250 research outputs found
Bayesian inference of substrate properties from film behavior
We demonstrate that by observing the behavior of a film deposited on a substrate, certain features of the substrate may be inferred with quantified uncertainty using Bayesian methods. We carry out this demonstration on an illustrative film/substrate model where the substrate is a Gaussian random field and the film is a two-component mixture that obeys the Cahn–Hilliard equation. We construct a stochastic reduced order model to describe the film/substrate interaction and use it to infer substrate properties from film behavior. This quantitative inference strategy may be adapted to other film/substrate systems.United States. Dept. of Energy. Office of Basic Energy Sciences (Award DE-SC0008926
Simulation of Plasticity in Nanocrystalline Silicon
Molecular dynamics investigation of plasticity in a model nanocrystalline silicon system demonstrates that inelastic deformation localizes in intergranular regions. The carriers of plasticity in these regions are atomic environments that can be described as high-density liquid-like amorphous silicon. During fully developed flow, plasticity is confined to system-spanning intergranular zones of easy flow. As an active flow zone rotates out of the plane of maximum resolved shear stress during deformation to large strain, new zones of easy flow are formed. Compatibility of the microstructure is accommodated by processes such as grain rotation and formation of new grains. Nano-scale voids or cracks may form if there emerge stress concentrations that cannot be relaxed by a mechanism that simultaneously preserves microstructural compatibility
Design of Nano-Composites for Ultra-High Strengths and Radiation Damage Tolerance
The combination of high strength and high radiation damage tolerance in nanolaminate
composites can be achieved when the individual layers in these composites are only a few
nanometers thick and therefore these materials contain a large volume fraction associated with
interfaces. These interfaces act both as obstacles to slip, as well as sinks for radiation-induced
defects. The morphological and phase stabilities of these nano-composites under ion irradiation
are explored as a function of layer thickness, temperature and interface structure. Using results
on model systems such as Cu-Nb, we highlight the critical role of the atomic structure of the
incoherent interfaces that exhibit multiple states with nearly degenerate energies in acting as
sinks for radiation-induced point defects. Reduced radiation damage also leads to a reduction in
the irradiation hardening, particularly at layer thickness of approximately 5 nm and below. The
strategies for design of radiation-tolerant structural materials based on the knowledge gained
from this work will be discussed
Experimental Extraction of Secure Correlations from a Noisy Private State
We report experimental generation of a noisy entangled four-photon state that
exhibits a separation between the secure key contents and distillable
entanglement, a hallmark feature of the recently established quantum theory of
private states. The privacy analysis, based on the full tomographic
reconstruction of the prepared state, is utilized in a proof-of-principle key
generation. The inferiority of distillation-based strategies to extract the key
is exposed by an implementation of an entanglement distillation protocol for
the produced state.Comment: 5 pages, 3 figures, final versio
Quantum-enhanced gyroscopy with rotating anisotropic Bose–Einstein condensates
High-precision gyroscopes are a key component of inertial navigation systems. By considering matter wave gyroscopes that make use of entanglement it should be possible to gain some advantages in terms of sensitivity, size, and resources used over unentangled optical systems. In this paper we consider the details of such a quantum-enhanced atom interferometry scheme based on atoms trapped in a carefully-chosen rotating trap. We consider all the steps: entanglement generation, phase imprinting, and read-out of the signal and show that quantum enhancement should be possible in principle. While the improvement in performance over equivalent unentangled schemes is small, our feasibility study opens the door to further developments and improvements
The effect of excess atomic volume on He bubble formation at fcc-bcc interfaces
Atomistic modeling shows that Cu–Nb and Cu–V interfaces contain high excess atomic volume due to constitutional vacancy concentrations of ∼ 5 at. % and ∼ 0.8 at. %., respectively. This finding is supported by experiments demonstrating that an approximately fivefold higher He concentration is required to observe He bubbles via through-focus transmission electron microscopy at Cu–Nb interfaces than in Cu–V interfaces. Interfaces with structures tailored to minimize precipitation and growth of He bubbles may be used to design damage-resistant composites for fusion reactors.United States. Dept. of Energy. Office of Basic Energy Sciences (award 2008LANL1026
Modeling of bone conduction of sound in the human head using hp-finite elements: Code design and verification
We focus on the development of a reliable numerical model for investigating the bone-conduction of sound in the human head. The main challenge of the problem is the lack of fundamental knowledge regarding the transmission of acoustic energy through non-airborne pathways to the cochlea. A fully coupled model based on the acoustic/elastic interaction problem with a detailed resolution of the cochlea region and its interface with the skull and the air pathways, should provide an insight into this fundamental, long standing research problem. To this aim we have developed a 3D hp-finite element code that supports elements of all shapes (tetrahedra, prisms and pyramids) to better capture the geometrical features of the head. We have tested the code on a multilayered sphere and employed it to solve an idealized model of head. In the future we hope to attack a model with a more realistic geometry
Non-random walk diffusion enhances the sink strength of semicoherent interfaces
Clean, safe and economical nuclear energy requires new materials capable of withstanding severe radiation damage. One strategy of imparting radiation resistance to solids is to incorporate into them a high density of solid-phase interfaces capable of absorbing and annihilating radiation-induced defects. Here we show that elastic interactions between point defects and semicoherent interfaces lead to a marked enhancement in interface sink strength. Our conclusions stem from simulations that integrate first principles, object kinetic Monte Carlo and anisotropic elasticity calculations. Surprisingly, the enhancement in sink strength is not due primarily to increased thermodynamic driving forces, but rather to reduced defect migration barriers, which induce a preferential drift of defects towards interfaces. The sink strength enhancement is highly sensitive to the detailed character of interfacial stresses, suggesting that ‘super-sink' interfaces may be designed by optimizing interface stress fields. Such interfaces may be used to create materials with unprecedented resistance to radiation-induced damage
Quantum states made to measure
Recent progress in manipulating quantum states of light and matter brings
quantum-enhanced measurements closer to prospective applications. The current
challenge is to make quantum metrologic strategies robust against
imperfections.Comment: 4 pages, 3 figures, Commentary for Nature Photonic
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