Topological Type Research Articles

Disrupted topological organization of functional brain networks in traumatic axonal injury

Traumatic axonal injury (TAI) may result in the disruption of brain functional networks and is strongly associated with cognitive impairment. However, the neural mechanisms affecting the neurocognitive function after TAI remain to be elucidated. We collected the resting-state functional magnetic resonance imaging data from 28 patients with TAI and 28 matched healthy controls. An automated anatomical labeling atlas was used to construct a functional brain connectome. We utilized a graph theoretical approach to investigate the alterations in global and regional network topologies, and network-based statistics analysis was utilized to localize the connected networks more precisely. The current study revealed that patients with TAI and healthy controls both showed a typical small-world topology of the functional brain networks. However, patients with TAI exhibited a significantly lower local efficiency compared to healthy controls, whereas no significant difference emerged in other small-world properties (Cp, Lp, γ, λ, and σ) and global efficiency. Moreover, patients with TAI exhibited aberrant nodal centralities in some regions, including the frontal lobes, parietal lobes, caudate nucleus, and cerebellum bilaterally, and right olfactory cortex. The network-based statistics results showed alterations in the long-distance functional connections in the subnetwork in patients with TAI, involving these brain regions with significantly altered nodal centralities. These alterations suggest that brain networks of individuals with TAI present aberrant topological attributes that are associated with cognitive impairment, which could be potential biomarkers for predicting cognitive dysfunction and help understanding the neuropathological mechanisms in patients with TAI.

Fatigue constrained topology optimization for the jacket support structure of offshore wind turbine under the dynamic load

This paper proposes a topology optimization method considering fatigue constraints for the jacket support structure of offshore wind turbine. Jacket support structure is an important component and supports the whole wind turbine weight under the dynamic environmental loads, which would induce serious fatigue problems. To obtain the optimal structural layout, the topology optimization method considering fatigue constrained is introduced for the jacket support structure under the dynamic load. The fatigue lifetime is constrained base on the Miner's cumulative damage rule. The design sensitivity of the objective and constraint functions are evaluated analytically, while the equivalent static load approach is applied. Some typical topology optimization problems are introduced to verify the effectiveness of the proposed method, and this method can obtain the appropriate layouts with stable convergence. A case study on the OC4 reference jacket indicates that the method can achieve a reasonable layout structure under the dynamic load, which meets the fatigue constraint. And the final design is reconstructed based on the topology optimization layout. Finally, a lighter jacket structure has good performance on the ultimate bearing capacity, eigenfrequency, and buckling, which is suited for long operation life.

Stability of intermetallic compounds: Geometrical and topological aspects

We have applied a universal geometrical-topological approach to analyze 23507 robust crystal structures of intermetallic compounds, which are deposited in the Inorganic Crystal Structure Database. All the structures were represented as three-periodic nets and arranged into 2551 topological types each of which possesses a unique system of interatomic bonds. For all 104309 topologically different atoms in these structures their environments (local atomic configurations, LACs) were explored within the first and second coordination shells. In total, 5251 topologically distinct types of coordination polyhedra and 21450 types of two-shell LACs were distinguished and deposited into our interactive database system TopCryst. We have found that the local density of the nearest environment of an atom naturally depends on its coordination number (CN) with a maximum at CN = 9. It was shown that LACs at CN ≥ 9 follow the close packing model of hard balls with Slater's atomic radii. At lower CNs, covalent interactions make a significant contribution that results in a decrease of the local density. Resting upon the dependence between the local density and CN we have proposed criteria for the estimation of the geometric instability (disbalance) of both a separate LAC and the whole intermetallic structure. We have revealed that strong geometric disbalance can be caused by errors in the structural data, incorrect description of the crystal structure, non-metallic nature of the chemical bonding or metastability of the crystalline phase. Thus the instability criteria can serve as important indicators of the structure inconsistency that is especially useful for checking crystallographic information on intermetallics or validating the structural models predicted by theoretical methods.

Rigidity of geometric structures

Geometric structures on a manifold M arise from a covering of M by charts with values in a homogeneous space G/H, with chart transitions restrictions of elements of G. If M is aspherical, then such geometric structures are given by a homomorphism of the fundamental group of M into G. Rigidity of such structures means that the conjugacy class of the homomorphism can be reconstructed from topological or geometric information on M. We give an overview of such rigidity results, focusing on topological type and length functions.

Synthesis, crystal structure, and spectroscopic characterization of aminoguanidinium thiosulfate, (CN4H7)2S2O3

AbstractAminoguanidinium thiosulfate, (CN4H7)2S2O3 (1), was prepared via an exchange route from barium thiosulfate and aminoguanidinium sulfate. The new compound is monoclinic, a=12.8344(6) Å, b=13.9134(6) Å, c=6.8757(3) Å, β=115.529(5)°, and crystallizes in a centrosymmetric C2/m space group. Its crystal structure can be considered either as pseudo‐columnar comprised of stacked [CN4H7]+ cations and isolated [S2O3]2− anions which are actively involved in hydrogen bonding, or as H‐bonded bilayers comprised of both [CN4H7]+ and [S2O3]2− of topologic type 3,6L60. The latter ones are H‐bound into a 4,8‐coordinated bearing framework of the type scu.

Loss and reliability analysis of various solid-state battery reconfiguration topologies

The research domain about the selection and design methodology of battery topology structures for energy storage systems, grounded in practical application scenarios, remains significantly underexplored. Furthermore, a substantial gap exists in the current state of research, where the majority of studies lack a comprehensive analysis of losses and reliability associated with reconfigurable battery topology structures. This paper quantitatively analyzes existing MOSFET-based topologies from three key dimensions: losses, costs, and reliability. The study aims to discern the impact of different topology structures and energy storage systems with redundant units on these three dimensions. Subsequently, while ensuring the adaptability of the topology structure, we propose a novel reconfigurable battery system topology suitable for DC microgrids, accompanied by its corresponding control strategy. Through comparative analysis with three typical topology structures, this topology structure has been validated to exhibit certain advantages in terms of losses, reliability, and costs. Lastly, the feasibility of the introduced topology structure is demonstrated through simulation using MATLAB/Simulink. Simulation results indicate that the proposed topology structure not only provides precise control of charge and discharge currents but also demonstrates excellent battery balancing capabilities.

Topologies in distributed machine learning: Comprehensive survey, recommendations and future directions

With the widespread use of distributed machine learning (DML), many IT companies have established networks dedicated to DML. Different communication architectures of DML have different traffic patterns and different requirements on network performance, which is closely related to network topology. However, traditional network topologies usually pursue general goals and are agnostic to the special communication pattern of the applications. The mismatch between network topology and the applications will directly affect the training performance. Although some studies have analyzed the effect of topology on training performance, the topologies and communication architectures involved are not comprehensive, and it is still not known which topology is appropriate for which communication architecture. This survey investigates typical topologies and analyzes whether they meet the requirements of three commonly used communication architectures (i.e., Parameter Server (PS), Tree and Ring architectures) of DML. Specifically, the topology requirements of each communication architecture and two common topology requirements (i.e., high scalability and fault tolerance) for DML are studied firstly. Next, whether these topologies meet the topology requirements is analyzed. Then, this paper discusses potential technologies and approaches to construct the appropriate scheme for each topology requirement, and then presents DMLNet, a novel network topology that suits the three communication architectures. Finally, several potential directions for future research are outlined.

Use of molecular simulation for evaluating adsorption equilibrium of inhalation anaesthetic agents on metal–organic frameworks

AbstractMetal–organic frameworks (MOFs) were studied as alternatives to zeolites and activated carbon for adsorptive removal of wasted inhalation anaesthetic agents (IAA). Monte Carlo simulation was used to predict equilibrium adsorption isotherms of IAA on selected MOFs. Rather than generic forcefields (FFs), the all‐atom FF parameters published by Arcario were used for IAA modelling. Continuous fractional component Monte Carlo (CFCMC) proved crucial for speedy simulation of large molecules. We found that allocating 70% probability to the CFlambdaSwap move gave optimum fits between simulation and experiment. The simulations provided us with an insight into the adsorption mechanisms of IAA in these structures. Heats of adsorption, Brauner‐Emmet‐Teller (BET) surface area, and total pore volume were deduced to be the crucial parameters for low, medium, and high range of relative pressures in the isotherm. Therefore, the chromium atoms in MIL‐101‐Cr are better adsorbers of IAA than MIL‐100‐Al at lower pressures despite the similarities in terms of the type of linkers and topology. Our simulation results corroborated the earlier published studies on the self‐association behaviour of sevoflurane molecules based on the experimental isotherms reported for MOF‐177‐Zn. Finally, the high polarity of IAA is thought to explain good low‐pressure simulation/experiment data agreement for the MOFs possessing coordinatively unsaturated sites (CUS) despite using generic DREIDING FF for the framework atoms. Our in‐house parsing code helped realize that the grand‐canonical Monte‐Carlo simulation speed is not the same for all pressure points but decreases for higher pressure points. This can be explained by increased density of the adsorbates making successful trial moves less probable.

On maximal block topological space

In this paper we create a new topological structure induced by connected simple undirected graphs called maximal block topological space and study some properties of this new type of topology. Also, define some concepts in maximal block topological space like (derived subgraph, closure subgraph and interior subgraph). Some results and properties of vertices and subgraphs in G due to maximal block topological space are proved and discussed. Moreover, showed that a maximal block topological space is T0-space and T1/2-space if and only if G is acyclic graph. Finally, irreducibility and topologically independent of maximal block topological space are introduced.

Big-bang limit of 2 + 1 gravity and Thurston boundary of Teichmüller space

We study the asymptotic behavior of the solution curves of the dynamics of spacetimes of the topological type Σp×R, p > 1, where Σp is a closed Riemann surface of genus p, in the regime of 2 + 1 dimensional classical general relativity. The configuration space of the gauge fixed dynamics is identified with the Teichmüller space (TΣp≈R6p−6) of Σp. Utilizing the properties of the Dirichlet energy of certain harmonic maps, estimates derived from the associated elliptic equations in conjunction with a few standard results of the theory of the compact Riemann surfaces, we prove that every non-trivial solution curve runs off the edge of the Teichmüller space at the limit of the big bang singularity and approaches the space of projective measured laminations/foliations (PMLPMF), the Thurston boundary of the Teichmüller space.

Double-Coupling Resonant Network for Dynamic IPT Systems Used in EV Charging Applications

Dynamic inductive power transfer (DIPT) systems as well as static inductive power transfer (SIPT) systems are typically implemented with H-bridge inverters with resonant compensation networks to control and limit the charging current. However, contrary to SIPT, DIPT implies inherent displacements, in the travel direction, as well as the already expected misalignments (vertical and lateral). The challenges imposed by this feature have an impact on the selected compensation network. Typical single-coupling resonant topologies SS, SP, PS, PP, LCL-S and LCL-P are considered. In this work, a double-coupling SSS topology is proposed for DIPT applications to overcome the limitations of classical topologies. A resonant converter topology with natural current and voltage limitation under misalignment conditions is preferable. This paper performs a finite element analysis (FEA) simulation of the magnetic coupler (MC) in order to extract the coupling factor and self and mutual inductances as a function of the electric vehicle (EV) movement. The MC parameters are used to build a model in MATLAB/Simulink with coupling variation in order to assess the converter behavior under misalignment conditions. The simulation and experimental results demonstrate the applicability of the double-coupling SSS topology for DIPT application by exhibiting safe converter operation under the full range of coupling and load operation (full to no-coupling and full to no-load).

Performance investigations of five-level reduced switches count Η-bridge multilevel inverter

Introduction. This research paper describes a simple five-level single-phase pulse-width modulated inverter topology for photovoltaic grid applications. Multilevel inverters, as opposed to conventional two-level inverters, include more than two levels of voltage while using multiple power switches and lower-level DC voltage levels as input to produce high power, easier, and less modified oscillating voltage. The H-bridge multilevel inverter seems to have a relatively simple circuit design, needs minimal power switching elements, and provides higher efficiency among various types of topologies for multi-level inverters that are presently accessible. Nevertheless, using more than one DC source for more than three voltage levels and switching and conduction losses, which primarily arise in major power switches, continue to be a barrier. The novelty of the proposed work consists of compact modular inverter configuration to connect a photovoltaic system to the grid with fewer switches. Purpose. The proposed system aims to decrease the number of switches, overall harmonic distortions, and power loss. By producing distortion-free sinusoidal output voltage as the level count rises while lowering power losses, the constituted optimizes power quality without the need for passive filters. Methods. The proposed topology is implemented in MATLAB/Simulink with gating pulses and various pulse width modulation technique. Results. With conventional topology, total harmonic distortion, power switches, output voltage, current, power losses, and the number of DC sources are investigated. Practical value. The proposed topology has proven to be extremely useful for deploying photovoltaic-based stand-alone multilevel inverters in grid applications.

On the topology of the transversal slice of a quasi-homogeneous map germ

AbstractWe consider a corank 1, finitely determined, quasi-homogeneous map germ f from $(\mathbb{C}^2,0)$ to $(\mathbb{C}^3,0)$ . We describe the embedded topological type of a generic hyperplane section of $f(\mathbb{C}^2)$ , denoted by $\gamma_f$ , in terms of the weights and degrees of f. As a consequence, a necessary condition for a corank 1 finitely determined map germ $g\,{:}\,(\mathbb{C}^2,0)\rightarrow (\mathbb{C}^3,0)$ to be quasi-homogeneous is that the plane curve $\gamma_g$ has either two or three characteristic exponents. As an application of our main result, we also show that any one-parameter unfolding $F=(f_t,t)$ of f which adds only terms of the same degrees as the degrees of f is Whitney equisingular.

Syntheses, Crystal Structures, and Catalytic Properties of Three Cu(II) and Cobalt(II) Coordination Compounds Based on an Ether-Bridged Tetracarboxylic Acid.

Three new products, [Cu2(μ3-dppa)(2,2'-bipy)2(H2O)]n·2nH2O (1), [Co4(μ4-dppa)2(phen)4(H2O)4]·2H2O (2), and [Co2(μ6-dppa)(μ-4,4'-bipy)(H2O)2]n·3nH2O (3) were synthesized using a hydrothermal method from Cu(II) and Co(II) metal(II) chlorides, 3-(3,4-dicarboxyphenoxy)phthalic acid (H4dppa), and different auxiliary ligands, namely 2,2'-bipyridine (2,2'-bipy),1,10-phenanthroline (phen), and 4,4'-bipyridine (4,4'-bipy). Products 1-3 were characterized by elemental analysis, FTIR, TGA, PXRD, SEM, and single-crystal X-ray crystallography. The structure of 1 features a 1D chain of the 2C1 topological type. Compound 2 shows a discrete tetrameric complex. Product 3 demonstrates a 3D metal-organic framework (MOF) with the new topology. Their structure and topology, thermal stability, and catalytic activity were studied. In particular, excellent catalytic activity was demonstrated for copper(II)-polymer 1 in the cyanosilylation reaction at 35 °C.

Synthesis of a covalent organic framework with hetero-environmental pores and its medicine co-delivery application

The topology type and the functionalization of pores play an important role in regulating the performance of covalent organic frameworks. Herein, we designed and synthesized the covalent organic framework with hetero-environmental pores using predesigned asymmetrical dialdehyde monomer. According to the results of structural characterization, crystallinity investigation, and theoretical calculation, the hetero-environmental pores of the obtained framework are regarded as the alternant arrangement. The distinctive hetero pore structure leads the designed material to show more advantages as compared with control materials in loading both hydrophobic and hydrophilic antibiotics for wound healing. This dual-antibiotic strategy can expand the antibacterial range as compared with the single antibiotic one, and reduce the generation of drug resistance. In summary, this strategy for designing covalent organic frameworks with hetero-environmental pores can extend the structural variety and provide a pathway for improving the practical application performance of these materials.

Eklemeli imal edilmiş gözenekli topolojilerin ısıl performansı üzerine deneysel incelemeler

Additive manufacturing enables researchers to form unique and unconventional topologies satisfying design compactness, improved efficiency, and lower cost. Design freedom introduced by the additive manufacturing reveals the idea of implementing the topology optimization approach into thermal systems. In this study, changes in thermal performance of three types of topologies: gyroid, hexagon (honeycomb), and rectilinear are experimentally investigated. In addition, porosity level of each topology is varied in between 25%, 50% and 75% to improve the impact of the study. The experimental results indicate that gyroid structures are thermally more efficient (up to 15.6%) than the remaining topologies. Furthermore, thermal diffusivities of the rectilinear and gyroid topologies with 25% porosity level are measured as the extremes, and it is detected that these structures propagate heat 1.1 times greater than the hexagon structure.

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.