Topological Type Research Articles

MFSE-based two-scale concurrent topology optimization with connectable multiple micro materials

The concurrent design of different lattice material microstructures and their corresponding macro-scale distributions has great potential in achieving both lightweight and desired multiphysical performances. In such design problems, the lattice microstructures are usually separately optimized on the basis of the homogenization method, and the possibly poor connectivity between them is a key factor that severely hinders the fabrication and application of optimized two-scale structures. To handle the microstructure connectivity issue, this paper proposes a novel microstructure connectable strategy to bridge the gap between the two-scale and the full-scale model using the material-field series expansion (MFSE) method. Assuming different lattice material types in several pre-defined macro-scale regions, describe all types of microstructural topology with different portions of one material field function and update them simultaneously during the optimization process. Benefits from the material field definition with spatial correlation, the microstructures are well-connected without requiring additional constraints in the topology optimization model. The energy-based homogenization method is utilized for bridging the two-scale with different microstructures, while a decoupled sensitivities analysis for the microscale is employed to enhance the computation efficiency. Additionally, the proposed method significantly reduces the dimension of design variables, resulting in lower optimizer spending. The effectiveness and efficiency of the proposed method are demonstrated by several benchmark two-scale problems. Compared to density-based connectable methods, the proposed framework is easy to implement and reduces computational time by an order of magnitude in the 2D case.

Automatic Containment of Field Exposure for Roadway Wireless Electric Vehicle Charger

Inductive power transfer (IPT) has found application prospect in dynamic wireless electric vehicle (EV) charging as it can avoid the constraints of physical connection. With the commonly-used LCC compensation, the ground-assembled transmitter coil is always excited by a fixed standby current even if there is no receiver coil coverage. As for dynamic wireless power transfer (DWPT) systems, even without EV charging, the underground transmitter coils typically remain activated at full power output to wait for the receivers in most cases, resulting in huge standby current and magnetic exposure safety concerns. In this paper, we proposed a method for automatic containment of field exposure caused by standby current in the transmitter coil of wireless chargers, which applies LCC compensation networks requiring only primary-side control with the elimination of wireless feedback communication and extra detection. The wireless chargers can be automatically deactivated once EVs depart, as well as automatically activated once detecting the presence of EVs. Also, its excellent interoperability for different loads and types of compensation topology has been well analyzed and then verified. Moreover, experiments demonstrate that the magnetic field exposure is merely 11.66% of the ICNIRP 2010 standard exposure limit with proposed modulation, which is suppressed by 94.64% than before.

Curriculum Based Reinforcement Learning of Grid Topology Controllers to Prevent Thermal Cascading

This paper describes how domain knowledge of power system operators can be integrated into reinforcement learning (RL) frameworks to effectively learn agents that control the grid's topology to prevent thermal cascading. Typical RL-based topology controllers fail to perform well due to the large search/optimization space. Here, we propose an actor-critic-based agent to address the problem's combinatorial nature and train the agent using the RL environment developed by RTE, the French TSO. To address the challenge of the large optimization space, a curriculum-based approach with reward tuning is incorporated into the training procedure by modifying the environment using network physics for enhanced agent learning. Further, a parallel training approach on multiple scenarios is employed to avoid biasing the agent to a few scenarios and make it robust to the natural variability in grid operations. Without these modifications to the training procedure, the RL agent failed for most test scenarios, illustrating the importance of properly integrating domain knowledge of physical systems for real-world RL learning. The agent was tested by RTE for the 2019 learning to run the power network challenge and was awarded the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2^{nd}$</tex-math></inline-formula> place in accuracy and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1^{st}$</tex-math></inline-formula> place in speed. The developed code is open-sourced for public use. Analysis of a simple system proves the enhancement in training RL-agents using the curriculum.

Non-symplectic automorphisms of order multiple of seven on K3 surfaces

In this paper we present a complete classification of non-symplectic automorphisms of K3 surfaces whose order is a multiple of seven by describing the topological type of their fixed locus. In the case of purely non-symplectic automorphisms, we provide new results for order 14 and alternative proofs for orders 21, 28 and 42, so that we can unify in the same paper the results on these automorphisms. For each of these orders we also consider not purely non-symplectic automorphisms and obtain a complete characterization of their fixed loci. Several results of our paper were obtained independently in the recent paper [12] by Brandhorst and Hofmann, but the methods used in the two papers are completely different.

Modeling and simulation of extra high voltage magnetically controlled shunt reactor based on PSCAD

For the two typical topologies of the extra high voltage magnetically controlled shunt reactor (MCSR), this study introduces its specific wiring methods and working principles. It conducts an analysis of the change characteristics and response characteristics of the core magnetic flux under different wiring modes of the controlled shunt reactor body. Based on PSCAD, two typical structures are used to model the body of the first 500 kV MCSR put into operation in a provincial power grid and perform steady-state and dynamic simulations. The results of field experiments are compared and analyzed. The winding connection mode of the device’s body electromagnetic transient model is determined, which lays a foundation for the follow-up research.

Evaluating Efficiency of Connected and Autonomous Vehicles with Different Communication Topologies

Connected and autonomous vehicles (CAV) employ vehicle-to-vehicle communications to safely drive in a platoon with short inter-vehicle distances, which can improve traffic throughput and reduce fuel consumption. With the development of wireless communication technology, more and more information can be used for vehicle controllers. However, is more information better? In this paper, a fuel economy-based performance evaluation index is established for evaluating the efficiency of CAVs driving in a platoon with different communication topologies. Four typical communication topologies that describe the CAV with different amounts of information are studied by the linear controller. The differential evolution algorithm is used to solve the parameters. Due to the increase in information, more control parameters need to be computed, and it is hard to find an optimal solution. So, the simulation results show that CAV with more information did not obtain a better fuel economy.

Objects generated by an arbitrary natural number. Part 4: New aspects

The set $\underline{SET}(n)$, generated by an arbitrary natural number $n$, was defined in [3]. There, and in [5,6], some arithmetic functions and arithmetic operators of a modal and topological types are defined over the elements of $\underline{SET}(n)$. Here, over the elements of $\underline{SET}(n)$ new arithmetic functions are defined and some of their basic properties are studied. Two standard modal topological structures over $\underline{SET}(n)$ are described. Perspectives for future research are discussed.

High Order Harmonic Pass Band Suppression in Microstrip Filter

It is very well understood that filters are backbone of communication system as they are employed in each stage of system design and the key parameters which indicates their performance and suitability to desired application are insertion loss, return loss, group delay etc. Apart from them a very important factor namely high order harmonic pass band which becomes very critical when input of the filter consists of multiple harmonic signal within it and creates interference to succeeding stages of the system. In order to achieve clean frequency spectrum in stop band frequency region, there is need of suppressing the high order harmonic spurious pass bands. In this research work additional microstrip patterns are formed at input/output of the filter schematic to achieve the required goal. In this article concept of the novel technique to eliminate or suppress the high order harmonics is detailed and same is implemented on hairpin type of filter topology.

Computational Exploration of Multistable Elastic Knots

We present an algorithmic approach to discover, study, and design multistable elastic knots. Elastic knots are physical realizations of closed curves embedded in 3-space. When endowed with the material thickness and bending resistance of a physical wire, these knots settle into equilibrium states that balance the forces induced by elastic deformation and self-contacts of the wire. In general, elastic knots can have many distinct equilibrium states, i.e. they are multistable mechanical systems. We propose a computational pipeline that combines randomized spatial sampling and physics simulation to efficiently find stable equilibrium states of elastic knots. Leveraging results from knot theory, we run our pipeline on thousands of different topological knot types to create an extensive data set of multistable knots. By applying a series of filters to this data, we discover new transformable knots with interesting geometric and physical properties. A further analysis across knot types reveals geometric and topological patterns, yielding constructive principles that generalize beyond the currently tabulated knot types. We show how multistable elastic knots can be used to design novel deployable structures and engaging recreational puzzles. Several physical prototypes at different scales highlight these applications and validate our simulation.

Zinc(II) complexes of 3,5-bis(4-pyridyl)-1H-1,2,4-triazole: Synthesis, the role of counter-anions in the formation of a type of crystal structure, and luminescence properties

Four Zinc(II) coordination compounds, i.e. [Zn(4bpt)(piv)]n∙1.5nDMSO∙2nH2O (1, 4Hbpt – 3,5-bis(4-pyridyl)-1,2,4-triazole, piv – pivalate-anion), [Zn2(4bpt)2Br2(H2O)]n∙∙3nDMF∙3nH2O (2) and [Zn(4Hbpt)X2]n∙2nDMF (X = Cl (3), Br (4)) have been synthesized and characterized by elemental and thermal analysis, IR spectroscopy and single-crystal X-ray diffraction methods. Structural analysis demonstrated that the influence of counter anions plays an important role in determining the resultant structure: 3D networks for 1 and 2 with topological type of srs and 3,4-c respectively, and chain polymers for 3 and 4. The photoluminescent properties and mechanisms, studied by means of solid state absorption, excitation/emission spectra, time-resolved lifetime techniques, indicate that the emissions of both compounds originate from a combination of exciplex and charge-transfer complex. Interestingly, compound 2 exhibit excitation-dependent emissions, which can be used to fine-tune their emission wavelengths.

Effect of Crosshead Speed and Volume Ratio on Compressive Mechanical Properties of Mono- and Double-Gyroid Structures Made of Inconel 718.

The current development of additive technologies brings not only new possibilities but also new challenges. One of them is the use of regular cellular materials in various components and constructions so that they fully utilize the potential of porous structures and their advantages related to weight reduction and material-saving while maintaining the required safety and operational reliability of devices containing such components. It is therefore very important to know the properties of such materials and their behavior under different types of loads. The article deals with the investigation of the mechanical properties of porous structures made by the Direct Metal Laser Sintering (DMLS) of Inconel 718. Two types of basic cell topology, mono-structure Gyroid (G) and double-structure Gyroid + Gyroid (GG), with material volume ratios of 10, 15 and 20 %, were studied within our research to compare their properties under quasi-static compressive loading. The testing procedure was performed at ambient temperature with a servo-hydraulic testing machine at three different crosshead testing speeds. The recorded data were processed, while the stress-strain curves were plotted, and Young's modulus, the yield strength Re0.2, and the stress at the first peak of the local maximum σLocMax were identified. The results showed the best behavior under compression load among the studied structures displayed by mono-structure Gyroid at 10 %. At the same time, it can be concluded that the wall thickness of the structure plays an important role in the compressive properties but on the other hand, crosshead speed doesn´t influence results significantly.

A genetic‐algorithm‐based synthesis of microwave integrated distributed amplifiers

AbstractThis article presents a genetic algorithm‐based technique for microwave integrated distributed amplifier synthesis. To speed‐up synthesis, only linear characteristics are used in the goal function. The technique uses MMIC foundry process design kit models providing manufacturing‐ready schematics to be found. The models from the process design kit are presented as S‐parameters again to enhance algorithm performance. The technique allows searching among most of the existing schematics of the microwave distributed amplifier but is not limited to typical topologies. The section number is theoretically unlimited and makes it possible to find principally new circuit topology. The synthesis shortens and simplifies the distributed amplifier design time. Experimental validation of the technique is carried out by synthesizing the broadband driver stage for the 20–30 GHz buffer amplifier. The technique produces several amplifier topologies meeting the requirements. The most appropriate circuit was manufactured using a commercial 0.25 μm GaAs pHEMT process. The manufactured buffer amplifier demonstrates a gain of 10 dB and 20 dBm output power at a 1 dB compression point.

Three Ca(II)-Dy(III) heterometallic coordination polymers with different topologies and different water clusters: Synthesis and properties

Three new heterometallic polymers [DyL4Ca2(H2O)2.5(C2H5OH)0.5]·Him·H2O (1), [Dy2L6Ca3(H2O)12]·6H2O (2) and [Dy0.67L2Ca(H2O)2]·4H2O (3) (H2L = 4-chloropyridine-2,6-dicarboxylic acid, im = imidazole) were prepared under solvothermal conditions. The single crystal determination showed that polymers 1 and 3 are two-dimensional structures and polymer 2 is three-dimensional structure. It was found that different types of water clusters were present in these three polymers. They exhibit different topologies with the topological symbols {43}2{46·66·83}, {42·6·123}2{42·6}2 and {63}, where polymer 2 is a new topological type. A series of characterizations, such as XRD, IR, TGA, and solid-state fluorescence, were carried out on these three crystalline materials. They all show characteristic emission spectra of Dy(III) ions. Their quantum yields Фtotal are 4.01% (1), 2.25% (2), 2.88% (3), respectively.

A Family of Symmetrical Bipolar Output Converters Based on Voltage-Multiplying Rectifiers for Interfacing Renewable Energy With Bipolar DC Microgrid

The bipolar dc microgrid system is considered a greatly promising solution to interface various renewable energy sources and emerging loads due to its advantages in efficiency and reliability. However, pole voltage imbalance and lack of superior bipolar power conversion topologies limit the development and application of bipolar DC microgrid systems. In this context, this paper proposes a family of multi-port converters based on voltage-multiplying rectifiers to achieve symmetrical bipolar output voltage and power conversion between renewable energy sources and bipolar buses. In the proposed topologies, single-stage power conversion, without voltage balance feedback control, and a low number of components are obtained. Furthermore, the bulky balancing inductor is eliminated to improve conversion efficiency and reduce the volume of the system. Moreover, the higher voltage gain, smaller input current ripple, and lower voltage stress of semiconductor devices make it ideal for interfacing renewable energy sources with bipolar DC microgrids. The derivation method for the proposed topology family is first introduced. Then, a typical topology in the proposed converter family is analyzed in detail as an example, including the operation principle, steady-state performance, parasitic parameter effects, design considerations, efficiency analysis, control method, loop designing, etc. Finally, a 1-kW prototype is developed and tested to verify the performance of the proposed converter.

STRUCTURAL CLASSES WITH A SOLE BEARING CONTACT OF CHAINED STRUCTURAL UNITS

Structural classes of the crystal structures consisting of mutually parallel chains of structural units (polymers) and constructed due to the sole bearing contact between polymer chains have been derived. In total, 43 structure classes have been found. Nets of bearing contacts in these classes belong to topological types sql, hxl, hcb, kgm, kgd, 2,4L2 and some other types of nets with doubly coordinated vertices. Examples of crystal structures of inorganic and organic polymers are presented.

Observation of modes reversion by encircling exceptional points in high-order non-hermitian system

The special properties of non-trivial topological structures usually come from a so-called edge mode which emerges in the band gap after the band inversion. The topological winding number of exceptional points (EPs) in non-Hermitian physical systems can be regarded as another type of topology. In photonics, the topological properties of EPs have been observed widely both in adiabatic and non-adiabatic second-order non-Hermitian systems. Here, we construct a higher-order non-Hermitian system with meta-atoms, including two independent second-order EPs. By circling EPs in different paths in the Riemann parameter surface, we observe extraordinary modes of reversion and repulsion, which is quite different from the conventional second-order EP systems. We propose a theoretical model of three-resonance non-Hermitian system and verify experimentally the mode reversion by encircling exceptional points in the microwave band, which may pave a new way for studying the topological physical mechanism of non-Hermitian systems, and provide a practical experimental system for its application.

Modified toric code models with flux attachment from Hopf algebra gauge theory

Kitaev’s toric code is constructed using a finite gauge group from gauge theory. Such gauge theories can be extended with the gauge group generalized to any finite-dimensional semisimple Hopf algebra. This also leads to extensions of the toric code. Here we consider the simple case where the gauge group is unchanged but furnished with a non-trivial quasitriangular structure (R-matrix), which modifies the construction of the gauge theory. This leads to some interesting phenomena; for example, the space of functions on the group becomes a non-commutative algebra. We also obtain simple Hamiltonian models generalizing the toric code, which are of the same overall topological type as the toric code, except that the various species of particles created by string operators in the model are permuted in a way that depends on the R-matrix. In the case of gauge theory, we find that the introduction of a non-trivial R-matrix amounts to flux attachment.

Characterizing compact sets in Lp-spaces and its application

In this paper, we give a characterization of compact sets in Lp-spaces on metric measure spaces, which is a generalization of the Kolmogorov-Riesz theorem. Using the criterion, we investigate the topological type of the space consisting of Lipschitz maps with bounded supports.

Arithmetic Study about Efficiency in Network Topologies for Data Centers

Data centers are getting more and more attention due the rapid increase of IoT deployments, which may result in the implementation of smaller facilities being closer to the end users as well as larger facilities up in the cloud. In this paper, an arithmetic study has been carried out in order to measure a coefficient related to both the average number of hops among nodes and the average number of links among devices for a range of typical network topologies fit for data centers. Such topologies are either tree-like or graph-like designs, where this coefficient provides a balance between performance and simplicity, resulting in lower values in the coefficient accounting for a better compromise between both factors in redundant architectures. The motivation of this contribution is to craft a coefficient that is easy to calculate by applying simple arithmetic operations. This coefficient can be seen as another tool to compare network topologies in data centers that could act as a tie-breaker so as to select a given design when other parameters offer contradictory results.

Influence of core topology on blast mitigation application of multi-layered honeycomb core sandwich panel

In the past years, the aluminium honeycomb core sandwich panel has emerged as a promising blast mitigation solution owing to its high energy absorbing capacity under impulsive loading. To enhance its performance against the blast load, it is important to understand the mechanical behaviour of honeycomb core sandwich panel with varying core configurations. The present study investigates the difference in load mitigation behaviour of sandwich panel under blast loading with different honeycomb core topologies. Three types of honeycomb core topology i.e., square, circular, and hexagonal are considered in the present study. The performance of the sandwich panels under blast loading is compared for two criteria i.e., constant mass (or aerial density) and constant cell size. The influence of a multi-layered core along with the intermediate sheets on the blast resistance of sandwich panel is further examined under blast load. It is observed that the multi-layered core and intermediate sheets not only strengthen the sandwich panel but also make it significantly stronger under the blast loading in comparison to the single layer sandwich panel. The role of intermediate sheets in energy dissipation is observed to be insignificant in multi-layered sandwich panel for the parameters considered in this investigation. Further, it is observed that the difference in energy dissipated by front face sheet and back face sheet is increased with increase in the number of layers of cores.