Two-level System Research Articles

A two-level MPC method for the operation of a gas pipeline system under demand variation

A gas pipeline system is in an almost continual state of transition due to changing gas demand. A control method is required to keep a gas pipeline operating in an energy-saving status and provide reliable transmission service for the customers. Model predictive control (MPC) predicts the future states of a system, making it suitable for following gas demand changes. However, to avoid computation time challenges associated with formulating the MPC problem as a large-scale MINLP, an online two-level MPC system is proposed, comprising an upper-level economic MPC (EMPC) and a lower-level tracking MPC (TMPC). EMPC adopts energy cost as the objective function and utilizes a simplified nonlinear model to address long-horizon optimization, while TMPC tracks the status optimized in EMPC, to find the optimal output pressure and the on-off status of the compressors and compressor stations. The performance of the method is demonstrated through application to case studies.

Quantum speed limits of quantum system in colored environments

In this paper, we investigate quantum speed limits (QSLs) of a two-level system in the colored environments which are described by stochastic processes. We present QSL can be affected by the correlation time, the partitions of the constituent elements of the two-level system in different colored environments: the Ornstein–Uhlenbeck environment, simple fluctuating bottleneck environment, and the Dichotomic (two-state) environment. The investigations provide us a potential way to manipulate the quantum speed limit time (QSLT) of the quantum system in the colored environments. Our results could provide different insights on quantum control technologies of QSL and decoherent dynamics for the quantum computation.

THE FREQUENCY METHOD FOR OPTIMAL IDENTIFICATION OF CLOSE-LOOP SYSTEM ELEMENTS

Context. The article is devoted to overcoming the contradictions between the assumptions adopted in known methods of closedloop control system identification and the design and conditions of its operation. The article presents a new method of identifying the transfer functions matrix of a two-level closed-loop control system element, which functions under the conditions of multidimensional stationary centered random influences.
 Objective. The purpose of the study, the results of which are presented in this paper, is to extend the indirect identification method to the case of estimating one of the two-level closed-loop control system elements’ dynamics model based on passive experiment data.
 Method. To solve the optimal identification problem, a variational method for minimizing the quality functional on the class of fractional-rational transfer function matrices was used.
 Results. As a result of the research, the identification problem formulation was formalized, the rules for obtaining experimental information about the input and output signals were determined, the rules for identifying the transfer functions matrix of a two-level closed-loop control system element, which minimizes the sum of the variances of identification errors in the frequency domain, and the verification of these rules was carried out.
 Conclusions. Justified rules allow to correctly determine transfer functions matrices of the closed-loop systems selected element when fulfilling the defined list of conditions. The closed-loop systems control paths signals analysis proves the possibility of the effect of changing these signals statistical means, even under conditions of only centered stationary input influences actions on the system. Based on this, the further development of research can be aimed at overcoming such effects.

Graph-based two-level indicator system construction method for smart city information security risk assessment

<p>The rapid development of urban informatization has led to a deep integration of advanced information technology into urban life. Many decision-makers are starting to alleviate the adverse effects of this informatization process through risk assessment. However, existing methods cannot effectively analyze internal and hierarchical relationships because of the excessive number of indicators. Thus, it is necessary to construct an indicator's dependency graph and conduct a comprehensive hierarchical analysis to solve this problem. In this study, we proposed a graph-based two-level indicator system construction method. First, a random forest was used to extract the indicators' dependency graph from missing data. Then, spectral clustering was used to separate the graph and form a functional subgraph. Finally, PageRank was used to calculate the prioritization for each subgraph's indicator, and the two-level indicator system was established. To verify the performance, we took China's 25 smart cities as examples. For the simulation of risk level prediction, we compared our method with some machine learning algorithms, such as ridge regression, Lasso regression, support vector regression, decision trees, and multi-layer perceptron. Results showed that the two-level indicator system is superior to the general indicator system for risk assessment.</p>

Dynamic optimisation of unbalanced distribution network management by model predictive control with Markov reward processes

In this work, a two-level control system is used to minimize the total active power losses of an active distribution system connected to the external grid and composed of a wind turbine, two photovoltaic power sources, and two batteries. At the first control level, a model-based predictive control (MPC) is run, using non-homogeneous Markov reward models for wind power prediction and homogeneous Markov reward models for photovoltaic power. At the second level, an algorithm is run for optimal management of voltage control assets, such as voltage regulating transformers, to minimize losses. Different scenarios have been considered, highlighting the advantages of using an MPC framework. This results in an optimization process that can be influenced by different time horizons depending on whether or not the MPC is applied. The predictions allow considering a long-horizon stepwise optimization process that leads to an increasing number of variables along with the decrease of total active power losses. When the MPC is not applied, a short-horizon analysis is performed with a decrease in both the number of variables and the quality of the results. Different cases are considered in which the nominal power of a photovoltaic unit and the battery capacity are modified.

ОРГАНІЗАЦІЯ ТА ЕФЕКТИВНІСТЬ МОНІТОРИНГУ ДІЯЛЬНОСТІ ПІДПРИЄМСТВА

In contemporary business settings, it's essential to establish a dynamic information and analytical framework to facilitate effective managerial decisions. This involves implementing a monitoring system to track internal processes and external factors, providing comprehensive and timely data for decision-making. The article aims to outline the theoretical and methodological underpinnings of such a monitoring system, focusing on its practical application in monitoring, diagnosing, modeling, and managing various aspects of a company's operations. Drawing from scholarly works and diverse sources, including periodicals and online materials, the study employs methods such as comparative analysis and content analysis. It argues that modern enterprise monitoring should not merely be an information system but should also serve as a vital support for informed decisionmaking. The article proposes a two-level monitoring system comprising an information base and methodological framework to fulfill evaluation, analytical, prognostic, and management functions. It identifies and examines the structural components of this system, including the database and knowledge base. Furthermore, it defines key elements such as goals, objects, subjects, principles, and functions, forming the conceptual foundation of the monitoring system. Building upon these foundations, the article presents a model for the enterprise's monitoring system as an integral part of the decision-making process. The practical significance of this conceptual model lies in its ability to develop a comprehensive system for monitoring, evaluating, and forecasting enterprise activities, thereby facilitating timely management decisions. Effective implementation of such a system requires robust technological infrastructure, skilled personnel, and organizational commitment to data-driven decision-making practices. Additionally, ongoing evaluation and refinement are necessary to adapt the monitoring system to evolving business environments and information needs. Overall, the integration of advanced monitoring capabilities into managerial processes enhances agility, resilience, and competitiveness in today's dynamic business landscape.

Bandwidth of quantized surface plasmons: competition between radiative and nonradiative damping effects.

We investigate the damping effects of coherent electron oscillations on the bandwidth of a quantized nanoparticle plasmon resonance. The nanoparticle (NP) is treated as a two-level quantum system, and the total relaxation time involves both the population relaxation time associated with radiative processes and the collisional relaxation time associated with nonradiative processes that result in dephasing/decoherence of electron oscillations. We describe the optical response of NPs to an external electromagnetic field by the optical Bloch equations employing the density matrix formalism to capture the quantum description nature of dipolar plasmon resonance and suggest a generalized criterion for the validity of dipole approximation. Then we explore the competition between the radiative and nonradiative damping in determining the plasmon bandwidth of two typical NP models; metallic nanospheres and dielectric core-metal shell NPs (nanoshells). We show that the frequency of plasmon resonance, in addition to the NP size, plays an important role in the competition between the damping mechanisms. Consequently, the damping processes are significantly influenced by the factors that determine the resonance frequency, such as the core size, the dielectric constant of the medium, and the shell thickness (for nanoshells). For both models of NPs, we identify the optimum parameters that achieve a narrower plasmon bandwidth (minimal damping), which is a prerequisite for advanced sensing and medical applications. We demonstrate excellent agreement of the simulated spectral features of the plasmon resonance with previously reported experimental results for a single NP where the inhomogeneous broadening of the plasmon line is excluded. For NP ensembles where inhomogeneous broadenings and interface chemical effects are significant, our theoretical approach successfully predicts the overall trend of size-dependent damping rates.

Inverse engineering for robust state transport along a spin chain via low-energy subspaces

Quantum state transfer (QST) plays a central role in the field of quantum computation and communication, but its quality will be deteriorated by the ubiquitous variations and noise in quantum systems. Here we propose robust and nonadiabatic protocols for transmitting quantum state across a strongly coupled spin chain, especially in the presence of unwanted disorders in the couplings. To this end, we approximately map the low-energy subspaces of the odd-size Heisenberg chain to a two-level system, and derive the sensitivity of the final fidelity with respect to systematic deviations or time-varying fluctuations. Subsequently, leveraging the flexibility of the inverse-engineering technique, we optimize the state-transfer robustness concerning these perturbations individually. The resulting schemes allow for more stable QST than the original accelerated schemes and only require manipulating the two boundary couplings instead of the whole system, which open up the possibility of fast and robust information transfer in spin-based quantum systems.

ОПТИМІЗАЦІЯ ПЛАНІВ ВИРОБНИЦТВА ТА ДОСТАВКИ ПРОДУКЦІЇ В ЛОГІСТИЧНИХ ЛАНЦЮГАХ З ВРАХУВАННЯМ ВИТРАТ ПІДПРИЄМСТВА НА МАРКЕТИНГ

In the article static model of enterprise interaction planning of supply chains within the framework of VAT-classification into account the marketing activity of a plant analyzed. The two-level system of A type is under consideration. The model describes the co-ordination among main participants of supply chain with the aim to optimize the total logistic costs for production and transportation of finished products. It is supposed that there are several plants-suppliers for manufacturing of complete set for a single plant which manufactures the finished products. It is considered that all enterprises-suppliers produce different complete sets. All produced in factories supplying complete sets are purchased by the manufacturer, which produces the final product of several items. Manufactured end products arrives at the warehouse, where it must be delivered to destinations within a few points of transshipment. It is possible to consider that in transfer points production of manufacturer is overloaded from one type of transport on another. It is supposed that demand for finished products is a some increasing function of advertising costs. The concrete form of such dependence may be found in result of corresponding market’s analyses for previous period. In more simple case it may be the linear dependence. It is supposed also that expected demand without cost for advertising is known in result of market analyses. This optimization model allows us to find out the optimal joint production and transportation plans and optimal advertising costs maximizing the total profit of enterprise. The experimental calculationsshow that interaction of marketing and logistics conceptions allows not only to increase the effectiveness of supply chain functioning as a whole but its every link, as well. In the future research, it is possible to perform different generalizations of results, given in the present article, for example, for investigation of more general optimization models and to study oligopolies for static and dynamic models of optimization of production plans innovative and marketing activity of enterprises-manufacturers.

Noise spectrum analysis of superconducting kinetic inductance detectors

As a newly developed pair-breaking superconducting detector, microwave kinetic inductance detectors are simple to integrate in the frequency domain and have already been used in astronomical detection and array imaging at the (sub)millimeter and optical wavelengths. For these applications, the dark noise level of kinetic inductance detector is one of the key performance indicators. Herein a noise power spectrum analysis method is introduced in detail, which can accurately and effectively analyze the noise spectrum of kinetic inductance detector in a wide frequency range. This method can well balance the noise spectrum resolution and variance performance, by taking the noise data at the resonance frequency with two sampling rates and setting the appropriate frequency resolutions for different frequency bands. This method is used to characterize and compare the noise of aluminum (Al) kinetic inductance detectors made from two different micromachining processes. We deposite a 25-nm-thick aluminum film on high-resistivity silicon substrate for one device, while place one silicon nitride (SiN<sub><i>x</i></sub>) film on the top and one on the bottom of the aluminum film for another device. It is found that the frequency noise of the device with two silicon nitride films is about 25% to 50% of the bare aluminum device. Using this double silicon nitride film fabrication technique, we further fabricate a few groups of lumped-element aluminum kinetic inductance detectors with various inductor and interdigitated capacitor designs. We investigate the noise properties of these devices at different microwave driven power and bath temperatures, and the experimental results show typical two-level system noise behaviors. Our work provides a standard method to characterize the noise power spectrum of kinetic inductor detector, and also paves the way to developing low-noise aluminum kinetic inductance detectors for terahertz imaging, photon-counting and energy-resolving applications.

ЕКСПЕРИМЕНТАЛЬНІ ДОСЛІДЖЕННЯ СЕРІЙНОЇ ДОРОЖНО-АЕРОДРОМНОЇ ЗАЛІЗОБЕТОННОЇ ПЛИТИ

The results of experimental studies of the load-bearing capacity and crack resistance of the serially produced road-airfield reinforced concrete slab PAG, manufactured at Velikodolinsky Reinforced Concrete Plant LLC by order of the Odessa State Academy of Construction and Architecture, are presented. In accordance with the regulatory documents in force in Ukraine, one of two possible loading schemes was considered ― with a load by a concentrated force applied on the cantilever part of the slab. The slab was tested on a specially made stand, which consists of four support posts connected in pairs by beams on which the slab rested. The load was applied along the width of the slab in steps ― 0.04 from the destructive load, along two concentrated vertical stripes. Each load stage ended with a five-minute hold, at the beginning and end of which readings were taken on the measuring instruments. All tests were carried out using two 30t jacks and a 50t dynamometer. The principle of operation of the jack was that its lower plane pressed on a two-level cross-beam system, and through it the load was distributed onto the slab. During testing, the applied load, deflections and deformations were recorded on the slabs. Dial indicators and deflectometers were used as measuring instruments. The process of crack formation on the surfaces of the slabs was observed using a Brinell tube in the places of the greatest opening of the cracks. As a result of the tests, the load-bearing capacity of the slab was 163.2 kN with a bending moment of 78.3 kNm. The load corresponding to the onset of cracking is 86.4 kN with a bending moment of 36.9 kNm. The maximum crack opening width was 1.0 mm. Based on the indicator readings, graphs of the dependence of relative deformation on load were constructed. Graphs of the dependence of deflections on load are constructed using data from two deflection meters. Before the first crack appears, the maximum deflection of the slab is 12.0% of the deflection recorded at the end of the tests.

Modelling assisted tunneling on the Bloch sphere using the Quantum Composer

The Bloch sphere representation is a geometric model for all possible quantum states of a two-level system that can be used to describe the time dynamics of a qubit. As explicit application, we consider the time dynamics of a particle in a double-well potential. In particular, we adopt a recent method for off-resonant excitations, the so-called SUPER principle (Swing Up of the quantum emitter population) driven by periodic electromagnetic fields, to the context of quantum tunnelling. We show that the tunnelling probability can be enhanced significantly when an appropriate oscillation of the potential height is introduced. Driven by a collaborative approach we call educator-developer dialogue, an updated version of the software Quantum Composer is presented. For educational purposes, we map the two lowest energy states of the 1D-Schrödinger equation to the Bloch sphere representation, leading to a rather clear and intuitive physical picture for the pertinent time dynamics.

Theoretical and methodological foundations of financial support for the development strategies of territorial communities

Subject. The article considers theoretical and methodological substantiation of using an analogue of the system of national accounts at the territorial level as the main tool to explore financial capabilities of territories for achieving the strategic planning goals. Objectives. We focus on highlighting the main advantages of the system of territorial accounts in the strategic planning system, underpinning the configuration of building financial balances of territories from the two-level system of balances (region – municipalities) to the use of a limited set of institutional sectors. Methods. The study rests on methodological principles of international system of national accounts, which serves as a standard for statistical analysis worldwide. Results. The paper shows the necessity and advantages of building a system of territorial accounts, especially in the context of strategic planning documents development, to define financial opportunities for development of territories, including remote ones. It discloses the methodology of building a system of national accounts based on the relationship of indicators of institutional sectors of the economy, highlights specifics of account formation of ‘corporations’, ‘public administration’, ‘households’ sectors, and identifies sources of official information for calculating the necessary indicators. Conclusions. The findings enable to identify outflows or inflows of financial resources at the regional and municipal level, to measure and evaluate the volume of production, income distribution, and formation of added value, contributing to improved management of financial resources and ensuring the stability of economic growth. This is especially relevant for determining strategic directions for Russia’s remote territories development, as low competitiveness of traditional industries, caused by natural and climatic characteristics of the territories, leads to dependence on external financial resources.

Probing Oxidation-Driven Amorphized Surfaces in a Ta(110) Film for Superconducting Qubit.

Recent advances in superconducting qubit technology have led to significant progress in quantum computing, but the challenge of achieving a long coherence time remains. Despite the excellent lifetime performance that tantalum (Ta) based qubits have demonstrated to date, the majority of superconducting qubit systems, including Ta-based qubits, are generally believed to have uncontrolled surface oxidation as the primary source of the two-level system loss in two-dimensional transmon qubits. Therefore, atomic-scale insight into the surface oxidation process is needed to make progress toward a practical quantum processor. In this study, the surface oxidation mechanism of native Ta films and its potential impact on the lifetime of superconducting qubits were investigated using advanced scanning transmission electron microscopy (STEM) techniques combined with density functional theory calculations. The results suggest an atomistic model of the oxidized Ta(110) surface, showing that oxygen atoms tend to penetrate the Ta surface and accumulate between the two outermost Ta atomic planes; oxygen accumulation at the level exceeding a 1:1 O/Ta ratio drives disordering and, eventually, the formation of an amorphous Ta2O5 phase. In addition, we discuss how the formation of a noninsulating ordered TaO1-δ (δ < 0.1) suboxide layer could further contribute to the losses of superconducting qubits. Subsurface oxidation leads to charge redistribution and electric polarization, potentially causing quasiparticle loss and decreased current-carrying capacity, thus affecting superconducting qubit coherence. The findings enhance the comprehension of the realistic factors that might influence the performance of superconducting qubits, thus providing valuable guidance for the development of future quantum computing hardware.

Generalised quantum speed limit for arbitrary time-continuous evolution

The quantum speed limit describes how quickly a quantum system can evolve in time from an initial state to a final state under a given dynamics. Here, we derive a generalised quantum speed limit (GQSL) for arbitrary time-continuous evolution using the geometrical approach of quantum mechanics. The GQSL is applicable for quantum systems undergoing unitary, non-unitary, completely positive, non-completely positive and relativistic quantum dynamics. This reduces to the well known standard quantum speed limit (QSL), i.e. the Mandelstam-Tamm bound when the quantum system undergoes unitary time evolution. Using our formalism, we then obtain a quantum speed limit for non-Hermitian quantum systems. To illustrate our findings, we have estimated the quantum speed limit for a time-independent non-Hermitian system as well as for a time-dependent non-Hermitian system namely the Bethe-Lamb Hamiltonian for general two-level system.

Stimulated emission in a CuInS2/ZnS core-shell quantum-dot-doped liquid-core optical fiber.

We fabricated QD liquid-core optical fibers by doping C u I n S 2/Z n S (CIS/ZnS) core/shell QDs with cladding times of 90 and 60min, respectively, and compared and analyzed their emission properties with those of bare core C u I n S 2 QDs. For CIS/ZnS core/shell QDs (with cladding time of 90min) doped fibers, their emission transmits the longest distance in the fiber, and the emission intensity is approximately 4.73 times that of bare-core QD-doped fibers. Additionally, the fact that the full-width at half-maximum is narrowing and the spectral intensity is rapidly increasing superlinearly with excitation power indicates that stimulated emission happens in the fiber. The optical performance was compared and showed good agreement with a theoretical two-level system model for the QDs confined in an optical waveguide.

Interplay of decoherence and relaxation in a two-level system interacting with an infinite-temperature reservoir.

We study the time evolution of a single qubit in contact with a bath, within the framework of projection operator methods. Employing the so-called modified Redfield theory, which also treats energy conserving interactions nonperturbatively, we are able to study the regime beyond the scope of the ordinary approach. Reduced equationsof motion for the qubit are derived in an idealistic system where both the bath and system-bath interactions are modeled by Gaussian distributed random matrices. In the strong decoherence regime, a simple relation between the bath correlation function and the decoherence process induced by the energy conserving interaction is found. It implies that energy conserving interactions slow down the relaxation process, which leads to a Zeno freezing if they are sufficiently strong. Furthermore, our results are also confirmed in numerical simulations.

A MODEL OF THE TWO-LEVEL SYSTEM FOR FORMING INFORMATION AND COMMUNICATION COMPETENCE OF STUDENTS IN GENERAL SECONDARY EDUCATION INSTITUTIONS

The work systematizes the authors’ experience of using information technologies in the educational process of a general secondary education institution and presents the authors’ model of effective development of students' information and communication competence based on it. A model of a two-level system of formation of information and communication competence of students in the educational process has been developed. At the first level of the model, teachers use information tools during lessons to form students' basic knowledge and skills. At the second level, information technologies are used by teachers in extracurricular activities as a tool for creating creative products of students (in particular, scientific research works, educational projects, posters, presentations, video demonstrations), as well as their own developments (pedagogical technologies, teaching aids, etc.), which contributes to the formation of students' comprehensive ability to apply acquired knowledge and skills in practice, and, therefore, information and communication competence. To implement the first level of the proposed model, a comparative analysis of the most common information tools was conducted, the results of which are presented using original schemes. Information tools that ensure high-quality educational process at the "Cossack Lyceum" were subject to analysis: learning management systems – Google Classroom and NZ.UA; video conferencing platforms - Zoom and Google Meet; online boards – Jamboard, IDroo and Flinga; tools for creating information content – Google Presentations, Canva, Prezi and Microsoft Sway; software for simulating natural processes – Phet and Mozaik Education; tools for creating interactive exercises – Mentimeter, Kahoot, Wordwall, Live Worksheets and Learning Apps. The implementation of the second level of the model is shown on the example of a student's creative product created by participating in the competition of the Small Academy of Sciences of Ukraine. We associate promising directions for further research with the development of methodological recommendations for the use of information and communication technologies at various stages of students' creative activity.

DISTANCE EDUCATION OF JUNIOR HIGH SCHOOL STUDENTS

A model of a two-level system of formation of information and communication competence of students in the educational process has been developed. At the first level of the model, teachers use information tools during lessons to form students' basic knowledge and skills. At the second level, information technologies are used by teachers in extracurricular activities as a tool for creating creative products of students (in particular, scientific research works, educational projects, posters, presentations, video demonstrations), as well as their own developments (pedagogical technologies, teaching aids, etc.), which contributes to the formation of students' comprehensive ability to apply acquired knowledge and skills in practice, and, therefore, information and communication competence.

Robustness of Wave-Particle Duality under Unruh Effect.

By considering a uniformly accelerated two-level system in an initial superposition state of a qubit, we investigate the loss of coherence induced by the acceleration. In addition, we investigate the impact of acceleration on the complementarity relation in a quantum interferometric circuit or quantum scattering circuit. We present an alternative approach to exploring acceleration effects through examination of quantum coherence decay and degradation in the interference pattern. Our investigations help to provide understanding of the consequences of decoherence induced by the Unruh effect on the wave-particle duality of a uniformly accelerated qubit.