We consider a smooth autonomous system in general form that admits a nondegenerate periodic solution. A global family (with respect to the parameter h) of nondegenerate periodic solutions is constructed, the law of monotonic variation of the period on the family is derived, and the existence of a reduced second-order system is proved. For it, the problem of stabilizing the oscillation of the controlled system, distinguished by the value of the parameter h, is solved. A smooth autonomous control is found, and an attracting cycle is constructed.

Three variants of the statistical complexity function, which is used as a criterion in the problem of detection of a useful signal in the signal-noise mixture, are considered. The probability distributions maximizing the considered variants of statistical complexity are obtained analytically and conclusions about the efficiency of using one or another variant for detection problem are made. The comparison of considered information characteristics is shown and analytical results are illustrated on an example of synthesized signals. A method is proposed for selecting the threshold of the information criterion, which can be used in decision rule for useful signal detection in the signal-noise mixture. The choice of the threshold depends a priori on the analytically obtained maximum values. As a result, the complexity based on the total variation demonstrates the best ability of useful signal detection.

Based on VKontakte data, we study the influence of various factors on the dynamics of opinions and actions both at the macro level (“public opinion”) and at the micro level (the opinions and actions of individual agents). Primary analysis results are presented for the dynamics of opinions and actions of agents in this social network. In particular, the growing polarization of opinions at the macro level is detected; changes in the opinions of agents over time are observed; socio-demographic characteristics of agents who changed their opinions are determined; a good consistency between the opinions and actions of agents is revealed; finally, an explicit relationship between the opinions and actions of agents is established.

The paper discusses the development of a platform for distributed energy resources management based on digital twins. The platform use cases include demand response, electric vehicle charging, peer-to-peer energy trading, storage scheduling, virtual power plant, and so on. Thanks to the digital twin, the platform can perform the use cases controlling either real operation-stage equipment or virtual design-stage simulation models. The platform offers mass distributed energy resources owners and operators to improve the power supply quality (including stability), reduce costs (including transaction overhead), and gain emerging market opportunities (including participation in various aggregators' programs). Software and equipment vendors are interested in the platform's capability to quickly assemble distributed energy management systems almost without programming. The digital twin and the platform are designed with the viewpoint-based approach established by the international systems engineering standard ISO/IEC/IEEE 42010. The typical power system digital twin architecture is described. The major kinds of mathematical models as part of digital twins are presented: physical models based on numerical solutions of differential equations and optimization problems, machine learning models, knowledge-based models. The interoperability of such heterogeneous models is ensured on the basis of the ontological model of distributed energy. The platform architecture is represented from three key viewpoints: functional, information, and software. To formalize and ultimately automate the integration of heterogeneous models, we propose novel mathematical methods of model-based system engineering based on category theory, including universal constructions and the multicomma. The multicomma category is shown to be constructed using standard product, exponent, and pushout constructions, which makes it possible to establish a number of its practically significant properties.