Simulation research of the strength of an engine mount in an aircraft piston diesel engine

The article presents strength simulations of a mount for mounting the test engine. Mounted on a stationary test stand, this mount consists of external fixings, fixings to stabilize the engine and tubular elements as a truss. These tubular elements are pipes made of seamless black steel. The material of the truss is S235JR steel. The article examines three different versions of the mount: mount no. 1 - initial mount, mount no. 2 - mount after a modification of pipe arrangement, mount no. 3 - mount after a modification of pipe wall thickness. For each version of the mount and subsequent calculation steps, the same boundary conditions and results legend were assumed. All calculations were made in Catia v5 in the Generative Structure Analysis module. To reflect the conditions prevailing during the engine operation on the test bench, the following conditions as mount load were adopted: gravity from the engine mass as 1000 N; engine thrust as 5000 N, and engine torque as 227 Nm. First, the model was pre-calculated to check the influence of mesh size on the obtained results. 2 mm parabolic tetrahedral elements were used in a computational grid. All subsequent steps of the mount modification showed a positive effect of reducing the maximum stress values or their mitigation as dispersion over a larger area. The changes made it possible to eliminate potentially dangerous areas of stress accumulation points. The material used has a strength several times greater than the stresses occurring in the tested elements. It was found that no further modifications to the mount are required and it is possible to use the created geometry on the test stand.

The modern state of the coenopopulations and the reproduction Asphodeline taurica (Pall.) Endl. in south-western part of the Crimea

The article presents the results of study some features of the development of Asphodeline taurica (Pall. ex Bieb.) Endl. in the south-western part of the Crimean peninsula. The age structure, density per m² and the type of coenopopulations of the species in various ecology-phytocenotic conditions have been described. It is shown that generative structure formation processes are mostly similar to other species of the genus Asphodeline , and the viability and peculiarities of seed formation can ensure optimal reproduction of Asphodeline taurica. The main limiting factors of species conservation and reproduction are anthropogenic impact and hydrothermal conditions during critical periods of genesis of generative structures, as well as the presence of pollinating insects during the flowering period.

Reciprocity, hierarchy, and obligation in world politics: From Kula to Potlatch

The observation that agents and structures are co-constituted is now commonplace, yet scholars continue to struggle to incorporate this insight. Rationalists tend to overemphasize actors’ agency in the constitution of social order while constructivists tend to overstate the degree to which structures determine action. This article uses The Gift to rethink the agent–structure debate, arguing that the model of social relations Mauss outlines in this work sheds new light on basic concepts in international relations theory such as reciprocity, hierarchy, and obligation. Mauss’ social theory locates the generative structure of social order in diffuse exchange relations, what he terms gift exchange, and assumes that actors are both socially positioned within hierarchical relations of exchange and reflexive agents who are able to understand and strive to change those relations. In so doing, he avoids reducing social order to either deeply internalized social norms or instrumental interests, navigating between agents and structures to develop a more dynamic model of social relations. This model of social order permits a richer understanding of hierarchy in world politics that appreciates the experience of domination and the possibility of resistance. It also provides a distinct understanding of the nature of social obligation and the “compliance pull” of social norms, locating their force in the reflexive recognition by actors that they are dependent on shared social relations for meaningful social agency. This points toward an ethics of stewardship that opens up new perspectives on the duties that states and others owe to each other, a duty grounded in an acknowledgment of our mutual vulnerability as socially constituted agents.

Model checking with probabilistic tabled logic programming

We present a formulation of the problem of probabilistic model checking as one of query evaluation over probabilistic logic programs. To the best of our knowledge, our formulation is the first of its kind, and it covers a rich class of probabilistic models and probabilistic temporal logics. The inference algorithms of existing probabilistic logic-programming systems are well defined only for queries with a finite number of explanations. This restriction prohibits the encoding of probabilistic model checkers, where explanations correspond to executions of the system being model checked. To overcome this restriction, we propose a more general inference algorithm that uses finite generative structures (similar to automata) to represent families of explanations. The inference algorithm computes the probability of a possibly infinite set of explanations directly from the finite generative structure. We have implemented our inference algorithm in XSB Prolog, and use this implementation to encode probabilistic model checkers for a variety of temporal logics, including PCTL and GPL (which subsumes PCTL*). Our experiment results show that, despite the highly declarative nature of their encodings, the model checkers constructed in this manner are competitive with their native implementations.