Taming Single Input Chaotic Systems by Fractional Differentiator-Based Controller: Theoretical and Experimental Study

A simple fractional differentiator-based controller is proposed to suppress chaos in a 3D single input chaotic system by stabilizing some of the fixed points. The tuning procedure for the proposed controller is based on the stability concepts in the incommensurate fractional order systems. To show the efficiency of the controller, some numerical simulations are given. Also, to evaluate the practical capability of the proposed controller, we experimentally apply it to control chaos in a chaotic circuit. Moreover, some mathematical analyses are presented to show the applicability of the proposed controller, when its structure is not exactly implementable.     

Predictive functional control for active queue management in congested TCP/IP networks

Predictive functional control (PFC) as a new active queue management (AQM) method in dynamic TCP networks supporting explicit congestion notification (ECN) is proposed. The ability of the controller in handling system delay along with its simplicity and low computational load makes PFC a privileged AQM method in the high speed networks. Besides, considering the disturbance term (which represents model/process mismatches, external disturbances, and existing noise) in the control formulation adds some level of robustness into the PFC-AQM controller. This is an important and desired property in the control of dynamically-varying computer networks. In this paper, the controller is designed based on a small signal linearized fluid-flow model of the TCP/AQM networks. Then, closed-loop transfer function representation of the system is derived to analyze the robustness with respect to the network and controller parameters. The analytical as well as the packet-level ns-2 simulation results show the out-performance of the developed controller for both queue regulation and resource utilization. Fast response, low queue fluctuations (and consequently low delay jitter), high link utilization, good disturbance rejection, scalability, and low packet marking probability are other features of the developed method with respect to other well-known AQM methods such as RED, PI, and REM which are also simulated for comparison.     

Electrification: Conversion woes

With market forces bent on electrification, natural gas distribution compannies may have to contend with a less friendly residential market. This article examines the effects of technology and price on historical trend in market share for electricity and natural gas in residential heating markets. Inter-fuel elasticity of substitution is estimated via econometric analysis of state-level panel data from 2001 to 2017. The results suggest that market shares are insensitive to relative prices in the short run. In the long run, the response tends to be material and statistically significant.     

Flocking Algorithms in Networks with Directed Switching Velocity Interaction Topologies

This paper studies flocking algorithms for multi‐agent systems with directed switching velocity interaction topologies. It is assumed that the position information of each agent is available for agents within its neighborhood region of radius r, however, they communicate the velocity information between each other through unidirectional links modeled by a particular class of directed topologies. A new energy function is defined to analyze the global stability and a sufficient condition is derived for asymptotic flocking in the face of switching topologies. The proposed control strategy guarantees the achievement of desired formations, while avoiding collisions among agents. It also ensures velocity agreement under suitable conditions in a variety of real networks with greatly reduced velocity data exchange. Moreover, a leader‐follower framework is formulated for the described class of interaction topologies and it is shown that a more relaxed condition is required to achieve the desired performance. Finally, several simulations are performed to illustrate and confirm the theoretical results obtained.     

New-generation bonded reinforcing materials for anterior periodontal tooth stabilization and splinting

Teeth are splinted and stabilized in the anterior region for a variety of reasons. This article presents the techniques for periodontal splinting with an adhesive technique using direct placement ribbon reinforced composite resins. The research supporting this technique is also reviewed.     

A hybrid reciprocal model of PCA and K-means with an innovative approach of considering sub-datasets for the improvement of K-means initialization and step-by-step labeling to create clusters with high interpretability

Pattern Analysis and Applications - The K-means algorithm is a popular clustering method, which is sensitive to the initialization of samples and selecting the number of clusters. Its performance...     

An optimal approach to synchronize non‐identical chaotic circuits: An experimental study

The control signal magnitude and energy are among the limiting and therefore important factors to be addressed in the practical applications of a synchronization scheme. In this paper, we present an algorithm to find control parameters in an active sliding mode controller in order to reduce the control effort in synchronizing non‐identical chaotic systems. We also determine uncertainties bound on the systems dynamics for which the calculated control parameters still guarantee the occurrence of the sliding motion of the error states. The proposed controller was practically applied on an experimental setup, consisting of two chaotic circuits, which resembles Chen and Lu systems behavior. Experimental results confirm our theoretical reasoning as well as the effectiveness of the proposed control design technique. Copyright © 2010 John Wiley & Sons, Ltd.     

Experimental study of a chaos‐based communication system in the presence of unknown transmission delay

In this paper, a chaos‐based communication system in the presence of unknown transmission delay is studied. First, under master/slave configurations, two chaotic Chen systems as the slaves are synchronized with a master one via unidirectional coupling. Then at the transmitter, information of an image is embedded within a slave‐one signal and the resultant signal along with another one which is used to determine the transmission delay is transmitted to the receiver. At the receiver, using the received signals and the slave‐two counterpart signal, the image is recovered. The performance of the proposed method is experimentally illustrated. Copyright © 2009 John Wiley & Sons, Ltd.