4,530 research outputs found
Auto-focus algorithm based on maximum gradient and threshold
So as to conquer the disservices of the conventional auto-focus algorithm which are poor in real time performance, feeble in anti-noise capability and powerless against the impact of contrast and background pixels, here an auto-focus algorithm focused around greatest gradient and threshold is proposed. It presents an edge component and takes another sort of versatile threshold to evacuate the pixels sullied by noise and background in the picture, then uses enhanced Sobel operators to concentrate maximum gray gradient after picture pre processing and figures assessment esteem. The trial results demonstrate that the proposed algorithm has great continuous-execution, solid unimodality, high sensitivity and strong anti-noise capability. What's more, the algorithm is less impacted by contrast and background in the picture. It can additionally control the sensitivity and focusing reach of the focusing function. So the proposed algorithm is most suitable for auto focu
Deformations of special geometry: in search of the topological string
The topological string captures certain superstring amplitudes which are also
encoded in the underlying string effective action. However, unlike the
topological string free energy, the effective action that comprises
higher-order derivative couplings is not defined in terms of duality covariant
variables. This puzzle is resolved in the context of real special geometry by
introducing the so-called Hesse potential, which is defined in terms of duality
covariant variables and is related by a Legendre transformation to the function
that encodes the effective action. It is demonstrated that the Hesse potential
contains a unique subsector that possesses all the characteristic properties of
a topological string free energy. Genus contributions are constructed
explicitly for a general class of effective actions associated with a
special-K\"ahler target space and are shown to satisfy the holomorphic anomaly
equation of perturbative type-II topological string theory. This identification
of a topological string free energy from an effective action is primarily based
on conceptual arguments and does not involve any of its more specific
properties. It is fully consistent with known results. A general theorem is
presented that captures some characteristic features of the equivalence, which
demonstrates at the same time that non-holomorphic deformations of special
geometry can be dealt with consistently.Comment: 44 pages, LaTex; v2, v3: minor text improvement
Spontaneous breaking of time reversal symmetry in strongly interacting two dimensional electron layers in silicon and germanium
We report experimental evidence of a remarkable spontaneous time reversal
symmetry breaking in two dimensional electron systems formed by atomically
confined doping of phosphorus (P) atoms inside bulk crystalline silicon (Si)
and germanium (Ge). Weak localization corrections to the conductivity and the
universal conductance fluctuations were both found to decrease rapidly with
decreasing doping in the Si:P and Ge:P layers, suggesting an effect
driven by Coulomb interactions. In-plane magnetotransport measurements indicate
the presence of intrinsic local spin fluctuations at low doping, providing a
microscopic mechanism for spontaneous lifting of the time reversal symmetry.
Our experiments suggest the emergence of a new many-body quantum state when two
dimensional electrons are confined to narrow half-filled impurity bands
Internal fixation of pediatric shaft femur fractures by titanium elastic nails: clinical and radiological study
Background: Management of diaphyseal femoral fractures in the pediatric age group is challenging. There has been a demand worldwide for operative fixation.Methods: Twelve children (7 boys, five girls) aged 6-16 years with diaphyseal femoral fractures (12 fractures, one in each) was stabilized with titanium elastic nail system (TENS). Patients underwent surgery within a week days of their injury. The results were evaluated using Flynn's Scoring system. Identical two nails were used in each fracture.Results: All 12 patients were available for evaluation and follow-up for a mean duration of 24 months (14-34 months). Radiological union in all cases was seen at a mean duration of 8 weeks. Full weight bearing was possible at a mean duration of 10 weeks (8-12 weeks). The results were excellent in 8 patients (67%) and satisfactory in 4 patients (33%). Complications that occurred were infection (2 cases), knee joint stiffness (4 cases), angulation <10 degrees (1 case), and shortening less than 10 mm (2 cases). Conclusions: Intramedullary fixation by TENS is an effective, time-tested treatment of fracture of the femur in patients of the 6-16 years age group
Anomalous in-plane magneto-optical anisotropy of self-assembled quantum dots
We report on a complex nontrivial behavior of the optical anisotropy of
quantum dots that is induced by a magnetic field in the plane of the sample. We
find that the optical axis either rotates in the opposite direction to that of
the magnetic field or remains fixed to a given crystalline direction. A
theoretical analysis based on the exciton pseudospin Hamiltonian unambiguously
demonstrates that these effects are induced by isotropic and anisotropic
contributions to the heavy-hole Zeeman term, respectively. The latter is shown
to be compensated by a built-in uniaxial anisotropy in a magnetic field B_c =
0.4 T, resulting in an optical response typical for symmetric quantum dots.Comment: 5 pages, 3 figure
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