467 research outputs found
Effective Width of Floor Systems for Application in Seismic Analysis
Effective width coefficients for floor systems have been developed for use
in the analysis of frames subjected to lateral seismic loads. The results cover
a wide range of the governing nondimensional parameters, and are applicable to
floor slabs with supporting beams as well as to flat slabs.
The effective width coefficients were derived from a parametric study of
typical interior panels of floor systems using elastic finite element analysis.
An example of the application of the use of the results in seismic analysis
of low-rise building frames is presented.National Science Foundation Grants ENV 77-07190 and PFR 80-0258
Constraints on Initial AHS Deployment and the Concept Definition of a Shuttle Service for AHS Debut
Highway automation and its evolution involve a multitude of systems issues. Particularly important and difficult in defining a deployment sequence is the very first step, i.e. the first user service involving fully automated freeway driving. However, this importance and the difficulty imply that many factors may severely constrain the initial deployment. After discussing the paramount importance of initial AHS deployment, this paper points out major high-level issues and constraints. Any realistic deployment strategy must take into consideration gradual technology maturation, introduction of new driver role and diminishing conventional driver role for automated driving, high cost of early-generation automation-equipped vehicles, gradual infrastructure modification, gradual commitment of automakers to manufacture and service automation-equipped vehicles, gradual commitment of insurance industry to carry liability, and gradual acceptance by the interest groups and the general public. This paper then proposes a freeway shuttle van service for AHS debut. This user service could be a good candidate for the 1997 AHS demonstration required by ISTEA and has a good chance of leading to a successful long-term AHS deployment supported by the general public
Energy band structure and intrinsic coherent properties in two weakly linked Bose Einstein Condensates
The energy band structure and energy splitting due to quantum tunneling in
two weakly linked Bose-Einstein condensates were calculated by using the
instanton method. The intrinsic coherent properties of Bose Josephson junction
were investigated in terms of energy splitting. For , the
energy splitting is small and the system is globally phase coherent. In the
opposite limit, , the energy splitting is large and the
system becomes a phase dissipation. Our reslults suggest that one should
investigate the coherence phenomna of BJJ in proper condition such as
.Comment: to appear in Phys. Rev. A, 2 figure
Entangled quantum tunneling of two-component Bose-Einstein condensates
We examine the quantum tunneling process in Bose condensates of two
interacting species trapped in a double well configuration. We discover the
condition under which particles of different species can tunnel as pairs
through the potential barrier between two wells in opposition directions. This
novel form of tunneling is due to the interspecies interaction that eliminates
the self- trapping effect. The correlated motion of tunneling atoms leads to
the generation of quantum entanglement between two macroscopically coherent
systems.Comment: 4 pages, 3 figure
Quasi-spin Model for Macroscopic Quantum Tunnelling between Two Coupled Bose-Einstein Condensates
The macroscopic quantum tunneling between two coupled Bose-Einstein
condensates (BEC) (radio-frequency coupled two-component BECs or two BECs
confined in a double-well potential) is mapped onto the tunneling of an
uniaxial spin with an applied magnetic field. The tunneling exponent is
calculated with an imaginary-time path-integral method. In the limit of low
barrier, the dependence of tunneling exponent on the system parameters is
obtained, and the crossover temperature from thermal regime to quantum regime
is estimated. The detailed information about the tunnelling will give help to
control population conversion between coupled BECs and realize quantum
computation with coupled BECs.Comment: 20 pages, 4 figures, accepted by Phys.Rev.
Dynamics of a large extra dimension inspired hybrid inflation model
In low scale quantum gravity scenarios the fundamental scale of nature can be
as low as TeV, in order to address the naturalness of the electroweak scale. A
number of difficulties arise in constructing specific models; stabilisation of
the radius of the extra dimensions, avoidance of overproduction of Kaluza Klein
modes, achieving successful baryogenesis and production of a close to
scale-invariant spectrum of density perturbations with the correct amplitude.
We examine in detail the dynamics, including radion stabilisation, of a hybrid
inflation model that has been proposed in order to address these difficulties,
where the inflaton is a gauge singlet residing in the bulk. We find that for a
low fundamental scale the phase transition, which in standard four dimensional
hybrid models usually ends inflation, is slow and there is second phase of
inflation lasting for a large number of e-foldings. The density perturbations
on cosmologically interesting scales exit the Hubble radius during this second
phase of inflation, and we find that their amplitude is far smaller than is
required. We find that the duration of the second phase of inflation can be
short, so that cosmologically interesting scales exit the Hubble radius prior
to the phase transition, and the density perturbations have the correct
amplitude, only if the fundamental scale takes an intermediate value. Finally
we comment briefly on the implications of an intermediate fundamental scale for
the production of primordial black holes and baryogenesis.Comment: 9 pages, 2 figures version to appear in Phys. Rev. D, additional
references and minor changes to discussio
Nonlinear ion-acoustic (IA) waves driven in a cylindrically symmetric flow
By employing a self-similar, two-fluid MHD model in a cylindrical geometry,
we study the features of nonlinear ion-acoustic (IA) waves which propagate in
the direction of external magnetic field lines in space plasmas. Numerical
calculations not only expose the well-known three shapes of nonlinear
structures (sinusoidal, sawtooth, and spiky or bipolar) which are observed by
numerous satellites and simulated by models in a Cartesian geometry, but also
illustrate new results, such as, two reversely propagating nonlinear waves,
density dips and humps, diverging and converging electric shocks, etc. A case
study on Cluster satellite data is also introduced.Comment: accepted by AS
Neutrino Masses, Mixing and New Physics Effects
We introduce a parametrization of the effects of radiative corrections from
new physics on the charged lepton and neutrino mass matrices, studying how
several relevant quantities describing the pattern of neutrino masses and
mixing are affected by these corrections. We find that the ratio omega = sin
theta / tan theta_atm is remarkably stable, even when relatively large
corrections are added to the original mass matrices. It is also found that if
the lightest neutrino has a mass around 0.3 eV, the pattern of masses and
mixings is considerably more stable under perturbations than for a lighter or
heavier spectrum. We explore the consequences of perturbations on some flavor
relations given in the literature. In addition, for a quasi-degenerate neutrino
spectrum it is shown that: (i) starting from a bi-maximal mixing scenario, the
corrections to the mass matrices keep tan theta_atm very close to unity while
they can lower tan theta_sol to its measured value; (ii) beginning from a
scenario with a vanishing Dirac phase, corrections can induce a Dirac phase
large enough to yield CP violation observable in neutrino oscillations.Comment: 14 pages, 21 figures. Uses RevTeX4. Added several comments and
references. Final version to appear in PR
Questionnaire-Based Polyexposure Assessment Outperforms Polygenic Scores for Classification of Type 2 Diabetes in a Multiancestry Cohort
OBJECTIVE Environmental exposures may have greater predictive power for type 2 diabetes than polygenic scores (PGS). Studies examining environmental risk factors, however, have included only individuals with European ancestry, limiting the applicability of results. We conducted an exposome-wide association study in the multiancestry Personalized Environment and Genes Study to assess the effects of environmental factors on type 2 diabetes. RESEARCH DESIGN AND METHODS Using logistic regression for single-exposure analysis, we identified exposures associated with type 2 diabetes, adjusting for age, BMI, household income, and self-reported sex and race. To compare cumulative genetic and environmental effects, we computed an overall clinical score (OCS) as a weighted sum of BMI and prediabetes, hyperten-sion, and high cholesterol status and a polyexposure score (PXS) as a weighted sum of 13 environmental variables. Using UK Biobank data, we developed a multiancestry PGS and calculated it for participants. RESULTS We found 76 significant associations with type 2 diabetes, including novel associations of asbestos and coal dust exposure. OCS, PXS, and PGS were significantly associated with type 2 diabetes. PXS had moderate power to determine associations, with larger effect size and greater power and reclassification improvement than PGS. For all scores, the results differed by race. CONCLUSIONS Our findings in a multiancestry cohort elucidate how type 2 diabetes odds can be at-tributed to clinical, genetic, and environmental factors and emphasize the need for exposome data in disease-risk association studies. Race-based differences in predictive scores highlight the need for genetic and exposome-wide studies in diverse populations. EmR2TaFJ
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