511 research outputs found
Properties and efficiency of catalysts produced by an ION beam processing technology
Paper presents the test results and properties of catalysts produced by an ion implantation technique. New catalysts showed the same efficiency with much lower expense of noble metals as compared with the catalysts produce by an impregnation. Also shown, that the ion bombardment did not reduce the specific surface area of the catalyst.ΠΡΠΈΠ²Π΅Π΄Π΅Π½Ρ ΡΠ²ΠΎΠΉΡΡΠ²Π° ΠΈ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΡ ΠΈΡΠΏΡΡΠ°Π½ΠΈΠΉ ΠΊΠ°ΡΠ°Π»ΠΈΠ·Π°ΡΠΎΡΠΎΠ², ΠΏΠΎΠ»ΡΡΠ΅Π½Π½ΡΡ
ΠΏΡΡΠ΅ΠΌ ΠΈΠΎΠ½Π½ΠΎΠΉ ΠΈΠΌΠΏΠ»Π°Π½ΡΠ°ΡΠΈΠΈ. ΠΠΎ ΡΡΠ°Π²Π½Π΅Π½ΠΈΡ Ρ ΠΊΠ°ΡΠ°Π»ΠΈΠ·Π°ΡΠΎΡΠ°ΠΌΠΈ, ΠΏΠΎΠ»ΡΡΠ΅Π½Π½ΡΠΌΠΈ ΠΎΠ±ΡΡΠ½ΡΠΌΠΈ ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΡΠΌΠΈ, ΠΎΠΏΡΡΠ½ΡΠ΅ ΠΊΠ°ΡΠ°Π»ΠΈΠ·Π°ΡΠΎΡΡ ΠΏΠΎΠΊΠ°Π·ΡΠ²Π°ΡΡ ΡΠ΅ ΠΆΠ΅ Π·Π½Π°ΡΠ΅Π½ΠΈΡ ΠΊΠΎΡΡΡΠΈΡΠΈΠ΅Π½ΡΠ° Π½Π΅ΠΉΡΡΠ°Π»ΠΈΠ·Π°ΡΠΈΠΈ ΠΏΡΠΈ Π·Π½Π°ΡΠΈΡΠ΅Π»ΡΠ½ΠΎ ΠΌΠ΅Π½ΡΡΠ΅ΠΌ ΡΠΎΠ΄Π΅ΡΠΆΠ°Π½ΠΈΠΈ Π±Π»Π°Π³ΠΎΡΠΎΠ΄Π½ΡΡ
ΠΌΠ΅ΡΠ°Π»Π»ΠΎΠ². ΠΠΎΠΊΠ°Π·Π°Π½ΠΎ, ΡΡΠΎ ΠΈΠΎΠ½Π½Π°Ρ Π±ΠΎΠΌΠ±Π°ΡΠ΄ΠΈΡΠΎΠ²ΠΊΠ° Π½Π΅ ΡΠΌΠ΅Π½ΡΡΠ°Π΅Ρ ΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΡΡ ΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΡ Π½ΠΎΡΠΈΡΠ΅Π»Π΅ΠΉ
The minimal conformal O(N) vector sigma model at d=3
For the minimal O(N) sigma model, which is defined to be generated by the
O(N) scalar auxiliary field alone, all n-point functions, till order 1/N
included, can be expressed by elementary functions without logarithms.
Consequently, the conformal composite fields of m auxiliary fields possess at
the same order such dimensions, which are m times the dimension of the
auxiliary field plus the order of differentiation.Comment: 15 page
Direct evidence for a piezoelectriclike effect in coherently strained SiGe/Si heterostructures
A hybrid acoustic spectroscopy technique has been used to demonstrate the (reversible) conversion of high frequency electric fields into longitudinal acoustic waves within a modulation-doped pseudomorphic Si/Si0.88Ge0.12/Si heterostructure. This provides compelling evidence for the existence of a piezoelectriclike coupling within such structures
Synthesis and crystal structure of a new hexagonal perovskite 7H-Ba7Li1.75Mn3.5O15.75 with Mn4+/Mn5+ charge distribution.
Our work describes the synthesis and crystal structure of a new hexagonal perovskite 7H-Ba7Li1.75Mn3.5O15.75with Mn4+/Mn5+charge distribution.</p
The structure of Green functions in quantum field theory with a general state
In quantum field theory, the Green function is usually calculated as the
expectation value of the time-ordered product of fields over the vacuum. In
some cases, especially in degenerate systems, expectation values over general
states are required. The corresponding Green functions are essentially more
complex than in the vacuum, because they cannot be written in terms of standard
Feynman diagrams. Here, a method is proposed to determine the structure of
these Green functions and to derive nonperturbative equations for them. The
main idea is to transform the cumulants describing correlations into
interaction terms.Comment: 13 pages, 6 figure
Metal vapor lasers with increased reliability
Results of investigation and development of an excitation pulse generator with magnetic pulse compression by saturation chokes for pumping of active media of CuBr, Sr, and Ca vapor lasers are presented. A high-power IGBT transistor is used as a commutator. The generator can operate at excitation pulse repetition frequencies up to 20 kHz. The total average power for all laser lines of the CuBr laser pumped by this generator is ~6.0 W; it is ~1.3β1.7 W for the Sr and Ca lasers
Operator approach to analytical evaluation of Feynman diagrams
The operator approach to analytical evaluation of multi-loop Feynman diagrams
is proposed. We show that the known analytical methods of evaluation of
massless Feynman integrals, such as the integration by parts method and the
method of "uniqueness" (which is based on the star-triangle relation), can be
drastically simplified by using this operator approach. To demonstrate the
advantages of the operator method of analytical evaluation of multi-loop
Feynman diagrams, we calculate ladder diagrams for the massless theory
(analytical results for these diagrams are expressed in terms of multiple
polylogarithms). It is shown how operator formalism can be applied to
calculation of certain massive Feynman diagrams and investigation of Lipatov
integrable chain model.Comment: 16 pages. To appear in "Physics of Atomic Nuclei" (Proceedings of
SYMPHYS-XII, Yerevan, Armenia, July 03-08, 2006
Selfdual Spin 2 Theory in a 2+1 Dimensional Constant Curvature Space-Time
The Lagrangian constraint analysis of the selfdual massive spin 2 theory in a
2+1 dimensional flat space-time and its extension to a curved one, are
performed. Demanding consistence of degrees of freedom in the model with
gravitational interaction, gives rise to physical restrictions on non minimal
coupling terms and background. Finally, a constant curvature scenario is
explored, showing the existence of forbidden mass values. Causality in these
spaces is discussed. Aspects related with the construction of the reduced
action and the one-particle exchange amplitude, are noted.Comment: 20 pages, references added, little modifications performe
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