7,621 research outputs found
Nature of metal-nonmetal transition in metal-ammonia solutions. II. From uniform metallic state to inhomogeneous electronic microstructure
Applying semi-analytical models of nonideal plasma, we evaluate the behavior
of the metallic phase in metal-ammonia solutions (MAS). This behavior is mainly
controlled by the degenerate electron gas, which remains stable down to 5 MPM
due to high solvent polarizability and strong dielectric screening of solvated
ions. Comparing the behavior of the metallic state with those of localized
solvated electrons, we have estimated the miscibility gap for
various alkali metals and found (Na)K. It is rather
narrow in Rb-NH and does not occur in Cs-NH solutions, which is in full
agreement with the experiments. The case of Li is discussed separately. The
difference calculated in the excess free energies of the metallic and
nonmetallic phases is in the order of , yielding a thermally fluctuating
mixed state at intermediate metal concentrations. It results in a continuous
metal-nonmetal (MNM) transition above the consolute point and a phase
separation below . We propose a criterion for the MNM transition which may
be attributed to the line of the maximum of compressibility above . This
line crosses the spinodal one at the critical temperature. Finally, we assert
that a new electronic phase similar to microemulsion should also arise between
the spinodal and the binodal lines.Comment: 22 pages, 10 figure
Real-Time Seamless Single Shot 6D Object Pose Prediction
We propose a single-shot approach for simultaneously detecting an object in
an RGB image and predicting its 6D pose without requiring multiple stages or
having to examine multiple hypotheses. Unlike a recently proposed single-shot
technique for this task (Kehl et al., ICCV'17) that only predicts an
approximate 6D pose that must then be refined, ours is accurate enough not to
require additional post-processing. As a result, it is much faster - 50 fps on
a Titan X (Pascal) GPU - and more suitable for real-time processing. The key
component of our method is a new CNN architecture inspired by the YOLO network
design that directly predicts the 2D image locations of the projected vertices
of the object's 3D bounding box. The object's 6D pose is then estimated using a
PnP algorithm.
For single object and multiple object pose estimation on the LINEMOD and
OCCLUSION datasets, our approach substantially outperforms other recent
CNN-based approaches when they are all used without post-processing. During
post-processing, a pose refinement step can be used to boost the accuracy of
the existing methods, but at 10 fps or less, they are much slower than our
method.Comment: CVPR 201
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Can Big Media do "Big Society"?: A Critical Case Study of Commercial, Convergent Hyperlocal News
The UK Government is committed to helping ‘nurture a new generation of local media companies’. Changes to local media ownership rules allowing companies to follow their customers from platform to platform are supposed to assist in this by encouraging economies of scale. This paper provides a timely case study examining a UK-based commercial local news network owned by Daily Mail & General Trust that leverages economies of scale: Northcliffe Media’s network of 154 Local People websites. The study evaluates the level of audience engagement with the Local People sites through a user survey, and by looking at the numbers of active users, their contributions and their connections with other users. Interviews with ten of the ‘community publishers’ who oversee each site on the ground were conducted, along with a content survey. Although the study reveals a demand for community content, particularly of a practical nature, the results question the extent to which this type of ‘big media’ local news website can succeed as a local social network, reinvigorate political engagement, or encourage citizen reporting. The Government hopes that communities, especially rural ones, will increasingly use the Internet to access local news and information, thereby supporting new, profitable local media companies, who will nurture a sense of local identity and hold locally-elected politicians to account. This case study highlights the difficulties inherent in achieving such outcomes, even using the Government’s preferred convergent, commercial model
Discrete symmetries from hidden sectors
We study the presence of abelian discrete symmetries in globally consistent
orientifold compactifications based on rational conformal field theory. We
extend previous work [1] by allowing the discrete symmetries to be a linear
combination of U(1) gauge factors of the visible as well as the hidden sector.
This more general ansatz significantly increases the probability of finding a
discrete symmetry in the low energy effective action. Applied to globally
consistent MSSM-like Gepner constructions we find multiple models that allow
for matter parity or Baryon triality.Comment: 20 page
Flight Dynamics-based Recovery of a UAV Trajectory using Ground Cameras
We propose a new method to estimate the 6-dof trajectory of a flying object
such as a quadrotor UAV within a 3D airspace monitored using multiple fixed
ground cameras. It is based on a new structure from motion formulation for the
3D reconstruction of a single moving point with known motion dynamics. Our main
contribution is a new bundle adjustment procedure which in addition to
optimizing the camera poses, regularizes the point trajectory using a prior
based on motion dynamics (or specifically flight dynamics). Furthermore, we can
infer the underlying control input sent to the UAV's autopilot that determined
its flight trajectory.
Our method requires neither perfect single-view tracking nor appearance
matching across views. For robustness, we allow the tracker to generate
multiple detections per frame in each video. The true detections and the data
association across videos is estimated using robust multi-view triangulation
and subsequently refined during our bundle adjustment procedure. Quantitative
evaluation on simulated data and experiments on real videos from indoor and
outdoor scenes demonstrates the effectiveness of our method
Dispersive Response of a Disordered Superconducting Quantum Metamaterial
We consider a disordered quantum metamaterial formed by an array of
superconducting flux qubits coupled to microwave photons in a cavity. We map
the system on the Tavis-Cummings model accounting for the disorder in
frequencies of the qubits. The complex transmittance is calculated with the
parameters taken from state-of-the-art experiments. We demonstrate that photon
phase shift measurements allow to distinguish individual resonances in the
metamaterial with up to 100 qubits, in spite of the decoherence spectral width
being remarkably larger than the effective coupling constant. Our simulations
are in agreement with the results of the recently reported experiment.Comment: 10 pages, 4 figure
A possible Efimov trimer state in a 3-component lithium-6 mixture
We consider the Efimov trimer theory as a possible framework to explain
recently observed losses by inelastic three-body collisions in a
three-hyperfine-component ultracold mixture of lithium 6. Within this
framework, these losses would arise chiefly from the existence of an Efimov
trimer bound state below the continuum of free triplets of atoms, and the loss
maxima (at certain values of an applied magnetic field) would correspond to
zero-energy resonances where the trimer dissociates into three free atoms. Our
results show that such a trimer state is indeed possible given the two-body
scattering lengths in the three-component lithium mixture, and gives rise to
two zero-energy resonances. The locations of these resonances appear to be
consistent with observed losses.Comment: 4 pages, 2 figures. Updated figures, equations and references as in
the published version. Note that there is a 1/2 factor missing in Eq. (6) of
the published versio
Discovery and Selection of Certified Web Services Through Registry-Based Testing and Verification
Reliability and trust are fundamental prerequisites for the establishment of functional relationships among peers in a Collaborative Networked Organisation (CNO), especially in the context of Virtual Enterprises where economic benefits can be directly at stake. This paper presents a novel approach towards effective service discovery and selection that is no longer based on informal, ambiguous and potentially unreliable service descriptions, but on formal specifications that can be used to verify and certify the actual Web service implementations. We propose the use of Stream X-machines (SXMs) as a powerful modelling formalism for constructing the behavioural specification of a Web service, for performing verification through the generation of exhaustive test cases, and for performing validation through animation or model checking during service selection
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