System Topology Research Articles

Breaking and resurgence of symmetry in the non-Hermitian Su-Schrieffer-Heeger model in photonic waveguides

Symmetry is one of the cornerstones of modern physics and has profound implications in different areas. In symmetry-protected topological systems, symmetries are responsible for protecting surface states, which are at the heart of the fascinating properties exhibited by these materials. When the symmetry protecting the edge mode is broken, the topological phase becomes trivial. By engineering losses that break the symmetry protecting a topological Hermitian phase, we show that a new genuinely non-Hermitian symmetry emerges, which protects and selects one of the boundary modes: the topological monomode. Moreover, the topology of the non-Hermitian system can be characterized by an effective Hermitian Hamiltonian in a higher dimension. To corroborate the theory, we experimentally investigated the non-Hermitian one- and two-dimensional SSH models using photonic lattices and observed dynamically generated monomodes in both cases. We classify the systems in terms of the (non-Hermitian) symmetries that are present and calculate the corresponding topological invariants. Published by the American Physical Society 2024

Design and reliability analysis of converter topology for Micro Grid system through optimal switching control

Design and reliability analysis of converter topology for Micro Grid system through optimal switching control

Application of Q-learning algorithm based on heterogeneous sensor networks in higher education teaching management

With the rapid advancement of information technology and online technologies, it has become imperative for all colleges and universities to address the challenge of leveraging modern management methods to enhance management efficiency, level, and practices. In the realm of educational institution management, the learning management system stands as the cornerstone of contemporary campus management and the entire campus computer network. In this article, the Q-learning algorithm, specifically applied to a heterogeneous cellular network, is employed to investigate the issues pertaining to teaching management in colleges and universities.The design and implementation of the university teaching management system mainly uses heterogeneous cellular networks to establish a physical model of the Q-learning algorithm, and then in the Rayleigh channel, the coverage factor and the system rate expression are derived in a closed form, and in a closed form Derive the energy efficiency expression, and then optimize the density of the basic micro-station algorithm to maximize performance. In the process of system design, this paper uses an algorithm to analyze the current research status of university teaching management, then proposes the research purpose and subject content, and analyzes the university's teaching management function and potential future functional requirements. When designing the university learning management system, it describes in detail the overall design concept, key technologies, system structure, and operating system structure and system topology. This research mainly focuses on the research of campus information management and Q learning algorithm. Based on the cellular network, a large number of campus management cases were analyzed and data fitting at the same time, and a set of Q-learning algorithm teaching management system based on heterogeneous cellular network was designed.

Simple model for the gap in the surface states of the antiferromagnetic topological insulator MnBi[formula omitted]Te[formula omitted]

We study the influence of the antiferromagnetic order on the surface states of topological insulators. We derive an effective Hamiltonian for these states, taking into account the spatial structure of the antiferromagnetic order. We obtain a typical (gapless) Dirac Hamiltonian for the surface states when the surface of the sample is not perturbed. Gapless spectrum is protected by the combination of time-reversal and half-translation symmetries. However, a shift in the chemical potential of the surface layer opens a gap in the spectrum away from the Fermi energy. Such a gap occurs only in systems with finite antiferromagnetic order. We observe that the system topology remains unchanged even for large values of the disorder. We calculate the spectrum using the tight-binding model with different boundary condition. In this case we get a gap in the spectrum of the surface states. This discrepancy arises due to the violation of the combined time-reversal symmetry. We compare our results with experiments and density functional theory calculations.

Review paper on multilevel converters topology for VSC-based HVDC transmission system connected offshore wind power plant

This review paper offers a comprehensive analysis of multilevel converters (MLCs) within Voltage Source Converter (VSC)-based High Voltage Direct Current (HVDC) transmission systems, focusing on their integration with offshore wind power plants. Through an exhaustive exploration, the paper investigates various MLC configurations and control strategies, assessing their potential to enhance the performance, efficiency, and reliability of offshore wind energy integration into the power grid. By examining the intricate interplay between MLCs, VSC-based HVDC systems, and offshore wind power plants, this review aims to provide valuable insights into the evolving landscape of renewable energy integration technologies. Key topics covered include an overview of offshore wind power generation, the significance of HVDC transmission for offshore wind farms, and the role of MLCs in overcoming integration barriers. Furthermore, the paper delves into control strategies, performance evaluation metrics, and future perspectives and challenges. Through its in-depth analysis, this review contributes to a deeper understanding of the potential of MLCs in advancing the efficiency and reliability of VSC-based HVDC systems, ultimately facilitating the seamless integration of offshore wind energy into the broader power grid.

ST-AGNet: Dynamic power system state prediction with spatial–temporal attention graph-based network

Accurate and timely prediction of power system states is one of the most important challenging tasks in modern power systems. Considering the integration of renewable energy sources, recent deep learning-based models have been well studied and found to have benefits in exploiting spatial–temporal relationships in power system data. However, the complexity of different power system topology structures is not substantially captured since the existing models did not fully consider the graph-based information retrieved from power networks. To resolve the problem, a spatial–temporal attention graph-based network (ST-AGNet), an adaptive power system state prediction approach that utilizes graph-based information data to account various typologies of complex power systems, is proposed. Initially, the power flow model is used for generating historical system state data. With the graph-based topology information, the input dataset with the spatial and temporal features is fed into the proposed network for the training and validating process. Meanwhile, the connectivity of the time-varying graph-based information are accounted in the proposed model. Case studies demonstrate the superiority of the ST-AGNet model over the existing baselines under four different scales of complex systems, which can significantly support dynamic power system analysis and operational tasks.

Residential urban heritage space identification, delimitation, and potential assessment model based on space syntax

In the era of post-modernization, profound transformations in urban spaces have led to significant shifts in the spatial composition paradigms of contemporary urban heritage. Research on this process is crucial for elucidating the spatial pathways and compositional changes in the modernization transformation of urban heritage. This study aims to establish identification indicators and assessment systems for the spatial structure of urban residential environments exhibiting historical characteristics and heritage potential through a comparative analysis of residential urban heritage spatial paradigms in historic cities in China and Japan. First, grounded in space syntax theory, this study selected residential urban heritage in Suzhou’s Pingjiang Historic District and Uji’s Nakauji District as research cases. Utilizing road network data, this study analyzed the Life Integration (Int.VR1000) and Global Integration (Int.VR5000) of urban heritage spaces, thereby constructing a spatial topology system for heritage spaces. Second, the study employed urban spatial entropy indicators, such as architectural density entropy, spatial morphology entropy, and function mixing entropy, to quantitatively describe the spatial structure, consequently establishing a heritage space morphological structure indicator system. Finally, spatial clustering methods are used to integrate the spatial topology system with the morphological structure indicator system, resulting in a feature model for residential urban heritage spaces. The research results indicate that the transformation path of residential space paradigms is mainly influenced by spatial topology, affecting the structure of residential heritage spaces in three aspects: functional layout, building density, and spatial form. This phenomenon, in turn, impacts population distribution and the migration of living spaces. However, at the same time, the “resistance effect” of street and lane spaces and the limitations of architectural forms on spatial functions have protected the integrity and authenticity of the internal space.

Assessment of an auto-routing method for topology generation of aircraft power supply systems

During early phases of aircraft development, overall systems design is performed to estimate relevant system design parameters such as mass, power consumption, and compliance with architectural requirements (redundancy). The GeneSys software framework has been developed for parametric modeling of aircraft on-board systems for overall systems design. To this end, model-based architecture definition, topology generation (components positioning and connections routing), and system sizing are conducted. The topology generation is currently performed using design templates containing knowledge-based heuristics derived from systems topologies of existing aircraft. However, using such design templates limits their generic application to novel aircraft models because exceptions for geometric differences between these models need to be implemented. This especially applies to the topology generation of power supply systems (electric, hydraulic) due to their high number of interfaces to consumer systems. To overcome these limitations, an automated routing method is presented in this paper as a generic approach for topology generation. With this method, the system topology is generated based on a defined routing network, which comprises areas of the aircraft for allowed components positioning and connections routing. Using Dijkstra’s algorithm, the shortest path connections are found within the established routing network. Furthermore, boundary conditions for routing, for instance adding a cost function for power segregation, can be defined. An assessment of the automated routing method applied on the electric power supply system is performed using qualitative parameters such as the capability to adapt the routing network. Quantitative parameters like cable length and system mass are assessed as well.

Reconstructing transient pressures in pipe networks from local observations by using physics-informed neural networks

Reconstructing transient states presents significant challenges, particularly within complex pipe networks. These challenges arise due to nonlinear behaviours, inherent uncertainties in the system, and limitations in data availability. This work proposed a novel approach employing Physics-Informed Neural Networks (PINN) to reconstruct transient states in pipe networks, even with limited sensor data. To integrate the complex topology of pipe network systems into neural networks, the method integrates the PINN framework with an efficient elastic water column (EWC) model which can be simply formulated across diverse pipe network configurations. The results showed the proposed PINN method can accurately reconstruct the pressure and flow variation at unmonitored locations, even provided with noisy data at a limited number of locations. One of its advantages lies in its ability to effectively capture extreme values that hold potential significance for pipe infrastructure, providing a promising avenue for pipe failure analysis and enhanced safety management. Laboratory experiments have also been conducted to validate the efficacy and reliability of this method, thus further underlining its potential for real-world applications.

Synthesis and catalytic performance of One-Dimensional coordination polymers for Knoevenagel condensation under green conditions

This work presents the synthesis, characterization, and catalysis application of two one-dimensional coordination polymers. The structures were obtained through a two-step synthesis method, involving the combination of the ligands 5-sulfoisophthalic acid (ACSO3) and isonicotinylhydrazine (INH) with Zn(II), designated as 1, or Cu(II), designated as 2, resulting in a ladder-shaped topology system. Compound 1 was thoroughly characterized using single-crystal X-ray diffraction, along with complementary techniques such as FT-IR spectroscopy, elemental analysis, and thermogravimetric analysis. These analyses provided insights into its bifunctional catalytic structure. Moreover, the heterogeneous catalytic activity of compound 1 was evaluated in Knoevenagel condensation reactions using various solvents. The catalyst exhibited high conversion rates and recyclability under mild conditions, particularly noteworthy when using eco-friendly solvents, establishing it as a green catalyst. A computational simulation was conducted to explore the surface properties of 1, providing a comprehensive description of its bifunctional properties.

Geometrical method for a fast practical static stability region evaluation of a smart microgrid

This paper introduces an innovative approach to the offline Static Security Assessment (SSA) of smart MicroGrids (MG). By defining a specific region in the operating hyperspace, the stability of a MG is evaluated in a practical way, through the study of violations of voltage limits settled by protection relays. This method determines whether operating points, generated by Economic Dispatch algorithms, are feasible or not. Unlike traditional methods, it doesn't require continuous training on large datasets if the system topology doesn’t change. The method proactively explores the operating region offline, enabling quick assessment of operational security. By analyzing the feasibility region in the hyperspace from a geometrical perspective, it provides rapid insights of the system security status. This eliminates the need for computationally expensive trajectory studies involving complex equations and online iterative procedures, as applied in energy function approaches and conventional methods like the continuation load flow. The methodology is tested by simulation on a case study reproducing a subset of the experimental MG installed at the PrInCE Laboratory of the Polytechnic University of Bari.

Towards a Digital Representation of Building Systems Controls

Energy monitoring and performance optimization processes play a significant role in ensuring energy-efficient building operation. However, the current implementation of these processes requires substantial time and effort due to the fragmented and non-digital nature of technical building equipment information. To address these challenges, we demonstrate the application of the PLCont methodology within an ongoing monitoring process in a real building. PLCont utilizes Semantic Web Technologies and established RDF ontologies to describe the control topology. The digital representation of control functions aligns closely with the IEC standard 61131-3, and the PLCont ontology establishes a connection between the topology and the control functions. We compare the conventional approach and the PLCont methodol-ogy using the supply air temperature control of an Air Handling Unit (AHU) as a use case. A graphical user interface built upon the PLCont backend provides a comprehensive represen-tation of the system's functionality. It displays the system topology as a digital HVAC schema, the function code exported from the PLC, time-series data plots, and textual descriptions of implemented functions. We demonstrate how this approach enhances transparency and facil-itates the identification and elimination of faulty system behavior, ultimately contributing to the optimization and energy efficiency of building systems.

Distributed active vibration control for helicopter based on diffusion collaboration

The active vibration control technology has been successfully applied to several helicopter types. However, with the increasing of control scale, traditional centralized control algorithms are experiencing significant increase of computational complexity and physical implementation challenging. To address this issue, a diffusion collaboration-based distributed Filtered-x Least Mean Square algorithm applied to active vibration control is proposed, drawing inspiration from the concept of data fusion in wireless sensor network. This algorithm distributes the computation load to each node, and constructs the active vibration control network topology of large-scale system by discarding the weak coupling secondary paths between nodes, achieving distributed active vibration control. In order to thoroughly validate the effectiveness and superiority of this algorithm, a helicopter fuselage model is designed as the research object. Firstly, the excellent vibration reduction performance of the proposed algorithm is confirmed through simulations. Subsequently, specialized node control units are developed, which utilize STM32 microcontroller as the processing unit. Further, a distributed control system is constructed based on multi-processor collaboration. Building on this foundation, a large-scale active vibration control experimental platform is established. Based on the platform, experiments are carried out, involving the 4-input 4-output system and the 8-input 8-output system. The experimental results demonstrate that under steady-state harmonic excitation, the proposed algorithm not only ensures control effectiveness but also reduces computational complexity by 50%, exhibiting faster convergence speed compared with traditional centralized algorithms. Under time-varying external excitation, the proposed algorithm demonstrates rapid tracking of vibration changes, with vibration amplitudes at all controlled points declining by over 94%, proving the strong robustness and adaptive capability of the algorithm.

Methods, Techniques, and Algorithms of Synchronous Multi-Zone Modulation of Signals of Voltage Source Inverters (literature review)

This publication provides a brief overview of the results of research work in the field of developing alternative methods, schemes, and algorithms of synchronous multi-zone modulation of signals of inverters of power conversion systems with reduced switching frequency of power switches. In particular, in the mentioned researches, the basic strategies, schemes, and algorithms of synchronous multi-zone modulation have been fur-ther developed, modernized, modified, and disseminated in relation to new promising topologies of power conversion systems, including: two-inverter-based electric drives with open windings of electrical motor; drive systems based on electric motor with two stator windings; dual three-phase electric drives of symmetrical and asymmetric type; five-phase power conversion systems, powerful six-phase systems based on four inverters, and two-inverter-based and three-inverter-based photovoltaic installations with multi-winding transformer. It is shown that the developed schemes and algorithms of synchronous space-vector modulation applied for control of inverter-based systems provide continuous synchronization and symmetry of the basic voltage waveforms of systems during the whole control range. It provides minimization of even harmonics and undesirable subhar-monics (of the fundamental frequency) in spectra of the basic voltages of systems, leading to reducing of losses in systems and to increasing of its efficiency. Based on a comparative analysis of the integral spectral character-istics of the phase and line voltages of the systems, recommendations are formulated for the rational choice of schemes and algorithms of synchronous modulation for the relevant installations, depending on the modes of their operation.

Influence of inflow conditions on simplified heavy vehicle wake

In the current study, the impact of various inflow conditions, including turbulent wind profiles and turbulent intensity, on the wake flow topology of a simplified ground transportation system (GTS) model was investigated using the improved delayed detached eddy simulation. The reliability and accuracy of the numerical method adopted in this paper were verified against the results comprising the aerodynamic drag and the wake flow structure of the GTS model obtained from the large eddy simulation and the experimental data. The research results indicate that turbulent winds characterized by logarithmic and uniform velocity profiles resulted in significantly different wake flow topologies yet exhibit the same dominant frequency. The turbulent intensity also plays a crucial role in the wake of the GTS model. It is observed that an increase in turbulence intensity corresponds with a rise in the aerodynamic drag. Specifically, when the turbulence intensity is set at 15%, there is a 3.68% increase in the aerodynamic drag of the GTS model compared to a case where the turbulence intensity was only 5%. In addition, the turbulent intensity is critical to the dominant frequency characteristics of the wake region of the GTS model. These results demonstrate that both the velocity profiles and the turbulence intensities significantly influence the wake flow topology and aerodynamic drag of the GTS model, providing a valuable reference for establishing appropriate inflow conditions and exploring the formation mechanism of flow topology in the wake of the GTS model.

Three-Level DC-DC Boost Converter for Wind Energy Conversion

In recent years, advancements in power converter technology for wind energy conversion systems have aimed to enhance power output, increase reliability, and improve overall efficiency. However, achieving a fixed and high-power DC output remains a challenge. This study explores three modes of operation for a DC-DC boost converter to enhance fixed DC output, essential for various applications like battery charging and electronics. The research categorizes DC system topologies based on factors such as setup complexity, cost-effectiveness, and performance metrics. It proposes a DC/DC conversion approach that offers cost-effectiveness and efficiency, aiming to set a new standard in topology for future converters. The study addresses key challenges in the efficiency of the step-up process of DC/DC converters, focusing on parameter design, operational principles, and control strategies. Simulation results confirm the effectiveness of the suggested approach, emphasizing its future potential for non-isolated high step-up DC/DC converters. Reduced device voltage stress and increased efficiency represent the two advantages of the suggested three-level DC-DC boost converter, which combines a standard boost converter with a switched capacitor function to supply three capacitors in series. Simulation results demonstrate the converter’s effectiveness in a wind energy conversion system, showcasing its potential for high-power applications.

Investigation of Different Communication Topologies for Cooperative Adaptive Cruise Control Systems

After Adaptive Cruise Control (ACC) system applications, Cooperative Adaptive Cruise Control (CACC) systems are becoming an important part of automotive technology and industry in autonomous vehicles convoy applications. Together with this developing technology, CACC systems use vehicle to vehicle (V2V) communication to automatically transmit the movement information of vehicles. In this context, ACC systems use Radar or LIDAR measurements while CACC systems also consider the acceleration of the preceding vehicle. In this paper, the forms of information transmission between vehicles in autonomous vehicle convoys using CACC systems have been examined. From these forms of information transmission, the leader following, the predecessor follow-ing and the leader – predecessor following topologies have been considered. For each topology, an autonomous vehicle convoy consisting of eight vehicles was modeled in the MATLAB/Simulink environment. The feedforward and the feedback control system structure were given for CACC and ACC systems. For different communication topologies, the position-time, the speed-time, the acceleration-time and the headway time-time results were obtained. The maximum intervehicle distance error plots for each vehicle in different topology convoys were given to analyze the dynamic behavior of the convoys. The results have been analyzed in terms of the maximum intervehicle distance, the maximum speed, the minimum and the maximum acceleration, and the maximum headway time deviation from the desired headway time.

Bulk-Boundary Correspondence in Point-Gap Topological Phases.

A striking feature of non-Hermitian systems is the presence of two different types of topology. One generalizes Hermitian topological phases, and the other is intrinsic to non-Hermitian systems, which are called line-gap topology and point-gap topology, respectively. Whereas the bulk-boundary correspondence is a fundamental principle in the former topology, its role in the latter has not been clear yet. This Letter establishes the bulk-boundary correspondence in the point-gap topology in non-Hermitian systems. After revealing the requirement for point-gap topology in the open boundary conditions, we clarify that the bulk point-gap topology in open boundary conditions can be different from that in periodic boundary conditions. On the basis of real space topological invariants and the K theory, we give a complete classification of the open boundary point-gap topology with symmetry and show that the nontrivial open boundary topology results in robust and exotic surface states.

Topological phases and non-Hermitian topology in tunable nonreciprocal cyclic three-mode optical systems

We propose a method for simulating a 1D non-Hermitian Su-Schrieffer-Heeger model with modulated nonreciprocal hopping using a cyclic three-mode optical system. The current system exhibits different localization of topologically nontrivial phases, which can be characterized by the winding number. We find that the eigenenergies of such a system undergo a real-complex transition as the nonreciprocal hopping changes, accompanied by a non-Bloch parity-time symmetry breaking. We explain this phase transition by considering the evolution of saddle points on the complex energy plan and the ratio of complex eigenenergies. Additionally, we demonstrate that the skin states resulting from the non-Hermitian skin effect possess higher-order exceptional points under the critical point of the non-Bloch parity-time phase transition. Furthermore, we investigate the non-Hermitian skin phase transition by the directional mean inverse participation ratio and the generalized Brillouin zone. This work provides an alternative way to investigate the novel topological and non-Hermitian effects in nonreciprocal optical systems.

Multi-Objective Optimization of Yokeless and Segmented Armature Machine for In-Wheel Traction Applications Based on the Taguchi Method

For electrical machines with complex structures, the design space of parameters can be large with high dimensions during optimization. Considering the calculation cost and time consumption, it is hard to optimize all the design parameters at the same time. Therefore, in that situation, sensitivity analysis of these design parameters is usually used to sort out crucial parameters. In this paper, the sensitivity analysis-based Taguchi method is applied to optimize the axial-flux permanent magnet (AFPM) machine with yokeless and segmented armature (YASA) topology for an in-wheel traction system. According to the key parameters and their sensitivity analysis, the optimal machine scheme to meet the performance requirements can be formed. In this case study, the machine performance is improved significantly after optimization. Lastly, the experimental results verify the accuracy of the model used in this study.