54,630 research outputs found
Remote sensor imagery in urban research - Some potentialities and problem
Imaging techniques of urban data collection for development and plannin
Sound separation probe
Probe separates sound waves from turbulent flow pressure fluctuations in ducted airstreams by using principle that sound waves and turbulent flow pressure perturbations travel at different velocities
Constraints on Hidden Photon Models from Electron g-2 and Hydrogen Spectroscopy
The hidden photon model is one of the simplest models which can explain the
anomaly of the muon anomalous magnetic moment (g-2). The experimental
constraints are studied in detail, which come from the electron g-2 and the
hydrogen transition frequencies. The input parameters are set carefully in
order to take dark photon contributions into account and to prevent the
analysis from being self-inconsistent. It is shown that the new analysis
provides a constraint severer by more than one order of magnitude than the
previous result.Comment: 18 pages, 2 figures, 1 table. v2: minor correction
Structural Analysis and Performance-Based Validation of a Composite Wing Spar
Electric-motor powered aircraft possess the ability to operate with efficient energy delivery, but lack the operational range of internal combustion engine powered aircraft. This range limitation requires the use of high aspect ratio, thin-chord wings to minimize aerodynamic drag losses, which results in highly loaded composite spar structures. High aspect ratio wings are required to increase mission durations for a NASA-developed experimental multi-rotor electric powered aircraft denoted as the Scalable Convergent Electric Propulsion Technology and Operations Research (SCEPTOR) or X-57. This paper examines the structural performance of the composite main wing spars to validate spar strength using ply-based laminate finite element methods. Geometric scaling of a main spar test-section was initially proposed for proof-testing but sacrificed stability. Ply-based structures modeling with local structural features was implemented as a risk-reduction methodology. Ply-based modeling was selected to augment the conventional building block approach to reduce risk, and leverage a performance-based approval processes encouraged in Federal Aviation Administration (FAA) design guidance. Therefore, ply-based laminate modeling of the full-scale main spar and forward spar shear-web attachments were subsequently undertaken to determine load path complexity with predicted flight loads. Ply-based modeling included stress concentrations and interlaminate behavior at interface locations that can be obscured in traditional finite element sizing models. Analysis of the wing spar laminate ply-based models compared with bearing test coupon performance was used to reduce future wing assembly proof-testing burden and facilitate performance-based flight hardware safety for the X-57 experimental aircraft
Geometric criticality between plaquette phases in integer-spin kagome XXZ antiferromagnets
The phase diagram of the uniaxially anisotropic antiferromagnet on the
kagom\'e lattice includes a critical line exactly described by the classical
three-color model. This line is distinct from the standard geometric classical
criticality that appears in the classical limit () of the 2D XY
model; the geometric T=0 critical line separates two unconventional
plaquette-ordered phases that survive to nonzero temperature. The
experimentally important correlations at finite temperature and the nature of
the transitions into these ordered phases are obtained using the mapping to the
three-color model and a combination of perturbation theory and a variational
ansatz for the ordered phases. The ordered phases show sixfold symmetry
breaking and are similar to phases proposed for the honeycomb lattice dimer
model and model. The same mapping and phase transition can be
realized also for integer spins but then require strong on-site
anisotropy in the Hamiltonian.Comment: 5 pages, 2 figure
Prediction of VO\u3csub\u3e2\u3c/sub\u3e Peak Using Sub-Maximum Bench Step Test in Children
The purpose of this study was to develop a valid prediction of maximal oxygen uptake from data collected during a submaximum bench stepping test among children ages 8-12 years. Twentyseven active subjects (16 male and 11 female), weight 36.1 kg, height 144.4 cm and VO2 47.4 ± 7.9 ml/kg/min participated. Subjects completed a maximal oxygen consumption test with analysis of expired air and a submaximal bench stepping test. A formula to predict VO2max was developed from height, resting heart rate and heart rate response during the submaximum bench stepping test. This formula accounted for 71% of the variability in maximal oxygen consumption and is the first step in verifying the validity of the submaximum bench stepping test to predict VO2max. VO2max = -2.354 + (Height in cm * 0.065) + (Resting Heart Rate * 0.008) + (Step Test Average Heart Rate as a Percentage of Resting Heart Rate * -0.870
RTCC requirements for mission G - Trajectory computers for TLI and MCC processors, part 1 Final report
Functional properties of trajectory computers for translunar injection and midcourse correction procedures on lunar orbit
Entanglement entropy of random quantum critical points in one dimension
For quantum critical spin chains without disorder, it is known that the
entanglement of a segment of N>>1 spins with the remainder is logarithmic in N
with a prefactor fixed by the central charge of the associated conformal field
theory. We show that for a class of strongly random quantum spin chains, the
same logarithmic scaling holds for mean entanglement at criticality and defines
a critical entropy equivalent to central charge in the pure case. This
effective central charge is obtained for Heisenberg, XX, and quantum Ising
chains using an analytic real-space renormalization group approach believed to
be asymptotically exact. For these random chains, the effective universal
central charge is characteristic of a universality class and is consistent with
a c-theorem.Comment: 4 pages, 3 figure
Solvable Hydrodynamics of Quantum Integrable Systems
The conventional theory of hydrodynamics describes the evolution in time of
chaotic many-particle systems from local to global equilibrium. In a quantum
integrable system, local equilibrium is characterized by a local generalized
Gibbs ensemble or equivalently a local distribution of pseudo-momenta. We study
time evolution from local equilibria in such models by solving a certain
kinetic equation, the "Bethe-Boltzmann" equation satisfied by the local
pseudo-momentum density. Explicit comparison with density matrix
renormalization group time evolution of a thermal expansion in the XXZ model
shows that hydrodynamical predictions from smooth initial conditions can be
remarkably accurate, even for small system sizes. Solutions are also obtained
in the Lieb-Liniger model for free expansion into vacuum and collisions between
clouds of particles, which model experiments on ultracold one-dimensional Bose
gases.Comment: 6+5 pages, published versio
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