Topology Control Research Articles

Incorporating Highly Anisotropic Four-Coordinate Co(II) Ions within One-Dimensional Coordination Chains

Low-coordinate metallic ions have been well recognized for constructing good-performance single ion magnets (SIMs) due to their enhanced magnetic anisotropy; however, the incorporation of such specific ions into coordination polymers is still challenging. Here, we reported two new CoII coordination polymers, namely [Co(pdms)(bpe)]n (1) and {[Co(pdms)(tpb)]·H2O·tpb}n (2) (H2pdms = 1,2-bis(methanesulfonamido)benzene, bpe = 1,2-di(4-pyridyl)ethane, tpb = 1,2,4,5-tetra(4-pyridyl)benzene). Single crystal X-ray diffraction experiments indicated that the CoII centers in both 1 and 2 display a distorted tetrahedral geometry with quasi C2v symmetry and are linked into a one-dimensional (1D) zig-zag chain via the ditopic bridging ligand of bpe in 1 while a ribbon chain via the tetradentate linker of tpb in 2. Magnetic studies revealed the easy-axis magnetic anisotropy of the CoII ions with different zero-field splitting D of −19 cm–1 (1) and −33 cm–1 (2), likely due to the distinct changes in the Npy–Co–Npy bite angles (100.20° (1) vs. 93.90° (2)). Moreover, slow magnetic relaxation proceeded via different relaxation mechanisms under applied dc fields was observed, giving an effective energy barrier (Ueff) of 69.6 K for 1 and 76.6 K for 2, respectively. The ab initio calculations on both the polymers further confirmed the sign and magnitude of the ZFS parameters and nicely reproduced the experimental results. Our study demonstrated a great potential for applying the well-studied and highly anisotropic 4-coordinate metal ions within a coordination polymer, opening a viable means to tuning magnetic anisotropy via topological control.

A Torque-Enhanced Magnetic-Geared Machine with Dual-Series-Winding and Its Design Approach for Electric Vehicle Powertrain

Magnetic gear and magnetic-geared machine (MGM) are the potential solutions in electric vehicles (EVs) powertrains for inherent high efficiency and mechanical simplification. However, the torque density issue of the MGM greatly limits its industrial application. To enhance the torque performance of the MGM, a torque-enhanced magnetic-geared machine with dual-series-winding and its design approach are proposed. The key merits of the proposed design are to achieve a high space utilization with a dual-winding design, with no additional control topologies and power converters required. The auxiliary winding is supplemented and integrated with modulation rings. The relative position of the stator and armature winding are designed and rotated compared to the modulation rings with auxiliary winding, to ensure the auxiliary winding shares the excitation with the armature winding. Accordingly, simplifying the external control topologies. With the proposed design, the torque of the MGM can be significantly enhanced with a single three-phase driving. Theoretical analysis, parameters optimization and electromagnetic verification are given, demonstrating that the proposed machine can achieve an efficiency of 93.2%, generate a torque of 107.2 N·m, and reach a torque density of 10.81 N·m/kg.

A novel method combining VAT photopolymerization and casting for the fabrication of biodegradable Zn–1Mg scaffolds with triply periodic minimal surface

Zinc alloy porous scaffolds are expected to be the next generation of degradable orthopedic implants attributed to their suitable degradation rate. However, a few studies have thoroughly investigated its applicable preparation method and functionality as an orthopedic implant. This study fabricated Zn–1Mg porous scaffolds with triply periodic minimal surface (TPMS) structure by a novel method combining VAT photopolymerization and casting. As-built porous scaffolds displayed fully connected pore structures with controllable topology. The manufacturability, mechanical properties, corrosion behaviors, biocompatibility, and antimicrobial performance of the bioscaffolds with pore sizes of 650 μm, 800 μm, and 1040 μm were investigated, and then compared and discussed with each other. In simulations, the mechanical behaviors of porous scaffolds exhibited the same tendency as the experiments. In addition, the mechanical properties of porous scaffolds as a function of degradation time were studied through a 90-day immersion experiment, which can provide a new option for analyzing the mechanical properties of porous scaffolds implanted in vivo. The G06 scaffold with lower pore size presented better mechanical properties before and after degradation compared with G10. The G06 scaffold with the pore size of 650 μm revealed good biocompatibility and antibacterial properties, which makes it possible to be one of the candidates for orthopedic implants.

Dual, Three-Level, Quasi-Z-Source, Indirect Matrix Converter for Motors With Open-Ended Windings

In this paper, a novel variable-voltage, variable-frequency, dual, three-level, quasi-Z-source, indirect matrix converter topology is proposed, including a detailed description of a modulation method and a control strategy for three-phase motors with open-ended windings. The proposed power drive system (PDS) supports bidirectional power flow and has a combined control of DC-link voltage and output AC voltage frequency. Experimentally validation was performed on a 4-kW PDS. For a given supply voltage amplitude and the same power switch voltage rating in the DC/AC converter, the proposed PDS can double the voltage output gain, thus being an interesting solution for high-power applications with motors designed for higher voltages. The proposed PDS topology, modulation method and motor control strategy can reduce the common-mode component, low-order harmonic content, peak values and d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> of the motor phase voltage, ultimately leading to lower winding insulation voltage stress at low-speed, low-voltage operation, lower harmonic losses in the motor, and ride-through capability over voltage sags in the mains, which are important advantages.

An Overview of High-efficiency Synchronous Reluctance Machines

In recent years the synchronous reluctance machines (SynRMs) have received much attention. They have some good features such as high torque density, high reliability and low cost. This paper aims to give an overview of SynRMs with particular emphasis on the history, research status and industrial application. Besides, concept and basic operating principles of such machines are also described. Moreover, some hot spots of the research on the SynRMs are introduced. Several methods to improve the average torque and reduce torque ripple of the SynRMs in the past literatures are presented including topology design and control strategies. An overview of the methods from different aspects to realize high efficiency for the SynRMs is given which contain rotor optimization, winding configuration, material improvement, control schemes and so on. Some approaches suitable for high speed application are also introduced. It can be seen that the SynRMs have broad development prospects and great potential in industrial application.

Control of Cuk-Based Microinverter Topology with Energy Storage for Residential PV Applications

This paper proposes a modular inverter based on Cuk converters for solar photovoltaic (PV) systems to mitigate the voltage and current mismatch issue at the PV module level. The proposed modular Cuk inverter (MCI) is formed by connecting several low-voltage (LV) microinverters (MIs) in series and linking their output sides to the distribution network. This architecture does not require a central inverter, and hence, it eliminates the need for large dc-link intermediate capacitors. The proposed MCI provides more controllability over the PV system by having a decentralized structure. The MCI will improve the PV system efficiency by reducing the voltage and current stresses in the MIs and will enable better voltage regulation due to the provided controllability. Since the proposed MI topology is based on the Cuk converter, it offers continuous input and output currents that will reduce the required filtering capacitance and will provide a wide range of voltage regulation for either supplying the loads or charging the storage batteries. The paper presents the associated control scheme for the proposed MCI that employs two controlling loops. The input loop at the PV side is designed and tuned to eliminate the ripples from the input current, while the outer loop at the grid side will control the output ac current and hence the MCI power. Computer simulations are presented using MATLAB/SIMULINK software to examine the validity of the suggested inverter for distributed generation PV residential applications. A scaled-down experimental prototype controlled by TMS320F28335 DSP was built and used to validate the mathematical analyses and simulation results.

Duo: A High-Throughput Reconfigurable Datacenter Network Using Local Routing and Control

The performance of many cloud-based applications critically depends on the capacity of the underlying datacenter network. A particularly innovative approach to improve the throughput in datacenters is enabled by emerging optical technologies, which allow to dynamically adjust the physical network topology, both in an oblivious or demand-aware manner. However, such topology engineering, i.e., the operation and control of dynamic datacenter networks, is considered complex and currently comes with restrictions and overheads. We present Duo, a novel demand-aware reconfigurable rack-to-rack datacenter network design realized with a simple and efficient control plane. Duo is based on the well-known de Bruijn topology (implemented using a small number of optical circuit switches) and the key observation that this topology can be enhanced using dynamic (''opportunistic'') links between its nodes. In contrast to previous systems, Duo has several desired features: i) It makes effective use of the network capacity by supporting integrated and multi-hop routing (paths that combine both static and dynamic links). ii) It uses a work-conserving queue scheduling which enables out-of-the-box TCP support. iii) Duo employs greedy routing that is implemented using standard IP longest prefix match with small forwarding tables. And iv) during topological reconfigurations, routing tables require only local updates, making this approach ideal for dynamic networks. We evaluate Duo in end-to-end packet-level simulations, comparing it to the state-of-the-art static and dynamic networks designs. We show that Duo provides higher throughput, shorter paths, lower flow completion times for high priority flows, and minimal packet reordering, all using existing network and transport layer protocols. We also report on a proof-of-concept implementation of Duo's control and data plane.

Topological quantum criticality of the disordered Chern insulator

We consider the two-dimensional topological Chern insulator in the presence of static disorder. Generic quantum states in this system are Anderson localized. However, topology requires the presence of a subset of critical states, with diverging localization length (the Chern insulator analog of the ‘center of the Landau band states’ of the quantum Hall insulator.) We discuss geometric criteria for the identification of these states at weak disorder, and their extension into the regime of strong disorder by analytical methods. In this way, we chart a critical surface embedded in a phase space spanned by energy, topological control parameter, and disorder strength. Our analytical predictions are supplemented by a numerical analysis of the position of the critical states, and their multifractal properties.

Engineering austenite/martensite mesostructured materials by controlled localised laser treatments in a Fe–Ni–C alloy

Localised laser treatments enable the creation of sophisticated austenite/martensite mesostructures in Fe–Ni–C steel with the potential of achieving enhanced mechanical performance. The control of phase topology is essential to modify the properties of these structures on demand and requires a profound understanding of the effect of the processing parameters on the development of the different phases upon the application of laser treatment. In this work, the microstructure evolution under exceptional gradients in temperature and heating rates is thoroughly investigated. The extent of the laser-affected zone and the heat input were tailored by varying laser parameters and specimen thickness, based on a model that considers transient material properties and the coupling between temperature and microstructure. The predicted temperature fields resulted in a complex interplay between martensite to austenite phase transformation and martensite tempering. Considering the high heating rates of up to 25000 K/s and the observed microstructures, it is suggested that austenite was formed by a pseudo-displacive mechanism and subsequently fully recrystallised in the zones most directly affected by the laser heat source. A smooth strength transition from austenite to martensite, affected by the laser parameters, could be exploited for more effective deformation mechanisms and improved material mechanical properties.

Anti-Dissipative Strategies toward More Efficient Solar Energy Conversion.

In natural and artificial photosynthesis, light absorption and catalysis are separate processes linked together by exergonic electron transfer. This leads to free energy losses between the initial excited state, formed after light absorption, and the active catalyst formed after the electron transfer cascade. Additional deleterious processes, such as internal conversion (IC) and vibrational relaxation (VR), also dissipate as much as 20-30% of the absorbed photon energy. Minimization of these energy losses, a holy grail in solar energy conversion and solar fuel production, is a challenging task because excited states are usually strongly coupled which results in negligible kinetic barriers and very fast dissipation. Here, we show that topological control of oligomeric {Ru(bpy)3} chromophores resulted in small excited-state electronic couplings, leading to activation barriers for IC by means of inter-ligand electron transfer of around 2000 cm-1 and effectively slowing down dissipation. Two types of excited states are populated upon visible light excitation, that is, a bridging-ligand centered metal-to-ligand charge transfer [MLCT(Lm)], and a 2,2'-bipyridine-centered MLCT [MLCT(bpy)], which lies 800-1400 cm-1 higher in energy. As a proof-of-concept, bimolecular electron transfer with tri-tolylamine (TTA) as electron donor was performed, which mimics catalyst activation by sacrificial electron donors in typical photocatalytic schemes. Both excited states were efficiently quenched by TTA. Hence, this novel strategy allows to trap higher energy excited states before IC and VR set in, saving between 100 and 170 meV. Furthermore, transient absorption spectroscopy suggests that electron transfer reactions with TTA produced the corresponding Lm•--centered and bpy•--centered reduced photosensitizers, which involve different reducing abilities, that is, -0.79 and -0.93 V versus NHE for Lm•- and bpy•-, respectively. Thus, this approach probably leads in fine to a 140 meV more potent reductant for energy conversion schemes and solar fuel production. These results lay the first stone for anti-dissipative energy conversion schemes which, in bimolecular electron transfer reactions, harness the excess energy saved by controlling dissipative conversion pathways.

An adaptive fuzzy logic control technique for LVRT enhancement of a grid-integrated DFIG-based wind energy conversion system

The fast improvement of wind energy conversion technology with optimization algorithms has recently received a lot of attention. However, their slow convergence speed, huge computational load, and low efficiency are the main drawbacks and to improve these disadvantages, a new adaptive fuzzy logic controller strategy is proposed to enhance the low voltage ride-through of the grid-connected doubly fed induction generator during severe grid faults. The rotor side converter and the grid side converter are controlled using an adaptive fuzzy logic controller topology under cascaded structure to improve the performance. The novel application of the ‘generalized variable step-size diffusion continuous mixed p-norm’ adaptive filtering algorithm is proposed to modify the calibrating factors of the fuzzy logic controllers at a rapid convergence speed with low normalized misalignment error. The proposed adaptive algorithm-based fuzzy logic controller has a better low voltage ride-through improvement capability than that of using the particle swarm optimization-based proportional-integral controller during severe grid disturbances. The convergence speed of the proposed adaptive filtering algorithm is compared to that of existing algorithms such as least mean fourth, least mean square, and continue mixed p-norm algorithms. In addition, a comparison is also made with different common optimization methods. The field-programmable gate array-based real-time experimental results are presented to validate the proposed adaptive control topology.

Electrical Manipulation of Topological Phases in a Quantum Anomalous Hall Insulator.

Quantum anomalous Hall phases arising from the inverted band topology in magnetically doped topological insulators have emerged as an important subject of research for quantization at zero magnetic fields. Though necessary for practical implementation, sophisticated electrical control of molecular beam epitaxy (MBE)-grown quantum anomalous Hall matter have been stymied by growth and fabrication challenges. Here, a novel procedure is demonstrated, employing a combination of thin-film deposition and 2Dmaterial stacking techniques, to create dual-gated devices of the MBE-grown quantum anomalous Hall insulator, Cr-doped (Bi,Sb)2 Te3 . In these devices, orthogonal control over the field-induced charge density and the electric displacement field is demonstrated. A thorough examination of material responses to tuning along each control axis is presented, realizing magnetic property control along the former and a novel capability to manipulate the surface exchange gap along the latter. Through electrically addressing the exchange gap, the capabilities to either strengthen the quantum anomalous Hall state or suppress it entirely and drive a topological phase transition to a trivial state are demonstrated. The experimental result is explained using first principle theoretical calculations, and establishes a practical route for in situ control of quantum anomalous Hall states and topology.

Mission-based PTR triangle for multi-UAV systems flight planning

The Unmanned Aerial Vehicle (UAV) domain, especially the design of UAV cooperative systems, is one of the most important research and applied fields nowadays. The multi-UAV system design is a wealth of research points under the flight planning umbrella, including the design of communication protocols for the Flying Ad-hoc Network (FANET) connecting UAVs, and the inevitable flight design aspects which are the mission planning and path planning. With the fact that topology and routing are the communication design parts most affected by FANET's highly dynamic 3D movement, this paper introduces a design concept for multi-UAV system flight plan that has been named mission-based PTR triangle to indicate the importance of joint optimization of the three design pillars: Path planning, Topology control, and Routing strategy based on mission requirements. These aspects are very interconnected; they determine the UAV positions and relative placement and how the UAVs are connected; any of them can influence or be influenced by the other. They can be regarded as a single process and the trade-off between their parameters controls their influence. In addition, most of the flight planning operations are confined to a PTR triangle its edges represent cross-layer or joint optimization associations, results in different optimization cases to support adaptive optimality suitable to the dynamic nature of FANET, design constraints, and variety in mission scenarios. To this end, this paper sheds light on and reviews the work done on each process and on the mission analysis, including classifications, approaches, and examples of separate and cross-layered optimization. The paper drew a roadmap for flight planning employing the mission-based PTR triangle design approach with a proof-of-concept to the PTR joint optimization ideas. The paper serves as an entry point to the interested researchers in the field of UAV systems design.

Monolayer heterojunction interactive hydrogels for high-freedom 4D shape reconfiguration by two-photon polymerization.

Mimicking natural botanical/zoological systems has revolutionarily inspired four-dimensional (4D) hydrogel robotics, interactive actuators/machines, automatic biomedical devices, and self-adaptive photonics. The controllable high-freedom shape reconfiguration holds the key to satisfying the ever-increasing demands. However, miniaturized biocompatible 4D hydrogels remain rigorously stifled due to current approach/material limits. In this research, we spatiotemporally program micro/nano (μ/n) hydrogels through a heterojunction geometric strategy in femtosecond laser direct writing (fsLDW). Polyethylene incorporated N-isopropylacrylamide as programmable interactive materials here. Dynamic chiral torsion, site-specific mutation, anisotropic deformation, selective structural coloration of hydrogel nanowire, and spontaneous self-repairing as reusable μ/n robotics were identified. Hydrogel-materialized monolayer nanowires operate as the most fundamental block at nanometric accuracy to promise high freedom reconfiguration and high force-to-weight ratio/bending curvature under tight topological control. Taking use of this biomimetic fsLDW, we spatiotemporally constructed several in/out-plane self-driven hydrogel grippers, diverse 2D-to-3D transforming from the same monolayer shape, responsive photonic crystal, and self-clenched fists at μ/n scale. Predictably, the geometry-modulable hydrogels would open new access to massively-reproducible robotics, actuators/sensors for microenvironments, or lab-on-chip devices.

Power Limiting for Battery Manage System based on Event-triggered mechanism with stationary leaders

In this paper, the power constraints of battery energy storage systems(BESS) are considered by designing a cooperative consensus algorithm utilizing Soc containment control. For batteries of different capacities, power constraints and Soc balancing can be achieved under undirected topology and containment control. The distributed event-triggered mechanism is adopted to reduce communication time and consumption of communication resources. In the last section, the effectiveness and stability of the designed control strategy are verified by MATLAB simulation.

Explicit Tunnels and Cavities Control Using SIMP and MMA in Structural Topology Optimization

The topology of a 3D continuum structure is usually characterized by the number of independent connected component and holes in the structure, where the holes include tunnels (through holes) and cavities (interior holes). The number of these features can be measured by the topological invariants of the structure (e.g., Betti numbers and Euler characteristic). The quantitative control of structural topology is important in topology optimization design because of various considerations, including design freedom, manufacturability, structural performance, and manufacturing costs. However, effective control of the structural topology during the topology optimization process remains a challenge, particularly to control the structural tunnels. To simplify the problem, only the number of tunnels (NT) and cavities (NC) of the structure are controlled in this paper. To solve the aforementioned problems, this study calculates the characteristic information of the tunnels and cavities by introducing the tunnel loops of homology theory and fire-burning method (FBM), while proposing a method for quantitative control of the 3D structural tunnels and cavities within the framework of the solid isotropic material with penalty (SIMP) interpolation of the design variable and method of moving asymptotes (MMA) optimization algorithm. The method achieves unilateral constraints over the structural tunnels and cavities by establishing explicit relationships between the element design variables in the structural topology optimization and NT as well as NC in the structure. Numerical examples demonstrate that the proposed method can effectively control the tunnels and cavities of an optimized structure.

Optimal topology control of monitoring sensor network based on physical layer security for smart photovoltaic power system

In order to realize the intelligent management of photovoltaic power generation system, wireless sensor network (WSN) is considered as a promised solution. However, the energy of sensor nodes in WSN is limited and the security is not guaranteed. In order to prolong the service life of WSN and to improve the security of monitoring, this paper comprehensively considers the factors those affect the security and efficiency of WSN, such as transmission power, sensor association and the choice of Cluster Head (CH). Therefore, this paper proposes a joint sensor secure rate and energy efficiency optimization algorithm to obtain the optimal topology and transmission power design. Then, an effective iterative algorithm based on Block Coordinate Descent (BCD) technology is proposed to obtain the optimal solution to minimize the energy consumption of WSN and maximize the secure rate of sensor networks, thus ensuring the security and reliability of monitoring. Sensor association is modeled as a 0–1 multi-knapsack optimization problem. Different complexity methods are implemented to solve this NP-hard problem, and their performance are compared with simulations.

Diffusion-mediated carving of interior topologies of all-natural protein nanoparticles to tailor sustained drug release for effective breast cancer therapy

Proteins are promising base materials for developing drug carriers with efficient blood circulation due to low possibilities of clearance by macrophages. However, such natural biopolymers have highly sophisticated molecular structures, preventing them from being assembled into nano-platforms with manipulable payload release profiles. Here, we report the self-assembly of two natural proteins (milk casein and rice protein) into protein nanoparticles (NPs, ∼150 nm) with tailorable release profiles. Diffusion of plant-derived paclitaxel (PTX)-containing eugenol into the hydrophobic cores of the NPs and subsequent dialysis to remove eugenol from the cores lead to the carving of the NP interiors. With the increase in the mass ratios of casein and rice protein, this process generates all-natural NPs with PTX loaded in their full cavities, semi-full cavities, or solid cores. These NPs can be efficiently uptaken by breast cancer cells and could kill the cancer cells efficiently. PTX in these NPs demonstrates increasingly sustained in vivo release profiles from full cavities, semi-full cavities, to solid cores, gradually extending its pharmacokinetic profiles in blood plasma to favor drug accumulation in breast tumor models. Consequently, the NPs with solid cores completely inhibit tumor growth in vivo, more effectively than those with full and semi-full cavities. Our work opens up a new avenue to the use of diffusion-mediated nanoscale carving in producing biomaterials with controllable interior topologies relevant to drug release profiles.

Ferroelectric higher-order topological insulator in two dimensions

The interplay between ferroelectricity and band topology can give rise to a wide range of both fundamental and applied research. Here, we map out the emergence of nontrivial corner states in two-dimensional ferroelectrics and, remarkably, demonstrate that ferroelectricity and corner states are coupled together by crystallographic symmetry to realize the electric control of higher-order topology. Implementing density functional theory, we identify a series of experimentally synthesized two-dimensional ferroelectrics, such as ${\mathrm{In}}_{2}{\mathrm{Se}}_{3}$, BN, and SnS, as realistic material candidates for the proposed ferroelectric higher-order topological insulators. Our work not only sheds light on traditional ferroelectric materials but also opens an avenue to bridge the higher-order topology and ferroelectricity that provides a nonvolatile handle to manipulate the topology in next-generation electronic devices.

Smart bi-directional inverter control and PV-ESS integration for net zero energy residential buildings

Climate change, sustainable energy goals, and declining investment costs have increased the use of solar photovoltaic generation in residential buildings. According to research, residential buildings account for around 40% of the world&apos;s overall energy use. Most of this utilised energy is derived from fossil fuels, a cause of environmental degradation. The net zero energy building (NZEB) provides a solution to this worrisome pollution. Rooftop solar panels coupled with home-scale storage units are becoming more common in residential areas, and they provide prosumer families with tremendous potential to profit from selling their excess energy to the grid or neighbours. Consequently, the primary purpose of this research paper is to integrate solar (photovoltaic) PV with a household energy storage system (ESS) and the utility grid with NZEB&apos;s electrical load. Power electronic converters are necessary to interface renewable energy sources (RESs) with the grid and the NZEB in order to accomplish this objective. This research work aims to develop an intelligent next-generation bi-directional inverter controller to meet the consumer flexibility demand under different operational constraints. A model predictive current control topology for the inverter has been proposed to achieve the bi-directional power flow. Fourth-order Newton Gregory (N-G), backward differencing polynomial has been used for prediction purposes.