Finite-time stability analysis and stabilization for linear discrete-time system with time-varying delay

The problem of finite-time stability for linear discrete-time systems with time-varying delay is studied in this paper. In order to deal with the time delay, the original system is firstly transformed into two interconnected subsystems. By constructing a delay-dependent Lyapunov–Krasovskii functional and using a two-term approximation of the time-varying delay, sufficient conditions of finite-time stability are derived and expressed in terms of linear matrix inequalities (LMIs). The derived stability conditions can be applied into analyzing the finite-time stability and deriving the maximally tolerable delay. Compared with the existing results on finite-time stability, the derived stability conditions are less conservative. In addition, for the stabilization problem, we design the state-feedback controller. Finally, numerical examples are used to illustrate the effectiveness of the proposed method.     

The determinants of individuals’ perceived e-security: Evidence from Malaysia

Despite the critical role of individuals’ perceived security in an online environment, previous research has not attempted to comprehensively study the influences and interrelations between the determinants of online individuals’ perceived security. This research employs five theories to examine the interrelations that might exist between the antecedents of individuals’ perceived security in online environment in Malaysia. It is the first attempt to empirically examine the interrelations of the confidentiality related factors identified in the literature which is a significant original contribution. A questionnaire was the primary research methodology and structural equation modeling was employed to test the hypotheses. The findings suggest that individuals’ perceptions about security are significantly influenced by their perceived technical protection while technical protection was found to be influenced by website design features. Moreover, it was found that individuals’ perceptions toward internally provided assurances are highly influenced by externally provided assurances. However, the results found no significant relations between internally and externally provided assurances about a website's security. The findings imply that e-retailers should launch well-designed websites and communicate the technical protection capabilities of their websites to address individuals’ security concerns. The results also suggest that e-traders should consider the factors influencing individuals’ security perceptions when designing/developing their websites.     

Common European framework of reference for languages (CEFR): insights into global policy borrowing in Malaysian higher education

The Common European Framework of Reference for Languages (CEFR) has emerged as a global policy in language education which has been ‘borrowed’ by nations across the world. This paper presents a critical analysis of Malaysia’s borrowing of the CEFR as part of English language curriculum reform with particular reference to policy motivation and implementation processes as outlined in the English Language Education Roadmap for Malaysia (2015–2025). The analysis draws on Phillips and Ochs’s (2003, “Processes of Policy Borrowing in Education: Some Explanatory and Analytical Devices.” Comparative Education 39 (4): 451–461.) framework for examining educational policy borrowing to highlight challenges as well as prospects of the implementation of the global policy in higher education in Malaysia.     

Anti-disturbance control based on disturbance observer for nonlinear systems with bounded disturbances

A composite anti-disturbance control problem for a class of nonlinear systems is studied in this paper. There are two types of disturbances in the systems, one is the matched disturbance with bounded variation rate, the other is the unmatched time-varying disturbances. A nonlinear disturbance observer is designed to estimate the matched disturbances, which can be presented separately from the controller design. By integrating DOBC with back-stepping method, a composite DOBC and back-stepping controller is proposed, and the disturbance estimations are introduced into the design of virtual control laws to compensate the unmatched disturbances. In addition, it is proved that all the states in the closed-loop system are uniformly ultimate bounded (UUB). Finally, a numerical example is given to demonstrate the feasibility and effectiveness of the proposed method.     

New approaches to positive observer design for discrete-time positive linear systems

This paper aims at providing new design approaches for positive observers of discrete-time positive linear systems based on a construction method of linear copositive Lyapunov function for positive systems. First, an efficient positive observer design approach is proposed by using linear programming such that the observer error system is exponentially stable. Furthermore, an interval observer design is proposed for uncertain positive systems. Then, the results are extended to positive time delay systems. In contrast with the previous design approaches, the new design method provides a general observer design with lower computational burden. Finally, three comparison examples are given to show the merit of the new design approach.     

During early to mid adolescence,moderate to vigorous physical activity is associated with restoring sleep,psychological functioning,mental toughness and male gender

Numerous studies showed that regular physical activity (PA) is associated with both favourable and restorative sleep and improved psychological functioning (PF). However, there is little research on the topic covering the early to mid-adolescence period. Moreover, curiosity and exploratory behaviour (CEB) and mental toughness (MT) as a result of PA remains thus far uninvestigated, as do possible gender differences. The aim of the present study was to explore the associations between PA, subjective sleep (sS), PF, CEB, and MT during early to mid-adolescence. A total of 1361 participants (mean age = 13.37 years; range: 11–16 years; 51.2% female) took part in the study. They completed questionnaires covering PA, sS, PF, CEB, and MT. Greater PA was related to improved PF, better sS, and increased CEB and MT. Compared to male participants, females reported less PA, poorer sS, and had lower PF and MT scores. The present pattern of results suggests that during early and mid-adolescence greater PA was associated with more favourable sS and better PF, including CEB and MT, and that female participants reported lower scores in PA, sS, and PF. Accordingly, if PA has a favourable impact on sleep and psychological functioning, then data suggest that sports participation should be more tailored to increase motivation among female adolescents.     

Optimal trajectory tracking solution: Fractional order viewpoint

In this paper, a generalized trajectory tracking problem for a closed-loop control system is formulated in the optimal control context. A linear time varying plant is considered to track a closed-loop desired trajectory generated by a given mechanism. The theoretical results are obtained based on the Hamilton-Jacobi-Bellman theory in which some generalized semiquadratic value functions are employed as the Lagrangian. In addition, we employ a non-integer order integral of Riemann-Liouville type as the cost functional, so that the trajectory tracking process can be evaluated in an extended optimum manner wherein the fractionality plays the main role. By selecting a suitable fractional order of the integral, a satisfactory optimal control system can be deduced in which least concentration on selecting the weighting matrices is needed. To show the effectiveness of the results, some numerical examples illustrate the potentials.