104,114 research outputs found
Geometric model for the critical-value problem of nucleation phenomena containing the size effect of nucleating agent
Nucleation is of great concern in many cases—for example, the production of artificial rainfall and the synthesis of advanced amorphous alloys. Although exact solutions have been well known to both homogeneous nucleation and heterogeneous nucleation occurring on a large flat container wall, yet in more general situations the actual nucleation takes place around finite-sized heterogeneous particles. The understanding of nucleation in such situations requires a more extended model which considers the size effect of nucleating agents. Partially motivated by our research on bulk metallic glasses, we construct such a geometric model. Also we derive an exact solution to the model and discuss briefly its physical implications. A previously presumed relation between the critical energy barrier (Ec) and the volumetric Gibbs free energy of the critical nucleus (Gc)—i.e., Ec=(1/2)Gc—is found to be not true for general cases, although it is correct for the limiting cases
On the rigidity theorems for Lagrangian translating solitons in pseudo-Euclidean space II
Let be a smooth convex function in and the graph
of be a space-like translating soliton in
pseudo-Euclidean space with a translating vector
, then
the function satisfies where , and are constants. The
Bernstein type results are obtained in the course of the arguments.Comment: 9 page
Measurement of surface potential decay of corona-charged polymer films using the pulsed electroacoustic method
In this paper, the pulsed electroacoustic (PEA) technique that allows the determination of space charge in a dielectric material has been used to monitor the electrical potential decay of corona-charged polyethylene films of different thicknesses. To prevent possible disturbance on the surface charge during the PEA measurements, two thin polyethylene films were placed on both sides of the corona-charged sample. Charge profiles measured at different times were used to calculate the potential across the sample. The obtained potential decay was compared with the potential measured using the conventional method. A good agreement has been obtained. More importantly, the charge profile obtained using the PEA technique indicates that bipolar charge injection has taken place
Binding energies of hydrogen-like impurities in a semiconductor in intense terahertz laser fields
A detailed theoretical study is presented for the influence of linearly
polarised intense terahertz (THz) laser radiation on energy states of
hydrogen-like impurities in semiconductors. The dependence of the binding
energy for 1s and 2p states on intensity and frequency of the THz radiation has
been examined.Comment: 14 pages, 4 figure
Electronic properties of bilayer phosphorene quantum dots in the presence of perpendicular electric and magnetic fields
Using the tight-binding approach, we investigate the electronic properties of
bilayer phosphorene (BLP) quantum dots (QDs) in the presence of perpendicular
electric and magnetic fields. Since BLP consists of two coupled phosphorene
layers, it is of interest to examine the layer-dependent electronic properties
of BLP QDs, such as the electronic distributions over the two layers and the
so-produced layer-polarization features, and to see how these properties are
affected by the magnetic field and the bias potential. We find that in the
absence of a bias potential only edge states are layer-polarized while the bulk
states are not, and the layer-polarization degree (LPD) of the unbiased edge
states increases with increasing magnetic field. However, in the presence of a
bias potential both the edge and bulk states are layer-polarized, and the LPD
of the bulk (edge) states depends strongly (weakly) on the interplay of the
bias potential and the interlayer coupling. At high magnetic fields, applying a
bias potential renders the bulk electrons in a BLP QD to be mainly distributed
over the top or bottom layer, resulting in layer-polarized bulk Landau levels
(LLs). In the presence of a large bias potential that can drive a
semiconductor-to-semimetal transition in BLP, these bulk LLs exhibit different
magnetic-field dependences, i.e., the zeroth LLs exhibit a linear-like
dependence on the magnetic field while the other LLs exhibit a square-root-like
dependence.Comment: 11 pages, 6 figure
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