Impulse Gain Research Articles

Synchronization control of partial-state-based neural networks: Event-triggered impulsive control with distributed actuation delay

Within the framework of event-triggered impulsive control (ETIC), this paper delves into the synchronization of partial-state-based neural networks, meticulously considering the distributed actuation delay inherent to ETIC. By seamlessly integrating the Lyapunov-Razumikhin (L-R) technique with a dimension extension method, we articulate sufficient conditions for achieving synchronization in partially measurable states through linear matrix inequalities (LMIs), all while effectively circumventing Zeno behavior. Furthermore, an innovative partial-state-based event-triggered mechanism (ETC) is conceived to address network challenges arising from distributed actuation delay, incorporating a forced triggering strategy to ensure synchronization. Additionally, at each impulse instant, unmeasurable states can be elegantly complemented by their measurable counterparts through the design of an appropriate impulse gain matrix, without imposing any constraints on the number of unmeasurable states. Ultimately, two illustrative examples serve to underscore the efficacy of our principal findings.

Global finite-time synchronization for fractional complex network via impulsive control based on a new finite-time stability result

This paper focuses on the finite-time stability (FTS) issue for fractional nonlinear impulsive systems (FNISs). By applying Lyapunov functional approach and fractional calculus, a novel result with respect to the FTS is developed, where stabilizing impulse and destabilizing impulse are introduced in systems simultaneously. The settling time (ST), which is related to the impulse numbers, the impulse gain and the order of systems, is calculated accurately. Moreover, the proposed theoretical results are applied to derive the global finite-time synchronization (GFS) conditions for fractional-order complex dynamic network (FCDNs) under hybrid impulse effects. Finally, a simulation example is provided to substantiate the validity of the obtained results.

Video head impulse gain is impaired in myotonic dystrophy types 1 and 2.

This study was undertaken to examine vestibulo-ocular reflex (VOR) characteristics in myotonic dystrophy type 1 (DM1) and type 2 (DM2) using video head impulse testing (vHIT). VOR gain, refixation saccade prevalence, first saccade amplitude, onset latency, peak velocity, and duration were compared in DM1, DM2, age-matched normal controls, and patients with peripheral and central vestibulopathies. Fifty percent of DM1 and 37.5% of DM2 patients demonstrated reduced VOR gain. Refixation saccade prevalence for horizontal canal (HC) and posterior canal (PC) was significantly higher in DM1 (101 ± 42%, 82 ± 47%) and DM2 (70 ± 45%, 61 ± 38%) compared to controls (40 ± 28% and 43 ± 33%, p < 0.05). The first saccade amplitudes and peak velocities were higher in HC and PC planes in DM1 and DM2 compared to controls (p < 0.05). HC slow phase eye velocity profiles in DM1 showed delayed peaks. The asymmetry ratio, which represents the percentage difference between the first and second halves of the slow phase eye velocity response, was therefore negative (-22.5 ± 17%, -2.3 ± 16%, and - 4.7 ± 8% in DM1, DM2, and controls). HC VOR gains were lower and gain asymmetry ratio was larger and negative in patients with DM1 with moderate to severe ptosis and a history of imbalance and falls compared to the remaining DM1 patients (p < 0.05). In peripheral vestibulopathies, saccade amplitude was larger, peak velocity was higher, and onset latency was shorter (p < 0.05) than in DM1. In central vestibulopathy (posterior circulation strokes), saccade peak velocity was higher, but amplitude and onset latency were not significantly different from DM1. VOR impairment is common in DM1 and DM2. In DM1, refixation saccade characteristics are closer to central than peripheral vestibulopathies. Delayed peaks in the vHIT eye velocity profile observed in patients with DM1 may reflect extraocular muscle weakness. VOR impairment and VOR asymmetry in DM1 are associated with imbalance and falls.

Asymptotic Synchronization for Caputo Fractional-Order Time-Delayed Cellar Neural Networks with Multiple Fuzzy Operators and Partial Uncertainties via Mixed Impulsive Feedback Control

To construct Caputo fractional-order time-delayed cellar neural networks (FOTDCNNs) that characterize real environments, this article introduces partial uncertainties, fuzzy operators, and nonlinear activation functions into the network models. Specifically, both the fuzzy AND operator and the fuzzy OR operator are contemplated in the master–slave systems. In response to the properties of the considered cellar neural networks (NNs), this article designs a new class of mixed control protocols that utilize both the error feedback information of systems and the sampling information of impulse moments to achieve network synchronization tasks. This approach overcomes the interference of time delays and uncertainties on network stability. By integrating the fractional-order comparison principle, fractional-order stability theory, and hybrid control schemes, readily verifiable asymptotic synchronization conditions for the studied fuzzy cellar NNs are established, and the range of system parameters is determined. Unlike previous results, the impulse gain spectrum considered in this study is no longer confined to a local interval (−2,0) and can be extended to almost the entire real number domain. This spectrum extension relaxes the synchronization conditions, ensuring a broader applicability of the proposed control schemes.

Non-pilot based carrier frequency offset estimation and reflection coefficient optimization for RIS-assisted OFDM systems

Carrier frequency synchronization between the transmitter and receiver is challenging due to oscillator inaccuracies and Doppler shifts, which lead to inter-carrier interference. To address this synchronization error, i.e., carrier frequency offset (CFO), we introduce a novel method for estimating the CFO in reconfigurable intelligent surfaces (RIS)-assisted orthogonal frequency division multiplexing (OFDM) systems. Additionally, we present a method to optimize reflection coefficients, as adjusting the reflection coefficient of RIS can effectively manipulate signal propagation and amplitude, thereby enhancing system performance. In the proposed method, a randomized set of reflection coefficients is applied for the first OFDM symbol, and CFO is estimated using the oversampling method within that symbol over the Rayleigh fading environment. A deterministic approach is adopted to reduce grid search complexity. Simulation results demonstrate the superior performance of the proposed CFO estimation method, particularly in high signal-to-noise ratio scenarios, compared to the existing Zadoff Chu sequence-based estimator in terms of mean square error (MSE). Subsequently, the CFO is compensated in the second OFDM symbol using the estimated CFO, and the reflection coefficient is optimized by identifying the channel tap associated with the maximum channel impulse gain technique. The optimized reflection coefficient enhances system performance in terms of bit error rate (BER) for RIS-assisted OFDM systems.

Event-Triggered Impulsive Control for Input-to-State Stabilization of Nonlinear Time-Delay Systems.

This article investigates the event-triggered impulsive control (ETIC) problem for a class of nonlinear time-delay systems subject to exogenous disturbances. An original event-triggered mechanism (ETM) which utilizes the information of system state and external input is constructed based on Lyapunov function approach. To achieve the input-to-state stability (ISS) of the considered system, some sufficient conditions are presented, in which the underlying relationship among ETM, exogenous input, and impulse action is established. Furthermore, the possible Zeno behavior induced by the proposed ETM is excluded simultaneously. As an application, the design criterion of ETM and impulse gain is put forward for a class of impulsive control systems with delay according to the feasibility of some linear matrix inequalities (LMIs). Finally, two examples with numerical simulations are provided to confirm the effectiveness of the developed theoretical results, where the synchronization issue of delayed Chua's circuit is considered.

Experimental and numerical study on RBCC engines performance in simultaneous and combustion cycle

The simultaneous mixing and combustion (SMC) cycle is a simple yet effective approach to augment the specific impulse of rocket-based combined cycle (RBCC) engines in ejector mode. However, the thrust performance of RBCC engines in the SMC cycle has not been adequately explored. This study investigates the effects of the flight Mach number, mixer shapes, and mixture ratio (MR) on the thrust performance of an axisymmetric kerosene-fueled RBCC engine. Ground free-suction experiments were conducted, employing a supersonic air ejector to simulate varying flight backpressures. Wall pressure distributions and axial thrusts were obtained. To eliminate undesirable interactions between MRs and backpressures inherent in experiments, numerical simulations were performed. The experimental results show that as flight Mach number increases, specific impulse improves rapidly, and specific impulse augmentation is achieved in the transonic regime. Simulations conducted at H4.0km/Mach0.88 with the expansion mixer reveal that as MR decreases, both mixing efficiency and combustion intensity increase. The balance between specific impulse gain from the secondary stream and loss from the primary stream is achieved at MR = 2.2, with the highest specific impulse being achieved at MR = 2.0. These insights provide valuable guidance for advancing the development of more efficient RBCC engines using the SMC cycle.

The semicircular canal function is preserved with little impact on falls in patients with mild Parkinson's disease

IntroductionPostural instability is a cardinal symptom of Parkinson's disease (PD), which suggests the vestibular system may be affected in PD. This study aimed to determine whether vestibular dysfunction is associated with the risk of falls in PD. MethodsWe prospectively recruited patients with de-novo PD at a tertiary medical center between December 2019 and March 2023. During initial assessment, each patient was queried about falls within the preceding year. All patients underwent evaluation of video head-impulse tests (video-HITs), motion analysis, mini-mental state examination (MMSE), and Montreal Cognitive Assessment (MOCA). We determined whether head impulse gain of the vestibulo-ocular reflex (VOR) was associated with clinical severity of PD or risk of falls. ResultsOverall, 133 patients (mean age ± SD = 68 ± 10, 59 men) were recruited. The median Movement Disorder Society-Unified Parkinson's Disease Rating Scale motor part (MDS-UPDRS-III) was 23 (interquartile range = 16–31), and 81 patients (61 %) scored 2 or less on the Hoehn and Yahr scale. Fallers were older (p = 0.001), had longer disease duration (p = 0.001), slower gait velocity (p = 0.009), higher MDS-UPDRS-III (p < 0.001) and H&Y scale (p < 0.001), lower MMSE (p = 0.018) and MOCA scores (p = 0.001) than non-fallers. Multiple logistic regression showed that MDS-UPDRS-III had a positive association with falling (p = 0.004). Falling was not associated with VOR gain (p = 0.405). The VOR gain for each semicircular canal showed no correlation with the MDS-UPDRS-III or disease duration. ConclusionsThe semicircular canal function, as determined by video-HITs, is relatively spared and has little effect on the risk of falls in patients with mild-to-moderate PD.

Stability of stochastic systems with semi-Markovian switching and impulses

The aim of this paper is to investigate the stochastic asymptotic stability of semi-Markov switched systems with mixed impulses. A novel definition of average impulse gain is given to estimate the intensity of the mixed impulses. Based on the multiple Lyapunov function approach and average impulse interval method, we provide sufficient conditions on the stochastic asymptotic stability for the semi-Markov switched system with impulses. Moreover, the influence of impulses on the system is estimated by applying the average impulse gain and average impulse interval method, which are not only suitable for synchronous impulses but also for asynchronous impulses. The theoretical results are demonstrated by two examples.

Direction-of-arrival estimation for a nested array with gain-phase error and impulse noise

To solve direction-finding problems for nested arrays under conditions of impulse noise and gain–phase errors, this paper proposes a direction-of-arrival (DOA) estimation method. First, a correntropy with an adaptive kernel length combined with an infinite norm of a variable weight value is proposed to suppress impulse noise. Then, the auxiliary array elements are used to realize the initial calibration of the amplitude and phase errors. On this basis, a DOA estimation method without a spectral peak search is proposed; this method is robust for arrays that still have residual gain–phase errors after calibration. Our method overcomes the difficulties of DOA estimation for nested arrays under conditions of gain–phase errors and impulse noise. Compared with traditional methods, the proposed method does not require prior knowledge, does not require a spectral peak search and has high superiority and robustness; a series of experiments have verified its superiority. In addition, a Cramér‒Rao bound (CRB) for angle estimation under conditions of gain–phase errors and impulse noise is proposed in this paper.

Exponential stability of time‐delay systems with flexible delayed impulse

AbstractThe problem of exponential stability for time‐delay systems with flexible delayed impulse control is investigated. Unlike the conventional Razumikhin‐type inequality, variable parameter based on the flexible impulsive gain is introduced. Sufficient conditions for exponential stability are developed for a class of time‐delay systems, for which the size of delay is not limited by impulsive intervals. A flexible impulse control scheme is developed by utilizing the flexible impulsive gain and time‐varying delays. When the system is disturbed by the impulse interferences, both the impulse gain and impulse delay can be adjusted accordingly to make the system exponential stable. The effectiveness of the present results is illustrated by two numerical examples and an application.

Designing Distributed Impulsive Controller for Networked Singularly Perturbed Systems

This paper develops a novel synthesis approach for synchronization of a network of singularly perturbed systems (SPSs) with a small singular perturbation parameter (SPP) <inline-formula><tex-math notation="LaTeX">$\varepsilon$</tex-math></inline-formula> via distributed impulsive control. First, a decoupling method in the setting of directed networks is employed to decompose networked SPSs related to complex eigenvalues of the Laplacian matrix. Then, based on an improved piecewise continuous Lyapunov function, an <inline-formula><tex-math notation="LaTeX">$\varepsilon$</tex-math></inline-formula>-dependent synchronization criterion is established. The relationship among the impulse interval, the impulse gain matrix and <inline-formula><tex-math notation="LaTeX">$\varepsilon$</tex-math></inline-formula> is revealed. By employing the newly-obtained synchronization criterion, sufficient conditions on the existence of an <inline-formula><tex-math notation="LaTeX">$\varepsilon$</tex-math></inline-formula>-dependent impulse gain matrix are derived. Finally, an example is simulated to verify the effectiveness of the theoretical results.

Unidirectional Vertical Vestibuloocular Reflex Adaptation in Humans Using 1D and 2D Scenes.

The vertical vestibuloocular reflex (VOR) in response to pitch head impulses can be optimally trained to increase in one direction using a two-dimensional (2D) visual training target with minimal effect on the horizontal VOR. We modified the incremental VOR adaptation (IVA) technique, shown to increase the horizontal VOR in patients with vestibular hypofunction, to drive vertical VOR adaptation in healthy control subjects. We measured the horizontal and vertical active (self-generated) and passive (imposed) head impulse VOR gains (eye velocity/head velocity) before and after 15 minutes of unidirectional downward IVA training. IVA training consisted of two sessions, one using a single-dot one-dimensional (1D) target, the other a grid-of-dots 2D target. The downward head impulse VOR gain significantly increased because of training by 13.3%, whereas the upward VOR gain did not change. The addition of extraretinal (2D) feedback did not result in greater adaptation, i.e., 1D and 2D gain increases were 15.5% and 10.6%, respectively. The vertical VOR gain increase resulted in a 3.2% decrease in horizontal VOR gain. This preliminary study is the first to show that physiologically relevant (high frequency) unidirectional increases in vertical VOR gain are possible with just 15 minutes of training. This study sets the basis for future clinical trials examining vertical IVA training in patients, which may provide the first practical rehabilitation treatment to functionally improve the vertical VOR.

A Method to Evaluate the Performance of Ultra-Wideband Antennas for the Radiation of High-Power Electromagnetic Pulses

In this communication, a time-frequency joint method is proposed to evaluate the performance of ultrawideband (UWB) antennas for the radiation of high-power (HP) electromagnetic pulses. First, conventional antenna parameters, such as the efficiency, gain, and so on, are translated to UWB pulsed antennas from the energy perspective, so as to get several scalar antenna parameters, since energy in one pulse is finite. Thus, the power-spectrum weighted efficiency ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\eta _{e}$ </tex-math></inline-formula> ), directivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D_{e}$ </tex-math></inline-formula> ), and gain ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$G_{e}$ </tex-math></inline-formula> ) are proposed. Then, several electromagnetic norms of the radiating pulse are selected to characterize the sensitive parameters of the equipment under test (EUT). Based on these, several other scalar antenna parameters are proposed, which are the effective potential gain ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$G_{ep}$ </tex-math></inline-formula> ), pulse sharpening factor ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PSF</i> ), and peaking impulse gain ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$G_{PI}$ </tex-math></inline-formula> ). Thus, a set of time-domain scalar criteria are proposed to evaluate the performance of HP-UWB antennas. These criteria can be calculated with the frequency functions of conventional antenna parameters, which demonstrate the inherent properties of one antenna. Finally, the performance of two kinds of typical HP-UWB antennas, namely the impulse radiating antenna and the combined antenna, is measured and compared with the proposed method. It indicates that, with the proposed method, one can not only get the inherent properties of one antenna in the frequency domain but also quantitatively compare the performance of different antennas with a given exciting pulse in the time domain with the proposed scalar antenna parameters.

Impulsive cluster synchronization for complex dynamical networks with packet loss and parameters mismatch

This paper investigates the cluster synchronization (CS) for a class of complex dynamical networks (CDNs) with parameters mismatch to the selected cluster pattern. An impulsive control strategy with multiple control gains is proposed. Particularly, the possible packet loss phenomenon in control input is fully considered, and it is characterized by a series of impulse packet loss rate (iPLR) conditions. In terms of the reverse average dwell time (rADT) condition and the average impulse gain method, some sufficient conditions guaranteing that all the nodes of CDNs can be synchronized to their cluster sets are derived, from which the constraint relationships among rate coefficients, impulsive control law, and iPLR can be revealed. Finally, an example is given to illustrate the correctiveness of our results.

Does vestibular loss result in cognitive deficits in children with cochlear implants?

In adults, vestibular loss is associated with cognitive deficits; however, similar relationships have not been studied in children. Evaluate the effect of vestibular loss on working memory and executive function in children with a cochlear implant (CCI) compared to children with normal hearing (CNH). Vestibular evoked myogenic potential, video head impulse, rotary chair, and balance testing; and the following clinical measures: vision, hearing, speech perception, language, executive function, and working memory. Thirty-eight CNH and 37 CCI participated (26 with normal vestibular function, 5 with unilateral vestibular loss, 6 with bilateral vestibular loss). Children with vestibular loss demonstrated the poorest balance performance. There was no significant reduction in working memory or executive function performance for either CCI group with vestibular loss; however, multivariate regression analysis suggested balance performance was a significant predictor for several working memory subtests and video head impulse gain was a significant predictor for one executive function outcome. CCI with vestibular loss did not have significantly reduced working memory or executive function; however, balance performance was a significant predictor for several working memory subtests. Degree of hearing loss should be considered, and larger sample sizes are needed.

Adaptive treadmill control can be manipulated to increase propulsive impulse while maintaining walking speed

Adaptive treadmills (ATM) designed to promote increased propulsion may be an effective tool for gait training since propulsion is often impaired post-stroke. Our lab developed a novel ATM controller that adjusts belt speed via real-time changes in step length, propulsive impulse, and position. This study modified the relative importance of propulsion to step length in the controller to determine the effect of increased propulsive feedback gain on measures of propulsion and walking speed. Twenty-two participants completed five trials at their self-selected speed, each with a unique ATM controller. Walking speed, peak AGRF and PGRF, and AGRF, PGRF, and net impulse were compared between the modifications using one-way repeated measures ANOVAs at a significance level of 0.05. Participants chose similar walking speeds across all conditions (all p > 0.2730). There were no significant differences in peak AGRF (p = 0.1956) or PGRF (p = 0.5159) between conditions. AGRF impulse significantly increased as the gain on the propulsive impulse term was increased relative to the gain on step length (p < 0.0001) while PGRF and net impulse were similar across all conditions (p = 0.5487). Increasing the propulsive impulse gain essentially alters the treadmill environment by providing a controlled amount of resistance to increases in propulsive forces. Our findings demonstrate that the ATM can be modified to promote increased propulsive impulse while maintaining a consistent walking speed. Since increasing propulsion is a common goal of post-stroke gait training, these ATM modifications may improve the efficacy of the ATM for gait rehabilitation.

Ictal downbeat nystagmus in Ménière disease: A cross-sectional study.

To determine the mechanism of ictal downbeat nystagmus in Ménière disease (MD), we compared the head impulse gain of the vestibulo-ocular reflex (VOR) for each semicircular canal between patients with (n = 7) and without (n = 70) downbeat nystagmus during attacks of MD. We retrospectively analyzed the results of video-oculography, video head-impulse tests, and cervical vestibular-evoked myogenic potentials (VEMPs) in 77 patients with definite MD who were evaluated during an attack. Pure or predominant downbeat nystagmus was observed in 7 patients (9%) with unilateral MD during the attacks. All 7 patients showed spontaneous downbeat nystagmus without visual fixation with a slow phase velocity ranging from 1.5 to 11.2°/s (median 5.4, interquartile range 3.7-8.5). All showed a transient decrease of the head impulse VOR gains for the posterior canals (PCs) in both ears (n = 4) or in the affected ear (n = 3). Cervical VEMPs were decreased in the affected (n = 2) or both ears (n = 2) when evaluated during the attacks. Downbeat nystagmus disappeared along with normalization of the VOR gains for PCs after the attacks in all patients. During the attacks, the head impulse VOR gains for the PC on the affected side were lower in the patients with ictal downbeat nystagmus than in those without (Mann-Whitney U test, p < 0.001), while the gains for other semicircular canals did not differ between the groups. Downbeat nystagmus may be observed during attacks of MD due to an asymmetry in the vertical VOR or saccular dysfunction. MD should be considered in recurrent audiovestibulopathy and ictal downbeat nystagmus.

Global [formula omitted]-synchronization of impulsive pantograph neural networks

This paper investigates the problem of global μ-synchronization of impulsive pantograph neural networks. In this paper, new concept of ν-asymptotic periodic impulsive interval Tasyν is proposed for pantograph networks. By employing the Lyapunov method combined with the mathematical analysis approach for impulsive systems, some useful criteria are derived to guarantee the global μ-synchronization of coupled pantograph neural networks when the asymptotic logarithmic periodic impulsive interval Tasyln<∞ and Tasyln=∞, respectively. Especially when Tasyln=∞, as long as the networks are unstable, impulsive control cannot achieve synchronization regardless of the size of the impulse gain. Numerical simulations are exploited to illustrate our theoretical results.

Evolution in the Findings of Head-Impulse Tests During the Attacks of Menière's Disease.

To determine the vestibulo-ocular reflex (VOR) performance during the attacks of Menière's disease (MD) using video head-impulse tests (video-HITs) according to each ictal phase. Retrospective case series review. We analyzed the results of video-HITs in 24 patients with unilateral definite MD during and between the attacks. The head impulse gain of the VOR was usually normal (81%, 39 of the 48 semicircular canals [SCCs] in 16 patients) in the affected ear during the irritative or recovery phase, and did not differ from that for each SCC between the attacks (horizontal [HCs], p = 0.412; anterior [ACs], p = 0.920; posterior canals [PCs], p = 0.477). During the paretic phase, however, the head impulse gains of the VOR were equally normal (22/42, 52%) or decreased (20/42, 48%) for the affected ear (42 SCCs in 14 patients). The gains for the HCs were lower during the paretic phase than those between the attacks in the affected ear, while those for the ACs and PCs did not differ (HCs, p = 0.001; ACs, p = 0.158, PCs, p = 0.401). Covert saccades were more frequently observed even in the presence of normal VOR gains during the paretic phase as well. During the attacks of MD, HITs are usually normal during the irritative/recovery phases, but become positive in more than a half of the patients during the paretic phase. This evolution in the ictal findings of HITs may reflect characteristic ictal vestibular discharges in MD and should be considered in evaluating patients with MD according to each ictal phase during the attacks.