Impulse Input Research Articles

Developing Models of Lithuanian Speech Vowels and Semivowels

Lithuanian vowel and semivowel phoneme modelling framework is proposed. Using this framework, the phoneme signal is described as the output of a linear multiple-input and single-output (MISO) system. The MISO system is a parallel connection of single-input and single-output (SISO) systems whose input impulse amplitudes vary in time. Within this framework two synthesis methods are proposed: harmonic and formant. The synthesized sounds obtained by the harmonic synthesis method are compared with those obtained by the formant method. Application of this modelling framework to all of Lithuanian vowel and semivowel synthesis gives naturally sounding result.

Analgesic and anti‐hyperalgesic effects of muscle injections with lidocaine or saline in patients with fibromyalgia syndrome

Patients with musculoskeletal pain syndrome including fibromyalgia (FM) complain of chronic pain from deep tissues including muscles. Previous research suggests the relevance of impulse input from deep tissues for clinical FM pain. We hypothesized that blocking abnormal impulse input with intramuscular lidocaine would decrease primary and secondary hyperalgesia and FM patients' clinical pain. We enrolled 62 female patients with FM into a double-blind controlled study of three groups who received 100 or 200 mg of lidocaine or saline injections into both trapezius and gluteal muscles. Study variables included pressure and heat hyperalgesia as well as clinical pain. In addition, placebo factors like patients' anxiety and expectation for pain relief were used as predictors of analgesia. Primary mechanical hyperalgesia at the shoulders and buttocks decreased significantly more after lidocaine than saline injections (p = 0.004). Similar results were obtained for secondary heat hyperalgesia at the arms (p = 0.04). After muscle injections, clinical FM pain significantly declined by 38% but was not statistically different between lidocaine and saline conditions. Placebo-related analgesic factors (e.g., patients' expectations of pain relief) accounted for 19.9% of the variance of clinical pain after the injections. Injection-related anxiety did not significantly contribute to patient analgesia. These results suggest that muscle injections can reliably reduce clinical FM pain, and that peripheral impulse input is required for the maintenance of mechanical and heat hyperalgesia of patients with FM. Whereas the effects of muscle injections on hyperalgesia were greater for lidocaine than saline, the effects on clinical pain were similar for both injectates.

An Impulse Response Model and $Q$ -Factor Estimation for Vehicle Cavities

To facilitate efficient communications (i.e., minimum power consumption and maximum information throughput) in vehicle cavities, it is necessary to fully understand the underlying physics of the propagation process. This can be characterized as a statistical model of the channel impulse response, which we derive from a general starting point. The impulse response model is useful in its own right for ultrawideband pulse radio communications, channel simulations, and time-of-arrival positioning systems, and it also allows us to verify the generally accepted property that the energy retained in the cavity exponentially decays with time after an impulse input. This property can be characterized as a cavity Q-factor, and we investigate methods of Q-factor estimation in vehicle cavities, using only a limited amount of data, such as would typically be available to a deployed in-vehicle wireless network. We find that the most reliable approach utilizes an inverse-discrete-Fourier-transform-based method, which finds the maximum-likelihood instantaneous Q-factor, given measured data across various spatial links and frequency channels.

Исследование устойчивости элементов заряда твердого топлива в условиях импульсного воздействия

Исследование устойчивости элементов заряда твердого топлива в условиях импульсного воздействия

The dynamic elastic response to impulse synchronisation of composite prosthetic energy storing and returning feet

In this research, it is proven that perfect synchronisation between the input impulse (human effort) and the ground reaction impulse/impact can result in a phenomenon called the dynamic elastic response to impulse synchronisation with favourable consequences to the behaviour of the energy storing and returning foot. An energy storing and returning composite prosthetic foot was first used in elite competition at the 1988 Paralympic Games. Since its introduction, the prostheses have proven to be a source of controversy. In 2008, it was concluded that the athletes who use such technology when running are in an advantageous position when compared to able-bodied athletes. However, these findings have since been disputed. There still remain unanswered questions regarding the level of contribution of energy storing and returning feet in the performance of amputee athletes. A series of investigations have previously been conducted to study the dynamic characteristics of a number of energy storing and returning composite prosthetic feet. It was found that if a sinusoidal input impulse, with a frequency close to one of the energy storing and returning feet’s natural frequencies, could be applied, it can make the energy storing and returning foot susceptible to resonance, which, in the case of bending mode, if sustained can lead to a gain in height or increased velocity.

Reliability-based optimal controller design for systems with probabilistic uncertain parameters using fuzzy limit state function

In this paper, a fuzzy rule-based system (FRS) has been used for optimal reliability-based robust controller design for a two-mass-spring system with probabilistic uncertainties in its parameters. In this way, a multiobjective uniform-diversity genetic algorithm (MUGA) is first used to find a Pareto front of two-mass-spring system in a deterministic approach. This paper considers a two-mass-spring system under an impulse input. Two conflicting objective functions in this model include settling time of the second mass and control effort exerted on the first mass. Consequently, such Pareto front is then obtained for a two-mass-spring system with probabilistic uncertainties in its parameters using the probabilities of failure of those objective functions through a Monte Carlo simulation approach. It is shown that the FRS system removes the difficulty of selecting suitable crisp values and obligation due to a defining limit state function. Besides, the multiobjective Pareto optimization of such robust controllers using MUGA unveils some very important and informative trade-offs among those objective functions. Consequently, some optimum robust controllers can be compromisingly chosen from the Pareto frontiers.

Exponential stability of a class of nonlinear singularly perturbed systems with delayed impulses

A class of nonlinear singularly perturbed systems with delayed impulses is considered. By delayed impulses we mean that the impulse maps describing the state's jumping at impulsive moments are dependent on delayed state variables. Assuming that each of two lower order subsystems possesses a Lyapunov function, exponential stability criteria for all small enough values of singular perturbation parameter are obtained. It turns out that the achieved exponential stability is robust with respect to small impulse input delays. A stability bound on perturbation parameter is also derived through using those Lyapunov functions. Additionally, for a class of singularly perturbed Lur'e systems with delayed impulses, an LMI-based method to determine stability and an upper bound of the singular perturbation parameter is presented. The results are illustrated by an example for the position control of a dc-motor with unmodelled dynamics.

Latency and rate coding in a spiking model of retina

We describe a family of spiking retina computational models for large-scale simulations of the visual pathways. The models reproduce the overall spatial, temporal, and chromatic structure of the receptive fields of midget and parasol retinal ganglion cells (RGCs) of the primate retina, as well as their contrast response, while using fairly simple models of bipolar, horizontal, amacrine, and RGCs. These retina models provide input to a realistic model of visual cortex, presented in a separate submission. The retina model simulates cone and bipolar cell dynamics using a damped wave equation. Parameters are so chosen that an impulse retinal input gives rise to a damped biphasic output current, and that a coherent stimulus elicits a substantially stronger response than an incoherent stimulus of the same power (Figure ​(Figure1).1). Static or low-frequency visual inputs are smoothly rejected. In contrast to biology, this stage of the model is linear; rectification and adaptation mechanisms are all realized in the spiking ganglion cell layer. In the ganglion cell layer parasol, midget, and SBC cells are simulated. The spatio-temporal receptive fields of different RGCs are not prewired; they emerge via the lateral interactions between the horizontal, bipolar, and amacrine cells. Spike generation in the RGCs is modeled using spiking neurons with two dynamic variables and an intrinsic adaptation mechanism. Midget RGCs have an additional leaky temporal integration of the input current, to account for the relatively tonic character of their responses. Parasol RGCs have an additional partial divisive normalization of the input current, to reproduce the saturating parasol response to relative contrast of the stimulus. Simplified amacrine-cell dynamics is introduced to provide for the spatiotemporal structure of the parasol receptive field surrounds. Figure 1 A-E: model response to coherent vs. randomized stimulus. Moving edge stimulus is presented (A) and elicits strong response (B). Same stimulus with fixed random permutation of pixels (C) elicits much weaker response (D). (E) compares the total responses ... Desired latency encoding of input features is achieved by calibrating the parameters of the spiking RGC conductance dynamics. A near logarithmic latency to the first spike, for a step up in the input signal, provides for a good contrast invariance of the relative spike timing in the response. A combination of spike-latency and spike-count encoding of the input stimulus, together with the enhanced response of the simulated retina to coherent stimuli, results in an informative yet not too noisy spiking input to the LGN and V1; the information content analysis of the RGC spike-train vocabulary will be presented. This retina model was used to produce a fully-emergent orientation tuning in a spiking model [1] of V1 cortex.

Study on Thermal Response to Instantaneous Heat Generation in LN2 Chamber for HTS-FCL

This paper describes the thermal response of a high-temperature superconducting (HTS) wire model to instantaneous heat generation in a pressurized liquid nitrogen chamber for an HTS fault current limiter. A dc impulse power input to a stainless steel strip is adopted to simulate the quench state of the HTS wire. The test sample is submerged in the liquid nitrogen, which maintains a 77 K temperature with operating pressures of 101, 250, 400, and 600 kPa. Three different levels of dc current are supplied to the test sample during 50 ms for each operating condition. The boiling phenomena are captured with a high-speed camera and the surface temperature of the sample strip is measured to investigate the recovery process. From the captured video, the suppression of bubble generation is clearly observed as increasing operating pressure, especially for the lower heat flux condition. From the measurement of temperature, temperature rise of sample strip during heat generation decreases with increasing operating pressure except for the higher heat flux. For the recovery process, increasing operating pressure delays the recovery of the sample strip, but recovery time is within a few seconds for all cases.

Delayed Impulsive Control of Takagi–Sugeno Fuzzy Delay Systems

In this paper, the problem of exponential stability for Takagi-Sugeno (T-S) fuzzy delay systems with delayed impulses is addressed. By means of the time-dependent Lyapunov function method combined with Razumikhin technique, a sufficient condition expressed in terms of linear matrix inequalities (LMIs) is obtained for exponential stability of T-S fuzzy delay systems with delayed impulses. The derived stability condition depends both on the lower bound and the upper bound of impulsive intervals, which is robust with respect to small impulse input delays. By solving a set of LMIs, an impulsive state feedback controller can be easily constructed. Two numerical examples are discussed to illustrate the effectiveness of the theoretical findings.

Analytic Analysis of Transient Radiation From Phased Array Antennas in the Near- and Far-Field Focus Applications

This paper presents an analytical transient analysis of electromagnetic field radiation from a time-delayed and finite periodic array of antennas for the near- and far-field focused applications. The elemental current moments of array are assumed with a transient impulse input for the excitations whose signals are delayed to radiate near-zone focused fields. The transient field phenomena for each of the Floquet mode expansion were analyzed. The solution reduces to the case of far-zone field radiation by moving the focus point to the far zone. The analysis shows that the radiation exhibits an impulse field at the focused point, and finite pulses at locations away from the focus point. Phenomena of partial cylindrical wave functions have been observed.

Numerical investigation on feedback control of flow around an oscillating hydrofoil by Lorentz force

In order to improve the hydrodynamic characteristics of a hydrofoil (NACA0012), this paper investigates an oscillating hydrofoil immersed in seawater (an electrically poorly conducting fluid) with feedback control of electromagnetic force (Lorentz force). This method is used in the iterative process, by forecasting the location of boundary layer separation points and attack angle at the next time step and figuring out the optimal force distribution function based on these parameters, then returns to the current time step and applies the optimal force onto the leeside to control the flow separation. Based on the basic flow governing equations, the flow field structures, lift evolutions and energy consumptions (the input impulse of Lorentz force) have been numerically investigated. Numerical results show that with this control, the flow separation could be fully suppressed. Meanwhile, the lift increases dramatically and oscillation is suppressed successfully. Furthermore, under similar lift improvement and control effects, the feedback control optimal ratio is 72.58%.

Objective Biomarkers or Symptom Scores for the Classification of Fibromyalgia Syndrome?

Multiple abnormalities in pain processing have been reported in patients with chronic musculoskeletal pain syndromes including fibromyalgia (FM). These changes include mechanical and thermal hyperalgesia, decreased thresholds to mechanical and thermal stimuli (allodynia) as well as central sensitization, all of which are fundamental to the generation of clinical pain. In addition to pain, self-reported symptoms like negative mood, non-refreshing sleep, and dyscognition, are common in FM. The pathogenesis of FM is only partially understood, but peripheral tissue changes and nervous system abnormalities have been implicated. These tissue abnormalities include decreased blood flow, increased levels of muscle metabolites, and degenerative joint changes. Indirect evidence from interventions that decrease tonic peripheral impulse input in patients with FM suggest that their overall pain and hyperalgesia is dependent on signaling from deep tissues. At least some of this peripheral impulse input seems to undergo abnormal pain processing in the central nervous system including increased pain facilitation as well as inadequate pain inhibition. Thus interventions that either decrease peripheral input and/or improve central pain processing abnormalities appear to be promising strategies for FM patients. The 1990 FM classification criteria were instrumental for research that greatly improved our current understanding of FM mechanisms. These criteria required widespread pain and mechanical hyperalgesia at ≥ 11 out of 18 body sites (tender points). In 2010 new FM criteria were introduced which only require self-reported somatic and cognitive symptoms, use complex scoring algorithms, and lack any objective mechanistic assessments. This lack of objective biomarker, however, may limit the usefulness of the new FM Criteria for research and clinical practice. Overall the diagnosis as well as the treatment of FM may benefit from improved classification criteria which should include relevant disease biomarkers that are fundamental for the development and persistence of FM and other chronic musculoskeletal pain syndromes, like abnormal central nervous system processing abnormalities of nociceptive signals. Keywords: Biomarker, central sensitization, nociception, fibromyalgia, chronic pain

Viscerosomatic Facilitation in a Subset of IBS Patients, an Effect Mediated by N-Methyl-D-Aspartate Receptors

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder in which the pathophysiological mechanisms of the pain and hypersensitivity are incompletely understood. IBS patients frequently complain of pain in body regions somatotopically distinct from the gut, suggesting involvement of central hyperalgesic mechanisms. We tested the role of tonic peripheral impulse input by using both repetitive thermal stimuli to the leg and repetitive stimuli to the rectum. Changes in thermal/visceral pain sensitivity after nociceptive thermal/visceral repetitive stimulation were determined. A subset of IBS patients showed enhanced rectal/thermal pain sensitivity after repetitive thermal/rectal stimulation, respectively. IBS patients then received 60 mg dextromethorphan and placebo (diphenhydramine) in a randomized, double-blind, crossover trial. The results showed that 1) a subset of IBS patients had increased visceral/cutaneous hypersensitivity following a series of repetitive nociceptive stimuli and that 2) this increased pain sensitivity was blocked by administration of dextromethorphan. This is the first human study indicating that repetitive stimulation enhances a bidirectional mechanism of secondary hyperalgesia due to viscerosomatic facilitation in IBS patients. These unique findings elucidate mechanisms of somatic hypersensitivity in IBS patients and support an etiologic basis for abnormal N-methyl-D-aspartate receptor mechanisms that may be the target of future therapies for IBS. PerspectiveRepetitive stimulation enhances a bidirectional mechanism of secondary hyperalgesia due to viscerosomatic convergence in IBS patients. The findings elucidate unique mechanisms of somatic/visceral hypersensitivity in a subset of IBS patients and further support an etiologic basis for abnormal N-methyl-D-aspartate receptor mechanisms that may be future targets of therapies for IBS.

Comparison of Spectral and Wavelet Estimators of Transfer Function for Linear Systems

AbstractWe compare spectral and wavelet estimators of the response amplitude operator (RAO) of a linear system, with various input signals and added noise scenarios. The comparison is based on a model of a heaving buoy wave energy device (HBWED), which oscillates vertically as a single mode of vibration linear system. HBWEDs and other single degree of freedom wave energy devices such as oscillating wave surge convertors (OWSC) are currently deployed in the ocean, making such devices important systems to both model and analyse in some detail. The results of the comparison relate to any linear system. It was found that the wavelet estimator of the RAO offers no advantage over the spectral estimators if both input and response time series data are noise free and long time series are available. If there is noise on only the response time series, only the wavelet estimator or the spectral estimator that uses the cross-spectrum of the input and response signals in the numerator should be used. For the case of noise on only the input time series, only the spectral estimator that uses the cross-spectrum in the denominator gives a sensible estimate of the RAO. If both the input and response signals are corrupted with noise, a modification to both the input and response spectrum estimates can provide a good estimator of the RAO. A combination of wavelet and spectral methods is introduced as an alternative RAO estimator. The conclusions apply for autoregressive emulators of sea surface elevation, impulse, and pseudorandom binary sequences (PRBS) inputs. However, a wavelet estimator is needed in the special case of a chirp input where the signal has a continuously varying frequency.

Research on the Influence of Unsprung Mass on Vehicle Handling Stability

A dynamical model of engine vehicle was built by using ADAMS/Car. Based on that, another dynamical model of four-independent-wheel-drive electric vehicle was built too. Two simulation experiments of steering wheel angle step input and steering wheel angle impulse input were done. Considering the vehicle mathematical model with two linear degrees of freedom, the transient response and frequency response characteristics were evaluated. Simulation results indicated that time-domain and frequency-domain characteristics of four-independent-wheel-drive electric vehicle were influenced because of its heavy unsprung mass, and that leaded to the deteriorative handling stability.

Abnormal endogenous pain modulation is a shared characteristic of many chronic pain conditions

The intensity of acute and chronic pain depends on interactions between peripheral impulse input and CNS pain mechanisms, including facilitation and inhibition. Whereas tonic pain inhibition is a characteristic of most pain-free individuals, pain facilitation can be detected in many chronic pain patients. The capability to inhibit pain is normally distributed along a wide continuum in the general population and can be used to predict chronic pain. Accumulating evidence suggests that endogenous pain inhibition depends on activation of the prefrontal cortex, periaqueductal gray and rostral ventral medulla. Quantitative sensory test paradigms have been designed to acquire detailed information regarding each individual’s endogenous pain inhibition and facilitation. Such tests include: temporal summation of pain, which is mostly used to assess facilitatory pain modulation by measuring the change in pain perception during a series of identical nociceptive stimuli; and conditioned pain modulation, which tests pain inhibition by utilizing two simultaneously applied painful stimuli (the ‘pain inhibits pain’ paradigm). Considerable indirect evidence seems to indicate that not only increased pain facilitation but also ineffective pain inhibition represents a predisposition for chronic pain. This view is supported by the fact that many chronic pain syndromes (e.g., fibromyalgia, temporomandibular joint disorder, irritable bowel syndrome, headache and chronic fatigue syndrome) are associated with hypersensitivity to painful stimuli and reduced endogenous pain inhibition. However, future prospective studies will be necessary to provide definitive evidence for this relationship. Such research would not only provide important information about mechanisms relevant to chronic pain but would also permit identification of individuals at high risk for future chronic pain.

Energy flow analysis and hybrid controller design for non-linear electromagnetic suspension

In this paper, a mathematical model for the developed electromagnetic suspension actuator is established based on measured parameters and test data. A main/inner-loop control strategy is proposed for its active control and the inner loop undertakes the control of a three-phase motor by applying a hysteresis current control method to track the calculated signal by the main loop. With the simplification of the inner-loop control system, the achievable range of control current and energy flow states of the actuator are analysed. Then, owing to the non-linear damping characteristic of the actuator, a hybrid system model which involves real and integer variables is built up for the main loop and optimal control to improve vehicle ride comfort is carried out based on a model predictive control method. Simulations are carried out with bump impulse and random uneven road inputs and the results demonstrate that the electromagnetic suspension with the designed hybrid controller can improve vehicle ride comfort compared with a corresponding passive suspension while energy is consumed from the battery.

Evidence for Shared Pain Mechanisms in Osteoarthritis, Low Back Pain, and Fibromyalgia

Osteoarthritis (OA), low back pain (LBP), and fibromyalgia (FM) are common chronic pain disorders that occur frequently in the general population. They are a significant cause of dysfunction and disability. Why some of these chronic pain disorders remain localized to few body areas (OA and LBP), whereas others become widespread (FM) is unclear at this time. Genetic, environmental, and psychosocial factors likely play an important role. Although patients with OA, LBP, and FM frequently demonstrate abnormalities of muscles, ligaments, or joints, the severity of such changes is only poorly correlated with clinical pain. Importantly, many patients with these chronic pain disorders show signs of central sensitization and abnormal endogenous pain modulation. Nociceptive signaling is actively regulated by the central nervous system to allow adaptive responses after tissue injuries. Thus, abnormal processing of tonic peripheral tissue impulse input likely plays an important role in the pathogenesis of OA, LBP, or FM. Tonic and/or intense afferent nociceptive barrage can result in central sensitization that depends on facilitatory input from brainstem centers via descending pain pathways to the spinal cord. Abnormal endogenous control of these descending pathways can lead to excessive excitability of dorsal horn neurons of the spinal cord and pain. Ineffective endogenous pain control and central sensitization are important features of OA, LBP, and FM patients.

Relative dispersions of intra-albumin transit times across rat and elasmobranch perfused livers, and implications for intra- and inter-species scaling of hepatic clearance using microsomal data.

It is recognized that vascular dispersion in the liver is a determinant of high first-pass extraction of solutes by that organ. Such dispersion is also required for translation of in-vitro microsomal activity into in-vivo predictions of hepatic extraction for any solute. We therefore investigated the relative dispersion of albumin transit times (CV2) in the livers of adult and weanling rats and in elasmobranch livers. The mean and normalized variance of the hepatic transit time distribution of albumin was estimated using parametric non-linear regression (with a correction for catheter influence) after an impulse (bolus) input of labelled albumin into a single-pass liver perfusion. The mean+/-s.e. of CV2 for albumin determined in each of the liver groups were 0.85+/-0.20 (n = 12), 1.48+/-0.33 (n = 7) and 0.90+/-0.18 (n = 4) for the livers of adult and weanling rats and elasmobranch livers, respectively. These CV2 are comparable with that reported previously for the dog and suggest that the CV2 of the liver is of a similar order of magnitude irrespective of the age and morphological development of the species. It might, therefore, be justified, in the absence of other information, to predict the hepatic clearances and availabilities of highly extracted solutes by scaling within and between species livers using hepatic elimination models such as the dispersion model with a CV2 of approximately unity.