A 3D Fractional-Order Chaotic System with Only One Stable Equilibrium and Controlling Chaos

One 3D fractional-order chaotic system with only one locally asymptotically stable equilibrium is reported. To verify the chaoticity, the maximum Lyapunov exponent (MAXLE) with respect to the fractional-order and chaotic attractors are obtained by numerical calculation for this system. Furthermore, by linear scalar controller consisting of a single state variable, one control scheme for stabilization of the 3D fractional-order chaotic system is suggested. The numerical simulations show the feasibility of the control scheme

Modeling of pneumatic actuator system for high performance nonlinear controller design,"

ABSTRACT Modern applications in robotics such as teleoperations and haptics require high performance force actuators. Pneumatic actuators have significant advantages over electrical motors in terms of force-to-mass ratio. However, position and force control of these actuators in applications that require high bandwidth is not trivial because of the compressibility of air and highly nonlinear flow through pneumatic system components. In this paper, we develop a detailed model of a pneumatic actuator system comprised of a double acting cylinder and a proportional servo valve to be used in position, force or hybrid position and force control. NOMENCLATURE R Ideal gas constant C v Specific heat at constant volume C p Specific heat at constant pressure k Specific heat ratio P Pressure of gas V Volume of gas ρ Density of gas T Temperature of gaṡ m Mass flow rate * Corresponding author.ṁ en Mass flow rate entering to the controlled volume of gaṡ m ex Mass flow rate exiting from the controlled volume of gaṡ Q Heat transfer rate to the controlled volume of gas h en Enthalpy of the gas entering to the controlled volume of gas h ex Enthalpy of the gas exiting from the controlled volume of gas v en Velocity of the gas entering to the controlled volume of gas v ex Velocity of the gas exiting from the controlled volume of gas E Total energy of the controlled volume of gas U Internal energy of control volume of gas W Work delivered by the controlled volume of gas to the envi- INTRODUCTION Modern existing and emerging new applications in robotics require high performance force actuators or hybrid force and position actuators with high force output per unit weight. Compared to traditional geared electrical motors and hydraulic actuators, pneumatic actuators have several advantages [1] in these applications beside their being low cost and clean-operation. Pneumatic actuators can also provide static high force output for a long duration without additional cooling systems as in the case of direct drive electrical motors. However, position and force control of these actuators in applications that require high bandwidth is difficult because of the compressibility of air and the highly nonlinear flow through pneumatic system components. Due to these difficulties, early use of pneumatic actuators had been limited to simple applications that require only positioning at the two ends of the piston stroke. With the increasingly in-depth understanding of the thermodynamics and flow characteristics [2], linear position controllers have been developed To study the control aspects of pneumatic actuators for applications in precision position control, force control and hybrid position and force control, we developed a simple pneumatic testbed that consists of a double acting cylinder with rods and proportional servo valve connected by tubes. In this paper, we derive a detailed model of the pneumatic actuator system

A Novel Evolution-Based Method for Detecting Gene-Gene Interactions

BACKGROUND: The rapid advance in large-scale SNP-chip technologies offers us great opportunities in elucidating the genetic basis of complex diseases. Methods for large-scale interactions analysis have been under development from several sources. Due to several difficult issues (e.g., sparseness of data in high dimensions and low replication or validation rate), development of fast, powerful and robust methods for detecting various forms of gene-gene interactions continues to be a challenging task. METHODOLOGY/PRINCIPAL FINDINGS: In this article, we have developed an evolution-based method to search for genome-wide epistasis in a case-control design. From an evolutionary perspective, we view that human diseases originate from ancient mutations and consider that the underlying genetic variants play a role in differentiating human population into the healthy and the diseased. Based on this concept, traditional evolutionary measure, fixation index (Fst) for two unlinked loci, which measures the genetic distance between populations, should be able to reveal the responsible genetic interplays for disease traits. To validate our proposal, we first investigated the theoretical distribution of Fst by using extensive simulations. Then, we explored its power for detecting gene-gene interactions via SNP markers, and compared it with the conventional Pearson Chi-square test, mutual information based test and linkage disequilibrium based test under several disease models. The proposed evolution-based method outperformed these compared methods in dominant and additive models, no matter what the disease allele frequencies were. However, its performance was relatively poor in a recessive model. Finally, we applied the proposed evolution-based method to analysis of a published dataset. Our results showed that the P value of the Fst -based statistic is smaller than those obtained by the LD-based statistic or Poisson regression models. CONCLUSIONS/SIGNIFICANCE: With rapidly growing large-scale genetic association studies, the proposed evolution-based method can be a promising tool in the identification of epistatic effects

AoBck1 and AoMkk1 Are Necessary to Maintain Cell Wall Integrity, Vegetative Growth, Conidiation, Stress Resistance, and Pathogenicity in the Nematode-Trapping Fungus Arthrobotrys oligospora

The cell wall integrity (CWI) pathway is composed of three mitogen-activated protein kinases (MAPKs), Bck1, Mkk1/2, and Slt2, and is one of the main signaling pathways for fungal pathogenesis, cell wall synthesis, and integrity maintenance. In this study, we characterized orthologs of Saccharomyces cerevisiae Bck1 and Mkk1 in the nematode-trapping (NT) fungus Arthrobotrys oligospora by multiple phenotypic comparison, and the regulation of conidiation and cell wall synthesis was analyzed using real-time PCR (RT-PCR). Both ΔAoBck1 and ΔAoMkk1 mutants showed severe defects in vegetative growth, cell nucleus number, and stress resistance. Both the mutants were unable to produce spores, and the transcription of several genes associated with sporulation and cell wall biosynthesis was markedly downregulated during the conidiation stage. Further, cell walls of the ΔAoBck1 and ΔAoMkk1 mutants were severely damaged, and the Woronin body failed to respond to cellular damage. In particular, the mutants lost the ability to produce mycelial traps for nematode predation. Taken together, AoBck1 and AoMkk1 play a conserved role in mycelial growth and development, CWI, conidiation, multi-stress tolerance, trap formation, and pathogenicity. We highlighted the role of AoBck1 and AoMkk1 in regulating the Woronin body response to cellular damage and cell nucleus development in A. oligospora

A New 3D Autonomous Continuous System with Two Isolated Chaotic Attractors and Its Topological Horseshoes

Based on the 3D autonomous continuous Lü chaotic system, a new 3D autonomous continuous chaotic system is proposed in this paper, and there are coexisting chaotic attractors in the 3D autonomous continuous chaotic system. Moreover, there are no overlaps between the coexisting chaotic attractors; that is, there are two isolated chaotic attractors (in this paper, named “positive attractor” and “negative attractor,” resp.). The “positive attractor” and “negative attractor” depend on the distance between the initial points (initial conditions) and the unstable equilibrium points. Furthermore, by means of topological horseshoes theory and numerical computation, the topological horseshoes in this 3D autonomous continuous system is found, and the topological entropy is obtained. These results indicate that the chaotic attractor emerges in the new 3D autonomous continuous system

A Fractional-Order System with Coexisting Chaotic Attractors and Control Chaos via a Single State Variable Linear Controller

A 3D fractional-order nonlinear system with coexisting chaotic attractors is proposed in this paper. The necessary condition of the existence chaos is q≥0.8477. The fractional-order system exhibits chaotic attractors with the order as low as 2.5431. The largest Lyapunov exponent varying as fractional order q is given. Furthermore, there are the coexisting “positive attractor” and “negative attractor” in this fractional-order chaotic system, and the necessary condition for “positive attractor” and “negative attractor” is obtained. Meanwhile, a control scheme for the stabilization of the unstable equilibrium is suggested via a single state variable linear controller. Numerical results show that the control scheme is valid

A novel formal logic for formal analysis of timeliness in non-repudiation protocols

Non-repudiation protocols are aimed at exchanging digital messages and irrefutable receipts between two mistrusting parties over the Internet, which form the cornerstones of modern secure network transactions. Timeliness is a key security property of non-repudiation protocols, which ensures that protocol agents can terminate their execution within a finite time, and guarantees the satisfaction of time-constraint among protocol events. A number of analysis methods have been proposed, but most of them cannot explicitly express the time factor which plays an important role in protocols. In order to address the challenge of analyzing timeliness, this paper extends the logic of events theory (LoET) and proposes a novel formal logic. By explicitly introducing the time factor into predicate formulas, the new logic can model actions, knowledge, and process states of each agent at different time points, thus enhancing its ability of time description. The formal semantics of new logic is given to avoid ambiguity of logic language and guarantee the soundness of new logic. A typical non-repudiation protocol is analyzed with new logic, and the timeliness flaw is discovered. The proposed logic overcomes the limitations of LoET in terms of time description and effectively addresses the issue of the inability to analyze timeliness