5,894 research outputs found
ОЦЕНКА ЭНЕРГЕТИЧЕСКОЙ ЕФФЕКТИВНОСТИ ПАРАЛЛЕЛЬНОГО КВАЗИРЕЗОНАНСНОГО ПРЕОБРАЗОВАТЕЛЯ
The processing in experimental specimen of parallel quasi-resonant zero current switch converter (QR-ZCS) is considered. The advantages of QR-ZCS’ structural design are shown. The results of experimental researches of energy efficiency of parallel QR-ZCS converter are published. References 3, tables 1, figures 2.Исследована работа экспериментального макета параллельного квазирезонансного импульсного преобразователя, переключаемого при нулевом токе(КРИП-ПНТ). Показаны достоинства его структурного построения. Приведены результаты экспериментальных исследований энергетической эффективности параллельного КРИП- ПНТ. Библ. 3, табл. 1, рис. 2
Thermally stable composite system Al2O3-Ce 0.75Zr0.25O2 for automotive three-way catalysts
Present-day three-way catalysts operate in contact with exhaust gases whose temperature is as high as >1000 C, so the problem of developing thermally stable catalytic compositions is still topical. A series of Al2O 3-Ce0.75Zr0.25O2 composites containing 0, 10, 25, and 50 wt % Al2O3 has been synthesized by direct precipitation. The as-prepared composites and those calcined in air at 1000 and 1100 C have been characterized by BET, X-ray diffraction, transmission electron microscopy, and temperature-programmed reduction methods. The composites aged at 1050 C in a 2% O2 + 10% H2O + 88% N2 atmosphere have been used to prepare monolith catalysts, and the oxygen storage capacity (OSC) of the latter has been measured using a gas analysis setup. As the proportion of Al2O 3 in the composite is raised, the mixing uniformity and degree of dispersion of Ce x Zr1-x O2-δ particles increase, their chemical composition becomes homogeneous, and the amount of cerium involved in oxidation and reduction increases. The composite containing 50 wt % Al2O3 is a mixture of Ce x Zr 1-x O2-δ and Al2O3 crystallites, whose size is practically unaffected by calcination. The (Pt/Al2O3 + Al2O3-Ce 0.75Zr0.25O2) based on this composite has the highest OSC and is the most active. For this reason, full-scale testing of this catalyst is recommended. © 2013 Pleiades Publishing, Ltd
Phased array based ultrasound scanning system development
© Published under licence by IOP Publishing Ltd. Multichannel ultrasound scanning system based on phased arrays development is presented in this paper. Substantiation of system parameters is presented. The description of block diagram and hardware development is presented. The combination of the self-developed receiving and a transmitting units and commercially available FPGA unit and Personal Computer can solve our scientific goals, while providing a relatively low device cost
Big-Bang Nucleosynthesis and Hadronic Decay of Long-Lived Massive Particles
We study the big-bang nucleosynthesis (BBN) with the long-lived exotic
particle, called X. If the lifetime of X is longer than \sim 0.1 sec, its decay
may cause non-thermal nuclear reactions during or after the BBN, altering the
predictions of the standard BBN scenario. We pay particular attention to its
hadronic decay modes and calculate the primordial abundances of the light
elements. Using the result, we derive constraints on the primordial abundance
of X. Compared to the previous studies, we have improved the following points
in our analysis: The JETSET 7.4 Monte Carlo event generator is used to
calculate the spectrum of hadrons produced by the decay of X; The evolution of
the hadronic shower is studied taking account of the details of the energy-loss
processes of the nuclei in the thermal bath; We have used the most recent
observational constraints on the primordial abundances of the light elements;
In order to estimate the uncertainties, we have performed the Monte Carlo
simulation which includes the experimental errors of the cross sections and
transfered energies. We will see that the non-thermal productions of D, He3,
He4 and Li6 provide stringent upper bounds on the primordial abundance of
late-decaying particle, in particular when the hadronic branching ratio of X is
sizable. We apply our results to the gravitino problem, and obtain upper bound
on the reheating temperature after inflation.Comment: 94 pages, 49 figures, to appear in Phys. Rev. D. This is a full
length paper of the preprint astro-ph/040249
(Tl, Au)/Si(111) and (Tl, Au)/Si(100) 2D compounds: Atomic and electronic structure and transport properties
Multipoint Schur algorithm and orthogonal rational functions: convergence properties, I
Classical Schur analysis is intimately connected to the theory of orthogonal
polynomials on the circle [Simon, 2005]. We investigate here the connection
between multipoint Schur analysis and orthogonal rational functions.
Specifically, we study the convergence of the Wall rational functions via the
development of a rational analogue to the Szeg\H o theory, in the case where
the interpolation points may accumulate on the unit circle. This leads us to
generalize results from [Khrushchev,2001], [Bultheel et al., 1999], and yields
asymptotics of a novel type.Comment: a preliminary version, 39 pages; some changes in the Introduction,
Section 5 (Szeg\H o type asymptotics) is extende
Extracellular electrical signals in a neuron-surface junction: model of heterogeneous membrane conductivity
Signals recorded from neurons with extracellular planar sensors have a wide
range of waveforms and amplitudes. This variety is a result of different
physical conditions affecting the ion currents through a cellular membrane. The
transmembrane currents are often considered by macroscopic membrane models as
essentially a homogeneous process. However, this assumption is doubtful, since
ions move through ion channels, which are scattered within the membrane.
Accounting for this fact, the present work proposes a theoretical model of
heterogeneous membrane conductivity. The model is based on the hypothesis that
both potential and charge are distributed inhomogeneously on the membrane
surface, concentrated near channel pores, as the direct consequence of the
inhomogeneous transmembrane current. A system of continuity equations having
non-stationary and quasi-stationary forms expresses this fact mathematically.
The present work performs mathematical analysis of the proposed equations,
following by the synthesis of the equivalent electric element of a
heterogeneous membrane current. This element is further used to construct a
model of the cell-surface electric junction in a form of the equivalent
electrical circuit. After that a study of how the heterogeneous membrane
conductivity affects parameters of the extracellular electrical signal is
performed. As the result it was found that variation of the passive
characteristics of the cell-surface junction, conductivity of the cleft and the
cleft height, could lead to different shapes of the extracellular signals
Single layer nickel disilicide on surface and as embedded layer
Single monolayers of various materials (e.g. graphene, silicene, bismuthene, plumbene, etc) have recently become fascinating and promising objects in modern condensed-matter physics and nanotechnology. However, growing a monolayer of non-layered material is still challenging. In the present report, it will be shown that single monolayer NiSi2 can be fabricated at Si(111) surface stabilized by either Tl, Pb or In monolayers. Nickel atoms were found to intercalate the stabilizing metal layers upon deposition and to reside in the interstitial sites inside the first silicon bilayer of bulk-like-terminated Si(111)1×1 surface. The interstitial positions almost coincide with the bulk NiSi2 atomic positions thus forming NiSi2 single layer. Atomic and electronic structure of formed systems is described in detail by means of a set of experimental techniques, including low-energy electron diffraction, scanning tunneling microscopy, angle-resolved photoemission spectroscopy and also first-principles density-functional-theory calculations. Quality of formed single monolayer NiSi2 was additionally confirmed by in situ four-probe transport measurements that show that single monolayer NiSi2 preserves a metallic-type conductivity down to 2.0 K. Moreover it was found that delta-type structure with atomic sheet of NiSi2 silicide embedded into a crystalline Si matrix can be fabricated using room-temperature overgrowth of a Si film onto the Tl stabilized NiSi2 surface layer. Confinement of the NiSi2 layer to a single atomic plane has been directly confirmed by high-resolution transmission electron microscopy
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Performance of the E715 Transition Radiation Detector
The transition radiation detector (TRD) consisted of 12 identical modules, each containing a radiator and a multiwire proportional counter (MWPC). A TRD is found to be an effective device for the identification of electrons in a large hadron background at Tevatron energies. The TRD proved to be a stable and reliable device with performance parameters in close agreement with theoretical predictions. The combination of a TRD with a lead glass calorimeter proved to be a very powerful method of electron identification. (LEW
Recrystallized graphite behavior as the first wall material in Globus-M spherical tokamak
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