Occurrence Of Impulses Research Articles

A review on the surface topography and corrosion behavior of Mg-alloy coatings for biomedical implants

Osteoconductive, biocompatible, and biodegradable magnesium alloys hold great promise as novel materials for orthopaedic and vascular implants due to their bone-like mechanical properties. Furthermore, their limited utility in therapeutic environments is compounded by their inadequate resistance to corrosion. Because the impulsive occurrence of corrosion in magnesium alloys is governed by the loss of properties, including the materials' fundamental properties and various corrosive conditions, the corrosion mechanism is extremely complex. Due to the incidence of numerous factors, including the materials' inherent properties and the presence of various corrosive environments, the corrosion mechanism of magnesium alloys is complexity-ridden.

Approximate controllability of second-order neutral stochastic differential evolution systems with random impulsive effect and state-dependent delay

<p>In this paper, we have discussed a class of second-order neutral stochastic differential evolution systems, based on the Wiener process, with random impulses and state-dependent delay. The system is an extension of impulsive stochastic differential equations, since its random effect is not only from stochastic disturbances but also from the random sequence of the impulse occurrence time. By using the cosine operator semigroup theory, stochastic analysis theorem, and the measure of noncompactness, the existence of solutions was obtained. Then, giving appropriate assumptions, the approximate controllability of the considered system was inferred. Finally, two examples were given to illustrate the effectiveness of our work.</p>

Stability Analysis for Impulsive Stochastic Time-Varying Systems

The average impulsive interval is widely used to describe the frequency of impulsive occurrence (FIO), where the occurrence number of impulses is bounded by a linear function of time interval length. However, the linear relationship may insufficiently or excessively characterize the occurrence number of impulses to stabilize impulsive time-varying systems. In this article, the impulsive density is introduced to describe a time-varying FIO, such that the occurrence number of impulses can be characterized more explicitly. Under the impulsive density, the asymptotical stability is considered for impulsive stochastic time-varying systems, where the continuous dynamics of systems, impulsive strengths, and instants are all assumed to be time-varying. In addition, the exponential stability is also investigated for impulsive stochastic time-varying systems with time-delay, which can extend some existing results. Two examples, including one example of the consensus for impulsive time-varying multiagent systems with time-delay, are presented to demonstrate the effectiveness of the proposed results.

Improved Input-to-State Stability Analysis of Impulsive Stochastic Systems

This article is concerned with the input-to-state stability (ISS) and stochastic input-to-state stability (SISS) of impulsive stochastic nonlinear systems. By constructing a general SISS-Lyapunov function, which takes the exponential SISS-Lyapunov function as a special case, the ISS criteria are obtained, respectively, for destabilizing and stabilizing impulses. It should be stressed that we impose the average dwell-time (ADT) condition for destabilizing impulses and reverse average dwell-time (RADT) condition for stabilizing impulses to restrain the occurrence of impulses, which extends the fixed dwell-time condition in recent literature. Moreover, the ADT and RADT conditions in this article correspond to the average impulsive interval method in most existing results under the exponential ISS-Lyapunov condition. As a subsequent result, the ISS and SISS of impulsive stochastic interconnected systems on networks are also studied by the Lyapunov method and graph-theoretic technique. Finally, several illustrative examples together with their numerical simulations are provided to demonstrate the theoretical results.

Fixed-time and state-dependent time discontinuities in the theory of Stieltjes differential equations

In the present paper, we are concerned with a very general problem, namely the Stieltjes differential Cauchy problem involving state-dependent discontinuities. Given that the theory of Stieltjes differential equations covers the framework of impulsive problems with fixed-time impulses, in the present work we generalize this setting by allowing the occurrence of fixed-time impulses, as well as the occurrence of state-dependent impulses. Along with an existence result obtained under an overarching set of assumptions involving Stieltjes integrals, it is showed that a least and a greatest solution can be found.

МОДЕЛИРОВАНИЕ ИМПУЛЬСА ЧАСТИЧНОГО РАЗРЯДА В ЦЕПИ ЗАЗЕМЛЕНИЯ СИЛОВОГО КАБЕЛЯ

The paper describes the modeling of a partial discharge (PD) pulse in the grounding circuit of power cables in order to evaluate the effectiveness of using a low-resistance resistive element for registering par-tial discharges. Three possible options for constructing the model are considered. The first is based on the classical method for calculating transients. A system of differential equations was compiled, corresponding to the compiled scheme for the occurrence of PD impulses. The system was then solved using the Matlab software package. The Simscape Electrical module built into Matlab/Simulink was chosen as the second option for build-ing the model. A scheme for the occurrence of a partial discharge was drawn up, initial conditions were set, and a solution was made. The third option for constructing the model was a computer model of an electrical circuit using a calibration generator. All three constructed models showed similar simulation results for a PD pulse cor-responding to 3 nC. As a result, it was determined that the resistive element can be used to register partial dis-charges. However, possible registration problems can be interference in the enterprise network. However, it is assumed that dangerous levels of partial discharges can be recorded even in the presence of interference.

Decoding a Music-Modulated Cognitive Arousal State using Electrodermal Activity and Functional Near-infrared Spectroscopy Measurements.

Biofeedback systems sense different physiological activities and help with gaining self-awareness. Understanding music's impact on the arousal state is of great importance for biofeedback stress management systems. In this study, we investigate a cognitive-stress-related arousal state modulated by different types of music. During our experiments, each subject was presented with neurological stimuli that elicit a cognitive-stress-related arousal response in a working memory experiment. Moreover, this cognitive-stress-related arousal was modulated by calming and vexing music played in the background. Electrodermal activity and functional near-infrared spectroscopy (fNIRS) measurements both contain information related to cognitive arousal and were collected in our study. By considering various fNIRS features, we selected three features based on variance, root mean square, and local fNIRS peaks as the most informative fNIRS observations in terms of cognitive arousal. The rate of neural impulse occurrence underlying EDA was taken as a binary observation. To retain a low computational complexity for our decoder and select the best fNIRS-based observations, two features were chosen as fNIRS-based observations at a time. A decoder based on one binary and two continuous observations was utilized to estimate the hidden cognitive-stress-related arousal state. This was done by using a Bayesian filtering approach within an expectation-maximization framework. Our results indicate that the decoded cognitive arousal modulated by vexing music was higher than calming music. Among the three fNIRS observations selected, a combination of observations based on root mean square and local fNIRS peaks resulted in the best decoded states for our experimental settings. This study serves as a proof of concept for utilizing fNIRS and EDA measurements to develop a low-dimensional decoder for tracking cognitive-stress-related arousal levels.

Problematic Internet use (PIU), personality profiles and emotion dysregulation in a cohort of young adults: trajectories from risky behaviors to addiction

Problematic Internet Use (PIU) encloses excessive online activities (like video gaming, social media use, web-streaming, pornography viewing, buying). Despite its psychological burden, risk factors related to PIU remain still unclear. In the present study we explored the role of personality traits and emotion dysregulation as potential vulnerability factors for PIU. In a sample of American young adults with different PIU risk levels (established through the Internet Addiction Diagnostic Questionnaire), we administered the Tridimensional Personality Questionnaire (TPQ), the Difficulties in Emotion Regulation Scale (DERS), the Barratt Impulsiveness Scale, the Hamilton Depression Rating Scale, the Hamilton Anxiety Rating Scale. PIU participants were more likely to report lower TPQ scores in novelty seeking, harm avoidance and reward dependence. Moreover, DERS total scores significantly differed across PIU-risk groups, along with a progressively higher occurrence of depression, anxiety and impulsivity. These results preliminarily support the hypothesis of PIU as a mainly behavior aimed at ‘escaping’ from negative affects. Besides confirming the role of some personality traits and emotional dysregulation, we propose the concept of risk-trajectories to monitor and prevent the emergence of PIU. Gaining more insight into PIU vulnerability factors may allow us to establish targeted interventions to cope with emotion dysregulation and negative affects.

Effects of infinite occurrence of hybrid impulses with quasi-synchronization of parameter mismatched neural networks

This article is deeply concerned with the effects of hybrid impulses on quasi-synchronization of neural networks with mixed time-varying delays and parameter mismatches. Hybrid impulses allow synchronizing as well as desynchronizing impulses in one impulsive sequence, so their infinite time occurrence with the system may destroy the synchronization process. Therefore, the effective hybrid impulsive controller has been designed to deal with the difficulties in achieving the quasi-synchronization under the effects of hybrid impulses, which occur all the time, but their density of occurrence gradually decrease. In addition, the new concepts of average impulsive interval and average impulsive gain have been applied to cope with the simultaneous existence of synchronizing and desynchronizing impulses. Based on the Lyapunov method together with the extended comparison principle and the formula of variation of parameters for mixed time-varying delayed impulsive system, the delay-dependent sufficient criteria of quasi-synchronization have been derived for two separate cases, viz., Ta<∞ and Ta=∞. Finally, the efficiency of the theoretical results has been illustrated by providing two numerical examples.

Delay-Dependent Impulsive Distributed Synchronization of Stochastic Complex Dynamical Networks With Time-Varying Delays

This paper studies the problem of synchronization for a class of stochastic complex dynamical networks. It designs for the first time a distributed impulsive protocol based on pinning control that involves a constant signal transmission delay to tackle synchronization issues of such networks. Novel criteria on network synchronization are established by employing a time-dependent Lyapunov functional and a mathematical induction approach, where information on the state variables themselves and their neighbors is sufficiently utilized. Moreover, it is shown that the frequency of impulsive occurrence, impulsive input delays, stochastic perturbations, and the feedback control strength can significantly affect the synchronization performance. Numerical simulations are given to illustrate the effectiveness of the derived theoretical results.

O suicídio de idosos em Teresina: fragmentos de autópsias psicossociais

This study aims to discuss about the circumstances that involved the suicide of elderly people that occurred in Teresina city, PI. It is a qualitative, descriptive, exploratory study made through psychosocial autopsies of five suicidal cases of elderly people. Thereunto, it was investigated retrospectively the life of these subjects, by interviews with relatives who lived nearby the victims. The method used has grouped three types of instruments: personal and social identification form of the elder, genogram and semi structured interview. The stories were analyzed qualitatively, reconstructed taking as a guide the principles of hermeneutical-dialectic. It has been observed that the outstanding presence of some risk circumstances associated to the investigated suicides, which there were fragile affective relationships, meaningless life, depression, abuse of alcohol, aggressive impulsive personality traits and occurrence of previous suicide attempts.

Design and Performance Analysis of Power Line Communication Networks Under Impulsive Noise in Smart Home

Power line communication (PLC) is an attractive approach to provide information transfer services for the smart home. The PLC network inherently suffers from the severe channel fading and impulsive noise. According to the mode of impulsive and the impulsive occurrence, the PLC channel can be modeled as the channel with memory. We compute the achievable rate by employing the Markov process with a finite number of states based on the dependence among the impulsive occurrence numbers in different time slots. Furthermore, the cumulative distribution function (CDF) for the received signal-to-noise ratio is derived with the statistical characteristics of the PLC channel. This helps in obtaining the ergodic capacity and outage probability for the PLC channels. We finally present the simulation results to verify the analytical results.

Fault detection of a wheelset bearing in a high-speed train using the shock-response convolutional sparse-coding technique

The wheelset bearing is an essential mechanical component of a high-speed train, and its fault detection is of great importance for ensuring the safety of high-speed train service. However, the strong nonlinear and non-stationary modulation characteristics of the impulses induced by bearing faults, noises and interferences make fault detection of the wheelset bearing difficult and complex. The impulses induced by bearing faults have convolutional sparse characteristics, and can be described as the convolution of shock responses and time location coefficients. This paper presents a new fault detection method based on the shock-response convolutional sparse-coding technique (SRCSCT) to resolve the two inverse problems related to convolution characteristics. One of the problems is that shock responses are learned directly from vibration signals via the shift-invariant dictionary learning (SIDL) of SRCSCT; the other is that the time location coefficients are inferred from vibration signals via shift-invariant sparse coding (SISC) of SRCSCT. Shock responses can reflect the high-level structures of impulses embedded in vibration signals. Time location coefficients can be used to determine the time of impulse occurrence. The convolutions of learned shock responses and inferred corresponding time location coefficients are used to extract impulses submerged in vibration signals and are convenient for post-processing methods, such as Hilbert envelope analysis. Both the simulated signals and real vibration signals collected from a wheelset bearing test bench are used to verify the proposed method. The results show that SRCSCT not only effectively detects faults of the wheelset bearing but also accurately characterizes the fault dynamic behaviours of the bearing defects.

Synchronization of nonlinear complex dynamical systems via delayed impulsive distributed control

This paper investigates the exponential synchronization problem of nonlinear complex dynamical systems via delayed impulsive distributed control. Different from the existing results on the synchronization of complex dynamical systems, impulsive input delays are considered in our model. Combined with the time-varying Lyapunov functional and mathematical induction approaches, criteria on system synchronization are established, which sufficiently utilize the information of both the state variables of themselves and their neighbors. Moreover, it is shown that the frequency of impulsive occurrence and impulsive input delays can heavily affect the synchronization performance. Finally, two numerical simulations are given to illustrate the effectiveness of the derived theoretical results.

Path integral solution for nonlinear systems under parametric Poissonian white noise input

In this paper the problem of the response evaluation in terms of probability density function of nonlinear systems under parametric Poisson white noise is addressed. Specifically, extension of the Path Integral method to this kind of systems is introduced. Such systems exhibit a jump at each impulse occurrence, whose value is obtained in closed form considering two general classes of nonlinear multiplicative functions. Relying on the obtained closed form relation liking the impulses amplitude distribution and the corresponding jump response of the system, the Path Integral method is extended to deal with systems driven by parametric Poissonian white noise. Several numerical applications are performed to show the accuracy of the results and comparison with pertinent Monte Carlo simulation data assesses the reliability of the proposed procedure.

Direct evaluation of jumps for nonlinear systems under external and multiplicative impulses

In this paper the problem of the response evaluation of nonlinear systems under multiplicative impulsive input is treated. Such systems exhibit a jump at each impulse occurrence, whose value cannot be predicted through the classical differential calculus. In this context here the correct jump evaluation of nonlinear systems is obtained in closed form for two general classes of nonlinear multiplicative functions. Analysis has been performed to show the different typical behaviors of the response, which in some cases could diverge or converge to zero instantaneously, depending on the amplitude of the Dirac's delta.

Differences in Impulsivity between Females Diagnosed with Eating Disorders and Healthy Subjects

Objectives: This cross-sectional study investigates the tendencies toward impulsivity and self-control over the entire spectrum of the different eating disorders in comparison to healthy and recovered subjects. Methods: The study included 116 women, aged 18-35. Participants filled seven self-report questionnaires to assess eating disorders features and tendencies toward impulsivity and self-control and two computerized tasks (Go/No Go and Cognitive Delay Discounting) to examine motoric impulsivity. Results: There was a hierarchy of occurrence of impulsivity in the different categories of eating disorders. Cognitive impulsivity as well as motor impulsivity and global score of impulsivity were most prominent in the anorexia nervosa binging type. This hierarchy was correlated with the eating disorders symptoms. The lowest score in motor impulsivity was observed among restrictive patients with anorexia and the highest among patients with binging-purging anorexia, while all other groups were in between. Those with binging-purging anorexia demonstrated significantly different behavior in short term delays: they were less willing to delay gratification in comparison to other participants who demonstrated preference for the higher delayed reward. The impulse regulation and the ineffectiveness scores of both anorextic groups were higher in comparison to the other groups. These two variables were highly correlated with attentional impulsiveness. Conclusion: These findings suggest that binging restricting behaviors may be seen as lying on opposite ends of a spectrum of impulsive behaviors. Individuals with AN-BP appear to have more in common with BN individuals as they share the tendency to display greater response Disinhibition and produce more impulsive behaviors. Since at this stage only a small sample size was analyzed these results are considered preliminary.

Synchronization of hybrid impulsive and switching dynamical networks with delayed impulses

In this paper, the exponential synchronization problem is investigated for a class of hybrid impulsive and switching dynamical networks (HISDNs). Different from the existing results concerning synchronization of HISDNs, impulsive input delays are considered in our model. Moreover, in our model, the impulsive instances and system switching instances do not need to be coincident. By using the Razumikhin theorem and the mathematical induction method, several sufficient synchronization criteria are obtained in terms of linear matrix inequalities. The obtained criteria reveal that the frequency of impulsive occurrence, impulsive input delays, can heavily affect the synchronization performance. Finally, an example is provided to illustrate the effectiveness of the obtained results.

Optimized threshold calculation for blanking nonlinearity at OFDM receivers based on impulsive noise estimation

AbstractImpulsive noise (IN) degrades the performance of OFDM-based communication systems. Performance degradation is usually measured in terms of signal-to-noise ratio (SNR) and symbol-error rate (SER). To improve the performance of the system of OFDM receivers, one of the effective methods is to use blanking nonlinearity. In this method, the samples whose magnitudes exceed a certain fixed threshold are considered to be IN-affected and are therefore blanked. A fixed threshold does not always determine the IN-affected samples truly for all probabilities of IN occurrence. This paper proposes an optimized threshold-calculation method for blanking nonlinearity which is based on distribution characteristics of the received signal, i.e., mean, median, and peak. The proposed method can calculate an optimized threshold for all probabilities of impulsive noise occurrence. Simulation results show over 2.2-dB gain in SNR and lower SER by using the proposed method as compared to fixed threshold.

Optimal Signaling Scheme and Capacity Limit of PLC Under Bernoulli-Gaussian Impulsive Noise

This paper studies the optimal signaling scheme and capacity of the Bernoulli–Gaussian impulsive noise channel to shed new light on the impact of impulsive noise on spectral efficiency of power-line communications systems. First, by focusing on the practically typical case with impulse power that is much higher than signal power, we develop a tight approximation to the differential entropy of Bernoulli–Gaussian noise. Closed-form tight lower and upper bounds on the capacity are then derived. By comparing these bounds, it is demonstrated that the capacity decreases with an increasing impulse occurrence rate and the Gaussian signaling scheme is nearly optimal. We then focus on the case with an impulse power lower than signal power to develop tight lower and upper bounds. We subsequently show that the Gaussian signaling can approach the capacity in this region as well. In addition, channel erasure is shown to be very effective for the impulsive noise channel when impulse power is higher than signal power, but it introduces rate loss when impulse power is sufficiently lower than signal power. Illustrative simulation results confirm the analytical derivations and show their applications to estimate the maximum achievable rate of a power-line communication link with practical parameters.