Topology Control Research Articles

Topological controls on catchment‐scale sediment dynamics

AbstractThe episodic transfer of sediment from source to sink is a fundamental process in fluvial systems that influences river morphology, aquatic and riparian ecosystems, and risk from a variety of associated natural hazards. The hierarchical structure of river networks has been identified as a key control on spatiotemporal patterns of sediment routing at the catchment scale, but very few studies have systematically explored this relationship. In this paper, we investigate the role that drainage network topology plays in modulating sediment flux and morphodynamic activity. We simulate the geomorphological responses of four topologically distinct catchments from New Zealand's South Island to sequences of flood events using a landscape evolution model. Spatiotemporal variation in different types of geomorphological activity is assessed via a link‐based framework, and potential interrelationships between within‐network changes and discharge and sediment yield at the catchment outlets are explored to provide insights into relative levels of network connectivity. We also investigate the occurrence of geomorphic ‘hotspots’ in relation to network topology, and their impact on the downstream transfer of sediment in different network ‘types’. Dissected networks were found to exhibit much greater spatiotemporal variability in geomorphological activity compared to narrow, elongated networks where change was concentrated in mainstem reaches. The frequency and significance of geomorphological hotspots are shown to vary between network types, with strong contrasts evident between dissected networks with steep topography and elongated networks with more gentle gradients. Dissected networks exhibited mostly non‐linear relationships between within‐network geomorphological activity and outlet discharge and sediment yield. However, moderate to strong linear relationships between these variables were observed in mainstem‐dominated networks, indicating much greater levels of connectivity across a range of flow conditions. We discuss the implications of these findings on the transformation of environmental signals through fluvial systems with different topological structures, and the differential responses of catchments to disturbance events.

A Review of Axial-Flux Permanent-Magnet Motors: Topological Structures, Design, Optimization and Control Techniques

Axial-flux permanent-magnet (AFPM) motors are a kind of important motor with compact structure, high power density and high torque density. In this review, the progress of AFPM motors and their key technologies are analyzed and described, with emphasis on the topological structures, design and optimization methods and control techniques. Based on these analyses, the main findings of the review are the following: (1) the yokeless and segment armature (YASA)-type motors have great potential for development; (2) the multi-objective optimization design theories can be integrated and applied to optimize the design of AFPM motors; and (3) optimal control and sensorless control have important value in improving system reliability and reducing cost. Finally, highlights and prospects are provided for further advancing AFPM motors.

Squishing Skyrmions: Symmetry-Guided Dynamic Transformation of Polar Topologies Under Compression.

Mechanical controllability of recently discovered topological defects (e.g., skyrmions) in ferroelectric materials is of interest for the development of ultralow-power mechano-electronics that are protected against thermal noise. However, fundamental understanding is hindered by the "multiscale quantum challenge" to describe topological switching encompassing large spatiotemporal scales with quantum mechanical accuracy. Here, we overcome this challenge by developing a machine-learning-based multiscale simulation framework─a hybrid neural network quantum molecular dynamics (NNQMD) and molecular mechanics (MM) method. For nanostructures composed of SrTiO3 and PbTiO3, we find how the symmetry of mechanical loading essentially controls polar topological switching. We find under symmetry-breaking uniaxial compression a squishing-to-annihilation pathway versus formation of a topological composite named skyrmionium under symmetry-preserving isotropic compression. The distinct pathways are explained in terms of the underlying materials' elasticity and symmetry, as well as the Landau-Lifshitz-Kittel scaling law. Such rational control of ferroelectric topologies will likely facilitate exploration of the rich ferroelectric "topotronics" design space.

Метод оцінки зв’язності вузлів бездротових епізодичних мереж за умови застосування безпілотних літальних апаратів

The paper considers a method for assessing the connectivity of nodes of wireless episodic networks (WEN) under the condition of using unmanned aerial vehicles (UAVs). It is proposed to perform an evaluation of the connectivity of a pair of nodes according to a method, which is based on: an evaluation of geometric connectivity, which is limited to the maximum range of radio visibility at the physical level and the vulnerability interval of a given multiple access protocol at the channel level; assessment of information connectivity, which takes into account the presence of not only a physical connection of a given reliability, but also the presence of a free channel resource, a given amount of transmission delay at a given traffic limit value; assessment of the duration of connectivity taking into account the mobility of network nodes. On the basis of analytical mathematical models, the duration of connectivity of mobile subscribers (nodes) (MS) of the WEN consisting of MS and UAVs in direct radio visibility conditions and taking into account relaying was investigated. The connectivity of a pair of nodes is determined by the characteristics of different levels of OSI information interaction, such as radio range, channel bandwidth, information transmission delay, etc. It is shown that the duration of connectivity is directly proportional to the size of the coverage zone and inversely proportional to the speed of movement of nodes. The nature (scenario) of node mobility also affects the duration of connectivity. The simulation of the movement of nodes was carried out under 4 scenarios: «march», «skirmish», «random wandering in the field» and «random wandering in the city». The largest values of the duration of connectivity correspond to the third scenario, and the smallest to the second (with a fixed radius of the coverage area and the speed of movement of nodes). Thus, the average connection duration of the UAV-pedestrian connection in the event of a «difference» will be of the order of 36 minutes, and the UAV-car connection of the order of 5 minutes. The obtained results can be used in the UAV network topology control method.

Student psychology and social group optimizations based modified synchronous reference frame control topology for PV-DSTATCOM

This paper proposes the design of a modified synchronous reference frame (SRF) (MSRF) technique while incorporating student psychology based optimization (SPBO) and social group optimization (SGO) algorithms for solar photovoltaic (PV) and battery embedded distribution static compensator (DSTATCOM) for three-phase grid-tied system. For maximum power point tracking, the SPBO is used. The proposed MSRF controller provides satisfactory performance under different real-time cases. In case of night condition, the dc bus voltage is slightly reduced. MSRF may provide system stability under different faults. Due to the use of MSRF controller, the total harmonic distortion (THD) of grid current is 1.30% and the THD value is reduced by 9.72%, 23.98%, 26.14%, 66.23%, 36.59%, 38.97%, 56.38%, 30.85%, 41.44%, 75.05%, 77%, and 95.29%, respectively, as compared to the other techniques surfaced in the recent state-of-the-art literature such as (a) IT-2 fuzzy logic control (FLC), (b) type-I FLC, (c) PI control, (d) sliding mode control (SMC), (e) fuzzy and SMC, (f) indirect current control (ICC), (g) modified ICC, (h) SRF with teaching learning based optimization and SGO combination, (i) SRF with firefly and SGO combination, (j) SRF with particle swarm optimization and SGO combination, and (k) SRF control and without DSTATCOM.

Hybrid Approaches-Based Sliding-Mode Control for pH Process Control.

This paper presents two hybrid control topologies; the topologies are designed by combining artificial intelligence approaches and sliding-mode control methodology. The first topology mixes the learning algorithm for multivariable data analysis (LAMDA) approach with sliding-mode control. The second offers a Takagi-Sugeno multimodel approach, internal model, and sliding-mode control. The process under study is a nonlinear pH neutralization process with high nonlinearities and time-varying parameters. The pH process is simulated for multiple reference changes, disturbance rejection, and noise in the transmitter. Performance indices are used to compare the proposed approaches quantitatively. The hybrid control topologies enhance the performance and robustness of the pH process under study.

WS-OLSR: Multipoint Relay Selection in VANET Networks using a Wingsuit Flying Search Algorithm

The routing protocol is considered the backbone of network communication. However, mobility and bandwidth availability make optimizing broadcast message flooding a problem in an Optimized Link State Routing (OLSR)-based mobile wireless network. The selection of Multi-Point Relays (MPRs) has lately been proposed as a potential approach that has the added benefit of eliminating duplicate re-transmissions in VANET networks. Wingsuit Flying Search (WFS) is one of the swarm intelligent metaheuristic algorithms, it enables one to find the minimum number of MPR. In this study, a novel methodology based on (WFS) is called WS-OLSR (Wingsuit Search-OLSR). The (WS-OLSR) is investigated to enhance the existing MPR-based solution, arguing that considering a cost function as a further decision measure will effectively compute minimum MPR nodes that give the maximum coverage area possible. The enhanced MPR selection powered by (WFS) algorithm leads to decreasing MPR count required to cover 95% of mobile nodes, increasing throughput , and decreasing topology control which mitigates broadcasting storm phenomenon in VANETs.

Energy efficient topology control in Underwater Wireless Sensor Networks

Topology control in Underwater Wireless Sensor Networks (UWSNs) has been an active area of research owing to unique challenges an underwater environment poses. Node mobility due to water currents creates problems in localization and data transfer. In this paper, we propose an energy efficient topology control for mobile UWSNs using Expectation Maximization (EM) and Vickrey–Clarke–Groves (VCG) Auction mechanism. In the first stage, followed by a water current induced topology disturbance, the designated cluster head runs the EM algorithm to find similar sensor nodes in its proximity. In the second stage, cluster head runs VCG auction mechanism to compensate sensor nodes for costs incurred during data transfer. This ensures seamless data transmission between sensor nodes of heterogeneous ownership leading to higher energy efficiency. Simulations present higher energy efficiency of the network post EM and VCG steps. Comparison with existing protocols demonstrates superior performance of the protocol proposed in this paper.

Voltage Compensation and Energy Supplement-Based Power Conversion System and Its Experimental Verification

A voltage compensation and energy supplement-based power conversion system (VC-PCS) is proposed in this paper. A VC-PCS is a series connected to a battery that only processes fractional battery power; therefore, it has lower rated voltage and power in comparison with traditional PCSs. Compared with results of previous studies, the VC-PCS proposed herein can output bipolar voltage to meet voltage variation requirements and is a necessary and comprehensive improvement to previous research. First, its topology structure, working principle, and control strategy are comprehensively examined in this paper. Next, results of the simulations and physical experiments carried out are presented; the results show that the proposed VC-PCS is feasible in principle, and can be realized in physical applications.

Topological control of synthetic morphogenesis

Topological control of synthetic morphogenesis

Review on Virtual Inertia Control Topologies for Improving Frequency Stability of Microgrid

Renewable energy sources (RESs), such as solar and wind power, offer new technologies for meeting the world's energy requirements. The distributed generator (DG) based on RESs has no rotational mass and damping effects compared to the traditional power system with synchronous generators (SG). However, the increasing penetration level of DG based on RESs causes low inertia, a dampening effect on the dynamic performance of the grid, and stability. A solution to improve the frequency stability of such a system is to provide virtual inertia by using virtual synchronous generators (VSG), which can be created by using short-term energy storage and a power inverter, and a suitable control mechanism. The VSG control mimics the dynamics of the rotation SG and enhances the power system's stability. This paper presents an overview of various topologies on virtual inertia, VSG concepts, control techniques, and VSG applications. Finally, the VSG challenges and future research will be discussed.

Topological morphogenesis of neuroepithelial organoids

Animal organs exhibit complex topologies involving cavities and tubular networks, which underlie their form and function1–3. However, how topology emerges during the development of organ shape, or morphogenesis, remains elusive. Here we combine tissue reconstitution and quantitative microscopy to show that tissue topology and shape is governed by two distinct modes of topological transitions4,5. One mode involves the fusion of two separate epithelia and the other involves the fusion of two ends of the same epithelium. The morphological space is captured by a single control parameter that can be traced back to the relative rates of the two epithelial fusion modes. Finally, we identify a pharmacologically accessible pathway that regulates the frequency of two modes of epithelial fusion, and demonstrate the control of organoid topology and shape. The physical principles uncovered here provide fundamental insights into the self-organization of complex tissues6.

Region of convergence by parameter sensitivity constrained genetic algorithm-based optimization for coordinated load frequency control in multi-source distributed hybrid power system

The imbalances created by generation and load can indeed result in frequency variations demanding a load frequency control (LFC). The LFC becomes even more complicated with the multi-source distributed hybrid power system (HPS), where designing optimal controller parameters by identifying the region of convergence (RoC) is critical as it guarantees the HPS's stability. Hence, this paper aims to address the frequency regulation (FR) issue in a state-of-the-art modeled multi-source distributed HPS with a coordinated control approach. The modeled HPS includes a reheat thermal power system (RTPS), wind turbine generator (WTG), fuel cell (FC) stack, battery energy storage system (BESS), diesel engine generator (DEG), and various controllers.A novel method called parameter sensitivity algorithm (PSA) is proposed to obtain the RoC of the controller gains and is further optimized using a constrained genetic algorithm (GA). To demonstrate coordinated control effectiveness, a hybrid objective function for optimization is formulated as constrained GA's fitness function using the integral time absolute error (ITAE) and integral absolute error (IAE). Furthermore, a comparative assessment for PI, PID with filter (PIDN), cascaded PI-PD with filter (PIPDN) controller topologies is carried out using error index-based performance metrics to ascertain the preeminence of the hybrid objective function over existing objective functions. The investigation results validate that the suggested optimized controllers provide enhanced FR and are robust to uncertainties. The practical feasibility of the proposed methodology is reinforced using dSPACE hardware in loop testing.

Modelling farm-based electric vehicles on charging systems for power distribution networks with dynamic grid interactions

This paper provides the capability with a control topology for low voltage distribution network to satisfy sudden peak load demand by designing a system. Develop the electric vehicle (EV) farm accumulated based on the charging system for voltage regulation at a distribution node for transmitting power to the grid from EVs by a control vehicle-to-grid operation. Also, this paper concerns with modelling of an EV system with dynamic interaction with grid integrated with major classifications from the state of charge (SOC). In EV farm, four various EV profiles were considered to understand the grid integration and supply the sudden peak load demand. The EV farm integration with the grid was observed by modelling an equivalent system in MATLAB/Simulink.

Dysplastic Erythropoiesis in Stag2 Loss Exhibits Defective Nuclear Condensation and Hemophagocytosis

Chromosomes fold in a hierarchy of increasingly complex structures from nucleosomes to chromosomal territories. Dynamic chromosomal architecture establishes regulatory cues that allow for local reorganization during cellular differentiation. The ring-shaped cohesin complex, composed of SMC1, SMC3, RAD21, and either STAG1 or STAG2, plays a critical role in forming chromatin loops, permitting genomic partitioning, enhancer-promoter interactions, and topological control of gene expression. While both STAG1 and STAG2 play a role in regulating gene expression and genome organization, we and others have defined distinct roles, owing to their differential cellular localization and range of interactions. Given that STAG2 is recurrently mutated in various cancers, including acute myeloid leukemia and myelodysplastic syndrome, understanding the role of STAG2 in gene regulation, hematopoiesis, and tumor suppression could provide novel therapeutic and clinical insights. Prior work by our group has demonstrated that Stag2 deficiency results in altered hematopoietic stem cell (HSC) self-renewal, impaired HSC differentiation, and lineage skewing. In particular, Stag2 deficiency resulted in marked features of myelodysplasia. Here, we demonstrate that STAG2 loss results in erythroid atypia and hemophagocytosis. We observe decreased terminal erythroid maturation via scRNA-seq of Stag2-/- CFU-E (Lineage-cKit+Sca1−CD34−Fcγ−CD105+). To further investigate the mechanistic basis of this impaired maturation, bone marrow from Stag2-/-, Stag2+/-, and Stag2+/+ mice was stained with H&E, where marked nuclear-cytoplasmic dyssynchrony of erythroblasts was noted in a Stag2 dose dependent manner. Additionally, erythrocytes and erythrocyte debris was observed in bone marrow resident macrophages, suggesting the presence of hemophagocytosis (Fig. 1A). Immunohistochemistry (IHC) for Ter119, an erythroid specific protein, showed markedly reduced surface expression of Ter119, which was confirmed via flow cytometry (p < 0.001). In addition to the overall decrease in Ter119+ cells, the remaining IHC staining was concentrated into distinct foci with Stag2 loss. Immunohistochemistry for Iba1 showed an increased number of Iba1+ macrophages (Mφ) in Stag2-/- mice. Colocalization studies by confocal microscopy further validated hemophagocytosis (Fig.1B). To determine if Mφ overactivation was driving hemophagocytosis, Iba1+ Mφ from Stag2+/+ and Stag2-/- mice were stimulated with IL-4, IL-6, IFN-γ, and LPS and no differences observed as a function of Stag2 genotype. As no anemia present in Stag2-/- mice, we assayed serum erythropoietin and identified a significant increase in erythropoietin in Stag2-/- mice (p < 0.05), suggesting compensatory erythropoietic stimulation. Flow cytometric analysis of Stag2+/+ and Stag2-/- bone marrow stained for CD44 showed significant alterations to terminal erythroid differentiation, with an increase in Stage II erythroblasts (p = 0.01) and decreases in Stage IV/V erythroblasts (p = 0.029 and 0.031, respectively). Subsequent ATAC sequencing of sorted Stag2+/+ and Stag2-/- erythroid progenitors showed an overall more relaxed chromatin state and hyperaccessibility with Stag2 loss, suggesting defective nuclear condensation from the earliest stages of erythropoiesis. Preliminary data from STAG2 shRNA knockdown in human CD34+ cells in vitro suggests that STAG2 may impair chromatin condensation and enucleation during terminal erythroid differentiation. Whether the hyperaccessibility observed with STAG2 loss persists through terminal erythroid differentiation is being investigated to determine the mechanism by which STAG2 loss influences defective nuclear condensation and nuclear extrusion during erythroid differentiation. These data suggest that Stag2 loss negatively affects chromatin condensation, resulting in a compensatory erythropoietin secretion and increased hemophagocytosis. These data extend the role of Stag2 from lineage priming to the latest stages of erythropoiesis and define the critical physiologic role of Stag2 in erythropoiesis. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

A hybrid technique for transformer-less grid-tie Hybrid Renewable Energy Source with reduction of common mode leakage current

A hybrid method for transformer-less grid-tie hybrid Renewable Energy Source (HRES), such as photovoltaic (PV) and wind energy system (WES) with minimization of common mode leakage current is proposed in this manuscript. The proposed system is the combined execution of Vascular Invasive Tumor Growth (VSTG) Optimization Algorithm and extreme gradient boosting (XGBOOST) named VSTG-XGBOOST control topology. The main intention of transformerless grid-connected HRES system is “to lessen the leakage current, maximum power point (MPP) extraction and maximal power point tracking (MPPT), the active and reactive power controller, and having the unity power factor. To attain the above-mentioned aims, the following actions have been performed in this proposed work. Two turn-off snapper circuits are inserted parallel to the switches to share the input DC voltage among snubber capacitors. By then, VSTG is used to estimate the optimal gain parameters under various source currents as normal value is used to generate the optimal control signal database offline. Based on the attained dataset, the XGBOOST forecasts the optimal control signals of the grid-connected HRES inverter in the online way. This control technique allows two sources to supply the load separately depending on the availability of the energy sources and keeps common DC voltage constant.

Cascaded Controller for Controlling DC Bus Voltage in Mismatched Input Powers

The lack of uniform production of panels in photovoltaic (PV) systems and snowball effects in fuel cell (FC) systems led us to use a separate dc–dc converter. In addition, in the PV and FC systems, the output voltage is low. Hence, dc–dc boost converters are commonly used in a series connection. Each small unit of a PV or FC operates independently. Therefore, another problem arises in the system that uses the series connection of the converter's output. Owing to the unequal electricity production of the cells, a voltage imbalance occurs at the output terminals. To create voltage balance, a modular structure grounded on a three-level boost converter was investigated. The main objective of this article is to design the control of a modular topology, allowing perfect control of the dc-bus voltage, even with mismatched input powers. The proposed control strategy ensures dynamical properties independent of the operating point, voltage balance, and robust control of the dc output voltage with respect to load perturbations. To ensure the balance of voltages and the control of currents, a sliding mode controller based on indirect synthesis was used. To control the dc–bus voltage, an energy controller is proposed that ensures dynamical performance independent of the operating conditions. The performance in terms of tracking and regulation, as well as its effect on the voltage balance of the output capacitors, was validated through simulations and experimental results. A comparison with a classical proportional integral (PI) approach for controlling the dc-bus voltage was performed.

Dynamical analysis of a discrete-time COVID-19 epidemic model.

In this paper, we explore local dynamics with topological classifications, bifurcation analysis, and chaos control in a discrete-time COVID-19 epidemic model in the interior of . It is explored that for all involved parametric values, discrete-time COVID-19 epidemic model has boundary equilibrium solution and also it has an interior equilibrium solution under definite parametric condition. We have explored the local dynamics with topological classifications about boundary and interior equilibrium solutions of the discrete-time COVID-19 epidemic model by linear stability theory. Further, for the discrete-time COVID-19 epidemic model, existence of periodic points and convergence rate are also investigated. It is also studied the existence of possible bifurcations about boundary and interior equilibrium solutions and proved that there exists no flip bifurcation about boundary equilibrium solution. Moreover, it is proved that about interior equilibrium solution, there exist Hopf and flip bifurcations, and we have studied these bifurcations by utilizing explicit criterion. Moreover, by feedback control strategy, chaos in the discrete COVID-19 epidemic model is also explored. Finally, theoretical results are verified numerically.

A comprehensive evaluation method of DC voltage sag in medium–low voltage DC distribution system

The development of the DC distribution system (DCDS) has attracted increasing attention, due to its technological superiorities in integrating new energy sources and DC power loads more friendly and effectively. In this paper, a comprehensive evaluation method is proposed for the medium–low​ voltage DCDS to handle the voltage sag assessment problem. Firstly, the topology structure and control strategy of the DCDS are stated, and the pragmatic characteristics of DC voltage sag on the medium-voltage and low-voltage sides based on the dual active bridge (DAB) converter are analyzed. Then, considering the difference in the evaluation indexes of the low-voltage and medium-voltage sides of the DCDS, a comprehensive evaluation system is established. Further, the analytic hierarchy process (AHP) and criteria importance through intercriteria correlation (CRITIC) weighting method are applied to achieve comprehensive weighting, and the TOPSIS model is used to describe the severity of DC voltage sag. Using MATLAB, a 10 kV/ 750 V DCDS with the DAB is built, and comparative assessments are performed. The results show that the proposed method can reasonably evaluate the DC voltage sag of the low-voltage and medium-voltage sides. Compared to the evaluation schemes based on the single index, the proposed method can more effectively reflect the waveform features of the DC voltage sag, and it is very appropriate for the voltage dip evaluation of the medium–low voltage DCDS.

Dynamic metal patterns of wrinkles based on photosensitive layers

Regulating metal surfaces with micro-/nanoscale structures is of great significance for both material science and potential applications. However, the intrinsic properties of metals, such as fixed isotropic moduli and inflexible structures, in a sense present major limitations in developing next-generation smart patterned surfaces. In this work, a facile and general patterning strategy is proposed to endow insensitive metal surfaces with controllable spontaneous topologies and dynamic performance by exquisitely introducing an essential photosensitive interlayer. The arresting anthracene-containing photocrosslinking interlayer can selectively predetermine the anisotropic property of compliant bilayers without damaging metals’ homogeneous properties, and realize a changeable stiff/soft layer. Furthermore, the mechanical transition mechanism of the self-adaptive wrinkling modes in metal-based trilayer systems is revealed to pave the pathway for regulating functional wrinkled metal surfaces. This photodriven metal patterning strategy can promote the development of brand-new methods for tuning the instability of multilayered materials, and be potentially applied in smart optical devices with dynamic reflectance, including light gratings and “magic” mirrors.