607 research outputs found
Pозробка методу контролю елементів конструкції планеру повітряних суден в умовах експлуатації
The paper proposes to use a method of infrared pulse-echo inspection to control airframe designelements, made of polymeric composite materials under operators` conditions. The following is described:skeleton operation diagram of the given method, device structure and results of the preliminary researchesconfirming operation capacity of the method offeredПредложено использовать инфракрасный эхо-импульсный метод для контроля элементов конструкции планера, изготовленного из полимерных композицитных материаловЗапропоновано використовувати інфрачервоний ехо-імпульсний метод для контролю елементів конструкціїпланера, виготовленого з полімерних композитних матеріалі
Orbitally induced hierarchy of exchange interactions in zigzag antiferromagnetic state of honeycomb silver delafossite Ag3Co2SbO6
We report the revised crystal structure, static and dynamic magnetic
properties of quasi-two dimensional honeycomb-lattice silver delafossite
Ag3Co2SbO6. The magnetic susceptibility and specific heat data are consistent
with the onset of antiferromagnetic long range order at low temperatures with
N\'eel temperature TN ~ 21.2 K. In addition, the magnetization curves revealed
a field-induced (spin-flop type) transition below TN in moderate magnetic
fields. The GGA+U calculations show the importance of the orbital degrees of
freedom, which maintain a hierarchy of exchange interaction in the system. The
strongest antiferromagnetic exchange coupling was found in the shortest Co-Co
pairs and is due to direct and superexchange interactions between the
half-filled xz+yz orbitals pointing directly to each other. The other four out
of six nearest neighbor exchanges within the cobalt hexagon are suppressed,
since for these bonds active half-filled orbitals turned out to be parallel and
do not overlap. The electron spin resonance (ESR) spectra reveal a Gaussian
shape line attributed to Co2+ ion in octahedral coordination with average
effective g-factor g=2.3+/-0.1 at room temperature and shows strong divergence
of ESR parameters below 120 K, which imply an extended region of short-range
correlations. Based on the results of magnetic and thermodynamic studies in
applied fields, we propose the magnetic phase diagram for the new
honeycomb-lattice delafossite
Underwater contamination by petroleum exploitation and disposal methods of hazardous substances at drilling
Geomagnetic storms and the occurrence of phase slips in the reception of GPS signals
We have investigated a dependence of the relative density of GPS phase slips on the geomagnetic disturbance level. The study is based on using Internet-available selected data from the global GPS network, with the simultaneously handled number of receiving stations ranging from 160 to 323. The analysis used four days from the period 1999-2000, with the values of the geomagnetic field disturbance index Dst from 5 to – 300 nT. During strong magnetic storms, the relative density of phase slips on mid-latitudes exceeds that for magnetically quiet days by one-two orders of magnitude as a minimum, and reaches a few percent of the total density of observations. Furthermore, the level of phase slips for the GPS satellites located on the sunward side of the Earth was by a factor of 5-10 larger compared with the opposite side of the Earth. The level of slips of L 1 phase measurements at the fundamental GPS frequency is at least one order of magnitude lower than that in L 1 – L 2 measurements. The slips of L 1 – L 2 measurements are most likely to be caused by the high level of slips of L 2 phase measurements at the auxiliary frequency. As an alternative, we developed and tested a new method for determining TEC variations using only data on the pseudo-range and phase measurements at fundamental frequency L 1 . The standard deviation of the TEC variations which were obtained in phase measurements at two frequencies, L 1 – L 2 , and at fundamental frequency L 1 , does not exceed 0.1 TECU, which permits this method to be used in strong disturbance conditions when phase slips at auxiliary frequency L 2 are observed
Design of Pre-Dumping Ring Spin Rotator with a Possibility of Helicity Switching for Polarized Positrons at the ILC
The use of polarized beams enhance the possibility of the precision
measurements at the International Linear Collider (ILC). In order to preserve
the degree of polarization during beam transport spin rotators are included in
the current TDR ILC Lattice. In this report some advantages of using a combined
spin rotator/spin flipper are discussed. A few possible lattice designs of spin
flipper developed at DESY in 2012 are presented.Comment: Talk presented at the International Workshop on Future Linear
Colliders (LCWS15), Whistler, Canada, 2-6 November 201
Novel electronic states close to Mott transition in low-dimensional and frustrated systems
Recent studies demonstrated that there may appear different novel states in
correlated systems close to localized-itinerant crossover. Especially
favourable conditions for that are met in low-dimensional and in frustrated
systems. In this paper I discuss on concrete examples some of such novel
states. In particular, for some spinels and triangular systems there appears a
"partial Mott transition", in which first some finite clusters (dimers, trimes,
tetramers, heptamers) go over to the itinerant regime, and the real bulk Mott
transition occurs only later. Also some other specific possibilities in this
crossover regime are shortly discussed, such as spin-Peierls-Peierls transition
in TiOCl, spontaneous charge disproportionation in some cases, etc.Comment: To be published in Journal of Physics - Condensed Matter, conference
serie
High-Performance Mn-Al-O Catalyst on Reticulated Foam Materials for Environmentally Friendly Catalytic Combustion
MnOx supported on alumina and La2O3-modified alumina have been prepared and characterized as methane combustion catalysts. X-ray diffraction (XRD) analysis has revealed the significant low-temperature interaction between MnOx and alumina, resulting in a solid solution Mn-La-γ*-Al2O3 and a hexaaluminate formation upon thermal treatment at 900-1000 ºC and 1300 ºC, respectively. Mn-Al-O and Mn-La-Al-O catalysts washcoated on highly porous reticulated foam materials (RFM) have been prepared by two methods, such as: 1) a wet impregnation of a washcoating alumina layer on RFM by Mn and La nitrate solutions, 2) a dip coating of RFM into Mn-La-Al-containing suspension. The chemical compositions of RFM were cordierite, Ni, and NiCr-alloy. The catalytic activity of washcoated RFM in the methane combustion has been compared with one of granulated catalysts. The influence of alumina form (γ-Al2O3, (γ+χ)-Al2O3, α-Al2O3), manganese loading (5 and 10 wt.%), modifying agent (La2O3) on catalytic activity have been studied. Catalytic performances of Mn-Al-O and Mn-La-Al-O catalysts washcoated on RFM and pretreated in methane-containing atmosphere at 1100 ºC have been investigated. The Mn-Al-O catalyst modified by La2O3 and supported on RFM have been tested in a prototype catalytic water heating boiler and demonstrated a considerable reduction in the emissions of NOx and CO compared to the conventional household boilers. The washcoating of the Mn-La-Al-O catalyst over surface of RFM provides a substantial reduction of toxic emissions during the catalytic fuel combustion. While an optimal foam structure and composition of the RFM provide improved heat and mass transfer properties of the catalyst in fuel combustion
The spike train statistics for consonant and dissonant musical accords
The simple system composed of three neural-like noisy elements is considered.
Two of them (sensory neurons or sensors) are stimulated by noise and periodic
signals with different ratio of frequencies, and the third one (interneuron)
receives the output of these two sensors and noise. We propose the analytical
approach to analysis of Interspike Intervals (ISI) statistics of the spike
train generated by the interneuron. The ISI distributions of the sensory
neurons are considered to be known. The frequencies of the input sinusoidal
signals are in ratios, which are usual for music. We show that in the case of
small integer ratios (musical consonance) the input pair of sinusoids results
in the ISI distribution appropriate for more regular output spike train than in
a case of large integer ratios (musical dissonance) of input frequencies. These
effects are explained from the viewpoint of the proposed theory.Comment: 22 pages, 6 figure
Invariant variational principle for Hamiltonian mechanics
It is shown that the action for Hamiltonian equations of motion can be
brought into invariant symplectic form. In other words, it can be formulated
directly in terms of the symplectic structure without any need to
choose some 1-form , such that , which is not unique
and does not even generally exist in a global sense.Comment: final version; to appear in J.Phys.A; 17 pages, 2 figure
Synthesis of Nanoscale TiO2 and Study of the Effect of Their Crystal Structure on Single Cell Response
To study the effect of nanoscale titanium dioxide (TiO2) on cell responses, we synthesized four modifications of the TiO2 (amorphous, anatase, brookite, and rutile) capable of keeping their physicochemical characteristics in a cell culture medium. The modifications of nanoscale TiO2 were obtained by hydrolysis of TiCl4 and Ti(i-OC3H7)4 (TIP) upon variation of the synthesis conditions; their textural, morphological, structural, and dispersion characteristics were examined by a set of physicochemical methods: XRD, BET, SAXS, DLS, AFM, SEM, and HR-TEM. The effect of synthesis conditions (nature of precursor, pH, temperature, and addition of a complexing agent) on the structural-dispersion properties of TiO2 nanoparticles was studied. The hydrolysis methods providing the preparation of amorphous, anatase, brookite, and rutile modifications of TiO2 nanoparticles 3–5 nm in size were selected. Examination of different forms of TiO2 nanoparticles interaction with MDCK cells by transmission electron microscopy of ultrathin sections revealed different cell responses after treatment with different crystalline modifications and amorphous form of TiO2. The obtained results allowed us to conclude that direct contact of the nanoparticles with cell plasma membrane is the primary and critical step of their interaction and defines a subsequent response of the cell
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