Showing papers by "University of West Bohemia published in 2018"

CAVER Analyst 2.0: analysis and visualization of channels and tunnels in protein structures and molecular dynamics trajectories.

Abstract: Motivation: Studying the transport paths of ligands, solvents, or ions in transmembrane proteins and proteins with buried binding sites is fundamental to the understanding of their biological function. A detailed analysis of the structural features influencing the transport paths is also important for engineering proteins for biomedical and biotechnological applications. Results: CAVER Analyst 2.0 is a software tool for quantitative analysis and real-time visualization of tunnels and channels in static and dynamic structures. This version provides the users with many new functions, including advanced techniques for intuitive visual inspection of the spatiotemporal behavior of tunnels and channels. Novel integrated algorithms allow an efficient analysis and data reduction in large protein structures and molecular dynamic simulations. Availability and implementation: CAVER Analyst 2.0 is a multi-platform standalone Java-based application. Binaries and documentation are freely available at www.caver.cz.

Molecular Profiling of Mammary Analog Secretory Carcinoma Revealed a Subset of Tumors Harboring a Novel ETV6-RET Translocation: Report of 10 Cases.

Abstract: ETV6 gene abnormalities are well described in tumor pathology. Many fusion partners of ETV6 have been reported in a variety of epithelial, mesenchymal, and hematological malignancies. In salivary gland tumor pathology, however, the ETV6-NTRK3 translocation is specific for (mammary analog) secretory carcinoma, and has not been documented in any other salivary tumor type. The present study comprised a clinical, histologic, and molecular analysis of 10 cases of secretory carcinoma, with typical morphology and immunoprofile harboring a novel ETV6-RET translocation.

Thermal Conductivity and Electrical Resistivity of Solid Iron at Earth's Core Conditions from First Principles.

Abstract: We compute the thermal conductivity and electrical resistivity of solid hcp Fe to pressures and temperatures of Earth's core. We find significant contributions from electron-electron scattering, usually neglected at high temperatures in transition metals. Our calculations show a quasilinear relation between the electrical resistivity and temperature for hcp Fe at extreme high pressures. We obtain thermal and electrical conductivities that are consistent with experiments considering reasonable error. The predicted thermal conductivity is reduced from previous estimates that neglect electron-electron scattering. Our estimated thermal conductivity for the outer core is $77\ifmmode\pm\else\textpm\fi{}10\text{ }\text{ }\mathrm{W}\text{ }{\mathrm{m}}^{\ensuremath{-}1}\text{ }{\mathrm{K}}^{\ensuremath{-}1}$ and is consistent with a geodynamo driven by thermal convection.

Magnesium Oxide Nanoparticles: Dielectric Properties, Surface Functionalization and Improvement of Epoxy-Based Composites Insulating Properties

Abstract: Composite insulation materials are an inseparable part of numerous electrical devices because of synergy effect between their individual parts. One of the main aims of the presented study is an introduction of the dielectric properties of nanoscale magnesium oxide powder via Broadband Dielectric Spectroscopy (BDS). These unique results present the behavior of relative permittivity and loss factor in frequency and temperature range. Following the current trends in the application of inorganic nanofillers, this article is complemented by the study of dielectric properties (dielectric strength, volume resistivity, dissipation factor and relative permittivity) of epoxy-based composites depending on the filler amount (0, 0.5, 0.75, 1 and 1.25 weight percent). These parameters are the most important for the design and development of the insulation systems. The X-ray diffraction patterns are presented for pure resin and resin with optimal filler amount (1 wt %), which was estimated according to measurement results. Magnesium oxide nanoparticles were also treated by addition of silane coupling agent ( γ -Glycidoxypropyltrimethoxysilane), in the case of optimal filler loading (1 wt %) as well. Besides previously mentioned parameters, the effects of surface functionalization have been observed by two unique measurement and evaluation techniques which have never been used for this evaluation, i.e., reduced resorption curves (RRCs) and voltage response method (VR). These methods (developed in our departments), extend the possibilities of measurement of composite dielectric responses related to DC voltage application, allow the facile comparability of different materials and could be used for dispersion level evaluation. This fact has been confirmed by X-ray diffraction analyses.

Electromagnetic Radiation Efficiency of Body-Implanted Devices

Abstract: Autonomous wireless body-implanted devices for biotelemetry, telemedicine, and neural interfacing constitute an emerging technology providing powerful capabilities for medicine and clinical research. We study the through-tissue electromagnetic propagation mechanisms, derive the optimal frequency range, and obtain the maximum achievable efficiency for radiative energy transfer from inside a body to free space. We analyze how polarization affects the efficiency by exciting TM and TE modes using a magnetic dipole and a magnetic current source, respectively. Four problem formulations are considered with increasing complexity and realism of anatomy. The results indicate that the optimal operating frequency f for deep implantation (with a depth d greater than or similar to 3 cm) lies in the (10(8)-10(9))-Hz range and can be approximated as f = 2.2 x 10(7)/d. For a subcutaneous case (d less than or similar to 3 cm), the surface-wave-induced interference is significant: within the range of peak radiation efficiency (about 2 x 10(8) to 3 x 10(9) Hz), the max-to-min ratio can reach a value of 6.5. For the studied frequency range, 80%-99% of radiation efficiency is lost due to the tissue-air wave-impedance mismatch. Parallel polarization reduces the losses by a few percent; this effect is inversely proportional to the frequency and depth. Considering the implantation depth, the operating frequency, the polarization, and the directivity, we show that about an order-of-magnitude efficiency improvement is achievable compared to existing devices.

Adaptive Speed Control of Induction Motor Drive With Inaccurate Model

Abstract: An adaptive controller for the speed control of induction motor (IM) drives with inaccurate models is designed in this paper. Specifically, we assume that every equation in the state-space model of the drive is subject to slowly varying error. The proposed controller is composed of an adaptive feedforward control term, which compensates for the nonlinear and uncertain factors, and a feedback control term, which guarantees the system stability. The proposed scheme is not only simple and easy to implement, but also it guarantees a precise and fast speed tracking. Stability of the proposed speed controller is confirmed using the Lyapunov theorem and a related lemma. The designed control algorithm is compared to a controller based on nonadaptive feedback linearization control (FLC), conventional field oriented control (FOC), and adaptive backstepping sliding mode control (ABSMC). Experiments on a developed IM drive prototype of rated power of 4 kW confirm good control performance [better robustness, smaller mean square, and maximum absolute errors (MAEs)] compared to the competitors, especially in the case of severe parameter mismatch between the real drive and model used for controller design.

Visible-Light-Responsive Sillén-Structured Mixed-Cationic CdBiO2Br Nanosheets: Layer Structure Design Promoting Charge Separation and Oxygen Activation Reactions

Abstract: Exploration for new layered-structured materials is of significance in multiple fields, e.g., catalysis, energy storage, and conversion, etc. In this work, we develop a visible-light-responsive Sillen-structured mixed-cationic layered catalyst CdBiO2Br based on the typical Sillen-structured BiOBr, and first propose layer structure design as a novel tactic for promoting charge separation and oxygen activation reactions. Differing from BiOBr characterized by [Bi2O2]2+ layer and interleaved Br– double slabs, the crystal structure of CdBiO2Br comprises the [CdBiO2]+ layer and interbedded single Br– slice, rendering a narrowed interlayer spacing from 8.11 to 6.23 A. The largely reduced interlayer distance drastically shortens the diffusion paths of photogenerated electrons (e–) and holes (h+) in CdBiO2Br, allowing favorable migration of carriers from bulk to the surface of the catalysts. Profiting from this structural advantage, CdBiO2Br presents a superior visible-light driven oxygen activation ability in evo...

Observation of proton-tagged, central (semi)exclusive production of high-mass lepton pairs in pp collisions at 13 TeV with the CMS-TOTEM precision proton spectrometer

Abstract: The process pp → pl+l−p(*), with l+l− a muon or an electron pair produced at midrapidity with mass larger than 110 GeV, has been observed for the first time at the LHC in pp collisions at $$ \sqrt{s}=13 $$ TeV. One of the two scattered protons is measured in the CMS-TOTEM precision proton spectrometer (CT-PPS), which operated for the first time in 2016. The second proton either remains intact or is excited and then dissociates into a low-mass state p*, which is undetected. The measurement is based on an integrated luminosity of 9.4 fb−1 collected during standard, high-luminosity LHC operation. A total of 12 μ+μ− and 8 e+e− pairs with m(l+l−) > 110 GeV, and matching forward proton kinematics, are observed, with expected backgrounds of 1.49 ± 0.07 (stat) ± 0.53 (syst) and 2.36 ± 0.09 (stat) ± 0.47 (syst), respectively. This corresponds to an excess of more than five standard deviations over the expected background. The present result constitutes the first observation of proton-tagged γγ collisions at the electroweak scale. This measurement also demonstrates that CT-PPS performs according to the design specifications.

Control of a Single-Phase Cascaded H-Bridge Active Rectifier Under Unbalanced Load

Abstract: Cascaded H-bridge (CHB) converter technology is actually the most popular solution for grid-connected converters in both medium- and high-voltage applications. This paper introduces a new control of a single-phase CHB active rectifier. The control uses a direct grid current control based on adaptive resonant controllers. The resonant controllers are adapting to slow fluctuation of ac grid frequency. The challenging problem of CHB converters is dc-link capacitor voltage balancing especially under unbalanced load conditions. This paper presents a reliable voltage-balancing technique utilizing energy estimation of particular dc-link capacitor banks and simple prediction of the changes of their energies. A nonlinear behavior of the converter caused by power semiconductors voltage drops and dead-time effects is minimized by auxiliary adaptive resonant controllers. The resulting control has very good performance, including the operation under unbalanced load conditions, and achieves low total harmonic distortion of converter grid current. The theoretical results were verified by experiments made on the developed CHB active rectifier prototype with three power cells in cascade.

Ab Initio Investigation of the Structural, Electronic and Optical Properties of the Li 2 In 2 XY 6 (X = Si, Ge; Y = S, Se) Compounds

Abstract: The structural, electronic and optical properties of the Li2In2XY6 (X = Si, Ge; Y = S, Se) compounds, which are scarcely studied by theoretical methods previously, have been investigated by ab initio calculations based on the density functional theory (DFT) in this article by using the full potential linearized augmented plane wave method The equilibrium structural ground state properties of the Li2In2XY6 (X = Si, Ge; Y = S, Se) compounds such as the lattice parameters were obtained from the structural optimization process (with the Perdew–Burke–Ernzerhof generalized gradient approximation), and they are in close agreement with the experimental lattice parameters Conversely, calculations by the modified Becke Johnson exchange potential indicates that the Li2In2XY6 (X = Si, Ge; Y = S, Se) compounds are semiconductors with direct energy band gaps It is clearly observed from the DFT-calculated partial density of states, that there are significant contributions of the S-s and S-p states in the Li2In2SiS6 and Li2In2GeS6 compounds as well as the Se-s and Se-p states in the Li2In2SiSe6 and Li2In2GeSe6 compounds, respectively The calculated band gaps ranging from 192 eV to 324 eV of the Li2In2XY6 (X = Si, Ge; Y = S, Se) compounds are in good agreement with the experimental results, where the calculated band gap values are positioned in the visible region of the electromagnetic spectrum; therefore, these materials can be efficiently used for opto-electronic and optical applications Furthermore, some general trends are observed in the optical responses of the compounds, which are possibly correlated to the energy band gaps when the X cations changes from Si to Ge and the Y anions changes from S to Se in the Li2In2XY6 (X = Si, Ge; Y = S, Se) compounds, respectively

ZnO Coated Anodic 1D TiO2 Nanotube Layers: Efficient Photo‐Electrochemical and Gas Sensing Heterojunction

Abstract: The authors demonstrate, in this work, a fascinating synergism of a high surface area heterojunction between TiO2 in the form of ordered 1D anodic nanotube layers of a high aspect ratio and ZnO coatings of different thicknesses, produced by atomic layer deposition. The ZnO coatings effectively passivate the defects within the TiO2 nanotube walls and significantly improve their charge carrier separation. Upon the ultraviolet and visible light irradiation, with an increase of the ZnO coating thickness from 0.19 to 19 nm and an increase of the external potential from 0.4–2 V, yields up to 8-fold enhancement of the photocurrent density. This enhancement translates into extremely high incident photon to current conversion efficiency of ≈95%, which is among the highest values reported in the literature for TiO2 based nanostructures. In addition, the photoactive region is expanded to a broader range close to the visible spectral region, compared to the uncoated nanotube layers. Synergistic effect arising from ZnO coated TiO2 nanotube layers also yields an improved ethanol sensing response, almost 11-fold compared to the uncoated nanotube layers. The design of the high-area 1D heterojunction, presented here, opens pathways for the light- and gas-assisted applications in photocatalysis, water splitting, sensors, and so on.

Actor-Critic Off-Policy Learning for Optimal Control of Multiple-Model Discrete-Time Systems.

Abstract: In this paper, motivated by human neurocognitive experiments, a model-free off-policy reinforcement learning algorithm is developed to solve the optimal tracking control of multiple-model linear discrete-time systems. First, an adaptive self-organizing map neural network is used to determine the system behavior from measured data and to assign a responsibility signal to each of system possible behaviors. A new model is added if a sudden change of system behavior is detected from the measured data and the behavior has not been previously detected. A value function is represented by partially weighted value functions. Then, the off-policy iteration algorithm is generalized to multiple-model learning to find a solution without any knowledge about the system dynamics or reference trajectory dynamics. The off-policy approach helps to increase data efficiency and speed of tuning since a stream of experiences obtained from executing a behavior policy is reused to update several value functions corresponding to different learning policies sequentially. Two numerical examples serve as a demonstration of the off-policy algorithm performance.

O(lgN) Line Clipping Algorithm in E2

Abstract: A new O(lg N) line clipping algorithm in E2 against a convex window is presented. The main advantage of the presented algorithm is the principal acceleration of the line clipping problem solution. A comparison of the proposed algorithm with others shows a significant improvement in run-time. Experimental results for selected known algorithms are also shown.

Active photocatalytic water splitting solar-to-hydrogen energy conversion: Chalcogenide photocatalyst Ba2ZnSe3 under visible irradiation

Abstract: The photocatalytic performance of Ba2ZnSe3 is investigated by means of density functional theory. The investigation confirms that Ba2ZnSe3 possesses large birefringence, considerable anisotropy in the optical response, and the absorption edge occurs in the visible region. The estimated optical band gap of Ba2ZnSe3 is about 2.70 eV, and the EPc and EPv are about −0.145 V(vs.NHE) and +2.605 V (vs.NHE), respectively. Thus, Ba2ZnSe3 possesses a high negative reduction potential of excited electrons due to its higher CB position, and hence, the location of the CBM and VBM accommodates the redox capacity. Thus, the Ba2ZnSe3 photocatalyst is expected to exhibit superior activity in visible-light-driven photocatalytic H2 evolution. The electronic band structure shows high k-dispersion bands around the Fermi level, which implies low effective masses and, hence, the high mobility carriers enhance the charge transfer process. It was found that Ba2ZnSe3 possesses a great effective mass difference between electron (e−) and hole (h+), which can facilitate the e− and h+ migration and separation, and finally improve the photocatalytic performance. The observed large mobility difference in Ba2ZnSe3 is useful to the separation of e− and h+, reduction of the e− and h+ recombination rate, and improvement of the photocatalytic activity. Thus, Ba2ZnSe3 could be a good photocatalyst due to rapid generation of e−– h+ pairs with photoexcitation, and a high negative reduction potential of excited electrons due to its higher CB position. The excellent photocatalytic performance of Ba2ZnSe3 is due to hyperpolarizablity formed by ZnO4 tetrahedra and co-parallel BaSe7 polyhedra groups, and the layer structure favors the enhancement of the photocatalytic performance. The presence of the distorted (ZnO4)4− tetrahedral causes to increase the efficiency of the photocatalytic performance almost to double in comparison to other chalcogenide crystals. Based on these results, one can conclude that Ba2ZnSe3 satisfies all requirements to be an efficient photocatalyst. This will greatly improve the search efficiency and greatly help experiments to save resources in the exploration of new photocatalysts with good photocatalytic performance.

Ammonothermal Synthesis and Optical Properties of Ternary Nitride Semiconductors Mg-IV-N2 , Mn-IV-N2 and Li-IV2 -N3 (IV=Si, Ge).

Abstract: Grimm-Sommerfeld analogous nitrides MgSiN2 , MgGeN2 , MnSiN2 , MnGeN2 , LiSi2 N3 and LiGe2 N3 (generally classified as II-IV-N2 and I-IV2 -N3 ) are promising semiconductor materials with great potential for application in (opto)electronics or photovoltaics. A new synthetic approach for these nitride materials was developed using supercritical ammonia as both solvent and nitride-forming agent. Syntheses were conducted in custom-built high-pressure autoclaves with alkali metal amides LiNH2 , NaNH2 or KNH2 as ammonobasic mineralizers, which accomplish an adequate solubility of the starting materials and promote the formation of reactive intermediate species. The reactions were performed at temperatures between 870 and 1070 K and pressures up to 230 MPa. All studied compounds crystallize in wurtzite-derived superstructures with orthorhombic space groups Pna21 (II-IV-N2 ) and Cmc21 (I-IV2 -N3 ), respectively, which was confirmed by powder X-ray diffraction. Optical bandgaps were estimated from diffuse reflectance spectra using the Kubelka-Munk function (MgSiN2 : 4.8 eV, MgGeN2 : 3.2 eV, MnSiN2 : 3.5 eV, MnGeN2 : 2.5 eV, LiSi2 N3 : 4.4 eV, LiGe2 N3 : 3.9 eV). Complementary DFT calculations were carried out to gain insight into the electronic band structures of these materials and to corroborate the optical measurements.

TaS3 Nanofibers: Layered Trichalcogenide for High-Performance Electronic and Sensing Devices

Abstract: Layered materials, like transition metal dichalcogenides, exhibit broad spectra with outstanding properties with huge application potential, whereas another group of related materials, layered transition metal trichalcogenides, remains unexplored. Here, we show the broad application potential of this interesting structural type of layered tantalum trisulfide prepared in a form of nanofibers. This material shows tailorable attractive electronic properties dependent on the tensile strain applied to it. Structure of this so-called orthorhombic phase of TaS3 grown in a form of long nanofibers has been solved and refined. Taking advantage of these capabilities, we demonstrate a highly specific impedimetric NO gas sensor based on TaS3 nanofibers as well as construction of photodetectors with excellent responsivity and field-effect transistors. Various flexible substrates were used for the construction of a NO gas sensor. Such a device exhibits a low limit of detection of 0.48 ppb, well under the allowed value s...

Delegate MASs for coordination and control of one-directional AGV systems: a proof-of-concept

Abstract: Decentralized coordination and route planning face the challenges such as scalability, dynamic changes (disturbances) in the environment, continuous planning, and coordination issues (i.e., deadlock and livelock situations). Self-organized delegate multi-agent systems (D-MASs) have proven to be effective decentralized coordination mechanisms for coordination and control (C&C) applications. However, the use of such coordination mechanisms becomes more challenging, compared to the previous studies, in which the coordinated entities are one-directional automated guided vehicles (AGVs), with restricted movement, situated in a highly dynamic production environment. To address these challenges, there were several problematic situations identified dealing with issues such as the originally proposed functionalities of D-MASs, restricted movement, priority parameter settings, and simulated failures of AGVs. Solutions (coordination rules) to these situations were proposed, also described examples were provided and, finally, the approach was verified by simulation in the 3D environment, involving five AGV agents (AGVAs). Simple indicators of such intralogistics system were proposed to outline the system performance. Simulations were performed with as well as without simulated failure states. Simulation results show that the proof-of-concept was reached, and that by the combination of the proposed coordination rules and D-MAS, one-directional AGVAs were able to generate a short-term forecast for the near future and thus anticipate and avoid coordination issues as well as to cope with simulated failures.

Effect of Nozzle Geometry on the Microstructure and Properties of HVAF-Sprayed WC-10Co4Cr and Cr 3 C 2 -25NiCr Coatings

Abstract: Thermally sprayed hard metal coatings are the industrial standard solution for numerous demanding applications to improve wear resistance. In the aim of improving coating quality by utilising finer particle size distributions, several approaches have been studied to control the spray temperature. The most viable solution is to use the modern high velocity air-fuel (HVAF) spray process, which has already proven to produce high-quality coatings with dense structures. In HVAF spray process, the particle heating and acceleration can be efficiently controlled by changing the nozzle geometry. In this study, fine WC-10Co4Cr and Cr3C2-25NiCr powders were sprayed with three nozzle geometries to investigate their effect on the particle temperature, velocity and coating microstructure. The study demonstrates that the particle melting and resulting carbide dissolution can be efficiently controlled by changing the nozzle geometry from cylindrical to convergent–divergent. Moreover, the average particle velocity was increased from 780 to over 900 m/s. The increase in particle velocity significantly improved the coating structure and density. Further evaluation was carried out to resolve the effect of particle in-flight parameters on coating structure and cavitation erosion resistance, which was significantly improved in the case of WC-10Co4Cr coatings with the increasing average particle velocity.

Current State of Text-to-Speech System ARTIC: A Decade of Research on the Field of Speech Technologies

Abstract: This paper provides a survey of the current state of ARTIC – the modern Czech concatenative corpus-based text-to-speech system Through more than a decade of research & development in the field of speech technologies and applications, the system was enriched with new languages (and, as a consequence, language-dependent NLP methods), and its speech generation capabilities were significantly improved when new progressive speech generation modules (SPS, DNN, HSS) were (and are still being to) designed and incorporated into it Also, ARTIC has to deal with various requirements on data used to generate speech from, ranging in size, quality and domain of the output speech, while there always was the requirement to achieve the highest quality in terms of both naturalness and intelligibility Thus, the paper summarizes some of the most significant achievements and demanding tasks which had to be tackled by the system, illustrating the universality and flexibility of this Czech TTS system

Operando Imaging of All-Electric Spin Texture Manipulation in Ferroelectric and Multiferroic Rashba Semiconductors

Abstract: The control of the electron spin by external means is a key issue for spintronic devices. Using spin- and angle-resolved photoemission spectroscopy (SARPES) with three-dimensional spin detection, we demonstrate operando electrostatic spin manipulation in ferroelectric alpha-GeTe and multiferroic Ge1-xMnxTe. We demonstrate for the first time electrostatic spin manipulation in Rashba semiconductors due to ferroelectric polarization reversal. Additionally, we are also able to follow the switching pathway in detail. In multiferroic Ge1-xMnxTe operando SARPES reveals switching of the perpendicular spin component due to electric-field-induced magnetization reversal. This provides firm evidence of magnetoelectric coupling which opens up functionality with a multitude of spin-switching paths in which the magnetic and electric order parameters are coupled through ferroelastic relaxation paths. This work thus provides a new type of magnetoelectric switching intertwined with Rashba-Zeeman splitting in a multiferroic system.