This article addresses the issue of the cause-and-effect relationship between democracy and economic growth in Moldova from 1990 to 2020. This problem is one of the key topics of modern economic political science, but the results concerning the influence of the political system on economy are still ambiguous. No research has been conducted to date on this issue for Moldova. The econometric analysis was conducted using tree composite indexes of democracy, published by Freedom house, Polity V and V-Dem Varieties of Democracy. The causal impact between democracy indexes and per capita GDP growth is tested using Granger causality analysis. The results show that the choice of the democracy indicator and the time interval influences the modeling outcome. All three democracy indices depict different democratic trends at the country level. Although there is a positive causal link between the Polity index and GDP per capita in a short period, other results show no evidence that democratic reforms did contribute to economic growth in Moldova and vice versa. We conclude that democratization in conditions of weak law and political instability contributed to the emergency of a so-called hybrid democracy in Moldova.
Selecting gear materials is a great challenge for engineers. Gear teeth are subject to difficult and severe loading conditions. Simultaneous action of alternating normal and tangential dynamic stresses occurs, contact deformations accompanied by sliding friction. Gears are subject to increased requirements in terms of strength, geometric accuracy, dimensional stability, and durability. For the manufacture of gears, especially from thermoplastic materials, a theoretical argumentation of the materials is needed. An extensive study of thermoplastic materials, around the world needs to be done and the most efficient tribological couples to be chosen in terms of heat transfer from the gear zone, operation with or without lubrication, and gear life. In this paper, a theoretical synthesis of the Steel / Plastic, Plastic / Plastic, Plastic/Steel tribological couples is made, which were used in conformist and non-conformist experiments. Therefore, selected tribological couples are supposed to be used in the Precessional Transmissions applications.
The article examined the problem of the experimental setting of incidence angles for the generation of Lamb waves in plate-type parts by the non-contact ultrasonic control method. This type of control is mainly done by the use of two types of waves: Rayleigh, which detects invisible defects on the surface of parts, and Lamb waves mode A0 and S0. Mostly used is the mode A0 due to the propagation over distances of interest in the tested materials. One of the primary aim during the testing process is to position the ultrasonic transducers (transmitter and receiver) at oblique angles of incidence on a surface. The transducers should be positioned on an access face of the plate, as is common in industrial practice, at a fixed distance from the measured plate, and leaving an air gap between transducers and the tested plate. The ultrasonic transducers are moved simultaneously linearly or in zigzag on the surface of the plate-type part to measure the hidden defects (cracks, pores, inclusions) that appear in the composite materials during the manufacturing process or during the operation. The presented work brings new insights into the setting of the angle of incidence for generating lamb waves by non-contact method.
This paper deals with the theoretical-experimental model of the tribological behavior of the contact elements in precessional gears (PG) in the functions of conjugate profiles of linear velocities “convex-concave” or “convex-convex” for the corresponding geometric parameters (ρki, r, ρki – r) and the values of the kinematic force parameters (VE1, VE2, Vai) for each concrete position of the ki points. The calculation of the constructive-functional and kinematic parameters of the “roller-shoe” and “roller-roller” elements of the tribocouple were adjusted for the experimental verification tests on the SMT-1 installation and adapted to the specific test conditions of the tribocouples with conformal contact of gear teeth made of plastics, which will be subjected to sliding friction and rolling processes of the concrete tribocouple elements.
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