10,866 research outputs found
An Approximate Bayesian Long Short-Term Memory Algorithm for Outlier Detection
Long Short-Term Memory networks trained with gradient descent and
back-propagation have received great success in various applications. However,
point estimation of the weights of the networks is prone to over-fitting
problems and lacks important uncertainty information associated with the
estimation. However, exact Bayesian neural network methods are intractable and
non-applicable for real-world applications. In this study, we propose an
approximate estimation of the weights uncertainty using Ensemble Kalman Filter,
which is easily scalable to a large number of weights. Furthermore, we optimize
the covariance of the noise distribution in the ensemble update step using
maximum likelihood estimation. To assess the proposed algorithm, we apply it to
outlier detection in five real-world events retrieved from the Twitter
platform
Optimal Walking of an Underactuated Planar Biped with Segmented Torso
Recently, underactuated bipeds with pointed feet have been studied to achieve dynamic and energy efficient robot walking patterns. However, these studies usually simplify a robot torso as one link, which is different from a human torsos containing 33 vertebrae. In this paper, therefore, we study the optimal walking of a 6-link planar biped with a segmented torso derived from its 5-link counterpart while ensuring that two models are equivalent when the additional torso joint is locked. For the walking, we suppose that each step is composed of a single support phase and an instantaneous double support phase, and two phases are connected by a plastic impact mapping. In addition, the controlled outputs named symmetry outputs capable of generating exponentially stable orbits using hybrid zero dynamics, are adopted to improve physical interpretation. The desired outputs are parameterized by B´ezier functions, with 5-link robot having 16 parameters to optimize and 6-link robot having 19 parameters. According to our energy criterion, the segmented torso structure may reduce energy consumption up to 8% in bipedal walking, and the maximum energy saving is achieved at high walking speeds, while leaving the criteria at low walking speeds remain similar for both robots.China CSC LCF
Measure of genuine multipartite entanglement with computable lower bounds
We introduce an intuitive measure of genuine multipartite entanglement which
is based on the well-known concurrence. We show how lower bounds on this
measure can be derived that also meet important characteristics of an
entanglement measure. These lower bounds are experimentally implementable in a
feasible way enabling quantification of multipartite entanglement in a broad
variety of cases.Comment: 5 pages, 2 figure
Full evolution of low-mass white dwarfs with helium and oxygen cores
We study the full evolution of low-mass white dwarfs with helium and oxygen cores. We revisit the age dichotomy observed in many white dwarf companions to millisecond pulsar on the basis of white dwarf configurations derived from binary evolution computations. We evolve 11 dwarf sequences for helium cores with final masses of 0.1604, 0.1869, 0.2026, 0.2495, 0.3056, 0.3333, 0.3515, 0.3844, 0.3986, 0.4160 and 0.4481 M. In addition, we compute the evolution of five sequences for oxygen cores with final masses of 0.3515, 0.3844, 0.3986, 0.4160 and 0.4481 M. A metallicity of Z = 0.02 is assumed. Gravitational settling, chemical and thermal diffusion are accounted for during the white dwarf regime. Our study reinforces the result that diffusion processes are a key ingredient in explaining the observed age and envelope dichotomy in low-mass helium-core white dwarfs, a conclusion we arrived at earlier on the basis of a simplified treatment for the binary evolution of progenitor stars. We determine the mass threshold where the age dichotomy occurs. For the oxygen white dwarf sequences, we report the occurrence of diffusion-induced, hydrogen-shell flashes, which, as in the case of their helium counterparts, strongly influence the late stages of white dwarf cooling. Finally, we presensent our results as a set of white dwarf mass–radius relations for helium and oxygen cores.Fil: Panei, Jorge Alejandro. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Althaus, Leandro Gabriel. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Chen, X.. Chinese Academy of Sciences; República de ChinaFil: Han, Z.. Chinese Academy of Sciences; República de Chin
Detection of genuinely entangled and non-separable -partite quantum states
We investigate the detection of entanglement in -partite quantum states.
We obtain practical separability criteria to identify genuinely entangled and
non-separable mixed quantum states. No numerical optimization or eigenvalue
evaluation is needed, and our criteria can be evaluated by simple computations
involving components of the density matrix. We provide examples in which our
criteria perform better than all known separability criteria. Specifically, we
are able to detect genuine -partite entanglement which has previously not
been identified. In addition, our criteria can be used in today's experiment.Comment: 8 pages, one figur
Ambipolar Graphene Field Effect Transistors by Local Metal Side Gates
We demonstrate ambipolar graphene field effect transistors individually
controlled by local metal side gates. The side gated field effect can have
on/off ratio comparable with that of the global back gate, and can be tuned in
a large range by the back gate and/or a second side gate. We also find that the
side gated field effect is significantly stronger by electrically floating the
back gate compared to grounding the back gate, consistent with the finding from
electrostatic simulation.Comment: 4 pages, 3 figure
- …