Search

This paper studies the problem of dynamic output feedback control for networked switched systems which suffer from the asynchronism and deception attack. Different from the general asynchronism that only occurs when there exists at least once switching during the transmission interval, deception attack falsifies the sampled information containing the measured output and switching signal at any transmission instants, and causes the asynchronous control input with nonlinear disturbance inevitably. Then, by employing the different closed-loop systems caused by switching and attack, a stochastic upper bound for controller-mode-dependent Lyapunov function is obtained under the proposed randomized transmission scheme. Under the dynamic output feedback controller, a set of sufficient conditions for this upper bound tending to zero is developed, which indicates the almost sure asymptotic stability of switched systems with the sequence-based average dwell time method. Finally, the effectiveness of the theoretical result is illustrated by adjusting the power voltage in switched RLC circuit model. [ABSTRACT FROM AUTHOR]

In this article, the problem of event-triggered $\mathcal {H}_{\infty }$ control design is investigated for a class of continuous-time switched Takagi–Sugeno (T–S) fuzzy systems. Specifically, the nonweighted $\mathcal {H}_{\infty }$ performance is guaranteed for the system with mode-dependent average dwell-time (MDADT) switching, which is more general than the weighted one in most existing results. Meanwhile, the existence of asynchronous phenomenon between event-triggered instants is taken into account, which is more practical and complicated in the system under consideration. It is compulsive in most existing results that the candidate controllers are synchronous with the subsystems, while this constraint is released to deal with the case that the system switches more than once between two adjacent event-trigger instants. First of all, by verifying the existence of the minimal inter-execution time, it is demonstrated that the adopted event-triggered mechanism can exclude the Zeno behavior. Next, an improved criterion on stability and $\mathcal {H}_{\infty }$ performance is derived for switched T–S fuzzy systems with MDADT switching. On this basis, the mode-dependent event-triggered mechanism and controllers are co-designed. Finally, two simulations are provided to illustrate the effectiveness of the developed event-triggered control scheme. [ABSTRACT FROM AUTHOR]

We generalise Grabisch and Rusinowska (2013) to non-conformist societies. Agents in a network are iteratively picking a yes/no opinion, where updating stems from mutual influence. We introduce a notion of groups based on the signs of influence. We examine a few canonical societies, namely, conformist, communitarian, with leaders, with anti-conformist agents. We investigate stability issues. Any kind of opinion updating model can be hosted by our formalism, provided that: (i) alternatives are binary; (ii) opinion adoption is reversible and independent among agents; (iii) the process is Markovian and stationary; (iv) the number of agents is finite; (v) time is discrete. • Negative influence can be modelised by partial orders on the states of the world. • Groups are characterised with the signs of influences. • Canonical societies can be transformed into one another by simple transformations. • The influence graph can be used to determine the updating scheme. • Influential coalitions are the proper tool to characterise the dynamics. [ABSTRACT FROM AUTHOR]

Highlights • Effect of asynchronous of ground motion compared with the synchronous case. • The asynchronous tunnel motion affects the structural response of the tunnel lining. • The asynchronous induces axial force along the tunnel axis, bending and shear force in the horizontal plane. • Effect of the tunnel geometry and the direction of the incident wave on the tunnel internal forces. Abstract The seismic performance of underground tunnels is affected by some significant factors mostly depending on the seismic loading conditions, the tunnel structure in interaction with the surrounding soil and the three dimensional geometry of the tunnel and the soil stratigraphy. The paper addresses the problem of underground tunnels when subjected to asynchronous seismic shaking along the axis in comparison with the synchronous case that is usually considered in the tunnels design. The study also includes the effect of the curved shape of the tunnel axis, the sudden change of dynamic impedance along its axis, the direction of the propagating wave and the effect of the initial state of stress induced by the excavation process. A finite element model able to catch the main deformation patterns of a tunnel subjected to non-uniform seismic load, coupling the axial and longitudinal deformations has been defined in Plaxis 3D. The numerical model has been first validated with a simplified benchmark case where the soil behaves elastically, and afterwards on the real case of the Metro Line 6 of Naples, assuming a more sophisticated constitutive model for the soil. The results of the 3D full dynamic analyses show the effect of the ground motion asynchronism on the distributions of internal forces in the tunnel lining. [ABSTRACT FROM AUTHOR]

In this paper, we propose a discrete-time biased min-consensus protocol with finite-time convergence by perturbing an existing min-consensus protocol, and investigate its convergence under time-delay and a synchronous state update. It is shown that a complex behavior that can address shortest path planning on a graph emerges from this modified consensus protocol. Theoretical analysis shows that the proposed protocol converges in finite time. In real-world networked systems, there may exist inevitable time delay or asynchronism in state updates. The convergence of biased min-consensus under these non-ideal situations is also theoretically analyzed. To show the scalability and efficiency of the proposed protocol, it is applied to large-scale maze solving on a maze map containing 640 × 640 pixels, which corresponds to a graph with 42,185 nodes. In addition, we also present an application of the proposed protocol to address the complete coverage problem, which further demonstrates the potential of biased min-consensus in robotic applications. [ABSTRACT FROM AUTHOR]

Nowadays, about half of the world population can receive information and exchange opinions in online environments (e.g. the Internet), while the other half do so offline (e.g. face to face). The speed at which information is received and opinions are exchanged in online environment is much faster than offline. To model this phenomenon, in this paper we consider online and offline as two subsystems in opinion dynamics and assume asynchronization when agents in these two subsystems update their opinions. We unfold that asynchro-nization has a strong impact on the steady-state time of the opinion dynamics, the opinion clusters and the interactions between online and offline subsystems. Furthermore, these effects are often enhanced the larger the size of the online subsystem is. [ABSTRACT FROM AUTHOR]

Based on the Logistic-map,an optimized method of generating the spread-spectrum sequences was proposed.An initial value was given and iterated in the Logistic map,then L bit qualification was done to every point,in this way,new spread spectrum sequence would be achieved by shorten.It was compared with conventional chaotic code and Gold code and finally simulated in the DS-CDMA systems.Experiment results show that the iterative times are reduced,the calculating speed is improved,the spread-spectrum sequences can be reshaped with any length and the number of these sequences is larger than Gold sequence in being.The best quantification order is got too.

In this paper, we introduce the two-user asynchronous cognitive multiple access channel (ACMAC). This channel model includes two transmitters, an uninformed one and an informed one, which knows prior to the beginning of a transmission the message which the uninformed transmitter is about to send. We assume that the channel from the uninformed transmitter to the receiver suffers a fixed but unknown delay. We further introduce a modified model, referred to as the asynchronous codeword cognitive multiple access channel (ACC-MAC), which differs from the ACMAC in that the informed user knows the signal that is to be transmitted by the other user, rather than the message that it is about to transmit. We state inner and outer bounds on the ACMAC and the ACC-MAC capacity regions, and we specialize the results to the Gaussian case. Furthermore, we characterize the capacity regions of these channels in terms of multi-letter expressions. Finally, we provide an example that instantiates the difference between message side-information and codeword side-information. [ABSTRACT FROM AUTHOR]

Several channels with asynchronous side information are introduced. We first consider single-user state-dependent channels with asynchronous side information at the transmitter. It is assumed that the state information sequence is a possibly delayed version of the state sequence, and that the encoder and the decoder are aware of the fact that the state information might be delayed. It is additionally assumed that an upper bound on the delay is known to both the encoder and the decoder, but other than that, they are ignorant of the actual delay. We consider both the causal and the noncausal cases and present achievable rates for these channels, and the corresponding coding schemes. We find the capacity of the asynchronous Gel’fand–Pinsker channel with feedback. Finally, we consider a memoryless state-dependent channel with asynchronous side information at both the transmitter and the receiver, and establish a single-letter expression for its capacity. [ABSTRACT FROM PUBLISHER]

Network tomography means to estimate internal link states from end-to-end path measurements. In conventional network tomog- raphy, to make packets transmissively penetrate a network, a cooperation between transmitter and receiver nodes is required, which are located at different places in the network. In this paper, we propose a reflective network tomography , which can totally avoid such a cooperation, since a single transceiver node transmits packets and receives them after traversing back from the network. Fur- thermore, we are interested in identification of a limited number of bottleneck links, so we naturally introduce compressed sensing technique into it. Allowing two kinds of paths such as (fully) loopy path and folded path, we propose a computationally-efficient algorithm for constructing reflective paths for a given network. In the performance evaluation by computer simulation, we confirm the effectiveness of the proposed reflective network tomography scheme. [ABSTRACT FROM AUTHOR]

Batch synchronization has been widely misunderstood as being only needed when variable trajectories have uneven length. Batch data are actually considered not synchronized when the key process events do not occur at the same point of process evolution, irrespective of whether the batch duration is the same for all batches or not. Additionally, a single synchronization procedure is usually applied to all batches without taking into account the nature of asynchronism of each batch, and the presence of abnormalities. This strategy may distort the original trajectories and decrease the signal-to-noise ratio, affecting the subsequent multivariate analyses. The approach proposed in this paper, named multisynchro, overcomes these pitfalls in scenarios of multiple asynchronisms. The different types of asynchronisms are effectively detected by using the warping information derived from synchronization. Each set of batch trajectories is synchronized by appropriate synchronization procedures, which are automatically selected based on the nature of asynchronisms present in data. The novel approach also includes a procedure that performs abnormality detection and batch synchronization in an iterative manner. Data from realistic simulations of a fermentation process of the Saccharomyces cerevisiae cultivation are used to illustrate the performance of the proposed approach in a context of multiple asynchronisms.Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper deals with some very simple interacting particle systems, \emphelementary cellular automata, in the fully asynchronous dynamics: at each time step, a cell is randomly picked, and updated. When the initial configuration is simple, we describe the asymptotic behavior of the random walks performed by the borders of the black/white regions. Following a classification introduced by Fatès \emphet al., we show that four kinds of asymptotic behavior arise, two of them being related to Brownian motion.

This article focuses on the set of 32 legal elementary cellular automata (ECA). We perform an exhaustive study of the systems’ response under: (i) α-asynchronous dynamics, from full asynchronism to perfect synchrony, (ii) κ-scaling, which extends α-asynchrony to compensate for less cell activity, and (iii) ϕ-noise scheme, a perturbation that affects the local transition function and causes a cell to probabilistically miscalculate the new state when it is updated. We propose a new classification in three classes under asynchronous conditions: α-invariant, α-robust, and α-dependent. We classify the 32 legal ECA according to the degree of behavioural modification, and we show that our classifying scheme provides results coherent with the density-based classification. We also show that κ-scaling provides results comparable to synchronous systems, both quantitatively and qualitatively. Subsequently, we analyse the effects of including different levels of noise in synchronous systems. We identify different responses to noise, including systems that are robust to asynchrony and susceptible to noise. To conclude, we investigate the behavioural changes caused by simultaneous asynchrony and noise in models tolerant to both perturbations. We describe a number of effects caused by the interplay of noise and asynchrony, thus further reinforcing that both aspects are pertinent for future studies. [ABSTRACT FROM AUTHOR]

Plant architecture is commonly defined by the adjacency of organs within the structure and their properties. Few studies consider the effect of endogenous temporal factors, namely phenological factors, on the establishment of plant architecture. This study hypothesized that, in addition to the effect of environmental factors, the observed plant architecture results from both endogenous structural and temporal components, and their interplays. Mango tree, which is characterized by strong phenological asynchronisms within and between trees and by repeated vegetative and reproductive flushes during a growing cycle, was chosen as a plant model. During two consecutive growing cycles, this study described vegetative and reproductive development of 20 trees submitted to the same environmental conditions. Four mango cultivars were considered to assess possible cultivar-specific patterns. Integrative vegetative and reproductive development models incorporating generalized linear models as components were built. These models described the occurrence, intensity, and timing of vegetative and reproductive development at the growth unit scale. This study showed significant interplays between structural and temporal components of plant architectural development at two temporal scales. Within a growing cycle, earliness of bud burst was highly and positively related to earliness of vegetative development and flowering. Between growing cycles, flowering growth units delayed vegetative development compared to growth units that did not flower. These interplays explained how vegetative and reproductive phenological asynchronisms within and between trees were generated and maintained. It is suggested that causation networks involving structural and temporal components may give rise to contrasted tree architectures. [ABSTRACT FROM AUTHOR]

Abstract: We analyze the influence of the update dynamics on symmetric 2-player evolutionary games, which are among the most used tools to study the emergence of cooperation in populations of interacting agents. A synchronous dynamics means that, at each time step, all the agents of the population update their strategies simultaneously. An extreme case of asynchronism is sequential dynamics, in which only one agent is updated each time. We first show that these two opposite update dynamics can lead to very different outcomes and that sequential dynamics is detrimental to the emergence of cooperation only when the probability of imitating the most successful neighbors is high. In this sense, we can say that, when the update dynamics has some influence, in general asynchronism is beneficial to the emergence of cooperation. We then explore the consequences of using intermediate levels of asynchronism, where only a fraction of the agents update their behavior each time. In general, the level of cooperation changes smoothly and monotonically as we gradually go from synchronous to sequential dynamics. However, there are some exceptions that should be taken into account. In addition, the results show that the possibility of agents taking irrational decisions has a key role in the sensitivity of these models to changes in the update dynamics. Explanations for the observed behaviors are advanced. [ABSTRACT FROM AUTHOR]

Abstract: Under seismic loads the deformability of an earth dam may induce several effects, including ground-motion amplification and asynchronism between different points of the dam embankment. The paper analyses the asynchronous effects occurring in two existing earth dams, representing well-documented case histories: the El Infiernillo Dam (Mexico) and the Camastra Dam (Italy). Asynchronous effects are analysed by theoretical predictions of the dam seismic response by adopting an advanced dynamic approach, which takes into account the main features that dam soils exhibit under cyclic loading conditions. For different potentially unstable masses within the dam embankment, equivalent accelerations were computed as the ratio between the resultant of the inertial forces and the weight of the volume V associated to the unstable mass. With the exception of very cortical sliding surfaces – not significant for dam stability – in most of the analysed cases the equivalent seismic coefficients do not exceed the peak acceleration at the dam base. [Copyright &y& Elsevier]

This paper addresses the problem of interference mitigation in cooperative Space Time Block Coded Orthogonal Frequency Division Multiplexing (STBC-OFDM) systems in the presence of asynchronism. This scheme first preprocesses the received ST codewords to convert the equivalent fading matrix into a suboptimal ordering upper triangular form based on low complexity permutation QR decomposition, and then suppresses the InterCarrier Interference (ICI) and InterSymbol Interference (ISI) by exploiting Successive Interference Cancellation (SIC) technique. Simulation results show that the performance of the proposed algorithm slightly outmatches or asymptotically approaches to that of the existing Minimum Mean Square Error (MMSE) detector depending on the magnitude of the Carrier Frequency Offsets (CFOs) but with less complexity. [ABSTRACT FROM AUTHOR]

Consider a multiple input multiple output (MIMO) system with pulse amplitude modulation (PAM), where each transmit antenna is allowed to choose a different transmission delay. (We refer to this system as a MIMO system with asynchronous PAM.) Such MIMO systems have been studied before for increasing diversity and avoiding unintentional beam-forming. We quantify the capacity/outage capacity improvement due to asynchronism and the corresponding spectral leakage (if any) for MIMO point-to-point and MIMO broadcast channels. We show that under commonly used transmitter spectral mask constraints, the channel has unbounded degrees of freedom. Synchronous PAM exploits only a finite number of these degrees of freedom, and asynchronism helps to improve capacity. For most cases of interest, two distinct shifts attain most of the capacity improvement. These gains are robust to interference from adjacent carriers. Analysis of the spectrum of the asynchronous PAM suggests that optimal water-filling based schemes are useful for improving capacity only in directional links due to possible spectral leakage, while uniform power allocation leads to capacity improvement without any extra spectral leakage. [ABSTRACT FROM AUTHOR]

We say that a Cellular Automaton (CA) is coalescing when its execution on two distinct (random) initial configurations in the same asynchronous mode (the same cells are updated in each configuration at each time step) makes both configurations become identical after a reasonable time. We prove coalescence for two elementary rules, non coalescence for two other. and show that there exist infinitely many coalescing CA. We then conduct an experimental study on all Elementary CA and show that some rules exhibit a phase transition, which belongs to the universality class of directed percolation. [ABSTRACT FROM AUTHOR]

This paper presents the evolution of the Associative Mesh, a massively parallel SIMD architecture based on reconfigurability and asynchronism. To favor its System on Chip implementation, we introduce a reorganization of the structure based on processors virtualization and evaluate its consequences on hardware cost and algorithmic performances. Using an evaluation environment based on a programming library and a parameterized description of the architecture, we show that a virtualized Associative Mesh achieves real-time execution for a number of complex image processing algorithms, including split and merge segmentation, watershed segmentation and motion detection. [ABSTRACT FROM AUTHOR]

This paper uses recently established properties of compositions of directed graphs together with results from the theory of nonhomogeneous Markov chains to derive worst case convergence rates for the headings of a group of mobile autonomous agents which arise in connection with the widely studied Vicsek consensus problem. The paper also uses graph-theoretic constructions to solve modified versions of the Vicsek problem in which there are measurement delays, asynchronous events, or a group leader. In all three cases the conditions under which consensus is achieved prove to be almost the same as the conditions under which consensus is achieved in the synchronous, delay-free, leaderless case. [ABSTRACT FROM AUTHOR]

This paper gives a formulation of the basins of fixed point states of fully asynchronous discrete-time discrete-state dynamic networks. That formulation provides two advantages. The first one is to point out the different behaviors between synchronous and asynchronous modes and the second one is to allow us to easily deduce an algorithm which determines the behavior of a network for a given initialization. In the context of this study, we consider networks of a large number of neurons (or units, processors, etc.), whose dynamic is fully asynchronous with overlapping updates . We suppose that the neurons take a finite number of discrete states and that the updating scheme is discrete in time. We make no hypothesis on the activation functions of the nodes, so that the dynamic of the network may have multiple cycles and/or basins. Our results are illustrated on a simple example of a fully asynchronous Hopfield neural network. [ABSTRACT FROM AUTHOR]

Abstract: The subject of this paper is to show the high efficiency of asynchronism for parallel iterative algorithms in the context of grid computing, that is to say, with machines scattered on a broad geographical scale. The question is: does asynchronism help to reduce the communication penalty and the overall computation time of such a given algorithm? The asynchronous programming model is evaluated on two test problems representing two important classes of scientific applications: a stationary linear problem and a non-stationary non-linear problem. They are implemented with a multi-threaded environment and tested on a set of distant heterogeneous machines. Several experiments have been performed allowing us to compare the performances of such asynchronous algorithms and also to analyze their behavior and extract the main possible optimizations for their use in a grid computing context. [Copyright &y& Elsevier]

We introduce a theoretical algorithm and its practical version to perform a decentralized detection of the global convergence of parallel asynchronous iterative algorithms. We prove that, even if the algorithm is completely decentralized, the detection of global convergence is achieved on one processor under the classical conditions. The proposed algorithm is very useful in the context of grid computing in which the processors are distributed and in which detecting the convergence on a master processor may be penalizing or even impossible as in Peer to Peer computation frameworks. Finally, the efficiency of the practical algorithm is illustrated in a typical experiment. [ABSTRACT FROM AUTHOR]

The emergence derived from errors is the key importance for both novel computing and novel usage of the computer. In this paper, we propose an implementable experimental plan for the biological computing so as to elicit the emergent property of complex systems. An individual plasmodium of the true slime mold Physarum polycephalum acts in the slime mold computer. Modifying the Elementary Cellular Automaton as it entails the global synchronization problem upon the parallel computing provides the NP-complete problem solved by the slime mold computer. The possibility to solve the problem by giving neither all possible results nor explicit prescription of solution-seeking is discussed. In slime mold computing, the distributivity in the local computing logic can change dynamically, and its parallel non-distributed computing cannot be reduced into the spatial addition of multiple serial computings. The computing system based on exhaustive absence of the super-system may produce, something more than filling the vacancy. [Copyright &y& Elsevier]

The conceptual design of a variable-phase asynchronous cyclotron (VPAC) is described, which provides longitudinal bunch compression of accelerated proton or ion beams, and thus, permits high current acceleration at higher accelerator efficiency, where the possible beam losses are minimized and the accelerator''s mechanical tolerances are relaxed. Beam control is assured by the ability to independently set and vary the acceleration phase and RF voltage amplitude, the inter-cavity harmonic number and the transverse focusing strength, which considerably overcome the space charge effects in each sector and turn of the proposed cyclotron. The new accelerator concept is especially suitable to accelerate intense proton beams up to 800 MeV in energy and average beam current in the 100-mA class. All accelerator elements are based on currently available and feasible technologies. To demonstrate feasibility of design, the detailed calculations and modeling of a 10-turn VPAC prototype for the production of 25.6 MeV, 100 mA proton beam are presented and the key features of the new accelerator concept are discussed. [Copyright &y& Elsevier]

We present in this paper some new language features and constructs, that allow the joint synchronous/asynchronous programming of reactive applications, as well as their formal verification. We show that reactive applications may be dealt with from two points of view. First, from the chronological point of view, i.e., when reactions are instantaneous, generated by event occurrences in discrete time. Second, from the chronometrical point of view, when reactions have durations in dense time. This duality must be expressible in languages that allow a consistent programming of both synchronous and asynchronous features. The objective of mixing these dual approaches leads to model reactive systems by using hybrid systems, to deal simultaneously with both discrete and continuous phenomena. Furthermore, this must be followed by some verification of the application's properties, with respect to its behavioural and quantitative features. We analyze several existing frameworks that meet these requirements, and propose our own approach based on the language E lectre. [ABSTRACT FROM AUTHOR]

Under natural conditions in the course of gametogenesis, the asynchronism in oocyte development in fish ovaries is observed on early stages of gonad maturation and mostly in species with batch spawning. When investigating gametogenesis in sterlet under conditions of a warm-water farm (Konakovsky sturgeon farm), rather uniform development of gametes is noted; asynchronism occurs in separate individuals and also in fishes grown under conditions of recirculating aquaculture system (RAS) at a constant high water temperature. [ABSTRACT FROM AUTHOR]

• Vinegar residue was used to pretreat corn stover instead of chemical reagent. • Vinegar residue enhanced the hydrolysis of lignocellulose in corn stover. • Methane yield was enhanced by 35.7% using vinegar residue pretreatment at 150 °C. • Pretreatment and co-digestion could improve asynchronism and generate synergism. • Butyrate acid fermentation was contributed more to biomethane production. A novel method was advanced for efficient anaerobic co-digestion by using fresh vinegar residue (FVR) as acidifier for pretreating corn stover (CS). FVR acted as one substrate as well as an acidifier by the acids contained in FVR. It was found that the organic acids in FVR could efficiently enhance the hydrolysis of lignocellulose in CS. The biomethane production from co-digestion of FVR and CS pretreated reached 140.48 L/kg VS, which was 35.7% higher than that of unpretreated mixture substrates. The highest biomethane production was obtained when pretreatment was conducted at 150 °C. The increase of biomethane production was contributed to the improved hydrolysis of CS due to the acidic pretreatment. Pretreatment and co-digestion could improve the asynchronism and generate synergistic effect. The study provides one novel method for efficient biomethane conversion from FVR and CS. [ABSTRACT FROM AUTHOR]