This paper studies multistability and hidden oscillations in a four-dimensional Keldysh model of flutter suppression. The model is written in the Lurie form and is considered with discontinuous damper characteristics interpreted in the sense of Filippov. We analyze the stationary set, the sliding manifold, and the corresponding reduced sliding dynamics. To detect undesired periodic solutions, we apply the locus of a perturbed relay system (LPRS) method and extend it to a discontinuous piecewise-linear approximation of the original Keldysh nonlinearity. It allows to reveal symmetric and asymmetric stable periodic solutions, including periodic solutions with complicated switching configurations. Numerical continuation from the discontinuous piecewise-linear characteristic to the original discontinuous characteristic with a quadratic term detects five stable periodic solutions, four of which are hidden with respect to the rest segment. These results show that the four-dimensional Keldysh model has rich and complex nonsmooth dynamics and provide a constructive framework for estimating the boundary of global stability in discontinuous aircraft control systems.
A simulation technique is described that was applied to optimise the design and ensure the desired field quality of a superconducting solenoid. A three-section solenoid with a lengthwise split winding was chosen as a reference configuration. The design was optimized through MathCAD calculations with the Levenberg-Marquardt minimization. The calculated data enabled adjustment of the coil geometry so as to provide required field homogeneity with respect to manufacture limitations. The optimised design was validated in comparative simulations and measurements on a prototype. The study was performed within the R&D activities on construction of an original electron beam ion source (EBIS). The results of the study were reported in the project documents.
This paper presents semantic inversion of pretrained image classifiers as an experimental probe of the view that late neural representations behave as class- dependent error-correcting codewords. The method reconstructs ImageNet validation images from late classifier activations by optimizing pixels to match one tail-proximal feature distribution under a symmetric Kullback–Leibler (Jeffreys) objective. The protocol is not a generative-prior attack and not a data-free synthesis method: it uses only the frozen classifier, a smoothed optimization path, a feature-mean constraint, a total-variation prior, and a class-logit KL constraint. The experiment evaluates 21 Torchvision models spanning RegNet, ResNet, EfficientNet, ConvNeXt, and ViT families on 48 class-capped high-margin validation samples per model. Reconstruction quality is measured objectively with OpenCLIP ViT-L/14 image-image retrieval metrics, feature-KL reduction in bits, and top-1 classification accuracy of the reconstructed images. The results show strong semantic recovery for ViT-B/16 and EfficientNet models, moderate recovery for RegNet models and ConvNeXt-Tiny, weak retrieval for the larger ResNet and ConvNeXt variants, and adversarial nonsemantic failures for ResNet18 and ResNet34. Qualitative reconstructions further illustrate that successful recoveries preserve class-level form and color without copying exact pixel-level appearance.
The paper develops a stochastic discrete-time framework for practical fixed-time consensus. Constructive estimates are obtained for the practical consensus set and for the expected entrance time into this set. A comparison-based argument is also established to relate the stochastic dynamics to an ideal noise-free model and to quantify their finite-horizon closeness.
This paper investigates a nonlocal control problem of a linear non-stationary dynamic system described by an ordinary differential equation subject to an integral constraint imposed on the components of the state vector over a certain subinterval of the system’s operating time. Conditions for complete controllability of the dynamic system under the imposed integral constraints are formulated. Conditions ensuring the existence of a solution to the control problem with such a nonlocal constraint are obtained. A constructive approach to solving the control problem is proposed, and the corresponding solution is constructed. The continuity and non-uniqueness of the control function are demonstrated. As an illustration, a control problem for the oscillatory motion of a material point with classical boundary conditions and an integral condition is solved.
