Wrocław University of Technology

About: Wrocław University of Technology is a education organization based out in Wrocław, Poland. It is known for research contribution in the topics: Laser & Computer science. The organization has 13115 authors who have published 31279 publications receiving 338694 citations.

Magnetism and Correlations in Fractionally Filled Degenerate Shells of Graphene Quantum Dots

Abstract: We show that the ground state and magnetization of the macroscopically degenerate shell of electronic states in triangular gated graphene quantum dots depends on the filling fraction of the shell. The effect of degeneracy, finite size, and electron-electron interactions are treated nonperturbatively using a combination of density functional theory, tight-binding, Hartree-Fock and configuration interaction methods. We show that electronic correlations play a crucial role in determining the nature of the ground state as a function of filling fraction of the degenerate shell at the Fermi level. We find that the half-filled charge neutral shell leads to full spin polarization but this magnetic moment can be completely destroyed by adding a single electron.

Etch rates and morphology of silicon (h k l) surfaces etched in KOH and KOH saturated with isopropanol solutions

Abstract: Silicon wafers with (1 1 0), (3 3 1), (3 1 1) and (2 1 1) crystallographic orientations etched in KOH and KOH saturated with isopropyl alcohol solutions have been studied. Etch rates of selected (h k l) planes were estimated by direct etch depth measurements. The effects of IPA additive on etch rates, hillocks formation and surface roughness of considered planes were analysed. It was shown that IPA affects the planes of (h h l)-type, causing both their etch rate reduction and surface quality improvement. IPA addition to KOH solution does not reduce etch rates of (h l l)-type planes but results in bulky hillocks formation on the whole etched area. The type of IPA interaction with different crystallographic planes probably depends on bond configuration on a particular plane.

Comparison of bagging, boosting and stacking ensembles applied to real estate appraisal

Abstract: The experiments, aimed to compare three methods to create ensemble models implemented in a popular data mining system called WEKA, were carried out. Six common algorithms comprising two neural network algorithms, two decision trees for regression, linear regression, and support vector machine were used to construct ensemble models. All algorithms were employed to real-world datasets derived from the cadastral system and the registry of real estate transactions. Nonparametric Wilcoxon signed-rank tests to evaluate the differences between ensembles and original models were conducted. The results obtained show there is no single algorithm which produces the best ensembles and it is worth to seek an optimal hybrid multi-model solution.

Complete disentanglement by partial pure dephasing

Abstract: We study the effect of pure dephasing on the entanglement of a pair of two-level subsystems (qubits). We show that partial dephasing induced by a super-Ohmic reservoir, corresponding to well-established properties of confined charge states and phonons in semiconductors, may lead to complete disentanglement. We show also that the disentanglement effect increases with growing distance between the two subsystems.