Design of Four-DoF Compliant Parallel Manipulators Considering Maximum Kinematic Decoupling for Fast Steering Mirrors

Laser beams can fluctuate in four directions, which requires active compensation by a fast steering mirror (FSM) motion system. This paper deals with the design of four-degrees-of-freedom (DoF) compliant parallel manipulators, for responding to the requirements of the FSM. In order to simplify high-precision control in parallel manipulators, maximum kinematic decoupling is always desired. A constraint map method is used to propose the four required DoF with the consideration of maximum kinematic decoupling. A specific compliant mechanism is presented based on the constraint map, and its kinematics is estimated analytically. Finite element analysis demonstrates the desired qualitative motion and provides some initial quantitative analysis. A normalization-based compliance matrix is finally derived to verify and demonstrate the mobility of the system clearly. In a case study, the results of normalization-based compliance matrix modelling show that the diagonal entries corresponding to the four DoF directions are about 10 times larger than those corresponding to the two-constraint directions, validating the desired mobility.

Universality of ultrasonic attenuation coefficient of amorphous systems at low temperatures

The competition between unretarded dispersion interactions between molecules prevailing at medium range order length scales and their phonon induced coupling at larger scales leads to appearance of nano-scale sub structures in amorphous systems. The complexity of intermolecular interactions gives rise to randomization of their operators. Based on a random matrix modelling of the Hamiltonian and its linear response to an external strain field, we show that the ultrasonic attenuation coefficient can be expressed as a ratio of two crucial length-scales related to molecular dynamics. A nearly constant value of the ratio for a wide range of materials then provides a theoretical explanation of the experimentally observed qualitative universality of the ultrasonic attenuation coefficient at low temperatures.

THE POEM "BEOWULF": NEW HORIZONTS OF STUDYING

[Karlova V. О. Cognitive-matrix Modelling of Borrowed Vocabulary in the Old English Poem "Beowulf" (Specialty 035 Philology. Kyiv, 2020. 303 p.)]

COMPARATIVE COMPATIBILITY

e article discusses the problem of comparative compatibility in Bulgarian, French and Turkish languages. The first two languages are Indo-European but from different groups (the Slavic and the Romance groups respectively), and the third is a non-Indo-European, representative of the Turkic language family. The objective of this study are the cognitive and pragmatic chains for expressing the impossibility of boarding a certain vehicle due to its delayed arrival at the place of departure, which are characteristic of the linguistic pictures of the three languages in question. The purpose of the study is to identify the elements used for building these cognitive and pragmatic chains in Bulgarian, French and Turkish languages by comparing them and exploring their potential for combinations in the languages mentioned. Samples of everyday speech acts from the three languages have been presented, described, juxtaposed, compared and analyzed from a morphosyntactic, lexical and pragmatic perspective. A combination of the comparative method and matrix modelling is used for processing the linguistic material and the results are presented in a tabular form. The conclusion not only reveals some linguistic differences, but suggests that they are due to the cultures of the three countries and their transport systems. A suggestion for further implementation of the results of the study is made, namely, elaborating bilingual and/or multilingual dictionaries.

Modelling and researching of forced spatial vibrations of axial fans

This work presents a mechanic - mathematical matrix modelling of the forced spatial vibrations of an axial fan. The axial fan is considered as a mechanical system consisting of three rigid bodies and with 18 degrees of freedom. The differential equations of the forced vibrations are derived. They take into account the mass, inertial, elastic, damping and geometric characteristics of this mechanical system. Algorithms are developed for computer calculating, analysis and synthesis of the design of this axial fan. These algorithms are a prerequisite for achieving the required operational properties of the fan and its compliance with the standards and regulations for vibrations’ impact on the human body. Calculations and results of the forced spatial vibrations are provided for specific parameters of the mechanical system.