Application of Wind Generation on Weak Networks Considering Potential System Limitations Due to Transients and Faults

Limited resources are available on the application of wind generation systems interconnected to weak powemetworks. With the need to further interface DG （distributed generation） including WG （wind generation） to weak networks, it is necessary to establish a means of determining what is the most efficient quantity of WG that can be applied in order to maintain stability in the network. This paper establishes a concept that can be applied to weak networks. The aim is to estimate how much WG can be installed on weak networks as well as establishing characteristic responses to generation loss without and with faulted conditions. The main contribution is a thorough understanding of weak network limitation proved to be the most critical parameter in these calculations.

WEAK SEQUENCE-COVERING MAPPING AND CS-NETWORK

A mapping f: X→Y is called weak sequence-covering if whenever {ya} is a sequence in Y converging to y ∈ Y, there exist a subsequence {ynk} and xk∈f^-1(ynk)(k∈N) ,x∈f^-1 (y) such that xk→x. The main results are: (1) Y is a sequential, Frechet, strongly Frechet space iff every weak sepuence-covering mapping onto Y is quotient, pseudo-open, countably bi-quotient respectively, (2) weak sequence-covering mapping preserves cs-network and certain k-(cs-)networks, thus some new mapping theorems on k-(cs-)notworks are proved.

基于FP-network关联规则挖掘算法的配电网薄弱点分析研究

针对配电网运行时经常发生故障的情况,如何快速高效地寻找出配电网中的薄弱点成为了当下配电网安全运行的一大难题。文中采用频繁模式网络(FP-network)模型,建立事务-项目的关联矩阵,并且将所需要进行关联规则挖掘的数据储存在关联矩阵中,从而进行关联规则的数据挖掘。通过算例分析证实了FP-network关联规则挖掘算法可用于配电网薄弱点分析中,并通过配电网实际运行情况验证了该算法的可行性。该算法对配电网数据库中的故障数据仅仅需要进行一次扫描,从而提高了配电网故障数据关联规则挖掘的效率,更有利于配电网实时更新数据库,为分析检测配电网运行中的薄弱点提供了技术支持。

Topic Detection Based on Weak Tie Analysis： A Case Study of LIS Research

Purpose: Based on the weak tie theory, this paper proposes a series of connection indicators Acof weak tie subnets and weak tie nodes to detect research topics, recognize their connections, and understand their evolution.Design/methodology/approach: First, keywords are extracted from article titles and preprocessed. Second, high-frequency keywords are selected to generate weak tie co-occurrence networks. By removing the internal lines of clustered sub-topic networks, we focus on the analysis of weak tie subnets’ composition and functions and the weak tie nodes’ roles.Findings: The research topics’ clusters and themes changed yearly; the subnets clustered with technique-related and methodology-related topics have been the core, important subnets for years; while close subnets are highly independent, research topics are generally concentrated and most topics are application-related; the roles and functions of nodes and weak ties are diversified.Research limitations: The parameter values are somewhat inconsistent; the weak tie subnets and nodes are classified based on empirical observations, and the conclusions are not verified or compared to other methods.Practical implications: The research is valuable for detecting important research topics as well as their roles, interrelations, and evolution trends. Originality/value: To contribute to the strength of weak tie theory, the research translates weak and strong ties concepts to co-occurrence strength, and analyzes weak ties’ functions. Also, the research proposes a quantitative method to classify and measure the topics’ clusters and nodes.

A Double Network Hydrogel with High Mechanical Strength and Shape Memory Properties

Double network(DN)hydrogels as one kind of tough gels have attracted extensive at-tention for their potential applications in biomedical and load-bearing fields.Herein,we import more functions like shape memory into the conventional tough DN hydro-gel system.We synthesize the PEG-PDAC/P(AAm-co-AAc)DN hydrogels,of which the first network is a well-defined PEG(polyethylene glycol)network loaded with PDAC(poly(acryloyloxyethyltrimethyl ammonium chloride))strands,while the second network is formed by copolymerizing AAm(acrylamide)with AAc(acrylic acid)and cross-linker MBAA(N;N′-methylenebisacrylamide).The PEG-PDAC/P(AAm-co-AAc)DN gels exhibits high mechanical strength.The fracture stress and toughness of the DN gels reach up to 0.9 MPa and 3.8 MJ/m^3,respectively.Compared with the conventional double network hydrogels with neutral polymers as the soft and ductile second network,the PEG-PDAC/P(AAm-co-AAc)DN hydrogels use P(AAm-co-AAc),a weak polyelectrolyte,as the second network.The AAc units serve as the coordination points with Fe^3+ions and physically crosslink the second network,which realizes the shape memory property activated by the reducing ability of ascorbic acid.Our results indicate that the high mechanical strength and shape memory properties,probably the two most important characters related to the potential application of the hydrogels,can be introduced simultaneously into the DN hydrogels if the functional monomer has been integrated into the network of DN hydrogels smartly.

Traditional Chinese Medicine-Based Subtyping of Early-Stage Type 2 Diabetes Using Plasma Metabolomics Combined with Ultra-Weak Photon Emission

The prevalence of type 2 diabetes mellitus(T2DM)is increasing rapidly worldwide.Because of the limited success of generic interventions,the focus of the disease study has shifted toward personalized strategies,particularly in the early stages of the disease.Traditional Chinese medicine(TCM)is based on a systems view combined with personalized strategies and has improved our knowledge of personalized diagnostics.From a systems biology perspective,the understanding of personalized diagnostics can be improved to yield a biochemical basis for such strategies;for example,metabolomics can be used in combination with other system-based diagnostic methods such as ultra-weak photon emission(UPE).In this study,we investigated the feasibility of using plasma metabolomics obtained from 44 pre-T2DM subjects to stratify the following TCM-based subtypes:Qi-Yin deficiency,Qi-Yin deficiency with dampness,and Qi-Yin deficiency with stagnation.We studied the relationship between plasma metabolomics and UPE with respect to TCM-based subtyping in order to obtain biochemical information for further interpreting disease subtypes.Principal component analysis of plasma metabolites revealed differences among the TCM-based pre-T2DM subtypes.Relatively high levels of lipids(e.g.,cholesterol esters and triglycerides)were important discriminators of two of the three subtypes and may be associated with a higher risk of cardiovascular disease.Plasma metabolomics data indicate that the lipid profile is an essential component captured by UPE with respect to stratifying subtypes of T2DM.The results suggest that metabolic differences exist among different TCM-based subtypes of pre-T2DM,and profiling plasma metabolites can be used to discriminate among these subtypes.Plasma metabolomics thus provides biochemical insights into system-based UPE measurements.

Spaces with σ-point-discrete N_0-weak bases

It is discussed in this paper the spaces with σ-point-discrete N_0-weak bases. The main results are： （1） A space X has a σ-compact-finite N_0-weak base if and only if X is a k-space with a σ-point-discrete N_0-weak base; （2） Under （CH）, every separable space with a σ-point-discrete N_0-weak base has a countable N_0-weak base.

基于全卷积网络的复杂背景红外弱小目标检测研究

针对复杂背景红外弱小目标检测过程中存在的检测误差率高,检测时间过长等问题,提出基于全卷积网络的复杂背景红外弱小目标检测方法。分析复杂背景红外弱小目标检测的研究进展,找出不同方法的缺陷,采集红外图像,提取目标检测特征,并采用全卷积网络设计弱小目标检测的分类器,实现复杂背景红外弱小目标检测。实验结果表明,该方法的复杂背景红外弱小目标检测精度超过97%,具有较高的实际应用价值。

面向薄弱配电网的农村多能互补系统储能协同优化配置

位于配电网薄弱区域的农村常常存在供能可靠性不足的问题,导致接入大规模光伏的多能互补系统难以在此类地区广泛开展。储能系统作为新型能源系统融合的纽带,能够有效提升此类地区的供能可靠性。为此,文中提出一种面向薄弱配电网的农村多能互补系统(rural multi-energy complementary system,RMES)储能协同优化配置策略。首先,明确包含生物质废弃物能源转化系统的RMES架构。然后,以系统缺供损失成本作为评判依据,提出一种储能配置评价准则。最后,建立计及储能全生命周期成本的RMES多元储能协同优化配置模型。针对该模型的特性,将其解耦转化为包含规划-运行两阶段的双层优化模型,并采用粒子群算法和Gurobi求解器相结合的混合策略进行求解。算例分析表明,所提储能配置评价准则有效激发了RMES配置储能的积极性。此外,构建的多元储能协同配置模型使得RMES表现出更好的经济效益和环境效益,并且在提升系统运行可靠性方面具有优越性。

基于卷积神经网络的红外弱小车辆目标检测方法

传统方法无法获得理想的红外弱小车辆目标检测结果,导致检测误差大,无法满足实际应用要求,为了解决传统红外弱小车辆目标检测方法存在的局限性,及时检测红外图像中的弱小车辆,提高车辆检测精度,设计了基于卷积神经网络的红外弱小车辆目标检测方法。首先对弱小车辆目标检测需要的红外图像进行采集,并对红外图像噪声进行处理,消除噪声对弱小车辆目标检测的干扰,然后采用卷积神经网络建立弱小车辆目标检测模型,最后通过具体仿真实验测试弱小车辆目标检测方法的性能。结果表明,该方法的弱小车辆目标检测精度超过了90%,大幅度减少了弱小车辆目标的误检率,同时弱小车辆目标检测时间控制在5 s内,可以满足弱小车辆目标检测的实时性要求,具有较高的实际应用价值。

LSTM神经网络下多噪声环境通信弱信号识别仿真

由于在多噪声环境下,微弱信号容易被噪声掩盖,导致通信弱信号识别难度较大且极耗费时间。为此,提出一种基于LSTM神经网络的多噪声环境通信弱信号识别方法。通过贪婪权值算法(Takenaka-Malmquist Greedy Algorithm,TMGW)压缩通信弱信号,获取通信弱信号和噪声在时频面上的能量分布特点,对其降噪处理。建立长短记忆(Long Short Term Memory,LSTM)神经网络预测模型结构图,通过损失函数优化训练的权重参数,获取网络训练结果,计算实际值与预测值之差,作为高斯分布检测模型的特征值,实现复杂噪声下通信弱信号识别。仿真结果表明,采用所提方法可以有效地识别通信弱信号,全面提升多噪声环境通信弱信号识别效率。

LEGAN:一种新的暗弱光照图像增强算法

针对暗弱光照图像所存在的亮度、对比度、信噪比低,以及噪声污染大等问题,提出了一种新的暗弱光照图像增强算法LEGAN。该算法将图像输入至所提伽马曲线估计网络求得包含伽马参数的特征图,再经过LEB模块增强亮度,并通过级联LEB的方式迭代增强结果。采用基于PatchGAN的全局-局部判别器结构来提高图像分辨率和恢复图像细节。通过引入感知损失来限制真实标签和输出结果之间的差距,利用照明平滑度损失保持相邻像素之间的单调性关系,同时结合空间一致性损失来增强图像的空间相关性。实验结果表明,相比于现今大多数主流增强算法,该算法的细节还原度相对较高,且能有效避免增强后的图像出现局部亮度不佳等问题。

Study on Influence of Farmers' Relational Network on Their Undertaking Process

We elaborate relevant theories of farmers' relational network,including the Differential Model of Association,the Strength of Weak Tie,Strength of Strong Tie and Favor and Face.The farmers' relational network in the Differential Model of Association can be divided into three layers:strong tie,weak tie and irrelative relationship according to Granovetter theory.These three layers have deep influence on opportunity selection during the undertaking,financing and enterprise development.With rational knowledge of these layers,farmers may exploit undertaking resources.On the basis of these,we made detailed analysis on farmers' selection of relations in the opportunity selection,financing and enterprise development stages.

基于超声导波和Y-Net的复合材料胶接质量检测研究

为实现复合材料胶接结构界面粘接质量的检测,本文提出了一种基于导波检测技术和Y-Net卷积神经网络的界面弱粘接缺陷反演成像方法。计算了超声导波在复合材料胶接结构中传播的相速度频散曲线和波结构,指出了适于实际检测的导波激励频率和激发模态;创建了基于有限元仿真的数据集,将缺陷导波检测数据及概率损伤成像(RAPID)结果作为输入,真实胶接质量结果作为标签数据,对Y-Net进行了搭建、训练、验证和泛化能力测试,并应用结构相似指数(SSIM)和峰值信噪比(PSNR)定量评估了Y-Net的反演能力;搭建了实验系统,开展了复合材料胶接板检测实验。结果表明,本文所提方法可以弱粘接缺陷反演成像方式实现胶接质量检测,成像结果可准确且高质量地表征弱粘接缺陷的位置、形状、大小和弱粘接程度等多个特性。

互联网使用、社会关系网络与农地流转行为

基于中国土地经济调查数据(CLES),运用Eprobit、Eregress、PSM-DID等模型,实证分析了互联网使用对农户土地流转行为的影响;运用4-way反事实总效应分解法,验证了互联网与社会关系网络的“协同”机制。研究发现:①互联网使用能进一步优化土地要素配置,显著促进农户转出土地的几率,同时显著增加了农户土地转出的面积。②机制研究表明,强社会关系网络仅具备中介效应,农户使用互联网通过强社会关系网络可促进农户转出土地;弱社会关系网络同时具备中介效应和交互效应,对农户使用互联网引致的土地流转效应起到拓展的作用;“协同”机制促使经营主体之间的农地交易趋于趋于长期化、合同化。③异质性分析发现,相比于普通农户和村集体,互联网与弱社会关系网络协同能有效促进小农主体与农业企业、专业合作社等新型经营主体交易衔接。因此,建议通过加强农村信息化建设、完善基础设施、加强对新型经营主体的培育与引导等措施,促进农地流转市场健康发展与转型。

弱电网条件下并网逆变器阻抗模型的建立方法综述

阻抗分析法已经成为研究并网逆变器与电网交互系统稳定性的重要手段,为深入研究该问题,回顾了并网逆变器的2种控制模式,其次分析了阻抗建模对于电力系统的稳定性及抑制宽频振荡的重要意义,为解决新型电力系统宽频稳定问题提供理论基础,并详细讨论了dq线性化、谐波线性化的阻抗建模的分析方法以及基于神经网络的并网逆变器阻抗模型辨识方法。通过对比以上方法的应用特点,为实际应用中建模方法提供了理论依据;总结了现有电力电子化系统并网逆变器阻抗建模的优势、挑战,并对其未来研究方向进行了展望,对提高交互系统的稳定性提供了参考指导。

数字企业如何在新兴市场获得收益:弱制度、网络联结与数字产品特性的组态效应

新兴市场对企业国际化具有重要的战略价值,如何在新兴市场获得收益成为企业持续发展的关键。现有文献表明企业网络联结能够帮助跨国企业在新兴市场获取外部资源,应对制度变化带来的不利影响,但忽视了其在不同制度与不同企业中的差异。基于中国App在非洲市场发展的数据,运用模糊集定性比较分析方法探究数字企业在新兴市场实现高绩效的发展路径。研究发现,数字企业网络联结在不同的弱制度与数字产品条件中展示出差异化的作用方式。在弱制度作为核心条件存在时,网络联结可以与弱制度互补为数字企业创造良好的发展环境;在弱制度条件不存在时,数字企业通过网络联结与数字产品特性的互补来增加数字产品价值获得高绩效。研究结论揭示了数字企业在新兴市场的组态发展路径,为其在弱制度环境中实现高绩效提供了策略,同时在理论上将网络联结的作用扩展至弱制度情境和数字企业对象。

欧美月球GNSS规划现状分析综述

月球是地球最重要的天然卫星,当前国际上正在迎来新一轮月球探索高潮,数十个机构和商业团队正在规划月球探索任务,并设想在未来实现航天员长期驻月,围绕月球的“太空竞赛”刚刚开始。月球GNSS(基于现有的地球GNSS以及新的环月卫星通信导航基础设施的月球卫星通信导航定位技术)是空间基准科研的基础,能够提供航天器着陆定位以及月面(及其覆盖空间)定位、导航与授时等服务,同时可以将月球作为试验场,将导航工具包扩展到更远的目的地(如火星)。对欧美近期发布的月球GNSS规划进行了整理归纳,其中包括美国月球GNSS接收机实验(LuGRE)计划和欧洲月光(MoonLight)计划,以及美国中远期月球通信中继和导航系统(LCRNS)计划,这些计划可以为我国开展月球GNSS规划提供参考。

连锁股东关系网络对企业违规的影响研究

本文以沪深A股上市企业为研究对象,从社会关系网络视角考察了企业在连锁股东关系网络中的位置对企业违规行为的影响。研究发现,企业在连锁股东关系网络的中心度越高,越能降低企业违规行为发生的概率。作用机制检验表明,连锁股东关系网络主要通过弱关系的信息优势降低企业代理成本,从而降低企业违规行为发生的概率。进一步研究表明,连锁股东关系网络能有效弥补正式治理机制的不足,对违规行为的抑制作用在监事会规模小和产品市场竞争程度低的企业中更为显著。

老年居民骨干参与乡村社会治理路径研究——以“五老说事”为例

乡村作为我国基层社会治理的重要单元,在推动社会治理和谐、有效的过程中始终发挥着重要作用。老年居民骨干既是基层社会治理的帮手,也是群众的知心人,更是基层和群众的联络人,为乡村治理提供强大动力。基于社会关系网络理论文献剖析发现,强关系网络和弱关系网络与老年居民骨干参与乡村社会治理间存在内在逻辑关系。以“五老说事”这一典型参与社会治理的方式为例,分析发现当前老年居民骨干参与乡村社会治理存在着强关系建构困难、弱关系连接受制等困境。针对上述困境,依托强弱关系理论框架设计了重构强关系网络、拓展弱关系网络等综合性策略,以期优化老年居民骨干参与乡村社会治理路径,进而有效促进乡村发展。