40,204 research outputs found
Imaging Studies of Characteristics for a Slab of a Lossy Left-handed Material
The characteristics of an imaging system formed by a slab of a lossy
left-handed material (LHM) are studied. The transfer function of the LHM
imaging system is written in an appropriate product form with each term having
a clear physical interpretation. A tiny loss of the LHM may suppress the
transmission of evanescent waves through the LHM slab and this is explained
physically. An analytical expression for the resolution of the imaging system
is derived. It is shown that it is impossible to make a subwavelength imaging
by using a realistic LHM imaging system unless the LHM slab is much thinner
than the wavelength.Comment: 15 pages, 10 figure
Ontobull and BFOConvert: Web-based programs to support automatic ontology conversion
When a widely reused ontology appears in a new version which is not compatible with older versions, the ontologies reusing it need to be updated accordingly. Ontobull has been developed to automatically update ontologies with new term IRI(s) and associated metadata to take account of such version changes. To use the Ontobull web interface a user is required to (i) upload one or more ontology OWL source files; (ii) input an ontology term IRI mapping; and (where needed) (iii) provide update settings for ontology headers and XML namespace IDs.
Using this information, the backend Ontobull Java program automatically updates the OWL ontology files with desired term IRIs and ontology metadata. The Ontobull subprogram BFOConvert supports the conversion of an ontology that imports a previous version of BFO. A use case is provided to demonstrate the features of Ontobull and BFOConvert
Optical Field Enhancement in Nanoscale Slot Waveguides of Hyperbolic Metamaterials
Nanoscale slot waveguides of hyperbolic metamaterials are proposed and
demonstrated for achieving large optical field enhancement. The dependence of
the enhanced electric field within the air slot on waveguide mode coupling and
permittivity tensors of hyperbolic metamaterials is analyzed both numerically
and analytically. Optical intensity in the metamaterial slot waveguide can be
more than 25 times stronger than that in a conventional silicon slot waveguide,
due to tight optical mode confinement enabled by the ultrahigh refractive
indices supported in hyperbolic metamaterials. The electric field enhancement
effects are also verified with the realistic metal-dielectric multilayer
waveguide structure.Comment: 13 pages, 4 figure
Unitarity of the Higher Dimensional Standard Model
We study the unitarity of the standard model (SM) in higher dimensions. We
show that the essential features of SM unitarity remain after compactification,
and place bounds on the highest Kaluza-Klein (KK) level N_KK and the Higgs mass
m_H in the effective four-dimensional (4d) low-energy theory. We demonstrate
these general observations by explicitly analyzing the effective 4d KK theory
of a compactified 5d SM on S^1/Z_2. The nontrivial energy cancellations in the
scattering of longitudinal KK gluons or KK weak bosons, a consequence of the
geometric Higgs mechanism, are verified. In the case of the electroweak gauge
bosons, the longitudinal KK states also include a small mixture from the KK
Higgs excitations. With the analyses before and after compactification, we
derive the strongest bounds on N_KK from gauge KK scattering. Applying these
bounds to higher-dimensional SUSY GUTs implies that only a small number of KK
states can be used to accelerate gauge coupling unification. As a consequence,
we show that the GUT scale in the 5d minimal SUSY GUT cannot be lower than
about 10^{14} GeV.Comment: Version in Phys. Lett. B (minor typos fixed, refs added
AUV SLAM and experiments using a mechanical scanning forward-looking sonar
Navigation technology is one of the most important challenges in the applications of autonomous underwater vehicles (AUVs) which navigate in the complex undersea environment. The ability of localizing a robot and accurately mapping its surroundings simultaneously, namely the simultaneous localization and mapping (SLAM) problem, is a key prerequisite of truly autonomous robots. In this paper, a modified-FastSLAM algorithm is proposed and used in the navigation for our C-Ranger research platform, an open-frame AUV. A mechanical scanning imaging sonar is chosen as the active sensor for the AUV. The modified-FastSLAM implements the update relying on the on-board sensors of C-Ranger. On the other hand, the algorithm employs the data association which combines the single particle maximum likelihood method with modified negative evidence method, and uses the rank-based resampling to overcome the particle depletion problem. In order to verify the feasibility of the proposed methods, both simulation experiments and sea trials for C-Ranger are conducted. The experimental results show the modified-FastSLAM employed for the navigation of the C-Ranger AUV is much more effective and accurate compared with the traditional methods
CP Violating Form Factors for Three Gauge Boson Vertex in the Two Higgs Doublet and Left-Right symmetric Models
In this paper we calculate the one loop contributions to the CP violating
three gauge boson couplings in two-Higgs doublet and Left--Right symmetric
models. In the two-Higgs doublet model only a P conserving and CP violating
coupling is generated, and it can be large as . In the Left--Right
symmetric model both P conserving and violating couplings are generated. Due to
constraints on the -- mixing, these couplings are small.Comment: 9 pages, Tex, UM-P-92/75, OZ-92/2
Frequency range and explicit expressions for negative permittivity and permeability for an isotropic medium formed by a lattice of perfectly conducting particles
An analytical model is presented for a rectangular lattice of isotropic
scatterers with electric and magnetic resonances. Each isotropic scatterer is
formed by putting appropriately 6 -shaped perfectly conducting
particles on the faces of a cubic unit cell. A self-consistent dispersion
equation is derived and then used to calculate correctly the effective
permittivity and permeability in the frequency band where the lattice can be
homogenized. The frequency range in which both the effective permittivity and
permeability are negative corresponds to the mini-band of backward waves within
the resonant band of the individual isotropic scatterer.Comment: 25 pages, 6 figure
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