Engineering and the build environment

Professional bodies regulating training for accountancy students posit that graduates lack certain professional competencies and skills in the workplace and it is evinced that there is a gap between the classroom and the boardroom. The South African Institute of Chartered Accountants (SAICA) call on lecturers to aid with the development of professional competencies and 21 st century skills. Obtainment of these professional competencies and 21 st century skills will prepare students to meet the challenges and opportunities of today's business world. A growing body of literature on teaching and learning indicates that lecturers should amend their teaching practices and pedagogical framework to include teaching and learning of competencies and skills. Teaching and learning research across disciplines suggests that the use of games in the classrooms can help students obtain these competencies and skills. A serious game dubbed Liike has been developed for undergraduate accountancy st...

BACKGROUND The concept of engagement surfaces as a predictor for effectiveness of eHealth interventions. However, a shared understanding of what engagement is and how to measure it, is missing. This makes research in this area fragmented and hard to generalize, and implies that there is a need for a valid way to measure engagement. Therefore, a new scale has been developed; the TWente Engagement with Ehealth Technologies Scale (TWEETS). This scale was developed based on interviews with engaged health app users and employs a definition of engagement that incorporates behavior, cognition and affect, as is common in other fields of research where engagement is used. OBJECTIVE The current paper is aimed at evaluating the psychometric properties of the newly developed TWEETS. As a secondary objective, the psychometric properties of the TWEETS were compared to those of the experiential part of the Digital Behavior Change Intervention engagement scale (DCBI-E). METHODS Participants (n = 28...

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This paper introduces a new 3-D quadratic autonomous system, which can generate two coexisting single-wing chaotic attractors and a pair of diagonal double-wing chaotic attractors. More importantly, the system can generate a fourwing chaotic attractor with very complicated topological structures over a large range of parameters. Some basic dynamical behaviors and the compound structure of the new 3-D system are investigated. Detailed bifurcation analysis illustrates the evolution processes of the system among two coexisting sinks, two coexisting periodic orbits, two coexisting single-wing chaotic attractors, major and minor diagonal double-wing chaotic attractors, and a four-wing chaotic attractor. Poincaré-map analysis shows that the system has extremely rich dynamics. The physical existence of the fourwing chaotic attractor is verified by an electronic circuit. Finally, spectral analysis shows that the system has an extremely broad frequency bandwidth, which is very desirable for engineering applications such as secure communications.

This paper presents a new four-dimensional (4-D) smooth quadratic autonomous chaotic system, which can present periodic orbit, chaos, and hyper-chaos under the conditions on different parameters. Importantly, the system can generate a four-wing hyper-chaotic attractor and a pair of coexistent double-wing hyper-chaotic attractors with two symmetrical initial conditions. Furthermore, a four-wing transient chaos occurs in the system. The dynamic analysis approach- in the paper involves time series, phase portraits, Poincaré maps, bifurcation diagrams, and Lyapunov exponents, to investigate some basic dynamical behaviors of the proposed 4-D system.

This paper reports a new three-dimensional continuous quadratic autonomous chaotic system, modified from the Lorenz system, in which each equation contains a single quadratic cross-product term, which is different from the Lorenz, Ro¨ssler, Chen, Lu¨systems. Basic properties of the new system are analyzed by means of Lyapunov exponent spectrum and bifurcation diagrams. Analysis results show that this system has complex dynamics with some interesting characteristics. r

A new hyperchaotic system is presented, which has two large positive and one small negative Lyapunov exponent over a large range of parameters. As a consequence, system orbits strongly expand in some directions but rapidly shrink in some other directions. These strong expansions and shrinking lead the system orbits to be more disordered and random. Bifurcation and Poincaré-map analyses further show that the system has very rich bifurcations in different directions and extremely complicated dynamics overall. Spectral analysis shows that the system in the hyperchaotic mode has an extremely broad frequency bandwidth of high magnitudes, verifying its unusual random nature and indicating its great potential for some relevant engineering applications such as secure communications.

In this paper, we present an adaptive high order differential feedback controller (HODFC) which is a kind of modelfree control diagram. The proposed HODFC achieves the objective that the system output and its high differentials approximate the given reference input and its high order differentials, respectively. Stability, convergence, and robustness of the closed-loop system are also studied. Moreover, a kind of linearized decoupling control is obtained for MIMO system by a multivariable HODFC.

In practice, there are many chaotic systems whose models are usually unknown or partially unknown. However, the majority of control schemes focus on model-dependent techniques. The model-free controlling problem for affine chaotic systems is investigated in this Letter. An adaptive higher-order differential feedback controller (HODFC), which does not depend on the model of the controlled chaotic system, is presented. The controller utilizes the information of the measured output and the given objective as well as extracted differentials of those via higher-order differentiator (HOD). Stability, convergence and robustness of the closed-loop system are investigated. The presented adaptive HODFC can successfully control the uncertain Lorenz system, the Chen system, the Duffing-Holmes system, the Rössler system, and a new coined 4-dimensional chaotic system, and can drive their trajectories to desired steady states, unstable periodic orbits, or new chaotic states. Importantly, the controller does not use model functions of these systems above. The control scheme is suitable for both chaotic affine systems and ordinary affine systems without knowing their precise models.

In this paper, several smooth canonical 3-D continuous autonomous systems are proposed in terms of the coefficients of nonlinear terms. These systems are derived from the existing 3-D four-wing smooth continuous autonomous chaotic systems. These new systems are the simplest chaotic attractor systems which can exhibit four wings. They have the basic structure of the existing 3-D four-wing systems, which means they can be extended to the existing 3-D four-wing chaotic systems by adding some linear and/or quadratic terms. Two of these systems are analyzed. Although the two systems are similar to each other in structure, they are different in dynamics. One is sensitive to the initializations and sampling time, but another is not, which is shown by comparing Lyapunov exponents, bifurcation diagrams, and Poincaré maps.

This paper introduces a new 3-D quadratic autonomous system, which can generate two coexisting single-wing chaotic attractors and a pair of diagonal double-wing chaotic attractors. More importantly, the system can generate a fourwing chaotic attractor with very complicated topological structures over a large range of parameters. Some basic dynamical behaviors and the compound structure of the new 3-D system are investigated. Detailed bifurcation analysis illustrates the evolution processes of the system among two coexisting sinks, two coexisting periodic orbits, two coexisting single-wing chaotic attractors, major and minor diagonal double-wing chaotic attractors, and a four-wing chaotic attractor. Poincaré-map analysis shows that the system has extremely rich dynamics. The physical existence of the fourwing chaotic attractor is verified by an electronic circuit. Finally, spectral analysis shows that the system has an extremely broad frequency bandwidth, which is very desirable for engineering applications such as secure communications.

A new particle swarm optimization (PSO) algorithm with has a chaotic neural network structure, is proposed. The structure is similar to the Hopfield neural network with transient chaos, and has an improved ability to search for globally optimal solution and does not suffer from problems of premature convergence. The presented PSO model is discrete-time discrete-state. The bifurcation diagram of a particle shows that it converges to a stable fixed point from a strange attractor, guaranteeing system convergence.

In this paper, a new hyperchaotic system is presented by adding a nonlinear controller to the three-dimensional autonomous chaotic system. The generated hyperchaotic system undergoes hyperchaos, chaos, and some different periodic orbits with control parameters changed. The complex dynamic behaviors are verified by means of Lyapunov exponent spectrum, bifurcation analysis, phase portraits and circuit realization. The Multisim results of the hyperchaotic circuit were well agreed with the simulation results.

In this paper, several three dimensional (3-D) four-wing smooth quadratic autonomous chaotic systems are analyzed. It is shown that these systems have a number of similar features. A new 3-D continuous autonomous system is proposed based on these features. The new system can generate a four-wing chaotic attractor with less terms in the system equations. Several basic properties of the new system is analyzed by means of Lyapunov exponents, bifurcation diagrams and Poincare maps. Phase diagrams show that the equilibria are related to the existence of multiple wings.

In this paper, several three dimensional (3-D) four-wing smooth quadratic autonomous chaotic systems are analyzed. It is shown that these systems have a number of similar features. A new 3-D continuous autonomous system is proposed based on these features. The new system can generate a four-wing chaotic attractor with less terms in the system equations. Several basic properties of the new system is analyzed by means of Lyapunov exponents, bifurcation diagrams and Poincare maps. Phase diagrams show that the equilibria are related to the existence of multiple wings.

This Letter contains three parts. First, it analyzes some basic properties of a new complex four-dimensional (4D) continuous autonomous chaotic system, in which each equation contains a cubic cross-product term. The new system has 9 equilibria, which display graceful symmetry with respect to the origin and the coordinate planes, and they have similarity associated with their linearized characteristics and along with invariant manifolds. Second, under constant control, the system displays (i) two coexisting symmetric double-wing chaotic attractors simultaneously, and (ii) two coexisting asymmetric double-wing and two coexisting single-wing attractors including chaotic, period-doubling, and periodic orbits. The evolution process of an attractor from double-wing to single-wing is investigated via a distribution diagram of equilibria and bifurcation diagrams of the system states. Finally, several circuits are built for different configurations of the new system, which show a good agreement between computer simulations and experimental results, revealing some important distinctions in applications arising from different frequencies used. .hk (G. Chen).

In this paper, a new simple 4D smooth autonomous system is proposed, which illustrates two interesting rare phenomena: first, this system can generate a four-wing hyperchaotic and a four-wing chaotic attractor and second, this generation occurs under condition that the system has only one equilibrium point at the origin. The dynamic analysis approach in the paper involves time series, phase portraits, Lyapunov exponents, bifurcation diagram, and Poincaré maps, to investigate some basic dynamical behaviors of the proposed 4D system. The physical existence of the four-wing hyperchaotic attractor is verified by an electronic circuit. Finally, it is shown that the fractional-order form of the system can also generate a chaotic four-wing attractor.

In this paper, new properties of a four-dimensional chaotic system are investigated. These properties explain the behavior of the system and clarify why it can only generate two coexisting double-wing chaotic attractors but cannot produce a single four-wing chaotic attractor. It is shown that a new system with an extremely complex four-wing chaotic attractor and a larger positive Lyapunov exponent than the original system is formed by using these findings and introducing state feedback control to the system. Some basic dynamical behaviors and the complex structure of the new four-wing autonomous chaotic system are theoretically investigated. A detailed bifurcation analysis demonstrates the evolution process from local attractors to global attractors. The local attractors include two coexisting sinks, two coexisting single-wing periodic orbits and two coexisting double-wing chaotic attractors. The global attractors contain a diagonal double-wing periodic orbit, a diagonal double-wing chaotic attractor and a four-wing chaotic attractor. Spectral analysis indicates that the system in the four-wing chaotic mode has a very wide frequency bandwidth, confirming its random nature and its suitability to engineering applications such as secure communications.

In this paper, a hybrid method using active control and a High Order Differentiator (HOD) methodology is proposed to synchronize chaotic systems. Compared to some traditional active control methods, this new method can synchronize chaotic systems where only output states of the master system are available, i.e. the system is considered a black box. The HOD is used to estimate the derivative information of the master system followed by an active control methodology relying on HOD information. The Qi hyperchaotic system is used to verify the performance of this hybrid method. The proposed method is also compared to some traditional methods. Experimental results show that the proposed method has high synchronization precision and speed and is robust against uncertainties in the master system. The circus implements of the proposed synchronizing scheme are included in this paper. The simulation results show the feasibility of the proposed scheme.