Stationary distribution and extinction of a stochastic predator–prey model with herd behavior

In this paper, we propose and study a stochastic predator–prey model with herd behavior. Firstly, by constructing a suitable stochastic Lyapunov function, we establish sufficient conditions for the existence and uniqueness of an ergodic stationary distribution of the positive solutions to the model. Then we establish sufficient conditions for extinction of the predator population in two cases, that is, the first case is the prey population survival and the predator population extinction; the second case is all the prey and predator populations extinction. Finally, some examples together with numerical simulations are introduced to illustrate the theoretical results.     

Graph convolutional network with sample and feature weights for Alzheimer’s disease diagnosis

Either traditional learning methods or deep learning methods have been widely applied for the early Alzheimer’s disease (AD) diagnosis, but these methods often suffer from the issue of training set bias and have no interpretability. To address these issues, this paper proposes a two-phase framework to iteratively assign weights to samples and features. Specifically, the first phase automatically distinguishes clean samples from training samples. Training samples are regarded as noisy data and thus should be assigned different weights for penalty, while clean samples are of high quality and thus are used to learn the feature weights. In the second phase, our method iteratively assigns sample weights to the training samples and feature weights to the clean samples. Moreover, their updates are iterative so that the proposed framework deals with the training set bias issue as well as contains interpretability on both samples and features. Experimental results on the Alzheimer’s Disease Neuroimaging Initiative (ADNI) dataset show that our method achieves the best classification performance in terms of binary classification tasks and has better interpretability, compared to the state-of-the-art methods.     

Dynamical analysis of a stochastic delayed epidemic model with lévy jumps and regime switching

In this paper a delayed stochastic SLVIQR epidemic model, which can be applied for modeling the new coronavirus COVID-19 after a calibration, is derived. Model is constructed by assuming that transmission rate satisfies the mean-reverting Ornstain-Uhlenbeck process and, besides a standard Brownian motion, another two driving processes are considered: a stationary Poisson point process and a continuous finite-state Markov chain. For the constructed model, the existence and uniqueness of positive global solution is proven. Also, sufficient conditions under which the disease would lead to extinction or be persistent in the mean are established and it is shown that constructed model has a richer dynamic analysis compared to existing models. In addition, numerical simulations are given to illustrate the theoretical results.     

Mixed H∞ and passivity control for a class of stochastic nonlinear sampled-data systems

In this paper, we consider the problem of mixed H_∞ and passivity control for a class of stochastic nonlinear systems with aperiodic sampling. The system states are unavailable and the measurement is corrupted by noise. We introduce an impulsive observer-based controller, which makes the closed-loop system a stochastic hybrid system that consists of a stochastic nonlinear system and a stochastic impulsive differential system. A time-varying Lyapunov function approach is presented to determine the asymptotic stability of the corresponding closed-loop system in mean-square sense, and simultaneously guarantee a prescribed mixed H_∞ and passivity performance. Further, by using matrix transformation techniques, we show that the desired controller parameters can be obtained by solving a convex optimization problem involving linear matrix inequalities (LMIs). Finally, the effectiveness and applicability of the proposed method in practical systems are demonstrated by the simulation studies of a Chua’s circuit and a single-link flexible joint robot.     

Political uncertainty and innovation: The relative effects of national leaders’ education levels and regime systems on firm-level patent applications

We explore the effect of political uncertainty on innovation. In particular, we examine the differential effects of two sources of uncertainty – leaders’ education levels and political regimes (i.e., presidential vs. parliamentary) – on patent applications. We posit that firms react to political uncertainty caused by the unexpected departure of a national leader by investing in patents as growth options. The empirical design analyzes a panel with information from over 62 million patent applications at the aggregated applicant level. Results show that leaders’ unexpected departures cause, on average, increases of approximately 9% in the aggregate growth of patent applications. We also find that the leader’s level of education and the country’s political regime system have significant effects on the relationship between political uncertainty and innovation. The difference between leaders with high and low levels of education accounts for 21% of the change in the growth of patent applications. Further, the effect of political uncertainty on innovation is amplified in presidential systems, which grant leaders more power and make electoral transitions less predictable. The differences between presidential and parliamentary systems account for approximately 16% of the change in the growth of patent applications. As a robustness check, we utilized a subsample of more than 170,000 firms with local and foreign patent applications, as well as a panel of over 5700 government non-profits, universities, and hospitals with local patent applications. Consistent with our theory, the former react to political uncertainty by investing in patents, while the latter remain unaffected. We contribute by showing the theoretical mechanisms linking leader and regime characteristics with patent applications.     

L’ Hopital’S rule-Based adaptive dynamic surface control for a class of strict-Feedback systems with unknown parameters

In this paper, a L’ Hopital’s rule-based adaptive dynamic surface control (L-ADSC) scheme is developed for a class of strict-feedback systems with unknown parameters using backstepping technique. The L-ADSC-derived backstepping technique is deployed to remove differentiation of complex virtual controller, thereby efficiently avoiding ”exlosion of complexity”. The L’ Hopital’s Rule is resorted to tackle singularity problem within controller synthesis. As a consequence, the proposed L-ADSC scheme guarantees that all signals of the closed-loop control system are semi-globally uniformly ultimately bounded. Simulation results show remarkable effectiveness.     

Time-domain simplification of linear time-invariant systems using cauer continued-fraction expansion about sa and s0 alternately

A simple time-domain procedure is presented for deriving simplified models for linear time-invariant systems. It is based on deriving a new realization form for the Cauer continued fraction expansion about s  a and s  0 alternately. A new similarity transformation is also developed which can be used to construct approximate aggregation matrices for the reduced order models obtained by the proposed procedure. Particularly when the original state-space model is in a phase-variable canonical form, the similarity matrix is given explicitly.     

Mixed H∞ and passive control for a class of nonlinear switched systems with average dwell time via hybrid control approach

This paper investigates the mixed H_∞ and passive control problem for a class of nonlinear switched systems based on a hybrid control strategy. To solve this problem, firstly, using the Takagi–Sugeno (T–S) fuzzy model to approximate every nonlinear subsystem, the nonlinear switched systems are modeled as the switched T–S fuzzy systems. Secondly, the hybrid controllers are used to stabilize the switched T–S fuzzy systems. The hybrid controllers consist of dynamic output-feedback controllers for every subsystem and state updating controllers at the switching instant. Thirdly, a new performance index is proposed for switched systems. This new performance index can be viewed as the mixed weighted H_∞ and passivity performance. Based on this new performance index, the weighted H_∞ control problem and the passive control problem for switched T–S fuzzy systems via the hybrid control strategy are solved in a unified framework. Together the multiple Lyapunov functions (MLFs) approach with the average dwell time (ADT) technique, new design conditions for the hybrid controllers are obtained. Under these conditions, the closed-loop switched T–S fuzzy systems are globally uniformly asymptotically stable with a prescribed mixed H_∞ and passivity performance index. Moreover, the desired hybrid controllers can be constructed by solving a set of linear matrix inequalities (LMIs). Finally, the effectiveness of the obtained results is illustrated by a numerical example.     

Using Aristotle’s theory of friendship to classify online friendships: a critical counterview

In a special issue of “Ethics and Information Technology” (September 2012), various philosophers have discussed the notion of online friendship. The preferred framework of analysis was Aristotle’s theory of friendship: it was argued that online friendships face many obstacles that hinder them from ever reaching the highest form of Aristotelian friendship. In this article I aim to offer a different perspective by critically analyzing the arguments these philosophers use against online friendship. I begin by isolating the most common arguments these philosophers use against online friendship and proceed to debunk them one by one by pointing out inconsistencies and fallacies in their arguments and, where needed, offering empirical findings from media and communication studies that offer a more nuanced view on online friendships. I conclude my analysis by questioning the correctness of the application of the Aristotelian theory of friendship by the critics of online friendship: in my view, the critics are applying the Aristotelian theory to online friendships in a rather narrow and limited way. Finally, I conclude my thesis by proposing that in the rapidly changing online landscape, a one-size-fits-all application of the Aristotelian theory on friendship is not sufficient to accurately judge the multitude of relationships that can exist online and that the various positive and valuable elements of online friendships should also be acknowledged and analyzed.     

Stochastic synchronization of semi-Markovian jump chaotic Lur’e systems with packet dropouts subject to multiple sampling periods

This paper is concerned with the problem of stochastic synchronization for semi-Markovian jump chaotic Lur’e systems. Firstly, packet dropouts and multiple sampling periods are both considered. By input-delay approach and then fully considering the probability distribution characteristic of packet dropouts in the modeling, the original system is transformed to a stochastic time-delay system. Secondly, by getting the utmost out of the usable information on the actual sampling pattern, the probability distribution values of stochastic delay taking values in m given intervals can be explicitly obtained. Then, a newly augmented Lyapunov-Krasovskii functional is constructed. Based on that, some sufficient conditions in terms of linear matrix inequalities (LMIs) are derived to ensure the stochastic stability of the error system, and thus, the master system stochastically synchronize with the slave system. Finally, the effectiveness and potential of the obtained results is verified by a simulation example.     

A hybrid stochastic fractal search and local unimodal sampling based multistage PDF plus (1 + PI) controller for automatic generation control of power systems

This paper proposes to use a hybrid Stochastic Fractal Search (SFS) and Local Unimodal Sampling (LUS) based multistage Proportional Integral Derivative (PID) controller consisting of Proportional Derivative controller with derivative Filter (PDF) plus (1 + Proportional Integral) for Automatic Generation Control (AGC) of power systems. Initially, a single area multi-source power system consisting of thermal hydro and gas power plants is considered and parameters of Integral (I) controller is optimized by Stochastic Fractal Search (SFS) algorithm. The superiority of SFS algorithm over some recently proposed approaches such as optimal control, Differential Evolution (DE) and Teaching Learning Based Optimization (TLBO) is demonstrated. To improve the system performance further, LUS is subsequently employed. The study is further extended for different controllers like PID, and proposed multistage PID controller and the superiority of multistage PID controller over conventional PID controller structure is demonstrated. The study is further extended to a two-area six unit multi-source interconnected power system and the superiority of proposed approach over, TLBO and optimal control is demonstrated. Finally the study is extended to a three unequal area system power system with appropriate nonlinearities such as Generation Rate Constraint (GRC), Governor Dead Band (GDB) and time delay. From the analysis, it is found that hybrid SFS–LUS algorithm is superior to the original SFS algorithm and substantial improvement in system performance are realized with proposed multistage PID controller over conventional PID controller structure.     

Minerva’s owl. A response to John Houghton and Charles Oppenheim’s ‘The economic implications of alternative publishing models’

As the twenty-first century approaches … the possibilities of a univerally opulent society being realised have appeared in the sense that [Adam] Smith envisioned it, and the information society that will emerge from the computer communications revolution will be a society that actually moves towards a universal society of plenty … this is what I mean by “Computopia” (Masuda)

Our culture … is already committed to the proposition that the only legitimate knowledge we can gain of our world is that yielded by science. All thinking, dreaming, feeling, indeed all other sources of insight have already be delegitimated. The indoctrination of our children's minds with simplistic and uninformed computer idolatory … is a pandemic phenomenon (Weizenbaum)²     

Improved results on stability analysis of time-varying delay systems via delay partitioning method and Finsler’s lemma

This paper proposes novel conditions based on linear matrix inequalities (LMI) for stability analysis of arbitrarily-fast time-varying delays systems. The time-varying delay interval is divided into smaller pieces in order to obtain an equivalent switched model with multiple time-varying delays of smaller interval, which differently from other existing approaches, the maximum switching frequency is not required for stability analysis. Thus, by the use of augmented Lyapunov-Krasovskii functionals and the Finsler’s lemma, together with some relationships among state variables intentionally defined, the inherent conservatism can be progressively reduced by refining more and more the delay partition. The superiority of the proposed method is illustrated through two benchmark examples.     

What’s mine is mine; what’s yours is mine: private ownership of ICTs as a threat to transparency

In the face of ubiquitous information communication technology, the presence of blogs, personal websites, and public message boards give the illusion of uncensored criticism and discussion of the ethical implications of business activities. However, little attention has been paid to the limitations on free speech posed by the control of access to the Internet by private entities, enabling them to censor content that is deemed critical of corporate or public policy. The premise of this research is that transparency alone will not achieve the desired results if ICT is used in a one way system, controlled by the provider of information. Stakeholders must have an avenue using the same technology to respond to and interact with the information. We propose a model that imposes on corporations a public trust, requiring these gatekeepers of communication technology to preserve individual rights to criticism and review.     

Rotary inverted pendulum with magnetically external perturbations as a source of the pendulum’s base navigation commands

The main objective of this paper is to drive a rotary inverted pendulum by following a desired navigation instruction. This navigation is commanded by the user through a new electromagnetic device which is allowed to perturb the pendulum from its upright position. This apparatus consists of an electronic magnetic driving circuit to introduce commands and realized via two operated magnetic coils. So, the external programmed magnetic perturbation can be seen as external commandments. Therefore, the control problem statement is solved via a modified regulation control implementation, to maintain the pendulum on its upright position and giving free manipulation of the base of the rotary inverted pendulum. Hence, by using the corresponding H_∞-linear matrix inequality technique, a static state controller is designed and tested experimentally so supporting our findings.     

Knowledge workers’ perceptions of potential benefits and challenges of inter-organizational knowledge sharing systems: a Delphi study in the health sector

Inter-organizational knowledge sharing systems (IOKSS) can serve as strategic systems for knowledge-based sectors. Most prior research on inter-organizational systems (IOSs) focuses on organizations’ adoption of such systems; they reveal little about knowledge workers’ adoption of IOS, especially in horizontally linked firms. Knowledge workers’ perception is critical to the deployment of IOKSS at all stages. On the basis of a Delphi technique in the health sector, this study demonstrates that IOKSS can benefit individuals, customers, organizations, the sector, and the knowledge sharing process, and that the challenges of IOKSS arise from individuals, peers, IOKSS, organizations, and the sector.     

A confluence of new technology and the right to water: experience and potential from South Africa’s constitution and commons

South Africa’s groundbreaking constitution explicitly confers a right of access to sufficient water (section 27). But the country is officially ‘water-stressed’ and around 10 % of the population still has no access to on-site or off-site piped or tap water. It is evident that a disconnect exists between this right and the reality for many; however the reasons for the continuation of such discrepancies are not always clear. While barriers to sufficient water are myriad, one significant factor contributing to insufficient and unpredictable access to water is the high percentage of broken water pumps. Previous studies have reported that between 20 and 50 % of all hand operated water pumps installed on the African continent are broken, or out of use. Monitoring and maintenance of pumps, which in South Africa is the responsibility of local municipalities is often ineffective, in part due to the distances between municipal centres and rural communities and the consequent costs of site visits, as well as breakdowns within the local bureaucratic system. The emergence of new telemetry tools that can remotely monitor water applications constitutes a novel and cost-efficient alternative to undertaking regular sites visits. Sustainable, appropriate, low-cost telemetry systems are emerging that could be used to monitor the operational performance of water pumps, or a wide range of other field parameters, and to communicate this information swiftly and cheaply to water service providers, using SMS messages. Data on the performance of water pumps could also be made available to the public online. This is an example of how ICT can be used for water resources management and environmental regulation, as well as in the governance of socio-economic rights: helping to optimize water allocation by improving communication and strengthening accountability.     

The intermediating role of organizational culture and internal analytical knowledge between the capability of big data analytics and a firm’s performance

Firms are increasingly relying on business insights obtained by deploying data analytics. Analytics-driven business decisions have thus taken a strategic imperative role for the competitive advantage of a firm to endure. The extent and effectiveness through which business firms can actually derive benefits by deploying big data-based practices requires deep analysis and calls for extensive research. This study extends the big data analytics capability (BDAC) model by examining the mediatory effects of organizational culture (CL) between internal analytical knowledge (KN) and BDAC, as well as the mediating effects of BDAC between CL and firm performance. The findings bring into focus that CL plays the role of complementary mediation between BDAC and KN to positively impact firm performance (FP); BDAC also plays a similar mediatory role between CL and the performance of a firm.