New Class Of Systems Research Articles

ON A BOUNDARY VALUE PROBLEM WITH INTEGRAL CONDITIONS FOR A SYSTEM OF DIFFERENTIAL EQUATIONS WITH MANY TRANSFORMED ARGUMENTS

A.M. Samoilenko's numerical-analytic method is well-known and effective research method of solvability and approximate construction of the solutions of various boundary value problems for systems of differential equations. The investigation of boundary value problems for new classes of systems of functional-differential equations by this method is still an actual problem. A boundary value problem for a system of differential equations with finite quantity of transformed arguments in the case of integral boundary conditions is considered at this paper. To investigate the existence and approximate construction of the solution of such boundary value problem it is proposed a traditional scheme of the numerical-analytic method with a determining equation, as well as a modified scheme without a determining equation. In the case of a traditional scheme it is constructed a recurrent sequence of functions that depend on parameter, each of which satisfies given boundary conditions. It is shown that under typical for numerical-analytic method assumptions, this sequence uniformly convergences to the limit function. It is established the value of the parameter at which the limit function will be an exact solution of the original boundary value problem. Approximate determining function and approximate determining equation put into consideration, and on the basis of them sufficient conditions for the solvability of this boundary value problem are obtained. The necessary conditions for the solvability of the considered boundary value problem and an estimation of the deviation of the approximate solution from the exact solution were also obtained. In the case of the modified scheme it is constructed a recurrent sequence of functions, each of which satisfies the specified boundary conditions. Under the typical for the numerical-analytic method assumptions, the uniform convergence of this sequence to the limit function, which is the exact solution of the considered boundary value problem, is proved. It is established the uniqueness of this solution and it is obtained an estimation of the deviation of the approximate solution from the exact solution. The proposed modified scheme of the numerical-analytic method is illustrated by concrete examples.

Global Feedback Regulation for a Class of Uncertain Nonlinear Systems via Integral Control: A Gain Control Technique

This paper studies the global feedback regulation problems for triangular nonlinear systems perturbed by matched disturbances and modeling uncertainties with unknown system parameters. Instead of constructing extended state observers, new integral controllers composed of an integral dynamic are constructed to make all states of the uncertain systems bounded and asymptotically converge to zero. Firstly, an integral dynamic is constructed and a new state transformation is introduced, which transforms the triangular nonlinear systems into a class of auxiliary intermediate systems. Secondly, by using the time-varying gain technique, designing regulating controllers for the auxiliary intermediate systems is converted into designing a dynamic parameter for a class of new systems. Thirdly, with the help of the Lyapunov stability theorem and the characteristics of designed dynamic parameter, it is provided that the boundness of the new systems yields the regulation of the auxiliary intermediate systems, which further indicates the global feedback regulation of the considered systems. Two physical system examples are given to demonstrate the effectiveness of the proposed controllers.

Check Out the Big Brain on BRAD: Simplifying Cloud Data Processing with Learned Automated Data Meshes

The last decade of database research has led to the prevalence of specialized systems for different workloads. Consequently, organizations often rely on a combination of specialized systems, organized in a Data Mesh. Data meshes present significant challenges for system administrators, including picking the right system for each workload, moving data between systems, maintaining consistency, and correctly configuring each system. Many non-expert end users (e.g., data analysts or app developers) either cannot solve their business problems, or suffer from sub-optimal performance or cost due to this complexity. We envision BRAD, a cloud system that automatically integrates and manages data and systems into an instance-optimized data mesh, allowing users to efficiently store and query data under a unified data model (i.e., relational tables) without knowledge of underlying system details. With machine learning, BRAD automatically deduces the strengths and weaknesses of each engine through a combination of offline training and online probing. Then, BRAD uses these insights to route queries to the most suitable (combination of) system(s) for efficient execution. Furthermore, BRAD automates configuration tuning, resource scaling, and data migration across component systems, and makes recommendations for more impactful decisions, such as adding or removing systems. As such, BRAD exemplifies a new class of systems that utilize machine learning and the cloud to make complex data processing more accessible to end users, raising numerous new problems in database systems, machine learning, and the cloud.

Fermiology of Chiral Cadmium Diarsenide CdAs2, a Candidate for Hosting Kramers-Weyl Fermions.

Nonmagnetic chiral crystals are a new class of systems hosting Kramers-Weyl Fermions, arising from the combination of structural chirality, spin-orbit coupling (SOC), and time-reversal symmetry. These materials exhibit nontrivial Fermi surfaces with SOC-induced Chern gaps over a wide energy range, leading to exotic transport and optical properties. In this study, we investigate the electronic structure and transport properties of CdAs2, a newly reported chiral material. We use synchrotron-based angle-resolved photoelectron spectroscopy (ARPES) and density functional theory (DFT) to determine the Fermiology of the (110)-terminated CdAs2 crystal. Our results, together with complementary magnetotransport measurements, suggest that CdAs2 is a promising candidate for novel topological properties protected by the structural chirality of the system. Our work sheds light on the details of the Fermi surface and topology for this chiral quantum material, providing useful information for engineering novel spintronic and optical devices based on quantized chiral charges, negative longitudinal magnetoresistance, and nontrivial Chern numbers.

Stably protected gapless edge states without Wannier obstruction

Bulk-boundary correspondence serves as an important feature of topological insulators, including Chern insulators and ${\mathbb{Z}}_{2}$ topological insulators. These topological insulators have spectral flow in the Wilson-loop spectrum, and they encounter Wannier obstruction. Recent studies show that the bulk topological features may not imply the existence of protected gapless boundary states. Here we address the opposite question: Does the existence of stably protected gapless edge states necessarily imply Wannier obstruction or Wilson-loop winding? We provide an example in which stably protected gapless edge states arise without the aforementioned bulk topological features. This trivialized topological insulator belongs to a new class of systems with non-$\ensuremath{\delta}$-like Wannier functions. Interestingly, the gapless edge states are not protected by crystalline symmetry; instead, the protection originates from mirror antisymmetry, a combination of chiral and mirror symmetries. Although the protected gapless edge states cannot be captured by bulk topological features, they can be characterized by the spectral flow in the entanglement spectrum.

Reduce-Order Modeling and Higher Order Numerical Solutions for Unsteady Flow and Heat Transfer in Boundary Layer with Internal Heating

We obtain similarity transformations to reduce a system of partial differential equations representing the unsteady fluid flow and heat transfer in a boundary layer with heat generation/absorption using Lie symmetry algebra. There exist seven Lie symmetries for this system of differential equations having three independent and three dependent variables. We use these Lie symmetries for the reduced-order modeling of the flow equations by constructing invariants corresponding to linear combinations of these Lie point symmetries. This procedure reduces one independent variable of the concerned fluid flow model when applied once. Double reductions are achieved by employing invariants twice that lead to ordinary differential equations with one independent and two dependent variables. Similarity transformations are constructed using these two sets of derived invariants corresponding to linear combinations of the Lie point symmetries. These similarity transformations have not been obtained earlier for this flow model. Moreover, the corresponding reduced systems of ordinary differential equations are different from those which exist in the literature for fluid flow and heat transfer that we have been dealing with. We obtain multiple similarity transformations which lead us to new classes of systems of ordinary differential equations. Accurate numerical solutions of these systems are obtained using the combination of an adaptive fourth-order Runge–Kutta method and shooting procedure. Effects of variation of unsteadiness parameter, Prandtl number and heat generation/absorption on fluid velocity, skin friction, surface temperature and heat flux are studied and presented with the help of tables and figures.

Field Trial of a Coherent, Widely Distributed, Dual-Band Photonics-Based MIMO Radar With ISAR Imaging Capabilities

Soon after its introduction in the communications domain, the novel concept of multiple input–multiple output (MIMO) has been making its way also into the radar world. A new generation of multistatic netted systems with unprecedented capabilities has been fully theorised, unveiling its potential advantages over its classical stand-alone, monostatic counterparts. However, MIMO radars mainly remained the object of abstract modeling, since electronic technology could hardly support the practical implementation of this new class of systems. With the development of microwave photonics, the realization of MIMO radar networks at the best of their capabilities has become a reality, thanks to the inherent coherence of photonics systems, and to the broad-band, low-distortion, and interference-immune optical signal distribution. This paper presents the results of a microwave photonics widely-distributed, dual-band MIMO radar network, deployed in a real freight port for maritime traffic monitoring, with inverse synthetic aperture radar imaging capabilities. It employs a central unit connected to multiple widely distributed remote radar peripherals thanks to optical fiber. The possibility to operate in dual-band mode, and the coherent management of the transmitted and received signals are demonstrated, exploiting geometric and frequency diversity in target detection. The system exhibits a spurious-free dynamic range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{\sim 82}\,{\mathbf{d}\mathbf{B}\cdot \mathbf{\mathbf{Hz}}^{\mathbf{2/3}}}$</tex-math></inline-formula> and a sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf{-110}\,\mathbf{dBm}$</tex-math></inline-formula> . Under these premises, a small boat of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf \sim\! 1\,{\mathrm{\mathrm{m}}^{\mathrm{2}}}$</tex-math></inline-formula> radar cross section has been detected at more than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf {800}\,{\mathbf{m}}$</tex-math></inline-formula> , achieving a probability of detection of about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf {0.85}$</tex-math></inline-formula> , for a false alarm rate of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf {7.7\times 10^{-4}}$</tex-math></inline-formula> .

Statics and dynamics of skyrmions interacting with disorder and nanostructures

Magnetic skyrmions are topologically stable nanoscale particle-like objects that were discovered in 2009. Since that time, intense research interest has led to the identification of numerous compounds that support skyrmions over a range of conditions spanning cryogenic to room temperatures. Skyrmions can be set into motion under various types of driving, and the combination of their size, stability, and dynamics makes them ideal candidates for numerous applications. Skyrmions represent a new class of system in which the energy scales of the skyrmion-skyrmion interactions, sample disorder, temperature, and drive can compete. A growing body of work indicates that the static and dynamic states of skyrmions can be influenced strongly by pinning or disorder in the sample; thus, an understanding of such effects is essential for the eventual use of skyrmions in applications. In this article we review the current state of knowledge regarding individual skyrmions and skyrmion assemblies interacting with quenched disorder or pinning. We outline the microscopic mechanisms for skyrmion pinning, including the repulsive and attractive interactions that can arise from impurities, grain boundaries, or nanostructures. This is followed by descriptions of depinning phenomena, sliding states over disorder, the effect of pinning on the skyrmion Hall angle, the competition between thermal and pinning effects, the control of skyrmion motion using ordered potential landscapes such as one- or two-dimensional periodic asymmetric substrates, the creation of skyrmion diodes, and skyrmion ratchet effects. We highlight the distinctions arising from internal modes and the strong gyroscopic or Magnus forces that cause the dynamical states of skyrmions to differ from those of other systems with pinning. We also discuss future directions and open questions related to the pinning and dynamics in skyrmion systems.

Majorana bound states induced by antiferromagnetic skyrmion textures

Majorana bound states are zero-energy states predicted to emerge in topological superconductors and intense efforts seeking definitive proof of their observation are still ongoing. A standard route to realize them involves antagonistic orders: a superconductor in proximity to a ferromagnet. Here, we show that this issue can be resolved using antiferromagnetic rather than ferromagnetic order. We propose to use a chain of antiferromagnetic skyrmions, in an otherwise collinear antiferromagnet, coupled to a bulk conventional superconductor as a novel platform capable of supporting Majorana bound states that are robust against disorder. Crucially, the collinear antiferromagnetic region neither suppresses superconductivity nor induces topological superconductivity, thus allowing for Majorana bound states localized at the ends of the chain. Our model introduces a new class of systems where topological superconductivity can be induced by editing antiferromagnetic textures rather than locally tuning material parameters, opening avenues for the conclusive observation of Majorana bound states.

Mechanical Properties of Nanoporous Metallic Ultrathin Films: A Paradigmatic Case.

Nanoporous ultrathin films, constituted by a slab less than 100 nm thick and a certain void volume fraction provided by nanopores, are emerging as a new class of systems with a wide range of possible applications, including electrochemistry, energy storage, gas sensing and supercapacitors. The film porosity and morphology strongly affect nanoporous films mechanical properties, the knowledge of which is fundamental for designing films for specific applications. To unveil the relationships among the morphology, structure and mechanical response, a comprehensive and non-destructive investigation of a model system was sought. In this review, we examined the paradigmatic case of a nanoporous, granular, metallic ultrathin film with comprehensive bottom-up and top-down approaches, both experimentals and theoreticals. The granular film was made of Ag nanoparticles deposited by gas-phase synthesis, thus providing a solvent-free and ultrapure nanoporous system at room temperature. The results, bearing generality beyond the specific model system, are discussed for several applications specific to the morphological and mechanical properties of the investigated films, including bendable electronics, membrane separation and nanofluidic sensing.

On ways to increase protection of special structures from impact action

The technique of research of dynamic processes of elements of engineering constructions of special purpose from explosive action of projectiles is developed. Elastically reinforced beams with hinged ends were chosen for the physical model of elements of engineering structures. It is assumed that the elastic properties of the latter satisfy the nonlinear technical law of elasticity. A mathematical model of the process of a series of impact actions of projectiles at different points of the element of the protective structure is constructed. The latter is a boundary value problem for a partial differential equation. Its peculiarity is that the external dynamic action is a discrete function of linear and time variables. To determine the dynamic effect of a series of impacts on the object under study, and thus the level of protection of the structure, the basic ideas of perturbation theory methods are extended to new classes of systems. This allowed to obtain an analytical dependence of the deformation of the elastically reinforced element on the basic physical and mechanical characteristics of the material of the protective element, its reinforcement and the characteristics of the external action of the projectiles. It is shown that the most dangerous cases, given the security of the structure, are those when the impact is repeated at equal intervals, in addition, the point of impact is closer to the middle of the protective element. The obtained theoretical results can be the basis for selection at the stage of designing the main physical and mechanical characteristics of the elements of engineering structures and their reinforcement in order to reliably protect personnel and equipment from the maximum possible impact on it of the shock series of projectiles. The reliability of the obtained results is confirmed by: a) generalization of widely tested methods to new classes of dynamical systems; b) obtaining in the limit case the consequences known in scientific sources concerning the linearly elastic characteristics of the elements of protective structures; c) their consistency with the essence of the physical process itself, which is considered in the work.

ON A TWO-POINT BOUNDARY VALUE PROBLEM FOR A SYSTEM OF DIFFERENTIAL EQUATIONS WITH MANY TRANSFORMED ARGUMENTS

A.M. Samoilenko’s numerical-analytic method is a well-known and effective research method of solvability and approximate construction of the solutions of various boundary value problems for systems of differential equations. The investigation of boundary value problems for new classes of systems of functional- differential equations by this method is still an actual problem. A boundary value problem for a system of differential equations with finite quantity of transformed arguments in the case of linear two-point boundary conditions is considered at this paper. In order to study the questions of the existence and approximate construction of a solution of this problem, we used a modification of A.M. Samoilenko’s numerical-analytic method without determining equation, i.e. the method has an analytical component only. Sufficient conditions for the existence of a unique solution of the considered boundary value problem and an error estimation of the constructed successive approximations are obtained. The use of the developed modification of the method is illustrated by concrete examples.

Радіомікропроцесорна технологія забезпечення безпеки на залізничному транспорті.

The need to minimize losses and accidents is an important factor in sustainable technical development. One of the industries characterized by a high level of danger is rail transport. This problem changes its scale with the increase in the number of vehicles, its traffic intensity and speed. Another special diffi-culty is that significant infrastructural development, which involves the construction of a large number of complex and expensive facilities such as interchanges, overpasses and underpasses, is impossible in today's economic environment. Therefore, there are some promising solutions aimed at developing and implementing a new class of systems that provide a high level of safety and are able to correct negative accident statistics and solve the problem of not harming people's lives on rail transport. The article is devoted to the problem of traffic safety at railway crossings, railway crosswalks and in the work areas of service personnel. An information approach aimed at improving traffic safety and timely informing road users about emergencies and dangerous situations in their area approach is developed in the work. It is offered to solve the mentioned above tasks at the expense of the creation of digital information systems of a new class. The main differences between the created systems are the use of microprocessor systems, wireless communications and energy-saving technologies. The systems themselves must meet modern requirements for reliability, fault tolerance, and dependability. The article describes some basic options for the implementation of control and information systems for railway crossings «Blagovist», railway crosswalks «Blagovist-Р» and for a mobile system for service personnel working on the tracks «Blago-vist-SP». The systems have technologies for autonomous operation and wireless transmission of infor-mation.

Hetero-tri-spin systems: an alternative stairway to the single molecule magnet heaven?

The search for molecule-based magnetic materials has stimulated over the years the development of extremely rich coordination chemistry. Various combinations of spin carriers have been investigated and illustrated by a plethora of hetero-spin complexes: 3d-nd, 3d-4f, 2p-3d, and 2p-4f. More recently, two other classes of hetero-spin complexes have grown rapidly: compounds containing three different paramagnetic metal ions, or one radical and two different paramagnetic metal ions (all within the same molecular entity). Such new classes of systems represent a challenge both from a synthetic and theoretical point of view. Indeed, the synthetic control and the understanding of the spin topology effect on the overall magnetic behavior from first-principles is a difficult problem to be solved. The presence of different spin carriers in a single molecule makes such compounds particularly interesting because they offer the possibility of developing new magnetic properties, different from those of hetero-bi-spin or homo-spin systems. A critical overview taking the case of 2p-3d-4f complexes is the focus of this perspective paper. An original organic picture of the state-of-art in this field and new hints about the main directions that should be pursued to achieve hetero-tri-spin systems with large anisotropy barriers, low quantum tunneling of magnetization and, possibly, large blocking temperatures are provided in this article through an analysis based on numerically revisiting already published data and a critical survey of the literature reported so far. The reasons for the limited success obtained for the largely used 3d-2p-4f topology are given along with the ones explaining the failure for the 2p-4f-3d case. The still never synthesized linear 2p-3d-4f spin topology seemed to be the most promising one based on the results obtained for the unique closed hetero-tri-spin closed triangular system synthesized so far.

Emerging Complexity in Distributed Intelligent Systems.

Distributed intelligent systems (DIS) appear where natural intelligence agents (humans) and artificial intelligence agents (algorithms) interact, exchanging data and decisions and learning how to evolve toward a better quality of solutions. The networked dynamics of distributed natural and artificial intelligence agents leads to emerging complexity different from the ones observed before. In this study, we review and systematize different approaches in the distributed intelligence field, including the quantum domain. A definition and mathematical model of DIS (as a new class of systems) and its components, including a general model of DIS dynamics, are introduced. In particular, the suggested new model of DIS contains both natural (humans) and artificial (computer programs, chatbots, etc.) intelligence agents, which take into account their interactions and communications. We present the case study of domain-oriented DIS based on different agents’ classes and show that DIS dynamics shows complexity effects observed in other well-studied complex systems. We examine our model by means of the platform of personal self-adaptive educational assistants (avatars), especially designed in our University. Avatars interact with each other and with their owners. Our experiment allows finding an answer to the vital question: How quickly will DIS adapt to owners’ preferences so that they are satisfied? We introduce and examine in detail learning time as a function of network topology. We have shown that DIS has an intrinsic source of complexity that needs to be addressed while developing predictable and trustworthy systems of natural and artificial intelligence agents. Remarkably, our research and findings promoted the improvement of the educational process at our university in the presence of COVID-19 pandemic conditions.

Multiple Hysteresis Jump Resonance in a Class of Forced Nonlinear Circuits and Systems

In this paper, a new class of systems with nonclassical jump resonance behavior is presented. Although jump resonance has been widely studied in the literature, this contribution refers to systems presenting a multiple hysteresis jump resonance phenomenon, meaning that the frequency response of the system presents more hysteresis windows nested within the same range of frequency. The analytical conditions for observing this type of behavior are derived and a design strategy to obtain multiple hysteresis jump resonance in circuits and systems presented.

Berezinskii-Kosterlitz-Thouless phase in two-dimensional ferroelectrics

The celebrated Berezinskii-Kosterlitz-Thouless (BKT) phase transition refers to a topological transition characterized, e.g., by the dissociation of vortex-antivortex pairs in two-dimensional (2D) systems. Such unusual phase has been reported in various types of materials, but never in the new class of systems made by one-unit-cell-thick (1UC) ferroelectrics (also coined as 2D ferroelectrics). Here, the use of a first-principles-based effective Hamiltonian method leads to the discovery of many fingerprints of a BKT phase existing in-between the ferroelectric and paraelectric states of 1UC tin tellurium being fully relaxed. Moreover, epitaxial strain is found to have dramatic consequences on the temperature range of such BKT phase for the 1UC SnTe. Consequently, our predictions extend the playground of BKT theory to a novel class of functional materials, and demonstrate that strain is an effective tool to alter BKT characteristics there.

A computational method for a class of systems of nonlinear variable-order fractional quadratic integral equations

This paper develops an accurate computational method based on the shifted Chebyshev cardinal functions (CCFs) for a new class of systems of nonlinear variable-order fractional quadratic integral equations (QIEs). In this way, a new operational matrix (OM) of variable-order fractional integration is obtained for these cardinal functions. In the proposed method, the unknown functions of a system of nonlinear variable-order fractional QIEs are approximated by the shifted CCFs with undetermined coefficients. Then, these approximations are substituted into the system. Next, the OM of variable-order fractional integration and the cardinal property of the shifted CCFs are utilized to reduce the system into an equivalent system of nonlinear algebraic equations. Finally, by solving this algebraic system an approximate solution for the problem is obtained. The main idea behind this approach is to reduce such problems to solving systems of nonlinear algebraic equations, which greatly simplifies the problem. Convergence of the presented method is investigated theoretically and numerically. Furthermore, the proposed approach is numerically evaluated by solving some test problems.

Expert assessment systems to support decision-making for sustainable development of complex technological and socio-economic facilities

In this paper, we investigate problems of decision making in management systems for the sustainable development of complex technological and socio-economic facilities. We show both the limitations of traditional expert systems and decision support systems, and the necessity of using expert evaluation technologies to find possible development strategies. Based on that we substantiate the need of creating a new class of systems, i.e. Automated eXpert Assessment Systems, and propose their organizational structure and design principles. We substantiate the level of automation of the work performed during the examinations and describe the composition of models and computer programs we recommend for creating effective automated expert assessment systems and corresponding technology. In the paper, we give examples of using the proposed method for various areas of human activity, in the management of urban infrastructure and e-learning at the universities, and show the effectiveness of the developed approach.

Adaptive estimation of component faults and actuator faults for nonlinear one‐sided Lipschitz systems

SummaryFault estimation for classical nonlinear Lipschitz systems has been subject to several research works. So far, much less interest has been given to the more generalized class of systems, namely, one‐sided Lipchitz systems. Dealing with component faults and actuator faults, only very few works have been done to reconstruct these types of faults for this new class of systems. A major limitation of the previous works is that the fault vector to be estimated there does not give any information about the actual faulty physical parameters of the system, so component faults and actuator faults are not distinguishable. In this paper, a set of possible faulty parameters in the system is estimated. Component faults and actuator faults are separated and distinguished. The effectiveness of the proposed method is shown through simulations for a numerical example.