382 research outputs found
Post-war development of geography in Poland
Ces notes témoignent de la vitalité et du dynamisme de la géographie polonaise d'après-guerre. Les chiffres fournis sont impressionnants, surtout si l'on songe à la rapidité avec laquelle la géographie polonaise est ressuscitée du néant où la guerre l'avait plongée. Aujourd'hui sept universités, sept écoles supérieures d'économique, un grand nombre d'écoles supérieures de pédagogie et d'universités technologiques dispensent un enseignement géographique spécialisé.Comme dans la plupart des démocraties populaires, la géographie physique et la géographie économique font l'objet des plus actives recherches. La géomorphologie est une spécialité polonaise ; et c'est en Pologne que les recherches sur les problèmes du quaternaire et sur la géomorphologie périglaciaire connaissent leur maximum de développement. La géographie économique a été de son côté l'objet de recherches très poussées et originales, notamment dans les questions de régionalisation, problème auquel les organismes gouvernementaux des démocraties populaires attachent une énorme importance.L'auteur note que la géographie polonaise a aussi ses points faibles, particulièrement en géographie des transports, en cartographie, en histoire de la géographie et, surtout, en géographie mathématique.Bref, l'avenir de la géographie polonaise s'annonce brillant
Two component Bose-Hubbard model with higher angular momentum states
We study a Bose-Hubbard Hamiltonian of ultracold two component gas of spinor
Chromium atoms. Dipolar interactions of magnetic moments while tuned resonantly
by ultralow magnetic field can lead to spin flipping. Due to approximate axial
symmetry of individual lattice site, total angular momentum is conserved.
Therefore, all changes of the spin are accompanied by the appearance of the
angular orbital momentum. This way excited Wannier states with non vanishing
angular orbital momentum can be created. Resonant dipolar coupling of the two
component Bose gas introduces additional degree of control of the system, and
leads to a variety of different stable phases. The phase diagram for small
number of particles is discussed.Comment: 4 pages, 2 figure
On the stability of Bose-Fermi mixtures
We consider the stability of a mixture of degenerate Bose and Fermi gases.
Even though the bosons effectively repel each other the mixture can still
collapse provided the Bose and Fermi gases attract each other strongly enough.
For a given number of atoms and the strengths of the interactions between them
we find the geometry of a maximally compact trap that supports the stable
mixture. We compare a simple analytical estimation for the critical axial
frequency of the trap with results based on the numerical solution of
hydrodynamic equations for Bose-Fermi mixture.Comment: 4 pages, 3 figure
Free expansion of a Bose-Einstein condensate at the presence of a thermal cloud
We investigate numerically the free-fall expansion of a Rb atoms
condensate at nonzero temperatures. The classical field approximation is used
to separate the condensate and the thermal cloud during the expansion. We
calculate the radial and axial widths of the expanding condensate and find
clear evidence that the thermal component changes the dynamics of the
condensate. Our results are confronted against the experimental data
Soliton trains in Bose-Fermi mixtures
We theoretically consider the formation of bright solitons in a mixture of
Bose and Fermi degenerate gases. While we assume the forces between atoms in a
pure Bose component to be effectively repulsive, their character can be changed
from repulsive to attractive in the presence of fermions provided the Bose and
Fermi gases attract each other strongly enough. In such a regime the Bose
component becomes a gas of effectively attractive atoms. Hence, generating
bright solitons in the bosonic gas is possible. Indeed, after a sudden increase
of the strength of attraction between bosons and fermions (realized by using a
Feshbach resonance technique or by firm radial squeezing of both samples)
soliton trains appear in the Bose-Fermi mixture.Comment: 4 pages, 4 figure
The effect of organic acids as leaching agents for hydrometallurgical recovery of metals from PCBs
The hydrometallurgical treatment, compared to other recycling processes, is of great interest due to its higher efficiency and better economy. In hydrometallurgy, popular agents used in the leaching processes of e-waste include inorganic acids, ammonia, chlorides, thiourea, thiosulphates. Organic acids are also becoming more and more popular. The article presents an overview of possible paths of the metal recovery from e-waste with the use of various organic acids. The results of own research on the leaching of printed circuit boards with the use of organic acids including citric acid, oxalic acid, acetic acid, formic acid, malic acid, lactic acid are also presented
The effect of organic acids as leaching agents for hydrometallurgical recovery of metals from PCBs
The hydrometallurgical treatment, compared to other recycling processes, is of great interest due to its higher efficiency and better economy. In hydrometallurgy, popular agents used in the leaching processes of e-waste include inorganic acids, ammonia, chlorides, thiourea, thiosulphates. Organic acids are also becoming more and more popular. The article presents an overview of possible paths of the metal recovery from e-waste with the use of various organic acids. The results of own research on the leaching of printed circuit boards with the use of organic acids including citric acid, oxalic acid, acetic acid, formic acid, malic acid, lactic acid are also presented
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