52,506 research outputs found
Dynamic Characteristics of Woodframe Buildings
The dynamic properties of wood shearwall buildings were evaluated, such as modal frequencies, damping and mode shapes of the structures. Through analysis of recorded earthquake response and by forced vibration testing, a database of periods and damping ratios of woodframe buildings was developed. Modal identification was performed on strong-motion records obtained from five buildings, and forced vibration tests were performed on a two-story house and a three-story apartment building, among others. A regression analysis is performed on the database to obtain a period formula specific for woodframe buildings. It should be noted that all test results, including the seismic data, are at small drift ratios (less than 0.1%), and the periods would be significantly longer for stronger shaking of these structures. Despite these low amplitudes, the equivalent viscous dampings for the fundamental modes were usually more than 10% of critical during earthquake shaking
Geometry and supersymmetry of heterotic warped flux AdS backgrounds
We classify the geometries of the most general warped, flux AdS backgrounds
of heterotic supergravity up to two loop order in sigma model perturbation
theory. We show under some mild assumptions that there are no
backgrounds with . Moreover the warp factor of AdS backgrounds is
constant, the geometry is a product and such solutions
preserve, 2, 4, 6 and 8 supersymmetries. The geometry of has been
specified in all cases. For 2 supersymmetries, it has been found that
admits a suitably restricted structure. For 4 supersymmetries, has
an structure and can be described locally as a circle fibration over a
6-dimensional KT manifold. For 6 and 8 supersymmetries, has an
structure and can be described locally as a fibration over a
4-dimensional manifold which either has an anti-self dual Weyl tensor or a
hyper-K\"ahler structure, respectively. We also demonstrate a new Lichnerowicz
type theorem in the presence of corrections.Comment: 34 pages. Reference adde
All Killing Superalgebras for Warped AdS Backgrounds
We present all the symmetry superalgebras of all warped
AdS, , flux backgrounds in dimensions
preserving any number of supersymmetries. First we give the conditions for
to decompose into a direct sum of the isometry algebra of
AdS and that of the internal space . Assuming this decomposition,
we identify all symmetry superalgebras of AdS backgrounds by showing that
the isometry groups of internal spaces act transitively on spheres. We
demonstrate that in type II and theories the AdS symmetry
superalgebras may not be simple and also present all symmetry superalgebras of
heterotic AdS backgrounds. Furthermore, we explicitly give the symmetry
superalgebras of AdS, , backgrounds and prove that they are all
classical.Comment: 41 pages, late
Red-giant stars in eccentric binaries
The unparalleled photometric data obtained by NASA’s Kepler Space Telescope has led to improved understanding of red-giant stars and binary stars. We discuss the characterization of known eccentric system, containing a solar-like oscillating red-giant primary component. We also report several new binary systems that are candidates for hosting an oscillating companion. A powerful approach to study binary stars is to combine asteroseimic techniques with light curve fitting. Seismology allows us to deduce the properties of red giants. In addition, by modeling the ellipsoidal modulations we can constrain the parameters of the binary system. An valuable independent source are ground-bases, high-resolution spectrographs
The Infrared Nucleus of the Wolf-Rayet Galaxy Henize 2-10
We have obtained near-infrared images and mid-infrared spectra of the
starburst core of the dwarf Wolf-Rayet galaxy He 2-10. We find that the
infrared continuum and emission lines are concentrated in a flattened ellipse
3-4'' or 150 pc across which may show where a recent accretion event has
triggered intense star formation. The ionizing radiation from this cluster has
an effective temperature of 40,000 K, corresponding to stars, and
the starburst is years old.Comment: 17 pages Latex, 7 postscript figures, 1 postscript table, accepted to
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Binary Decay of Light Nuclear Systems
A review of the characteristic features found in fully energy-damped,
binarydecay yields from light heavy-ion reactions with is presented. The different aspects of these yields that
have been used to support models of compound-nucleus (CN) fission and
deep-inelastic dinucleus orbiting are highlighted. Cross section calculations
based on the statistical phase space at different stages of the reaction are
presented and compared to the experimental results. Although the statistical
models are found to reproduce most of the observed experimental behaviors, an
additional reaction component corresponding to a heavy-ion resonance or
orbiting mechanism is also evident in certain systems. The system dependence of
this second component is discussed. The extent to which the binary yields in
very light systems can be viewed as resulting from a
fusion-fission mechanism is explored. A number of unresolved questions, such as
whether the different observed behaviors reflect characteristically different
reaction times, are discussed.Comment: 79 pages REVTeX file, 39 ps Figures included - to be publihed in
Physics Report
Phase II of the ASCE Benchmark Study on SHM
The task group on structural health monitoring of the Dynamic Committee of ASCE was formed in
1999 at the 12
th
Engineering Mechanics Conference. The task group has designed a number of analytical
studies on a benchmark structure and there are plans to follow these with an experimental program. The
first phase of the analytical studies was completed in 2001. The second phase, initiated in the summer of
2001, was formulated in the light of the experience gained on phase I and focuses on increasing realism in
the simulation of the discrepancies between the actual structure and the mathematical model used in the
analysis. This paper describes the rational that lead the SHM task group to the definition of phase II and
presents the details of the cases that are being considered
In situ correlative measurements for the ultraviolet differential absorption lidar and the high spectral resolution lidar air quality remote sensors: 1980 PEPE/NEROS program
In situ correlative measurements were obtained with a NASA aircraft in support of two NASA airborne remote sensors participating in the Environmental Protection Agency's 1980persistent elevated pollution episode (PEPE) and Northeast regional oxidant study (NEROS) field program in order to provide data for evaluating the capability of two remote sensors for measuring mixing layer height, and ozone and aerosol concentrations in the troposphere during the 1980 PEPE/NEROS program. The in situ aircraft was instrumented to measure temperature, dewpoint temperature, ozone concentrations, and light scattering coefficient. In situ measurements for ten correlative missions are given and discussed. Each data set is presented in graphical and tabular format aircraft flight plans are included
Developments in electromagnetic tomography instrumentation.
A new EMT sensor and instrumentation is described which combines the best features of previous systems and has a modular structure to allow for future system expansion and development
On the 2-categories of weak distributive laws
A weak mixed distributive law (also called weak entwining structure) in a
2-category consists of a monad and a comonad, together with a 2-cell relating
them in a way which generalizes a mixed distributive law due to Beck. We show
that a weak mixed distributive law can be described as a compatible pair of a
monad and a comonad, in 2-categories extending, respectively, the 2-category of
comonads and the 2-category of monads. Based on this observation, we define a
2-category whose 0-cells are weak mixed distributive laws. In a 2-category K
which admits Eilenberg-Moore constructions both for monads and comonads, and in
which idempotent 2-cells split, we construct a fully faithful 2-functor from
this 2-category of weak mixed distributive laws to K^{2 x 2}.Comment: 15 pages LaTeX source, final version to appear in Comm. Algebr
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