Piotr Tadeusz Różański

Leon Software

The design and implementation of dopant-based silicon nanoscale devices rely heavily on knowing precisely the locations of phosphorous dopants in their host crystal. One potential solution combines scanning tunneling microscopy (STM) imaging with atomistic tight-binding simulations to reverse-engineer dopant coordinates. This work shows that such a...

This article introduces an effective approach to performing matching pursuit calculations with continuous (quasi-infinite) dictionaries. Simulating continuous parameter space is accomplished by combining optimal dictionary construction as introduced previously with local parameter optimization. At the same time, the calculations can be performed no...

Atomistic modeling of nanostructures often leads to computationally challenging problems involving millions of atoms and tens of thousands of Coulomb matrix elements. In our previous work, we presented a practical solution to this problem, where quasi-linear efficiency, both in time and memory, was obtained by utilizing the fast Fourier transform....

The ability to determine the locations of phosphorous dopants in silicon is crucial for the design, modelling, and analysis of atom-based nanoscale devices for future quantum computing applications. Recently, several papers showed that a metrology of scanning tunnelling microscopy (STM) imaging combined with atomistic tight-binding simulations coul...

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...

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...

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...

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...

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...

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....

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...

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,...

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...

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...

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...

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...

Common Spatial Pattern and statistical tests in social Simon experiment

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...

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...

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...

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...

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...

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...

Efektywny algorytm transkrypcji muzyki polifonicznej

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}.

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...

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...

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.

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...

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...

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...