Numerické optimalizace experimentů NMR pevné fáze

Numerical optimizations of solid-state nuclear magnetic resonance experiments are one of the possible solutions to its low sensitivity. Using the Average Hamiltonian Theory, the negative effects of the radiofrequency field inhomogeneity on magnetization transfer were investigated. To overcome these effects, the Average Hamiltonian Theory was employed in the optimization of commonly used techniques such as Ramp-CP and Adiabatic-CP, optimization of pulses with arbitrarily modulated amplitude and new periodic pulses with arbitrarily modulated amplitudes and phases. Both types of shaped pulses achieved significantly higher efficiencies than Ramp- CP and Adiabatic-CP. The highest efficiency enhancement was calculated at high spinning frequencies and low dipolar coupling constants where the effect of the inhomogeneity is the strongest.Numerické optimalizácie experimentov nukleárnej magnetickej rezonancie pevnej fázy sú jedným z možných riešení nízkej citlivosti tejto metódy. Využitím teórie priemerného Hamiltoniánu boli preskúmané negatívne vplyvy nehomogenity rádiofrekvenčných polí na prenos magnetizácie medzi jadrami. Následne, za účelom ich prekonania, bola táto teória využitá na optimalizáciu bežne používaných techník Ramp-CP a Adiabatic-CP, pulzov s ľubovoľne modulovanou amplitúdou, aj úplne nových, periodických pulzov s ľubovoľnou amplitúdou a fázou. Obidva typy tvarovaných pulzov dosahujú výrazne vyššie teoretické účinnosti, než zaužívané techniky. K najvýznamnejšiemu nárastu účinnosti došlo pri vysokých rýchlostiach rotácie vzorky a nízkych dipól-dipólových interakčných konštantách, kedy je vplyv nehomogenity rádiofrekvenčných polí najvýraznejší.Katedra fyzikální a makromol. chemieDepartment of Physical and Macromolecular ChemistryFaculty of SciencePřírodovědecká fakult

Performance of the cross-polarization experiment in conditions of radiofrequency field inhomogeneity and slow to ultrafast magic angle spinning (MAS)

In this paper, we provide an analytical description of the performance of the cross-polarization (CP) experiment, including linear ramps and adiabatic tangential sweeps, using effective Hamiltonians and simple rotations in 3D space. It is shown that radiofrequency field inhomogeneity induces a reduction in the transfer efficiency at increasing magic angle spinning (MAS) frequencies for both the ramp and the adiabatic CP experiments. The effect depends on the ratio of the dipolar coupling constant and the sample rotation frequency. In particular, our simulations show that for small dipolar couplings (1 kHz) and ultrafast MAS (above 100 kHz) the transfer efficiency is below 40 % when extended contact times up to 20 ms are used and relaxation losses are ignored. New recoupling and magnetization transfer techniques that are designed explicitly to account for inhomogeneous radiofrequency fields are needed.</p

CubeSats in Support of Astrophysics, GRBAlpha and Beyond

Space science, including the field of astrophysics, is continuously finding innovative use cases for small satellites and CubeSat platforms. These missions support efforts in the democratisation and improved accessibility of space technologies. GRBAlpha, as one of such missions, is a 1U CubeSat carrying an experimental payload for the detection of gamma-ray bursts (GRB)

GRBAlpha: the smallest astrophysical space observatory -- Part 1: Detector design, system description and satellite operations

Aims. Since launched on 2021 March 22, the 1U-sized CubeSat GRBAlpha operates and collects scientific data on high-energy transients, making it the smallest astrophysical space observatory to date. GRBAlpha is an in-obit demonstration of a gamma-ray burst (GRB) detector concept suitably small to fit into a standard 1U volume. As it was demonstrated in a companion paper, GRBAlpha adds significant value to the scientific community with accurate characterization of bright GRBs, including the recent outstanding event of GRB 221009A. Methods. The GRB detector is a 75x75x5 mm CsI(Tl) scintillator wrapped in a reflective foil (ESR) read out by an array of SiPM detectors, multi-pixel photon counters by Hamamatsu, driven by two separate, redundant units. To further protect the scintillator block from sunlight and protect the SiPM detectors from particle radiation, we apply a multi-layer structure of Tedlar wrapping, anodized aluminium casing and a lead-alloy shielding on one edge of the assembly. The setup allows observations of gamma radiation within the energy range of 70-890 keV with an energy resolution of ~30%. Results. Here, we summarize the system design of the GRBAlpha mission, including the electronics and software components of the detector, some aspects of the platform as well as the current way of semi-autonomous operations. In addition, details are given about the raw data products and telemetry in order to encourage the community for expansion of the receiver network for our initiatives with GRBAlpha and related experiments.Comment: Accepted for publication in Astronomy & Astrophysics, 9 pages, 10 figure

Vytváření herních strategií pro hru PuppetWars pomocí neuroevoluce

In recent years the gaming industry has been on increase. In order to maintain competitiveness gaming companies are required to develop more and more compelling computer games what implies the presence of the very responsive artificial intelligence controlling the game elements, on which our work focuses. We have implemented a simple 2D programming game where we have experimented with the artificial intelligence in it trying to create a strategy beeing able to compete with human. We have explored several variations of learning through the evolutionary strategy applied to neural networks and we have created game characters worthy of being an equal opponent to the game user.V posledných rokoch nastal v hernom priemysle rozmach. Pre udržanie konkurencieschopnosti sú herné spoločnosti nútené vyvíjať stále viac príťažli- vé počítačové hry, čo implikuje i prítomnosť čo najvernejšej umelej inteligen- cie ovládajúcej herné prvky, na čo sa naša práca zameriava. Implementovali sme jednoduchú 2D programovaciu hru, na ktorej sme predviedli sadu poku- sov učiac umelú inteligenciu v nej, snažiac sa vytvoriť stratégie konkurujúce tým ľudským. Preskúmali sme niekoľko variácií učenia pomocou evolučnej stratégie aplikovanej na neurónové siete a vytvorili sme herné postavičky hodné bytia rovnocenným protivníkom užívateľom hry.Katedra teoretické informatiky a matematické logikyDepartment of Theoretical Computer Science and Mathematical LogicFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

IS pro elektronický obchod

Import 23/08/2007Prezenční456 - Katedra informatik

Hierarchické shlukování s Mahalanobis-average metrikou akcelerované na GPU

Hierarchical clustering algorithms are common tools for simplifying, exploring and analyzing datasets in many areas of research. For flow cytometry, a specific variant of agglomerative clustering has been proposed, that uses cluster linkage based on Mahalanobis distance to produce results better suited for the domain. Applicability of this clustering algorithm is currently limited by its relatively high computational complexity, which does not allow it to scale to common cytometry datasets. This thesis describes a specialized, GPU-accelerated version of the Mahalanobis-average linked hierarchical clustering, which improves the algorithm performance by several orders of magnitude, thus allowing it to scale to much larger datasets. The thesis provides an overview of current hierarchical clustering algorithms, and details the construction of the variant used on GPU. The result is benchmarked on publicly available high-dimensional data from mass cytometry.Hierarchické klastrovacie algoritmy sú bežnými nástromi na zjednodušenie, skúmanie a analýzu datasetov v mnohých oblastiach výskumu. Pre prietokovú cytometriu bol navrhnutý špecifický variant aglomeračného zhlukovania, ktorý využíva klastrovanie založené na Mahalanobisovskej vzdialenosti, aby sa dosiahli výsledky, ktoré sa pre danú doménu lepšie hodia. Uplatniteľnosť tohto klastrovacieho algoritmu je v súčasnosti obmedzená jeho pomerne vysokou výpočtovou náročnosťou, ktorá mu neumožňuje škálovať bežné cytometrické datasety. Táto práca popisuje špecializovanú, na GPU- zrýchlenú verziu hierarchického klastrovania založeného na Mahalanobisovskej vzdialenosti, ktorá zlepšuje výkon algoritmu o niekoľko rádov, čo mu umožňuje počítať oveľa väčšie datasety. Práca poskytuje prehľad súčasných hierarchických klastrovacích algoritmov a podrobne popisuje implementáciu algoritmu na GPU. Výsledok sa porovnáva s verejne dostupnými vysokorozmernými údajmi z hmotnostnej cytometrie.Department of Software EngineeringKatedra softwarového inženýrstvíMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

GPU-accelerated Mahalanobis-average hierarchical clustering

Hierarchical clustering algorithms are common tools for simplifying, exploring and analyzing datasets in many areas of research. For flow cytometry, a specific variant of agglomerative clustering has been proposed, that uses cluster linkage based on Mahalanobis distance to produce results better suited for the domain. Applicability of this clustering algorithm is currently limited by its relatively high computational complexity, which does not allow it to scale to common cytometry datasets. This thesis describes a specialized, GPU-accelerated version of the Mahalanobis-average linked hierarchical clustering, which improves the algorithm performance by several orders of magnitude, thus allowing it to scale to much larger datasets. The thesis provides an overview of current hierarchical clustering algorithms, and details the construction of the variant used on GPU. The result is benchmarked on publicly available high-dimensional data from mass cytometry