10,182 research outputs found
Vortices, circumfluence, symmetry groups and Darboux transformations of the (2+1)-dimensional Euler equation
The Euler equation (EE) is one of the basic equations in many physical fields
such as fluids, plasmas, condensed matter, astrophysics, oceanic and
atmospheric dynamics. A symmetry group theorem of the (2+1)-dimensional EE is
obtained via a simple direct method which is thus utilized to find \em exact
analytical \rm vortex and circumfluence solutions. A weak Darboux
transformation theorem of the (2+1)-dimensional EE can be obtained for \em
arbitrary spectral parameter \rm from the general symmetry group theorem. \rm
Possible applications of the vortex and circumfluence solutions to tropical
cyclones, especially Hurricane Katrina 2005, are demonstrated.Comment: 25 pages, 9 figure
Metoda za optimizaciju tehniÄkih parametara liofilizacije
Vacuum freeze-drying is a technique that makes a material dehydrate at low temperature and low pressure, and it has many merits. A control system is designed and developed based on a certain area freeze-drying machine. A test by the control system is done to optimize the freeze-drying technical parameters. According to the test results, by the method of quadratic orthogonal experiment, the key parameters, including duration, temperature and vacuum of freeze-drying, are analysed and optimized. The test proves the optimized parameters valid for certain vacuum freeze-drying machines and certain bacterins. Furthermore, the optimized parameters show that the vacuum freeze-drying method is useful for any area vacuum freeze-drying machine and any bacterin.Liofilizacija u vakuumu postupak je koji dehidrira materijal pri niskoj temperaturi i niskom tlaku, Å”to ima mnogo prednosti. Kontrolni sustav dizajniran je i razvijen za odreÄeni ureÄaj za liofilizaciju. Kako bi se optimizirali tehniÄki parametri liofilizacije, provedeno je ispitivanje od strane nadzornog sustava. Prema rezultatima, metodom kvadratnog ortogonalnog eksperimenta, analizirani su i optimizirani kljuÄni parametri ukljuÄujuÄi trajanje, temperaturu i razinu vakuuma liofilizacije. Ispitivanje dokazuje da optimizirani parametri vrijede za odreÄene ureÄaje za liofilizaciju i odreÄene bakterine. Dodatno, optimizirani parametri pokazuju da je liofilizacija upotrebljiva za bilo koji ureÄaj za liofilizaciju u vakuumu i bilo koji bakterin
Spin injection from perpendicular magnetized ferromagnetic -MnGa into (Al,Ga)As heterostructures
Electrical spin injection from ferromagnetic -MnGa into an (Al,Ga)As
p-i-n light emitting diode (LED) is demonstrated. The -MnGa layers show
strong perpendicular magnetocrystalline anisotropy, enabling detection of spin
injection at remanence without an applied magnetic field. The bias and
temperature dependence of the spin injection are found to be qualitatively
similar to Fe-based spin LED devices. A Hanle effect is observed and
demonstrates complete depolarization of spins in the semiconductor in a
transverse magnetic field.Comment: 4 pages, 3 figure
Robust and clean Majorana zero mode in the vortex core of high-temperature superconductor (Li0.84Fe0.16)OHFeSe
The Majorana fermion, which is its own anti-particle and obeys non-abelian
statistics, plays a critical role in topological quantum computing. It can be
realized as a bound state at zero energy, called a Majorana zero mode (MZM), in
the vortex core of a topological superconductor, or at the ends of a nanowire
when both superconductivity and strong spin orbital coupling are present. A MZM
can be detected as a zero-bias conductance peak (ZBCP) in tunneling
spectroscopy. However, in practice, clean and robust MZMs have not been
realized in the vortices of a superconductor, due to contamination from
impurity states or other closely-packed Caroli-de Gennes-Matricon (CdGM)
states, which hampers further manipulations of Majorana fermions. Here using
scanning tunneling spectroscopy, we show that a ZBCP well separated from the
other discrete CdGM states exists ubiquitously in the cores of free vortices in
the defect free regions of (Li0.84Fe0.16)OHFeSe, which has a superconducting
transition temperature of 42 K. Moreover, a Dirac-cone-type surface state is
observed by angle-resolved photoemission spectroscopy, and its topological
nature is confirmed by band calculations. The observed ZBCP can be naturally
attributed to a MZM arising from this chiral topological surface states of a
bulk superconductor. (Li0.84Fe0.16)OHFeSe thus provides an ideal platform for
studying MZMs and topological quantum computing.Comment: 32 pages, 15 figures (supplementary materials included), accepted by
PR
Approximate perturbed direct homotopy reduction method: infinite series reductions to two perturbed mKdV equations
An approximate perturbed direct homotopy reduction method is proposed and
applied to two perturbed modified Korteweg-de Vries (mKdV) equations with
fourth order dispersion and second order dissipation. The similarity reduction
equations are derived to arbitrary orders. The method is valid not only for
single soliton solution but also for the Painlev\'e II waves and periodic waves
expressed by Jacobi elliptic functions for both fourth order dispersion and
second order dissipation. The method is valid also for strong perturbations.Comment: 8 pages, 1 figur
A multiple exp-function method for nonlinear differential equations and its application
A multiple exp-function method to exact multiple wave solutions of nonlinear
partial differential equations is proposed. The method is oriented towards ease
of use and capability of computer algebra systems, and provides a direct and
systematical solution procedure which generalizes Hirota's perturbation scheme.
With help of Maple, an application of the approach to the dimensional
potential-Yu-Toda-Sasa-Fukuyama equation yields exact explicit 1-wave and
2-wave and 3-wave solutions, which include 1-soliton, 2-soliton and 3-soliton
type solutions. Two cases with specific values of the involved parameters are
plotted for each of 2-wave and 3-wave solutions.Comment: 12 pages, 16 figure
Study on the multiple dendrite growth of Al ā Si binary alloy using phase ā field method (PFM)
Phase ā field method offers the prospect of carrying out realistic numerical calculation on dendrite growth in metallic systems. The dendritic growth process of Al ā 0,02mole % Si binary alloy was simulated by the coupling method of phase field and solute field. The effects of anisotropic parameters on the growth morphology of dendrite were studied. The results show that with the increase of the anisotropy magnitude, the secondary dendrite arms are more developed, and the dendrite tip is obvious oriented. For the multiple dendrite growth, the dendrites present the morphology from the tip splitting to the dendrite tip oriented. The multi dendritic branching and remelting states of Al ā Si alloy were obtained and the directional solidification remelting and solute segregation were obtained under different anisotropic index conditions. And numerical simulations were conducted to investigate the growth of single and multiple dendrites under coupled conditions of phase field, solute field, and flow field
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