68 Result(s)

Article

Steam Reforming of Isobutanol on Biochar-Supported Ni–Co Catalysts

The equilibrium parameters of steam isobutanol reforming were calculated. These include the H₂ yield, selectivity with respect to carbon-containing gases, and feed conversion. The calculated data, on the whole, a...

A. K. Osipov, M. V. Kulikova, A. E. Kuz’min… in Russian Journal of Applied Chemistry (2023)

Article

Temperature Dependence of the Electrical Resistivity of Electron-Doped Cuprates

Experimental data on the temperature dependence of electrical resistivity are analyzed for electron-doped Nd_2 – xCe_xCuO_4 – δ cuprates in a wide range of cerium concentrations 0.12 ≤ x ≤ 0.20. It is shown that, in...

N. A. Babushkina, A. A. Vladimirov… in Journal of Experimental and Theoretical Ph… (2020)

Article

Variational Principles for Self-Adjoint Hamiltonian Systems

A. A. Vladimirov in Mathematical Notes (2020)

Article

Oscillation Properties of a Multipoint Fourth-Order Boundary-Value Problem with Spectral Parameter in the Boundary Condition

A multipoint fourth-order boundary-value problem with spectral parameter in the boundary condition is considered. It is proved that its spectrum is simple and the system of derivative eigenfunctions has oscill...

A. A. Vladimirov, E. S. Karulina in Mathematical Notes (2019)

Article

Quasirenormalizable Quantum Field Theories

Leading logarithms in massless nonrenormalizable effective field theories can be computed using nonlinear recurrence relations. These recurrence relations follow from the fundamental requirements of unitarity,...

M. V. Polyakov, K. M. Semenov-Tian-Shansky… in Theoretical and Mathematical Physics (2019)

Article

Large Fluctuations in Two-Level Systems With Stimulated Emission

We consider a system of N identical independent Markov processes, each taking values 0 or 1. The system describes the stochastic dynamics of an ensemble of two-level atoms. The atoms are exposed to a photon flux....

E. A. Pechersky, S. A. Pirogov, G. M. Schütz… in Theoretical and Mathematical Physics (2019)

Article

Propagation of Chaos and Poisson Hypothesis

We establish the strong Poisson hypothesis for symmetric closed networks. In particular, we prove asymptotic independence of nodes as the size of the system tends to infinity.

A. A. Vladimirov, S. A. Pirogov, A. N. Rybko… in Problems of Information Transmission (2018)

Article

Optimization of vibrational cutting

The cutting speed and vibrational acceleration have the greatest influence on the tool life in turning. Promising directions for further improvement in tool life are identified by analysis of a mathematical mo...

A. P. Sergiev, A. A. Vladimirov, E. G. Shvachkin in Russian Engineering Research (2017)

Article

Representation theorems and variational principles for self-adjoint operator matrices

We use the notion of triples D⁺ → H → D⁻ of Hilbert spaces to develop an analog of the Friedrichs extension procedure for a class of nonsemibounded operator matrices. In addition, we suggest a general approach (s...

A. A. Vladimirov in Mathematical Notes (2017)

Article

On the problem of oscillation properties of positive differential operators with singular coefficients

A criterion for a highly singular positive fourth-order operator with separable boundary conditions to have oscillation properties, as well as sufficient conditions for similar higher-order operators to have o...

A. A. Vladimirov in Mathematical Notes (2016)

Article

Magnetic order and spin excitations in the Kitaev–Heisenberg model on a honeycomb lattice

We consider the quasi-two-dimensional pseudo-spin-1/2 Kitaev–Heisenberg model proposed for A₂IrO₃ (A = Li, Na) compounds. The spin-wave excitation spectrum, the sublattice magnetization, and the transition temper...

A. A. Vladimirov, D. Ihle, N. M. Plakida in Journal of Experimental and Theoretical Physics (2016)

Article

Remarks on minorants of Laplacians on a geometric graph

A. A. Vladimirov in Mathematical Notes (2015)

Article

A priori lower bound for the minimal eigenvalue of a Sturm-Liouville problem with boundary conditions of the second type

We establish the attainability of the infimum m _γ for the minimal eigenvalues of the boundary-value problems $ - y'' +...

A. A. Vladimirov, E. S. Karulina in Mathematical Notes (2015)

Article

Magnetic order and spin excitations in layered Heisenberg antiferromagnets with compass-model anisotropies

The spin-wave excitation spectrum, magnetization, and Néel temperature for the quasi-two-dimensional spin-1/2 antiferromagnetic Heisenberg model with the compass-model interaction in the plane proposed for iri...

A. A. Vladimirov, D. Ihle, N. M. Plakida in JETP Letters (2015)

Article

Investigation of the structure and dispersion of photoactive nanocrystal TiO₂ powders

Effect of the pH in the synthesis of ammonium titanate gel and the temperature of xerogel dehydration on the phase composition, degree of crystallinity, and dispersion of photoactive TiO₂ powders is investigated....

D. V. Dyagilev, T. A. Larichev, V. M. Pugachev… in Journal of Structural Chemistry (2014)

Article

Neurophysiological Markers of Stress within a Recovery Period after Acute Complications of Cardiovascular Diseases

In the course of rehabilitation in a sanatorium, we provided polygraphic examination of a group of 14 men who endured myocardial infarction or stroke one to three months ago. Fourteen men of a comparable age (...

A. A. Vladimirov, Yu. I. Andriyashek in Neurophysiology (2014)