Identification of Wiener–Hammerstein models based on variational bayesian approach in the presence of process noise

This paper addresses the identification of Wiener–Hammerstein (WH) models in the presence of process and measurement noises, which has not been well studied yet in the existing works. To achieve an unbiased estimation, the model parameters are obtained by maximizing the likelihood function, which is solved in the expectation-maximization framework. Due to the difficulty of computing the posterior distributions of the latent variables of WH models, variational Bayes (VB) is used here, and a method for approximating the posterior distributions based on Monte Carlo integral is proposed in VB framework. To the best of our knowledge, it is the first time to use VB approach for WH model identification. Two simulation examples demonstrate the effectiveness of the proposed method. Moreover, the proposed method is used for a WH benchmark problem, and the results show that it improves the identification performance.     

Modified multi-innovation stochastic gradient algorithm for Wiener–Hammerstein systems with backlash

In this paper, the identification of the Wiener–Hammerstein systems with unknown orders linear subsystems and backlash is investigated by using the modified multi-innovation stochastic gradient identification algorithm. In this scheme, in order to facilitate subsequent parameter identification, the orders of linear subsystems are firstly determined by using the determinant ratio approach. To address the multi-innovation length problem in the conventional multi-innovation least squares algorithm, the innovation updating is decomposed into sub-innovations updating through the usage of multi-step updating technique. In the identification procedure, by reframing two auxiliary models, the unknown internal variables are replaced by using the outputs of the corresponding auxiliary model. Furthermore, the convergence analysis of the proposed algorithm has shown that the parameter estimation error can converge to zero. Simulation examples are provided to validate the efficiency of the proposed algorithm.     

Flocking of the hybrid Cucker–Smale model

In recent years, both the continuous-time and discrete-time Cucker–Smale models have been widely studied. However, in the practical systems, the dynamics of the agents coupled with each others can be hybrid. Thus, we consider the asymptotic flocking behavior of the hybrid Cucker–Smale model, which is composed of continuous-time dynamic agents and discrete-time dynamic agents. Firstly by some technical lemmas, a super-linear inequality of the derivative of velocity variance is established. Then, we eventually show that the hybrid model can achieve asymptotic flocking for the long-range communication weight¹ case. At last, the simulation examples are given to verify the theoretical results.     

An adaptive iterative learning algorithm for boundary control of a coupled ODE–PDE two-link rigid–flexible manipulator

To perform repetitive tasks, this paper proposes an adaptive boundary iterative learning control (ILC) scheme for a two-link rigid–flexible manipulator with parametric uncertainties. Using Hamilton?s principle, the coupled ordinary differential equation and partial differential equation (ODE–PDE) dynamic model of the system is established. In order to drive the joints to follow desired trajectory and eliminate deformation of flexible beam simultaneously, boundary control strategy is added based on the conventional joints torque control. The adaptive iterative learning algorithm for boundary control scheme includes a proportional-derivative (PD) feedback structure and an iterative term. This novel controller is designed to deal with the unmodeled dynamics and other unknown external disturbances. Numerical simulations are provided to verify the performance of proposed controller in MATLAB.     

A framework to evaluate the interoperability of information systems – Measuring the maturity of the business process alignment

In the current socio-economic environment, to face challenges such as the emergence of new technologies, globalisation and increasing demands from their clients it is inevitable that enterprises will collaborate with others and progressively shift their boundaries. In this context, interoperability has become a prerequisite in the jigsaw of such collaboration. By definition, it is entities’ ability to work together as an organisation. This ability spans a wide range of aspects, embracing both technical and business issues. Over the past decade, both the concept and the context of interoperability have been extended from a largely IT-focused domain to a business-focused domain and the evaluation of interoperability has become a rising concern. An increasing number of studies have concentrated on not just digital but business aspects of human behaviour in the social environment. In general, the wider application domain is the assessment of the interoperability of information systems and processes in any organisation (especially medium and large) that needs multiple processes to interact effectively.To deal with such concerns and pave the way to achievement of more effective collaborative goals in business, the concept of interoperability has been adopted to measure the efficiency and productivity of information systems’ integration. More than twenty approaches have so far been adopted to evaluate this interoperability, however most are unable to assess it at the higher levels, such as at the pragmatic, process and social levels. Hence, we have conducted a three-phase study. Phase 1 reviewed existing interoperability evaluation approaches. To prove the concept, phase 2 proposed the concept of semiotic interoperability and its application to healthcare information systems. This article reports on the third phase of the study, a proposed framework with a group of metrics to measure interoperability from a new perspective – a semiotics perspective. The framework is named the Semiotic Interoperability Evaluation Framework (the SIEF) and has the ability to analyse, measure and assess the interoperability among business processes. The metrics derive from a feasibility study to investigate several interoperability barriers at a hospital. Next, the SIEF was applied in a case study and a detailed interoperability evaluation was conducted.     

Is chess the drosophila artificial intelligence? A social history of an algorithm

Since the mid 1960s, researchers in computer science have famously referred to chess as the 'drosophila' of artificial intelligence (AI). What they seem to mean by this is that chess, like the common fruit fly, is an accessible, familiar, and relatively simple experimental technology that nonetheless can be used productively to produce valid knowledge about other, more complex systems. But for historians of science and technology, the analogy between chess and drosophila assumes a larger significance. As Robert Kohler has ably described, the decision to adopt drosophila as the organism of choice for genetics research had far-reaching implications for the development of 20th century biology. In a similar manner, the decision to focus on chess as the measure of both human and computer intelligence had important and unintended consequences for AL research. This paper explores the emergence of chess as an experimental technology, its significance in the developing research practices of the AI community, and the unique ways in which the decision to focus on chess shaped the program of AI research in the decade of the 1970s. More broadly, it attempts to open up the virtual black box of computer software--and of computer games in particular--to the scrutiny of historical and sociological analysis.     

A model for assessing the coherence of companies’ knowledge strategy

This paper proposes a strategic model for assessing the coherence between companies’ knowledge strategies and their business strategies as well as in their competitive and organisational contexts. In analysing knowledge management literature, we locate three principal strategies: (1) knowledge development (internal or external), (2) knowledge sharing (codification or personalisation) and (3) knowledge exploitation (internal or external). We then position the three strategies and six related policies in the context-content-process dimensions of Pettigrew's model to create a useful framework for strategic analysis and a model to assess the coherence of companies’ knowledge strategy. The model can be used to evaluate how an existing knowledge strategy aligns with a company's characteristics and to formulate and implement a coherent knowledge strategy based on the current competitive environment, organisational context and business strategy.     

Untangling the mystery of absorptive capacity: A process or a set of success factors?

The absorptive capacity of an organization is its ability to translate the knowledge sourced from outside into commercial benefits. Having gained a certain academic interest, the mechanism of the absorptive capacity phenomenon is still puzzling. This paper provides some limited confirmation of earlier frameworks; however, absorptive capacity is demonstrated to be a set of interrelated success factors rather than a sequential process of knowledge articulation in a company. The new model of absorptive capacity proposed encompasses four dimensions: continuing development, bottom-up innovation, trust-based internal cooperation, and deferred knowledge use. The continuing development facet entails a strong positive impact on organizational performance, while the bottom-up innovation dimension deteriorates it. Trust-based internal cooperation and deferred knowledge use report mixed results.     

Stabilization of highly nonlinear hybrid systems driven by Lévy noise and delay feedback control based on discrete-time state observations

There are many hybrid stochastic differential equations (SDEs) in the real-world that don’t satisfy the linear growth condition (namely, SDEs are highly nonlinear), but they have highly nonlinear characteristics. Based on some existing results, the main difficulties here are to deal with those equations if they are driven by Lévy noise and delay terms, then to investigate their stability in this case. The present paper aims to show how to stabilize a given unstable nonlinear hybrid SDEs with Lévy noise by designing delay feedback controls in the both drift and diffusion parts of the given SDEs. The controllers are based on discrete-time state observations which are more realistic and make the cost less in practice. By using the Lyapunov functional method under a set of appropriate assumptions, stability results of the controlled hybrid SDEs are discussed in the sense of pth moment asymptotic stability and exponential stability. As an application, an illustrative example is provided to show the feasibility of our theorem. The results obtained in this paper can be considered as an extension of some conclusions in the stabilization theory.     

Tide–surge interaction model including air bubble effects for the coast of Bangladesh

An estimate of water levels due to the interaction of tide and surge associated with a storm including air bubble effects is made along the coastal region of Bangladesh. For this purpose, a vertically integrated shallow water model in Cartesian coordinate system is developed introducing air bubbles and is solved using nested finite difference schemes. A fine grid model covering the region between 21°15′N to 23°N and 89°E to 92° E has been nested into a coarse grid model covering the region between 15°N to 23°N and 85°E to 95°E in the Bay of Bengal to incorporate all the major islands and coastal bending accurately. By applying tidal forcing through the southern open boundary of the coarse grid model appropriate tidal conditions are generated in the problem domain. Numerical experiments are performed with the help of the model to simulate water levels due to tide and surge interaction including air bubble effects associated with the tropical storm of April 1991. The model results are found to be reasonable and the model can be found to simulate higher water levels in the presence of air bubbles.     

The approximation of the T–S fuzzy model for a class of nonlinear singular system with derivative of input

In this paper, the approximation problem of T–S fuzzy linear singular system for a class of nonlinear singular system with derivative of input is considered and the nonlinear singular system has impulses. Consider a numerical example and a two-wheel drive robot, the T–S fuzzy singular systems are calculated for original system with derivative of input. According to solvability and steps of solving of the two examples, the results are extended to more generally nonlinear singular system with derivative of input. The theorem and algorithm that are given if input-state system is bounded impulse-free item and separable impulse item, it can be approximated by T–S fuzzy singular system with arbitrary accuracy. Finally, a numerical simulation is carried out to show the consistency with theoretical analysis and illustrate the effectiveness of approximation.     

Who captures whom – Pokémon or tourists? A perspective of the Stimulus-Organism-Response model

Since its launch in 2016, Pokémon Go has attracted huge numbers of players, causing a boom in this game market. Although it is not as popular as before, from time to time we still find crowds of players gathered in some spots where Pokémon appear. Numerous reports have explored this Pokémon phenomenon; however, the exact reasons for its popularity remain unknown. The purpose of this study is to explore the post-adoption behavior of Pokémon Go players and its influential factors in the gaming and tourism industries. The theoretical model of stimulus-organism-response was drawn on to examine the impact of the environmental stimuli (social influence and media influence) on players’ internal organisms, which in turn affect their post-experience responses. Moreover, gender differences were also examined in the hypothetical relationships. A total of 342 valid questionnaires from actual gamers were collected in this study, and data analysis was performed using a structural equation model. The results show that stimulus effects, such as social stimuli (critical mass and social interaction) and media stimuli (content timeliness and media richness), have significant impacts on the players’ internal gamified experience (attachment and conformity), which in turn affect their visit intention to catch creatures at certain attractions and to continue playing Pokémon Go. Further, we have also found that players’ intention to visit Pokémon spots is significantly correlated with their intention to continue playing the game. Findings provide links between gamification and tourism literature. Further theoretical and managerial implications are provided.     

A New finding pushes back the history of flying mammals by 70 million years

Teaming up with their US coworkers, CAS paleontologists have discovered, in Ningcheng of northern China's Inner     

Active fault tolerant control of wind turbine systems based on DFIG with actuator fault and disturbance using Takagi–Sugeno fuzzy model

This paper presents an active fault tolerant control (FTC) for doubly fed induction generator (DFIG) with actuator fault and disturbance using Takagi–Sugeno (TS) fuzzy model. The control structure has two parts: fault and disturbance estimation part and FTC part. First, a TS fuzzy model is used to describe the DFIG system. Using a special linear transformation, the original system is decoupled into three independent subsystems: state subsystem without fault and disturbance, disturbance subsystem without fault, and fault subsystem without disturbance. By solving linear matrix inequalities (LMIs), a TS fuzzy observer is designed for the state subsystem without fault and disturbance. Second, estimations of faults and disturbance are obtained using the other subsystem models. Third, an active FTC scheme is developed to reduce the effect of disturbance and actuator faults. Finally, the performance of the proposed FTC is tested for a wind turbine system based on DFIG with actuator faults and disturbance. The simulation results demonstrate that the new FTC scheme makes possible to obtain an efficient fault and disturbance estimation and to reduce the peak current in the transient process.