Eigenvectors of directed graphs and importance scores: dominance,T-Rank,and sink remedies

We study the properties of the principal eigenvector for the adjacency matrix (and related matrices) for a general directed graph. In particular—motivated by the use of the eigenvector for estimating the “importance” of the nodes in the graph—we focus on the distribution of positive weight in this eigenvector, and give a coherent picture which builds upon and unites earlier results. We also propose a simple method—“T-Rank”—for generating importance scores. T-Rank generates authority scores via a one-level, non-normalized matrix, and is thus distinct from known methods such as PageRank (normalized), HITS (two-level), and SALSA (two-level and normalized). We show, using our understanding of the principal eigenvector, that T-Rank has a much less severe “sink problem” than does PageRank. Also, we offer numerical results which quantify the “tightly-knit community” or TKC effect. We find that T-Rank has a stronger TKC effect than PageRank, and we offer a novel interpolation method which allows for continuous tuning of the strength of this TKC effect. Finally, we propose two new “sink remedies”, i.e., methods for ensuring that the principal eigenvector is positive everywhere. One of our sink remedies (source pumping) is unique among sink remedies, in that it gives a positive eigenvector without rendering the graph strongly connected. We offer a preliminary evaluation of the effects and possible applications of these new sink remedies.     

Barrier Lyapunov Functions for the control of output-constrained nonlinear systems

In this paper, we present control designs for single-input single-output (SISO) nonlinear systems in strict feedback form with an output constraint. To prevent constraint violation, we employ a Barrier Lyapunov Function, which grows to infinity when its arguments approach some limits. By ensuring boundedness of the Barrier Lyapunov Function in the closed loop, we ensure that those limits are not transgressed. Besides the nominal case where full knowledge of the plant is available, we also tackle scenarios wherein parametric uncertainties are present. Asymptotic tracking is achieved without violation of the constraint, and all closed loop signals remain bounded, under a mild condition on the initial output. Furthermore, we explore the use of an Asymmetric Barrier Lyapunov Function as a generalized approach that relaxes the requirements on the initial conditions. We also compare our control with one that is based on a Quadratic Lyapunov Function, and we show that our control requires less restrictive initial conditions. A numerical example is provided to illustrate the performance of the proposed control.     

Business processes in the agile organisation: a socio-technical perspective

This paper takes a cross-disciplinary view of the ontology of “business process”: how the concept is treated in the IS research literature and how related concepts (with stronger human behavioural orientation) from organisation and management sciences can potentially inform this IS perspective. In particular, is there room for socio-technical concepts such as technology affordance, derived from the constructivist tradition, in improving our understanding of operational business processes, particularly human-centric business processes? The paper presents a theoretical framework for understanding the role of business processes in organisational agility that distinguishes between the process-as-designed and the process-as-practiced. How this practice aspect of business processes also leads to the improvisation of various information technology enablers, is explored using a socio-technical lens. The posited theoretical framework is illustrated and validated with data drawn from an interpretive empirical case study of a large IT services company. The research suggests that processes within the organisation evolve both by top-down design and by the bottom-up routinisation of practice and that the tension between these is driven by the need for flexibility.     

一种社交网络虚假信息传播控制方法

针对社交网络中日渐泛滥的虚假信息,提出了一种社交网络虚假信息传播控制方法Fidic,针对社交网络中虚假信息传播时途经的用户序列,该方法基于PageRank的思想并结合用户传播虚假信息时的指向关系来对用户进行评级,用户的评级越高表明其在虚假信息传播过程中起到的作用越大.该方法通过控制高评级用户的传播行为从而缩小虚假信息传播的覆盖面,最终达到遏制甚至消除虚假信息传播的目的.实验证明该方法既可以获得较高的精度,而且方便可行,具有较高实用价值.     

蜂窝夹心板频响特性的研究

在聚氨酯泡沫夹心板频响特性的研究基础上，制备了纸蜂窝为芯材，玻璃纤维布增强的环氧层压板和铜版纸为皮层材料的蜂窝夹心板，借助传统扬声器频率响应特性的测试方法，研究了不同结构夹心板的频响特性。研究结果表明：蜂窝孔径增大，夹心板灵敏度增加，频宽变窄；蜂窝芯厚度增加，起振频率增大，声能在低频处的吸收增加；夹心板的芯层与皮层材料的声学阻抗越匹配，频响曲线越平稳。     

Analytical performance of 3?m and 3?m +1 armchair graphene nanoribbons under uniaxial strain

The electronic band structure and carrier density of strained armchair graphene nanoribbons (AGNRs) with widths of n =3 m and n =3 m +1 were examined using tight-binding approximation. The current-voltage (I-V) model of uniaxial strained n =3 m AGNRs incorporating quantum confinement effects is also presented in this paper. The derivation originates from energy dispersion throughout the entire Brillouin zone of uniaxial strained AGNRs based on a tight-binding approximation. Our results reveal the modification of the energy bandgap, carrier density, and drain current upon strain. Unlike the two-dimensional graphene, whose bandgap remains near to zero even when a large strain is applied, the bandgap and carrier density of AGNRs are shown to be sensitive to the magnitude of uniaxial strain. Discrepancies between the classical calculation and quantum calculation were also measured. It has been found that as much as 19% of the drive current loss is due to the quantum confinement. These analytical models which agree well with the experimental and numerical results provide physical insights into the characterizations of uniaxial strained AGNRs.     

Displacement bound of beam‐column with time‐dependent boundary constraints

Abstract

A simplified explicit formula for the displacement bounds of the beam‐column subjected to time‐dependent boundary constraints is proposed. The formula is derived by means of removing time dependence from the boundary conditions. The proposed bounds provide a quick estimation of the displacements for problems with complex loading conditions.