Piotr Tadeusz Różański

Piotr Tadeusz Różański
Nicolaus Copernicus University | umk · Department of Quantum Mechanics

Master of Science

About

31
Publications
2,816
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126
Citations
Introduction
Please refer to https://rozan.ski/ for more information (in both Polish and English).

Publications

Publications (31)
Poster
Full-text available
Matching Pursuit (MP) is an adaptive algorithm proposed by Mallat and Zhang in 1993 for generating a sub-optimal solution of NP-hard problem of finding optimal approximation of signal from a redundant set (dictionary) D using an iterative (greedy) procedure. Since the first practical applications researched at the Faculty of Physics in University...
Article
Full-text available
Matching pursuit is a greedy algorithm for computing a decomposition of the given signal as a linear combination of elements from an over-complete set (a “dictionary”). This paper generalizes the construction of an optimal dictionary to non-Gaussian envelope functions, and demonstrates that optimizing the dictionary with regard to the envelope func...
Article
Full-text available
Disorders of consciousness (DOC) are among the major challenges of contemporary medicine, mostly due to the high rates of misdiagnoses in clinical assessment, based on behavioral scales. This turns our attention to potentially objective neuroimaging methods. Paradigms based on electroencephalography (EEG) are most suited for bedside applications, b...
Article
Atomistic modeling of nanostructures such as quantum dots or nanowires often involves numbers of atoms reaching and even exceeding well beyond 1 million. Such a large quantity of atoms presents a very complex computational challenge especially at a stage of many-body calculation where numerous Coulomb matrix elements need to be calculated. Here we...
Article
Journal of Applied Computer Science (ISSN 1507-0360) *** The matching pursuit (MP) algorithm is a greedy method for signal decomposition used in video coding, data compression, and, particularly, analysis of EEG signals in various paradigms, including P300 and ER(D)S (motor imagery). An important issue for MP implementation is a correct treatment...
Article
Full-text available
We propose a fully parametric approach to the assessment of sleep architecture, based upon the classical electroencephalographic criteria, applicable also to the recordings of patients with disorders of consciousness (DOC). Sleep spindles and slow waves are automatically detected from the matching pursuit decomposition of overnight EEG recordings....
Poster
Crystal-phase quantum dots are formed by sections of a crystal material within a nanowire formed by a different crystal phase, whereas both phases share the same chemical composition. In case of zinc-blende sections in InP wurtzite nanowires this results in type-II confinement. Theoretical understanding of spectra of such nanostructures is so far l...
Poster
INTRODUCTION: Event-related (de-)synchronization (ER(D)S) is a short‑lasting modulation of specific frequency bands (e.g. alpha band) of EEG, which occurs in response for external stimuli (visual, haptic) or with motor imagery and execution of movements. Since it’s both time- and frequency‑specific, it is typically analysed in time‑frequency space,...
Poster
Excitonic properties of novel nanostructures such as crystal-phase quantum dots or semiconductor quantum wires are difficult to calculate with first-principle modelling such as the density functional theory (DFT) due to their size, often exceeding millions of atoms. On the other hand, simplified methods such as the effective mass approximation do n...
Article
Numerical calculations of excitonic properties of novel nanostructures, such as nanowire and crystal phase quantum dots, must combine atomistic accuracy with an approachable computational complexity. The key di?culty comes from the fact that excitonic spectra details arise from atomicscale contributions that must be integrated over a large spatial...
Poster
Full-text available
Brain-computer interfaces based on SSVEP (steady-state visual evoked potentials) are traditionally built using professional-grade light emitting devices. Accurate, portable and customizable stimulator is desired for such application. The goal of this study is to increase the practicability, portability and ubiquity of an SSVEP-based BCI for daily u...
Article
Full-text available
We present a complete framework for time-frequency parametrization of EEG transients, based upon matching pursuit (MP) decomposition, applied to the detection of sleep spindles. Ranges of spindles duration (>0.5 s) and frequency (11-16 Hz) are taken directly from their standard definitions. Minimal amplitude is computed from the distribution of the...
Poster
Full-text available
Feature extraction is a vital part of the biomedical signal analysis. Many phenomena in brain activity can be identified by presence or absence of well-defined time-frequency structures in EEG signal. High resolution selective detection and identification of these structures can be achieved with Matching Pursuit algorithm. Several variations of Mat...
Article
Full-text available
http://www.biomedical-engineering-online.com/content/12/1/94 Matching pursuit algorithm (MP), especially with recent multivariate extensions, offers unique advantages in analysis of EEG and MEG. We propose a novel construction of an optimal Gabor dictionary, based upon the metrics introduced in this paper. We implement this construction in a freel...
Article
Full-text available
We report a theoretical investigation of electronic properties of semiconductor InAs and GaAs nanocrystals. Our calculation scheme starts with the single particle calculation using atomistic tight-binding model including spinorbital interaction and d-orbitals. Then the exciton binding energies are calculated with screened Coulomb interaction. We st...
Poster
We present atomistic theory for calculation of many body properties of semiconductor quantum dots that scales linearly with number of atoms in computational domain. Our approach uses nearest neighbors tight-binding (TB) model incorporating d-orbitals, spin-orbit interaction and strain induced diagonal parameters shifts for fast O(n) calculation of...
Article
Full-text available
Two observational campaigns were carried out during the eclipses of EE Cep in 2003 and 2008/9 to verify whether the eclipsing body in the system is indeed a dark disk and to understand the observed changes in the depth and durations of the eclipses. Multicolour photometric data and spectroscopic observations at both low and high resolution were col...
Poster
Dielectric screening of Coulomb interactions affects optical and electronic properties of semiconductor nanostructures including multi-exciton generation rates in colloidal nanocrystals, excitonic spectra and self-energy corrections in nanopillar or graphene quantum dots. Using tight-binding approach we compare several methods of accounting for die...
Poster
Full-text available
Efektywny algorytm transkrypcji muzyki polifonicznej
Article
Full-text available
Jak wiadomo, każdy człowiek ma dwoje rodziców. Skoro każdy z rodziców też jest człowiekiem, ta rekurencyjna zależność pozwala w prosty sposób wyznaczyć liczbę przodków dowolnej osoby w linii prostej w kolejnych pokoleniach: czworo babć i dziadków, ośmioro prababć i pradziadków, a zatem ogólnie (pra)^n dziadków obojga płci mamy 2^{n+2}.
Presentation
Full-text available
Pytanie zawarte w tytule referatu, choć pozornie trywialne, do pełnego rozwiązania wymaga wykorzystania teorii prawdopodobieństwa oraz ustalenia modelu i parametrów rozwoju populacji. Po zapoznaniu ze stosowanymi oznaczeniami, przedstawione zostaną obliczenia i wyniki dla różnych wariantów modelu i różnych skal liczebności populacji. Ponadto, porus...
Article
Full-text available
Nova V2491 Cyg was discovered on April 10.72 UT 2008 (Nakano, 2008). Here we present spectrophotometric premises that V2491 Cyg can be a good candidate for recurrent nova (RNe). Its properties are compared to five well known RNe with red dwarf secondaries (U Sco, V394 Cra, T Pyx, CI Aql, IM Nor) and recently confirmed as recurrent nova V2487 Oph (P...
Article
Full-text available
We present photometric and spectral observation for four novae: V2362 Cyg, V2467 Cyg, V458 Vul, V2491 Cyg. All objects belongs to the "fast novae" class. For these stars we observed different departures from a typical behavior in the light curve and spectrum.
Article
Full-text available
We present UBVRI photometry of three symbiotic stars ZZ CMi, TX CVn and AG Peg carried out from 1997 to 2008 in Piwnice Observatory near Torun. To search orbital periods of these stars Fourier analysis was used. For two of them, TX CVn and AG Peg, we have confirmed the earlier known periods. For ZZ CMi we found a relatively short period 218.59 days...
Article
Full-text available
The photometric and spectroscopic observational campaign organized for the 2008/9 eclipse of EE Cep revealed features, which indicate that the eclipsing disk in the EE Cep system has a multi-ring structure. We suggest that the gaps in the disk can be related to the possible planet formation. Comment: 6 pages, 6 figures, contribution to the conferen...
Article
Full-text available
In a flat space, the global topology of comoving space can induce a weak acceleration effect similar to dark energy. Does a similar effect occur in the case of the Poincare dodecahedral space S^3/I^*? Does the effect distinguish the Poincare space from other well-proportioned spaces? The residual acceleration effect in the Poincare space is studied...