High-frequency oscillations in low-dimensional conductors and semiconductor superlattices induced by current in stack direction

A narrow energy band of the electronic spectrum in some direction in low-dimensional crystals may lead to a negative differential conductance and N-shaped I-V curve that results in an instability of the uniform stationary state. A well-known stable solution for such a system is a state with electric field domain. We have found a uniform stable solution in the region of negative differential conductance. This solution describes uniform high-frequency voltage oscillations. Frequency of the oscillation is determined by antenna properties of the system. The results are applicable also to semiconductor superlattices.Comment: 8 pages, 3 figure

Щодо впливу напруженого стану на деформування конструкційних матеріалів

The question of the influence of the type of stress state (TSS) on the process of scleronomic and rheonomic deformation of structural materials under simple and close to simple loading conditions is considered. The parameters characterizing the TSS are indicated. This is a parameter (indicator) of the rigidity of the stress state, which reflects the influence of the first invariant of the stress tensor and is, with an accuracy of a constant factor, the ratio of the hydrostatic component of the stress tensor to its deviator component. The influence of the third invariant of stress tensors is taken into account by a number of parameters – the Nadai-Lode parameter, as well as the TSS angle in its various interpretations. A variant of taking this influence into account by introducing the governing equation of state of the function with the parameter of the TSS angle is shown. This function is determined based on analysis of basic tensile and torsion experiments. It is shown that taking into account VNS increases the accuracy of the calculation and improves the agreement between the calculation results and experiment. Pages of the article in the issue: 66 - 69 Language of the article: UkrainianРозглядається питання впливу виду напруженого стану (ВНС) на процес склерономного і реономного деформування конструкційних матеріалів при простих і близьких до простих режимах навантаження. Вказуються параметри, що характеризують ВНС. Це параметр (показник) жорсткості напруженого стану, що відбиває вплив першого інваріанта тензора напружень і являє собою з точністю до постійного множника відношення гідростатичного компонента тензора напружень до його девіаторної складової. Вплив третього інваріанта тензорів напружень враховується рядом параметрів – параметром Надаи-Лоде, а також кутом ВНС у його різних трактуваннях. Показано варіант врахування цього впливу шляхом введення в визначальні рівняння функції з параметром кута ВНС. Ця функція визначається на основі аналізу базових експериментів на розтяг і кручення. Показано, що врахування ВНС підвищує точність розрахунку і поліпшує узгодження результатів розрахунку з експериментом

On the nature of the solar-wind-Mars interaction

Plasma measurements near Mars on the U.S.S.R. Mars-2, -3, and -5 spacecraft are considered. The data are compared with simultaneous magnetic measurements. Strong evidence is obtained in favor of a direct interaction and mass exchange between the solar wind plasma and the gaseous envelope of Mars

Photoacoustic effect in micro- and nanostructures: numerical simulations of Lagrange equations

The  work  provides  the  description  of  theoretical  and  numerical  modeling  techniques of thermomechanical effects that take place in absorbing micro- and nanostructures of different materials under the action of pulsed laser radiation. A proposed technique of the numerical simulation is based on the solution of equations of motion of continuous media in the form of Lagrange for spatially inhomogeneous media. This model allows calculating fields of temperature, pressure, density, and velocity of the medium depending on the parameters of laser pulses and the characteristics of micro- and nanostructures.The  work  provides  the  description  of  theoretical  and  numerical  modeling  techniques of thermomechanical effects that take place in absorbing micro- and nanostructures of different materials under the action of pulsed laser radiation. A proposed technique of the numerical simulation is based on the solution of equations of motion of continuous media in the form of Lagrange for spatially inhomogeneous media. This model allows calculating fields of temperature, pressure, density, and velocity of the medium depending on the parameters of laser pulses and the characteristics of micro- and nanostructures

Метод анализа квазиоптимальных топологий сетей на кристалле

У статті розглянуто синтез топологій мереж на кристалі на основі методу еволюційних обчислень. Запропоновано критерії оптимальності топологій мереж на кристалі і новий клас квазіоптимальних топологій. Сформульовано вимоги до квазіоптимальних топологій. Розроблено генетичний алгоритм GeNoC для синтезу квазіоптимальних топологій мереж на кристалі з кількістю вузлів до 100. За допомогою математичних методів оптимізації виконано аналіз отриманих квазіоптимальних топологій. Запропоновано метод корекції коефіцієнтів значущості параметрів цільової функції при синтезі квазіоптимальних топологій, що дозволило зменшити різницю в їхніх характеристиках порівняно з теоретично можливими оптимальними топологіями до 1,8%.The article concentrates upon the synthesis of network-on-chip topologies, based on the evolutionary computations method. The optimality criteria of the network-on-chip topologies and a new class of quasi-optimal topologies are proposed. The requirements for quasi-optimal topologies are defined. The genetic algorithm GeNoC for the synthesis of quasi-optimal network-on-chip topologies with the number of nodes up to 100 is developed. By using the mathematical methods of optimization the analysis of the obtained quasi-optimal topologies is performed. The importance coefficients correction method of the objective function in the synthesis of quasi-topologies is proposed; as a result, the difference in their performance compared to theoretically possible optimal topologies is reduced up to 1,8%.В статье рассматривается синтез топологий сетей на кристалле на основе метода эволюционных вычислений. Предложены критерии оптимальности топологий сетей на кристалле и новый класс квазиоптимальных топологий. Сформулированы требования к квазиоптимальным топологиям. Разработан генетический алгоритм GeNoC для синтеза квазиоптимальных топологий сетей на кристалле с количеством узлов до 100. С помощью математических методов оптимизации, выполнен анализ полученных квазиоптимальных топологий. Предложен метод коррекции коэффициентов значимости параметров целевой функции при синтезе квазиоптимальных топологий, что позволило уменьшить разницу в их характеристиках по сравнению с теоретически возможными оптимальными топологиями до 1,8%

Classification of networks-on-chip in the context of analysis of promising self-organizing routing algorithms

This paper contains a detailed analysis of the current state of the network-on-chip (NoC) research field, based on which the authors propose the new NoC classification that is more complete in comparison with previous ones. The state of the domain associated with wireless NoC is investigated, as the transition to these NoCs reduces latency. There is an assumption that routing algorithms from classical network theory may demonstrate high performance. So, in this article, the possibility of the usage of self-organizing algorithms in a wireless NoC is also provided. This approach has a lot of advantages described in the paper. The results of the research can be useful for developers and NoC manufacturers as specific recommendations, algorithms, programs, and models for the organization of the production and technological process.Comment: 10 p., 5 fig. Oral presentation on APSSE 2021 conferenc

Pseudorandom number generator influence on the genetic algorithm performance to minimize maritime cargo delivery route length

We consider a problem of minimizing the maritime cargo delivery route length to reduce the delivery cost. In our model, the cost is equivalent to the sum of tour lengths of feeders used for the delivery to cover the route. Formulated as a multiple traveling salesman problem, we solve it with a genetic algorithm. The algorithm performance is dramatically influenced by the stream of pseudorandom numbers used for randomly generating the starting population and accomplishing random mutations. As the number of ports increases from 10 to 80, the route length variation intensifies from 3.5% to 22.5% on average. However, we increase the route length minimization accuracy by re-running the algorithm to solve the same problem until closely the best solution is obtained. The number of reruns is about 3 to 6 for up to 20 ports. For more than 20 ports the required number of algorithm reruns abruptly increases from 28 reruns for 30 ports to about 51 reruns within the range of 40 to 80 ports

Control of ion density distribution by magnetic traps for plasma electrons

The effect of a magnetic field of two magnetic coils on the ion current density distribution in the setup for low-temperature plasma deposition is investigated. The substrate of 400 mm diameter is placed at a distance of 325 mm from the plasma duct exit, with the two magnetic coils mounted symmetrically under the substrate at a distance of 140 mm relative to the substrate centre. A planar probe is used to measure the ion current density distribution along the plasma flux cross-sections at distances of 150, 230, and 325 mm from the plasma duct exit. It is shown that the magnetic field strongly affects the ion current density distribution. Transparent plastic films are used to investigate qualitatively the ion density distribution profiles and the effect of the magnetic field. A theoretical model is developed to describe the interaction of the ion fluxes with the negative space charge regions associated with the magnetic trapping of the plasma electrons. Theoretical results are compared with the experimental measurements, and a reasonable agreement is demonstrated. © 2012 American Institute of Physics