Fyzikalni Ustav AV CR

Prague, Czech Republic

Fyzikalni Ustav AV CR

Prague, Czech Republic
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Lipton-Duffin J.A.,Center for Energy | Macleod J.M.,Center for Energy | Vondracek M.,Fyzikalni Ustav AV CR | Prince K.C.,Elettra - Sincrotrone Trieste | And 3 more authors.
Physical Chemistry Chemical Physics | Year: 2014

We have performed a high-resolution synchrotron radiation photoelectron spectroscopy study of the initial growth stages of the ZnPd near-surface alloy on Pd(111), complemented by scanning tunnelling microscopy data. We show that the chemical environment for surfaces containing less than half of one monolayer of Zn is chemically distinct from subsequent layers. Surfaces where the deposition is performed at room temperature contain ZnPd islands surrounded by a substrate with dilute Zn substitutions. Annealing these surfaces drives the Zn towards the substrate top-layer, and favours the completion of the first 1:1 monolayer before the onset of growth in the next layer. © 2014 the Owner Societies.

Cardenas L.,University of Québec | Cardenas L.,McGill University | Gutzler R.,University of Québec | Gutzler R.,McGill University | And 10 more authors.
Chemical Science | Year: 2013

We report the synthesis and first electronic characterization of an atomically thin two dimensional π-conjugated polymer. Polymerization via Ullmann coupling of a tetrabrominated tetrathienoanthracene on Ag(111) in ultra-high vacuum (UHV) produces a porous 2D polymer network that has been characterized by scanning tunnelling microscopy (STM). High-resolution X-ray photoelectron spectroscopy (HRXPS) shows that the reaction proceeds via two distinct steps: dehalogenation of the brominated precursor, which begins at room temperature (RT), and C-C coupling of the resulting Ag-bound intermediates, which requires annealing at 300 °C. The formation of the 2D conjugated network is accompanied by a shift of the occupied molecular states by 0.6 eV towards the Fermi level, as observed by UV photoelectron spectroscopy (UPS). A theoretical analysis of the electronic gap reduction in the transition from monomeric building blocks to various 1D and 2D oligomers and polymers yields important insight into the effect of topology on the electronic structure of 2D conjugated polymers. © 2013 The Royal Society of Chemistry.

Fu Q.,KTH Royal Institute of Technology | Fu Q.,Plasmatrix Materials AB | Lorite G.S.,University of Oulu | Rashid M.M.-U.,KTH Royal Institute of Technology | And 12 more authors.
Carbon | Year: 2016

Nanostructured Cu:CuCNx composite coatings with high static and dynamic stiffness were synthesized by means of plasma-enhanced chemical vapor deposition (PECVD) combined with high power impulse magnetron sputtering (HiPIMS). Scanning electron microscope (SEM) images and energy-dispersive X-ray spectroscopy (EDS) mapping from cross-sectioned samples reveals a multi-layered nanostructure enriched in Cu, C, N, and O in different ratios. Mechanical properties of the coatings were investigated by Vickers micro-indention and model tests. It was observed that copper inclusions as well as copper interlayers in the CNx matrix can increase mechanical damping by up to 160%. Mechanical properties such as hardness, elastic modulus and loss factor were significantly improved by increasing the discharge power of the sputtering process. Moreover the coatings loss modulus was evaluated on the basis of indentation creep measurements under room temperature. The coating with optimum properties exhibited loss modulus of 2.6 GPa. The composite with the highest damping loss modulus were applied on the clamping region of a milling machining tool to verify their effect in suppressing regenerative tool chatter. The high dynamic stiffness coatings were found to effectively improve the critical stability limit of a milling tool by at least 300%, suggesting a significant increase of the dynamic stiffness. © 2015 The Authors. Published by Elsevier Ltd.

Starman S.,Starmans electronics | Matz V.,Starmans electronics | Kvaca Z.,Molecular cybernetics | Mohyla M.,Molecular cybernetics | And 4 more authors.
NANOCON 2011 - Conference Proceedings, 3rd International Conference | Year: 2011

Based on the known Aurivillius phases types ABi2Ta2O9 and A2BiTaO6 (A=Ca,Sr,Ba) ) were supplemented with new compositions of layered tantalates, which resulted the possibility of the existence of a new phase Sr2BiTaO6. Ternary compounds with piezoelectric structure were prepared as nanoforms by solgel reactions of homogeneous acetate Bi, Ta, A and subsequent annealing in a controlled atmosphere. Annealing temperature was determined from DSC curves based on the weight loss and phase transitions. Composition and structure of nanocrystals has been analyzed by X-ray diffraction (XRD), scanning nanomorphology (SEM) and acoustic measurements. © 2011 TANGER Ltd., Ostrava.

Fyzikalni Ustav Av Cr and Oerlikon Solar Ltd. | Date: 2010-09-16

A photovoltaic cell (10) is fabricated by depositing a first transparent conductive layer (12) onto a substrate carrier (11). Portions of the first transparent conductive layer (12) are selectively removed to form a plurality of discrete transparent conductive protruding regions (13) or a plurality of discrete indentations (27) in the first transparent conductive layer (12). A silicon layer (14) comprising a charge separating junction is deposited onto the plurality of discrete protruding regions (13) or onto the plurality of discrete indentations (27) by chemical vapour deposition. A second transparent conductive layer (15) is deposited on the silicon layer (14) by chemical vapour deposition.

Heczko O.,Fyzikalni Ustav AV CR | Kopecek J.,Fyzikalni Ustav AV CR | Straka L.,Aalto University | Seiner H.,Czech Institute of Thermomechanics
Materials Research Bulletin | Year: 2013

We investigated twin boundaries with sharply different mobility or twinning stress in five-layered modulated (10 M) martensite of Ni-Mn-Ga exhibiting magnetic shape memory effect or magnetically induced reorientation. Different mobility is ascribed to the different microstructures of the macrotwin planar interface. In monoclinic approximation the mobile boundaries are of Type I and Type II with complex microstructure of adjoining variants. These boundaries respond differently to magnetic field. For Type II boundary the reorientation takes place at very low field 250 Oe. © 2013 Elsevier Ltd. All rights reserved.

Vicha J.,Fyzikalni Ustav AV CR | Chudoba J.,Fyzikalni Ustav AV CR
Journal of Physics: Conference Series | Year: 2015

Cosmic-ray particles with ultra-high energies (above 1018 eV) are studied through the properties of extensive air showers which they initiate in the atmosphere. The Pierre Auger Observatory detects these showers with unprecedented exposure and precision and the collected data are processed via dedicated software codes. Monte Carlo simulations of extensive air showers are very computationally expensive, especially at the highest energies and calculations are performed on the GRID for this purpose. The processing of measured and simulated data is described, together with a brief list of physics results which have been achieved. © Published under licence by IOP Publishing Ltd.

Berta M.,Fyzikalni Ustav AV CR | Kadlec F.,Fyzikalni Ustav AV CR
Phase Transitions | Year: 2010

We report on results of a near-field imaging experiment with broadband terahertz pulses applied to a BaTiO 3 multidomain single crystal. Data with a spatial resolution below 15μm were collected by our scanning time-domain terahertz imaging setup. We performed the scanning by an asymmetric skewed sapphire probe metallised from two sides ended with a 60 μm × 140μm facet. The imaging scans were performed with various angles of the polarisation of the probing field with respect to the direction of the domain walls in order to identify the orientations with optimal sensitivity. The raw experimental data were prewhitened and processed by the singular value decomposition. In this way, independent components belonging to experimental features (polarisation, noise and external perturbations) were found. The spatial resolution of the sensing probe was found significantly higher than that allowed by the outer dimensions of the probe end facet. This result was also confirmed by electromagnetic-field simulations. © 2010 Taylor & Francis.

Kouba T.,Fyzikalni Ustav AV CR | Chudoba J.,Fyzikalni Ustav AV CR | Elias M.,Fyzikalni Ustav AV CR | Fiala L.,Fyzikalni Ustav AV CR
Journal of Physics: Conference Series | Year: 2012

Computing Center of the Institute of Physics in Prague provides computing and storage resources for various HEP experiments (D0, Atlas, Alice, Auger) and currently operates more than 300 worker nodes with more than 2500 cores and provides more than 2PB of disk space. Our site is limited to one C-sized block of IPv4 addresses, and hence we had to move most of our worker nodes behind the NAT. However this solution demands more difficult routing setup. We see the IPv6 deployment as a solution that provides less routing, more switching and therefore promises higher network throughput. The administrators of the Computing Center strive to configure and install all provided services automatically. For installation tasks we use PXE and kickstart, for network configuration we use DHCP and for software configuration we use CFEngine. Many hardware boxes are configured via specific web pages or telnet/ssh protocol provided by the box itself. All our services are monitored with several tools e.g. Nagios, Munin, Ganglia. We rely heavily on the SNMP protocol for hardware health monitoring. All these installation, configuration and monitoring tools must be tested before we can switch completely to IPv6 network stack. In this contribution we present the tests we have made, limitations we have faced and configuration decisions that we have made during IPv6 testing. We also present testbed built on virtual machines that was used for all the testing and evaluation.

Necesal P.,Fyzikalni Ustav AV CR
Journal of Physics: Conference Series | Year: 2011

The Pierre Auger Observatory is a facility designed for the study of ultra-high energy cosmic rays. The Observatory combines two different types of detectors: a surface array of 1600 water Cherenkov stations placed on a 1.5 km triangular grid covering over 3000 km2; and a fluorescence detector of 24 telescopes located in 4 buildings at the perimeter of the surface array. The fluorescence telescopes, each consisting of 440 photomultipliers, collect the ultraviolet light produced when the charged secondary particles in an air shower excite nitrogen molecules in the atmosphere. Because the intensity of the nitrogen fluorescence is proportional to the energy deposited in the atmosphere during the air shower, the air fluorescence measurements can be used to make a calorimetric measurement of the cosmic ray primary energy. Showers observed independently by the surface array and fluorescence telescopes, called hybrid events, are critical to the function of the Observatory, as they allow for a model-independent calibration of the surface detector. In this paper I describe the detector and the most important measurements.

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