156 research outputs found
Development of Stress Relief Treatments for High Strength Aluminum Alloys Annual Report No. 2, 13 Aug. 1964 - 13 Aug. 1965
Residual stress, strength, and toughness response of high strength aluminum alloys subjected to time-temperature treatment
Interaction of a wave packet with potential structures moving with acceleration
The paper is devoted to a numerical study of the problem of interaction of
the wave packet with potential structures moving with constant acceleration. In
all the cases considered the result of the interaction is a change in the
velocity spectrum. In the first approximation the magnitude of the shift in the
spectrum is determined by the product of acceleration by group delay time.
Also, as the direction of acceleration reverses the effect changes its sign.
The results are completely consistent with the idea of universality of the
Effect of Acceleration which consists in a change in the frequency of the wave
at scattering on an object moving with acceleration
Plasma Oscillations and Expansion of an Ultracold Neutral Plasma
We report the observation of plasma oscillations in an ultracold neutral
plasma. With this collective mode we probe the electron density distribution
and study the expansion of the plasma as a function of time. For classical
plasma conditions, i.e. weak Coulomb coupling, the expansion is dominated by
the pressure of the electron gas and is described by a hydrodynamic model.
Discrepancies between the model and observations at low temperature and high
density may be due to strong coupling of the electrons.Comment: 4 pages, 4 figures. Accepted Phys. Rev. Let
Ambient Diffusion: Learning Clean Distributions from Corrupted Data
We present the first diffusion-based framework that can learn an unknown
distribution using only highly-corrupted samples. This problem arises in
scientific applications where access to uncorrupted samples is impossible or
expensive to acquire. Another benefit of our approach is the ability to train
generative models that are less likely to memorize individual training samples
since they never observe clean training data. Our main idea is to introduce
additional measurement distortion during the diffusion process and require the
model to predict the original corrupted image from the further corrupted image.
We prove that our method leads to models that learn the conditional expectation
of the full uncorrupted image given this additional measurement corruption.
This holds for any corruption process that satisfies some technical conditions
(and in particular includes inpainting and compressed sensing). We train models
on standard benchmarks (CelebA, CIFAR-10 and AFHQ) and show that we can learn
the distribution even when all the training samples have of their pixels
missing. We also show that we can finetune foundation models on small corrupted
datasets (e.g. MRI scans with block corruptions) and learn the clean
distribution without memorizing the training set.Comment: 24 pages, 11 figure
A crossed vortex bottle beam trap for single-atom qubits
We demonstrate trapping and quantum state control of single Cesium atoms in a
532 nm wavelength bottle beam trap. The three dimensional trap is formed by
crossing two unit charge vortex beams. Single atoms are loaded with 50%
probability directly from a magneto-optical trap. We achieve a trapping
lifetime of up to 6 s, and demonstrate fast Rabi oscillations with a coherence
time of .Comment: 5 figures, minor edits to text and figures, to appear opt. let
First Passage and Cooperativity of Queuing Kinetics
We model the kinetics of ligand-receptor systems, where multiple ligands may
bind and unbind to the receptor, either randomly or in a specific order.
Equilibrium occupation and first occurrence of complete filling of the receptor
are determined and compared. At equilibrium, receptors that bind ligands
sequentially are more likely to be saturated than those that bind in random
order. Surprisingly however, for low cooperativity, the random process first
reaches full occupancy faster than the sequential one. This is true {\it
except} near a critical binding energy where a 'kinetic trap' arises and the
random process dramatically slows down when the number of binding sites . These results demonstrate the subtle interplay between cooperativity and
sequentiality for a wide class of kinetic phenomena, including chemical
binding, nucleation, and assembly line strategies.Comment: 5pp, 5 figure
Plasma formation from ultracold Rydberg gases
Recent experiments have demonstrated the spontaneous evolution of a gas of
ultracold Rydberg atoms into an expanding ultracold plasma, as well as the
reverse process of plasma recombination into highly excited atomic states.
Treating the evolution of the plasma on the basis of kinetic equations, while
ionization/excitation and recombination are incorporated using rate equations,
we have investigated theoretically the Rydberg-to-plasma transition. Including
the influence of spatial correlations on the plasma dynamics in an approximate
way we find that ionic correlations change the results only quantitatively but
not qualitatively
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