Modern methods for studying polymer complexes in aqueous and organic solutions

This review summarizes published data concerning modern physicochemical methods used to study complexation processes of polymers in solutions. Some of them—dynamic light scattering, nanoparticle tracking analysis, transmission electron microscopy, cryotransmission electron microscopy, atomic force microscopy, small-angle neutron scattering, analytical-velocity sedimentation, and luminescence methods—make it possible to gain insight into the structure of polymer complexes, while the other methods, such as isothermal titration calorimetry and surface plasmon resonance, provide an opportunity to assess the intensity of specific interactions between complex components

Internet Engineering Task Force (IETF)

Abstract This document considers a VPN end user establishing an IPsec Security Association (SA) with a Security Gateway using the Internet Key Exchange Protocol version 2 (IKEv2), where at least one of the peers has multiple interfaces or where Security Gateway is a cluster with each node having its own IP address

ОСОБЕННОСТИ ИССЛЕДОВАНИЙ АЭРОУПРУГИХ КОЛЕБАНИЙ БЕСПИЛОТНЫХ ЛЕТАТЕЛЬНЫХ АППАРАТОВ С ЭЛЕКТРОПРИВОДОМ РУЛЕЙ

Designing a modern flight vehicle is associated with the need to solve many scientific and technical problems. These tasks include the prevention of insecure self-oscillations in flight, taking into account the elasticity of the structure. These problems relate to dynamic aeroelasticity, a science that examines the interaction of an elastic structure (at its oscillation) with an air flow. Maneuverable unmanned aerial vehicles (UAVs) are considered. Since UAVs are essentially not used without an automatic control system (ACS), its presence must be taken into account when considering the vibrations of an elastic structure in flight. The influence of the elasticity of UAV design on the operation of ACS in flight is manifested in the possibility of self-oscillations in the loop "elastic UAV – ACS". Self-oscillations lead to disruption of normal operation of the onboard equipment or its failure. The complexity of the problem requires its consideration at almost all stages of UAV’s development, including the creation of a prototype and testing. The computational and experimental studies of the characteristics of elastic oscillations in the UAV flight of the cross-shaped scheme are considered. The features of these UAVs (options with a modular design, the nonlinearity of the airframe, rudders, ACS, and others) due to a significant amount of testing that is the basis for the calculations. Electric actuators have a small continuous operation time, and resource use, there are gearboxes with a large gear ratio and backlashes. This determines the dependence of the rotation rigidity of the rudders on the amplitude and frequency, as well as a significant increase in the total moments of inertia. The technique of bench experiment with obtaining data to assess the boundaries of the flutter and the boundaries of the stability of the loop "elastic UAV – ACS" is given. The questions of improvement of the stabilization system of UAV required for the study of its stability at frequencies of elastic oscillations are considered, as well as the evaluation of the limiting cycles of self-oscillations is given.Проектирование современного летательного аппарата (ЛА) связано с необходимостью решения многих научнотехнических задач. В их число входит предотвращение опасных автоколебаний в полете с учетом упругости конструкции. Эти задачи относятся к динамической аэроупругости, науке, в которой исследуется взаимодействие упругой конструкции (при ее колебаниях) с потоком воздуха. Рассматриваются маневренные беспилотные летательные аппараты (БЛА), которые принципиально не допускают применения без системы автоматического управления (САУ), поэтому ее наличие необходимо учитывать при исследовании колебаний упругой конструкции в полете. Влияние упругости конструкции БЛА на работу САУ в полете проявляется в возможности возникновения автоколебаний в контуре «упругий ЛА – САУ». Автоколебания приводят к нарушению нормальной работы бортовой аппаратуры или выходу ее из строя. Сложность данной задачи требует ее рассмотрения практически на всех этапах разработки БЛА, включая создание опытного образца и начало летных испытаний. Представлены расчетно-экспериментальные исследования характеристик упругих колебаний в полете БЛА крестообразной схемы. Особенностями исследуемых БЛА (варианты модульной конструкции, нелинейности корпуса, рулей, САУ и другие) обусловлен значительный объем испытаний, являющихся основанием для расчетов. Электроприводы рулей имеют малое время непрерывной работы и низкий ресурс, в них входят редукторы с большим передаточным отношением и люфтами. С этим связана зависимость жесткости рулей на вращение от амплитуды и частоты, а также существенное увеличение суммарных моментов инерции. Приведена методика стендового эксперимента с получением данных для оценки границ флаттера и границ устойчивости контура «упругий ЛА – САУ». Рассмотрены вопросы доработки контура стабилизации БЛА, необходимой для его устойчивости на частотах упругих колебаний, а также дана оценка предельных циклов автоколебаний

Protecting Internet Key Exchange Protocol Version 2 (IKEv2) Implementations from Distributed Denial-of-Service Attacks

Abstract This document recommends implementation and configuration best practices for Internet Key Exchange Protocol version 2 (IKEv2) Responders, to allow them to resist Denial-of-Service and Distribute

RESEARCH FEATURES OF AEROELASTIC OSCILLATIONS OF UNMANNED AERIAL VEHICLES WITH ELECTRIC ACTUATOR OF RUDDERS

Designing a modern flight vehicle is associated with the need to solve many scientific and technical problems. These tasks include the prevention of insecure self-oscillations in flight, taking into account the elasticity of the structure. These problems relate to dynamic aeroelasticity, a science that examines the interaction of an elastic structure (at its oscillation) with an air flow. Maneuverable unmanned aerial vehicles (UAVs) are considered. Since UAVs are essentially not used without an automatic control system (ACS), its presence must be taken into account when considering the vibrations of an elastic structure in flight. The influence of the elasticity of UAV design on the operation of ACS in flight is manifested in the possibility of self-oscillations in the loop "elastic UAV – ACS". Self-oscillations lead to disruption of normal operation of the onboard equipment or its failure. The complexity of the problem requires its consideration at almost all stages of UAV’s development, including the creation of a prototype and testing. The computational and experimental studies of the characteristics of elastic oscillations in the UAV flight of the cross-shaped scheme are considered. The features of these UAVs (options with a modular design, the nonlinearity of the airframe, rudders, ACS, and others) due to a significant amount of testing that is the basis for the calculations. Electric actuators have a small continuous operation time, and resource use, there are gearboxes with a large gear ratio and backlashes. This determines the dependence of the rotation rigidity of the rudders on the amplitude and frequency, as well as a significant increase in the total moments of inertia. The technique of bench experiment with obtaining data to assess the boundaries of the flutter and the boundaries of the stability of the loop "elastic UAV – ACS" is given. The questions of improvement of the stabilization system of UAV required for the study of its stability at frequencies of elastic oscillations are considered, as well as the evaluation of the limiting cycles of self-oscillations is given