Microprocessor-based simulation of sampled data systems with/without a hold device using a set of sample-and-hold functions and Dirac delta functions

In the present work, Dirac delta function (DF) set and sample-and-hold functions (SHF) set are used for microprocessor-based simulation of discrete time as well as sample-and-hold systems. Such simulations are useful for identification of control systems with known input and output sequence. The presented method utilizes operational matrices of different orders in the DF and SHF domain to develop different operational transfer functions. A few open-loop as well as closed-loop systems have been studied and the simulation results obtained are compared with exact solutions derived with the help of z-transform analysis. Experiments have also been carried out to establish the validity of the proposal.     

企业员工流动的系统分析

企业中员工流动是目前较为普遍现象，运用状态转移矩阵模型，描述了企业员工流动的几种主要情况，通过对模型的系统分析，找到了员工流动的原因与规律，并结合具体问题，论述了企业员工流动的管理方法。     

我国公共农业科研机构科研激励制度调查分析——以1338名农业科学家为例

 根据问卷调查的数据对我国公共农业科研机构的科研激励制度进行了描述,讨论了科学家对公共农业科研机构利益目标的认知,并从职称晋升、学术奖励、绩效薪酬等方面分析了现行科研激励制度对科学家的影响。研究表明争取科研经费是得到样本科学家普遍认同的公共农业科研机构利益目标,为农户服务则被样本科学家认为是公共农业科研机构最重要的价值使命。同时现行科研激励制度并没有有效促进科学家学术水平的提高,在学术评审中“打招呼”等潜规则的存在则严重影响了科学家的学术信心。     

Implementation of approach to compute the Lyapunov characteristic exponents for continuous dynamical systems to higher dimensions

A general method for accurately computing the Lyapunov characteristic exponents (LCEs) of continuous dynamical systems has been developed in [10]. In this paper, this method is extended to implementations on systems of arbitrary dimensions. An accurate implementation of the extension of the method to compute LCEs that uses available numerical techniques is presented for systems of arbitrary dimensions. Previously in [10], the original approach had only been implemented for general systems of up to dimension three. Closed form expressions for the exponential of skew symmetric matrices of order 4 and 5 will be presented. These formulas are used to obtain an accurate and efficient implementation of the method for dynamical systems of dimensions 4 and 5. Numerical examples illustrating the accuracy of the implementations are presented.     

创新系统功能分析模型构建及应用

文章探讨了创新的本质和内涵,构建了创新系统功能分析模型,并对我国风电产业创新系统进行了功能演化分析。研究认为,创新的本质是复杂的价值创造过程,创新系统的主要功能是创造新的价值,包括科学价值、技术价值、经济价值、社会价值和文化价值;创新系统构成、创新系统功能和创新政策之间存在内在的逻辑关系,形成一个闭环。风电产业创新系统功能演化分析结果显示,我国风电产业发展具有阶段性特征,并遵循政策路线和技术成长两条路线。     

An application of the Udwadia-Kalaba dynamic formulation to flexible multibody systems

For the transient response analysis of a flexible slider-crank mechanism, the coordinate partitioning scheme and the Udwadia-Kalaba formulation are herein compared. The flexibility of the coupler has been modelled by means of a single Timoshenko beam element. The present analytical treatment can be viewed as an extension of the model discussed by Shabana in his textbook.     

A novel LMI-based optimization algorithm for the guaranteed estimation of the domain of attraction using rational Lyapunov functions

In this article we deal with the classical problem of estimating the domain of attraction (DOA) of autonomous dynamical systems. We propose a new LMI estimation method based on recent results from the mathematical theory of moments. In contrast to previous works we exploit the advantages of rational Lyapunov functions to enhance the estimates. Several examples illustrate the estimation method.     

新创企业动态能力：微观基础、能力演进及研究框架

 新创企业动态能力是创业研究中的一个关键问题。与成熟企业相比,新创企业的动态能力有许多差异。新创企业动态能力的微观基础、能力演进是相关研究中的重点和难点问题。在已有研究的基础上,综合动态能力的影响因素、能力构成和作用机理,提出一个新创企业动态能力的研究框架。     

A method of extracting malicious expressions in bulletin board systems by using context analysis

Bulletin board systems are well-known basic services on the Internet for information frequent exchange. The convenience of bulletin boards enables us to communicate with other persons and to read the communication contents at any time. However, malicious postings about crimes are serious problems for serving companies and users. The extracting scheme of the traditional methods depends on words or a sequence of words without considering contexts of articles and, therefore, it takes a lot of human efforts to alert malicious articles. In order to reduce the human efforts, this paper presents a new filtering algorithm that can recover the error rate of false positive for non-malicious articles by using context analysis. The presented scheme builds detecting knowledge by introducing multi-attribute rules. By the experimental results for 11,019 test data, it turns out that sensitivity and specificity of the presented method become 38.7 and 24.1 (%) points higher than traditional method, respectively.     

新型城镇化背景下地方政府职能转变路径探析

适应社会化、市场化及社会经济发展的客观要求,新型城镇化日益深化,并且也将是未来我国经济发展的一个必然趋势。地方政府必须面对职能转变过程中存在的意识不足、规划不周、权力集中、融资不力等问题,采取积极措施应对局势的变化,积极构建服务型政府,实现地方政府职能有效转变,推动新型城镇化的持续发展。     

Stability analysis of sampled-data systems considering time delays and its application to electric power markets

This paper investigates the stability of linear control systems with aperiodic sampled data and communication delays. A systematic analysis method is presented and then it is applied to an electric power market. Firstly, the sampled-data system is transformed into a system with a special time-varying delay via the input delay method. Secondly, a less conservative stability criterion is derived based on Lyapunov theory. Several augmented terms and an extra integral term are introduced during the constructing of candidate Lyapunov–Krasovskii functional (LKF); and an improved free-weighting matrix approach is used to handle with the LKF itself and its derivative for obtaining the relaxed conditions ensuring the positive and decreasing requirements of the LKF. The benefit of those treatments on the conservativeness-reducing is analyzed and verified based on a simple numerical example. Finally, the application of the proposed method to a simplified electric power market is investigated, including modeling the system with market clearing time and communication delay, and determining the stability region. The application also shows the practical significance of the reducing of the conservativeness.     

Dissipativity analysis and synthesis of a class of nonlinear systems with time-varying delays

In this paper, new results are established for the delay-independent and delay-dependent problems of dissipative analysis and state-feedback synthesis for a class of nonlinear systems with time-varying delays with polytopic uncertainties. This class consists of linear time-delay systems subject to nonlinear cone-bounded perturbations. Both delay-independent and delay-dependent dissipativity criteria are established as linear matrix inequality-based feasibility tests. The developed results in this paper for the nominal system encompass available results on H_∞ approach, passivity and positive realness for time-delay systems as special cases. All the sufficient stability conditions are cast. Robust dissipativity as well as dissipative state-feedback synthesis results are also derived. Numerical examples are provided to illustrate the theoretical developments.     

Innovation systems and global value chains: A Co-citation analysis of established linkages and possible future trends

This study draws a historical picture of conceptual linkages of innovation systems (IS) and global value chains (GVC). We used a co-citation technique to map the evolution of these two fields since 1990. We highlighted the connecting nodes over the past three decades. The first decade witnessed a connection between national innovation systems (NIS) and GVC, mediated by regional studies related to industrial clusters and district-based innovation. The tradeoff between tacit sticky local and codified transferable global knowledge and innovation and learning's importance in upgrading in GVC generated two new routes in the second decade. In the last decade, although these routes are retained, their mediating nodes have changed with the literature on technology and sustainable transition from IS and the path dependency role in the evolution of districts in global production networks. Recent trends indicate that evolutionary views on economic geography and catch-up may open new opportunities to link the two, and some lessons highlight the need for more structured interactions in the future.     

Understanding the dynamic and microscopic traits of typical Ethereum accounts

As the most ecologically active cryptocurrency platform, Ethereum has attracted the attention of many researchers. Leveraging its fully public transaction data, most existing analysis models all account interactions as a network and explores it from a static and global perspective. However, their work ignored the investigation of dynamic and microscopic features of accounts. Therefore, we conduct the first work about these features of different kinds of accounts on Ethereum. We select six account types on Ethereum, including exchanges, phishing, etc. Then we characterize and compare the dynamics of their transactions. Next, we construct a transaction ego network for each account, and investigate the network features from the perspective of microscopic structure. Experimental results show that different kinds of accounts have their own traits in terms of transaction features and properties of ego networks, which greatly contributes to understanding their roles. Additionally, there are obvious differences between normal accounts and illegal accounts in some characteristics such as transaction neighbors and interaction patterns. Moreover, we observe that criminal gangs may be participating in phishing scams. Finally, based on the conclusions of the account analysis, we design a variety of account features and use them for the account classification task. The experimental results prove that the dynamic and microscopic features we proposed are beneficial to distinguish different types of accounts. We believe our research can provide reference value for account classification tasks in Ethereum and other blockchains.     

Citation analysis: A social and dynamic approach to knowledge organization

Knowledge organization (KO) and bibliometrics have traditionally been seen as separate subfields of library and information science, but bibliometric techniques make it possible to identify candidate terms for thesauri and to organize knowledge by relating scientific papers and authors to each other and thereby indicating kinds of relatedness and semantic distance. It is therefore important to view bibliometric techniques as a family of approaches to KO in order to illustrate their relative strengths and weaknesses. The subfield of bibliometrics concerned with citation analysis forms a distinct approach to KO which is characterized by its social, historical and dynamic nature, its close dependence on scholarly literature and its explicit kind of literary warrant. The two main methods, co-citation analysis and bibliographic coupling represent different things and thus neither can be considered superior for all purposes. The main difference between traditional knowledge organization systems (KOSs) and maps based on citation analysis is that the first group represents intellectual KOSs, whereas the second represents social KOSs. For this reason bibliometric maps cannot be expected ever to be fully equivalent to scholarly taxonomies, but they are – along with other forms of KOSs – valuable tools for assisting users’ to orient themselves to the information ecology. Like other KOSs, citation-based maps cannot be neutral but will always be based on researchers’ decisions, which tend to favor certain interests and views at the expense of others.     

A method of multiple model adaptive control of affine systems and its application to aero-engines

This paper investigates the multiple model adaptive control problem of affine systems with unknown parameters. Firstly, an adaptive controller with resettable parameters and an adaptive law with projection function are designed to ensure the asymptotic tracking for the reference system and the boundedness of parameters. Secondly, a transformation of system is given to enable a finite-time parameter estimator to calculate the uncertain parameters in the system matrix and the affine item simultaneously. Then, a novel performance index to describe the error between the controlled plant and the identification model is given to orchestrate switchings among identification models aiming to choose the best one. Next, the sufficient condition of the asymptotic convergence for the system error is given. Finally, all designs are evaluated in a hardware-in-the-loop simulation platform of an aero-engine control system and compared with three other methods, the effectiveness and superiority are verified.     

基于系统基模的新产品开发模式研究

新产品开发是企业获得竞争优势的有效策略,新产品开发模式是关系到新产品开发效率及成败的关键一环。新产品开发可分为内包、外包、众包三种模式,系统介绍各模式的内涵、特征、优劣及其发展现状。从动态和系统角度出发,创新性地运用系统基模方法分析新产品开发模式,构建了"成长极限""转移负担""成长与投资不足"系统基模。具体分析各开发模式中可能存在的问题和困境,并提出相应的"杠杆解"。通过案例分析将理论与实践相结合,阐述系统基模对宝洁公司新产品开发模式的实践意义,为企业新产品开发模式的选择及运用提供参考,以期提高新产品开发效率和有效性,提升企业竞争力。     

Fixed-time stabilization of periodic linear systems and its application to the elliptical spacecraft rendezvous

A smooth periodic delayed feedback (SPDF) control scheme is proposed for the fixed-time stabilization problem of linear periodic systems subject to input delay. By investigating the monodromy matrix of the periodic system, it is proved that the SPDF controller can achieve the fixed-time stabilization of linear periodic systems with arbitrarily long yet bounded input delays under the condition that the original system is uniformly completely controllable. The proposed controller is continuously differentiable and smooth. The SPDF control scheme is then applied to the elliptical spacecraft rendezvous problem. The effectiveness of the established method is verified on numerical simulations.