12,509 research outputs found
Dynamical Electron Mass in a Strong Magnetic Field
Motivated by recent interest in understanding properties of strongly
magnetized matter, we study the dynamical electron mass generated through
approximate chiral symmetry breaking in QED in a strong magnetic field. We
reliably calculate the dynamical electron mass by numerically solving the
nonperturbative Schwinger-Dyson equations in a consistent truncation within the
lowest Landau level approximation. It is shown that the generation of dynamical
electron mass in a strong magnetic field is significantly enhanced by the
perturbative electron mass that explicitly breaks chiral symmetry in the
absence of a magnetic field.Comment: 5 pages, 1 figure, published versio
The structure, energy, and electronic states of vacancies in Ge nanocrystals
The atomic structure, energy of formation, and electronic states of vacancies
in H-passivated Ge nanocrystals are studied by density functional theory (DFT)
methods. The competition between quantum self-purification and the free surface
relaxations is investigated. The free surfaces of crystals smaller than 2 nm
distort the Jahn-Teller relaxation and enhance the reconstruction bonds. This
increases the energy splitting of the quantum states and reduces the energy of
formation to as low as 1 eV per defect in the smallest nanocrystals. In
crystals larger than 2 nm the observed symmetry of the Jahn-Teller distortion
matches the symmetry expected for bulk Ge crystals. Near the nanocrystal's
surface the vacancy is found to have an energy of formation no larger than 0.5
to 1.4 eV per defect, but a vacancy more than 0.7 nm inside the surface has an
energy of formation that is the same as in bulk Ge. No evidence of the
self-purification effect is observed; the dominant effect is the free surface
relaxations, which allow for the enhanced reconstruction. From the evidence in
this paper, it is predicted that for moderate sized Ge nanocrystals a vacancy
inside the crystal will behave bulk-like and not interact strongly with the
surface, except when it is within 0.7 nm of the surface.Comment: In Press at Phys. Rev.
Note: An object detection method for active camera
To solve the problems caused by a changing background during object detection in active camera, this paper proposes a new method based on SURF (speeded up robust features) and data clustering. The SURF feature points of each image are extracted, and each cluster center is calculated by processing the data clustering of k adjacent frames. Templates for each class are obtained by calculating the histograms within the regions around the center points of the clustering classes. The window of the moving object can be located by finding the region that satisfies the histogram matching result between adjacent frames. Experimental results demonstrate that the proposed method can improve the effectiveness of object detection.Yong Chen, Ronghua Zhang, Lei Shang, and Eric H
Computational fluid dynamics combustion analysis evaluation
This study involves the development of numerical modelling in spray combustion. These modelling efforts are mainly motivated to improve the computational efficiency in the stochastic particle tracking method as well as to incorporate the physical submodels of turbulence, combustion, vaporization, and dense spray effects. The present mathematical formulation and numerical methodologies can be casted in any time-marching pressure correction methodologies (PCM) such as FDNS code and MAST code. A sequence of validation cases involving steady burning sprays and transient evaporating sprays will be included
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