroyed the Space Shuttle Challenger. This paper describes nonlinear shell analyses that were performed to characterize the behavior of an overall SRB structure and a segment of the SRB in the vicinity of the External Tank Attachment (ETA) ring. Shell finite element models were used that would accurately reflect the global load transfer in an SRB in a manner such that nonlinear shell collapse and ovalization could be assessed. The purpose of these analyses was to calculate the overall deflection and stress distributions for these SRB models when subjected to mechanical loads corresponding to critical times during the launch sequence. Static analyses of these SRB models were performed using a snapshot picture of the loads. Analytical results obtained using these models show no evidence of nonlinear shell collapse for the pre-liftoff loading cases considered
Preliminary 2-D shell analysis of the space shuttle solid rocket boosters
A two-dimensional shell model of an entire solid rocket booster (SRB) has been developed using the STAGSC-1 computer code and executed on the Ames CRAY computer. The purpose of these analyses is to calculate the overall deflection and stress distributions for the SRB when subjected to mechanical loads corresponding to critical times during the launch sequence. The mechanical loading conditions for the full SRB arise from the external tank (ET) attachment points, the solid rocket motor (SRM) pressure load, and the SRB hold down posts. The ET strut loads vary with time after the Space Shuttle main engine (SSME) ignition. The SRM internal pressure varies axially by approximately 100 psi. Static analyses of the full SRB are performed using a snapshot picture of the loads. The field and factory joints are modeled by using equivalent stiffness joints instead of detailed models of the joint. As such, local joint behavior cannot be obtained from this global model
Stress Analysis of Composite Cylindrical Shells with an Elliptical Cutout
A special-purpose, semi-analytical solution method for determining the stress and deformation fields in a thin laminated-composite cylindrical shell with an elliptical cutout is presented. The analysis includes the effects of cutout size, shape, and orientation; non-uniform wall thickness; oval-cross-section eccentricity; and loading conditions. The loading conditions include uniform tension, uniform torsion, and pure bending. The analysis approach is based on the principle of stationary potential energy and uses Lagrange multipliers to relax the kinematic admissibility requirements on the displacement representations through the use of idealized elastic edge restraints. Specifying appropriate stiffness values for the elastic extensional and rotational edge restraints (springs) allows the imposition of the kinematic boundary conditions in an indirect manner, which enables the use of a broader set of functions for representing the displacement fields. Selected results of parametric studies are presented for several geometric parameters that demonstrate that analysis approach is a powerful means for developing design criteria for laminated-composite shells
Hot subdwarf stars and their connection to thermonuclear supernovae
Hot subdwarf stars (sdO/Bs) are evolved core helium-burning stars with very
thin hydrogen envelopes, which can be formed by common envelope ejection. Close
sdB binaries with massive white dwarf (WD) companions are potential progenitors
of thermonuclear supernovae type Ia (SN Ia). We discovered such a progenitor
candidate as well as a candidate for a surviving companion star, which escapes
from the Galaxy. More candidates for both types of objects have been found by
crossmatching known sdB stars with proper motion and light curve catalogues.
The Gaia mission will provide accurate astrometry and light curves of all the
stars in our hot subdwarf sample and will allow us to compile a much larger
all-sky catalogue of those stars. In this way we expect to find hundreds of
progenitor binaries and ejected companions.Comment: Proceedings of the 11th Pacific Rim Conference on Stellar
Astrophysics, Hong Kong 2015, Journal of Physics: Conference Series, in pres
Revised Coordinates and Proper Motions of the Stars in the Luyten Half-Second Catalogue
We present refined coordinates and proper motion data for the high proper
motion (HPM) stars in the Luyten Half-Second (LHS) catalogue. The positional
uncertainty in the original Luyten catalogue is typically >10" and is often
>30". We have used the digital scans of the Palomar Observatory Sky Survey
(POSS) I and POSS II plates to derive more accurate positions and proper
motions of the objects. Out of the 4470 candidates in the LHS catalogue, 4323
objects were manually re-identified in the POSS I and POSS II scans. A small
fraction of the stars were not found due to the lack of finder charts and
digitized POSS II scans. The uncertainties in the revised positions are
typically ~2", but can be as high as ~8" in a few cases; this is a large
improvement over the original data. Cross-correlation with the Tycho-2 and
Hipparcos catalogues yielded 819 candidates (with m_R < 12). For these brighter
sources, the position and proper motion data have been replaced with the more
accurate Tycho/Hipparcos data. In total, we have revised proper motion
measurements and coordinates for 4040 stars and revised coordinates for 4330
stars, which are presented here.Comment: 108 pages. Accepted for Publication in ApJ Suppl. Some errors caused
by the transcription errors in the original LHS catalogue have been corrected
in this resubmission. The most current version of the catalogue is also
available online at http://www.stsci.edu/~ksahu/lh
The orbits of subdwarf-B + main-sequence binaries. II. Three eccentric systems; BD+29 3070, BD +34 1543 and Feige 87
The predicted orbital-period distribution of the subdwarf-B (sdB) population
is bi-modal with a peak at short ( 250 days) periods.
Observationally, many short-period sdB systems are known, but the predicted
long period peak is missing as orbits have only been determined for a few
long-period systems. As these predictions are based on poorly understood
binary-interaction processes, it is of prime importance to confront the
predictions with reliable observational data. We therefore initiated a
monitoring program to find and characterize long-period sdB stars. In this
paper we aim to determine the orbital parameters of the three long-period
sdB+MS binaries BD+29 3070, BD+34 1543 and Feige 87, to constrain their
absolute dimensions and the physical parameters of the components.
High-resolution spectroscopic time series were obtained with HERMES at the
Mercator telescope on La Palma, and analyzed to determine the radial velocities
of both the sdB and MS components. Photometry from the literature was used to
construct the spectral-energy distribution (SED) of the binaries. Atmosphere
models were used to fit these SEDs and to determine the surface gravities and
temperatures of both components of all systems. Spectral analysis was used to
check the results of the SEDs. An orbital period of 1283 +- 63 d, a mass ratio
of q = 0.39 +- 0.04 and a significant non-zero eccentricity of e = 0.15 +- 0.01
were found for BD+29 3070. For BD+34 1543 we determined P = 972 +- 2 d, q =
0.57 +- 0.01 and again a clear non-zero eccentricity of e = 0.16 +- 0.01. Last,
for Feige 87 we found P = 936 +- 2 d, q = 0.55 +- 0.01 and e = 0.11 +- 0.01.
BD+29 3070, BD+34 1543 and Feige 87 are long period sdB + MS binaries on
clearly eccentric orbits. These results are in conflict with the predictions of
stable Roche-lobe overflow models.Comment: 15 pages, 6 figures, Accepted by A&
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