Quasi-synchronization of fractional-order complex networks with random coupling via quantized control

We investigate the quasi-synchronization of fractional-order complex networks(FCNs) with random coupling via quantized control. Firstly, based on the logarithmic quantizer theory and the Lyapunov stability theory, a new quantized feedback controller, which can make all nodes of complex networks quasi-synchronization and eliminate the disturbance of random coupling in the system state, is designed under non-delay conditions. Secondly, we extend the theoretical results under non-delay conditions to time-varying delay conditions and design another form of quantization feedback controller to ensure that the network achieves quasi-synchronization. Furthermore, the error bound of quasi-synchronization is obtained.Finally, we verify the accuracy of our results using two numerical simulation examples.

Synchronization Stability in Weighted Complex Networks with Coupling Delays

Realistic networks display not only a complex topological structure, but also a heterogeneous distribution of weights in connection strengths. In addition, the information spreading through a complex network is often associated with time delays due to the finite speed of signal transmission over a distance. Hence, the weighted complex network with coupling delays have meaningful implications in real world, and resultantly gains increasing attention in various fields of science and engineering. Based on the theory of asymptotic stability of linear time-delay systems, synchronization stability of the weighted complex dynamical network with coupling delays is investigated, and simple criteria are obtained for both delay-independent and delay-dependent stabilities of synchronization states. The obtained criteria in this paper encompass the established results in the literature as special cases. Some examples are given to illustrate the theoretical results.

Synchronization of networks with time-varying couplings

In this paper, we present a review of our recent works on complete synchro-nization analyses of networks of the coupled dynamical systems with time-varying cou-plings. The main approach is composed of algebraic graph theory and dynamic system method. More precisely, the Hajnal diameter of matrix sequence plays a key role in in-vestigating synchronization dynamics and the joint graph across time periods possessing spanning tree is a doorsill for time-varying topologies to reach synchronization. These techniques with proper modification count for diverse models of networks of the cou-pled systems, including discrete-time and continuous-time models, linear and nonlinear models, deterministic and stochastic time-variations. Alternatively, transverse stability analysis of general time-varying dynamic systems can be employed for synchronization study as a special case and proved to be equivalent to Hajnal diameter.

Time-varying coupling-induced logical stochastic resonance in a periodically driven coupled bistable system

Coupling-induced logical stochastic resonance(LSR) can be observed in a noise-driven coupled bistable system where the behaviors of system can be interpreted consistently as a specific logic gate in an appropriate noise level. Here constant coupling is extended to time-varying coupling, and then we investigate the effect of time-varying coupling on LSR in a periodically driven coupled bistable system. When coupling intensity oscillates periodically with the same frequency with periodic force or relatively high frequency, the system successfully yields the desired logic output. When coupling intensity oscillates irregularly with phase disturbance, large phase disturbance reduces the area of optimal parameter region of coupling intensity and response speed of logic devices. Although the system behaves as a desired logic gate when the frequency of time-periodic coupling intensity is precisely equal to that of periodic force, the desired logic gate is not robust against tiny frequency difference and phase disturbance. Therefore, periodic coupling intensity with high frequency ratio is an optimal option to obtain a reliable and robust logic operation.

Synchronization of stochastically hybrid coupled neural networks with coupling discrete and distributed time-varying delays

A general model of linearly stochastically coupled identical connected neural networks with hybrid coupling is proposed, which is composed of constant coupling, coupling discrete time-varying delay and coupling distributed timevarying delay. All the coupling terms are subjected to stochastic disturbances described in terms of Brownian motion, which reflects a more realistic dynamical behaviour of coupled systems in practice. Based on a simple adaptive feedback controller and stochastic stability theory, several sufficient criteria are presented to ensure the synchronization of linearly stochastically coupled complex networks with coupling mixed time-varying delays. Finally, numerical simulations illustrated by scale-free complex networks verify the effectiveness of the proposed controllers.

A Study of Thermal Response and Flow Field Coupling Simulation around Hayabusa Capsule Loaded with Light-Weight Ablator

The numerical simulation of flow field around Hayabusa capsule loaded with light-weight ablator thermal response coupled with pyrolysis gas flow inside the ablator was carried out. In addition, the radiation from high temperature gas around the capsule was coupled with flow field. Hayabusa capsule reentered the atmosphere about 12 km/sec in velocity and Mach number about 30. During such an atmospheric entry, space vehicle is exposed to very savior aerodynamic heating due to convection and radiation. In this study, Hayabusa capsule was treated as a typical model of the atmospheric entry spacecraft. The light-weight ablator had porous structure, and permeability was an important parameter to analyze flow inside ablator. In this study, permeability was a variable parameter dependent on density of ablator. It is found that the effect of permeability of light-weight ablator was important with this analysis.

Modeling and Decoupling of Coupling Tasks in Collaborative Development Process of Complicated Electronic Products

It is important to improve the development efficiency of decoupling a coupling task package according to the information relevancy relation between development tasks in the collaborative development process of complicated electronic products.In order to define the task coupling model in the development process,the weighted directed graph based on the information relevancy is established,and the correspondence between weighted directed graph model and numerical design structure matrix model of coupling tasks is introduced.The task coupling model is quantized,thereby the interactivity matrix of task package is built.A multi-goal task decoupling method based on improved genetic algorithm is proposed to decouple the task coupling model,which transforms the decoupling of task package into a multi-goal optimization issue.Then the improved genetic algorithm is used to solve the interactivity matrix of coupling tasks.Finally,the effectiveness of this decomposition method is proved by using the example of task package decoupling of collaborative development of a radar’s phased array antenna.

Pinning sampled-data synchronization for complex networks with probabilistic coupling delay

We deal with the problem of pinning sampled-data synchronization for a complex network with probabilistic time-varying coupling delay. The sampling period considered here is assumed to be less than a given bound. Without using the Kronecker product, a new synchronization error system is constructed by using the property of the random variable and input delay approach. Based on the Lyapunov theory, a delay-dependent pinning sampled-data synchronization criterion is derived in terms of linear matrix inequalities （LMIs） that can be solved effectively by using MATLAB LMI toolbox. Numerical examples are provided to demonstrate the effectiveness of the proposed scheme.

Spectrum of a Class of Difference Operators with Indefinite Weights

In this study, we use analytical methods and Sylvester inertia theorem to research a class of second order difference operators with indefinite weights and coupled boundary conditions. The eigenvalue problem with sign-changing weight has lasted a long time. The number of eigenvalues and the number of sign changes of the corresponding eigenfunctions of discrete equations under different boundary conditions are mainly studied. For the discrete Sturm-Liouville problems, similar conclusions about the properties of eigenvalues and the number of sign changes of the corresponding eigenfunctions are obtained under different boundary conditions, such as periodic boundary conditions, antiperiodic boundary conditions and separated boundary conditions etc. The purpose of this paper is to extend the similar conclusion to the coupled boundary conditions, which is of great significance to the perfection of the theory of the discrete Sturm-Liouville problems. We came to the following conclusions: first, the eigenvalues of the problem are real and single, the number of the positive eigenvalues is equal to the number of positive elements in the weight function, and the number of negative eigenvalues is equal to the number of negative elements in the weight function. Second, under some conditions, we obtain the sign change of the eigenfunction corresponding to the j-th positive/negative eigenvalue.

Weighted Pseudo Almost Periodic Solutions for a Class of Hematopoiesis Model with Time-Varying Delay

In this paper, firstly, a notion of a class of generalized weighted pseudo al- most periodic function is introduced, then we investigate some basic and essential properties of the space that consists of these functions. Finally, we study the exis- tence of weighted pseudo almost periodic solutions to hematopoiesis model with time- varying delay.

Fragmental Weight-Conservation Combining Scheme for Statistical Signal Transmissions under Fast Time-Varying Channels

Statistical Signal Transmission(SST)is a technique based on orthogonal frequency-division multiplexing(OFDM)and adopts cyclostationary features,which can transmit extra information without additional bandwidth.However,the more complicated environment in 5G communication systems,especially the fast time-varying scenarios,will dramatically degrade the performance of the SST.In this paper,we propose a fragmental weight-conservation combining(FWCC)scheme for SST,to overcome its performance degradation under fast time-varying channels.The proposed FWCC scheme consists of three phases:1、incise the received OFDM stream into pieces;2、endue different weights for fine and contaminated pieces,respectively;3、combine cyclic autocorrelation function energies of all the pieces;and 4、compute the final feature and demodulate data of SST.Through these procedures above,the detection accuracy of SST will be theoretically refined under fast time-varying channels.Such an inference is confirmed through numerical results in this paper.It is demonstrated that the BER performance of proposed scheme outperforms that of the original scheme both in ideal channel estimation conditions and in imperfect channel estimation conditions.In addition,we also find the experiential optimal weight distribution strategy for the proposed FWCC scheme,which facilitates practical applications.

Robust Beamforming Under Channel Prediction Errors for Time-Varying MIMO System

The accuracy of acquired channel state information(CSI)for beamforming design is essential for achievable performance in multiple-input multiple-output(MIMO)systems.However,in a high-speed moving scene with time-division duplex(TDD)mode,the acquired CSI depending on the channel reciprocity is inevitably outdated,leading to outdated beamforming design and then performance degradation.In this paper,a robust beamforming design under channel prediction errors is proposed for a time-varying MIMO system to combat the degradation further,based on the channel prediction technique.Specifically,the statistical characteristics of historical channel prediction errors are exploited and modeled.Moreover,to deal with random error terms,deterministic equivalents are adopted to further explore potential beamforming gain through the statistical information and ultimately derive the robust design aiming at maximizing weighted sum-rate performance.Simulation results show that the proposed beamforming design can maintain outperformance during the downlink transmission time even when channels vary fast,compared with the traditional beamforming design.

Ultra-thin and light-weight spoof surface plasmon polariton coupler achieved by broadside coupled split ring resonators

Low profile and light weight are very important for practical applications of a spoof surface plasmon polariton（SSPP）coupler, especially at low frequencies. In this paper, we propose and design an ultra-thin, light-weight SSPP coupler based on broadside coupled split ring resonators（BC-SRRs）. The size of BC-SRR can be far less than λ/100 and can extremely well control the reflective phases within a subwavelength thickness. Due to the broadside capacitive coupling, the electrical size of BC-SRR is dramatically reduced to guarantee the ultra-thin thickness of the SSPP coupler. The weight of the SSPP coupler is reduced by a low occupation ratio of BC-SRR in the unit cell volume. As an example, a C-band SSPP coupler composed of phase gradient BC-SRRs is designed, fabricated, and measured. Due to the ultra-small size and low occupation ratio of BC-SRRs, the thickness of the coupler is λ/12 and the surface density is only 0.98 kg/m^2. Both simulation and experiment results verify that the coupler can achieve high-efficiency SPP coupling at 5.27 GHz under normal incidence.

河北省休闲农业与旅游业耦合协调关系研究

休闲农业是一项旅游性较强的新兴产业,深入探索休闲农业与旅游业的耦合协调关系是促进两者可持续发展的重要基础。基于此,本研究以河北省为例,构建休闲农业与旅游业评价指标体系,采用熵权法确定指标权重,利用线性加权法测算两系统的综合发展指数,最后利用耦合协调度模型测算2013—2022年河北省休闲农业与旅游业的耦合协调度。实证结果表明:河北省休闲农业与旅游业综合发展指数变动趋势大体保持一致,整体呈现先升后降的趋势,呈现倒“V”型态势,2013—2019年指数上升,2019年后受疫情影响逐渐下降;两系统耦合度较低,目前处于拮抗阶段,耦合协调度发展经历了中度失调、轻度失调、濒临失调、勉强协调、初级协调、勉强协调、濒临失调7个阶段,后期疫情对于两系统的发展影响较大;在划分类型上,以休闲农业主导性为主,两大系统相互支撑、相互促进作用显著。基于此,促进河北省休闲农业与旅游业耦合协调关系进一步健康发展,应建立耦合协调发展管理机制、加强政府扶持及完善基础设施等。

长江经济带居民共同富裕与旅游发展水平耦合关系及影响因素研究

实现居民共同富裕是中国式现代化的本质要求,旅游业作为幸福产业,如何促进居民共同富裕与旅游发展水平协调共进成为当前研究的重点问题.该文以长江经济带为研究区域,构建了居民共同富裕与旅游发展水平指标体系,并基于耦合协调模型和时空地理加权回归模型(GTWR),考察分析2011—2020年居民共同富裕与旅游发展水平关系及其影响因素.结果发现:1)长江经济带旅游发展水平研究期内整体呈波动上升趋势,2020年因受疫情影响而出现跌落,居民共同富裕水平则呈整体逐年上升趋势;两者均呈现出显著空间异质性,但中上游地区旅游发展水平相近.2)居民共同富裕与旅游发展水平耦合协调水平呈波动上升趋势,重庆和贵州两地上升较快,2020年各省市受到疫情影响有所下降;下游地区高于其他地区.3) GTWR模型表明,人口密度、环境治理投入、旅游收入占比、人均GDP因素存在明显的时空差异,不同时期各因素对地区影响强度和波动方向不同,其中人均GDP影响为正向且影响作用较强.

基于改进云模型和线性规划优化算法的山区泥石流危险性评价

泥石流是一种由暴雨或地震诱发常发生在山区的破坏力强大的地质灾害,为了提前预防和减少其破坏能力,使用特定算法评价其危险性十分必要。采用云模型雾化特性对各评价指标权重进行一致性检验后耦合,得到合理的权重阈值区间。以线性规划优化算法通过设定目标函数后对各评价指标在权重区间内动态取值,从而得到各个泥石流沟渠最危险评分。改进了单指标的云数字特征公式,构建覆盖更全面的综合云模型,输入最大危险评分对研究区泥石流沟渠进行危险性分级。将该研究应用在汶川地震后北川县产生的72条泥石流沟渠实例中,其评价结果显示与研究区实际地形环境情况相吻合,为相似类型泥石流灾害的预防提供了新思路。

基于有偏采样的连续进化神经架构搜索

由于需要对每一个搜索到的架构进行独立的性能评估,神经架构搜索(NAS)往往需要耗费大量的时间和计算资源。提出一种基于有偏采样的连续进化NAS方法(OEvNAS)。OEvNAS在架构搜索过程中维护一个超网络,搜索空间中所有的神经网络架构都是该超网络的子网络。在演化计算的每一代对超网络进行少量的训练,子网络直接继承超网络的权重进行性能评估而无需重新训练。为提高超网络的预测性能,提出一种基于有偏采样的超网络训练策略,以更大的概率训练表现优异的网络,在减少权重耦合的同时提高训练效率。此外,设计一种新颖的交叉变异策略来提高算法的全局探索能力。在NATS-Bench和可微分架构搜索(DARTS)两个搜索空间上验证OEvNAS的性能。实验结果表明,OEvNAS的性能超越了对比的主流算法。在NATS-Bench搜索空间上,提出的超网络训练策略在CIFAR-10、CIFAR-100和ImageNet16-200上均取得了优异的预测性能;在DARTS搜索空间上,搜索到的最优神经网络架构在CIFAR-10和CIFAR-100上分别取得了97.67%和83.79%的分类精度。

河南省林旅产业耦合协调关系研究

利用2000—2019年河南省各地级市的林业与旅游业系统的相关数据,构建了河南省林业—旅游业发展水平综合评价指标体系,采用熵权法和耦合协调度对湖南省各地市的林旅产业发展水平的耦合协调度进行了测算,运用探索性空间数据分析方法与地理加权回归模型进行了实证研究。结果表明:河南省林业和旅游业的综合发展水平指数整体保持增长的趋势,旅游业发展水平整体高于林业;在耦合协调度方面,河南省林业与旅游业之间具有较强的耦合关系,初期的耦合协调度水平普遍较低,随后各城市的耦合协调水平有一定的提升,其中洛阳市耦合协调度的提升速率较高;从耦合协调发展的驱动因素来看,河南省林业与旅游业的耦合协调度受经济驱动、环境治理、产业结构、投资、政府、市场驱动等方面的影响。最后,提出了增强林旅产业融合、强化生态环境保护机制、加强资源整合及实现多元业态发展等政策建议。

轨道站网络中心性、客流与空间热力耦合分析

城市空间热力反映了人口聚集与街道活力。为探究城市轨道交通与空间热力分布的互动关系,从微观层面的轨道站点切入,采用百度热力图和轨道站点客流数据,以上海为例,对轨道站点的网络中心性、客流与站域空间热力进行耦合分析。首先采用Pearson双变量相关性研究两类轨道站点属性与空间热力的总体耦合关系,然后引入双变量空间自相关和地理加权回归分析方法分别挖掘网络中心性与站域热力、站域热力与站点客流的空间关联模式,并对比两类耦合性的空间差异。结果表明:轨道站点的网络中心性与空间热力的耦合性明显优于轨道客流与空间热力的耦合性,交通区位优势通常能够形成较高的空间热力,客流水平的影响因素则更为复杂;空间热力更适合量化核心区以外区域的轨道交通与城市空间互动关系,轨道交通网络化对空间热力提升具有乘数效应,而在开发密度低的区域提升空间热力更有助于刺激轨道客流;利用空间热力数据评估城市核心区以外区域的新建站点客流潜力具有可行性,但仅用热力预测客流具有局限性;轨道站点周边城市更新可参考不同空间区位站点的两类耦合性差异进行优化。该研究探索了结合城市空间热力分布完善轨道交通线网布局、针对不耦合因素优化轨道站点公共交通导向型开发(TOD)的分析框架,为微观层面衡量城市轨道交通“人-地”关系提供了新视角。

中国城市经济韧性的水平、耦合协调度与空间分布特征

中国经济的强韧性是防范风险的最有力支撑。以全国282个城市为研究样本,采用熵权法与加权秩和比法测算中国城市经济韧性水平,在此基础上利用耦合协调模型、空间自相关模型研究中国城市经济韧性三大子系统的耦合协调度,分析其空间分布的整体特征。研究发现:2011—2019年,中国城市经济韧性整体处在中等水平且呈现缓慢上升趋势,同时区域差异较大;中国城市经济韧性总体处于中级协调阶段,但各地区三大子系统耦合协调度及其增长情况有所不同;中国城市经济韧性的耦合协调度在空间分布上具有正相关性,且呈现显著的空间集聚特征和方向性。由此建议采取措施扎实推进城市经济韧性及城市经济韧性耦合协调度的全方位提升,提高区域经济的整体发展水平。