Internal Delay Research Articles

Stability result of Laminated beam with internal distributed delay

In this paper, we consider a laminated beams system with frictional damping and an internal distributed delay feedback on the effective rotational angle. With appropriate assumptions on the weight of the delay feedback and wave speeds, we prove that the dissipation through the frictional damping is sufficiently strong to uniformly stabilize the system even in the presence of delay.

A coalbed methane ‘stratum’ for a low-carbon future: A critical inquiry from the Lorraine Basin (France)

Coalbed methane exploration in Lorraine (France) is part of a rush to unconventional natural gas around the world. These resources are envisioned as a “transitional bridge” to a low-carbon economy dominated by renewable generation. This paper tackles the idea that such a “fuel bridge” could lead to a more sustainable transition. It studies the network of actors and interests involved in exploring a coalbed methane ‘volume’, its modelling and how it becomes public. Through this lens, it shows how a ‘volume’ endures in a ‘stratum’, as well as the political issues related to this reconfiguring of the underground in Lorraine.The article contributes to three debates in relation with political geology. First, it proposes a renewed definition of ‘volume’ based on the work of Michel Serres. The ‘volume’ is not a property of the underground nor a geometric ideality but defined as a transitory ordering of the ‘multitude’ that encompasses material, knowledge and political issues. It enables the development of a more continuous analytical strategy to follow geological and political crossed influences, and contributes to this project by going beyond existing divides (e.g. vitalist/constructivist). Second, the paper provides the reader with a complementary perspective (from the field instead of a compilation of data at an international level) about what it means to assess an unconventional resource. The proposed definition of ‘volume’ does not reduce uncertainty to a matter of knowing but makes it constitutive of the making of a gas potential. This enables one to follow the chain of mediations through which uncertainty is framed and strategically managed to meet industrial, scientific and political interests, while taming local oppositions. Third, the paper analyses why this coalbed methane ‘stratum’ may be democratically contested and transitory instead of preparing the ground for a low-carbon transition. This case study looks at a unique situation in France, namely a private company receiving public support in the context of political tensions about unconventional gas, and shows the country's internal contradictions and delays in updating its institutions and strategy concerning the use of underground resources for a low-carbon transition.

Impact of COVID-19 Pandemic on a Regional Stroke Thrombectomy Service in the United Kingdom

Introduction: We examined the impact of the coronavirus disease 2019 (COVID-19) pandemic on our regional stroke thrombectomy service in the UK. Methods: This was a single-center health service evaluation. We began testing for COVID-19 on 3 March and introduced a modified “COVID Stroke Thrombectomy Pathway” on 18 March. We analyzed the clinical, procedural and outcome data for 61 consecutive stroke thrombectomy patients between 1 January and 30 April. We compared the data for January and February (“pre-COVID,” n = 33) versus March and April (“during COVID,” n = 28). Results: Patient demographics were similar between the 2 groups (mean age 71 ± 12.8 years, 39% female). During the COVID-19 pandemic, (a) total stroke admissions fell by 17% but the thrombectomy rate was maintained at 20% of ischemic strokes; (b) successful recanalization rate was maintained at 81%; (c) early neurological outcomes (neurological improvement following thrombectomy and inpatient mortality) were not significantly different; (d) use of general anesthesia fell significantly from 85 to 32% as intended; and (e) time intervals from onset to arrival, groin puncture, and recanalization were not significantly different, whereas internal delays for external referrals significantly improved for door-to-groin puncture (48 [interquartile range (IQR) 39–57] vs. 33 [IQR 27–44] minutes, p = 0.013) and door-to-recanalization (82.5 [IQR 61–110] vs. 60 [IQR 55–70] minutes, p = 0.018). Conclusion: The COVID-19 pandemic has had a negative impact on the stroke admission numbers but not stroke thrombectomy rate, successful recanalization rate, or early neurological outcome. Internal delays actually improved during the COVID-19 pandemic. Further studies should examine the effects of the COVID-19 pandemic on longer term outcome.

Performance Analysis and Design Optimization of Parallel-Type Slew-Rate Enhancers for Switched-Capacitor Applications

The design of single-stage OTAs for accurate switched-capacitor circuits involves challenging trade-offs between speed and power consumption. The addition of a Slew-Rate Enhancer (SRE) circuit placed in parallel to the main OTA (parallel-type SRE) constitutes a viable solution to reduce the settling time, at the cost of low-power overhead and no modifications of the main OTA. In this work, a practical analytical model has been developed to predict the settling time reduction achievable with OTA/SRE systems and to show the effect of the various design parameters. The model has been applied to a real case, consisting of the combination of a standard folded-cascode OTA with an existing parallel-type SRE solution. Simulations performed on a circuit designed with a commercial 180-nm CMOS technology revealed that the actual settling-time reduction was significantly smaller than predicted by the model. This discrepancy was explained by taking into account the internal delays of the SRE, which is exacerbated when a high output current gain is combined with high power efficiency. To overcome this problem, we propose a simple modification of the original SRE circuit, consisting in the addition of a single capacitor which temporarily boosts the OTA/SRE currents reducing the internal turn-on delay. With the proposed approach a settling-time reduction of 57% has been demonstrated with an SRE that introduces only a 10% power-overhead with respect of the single OTA solution. The robustness of the results have been validated by means of Monte-Carlo simulations.

Passive Geometry Calibration for Microphone Arrays Based on Distributed Damped Newton Optimization

Geometry calibration is an inherent challenge in distributed acoustic sensor networks. To mitigate this problem, a passive geometry calibration approach based on distributed damped Newton optimization is proposed. Specifically, a geometric cost function incorporating direction of arrivals (DoAs) and time difference of arrivals (TDoAs) is first formulated, and then its identifiability conditions are given. Next, to achieve a distributed geometry calibration, the cost function is split into multiple local cost functions that are assigned to every node. After that, a distributed damped Newton optimization is presented to retrieve the geometry of microphone nodes and synchronize the internal delay between each two neighboring nodes. Finally, computational complexity and transmission bandwidth requirements are further analyzed. Compared with the existing approaches, the proposed method estimates the geometry structure of microphone networks in a distributed manner. Moreover, it requires a small number of acoustic sources. Experimental results show the validity of the proposed method.

A Computationally Efficient Tensor Regression Network-Based Modeling Attack on XOR Arbiter PUF and Its Variants

XOR arbiter PUF (XOR APUF), where the outputs of multiple arbiter PUF (APUFs) are XOR-ed, has proven to be more robust to machine learning-based modeling attacks. The reported successful modeling attacks for XOR APUF either employ auxiliary side-channel or reliability information, or require enormous computational effort. This robustness is primarily due to the difficulty in learning the unknown internal delay parameter terms in the mathematical model of a XOR APUF, and the robustness increases as the number of APUFs being XOR-ed increases. In this article, we employ a novel machine learning-based modeling technique called efficient CANDECOMP/PARAFAC-tensor regression network (CP-TRN), a variant of CP-decomposition-based tensor regression network, to reduce the computational resource requirement of model building attacks on XOR APUF. We theoretically prove the reduction in computational complexity, as well as give supporting experimental results. In addition, our proposed technique does not require any auxiliary information, and is robust to noisy training data. The proposed technique allowed us to successfully model 64-bit 8-XOR APUF and 128-bit 7-XOR APUF on a single desktop workstation, with high prediction accuracy. Further, we extend the proposed modeling attack technique to XOR APUF variants, e.g., lightweight secure PUF (LSPUF), which rely on input challenge transformation. The modeling accuracy results obtained by us for the LSPUF are comparable with those obtained by applying other state-of-the-art techniques, while requiring less training data.

Finite-time synchronization of stochastic complex networks with random coupling delay via quantized aperiodically intermittent control

This paper studies the finite-time synchronization issue of stochastic complex networks (SCNs) with random coupling delay and nonlinear coupling function. Internal delay, perturbation delay are also considered into this model. Meanwhile, a quantized aperiodically intermittent control strategy is proposed to realize finite-time synchronization of SCNs. By means of Lyapunov stability theory and graph theory, two types of sufficient conditions are derived to ensure finite-time synchronization of SCNs. The obtained results are closely related to the maximum proportion of rest width and the topological structure of considered networks. Moreover, the theoretical results is applied to study finite-time synchronization of stochastic coupled oscillators. Finally, a numerical example is presented to demonstrate the effectiveness and feasibility of the obtained results.

Receptance-based robust stability criteria for second-order linear systems with time-varying delay and unstructured uncertainties

This paper presents new frequency domain criteria for the robust stability analysis of closed-loop second-order systems under time-varying internal delay. The proposed approach is derived from the small gain theorem for systems described by the versatile system receptance to guarantee robust stability despite time-varying delays and model uncertainties. Robust stability of systems with time-varying delays is challenging to cope because time-invariant paradigm does not hold, but the proposed approach is directly based on the frequency response analysis of the closed-loop system with unstructured uncertainty bound. The criteria can be applied to either single or multiple inputs systems, and no constraint is imposed on the delay derivative. A simple receptance-based Internal Model Control strategy is proposed to improve robust stability margins while nominal state-feedback design is preserved. Thus, a controller obtained from the delay-free nominal model can be used to ensure the robust stability of the uncertain second-order system with time-varying delay. Simulation case studies are used to illustrate the benefits of the proposed criteria.

Functional Observers Design for Linear Systems with Non-commensurate Time Varying Delays

This paper deals with the problem of functional observer design for systems with non-commensurate time varying delays. The main procedure of three types of functional observers are presented in this article, more precisely, observers with delays dependent, observers without internal delays and delay-free functional observers. A necessary condition for the existence of these observers is given as rank equality. The design conditions for functional observers are presented in terms of linear matrix inequalities (LMIs). The solution of these LMIs is used to determine the observers parameters. Finally, some numerical examples are given at the end of the paper to show the feasibility of the proposed approach.

Global synchronization of coupled reaction–diffusion neural networks with general couplings via an iterative approach

Abstract We establish a framework to investigate the global synchronization of coupled reaction–diffusion neural networks with time delays. The coupled networks under consideration can incorporate both the internal delays in each individual network and the transmission delays across different networks. The coupling scheme for the coupled networks is rather general, and its performance is not adversely affected by the restrictions commonly imposed by existing relevant investigations. Based on the proposed iterative approach, the problem of global synchronization is transformed into that of solving the corresponding homogeneous linear system of algebraic equations. The synchronization criterion is subsequently derived and can be verified with simple computations. Three numerical examples are presented to illustrate the effectiveness of the synchronization theory presented in this paper.

Signal Diversification Is Associated with Corollary Discharge Evolution in Weakly Electric Fish.

Communication signal diversification is a driving force in the evolution of sensory and motor systems. However, little is known about the evolution of sensorimotor integration. Mormyrid fishes generate stereotyped electric pulses (electric organ discharge [EOD]) for communication and active sensing. The EOD has diversified extensively, especially in duration, which varies across species from 0.1 to >10 ms. In the electrosensory hindbrain, a corollary discharge that signals the timing of EOD production provides brief, precisely timed inhibition that effectively blocks responses to self-generated EODs. However, corollary discharge inhibition has only been studied in a few species, all with short-duration EODs. Here, we asked how corollary discharge inhibition has coevolved with the diversification of EOD duration. We addressed this question by comparing 7 mormyrid species (both sexes) having varied EOD duration. For each individual fish, we measured EOD duration and then measured corollary discharge inhibition by recording evoked potentials from midbrain electrosensory nuclei. We found that delays in corollary discharge inhibition onset were strongly correlated with EOD duration as well as delay to the first peak of the EOD. In addition, we showed that electrosensory receptors respond to self-generated EODs with spikes occurring in a narrow time window immediately following the first peak of the EOD. Direct comparison of time courses between the EOD and corollary discharge inhibition revealed that the inhibition overlaps the first peak of the EOD. Our results suggest that internal delays have shifted the timing of corollary discharge inhibition to optimally block responses to self-generated signals.SIGNIFICANCE STATEMENT Corollary discharges are internal copies of motor commands that are essential for brain function. For example, corollary discharge allows an animal to distinguish self-generated from external stimuli. Despite widespread diversity in behavior and its motor control, we know little about the evolution of corollary discharges. Mormyrid fishes generate stereotyped electric pulses used for communication and active sensing. In the electrosensory pathway that processes communication signals, a corollary discharge inhibits sensory responses to self-generated signals. We found that fish with long-duration pulses have delayed corollary discharge inhibition, and that this time-shifted corollary discharge optimally blocks electrosensory responses to the fish's own signal. Our study provides the first evidence for evolutionary change in sensorimotor integration related to diversification of communication signals.

Exponential synchronization of nonlinear complex networks via intermittent pinning control on time scales

This paper considers the synchronization problem of nonlinear complex dynamical networks (CDNs) through intermittent pinning control approach on time scales. Both the internal delay and coupling delay are considered in the nonlinear CDNs. To deal with the nonlinearity in the delayed complex network, a new scale-limited differential inequality is proposed. Based on the Lyapunov approach and the theory of time scales, some novel exponential synchronization criteria are derived, which are applicable not only to the continuous/discrete CDNs but also to the case of continuous–discrete hybrid time domains. Two numerical examples are provided to certify the validness of the proposed design method.

A recalling-enhanced recurrent neural network: Conjugate gradient learning algorithm and its convergence analysis

Elman network is a classical recurrent neural network with an internal delay feedback. In this paper, we propose a recalling-enhanced recurrent neural network (RERNN) which has a selective memory property. In addition, an improved conjugate algorithm with generalized Armijo search technique that speeds up the convergence rate is used to train the RERNN model. Further enhancement performance is achieved with adaptive learning coefficients. Finally, we prove weak and strong convergence of the presented algorithm. In other words, as the number of training steps increases, the following has been established for RERNN: (1) the gradient norm of the error function with respect to the weight vectors converges to zero, (2) the weight sequence approaches a fixed optimal point. We have carried out a number of simulations to illustrate and verify the theoretical results that demonstrate the efficiency of the proposed algorithm.

Stabilization of coupled wave equations with boundary or internal distributed delay

We consider a system of compactly coupled wave equations with distributed delay terms in the boundary or internal feedbacks. In both cases, we establish, under some assumptions, the exponential decay of the solution. These results are obtained by introducing suitable energy functions and by proving some observability estimates.

Stability results for an elastic–viscoelastic wave equation with localized Kelvin–Voigt damping and with an internal or boundary time delay

We investigate the stability of a one-dimensional wave equation with non smooth localized internal viscoelastic damping of Kelvin–Voigt type and with boundary or localized internal delay feedback. The main novelty in this paper is that the Kelvin–Voigt and the delay damping are both localized via non smooth coefficients. Under sufficient assumptions, in the case that the Kelvin–Voigt damping is localized faraway from the tip and the wave is subjected to a boundary delay feedback, we prove that the energy of the system decays polynomially of type t − 4 . However, an exponential decay of the energy of the system is established provided that the Kelvin–Voigt damping is localized near a part of the boundary and a time delay damping acts on the second boundary. While, when the Kelvin–Voigt and the internal delay damping are both localized via non smooth coefficients near the boundary, under sufficient assumptions, using frequency domain arguments combined with piecewise multiplier techniques, we prove that the energy of the system decays polynomially of type t − 4 . Otherwise, if the above assumptions are not true, we establish instability results.

Design and Realizations of Networked Estimators: A Descriptor Model Approach

This paper addresses the design and realization of a networked estimator, which requires further digital implementation using several subsystems. Implementation on a digital process entails finite word length effects on the coefficients’ representation, and a multiple-subsystem architecture also introduces internal time delays in the information interaction. Dealing with these intrinsic defects requires finding a resilient realization. A corresponding descriptor model-based approach is thus constructed to describe the internal time delays and equivalent realizations with finite word length effects in a unifying framework, which enables simultaneous consideration of design and realization. Based on the obtained descriptor model, a stability analysis condition is deduced and a design method for the estimator is further obtained. An algorithm is also proposed for finding the optimal realization requiring the minimum word length for stabilization. Finally, a simulation with two cooperative robots is considered to illustrate the effectiveness of the results.

Vector network analyzer usage at calibration of delay in satellite radio navigation system signal simulators

This article presents a method of vector network analyzer application at the task of global navigation system simulator calibration. Calibrated parameter is internal delay of the radiofrequency signal in simulator. Attention is payed to reducing of calibration uncertainty by means of taking into account the part, which is caused by impedance of simulator and other equipment mismatches. The goal of research is to estimate the non-excluded uncertainty after vector network analyzer measurements’ usage for correction calculation. Measured parameters are the group delay, reflection and transmission coefficients of cable with connectors, and reflection coefficients of simulator and oscilloscope. The goal has been achieved by means of simulation modelling. The main parts of modelling were simulation of vector network analyzer measurements’ and calculation the statistics of the non-excluded uncertainty. As the result, was shown, that if to use vector network analyzer for global navigation system simulator calibration, the part of uncertainty, caused by impedance mismatch, can be reduced in a several times.

Pinning synchronization of weighted bipartite networks with time-varying delays via aperiodic intermittent control

Bipartivity has been revealed as an important topological feature of many real networks. In this paper, we first propose a model of weighted bipartite networks with time-varying delays, where both internal delay and communication delay are incorporated, and meanwhile the delayed coupling contains only one single transmittal delay. Then we investigate its pinning synchronization problem via aperiodic intermittent control. By utilizing the Lyapunov functional method and mathematical induction, a generic global exponential synchronization criterion is established. Moreover, based on the theory of linear algebra, two easy verifiable low-dimensional synchronization conditions are obtained. It is shown that the network nodes with the highest degrees should be pinned successively. Finally, numerical simulations are given to verify the validity of the theoretical analysis.

A Novel Delay-Independent Robust Adaptive Controller Design for Uncertain Nonlinear Systems With Time-Varying State Delay

Abstract In this paper, two novel adaptive control strategies are presented based on the linear matrix inequality for nonlinear Lipschitz systems. The proposed approaches are developed by creatively using Krasovskii stability theory to compensate parametric uncertainty, unknown time-varying internal delay, and bounded matched or mismatched disturbance effects in closed-loop system of nonlinear systems. The online adaptive tuning controllers are designed such that reference input tracking and asymptotic stability of the closed-loop system are guaranteed. A novel structural algorithm is developed based on linear matrix inequality (LMI) and boundaries of the system delay or uncertainty. The capabilities of the proposed tracking and regulation methods are verified by simulation of three physical uncertain nonlinear system with real practical parameters subject to internal or state time delay and disturbance.

Enhancement for Real-Time Ethernet Clock Synchronization by Internal Processing Delay Measurement

Propagation delay asymmetry is one of the biggest factors affecting the performance of clock synchronization. For an industrial Ethernet system that implements communication in pure hardware, almost all the asymmetries are caused by hardware factors. In this letter, we analyze the hardware factors for the asymmetry of 100Base-Tx real-time Ethernet system. Then, a low-cost method to mitigate the asymmetry is proposed. The effectiveness of the method will be evaluated by experiments on real-world devices.