1,950 research outputs found
Simple transducer measures low heat-transfer rates
A simple transducer is used to measure low rates of convective and conductive heat transfer from a fluid to a cooled surface under steady-state conditions. Temperature drop is measured by two thermocouples imbedded in a rod of low thermal conductivity
Comparisons of experimental and theoretical aerodynamic heating results in air-carbon dioxide mixtures
Convective aerodynamic heating estimates for air- carbon dioxide gas mixture
Hydrogen-fueled engine
A hydrogen-oxygen fueled internal combustion engine is described, which utilizes an inert gas, such as argon, as a working fluid to increase the efficiency of the engine, eliminate pollution, and facilitate operation of a closed cycle energy system. In a system where sunlight or other intermittent energy source is available to separate hydrogen and oxygen from water, the oxygen and inert gas are taken into a diesel engine into which hydrogen is injected and ignited. The exhaust is cooled so that it contains only water and the inert gas. The inert gas in the exhaust is returned to the engine for use with fresh oxygen, while the water in the exhaust is returned to the intermittent energy source for reconversion to hydrogen and oxygen
Many-body localization beyond eigenstates in all dimensions
Isolated quantum systems with quenched randomness exhibit many-body
localization (MBL), wherein they do not reach local thermal equilibrium even
when highly excited above their ground states. It is widely believed that
individual eigenstates capture this breakdown of thermalization at finite size.
We show that this belief is false in general and that a MBL system can exhibit
the eigenstate properties of a thermalizing system. We propose that localized
approximately conserved operators (l-bits) underlie localization in such
systems. In dimensions , we further argue that the existing MBL
phenomenology is unstable to boundary effects and gives way to l-bits.
Physical consequences of l-bits include the possibility of an eigenstate
phase transition within the MBL phase unrelated to the dynamical transition in
and thermal eigenstates at all parameters in . Near-term experiments
in ultra-cold atomic systems and numerics can probe the dynamics generated by
boundary layers and emergence of l-bits.Comment: 12 pages, 5 figure
Performance experience with the new jpl wind tunnel data acquisition system
Performance characteristics of data acquisition system for wind tunnel digital data functio
Thermal inclusions: how one spin can destroy a many-body localized phase
Many-body localized (MBL) systems lie outside the framework of statistical
mechanics, as they fail to equilibrate under their own quantum dynamics. Even
basic features of MBL systems such as their stability to thermal inclusions and
the nature of the dynamical transition to thermalizing behavior remain poorly
understood. We study a simple model to address these questions: a two level
system interacting with strength with localized bits subject to
random fields. On increasing , the system transitions from a MBL to a
delocalized phase on the \emph{vanishing} scale , up to
logarithmic corrections. In the transition region, the single-site eigenstate
entanglement entropies exhibit bi-modal distributions, so that localized bits
are either "on" (strongly entangled) or "off" (weakly entangled) in
eigenstates. The clusters of "on" bits vary significantly between eigenstates
of the \emph{same} sample, which provides evidence for a heterogenous
discontinuous transition out of the localized phase in single-site observables.
We obtain these results by perturbative mapping to bond percolation on the
hypercube at small and by numerical exact diagonalization of the full
many-body system. Our results imply the MBL phase is unstable in systems with
short-range interactions and quenched randomness in dimensions that are
high but finite.Comment: 17 pages, 12 figure
- …