Amplitude Plots Research Articles

Study of damping in composite beams

The vibrations produced in the structures or components are the primary source of problems in machine tools, aircraft and automobile structures. Vibrations can be overcome by introducing damping in these structures. A recent method to improve the damping ability of structures is by fabricating these with composites in order to enhance their service life.. In addition, composites are found to have superior strength, stiffness, improved corrosion and fatigue resistance.. The damping of FR composites depends on the structure, diameter and orientation of fiber in matrix. Damping at the fiber-matrix interface dissipates a significant amount of energy. In the current investigation, damping of structural composite beams has been studied to estimate the damping ratios and natural frequencies. The various composite beams used are Glass Fibre Reinforced Epoxy (GFE), Glass Fibre Reinforced Polyester (GFP) and Carbon Black Filled Epoxy (CBFE). Logarithmic decrement method is used to evaluate the damping parameters from the obtained amplitude versus time plots. The damping ratio and natural frequency values are found to be 0.2281 and 1664.94 rad/s respectively for CBFE. CBFE has highest damping property as compared to GFE and GFP.

Poincaré Plot of Fingertip Photoplethysmogram Pulse Amplitude Suitable to Assess Diabetes Status

Multiscale entropy (MSE), an estimate of the complexity of physiological signals has been used for assessing diabetes status. This method requires much computation effort. Our study aimed to examine the Poincare plot, an easier method for computation to differentiate the diabetes status. We selected subjects and divided them into three groups including the non-diabetes (HbA1c ≤ 6.5%, n=22), diabetes with good control (6.5% < HbA1c < 8%, n=23), and diabetes with poor control (HbA1c ≥ 8%, n=17). Poincare method used consecutive 250 data points of PPG pulse amplitudes from each subject's right index fingertip. This method resulted in SSR, the standard deviation of the original photoplethysmogram (PPG) pulse amplitude (SD1) and the standard deviation of the interval 1 PPG pulse amplitude (SD2) ratio. The SSR in the three groups of non-diabetes, diabetes with good control and diabetes with poor control were 0.50, 0.28, and 0.23, respectively and differed between groups (P < 0.05). Our findings suggested that the Poincare plot of right-hand PPG pulse amplitude may be convenient to evaluate diabetes status.

Stochastic resonance, coherence resonance, and spike timing reliability of Hodgkin–Huxley neurons with ion-channel noise

The random transitions of ion channels between open and closed states are a major source of noise in neurons. In this study, we investigate the stochastic dynamics of a single Hodgkin–Huxley (HH) neuron with realistic, physiological channel noise, which depends on the channel number and the voltage potential of the membrane. Without external input, the stochastic HH model can generate spontaneous spikes induced by ion-channel noise, and the variability of inter-spike intervals attains a minimum for an optimal membrane area, a phenomenon known as coherence resonance. When a subthreshold periodic input current is added, the neuron can optimally detect the input frequency for an intermediate membrane area, corresponding to the phenomenon of stochastic resonance. We also investigate spike timing reliability of neuronal responses to repeated presentations of the same stimulus with different realizations of channel noise. We show that, with increasing membrane area, the reliability of neuronal response decreases for subthreshold periodic inputs, and attains a minimum for suprathreshold inputs. Furthermore, Arnold tongues of high reliability arise in a two-dimensional plot of frequency and amplitude of the sinusoidal input current, resulting from the resonance effect of spike timing reliability.

A dynamical study of frictional effect on scaling of earthquake source displacement spectra

&lt;span style="font-family: 新細明體;"&gt;The scaling of earthquake source displacement spectra is analytically studied based on the continuous form of one-dimensional dynamical spring-slider model in the presence of either linearly slip-weakening friction or linearly velocity-weakening friction.&lt;/span&gt; The main parameters of the model are the natural angular frequency, w&lt;sub&gt;o&lt;/sub&gt;, and the (dimensionless) decreasing rate, &lt;em&gt;D&lt;/em&gt;, of friction with slip (or the characteristic displacement) for &lt;span style="font-family: 新細明體;"&gt;slip-weakening friction&lt;/span&gt; as well as the (dimensionless) decreasing rate, &lt;em&gt;u&lt;/em&gt;, of friction with velocity (or the characteristic velocity)&lt;span style="font-family: 新細明體;"&gt; for velocity-weakening friction. The analytic solution includes the complementary and particular parts. The former shows the travelling wave and the latter denotes vibrations at a site. The complementary solution exhibits &lt;/span&gt;&lt;em&gt;w&lt;/em&gt;&lt;span style="font-family: 新細明體;"&gt;&lt;sup&gt;-1&lt;/sup&gt; scaling in the whole range of &lt;/span&gt;&lt;em&gt;w&lt;/em&gt;&lt;span style="font-family: 新細明體;"&gt; for both friction laws. For the particular solution, slip-weakening friction results in spectral amplitudes only at three values of &lt;/span&gt;&lt;em&gt;w&lt;/em&gt;&lt;span style="font-family: 新細明體;"&gt;. For velocity-weakening friction with &lt;/span&gt;&lt;em&gt;u&lt;/em&gt;&lt;span style="font-family: 新細明體;"&gt;&amp;gt;0.5, &lt;/span&gt;the log-log plot of spectral amplitude versus &lt;em&gt;w&lt;/em&gt; exhibits almost &lt;em&gt;w&lt;/em&gt;&lt;sup&gt;0&lt;/sup&gt; scaling when &lt;em&gt;w&lt;/em&gt; is lower than the corner angular frequency, &lt;em&gt;w&lt;/em&gt;&lt;sub&gt;c&lt;/sub&gt;, which is independent on &lt;em&gt;u&lt;/em&gt; and increases with &lt;em&gt;w&lt;/em&gt;&lt;sub&gt;o&lt;/sub&gt;. When &lt;em&gt;w&lt;/em&gt;&amp;gt;&lt;em&gt;w&lt;/em&gt;&lt;sub&gt;c&lt;/sub&gt;, the spectral amplitude monotonically decreases with &lt;em&gt;w&lt;/em&gt; following a line with a slope value of -1, which is the scaling exponent.

Influence of tuned mass damper on fixed-free 3D nonlinear beam embedded in nonlinear elastic foundation

This study investigated the damping effects of a tuned mass damper (TMD) on a fixed-free 3D nonlinear beam resting on a nonlinear elastic foundation with existing internal resonances. The nonlinear elastic foundation below (y-direction) and beside (z-direction) the nonlinear beam was simulated using cubic nonlinear springs via the method of multiple scales for the analysis of this problem. We first examined this system to ensure if the internal resonance exists. The 1:3 internal resonance was found in the 1st and 2nd modes of the system. This prompted us to add a TMD on the elastic beam in order to suppress internal resonance and vibrations. We also examined the influence of the mass and location of the TMD as well as damping and spring coefficients on the damping effects. Analysis data is presented in graphs, including 3D maximum amplitude plots of the modes and 3D maximum amplitude contour plots. Our results show that placing the TMD in the y-direction also suppresses vibrations in the z-direction. The locations of the maximum amplitudes between node points in the mode shapes and near the free end of the beam indicate where the TMD should be placed with regard to damping.

Transmission beam characteristics of a Risso's dolphin (Grampus griseus).

The echolocation system of the Risso's dolphin (Grampus griseus) remains poorly studied compared to other odontocete species. In this study, echolocation signals were recorded from a stationary Risso's dolphin with an array of 16 hydrophones and the two-dimensional beam shape was explored using frequency-dependent amplitude plots. Click source parameters were similar to those already described for this species. Centroid frequency of click signals increased with increasing sound pressure level, while the beamwidth decreased with increasing center frequency. Analysis revealed primarily single-lobed, and occasionally vertically dual-lobed, beam shapes. Overall beam directivity was found to be greater than that of the harbor porpoise, bottlenose dolphin, and a false killer whale. The relationship between frequency content, beam directivity, and head size for this Risso's dolphin deviated from the trend described for other species. These are the first reported measurements of echolocation beam shape and directivity in G. griseus.

Overview of OPAMP and OTA based Integrators

The circuit realization of lossless and lossy integrators using active devices like opamp and OTA have been discussed. The realization of integrator in single ended and fully differential configurations is considered. The voltage-mode and current-mode integrators reported in the literature have been considered. The realization of OTA-based transadmittance type integrator has been considered. The OTA based integrator circuits have been simulated in PSPICE using a behavioral macro-model of the OTA as well with a practical CMOS OTA circuit. The amplitude and phase response plots obtained for OTA based integrators are presented.

Echolocation beam shape of the Risso's dolphin (Grampus griseus)

Studies have shown that echolocation signals of some odontocete species are projected in both single and sometimes vertically dual-lobed beam shapes. In this study, the echolocation beam of a Risso's dolphin (Grampus griseus) was measured from a captive individual ensonifying an underwater target. Clicks were recorded with an array of 16 hydrophones and the two dimensional beam shape was explored using frequency-dependent amplitude plots. Click source parameters were comparable to those already described for this species, while analysis revealed primarily single-lobed, and occasionally vertically dual-lobed, beam shapes. Center frequencies of click signals increased with increasing sound pressure level, while the −3 dB beam radius decreased with increasing center frequency. This study is the first to measure the beam shape of echolocation signals in G. griseus, which exhibits forms similar to those found in the bottlenose dolphin and false killer whale

Duration–amplitude relationships of volcanic tremor and earthquake swarms preceding and during the 2009 eruption of Redoubt Volcano, Alaska

Duration–amplitude relationships were studied for tremor episodes and earthquake swarms occurring during the 2009 eruption of Redoubt Volcano, Alaska. Duration–amplitude distribution plots were generated daily from January 1 to May 31 and fit with both an exponential law and power law. Comparing R2 values of the fit for both laws showed that the exponential law fit better for days in which volcanic tremor and earthquake swarms occurred, while the power law fit better for other days. Fitting segments of seismic data with both an exponential and a power law leads to a metric that has potential for volcano monitoring: R2exp/R2pow, the ratio of the R2 fits using the exponential law and the power law. The ratio R2exp/R2pow tended to be greater than 1 when volcanic activity or precursory seismic activity was occurring, and less than 1 when no volcano-seismic activity was occurring. Duration–amplitude plots were generated for episodes of volcanic tremor that were identified by the R2exp/R2pow≥1 method and compared in an attempt to identify changes that may have occurred during the eruption. Stronger episodes of volcanic tremor showed higher characteristic amplitudes. Maximum heights of the plumes generated by the explosions showed a positive correlation with the characteristic amplitude of the concurrent tremor.

경사안내면 상에서 이송되는 볼나사-슬라이드 이송계의 마찰기인 진동해석

ABSTRACT A moving mass on a skewed linear guideway model to analyze the friction-induced stick-slip behavior of ball-screw-driven slides is proposed. To describe the friction force, a friction coefficient function is modelled as a third-order polynomial of the relative velocity between the slide mass and a guideway. A nonlinear differential equation of motion is derived and an approximate solution is obtained using a perturbation method for the amplitudes and base frequencies of both pure-slip and stick-slip oscillations. The results are presented with time responses, phase plots, and amplitude plots, which are compared adequately with those obtained by Runge Kutta 4th-order numerical integration, as long as the difference between the static and kinematic friction coefficients is small. However, errors in the results by the approximate solution increase and are not negligible if the difference between the friction coefficients exceeds approximately 40% of the static friction coefficient.

Asymmetric EPR entanglement in continuous variable systems

Continuous variable entanglement can be produced in nonlinear systems or via the interference of squeezed states. In many optical systems such as parametric down conversion, the production of two perfectly symmetric subsystems is usually assumed when demonstrating the existence of entanglement. This symmetry simplifies the description of entanglement. However, asymmetry in entanglement may arise naturally in a real experiment, or be intentionally introduced in a given quantum information protocol. These asymmetries can emerge from having the output beams experience different losses and environmental contamination, or from the availability of non-identical input quantum states in quantum communication protocols. In this paper, we present a visualization of entanglement using quadrature amplitude plots of the twin beams. We quantitatively discuss the strength of asymmetric entanglement using EPR and inseparability criteria and theoretically show that the optimal beamsplitter ratio for entanglement is dependent on the asymmetries and may not be 50 : 50. To support this theory, we present experimental results showing one particular asymmetric entanglement where a 78 : 22 beamsplitter is optimal for observing entanglement.

Cyclic Plastic Response and Damage in Materials for High Temperature Applications*

The characteristic changes of the cyclic plastic stress-strain response of stainless steel and superalloys derived from the analysis of hysteresis loop at different temperatures are reported. The evolution of the surface relief in strain controlled cycling is documented using high resolution SEM and TEM. The mechanisms leading to cyclic strain localization, formation of surface relief, fatigue crack initiation and early crack growth are discussed. The study of the low cycle fatigue behavior of these materials was concentrated mostly to the analysis of the stress-strain response, internal structures, fatigue life and crack growth (1-3). In recent years, considerable attention has been attracted to the study of the early damage mechanisms in crystalline materials, starting with the cyclic slip localization and resulting finally in the initiation of fatigue cracks and their early growth (4, 5). In this contribution, the methods allowing to study the sources of cyclic stress and early fatigue damage at room and elevated temperatures are presented and used to reveal details of the mechanisms of cyclic plastic straining and fatigue damage evolution in austenitic steels and nickel superalloys. 1. Cyclic Plastic Stress-Strain Response. Cyclic plasticity of materials is usually studied in strain- controlled cycling with constant strain rate, since stress response of the material depends not only on temperature but also on the strain rate. In a standard low cycle fatigue experiment, several specimens are cycled in a symmetrical cycle with constant total or plastic strain amplitudes, and their stress response is recorded and evaluated. Hysteresis loops can be stored in computer memory, and stress, strain and plastic strain amplitudes are evaluated during the fatigue life. The plot of the stress amplitudes vs. number of loading cycles represents the fatigue hardening/softening curves. The plot of the saturated stress amplitude (or stress amplitude at half-life) vs. strain or plastic strain amplitude represents the cyclic stress-strain curve. In order to find the sources of the cyclic stress, more detailed analysis is necessary. Hysteresis loop and the analysis of its shape using the generalized statistical theory (6) can yield information on the sources of the cyclic

Low Cycle Fatigue Behavior of AA2219-T87 at Room Temperature

Abstract The low cycle fatigue behavior of AA2219-T87 was studied at ambient temperature using fully reversed total strain controlled fatigue tests in longitudinal and transverse orientations. Tension-compression cyclic tests were carried out under total strain amplitude control with strain ratio Rε = −1 and at a frequency of 0.5 Hz. The total strain amplitude was varied from ±0.4 to ±1.5 %. The low cycle fatigue results were analyzed to determine the cyclic stress strain curves. The cyclic strain hardening parameters were evaluated from the cyclic stress–strain curves. Important fatigue parameters namely fatigue ductility coefficient, fatigue ductility exponent, and fatigue strength coefficient were evaluated. The material exhibited cyclic strain softening in both longitudinal and transverse directions. Analysis of the experimental results showed that the stress–strain hysteresis loops exhibited inflections in the first few cycles and the plastic strain amplitude versus fatigue-life plots exhibited bi-linear relationship. The geometry of hysteresis loops and the occurrence of Masing behavior are analyzed and found that the alloy in peak aged condition exhibited tendency towards Masing behavior.

Using ecological whole body kinematics to evaluate effects of medication adjustment in Parkinson disease.

Functional motor impairments including mobility are major reasons for clinical intervention and medication adjustment in symptomatic therapy for Parkinson's disease (PD). Outcome measures used to assess the impact of medication are mostly based on patients' memory or diaries which, considering the gaps between visits, are neither objective nor very reliable. Investigating the feasibility of using movement features extracted from ecological whole-body kinematics recordings to measure the quantitative and qualitative changes in multiple aspects of mobility after medication changes in PD. Eleven patients with PD (PwPD) performed mobility tasks in their own home, wearing a full body wireless inertial sensing based motion capture system. Three scripted walking tasks (walking, fast walking, and walk turns) were examined at baseline and two weeks after medication changes. Clinical scales, including investigator-rated clinical global impression of improvement (CGI-I), were collected at both visits. Out of 59 recorded body joint variables, five were identified as pertinent. Changes were represented in vector space as a plot of mean versus peak amplitude. Regression analysis was used to predict clinical improvement or worsening based on these vector features. The predictors were able to explain (>98.5% of variance) patients' clinical global impression of improvement, thus correctly predicting 5 cases of improvement and 2 cases of worsening. This study provided a method of extracting clinically meaningful reports from ecological kinematic data showing changes after drug adjustments. The results are presented using a novel concept called change space that may be more understandable for clinical staff.

2.5D EM modelling in TIV conductive media and the effect of anisotropy in normalized amplitude responses

We present an integral equation framework for 2.5D frequency domain EM modelling in conductive media, i.e. in media which are assumed invariant in one direction. Furthermore, we consider media which are transversely isotropic in the vertical direction (TIV), thus allowing the horizontal and vertical conductivities to differ. The integral equation framework allows for discretization of only a very limited area of the model, given a proper background model, thus leading to a small system of equations to be solved. The 2.5D integral equation method is suitable for studying the effect of localized resistivity anomalies efficiently and makes the generalization to real-world examples easier than for 1D modelling codes. We model three experiments to analyse and better understand the uncertainties of normalized amplitude and phase difference plots. Anisotropy has a significant effect on marine controlled source electromagnetic (mCSEM) data, and normalized amplitude graphs change both magnitude and position when changing the model to which one normalizes. It suggests that interpreters should be cautious when applying this to real data, where the model that caused the response at the reference receiver is unknown and may change along the line of receivers. Finally, we investigate whether mCSEM data are likely to be able to detect conductive inclusions in the stem of a salt diapir. When the models are exactly known, normalized amplitude plots can be used to check the sensitivity to perturbations.

Comparison of acoustic emission b-values with strains in reinforced concrete beams for damage evaluation

Reinforced concrete beam specimens were tested under incremental cyclic loading and the acoustic emission released during the fracture process of concrete was used to compute the acoustic emission-based b-values. The b-value based on Gutenberg–Richter formula was calculated from the frequency–amplitude plots of acoustic emission released. The strains in steel and concrete were compared with the corresponding b-value at various stages of loading to assess damage occurred in reinforced concrete beam specimens. The code of practice IS 456:2000 has defined limits for serviceability and collapse. A brief review of the application of acoustic emission testing to concrete structures is given. It is observed that the b-value reaches its minimum near the peak load and reaches maximum during micro cracking while it tends to decrease when micro cracks coalesce and start forming major and visible cracks.

Electrophysiological and motor function scale association in a pre-symptomatic infant with spinal muscular atrophy type I

A term infant, at familial risk for spinal muscular atrophy (SMA), had the diagnosis genetically confirmed on day 3 of life. Clinical evaluation, the CHOP INTEND motor scale and the CMAP amplitude were obtained on days 5 (pre-symptomatic), 20 (mildly weak), 34 (moderately weak) and 63 (severely weak). Palliative care was provided and he expired of an acute pulmonary infection on day 81. The CMAP amplitude and INTEND scores were initially in the normal range, then followed a corresponding decline to a nadir at day 34 and remained so at the 4th assessment. A log-transformed plot of CMAP amplitude from days 5-34 was linear. These data suggest that early motor neuron loss in SMA type I may be logarithmic and demonstrates that the INTEND motor scale closely follows the CMAP electrophysiological biomarker. This single case report supports the consideration that early intervention with a potential therapy is necessary, before the pool of functional motor neurons has plummeted. Further study of these parameters in pre-symptomatic infants with SMA type I will help guide the design of future intervention studies.

Kv3 channels modulate calcium signals induced by fast firing patterns in the rat retinal ganglion cells

Expression of non-inactivating Kv3.1/Kv3.2 potassium channels determines fast-spiking phenotype of many types of neurones including retinal ganglion cells (RGCs); furthermore Kv3 channels regulate neurotransmitter release from presynaptic terminals. In the present study we investigated how inhibition of Kv3 channel by low TEA concentrations modifies firing properties and Ca2+ influx in the rat RGCs. Experiments were performed on the whole-mount retinal preparations from 4 to 6 weeks old Wistar rats using simultaneous whole cell patch clamp and intracellular Ca2+ measurements in combination with single-cell RT-PCR. In response to 500-ms depolarization step the RGCs demonstrated fast firing tonic behaviour with a mean frequency of spiking 61±5Hz (n=28). All of the tonic cells tested (n=9) expressed specific mRNA for either Kv3.1 or Kv3.2 or for both channels. Bath applications of TEA (250μM, 500μM and 1mM) modified firing patterns dose-dependently as follows: firing frequency was decreased, mean action potential (AP) half-width increased and mean amplitude of after hyperpolarization was reduced. The amplitude of the Ca2+ signals induced by the cells firing was linearly dependent on number of APs with a mean slope of 7.3±0.9nM per one AP (n=8). APs widening by TEA increased the slope of the amplitude vs. AP number plots in a dose-dependent manner: 250μM of TEA increased the mean slope value to 9.5±1.2nM/AP, 500μM to 12.4±2.4nM/AP and 1mM to 13.2±2.9nM/AP (n=6). All these parameters, as well as the cells firing properties, were significantly different from controls and from each other except between 500μM and 1mM. This is consistent with the pharmacological properties of Kv3.1/Kv3.2 channels: the TEA IC50 is in the range 150–300μM with almost complete block at 1mM. This suggests that Kv3.1/Kv3.2 channels underlie the fast firing of the rat RGCs and provide at a given firing frequency 1.8-fold restriction Ca2+ influx, thus protecting the cells from its cytotoxic action.

Riluzole blocks human muscle acetylcholine receptors

Riluzole, the only drug available against amyotrophic lateral sclerosis (ALS), has recently been shown to block muscle ACh receptors (AChRs), raising concerns about possible negative side-effects on neuromuscular transmission in treated patients. In this work we studied riluzole's impact on the function of muscle AChRs in vitro and on neuromuscular transmission in ALS patients, using electrophysiological techniques. Human recombinant AChRs composed of α(1)β(1)δ subunits plus the γ or ε subunit (γ- or ε-AChR) were expressed in HEK cells or Xenopus oocytes. In both preparations, riluzole at 0.5 μm, a clinically relevant concentration, reversibly reduced the amplitude and accelerated the decay of ACh-evoked current if applied before coapplication with ACh. The action on γ-AChRs was more potent and faster than on ε-AChRs. In HEK outside-out patches, riluzole-induced block of macroscopic ACh-evoked current gradually developed during the initial milliseconds of ACh presence. Single channel recordings in HEK cells and in human myotubes from ALS patients showed that riluzole prolongs channel closed time, but has no effect on channel conductance and open duration. Finally, compound muscle action potentials (CMAPs) evoked by nerve stimulation in ALS patients remained unaltered after a 1 week suspension of riluzole treatment. These data indicate that riluzole, while apparently safe with regard to synaptic transmission, may affect the function of AChRs expressed in denervated muscle fibres of ALS patients, with biological consequences that remain to be investigated.

Single-lobed frequency-dependent beam shape in an echolocating false killer whale (Pseudorca crassidens)

Recent studies indicate some odontocetes may produce echolocation beams with a dual-lobed vertical structure. The shape of the odontocete echolocation beam was further investigated in a false killer whale performing an echolocation discrimination task. Clicks were recorded with an array of 16 hydrophones and frequency-dependent amplitude plots were constructed to assess beam shape. The majority of the echolocation clicks were single-lobed in structure with most energy located between 20 and 80 kHz. These data indicate the false killer whale does not produce a dual-lobed structure, as has been shown in bottlenose dolphins, which may be a function of lowered frequencies in the emitted signal due to hearing loss.