价电子轨道能量拓扑指数与Y、Bi系超导电性的关系

利用价电子轨道能量Ei和价电子层数ni,构建了新的原子点价δi,由点价δi构建价电子轨道能量拓扑指数mE。研究了Y系、Bi系高温超导氧化物与mE的0阶指数的关系,发现有较好的规律性。因此文中提出用价电子轨道能量拓扑指数mE作为Y系、Bi系高温超导氧化物超导电性的一个新判据,对今后制备出具有更高TC的Y系、Bi系超导氧化物有很好的指导意义。

多端口能量路由器拓扑参数设计方法研究

能量路由器是基于电力电子变换器的多能源接口装置,能够提高新能源发电技术的稳定性与效率。针对光伏发电、储能装置等分布式能源接入与能量即插即用、能量灵活接入的目的,设计了1个四接口的能量路由器,由2个光伏发电单元接口、1个储能装置接口以及1个并网接口。光伏发电单元接口采用Boost电路,储能装置接口采用交错并联的Buck/Boost变换器,并网接口采用双向DC/AC变换器。重点分析了该能量路由器的参数设计方法,并设计了10kW的能量路由器。最终在simulink/Matlab中搭建了仿真模型,仿真结果表明:该参数设计方法设计出的参数能够保证能量路由器的动态性能与稳态性能。

一种能量高效的无线传感器网络拓扑控制算法

通过对现有拓扑控制算法的研究,针对无线传感器网络中节点能耗分布不均匀的问题,提出了一种能量高效的拓扑控制算法(EETCA)。该算法以均衡全局能耗为目标,综合考虑了节点的剩余能量、簇的规模、数据最优传输跳数等因素,避免了部分节点能量消耗过快,从而有效地均衡网络负载。仿真结果表明:EETCA在能耗均衡方面均优于原来的算法,延长了无线传感器网络的生命周期。

价电子能量/能级拓扑指数与MgB_2体系超导电性的关系

构建了价电子平均能量/能级拓扑指数mV,计算了二硼化镁体系及掺杂二硼化镁体系的0阶拓扑指数0V,发现与超导转变温度TC之间有良好的规律性,因此文中提出以电性连接性指数0V作为掺杂二硼化镁体系超导电性的判据。

多盲孔缺陷的超声兰姆波时域拓扑能量成像方法研究

传统超声成像方法受瑞利准则的约束,难以对缺陷间距小于成像分辨率阈值的多缺陷进行成像。提出了一种基于时域拓扑能量的超声兰姆波成像方法,将逆散射拓扑成像方法中的拓扑渐进过程转换成求解直接声场和伴随声场。然后通过将伴随声场进行时间反转,两个声场将具有在缺陷处聚焦,在非缺陷处不聚焦的特性。将直接声场和伴随声场进行融合,以时域拓扑能量值作为像素值进行成像,从而使表征缺陷的精度较高。建立了缺陷间距小于分辨率阈值的多盲孔缺陷有限元模型,通过"一发多收"的方式激发S0模式和采集缺陷散射信号,并进行时域拓扑能量成像。仿真结果表明:对于多盲孔缺陷,时域拓扑能量成像法能够获得比延时叠加法和时间反转成像法更高的分辨率,并且能在缺陷间距小于成像分辨率阈值时进行成像。

电负性/价电子轨道能拓扑指数与MgB_2体系转变温度的关系

利用电负性拓扑指数mF和价电子轨道能量拓扑指数mX的0阶指数0F和0V分别计算了MgB2及其掺杂MgB2体系的0F、0V发现其与超导转变温度Tc之间有良好的规律性,转变温度高的物质在最佳掺杂范围对应的0F和0V分别为2.9034-2.9509和3.9218-3.8613内。因此本文就以0F0、V作为掺杂MgB2体系超导电性的一个判据来选取掺杂物及浓度以提高转变温度,为实验工作者今后探索更好的掺杂MgB2体系超导物提供了一个很好的经验借鉴。

多缺陷兰姆波拓扑成像

将时间反转理论与拓扑优化思想结合在一起,引入了直接声场和伴随声场的概念。通过将时间反转后的兰姆波散射信号作为伴随声场中的二次激励源,实现了信号在缺陷处的聚焦,并根据时域拓扑能量公式计算出检测区域内各点的拓扑能量值,从而对薄板内多缺陷进行表征。有限元仿真和实验表明:在多缺陷情形下,延迟叠加法(DelayandSum,DAS)因受瑞利准则的约束而在缺陷间距小于分辨率阈值时,无法对缺陷位置进行定位;时域拓扑能量法通过兰姆波时间反转聚焦、图像融合,不仅提高了缺陷检测分辨率,还消除了多模式、有噪声环境下伪像的干扰。有效推动了兰姆波在板类结构无损检测中的应用。

适用于建筑集成光伏系统的高增益DC-DC变换器拓扑研究

建筑集成光伏(Building Integrated Photovoltaic,简称BIPV)技术,是光伏发电技术的重要发展方向之一。其能量变换拓扑正逐渐向模块式结构发展,这对DC-DC变换器提出了新的要求。本文在分析了现有光伏发电能量变换拓扑结构的基础上,讨论了常见DC-DC变换拓扑的适用性,并给出了建议。

面向电力需求响应的工业园区综合能源系统优化调控研究

在电力需求响应技术不断发展的背景下,工业园区电力系统可通过引入天然气、氢气等多种能源形式实现综合供能,进而以综合能源系统为能量载体实现需求响应参与能力、参与强度的大幅提升,并促进园区新能源发电就地消纳。围绕电网需求响应背景下的工业园区综合能源系统结构设计与优化调控技术展开分析研究,提出了涵盖热、电、氢等多能源形式的工业园区综合能源系统能量拓扑,并建立了复杂约束下的系统优化调控模型,以实现多能负荷参与电网需求响应背景下的综合能源系统经济运行。实验结果表明,工业园区综合能源系统能够通过多能互补的方式促使多能负荷共同参与电网需求响应,在降低系统运行成本的同时减少高峰时段对电网的电力负荷需求,并有效提升新能源就地消纳水平。

电网节点负荷的立体化预测方法

把握统一大电网中任意节点负荷规律,并由此实现任意节点负荷预测对于未来电网智能化的调度与控制具有重要意义。对此,针对节点负荷自身单独、孤立预测所显现的弱点,提出节点负荷的立体化预测体系与方法,在相关性分析的基础上,试图实现电网任意节点负荷的有效预测。该体系包括:电网能量流按层、区的拓扑结构划分,每层的总量与相应节点构成的基本预测单元,以及对任一节点的组合预测。其预测方法分别基于最小二乘支持向量机、卡尔曼滤波以及加权递推最小二乘等技术。实际算例分析表明,节点负荷的立体化预测有利于预测精度的提高,具有实用前景。

超声相控阵全聚焦成像优化算法有限元仿真研究

先进的后处理成像算法能够极大地推动超声无损检测在工业检测中的应用。以Acrylic模型中二维分布的圆孔缺陷为检测对象,使用PZFlex有限元软件建模,MATLAB编写后处理算法程序,研究全聚焦算法、1/2矩阵算法和时域拓扑能量算法,比较图像重建质量、成像效率以及分辨率,并结合网格重构、插值算法和-6dB处理法进一步优化全聚焦算法的图像重建质量和成像效率。结果显示,改进后的全聚焦成像算法比TFM算法的成像效率和分辨率分别提高50%和42.8%,具有很大的应用潜力。

Algebraic algorithm for reliability index weighted capacity of communication network

Communication network has communication capacity and connection reliability of the links. They canbe independently defined and can be used separately, and when the reliability of a communication network isanalyzed from a macroscopical angle of view, it is more objective to express the performance index of a commu-nication network as a whole. The reliability index weighted capacity is just obtained by integrating these two pa-rameters. It is necessary to further study the algorithm to calculate the reliability index of the communicationnetwork with a complicated topologic structure and a whole algebraic algorithm is therefore proposed for calcula-tion of the reliability index weighted capacity of a communication network with a topologic structure. The wholecomputational procedure of the algorithm is illustrated with a typical example.

Energy-Efficient Multi-Mode Clusters Maintenance(M^2CM) for Hierarchical Wireless Sensor Networks

How to energy-efficiently maintain the topology of wireless sensor networks(WSNs) is still a difficult problem because of their numerous nodes,highly dynamic nature,varied application scenarios and limited resources.An energy-efficient multi-mode clusters maintenance(M2CM) method is proposed based on localized and event-driven mechanism in this work,which is different from the conventional clusters maintenance model with always periodically re-clustered among the whole network style based on time-trigger for hierarchical WSNs.M2 CM can meet such demands of clusters maintenance as adaptive local maintenance for the damaged clusters according to its changes in time and space field.,the triggers of M2 CM include such events as nodes' residual energy being under the threshold,the load imbalance of cluster head,joining in or exiting from any cluster for new node or disable one,etc.Based on neighboring relationship of the damaged clusters,one can start a single cluster(inner-cluster) maintenance or clusters(inter-cluster) maintenance program to meet diverse demands in the topology management of hierarchical WSNs.The experiment results based on NS2 simulation show that the proposed method can significantly save energy used in maintaining a damaged network,effectively narrow down the influenced area of clusters maintenance,and increase transmitted data and prolong lifetime of network compared to the traditional schemes.

基于双分支时空步态特征融合的深度学习步态识别

针对现有步态识别方法易受拍摄视角、着装变化影响的问题,提出一种融合二维无肩姿态拓扑能量图(shoulderless pose topological energy maps,SPTEM)和三维局部骨骼步态特征(local skeleton gait features,LSGF)的深度学习步态识别方法.首先,利用轻量级BlazePose姿态估计算法提取步态视频序列中的人体姿态拓扑图以生成SPTEM,在提高检测速度的同时减弱衣物变化带来的影响;然后,引入LSGF以弥补单一能量图特征在多变视角情况下识别准确率较低的不足;最后,提出结合注意力机制的时空特征提取网络模型,并在全连接层将双流特征进行一致融合.在CASIA-B数据集上对所提出方法进行验证,并与当前主流的步态识别方法进行比较,结果表明,所提出方法在跨视角和穿大衣/棉衣条件下的步态识别率都有明显提升.

Demonstration of topological wireless power transfer

Recent advances in non-radiative wireless power transfer(WPT)technique essentially relying on magnetic resonance and near-field coupling have successfully enabled a wide range of applications.However,WPT systems based on double resonators are severely limited to short-or mid-range distance,due to the deteriorating efficiency and power with long transfer distance.WPT systems based on multi-relay resonators can overcome this problem,which,however,suffer from sensitivity to perturbations and fabrication imperfections.Here,we experimentally demonstrate a concept of topological wireless power transfer(TWPT),where energy is transferred efficiently via the near-field coupling between two topological edge states localized at the ends of a one-dimensional radiowave topological insulator.Such a TWPT system can be modelled as a parity-time-symmetric Su-Schrieffer-Heeger(SSH)chain with complex boundary potentials.Besides,the coil configurations are judiciously designed,which significantly suppress the unwanted cross-couplings between nonadjacent coils that could break the chiral symmetry of the SSH chain.By tuning the inter-and intra-cell coupling strengths,we theoretically and experimentally demonstrate high energy transfer efficiency near the exceptional point of the topological edge states,even in the presence of disorder.The combination of topological metamaterials,non-Hermitian physics,and WPT techniques could promise a variety of robust,efficient WPT applications over long distances in electronics,transportation,and industry.

Non-Hermitian pseudo-gaps

The notion of a band gap is ubiquitous in the characterization of matter.Particularly interesting are pseudo-gaps,which are enigmatic regions of very low density of states that have been linked to novel phenomena like high temperature superconductivity.In this work,we discover a novel origin for pseudo-gaps when boundaries are introduced in a non-Hermitian lattice.It generically occurs due to the interference between two or more asymmetric pumping channels,and possess no analog in Hermitian systems.Mathematically,it can be visualized as being created by divergences of spectral flow in the complex energy plane,analogous to how sharp edges creates divergent electric fields near an electrical conductor.A non-Hermitian pseudo-gap can host symmetry-protected mid-gap modes like ordinary topological gaps,but the mid-gap modes are extended instead of edge-localized,and exhibit extreme sensitivity to symmetry-breaking perturbations.Surprisingly,pseudo-gaps can also host an integer number of edge modes even though the pseudo-bands possess fractional topological windings,or even no well-defined Chern number at all,in the marginal case of a phase transition point.Challenging conventional notions of topological bulk-boundary correspondences and even the very concept of a band,pseudo-gaps post profound implications that extend to many-body settings,such as fractional Chern insulators.

Compressive properties and energy absorption of BCC lattice structures with bio-inspired gradient design

Inspired by the gradient structure of the nature,two gradient lattice structures,i.e.,unidirectional gradient lattice(UGL)and bidirectional gradient lattice(BGL),are proposed based on the body-centered cubic(BCC)lattice to obtain specially designed mechanical behaviors,such as load-bearing and energy absorption capacities.First,a theoretical model is proposed to predict the initial stiffness of the gradient lattice structure under compressive loading,and validated against quasi-static compression tests and finite element models(FEMs).The deformation and failure mechanisms of the two structures are further studied based on experiments and simulations.The UGL structure exhibits a layer-by-layer failure mode,which avoids structure-wise shear failure in uniform structures.The BGL structure presents a symmetry deformation pattern,and the failure initiates at the weakest part.Finally,the energy absorption behaviors are also discussed.This study demonstrates the potential application of gradient lattice structures in load-transfer-path modification and energy absorption by topology design.

Implementing a topological quantum model using a cavity lattice

Kitaev model has both Abelian and non-Abelian anyonic excitations. It can act as a starting point for topological quantum compu- tation. However, this model Hamiltonian is difficult to implement in natural condensed matter systems. Here we propose a quantum simulation scheme by constructing the Kitaev model Hamiltonian in a lattice of coupled cavities with embedded A-type three-level atoms. In this scheme, several parameters are tunable, for example, via external laser fields. Importantly, our scheme is based on currently existing technologies and it provides a feasible way of realizing the Kitaev model to explore topological excitations.

Topological quantum catalyst: Dirac nodal line states and a potential electrocatalyst of hydrogen evolution in the TiSi family

Topological nodal line（DNL） semimetals, a closed loop of the inverted bands in its bulk phases, result in the almost flat drumhead-like non-trivial surface states（DNSSs） with an unusually high electronic density near the Fermi level. High catalytic active sites generally associated with high electronic densities around the Fermi level, high carrier mobility and a close-to-zero free energy of the adsorbed state of hydrogen（？G_（H＊）≈0） are prerequisite to design alternative of precious platinum for catalyzing electrochemical hydrogen production from water. By combining these two aspects, it is natural to consider if the DNLs are a good candidate for the hydrogen evolution reaction（HER） or not because its DNSSs provide a robust platform to activate chemical reactions. Here, through first-principles calculations we reported a new DNL TiSi-type family, exhibiting a closed Dirac nodal line due to the linear band crossings in k_y=0 plane.The hydrogen adsorbed state on the surface yields ？G_（H＊） to be almost zero and the topological charge carries participate in HER. The results highlight a new routine to design topological quantum catalyst utilizing the topological DNL-induced surface bands as active sites, rather than edge sites-, vacancy-,dopant-, strain-, or heterostructure-created active sites.

DISTRIBUTED QUANTIZED CONSENSUS FOR AGENTS ON DIRECTED NETWORKS

Communication bandwidth and network topology are two important factors that affect performance of distributed consensus in multi-agent systems.The available works about quantized average consensus assume that the adjacency matrices associated with the digraphs are doubly stochastic,which amounts to that the digital networks are balanced.However,this assumption may be unrealistic in practice.In this paper,without assuming double stochasticity,the authors revisit an existing quantized average consensus protocol with the logarithmic quantization scheme,and investigate the quantized consensus problem in general directed digital networks that are strongly connected but not necessarily balanced.The authors first derive an achievable upper bound of the quantization precision parameter to design suitable logarithmic quantizer,and this bound explicitly depends on network topology.Subsequently,by means of the matrix transformation and the Lyapunov techniques,the authors provide a testable condition under which the weighted average consensus can be achieved with the proposed quantized protocol.