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The effect of a compliant coating (film) over a porous surface on the stability of a supersonic (M = 2) boundary layer on a flat plate to disturbances of the first mode of instability under the conditions of experiments in the T-325 wind tunnel was calculated using linear stability theory. The calculations showed that a porous coating with a thin-film membrane on the surface can stabilize the boundary layer at Mach number M = 2 at the frequency most increasing on a solid plate. The dependences of the rates of the spatial growth of disturbances on a number of factors were found. Nonmonotonic (with minima) dependences of these growth rates on film tension, pore radius, porous coating depth, and porosity were obtained. The spatial growth rates of disturbances decrease with decreasing film thickness and the ratio of the gas pressure inside the pores to the static pressure in the boundary layer. It was found that stabilization of a supersonic (M = 2) boundary layer relative to the case of a smooth impermeable plate can occur only with a film thickness of less than 18 nm.

A multiblock numerical model was used to study the phenomenon of vacancy formation in a chain of dust particles. Self-consistent spatial distributions of the space charge and electric potential around the dust particles for two cases were obtained by means of numerical calculations: a linear chain of five particles and a chain of four particles with a vacancy. The equilibrium charges of particles and the magnitudes of the main forces acting on them (the ion drag force, the Coulomb force of particle repulsion, and the force exerted by an external electric field on charged particles) were calculated. It was shown that vacancy formation, without changing the structural parameters of the chain, occurs under conditions of strong ion trails, with the fourth and fifth particles in the strong ion trail of the second particle.

This paper describes a new phenomenon of generating a stable double precessing vortex in a highly swirling turbulent flow. It also identifies the range of flow conditions providing the clearest observation of this effect. It also identifies key features of the internal flow structure and the kinematic scheme of the double vortex precessional motion. The geometric parameters of the helical vortex are measured depending on the flow regime. The obtained results are important not only from a practical standpoint for the possibilities of controlling the flow structure in industrial apparatuses, but also from the standpoint of fundamental problems in vortex dynamics. Precession of a helical structure represents a canonical case of self-induced motion of a vortex filament with a helical axis of rotation.

This paper presents the analysis of linear stability of a swirling flow in a model combustion chamber. The flow is characterized by a strongly coherent component corresponding to vortex core precession. Using averaged data obtained via the large eddy simulation, a global stability analysis was performed taking into account turbulent viscosity. A mode with a dimensionless frequency of 0.76 was identified in the eigenvalue spectrum. The eigenfunction distributions indicate that this mode corresponds to a precessing vortex core (PVC). The study confirms that the PVC is a global unstable mode developing in a mean turbulent flow and will serve as a basis for further work on the development of PVC control strategies.

Thermal conductivity of solid magnesium-lithium alloys with X_Li = 35, 40, 50 at. % in the temperature range of 80 - 350 K was measured by a transient method using a plane heat source. The obtained results were compared with literature data for alloys of other compositions. For all the studied alloys, anomalous behavior in the form of a kink in the range of 310 - 330 K and a feature near 240 K, presumably associated with a martensitic transformation, was found on temperature dependences λ(T). Using literature data, concentration dependences of thermal conductivity of the Mg-Li system were plotted in the range X_Li = 0 - 50 at. %. It is shown that an increase in the lithium content in the range of 30 - 50 at. % leads to a further decrease in thermal conductivity.

The subject-matter of investigation is the nontrivial modal-logic problem of equivalence of de-dicto and de-re types of modalities. The target - explicating, exact formulating and adding the precisely formulated principle of equivalence of the modality-types as a new proper philosophy axiom scheme to the multimodal axiomatic system of formal philosophy Φ+∃. The scientific novelty : for realizing the target, the already published formal axiomatic theory Φ+∃ has been transformed into a qualitatively different logically formalized multimodal axiomatic system called Φ^DR due to manifest taking into an account and systematical dealing with the different modality types called de-dicto and de-re. For accomplishing the transformation, (1) definitions of the alphabets of artificial object-language and meta-language of Φ+∃ have been changed: new symbols Ω^D and Ω^R standing for perfection-modalities (belonging to the types D and R, respectively) have been included into the alphabet of metalanguage of Ф^DR; (2) in Φ^DR, one new axiom-scheme (containing the new symbols Ω^D and Ω^R) has been added to the set of axiom-schemes of Φ+∃; (3) by means of the artificial language of Φ^DR, a precise formulation of the principle of equivalence of the modality-types de-dicto and de-re is given, and the concrete epistemic condition, under which the equivalence principle is valid, is defined. For the first time, a nontrivial multimodal interpretation is given for the traditional formal logic square of opposition and hexagon. Also, for the first time, these geometric figures have been utilized for visual modeling a system of formal-axiological relations among qualitatively different de-re - perfection-modalities as evaluation-functions.

This paper examines the problem of semantics of intensional contexts from a special perspective related to the principles of operation of generative artificial intelligence (AI). Intensional contexts such as beliefs, desires, knowledge and convictions pose a particular challenge for modern language models, since they require taking into account the meanings of expressions in logical possible worlds or cognitive states of subjects. This paper is a kind of sketch for the formulation of a problem that has an engineering and philosophical dimension. Here, we analyze the mechanisms of operation of transformers that use contextual embeddings to model the meanings of words through self-attention. It was revealed that modern language models are able to effectively process anaphoric dependencies and contextual connections, but they face limitations when interpreting intensional constructions. Particular attention is paid to experiments with vector representations of objects in multidimensional space, during which difficulties arise when distinguishing between subjective beliefs and objective reality. The nature of the difficulties indicates that working with intensional contexts requires not only a simple analysis of probabilistic connections between words, but also a deeper understanding of the semantics of linguistic expressions.

We illustrate the functions of the concept of dispute in the formal theory of argumentation with the help of two well-known examples from the theory of argumentation: the example of Harry from Bermuda, used by S. Toulmin, and the example of Tweety the penguin, who does not fly, although it is a bird, used in non-monotonic logic. Reconstruction of these examples allows us to show the importance of the concept of dispute in the logic of argumentation for developing ways to solve the task of finding and selecting the strongest arguments with which the outcomes of argumentation between the parties can be identified. The solution of this task is a unification of the efforts of two leading areas of modern formal theory of argumentation - the argumentation logic and the dialectical theory of argumentation.

This article describes the language, semantics, and proof theory for firs t-order hybrid modal logic, which solves the problem of cross-world quantification.

The paper examines the logical representation of knowability in terms of the first-order hybrid epistemic logic proposed by C. Proietti. This logic contains alethic and epistemic modalities, and hybrid operators. Two drawbacks of Proietti’s formalization are shown and two modifications thereof are suggested.