On zero-divisors in group rings of groups with torsion

Nontrivial pairs of zero-divisors in group rings are introduced and discussed. A problem on the existence of nontrivial pairs of zero-divisors in group rings of free Burnside groups of odd exponent $n \gg 1$ is solved in the affirmative. Nontrivial pairs of zero-divisors are also found in group rings of free products of groups with torsion.Comment: 8 pages, to appear in Canadian Math. Bul

Employing per-component time step in DSMC simulations of disparate mass and cross-section gas mixtures

A new approach to simulation of stationary flows by Direct Simulation Monte Carlo method is proposed. The idea is to specify an individual time step for each component of a gas mixture. The approach consists of modifications mainly to collision phase and recommendation on choosing time step ratios. It allows softening the demands on the computational resources for cases of disparate collision diameters of molecules and/or disparate molecular masses. These are the cases important in vacuum deposition technologies. Few tests of the new approach are made. Finally, the usage of new approach is demonstrated on a problem of silver nanocluster diffusion in carrier gas argon in conditions of silver deposition experiments.Comment: The goal of submission is to find native English speaker willing to help me polish the paper. This is paper draft sent to Communications in Computational Physics. It is recommended to publication. The need of polishing was one of editors decision. See Additional data for MS Word source fil

Модельна оцінка взаємодії банківського і страхового сегментів фінансового ринку

Purpose: To develop a model of interaction between banks and insurance companies, allowing for a joint model assessment from the point of view of the possibility of sustainable operation and development. Findings: The article develops the theory of dynamic systems and a numerical method for solving the problem of assessing the results of interaction between banks and insurance companies based on a system of differential equations. The additive and multiplicative types of interaction are considered. The results of interaction are analyzed for various variants of the influence of the activities of the studied subjects. Practical Implications: The proposed approach is applicable to assess the effectiveness of the used model of interaction between banks and insurance companies. Originality/Value: The author's model of interaction between banks and insurance companies is original. The model has no analogues in the scientific literature of the studied subject area. Research Limitations/Future Research: The study proposes a generalized dynamic model of interaction without specifying the content of variables and the procedure for determining the input parameters. Its description and application determine potential areas for further research. Paper type: Theoretical.Цель работы: Разработать модель взаимодействия между банками и страховыми компаниями, позволяющую проводить совместную оценку с точки зрения возможности устойчивого функционирования и развития. Результаты исследования: В статье развивается теория динамических систем и на основе системы дифференциальных уравнений разработана методика решения проблемы оценки результатов взаимодействия банков и страховых компаний. Рассмотрены аддитивный и мультипликативный типы взаимодействия. Результаты взаимодействия анализируются при различных вариантах влияния деятельности исследуемых субъектов. Практическое значение исследования: Предложенный подход может быть использован для оценки эффективности используемой модели взаимодействия между банками и страховыми компаниями. Оригинальность / ценность: Авторская модель взаимодействия банков и страховых компаний оригинальна. Модель не имеет аналогов в научной литературе исследуемой предметной области. Ограничения исследований / Перспективы дальнейших исследований: Исследование предлагает обобщенную динамическую модель взаимодействия без указания содержания переменных и процедуры определения входных параметров. Его описание и применение определяют потенциальные направления дальнейших исследований. Тип статьи: Теоретический.Мета роботи: Розробити модель взаємодії між банками та страховими компаніями, що дозволяє проводити спільну оцінку з точки зору можливості стійкого функціонування та розвитку. Результати дослідження: У статті розвинено теорію динамічних систем та на основі системи диференціальних рівнянь розроблено методику вирішення проблеми оцінки результатів взаємодії банків та страхових компаній. Розглянуто аддитивний та мультиплікативний типи взаємодії. Результати взаємодії аналізуються при різних варіантах впливу діяльності досліджуваних об’єктів. Практичне значення дослідження: Запропонований підхід може бути використаний для оцінки ефективності використаної моделі взаємодії між банками та страховими компаніями. Оригінальність / цінність дослідження: Авторська модель взаємодії банків та страхових компаній оригінальна. Модель не має аналогів у науковій літературі досліджуваної предметної області. Обмеження досліджень / Перспективи подальших досліджень: Дослідження пропонує узагальнену динамічну модель взаємодії без зазначення змісту змінних та процедури визначення вхідних параметрів. Його опис та застосування визначають потенційні напрямки подальших досліджень. Тип статті: Теоретичний

Spin-Hall nanooscillator based on an antiferromagnetic domain wall

We propose here a high-frequency spin-Hall nano-oscillator based on a simple magnetic texture, such as a domain wall, located in an antiferromagnet with easy-axis anisotropy type. We show that the spin current, polarized along the anisotropy axis, excites a conical precession of the N\'eel vector in such a domain wall, which allows obtaining a robust ac output signal, -- contrary to the planar precession in an uniform uniaxial antiferromagnet, where ac output is hard to achieve. The frequency of the auto-oscillations is easily tunable by the applied current up to the THz range, and the threshold current vanishes for pure uniaxial antiferromagnet. By micro-magnetic simulations, we demonstrate that the pinning of the domain wall is crucial for the oscillator design, which can be achieved in nano-constriction layout of the free layer.Comment: 7 pages, 5 figures. Brief explanation of the dynamics near the threshold is added at P.

Antiferromagnetic droplet soliton driven by spin current

We demonstrate that a spin current flowing through a nano-contact into a uniaxial antiferromagnet with first- and second-order anisotropy can excite a self-localized dynamic magnetic soliton, known as a spin-wave droplet in ferromagnets. The droplet nucleates at a certain threshold current with the frequency of the N\'eel vector precession laying below the antiferromagnetic resonance. The frequency exhibits nonlinear behavior with the increasing of applied current. At the high value of applied torque, the soliton mode transforms, and the oscillator emits spin waves propagating in the antiferromagnetic layer.Comment: 6 pages, 5 figure

Agricultural Development Management in the Context of Ukraine's Foreign Economic Security

Purpose: Unsolved pre-war problems of agricultural production are additionally burdened by ongoing military operations, which have caused inevitable changes in domestic and foreign markets. Identifying and eliminating threats to the development of the agricultural sector will increase the efficiency of agricultural production, which will increase the level of foreign economic security of the country and, at the same time, strengthen global food security. Design / Method / Approach: Based on the data of domestic and international statistical services and organizations, we used economic and statistical methods (regression, trend analysis) and graphically presented the obtained results. Findings: A critically low share of imports negatively affects foreign economic security and pricing in the domestic market. The products export of plant-origin and low-value metals, as opposed to the high-tech products import, is critical. The condition with the provision of fish and fish products, fruits, berries and grapes, eggs, vegetables, and melon food crops is unstable. It depends either on conditions in foreign markets or only on domestic factors. The geographical structure of foreign trade is unsatisfactory and threatening due to excessive imports from China. An inverse correlation between the export volume of Ukrainian agricultural products and the world level of food prices has been established. Theoretical Implications: The work confirms the importance of the Ukrainian agricultural sector in the context of global food security. Practical Implications: We offer a set of actions, the implementation of which will make it possible to eliminate problems in agricultural production that negatively affect the state of foreign economic security. Originality / Value: Work on a highly specialized topic, which includes the development of agricultural processes against the background of ongoing military operations. Research Limitations / Future Research: In further research, it is advisable to consider the importance of the agricultural sector in the system of economic security of different countries since this article is limited to the methodology of the Ukrainian government. Paper type: Empirical JEL Classification: Q11, Q17, Q1

The Modified Two-Factor Model of the Profitable Behavior of Households

The main aim of the publication is clarifying of the influence of the motivational-stimulating factor of forming the profitable behavior of households for its detailizing, taking attention of the characteristic features of specific households by adjusting the form and parameters of dynamic models. A logarithmic form of the quantitative-qualitative evaluation of the motivational-stimulating factor is proposed, based on the economic interpretation of the psycho-physiological Weber-Fechner’s law. The built motivation function allows coordinating of endogenous and exogenous features by means of setting the level of satisfaction with incomes ensuring the minimum needs of the household. Comparison of its dynamics depending on the level of incomes with dynamics if function of motivation, which value is determined by a linear deviation between the full «satisfaction» with incomes and the actual in percents, displayed the existence of plots with ultra high motivation that correspond to lower than the minimum that should be regarded as a manifestation of formation of the economic behaviour in crisis. The built model is characterized by limited rationality and corresponds to the theory of institutionalism