47,958 research outputs found
Exciton and biexciton energies in bilayer systems
We report calculations of the energies of excitons and biexcitons in ideal
two-dimensional bilayer systems within the effective-mass approximation with
isotropic electron and hole masses. The exciton energies are obtained by a
simple numerical integration technique, while the biexciton energies are
obtained from diffusion quantum Monte Carlo calculations. The exciton binding
energy decays as the inverse of the separation of the layers, while the binding
energy of the biexciton with respect to dissociation into two separate excitons
decays exponentially
Detection of zeptojoule microwave pulses using electrothermal feedback in proximity-induced Josephson junctions
We experimentally investigate and utilize electrothermal feedback in a
microwave nanobolometer based on a normal-metal
(\mbox{Au}_{x}\mbox{Pd}_{1-x}) nanowire with proximity-induced
superconductivity. The feedback couples the temperature and the electrical
degrees of freedom in the nanowire, which both absorbs the incoming microwave
radiation, and transduces the temperature change into a radio-frequency
electrical signal. We tune the feedback in situ and access both positive and
negative feedback regimes with rich nonlinear dynamics. In particular, strong
positive feedback leads to the emergence of two metastable electron temperature
states in the millikelvin range. We use these states for efficient threshold
detection of coherent 8.4 GHz microwave pulses containing approximately 200
photons on average, corresponding to 1.1 \mbox{ zJ} \approx 7.0 \mbox{ meV}
of energy
Dynamic Adaptation on Non-Stationary Visual Domains
Domain adaptation aims to learn models on a supervised source domain that
perform well on an unsupervised target. Prior work has examined domain
adaptation in the context of stationary domain shifts, i.e. static data sets.
However, with large-scale or dynamic data sources, data from a defined domain
is not usually available all at once. For instance, in a streaming data
scenario, dataset statistics effectively become a function of time. We
introduce a framework for adaptation over non-stationary distribution shifts
applicable to large-scale and streaming data scenarios. The model is adapted
sequentially over incoming unsupervised streaming data batches. This enables
improvements over several batches without the need for any additionally
annotated data. To demonstrate the effectiveness of our proposed framework, we
modify associative domain adaptation to work well on source and target data
batches with unequal class distributions. We apply our method to several
adaptation benchmark datasets for classification and show improved classifier
accuracy not only for the currently adapted batch, but also when applied on
future stream batches. Furthermore, we show the applicability of our
associative learning modifications to semantic segmentation, where we achieve
competitive results
Quenching of Er(III) luminescence by ligand C-H vibrations: Implications for the use of erbium complexes in telecommunications
Copyright 2006 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Applied Physics Letters 89, 111115 (2006) and may be found at
Explicit robust schemes for implementation of a class of principal value-based constitutive models: Symbolic and numeric implementation
The issue of developing effective and robust schemes to implement a class of the Ogden-type hyperelastic constitutive models is addressed. To this end, special purpose functions (running under MACSYMA) are developed for the symbolic derivation, evaluation, and automatic FORTRAN code generation of explicit expressions for the corresponding stress function and material tangent stiffness tensors. These explicit forms are valid over the entire deformation range, since the singularities resulting from repeated principal-stretch values have been theoretically removed. The required computational algorithms are outlined, and the resulting FORTRAN computer code is presented
Semi-classical States in Homogeneous Loop Quantum Cosmology
Semi-classical states in homogeneous loop quantum cosmology (LQC) are
constructed by two different ways. In the first approach, we firstly construct
an exponentiated annihilation operator. Then a kind of semi-classical
(coherent) state is obtained by solving the eigen-equation of that operator.
Moreover, we use these coherent states to analyze the semi-classical limit of
the quantum dynamics. It turns out that the Hamiltonian constraint operator
employed currently in homogeneous LQC has correct classical limit with respect
to the coherent states. In the second approach, the other kind of
semi-classical state is derived from the mathematical construction of coherent
states for compact Lie groups due to Hall.Comment: 13 pages, submitted to CQ
Explicit robust schemes for implementation of general principal value-based constitutive models
The issue of developing effective and robust schemes to implement general hyperelastic constitutive models is addressed. To this end, special purpose functions are used to symbolically derive, evaluate, and automatically generate the associated FORTRAN code for the explicit forms of the corresponding stress function and material tangent stiffness tensors. These explicit forms are valid for the entire deformation range. The analytical form of these explicit expressions is given here for the case in which the strain-energy potential is taken as a nonseparable polynomial function of the principle stretches
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