Reduction In Maximum Amplitude Research Articles

Rotor Bearing Casing with added Polymer Particle Composite

The trend of production machines with higher operation speeds brought the issues of vibration amplitude and acoustic emissions to the surface. To solve this problem, a standard approach requiring mass and/or stiffness increase, and utilizing high-damping polymer composite materials, e.g. by adding them to the empty spaces of the original structures is employed. The presented polymer composite application is for rotor bearing casing in which the polymer particle composite is added into the mechanical system by filling the empty space between the rotor bearing casing and the housing body. Before this application, an analysis of four polymer composite samples with different compositions was made. Then the logarithmic decrements were measured by two experimental methods and one composite was selected. The application showed acoustic emission maximum amplitude reduction of 67% and 33% when excitation amplitudes are low (up to 5 g) and large (above 10 g), respectively. In the case of the FFT spectrum of acoustic emissions, the reduction was 85% and 51%.

Improved vibration performance of a nonlinear rotor-seal system with modified labyrinth seals by an interpolating database method

Traditional studies for seal evaluation primarily focused on rotordynamic coefficients. We previously introduced two innovative labyrinth seals, the diaphragm labyrinth seal (DLS) and hole diaphragm labyrinth seal (HDLS), featuring enhanced rotordynamic and leakage characteristics. To delve into the dynamic response of these circumferentially discontinuous seals, which cannot be reduced to a 2D model, an interpolation database method (IDM) is proposed. Improved vibration performances are obtained in a nonlinear rotor-seal system with modified labyrinth seals. The Muszynska seal force model is compared with IDM for verification of accuracy. Comprehensive insights into the system's behavior were provided through metrics like the maximum Lyapunov exponent, time-domain waveform, spectrogram, Poincaré, displacement orbits, and phase maps. Results underscored IDM's accuracy for circumferentially continuous seals vis-a-vis Muszynska's model, showcasing exceptional solving abilities for discontinuous seals. Local subharmonic vibrations in rotor-DLS and rotor-HDLS systems were identified. Notably, HDLS demonstrated a 56.6% reduction in maximum amplitude compared to labyrinth seal (LS) and a 24.6% reduction compared to DLS. Maximum Lyapunov exponent outcomes emphasized HDLS’s superior stability among the three labyrinth seal types in rotor-seal system. Especially, HDLS maintained stability across diverse unbalanced mass conditions, further highlighting its versatility and application potential.

Damping of layered porous composites and an application in machinery

The structured composite can involve the porous materials providing the important internal damping that is usable in mechanical engineering applications. The stiff base material is equipped by layer/s of softer porous material/s covered by constrained layer. Such layered structure is characterized by increased internal damping in vibration process. Paper analyses some either measured or simulated mechanical properties of designed layered porous composites. Novelty provided in paper is a specific application of structured composite for damping the high frequency vibrations in resonance frequency obtaining the beneficial results, e.g. 40-48% of maximum amplitude reduction.

Experimental research on using CO2-Ar microjets to control liquid fuel combustion instability and pollutant emission

Combustion instability has become an obstacle to the development of modern gas turbines. In this study, four categories of jet tubes inject CO2-Ar mixture to the flame root at different total injection volume flow rates and mixing ratios. These jets do not change the dominant combustion instability frequency, yet the large flow rate jets can significantly weaken the pressure and the heat addition oscillations. The tube type or the CO2-Ar volume fraction in the jets has no apparent influence on the control efficacy. When the total jet volume flowrate reaches 10 L/min, the maximum amplitude reduction ratio of pulsating pressure and CH∗ chemiluminescence intensity is 90% and 89%, respectively. Meanwhile, the jets caused a significant drop in the flame temperature, and the NOx emission was reduced by at least 35%. However, the side effect of the jets is that the flame is on the verge of blowing out, and the CO emission increases sharply. The higher the volume fraction of CO2 in the jets, the more likely it is to generate CO. Designers need to compromise the impact of jets on the safety and cleanliness of the combustors.

Design and testing of a frictionless mechanical inerter device using living-hinges

In this paper a novel type of frictionless mechanical inerter device is presented, where instead of gears, motion of the flywheel is achieved using living-hinges. The design is a type of pivoted flywheel inerter inspired in part by the Dynamic Anti-resonant Vibration Isolator (DAVI) concept, which was first developed in the 1960s. Unlike the DAVI, it will be shown that the pivoted flywheel inerter has the advantage of producing balanced forces. Furthermore the use of living-hinges eliminates the need for gears or other frictional elements in the inerter mechanism. To demonstrate the utility of the new concept, a bench-top experiment was performed using a small-scale living-hinge inerter manufactured using polypropylene hinges. By estimating the experimental system parameters, the transmissibility results from the experiment could be compared to a mathematical model. These results showed that the living-hinge inerter provided an isolation effect of at least three orders of magnitude in terms of the maximum amplitude reduction from the uncontrolled system compared to that with the inerter added. Although friction was eliminated, the living-hinges did introduce additional damping, and this was found to correspond to an increase in the equivalent damping ratio for the uncontrolled system of 1.2%. It is shown that the living-hinge inerter developed in this paper fits all of the essential conditions required to be a practical inerter device. Furthermore, as it operates without mechanical friction, or fluid flow, it represents a new paradigm in experimental inerter technology.

F165. The utility of short segmental stimulation (‘Inching”) of the ulnar sensory nerve in detecting mild ulnar neuropathies at the elbow

Introduction Compressive ulnar neuropathies at the elbow (UNE) present with isolated sensory symptoms in mild and early stages. With increased severity, weakness in ulnar innervated muscles may develop and motor “inching” studies may detect focal conduction block or slowing across the elbow. Electrophysiologic techniques to localize the site of mild UNE involving only sensory fibers are limited due to the difficulty interpreting conduction block as a result of normal temporal dispersion and phase cancellation when stimulating sensory nerves over long distances. We aim to investigate the diagnostic value of ulnar sensory short segmental stimulation (“inching”) across the elbow in mild sensory UNE. Methods We performed 2-cm segmental stimulation of the ulnar sensory nerve antidromically (5th digit recording) across the elbow in 20 asymptomatic volunteers (mean age 40.5) to determine the upper limit of normal (ULN) of maximum peak latency prolongation and amplitude reduction between two adjacent stimulation sites, and the maximum amplitude reduction between wrist and above elbow (AE). Patients with classic UNE symptoms were studied to identify whether sensory inching studies determined the site of focal compression. Results In 20 normal subjects, the mean maximum peak latency shift over 2-cm elbow segments on ulnar sensory inching studies was 0.52 ms (ULN 0.6) and mean maximum percentage amplitude reduction between 2 sites was 12% (ULN 14.5%) The mean amplitude reduction between wrist and AE in the normal group was 57.7% (40.4–80.7%). Sixteen patients with clinically suspected UNE (mean age 53.5) were studied and divided in 2 groups based on routine NCS: (1) UNE cases with focal conduction block or slowing across the elbow on motor inching studies ( n = 8) and (2) suspected UNE cases with normal motor inching ( n = 8). The mean sensory maximum latency shift and % amplitude reduction between 2 elbow segments were 1.1 ms (ULN 1.35) and 21% (ULN 29.5%) in group 1; and 1.0 ms (ULN 1.3) and 22.7% (ULN 30%) in group 2. The mean amplitude reduction between wrist and AE was 84% (73.3–92.3%) in group 1 and 73.5% (55.5–90.9%) in group 2 When considering a peak sensory latency prolongation ⩾ 0.8 ms between 2 elbow stimulation sites as the criteria for an abnormal sensory “inching” study in patients with otherwise normal routine tests, 75% of patients had an abnormal test. An amplitude reduction >15% indicating sensory conduction block was found in 100% and 87.5% of patients in group 1 and 2, respectively. Conclusion Our study demonstrates that ulnar sensory short segmental stimulation across the elbow may provide diagnostic confirmation and localization in clinically suspected mild UNE when routine motor studies, including ulnar motor inching, are normal. We found that the ULN for latency shift or amplitude reduction on sensory inching studies are similar to those reported for motor inching studies ( ⩾ 0.8 ms latency prolongation and >15% amplitude reduction between two stimulation sites).

Abstract TP80: Improving Perioperative Stroke Detection During Intracranial Aneurysm Surgery Using Somatosensory Evoked Potential Waveform Analysis

Background: Current alarm criteria for evaluating impending perioperative stroke using somatosensory evoked potential (SSEP) intraoperative monitoring is a 50% reduction in amplitude or a 10% increase in latency. In this study, we aim to evaluate the diagnostic accuracy of SSEP changes for predicting perioperative stroke during intracranial aneurysm surgery. Methods: We retrospectively reviewed the intraoperative neurophysiological records of 100 patients who underwent intracranial aneurysm clipping at our institution between 2009-2013. Of those 100 patients, 25 patients incurred a new onset perioperative stroke and 75 age- and sex-matched controls did not. Quantitative analysis was done to evaluate SSEP amplitude and latency changes during various surgical events including pre-incision, incision, dural opening, before clipping (both temporary and permanent), after clipping, and during dural closure. Diagnostic accuracy was calculated as the area under the receiver operating characteristic curve (AUC) for maximum SSEP amplitude and latency changes from a baseline set at incision. Statistical analysis was performed using R Statistical Software v3.4.1. Results: The mean age (with standard deviation) of our cohort was 55.3 ± 11.2 yrs (24 male, 76 female). Preoperative rupture rate was similar in patients with perioperative stroke (36%) and controls (25%) (p=0.440). SSEP amplitude reduction was significantly greater in patients with perioperative stroke relative to controls after temporary clipping (54.6% vs. 24.3%, p<0.001). AUC for maximum amplitude reduction was calculated to be 0.80 (95% CI, 0.70-.0.90). Notably, latency prolongation was found to be a non-significant discriminator of stroke, with an AUC of 0.60 (95% CI, 0.47-0.73). AUC for 50% SSEP amplitude reduction was calculated to be 0.73 (95% CI, 0.63-0.84) and the AUC for 10% latency prolongation was found to be 0.54 (95% CI, 0.44-0.64). Conclusion: SSEP amplitude changes, but not latency changes, are strongly predictive of stroke during intracranial aneurysm surgery. However, the current alarm criteria of 50% reduction in amplitude have limited value in informing the surgeon of impending perioperative stroke due to their predictive nature.

Active Stiffness Method for High Cycle Fatigue Mitigation using Topical Thin Foil Shape Memory Alloy

The strong need for high cycle fatigue mitigation has resulted in numerous techniques resulting in added weight, increased operational costs, and lower performance. The experimental investigation presented was a foundational effort towards mitigating HCF through the use of shape memory alloy in a composite system. The research objective was to quantify changes in eigenvalue, eigenvector, and amplitude of a vibrating cantilever beam with a thin SMA topical treatment; as quantified during SMA phase transformations and through comparison with a control. A composite beam consisting of a nitinol thin SMA foil adhered to an Aluminum Alloy 6061 substrate was designed and fabricated. The three configurations were utilized: (1) a full-span SMA treatment designed for maximum eigenvalue shift and maximum amplitude reduction, (2) a half-span SMA treatment designed for eigenvector shift, and (3) a full-span aluminum treatment for a control. Through a complete modal analysis, results illustrated that thin foil SMA treatments led to a significant shift in eigenvalue, up to 6.53%. Highlighting the reduction in amplitude was a 92% reduction in amplitude at second bending with constant excitation frequency with the full-span sample. Spanwise scans on the half-span sample with and without SMA actuation illustrated a 0.77% shift in node location.

Numerical investigation of the effectiveness of a step-shaped trench in reducing train-induced vibrations

In this paper, a step-shaped trench was introduced for the attenuation of train-induced vibration levels on trackside buildings. In order to evaluate the effectiveness of the proposed type of trench in comparison with a standard rectangular trench, a two-dimensional finite element model was developed under plane strain conditions using the ABAQUS software. The validity of the preliminary model of the track including a rectangular-shaped trench was confirmed by a close agreement of obtained results with those of previous studies. The effectiveness of the step-shaped trench compared with the rectangular type was studied in open and in-filled forms in terms of decreasing the effects of ground-borne vibrations on trackside structures. The obtained results for open and in-filled step-shaped trenches respectively showed 21% and 26.2% decreases in the maximum amplitude reduction ratio with respect to the common rectangular trench. Moreover, in the case of a real train moving loads, the proposed trench shape further decreased the values of peak particle velocity, root mean square and particle velocity decibel on a trackside structure compared with the values obtained for a rectangular-shaped trench.

Effects of nucleotides and nucleosides on coagulation

Nucleotides, including ADP, ATP and uridine triphosphate (UTP), are discharged profusely in the circulation during many pathological conditions including sepsis. Sepsis can cause hypotension and systemic activation of the coagulation and fibrinolytic systems in humans, which may cause disseminated intravascular coagulation. We investigated whether nucleotide-induced cardiovascular collapse as provoked by systemic infusion of adenosine, ADP, ATP, UTP and nitric oxide affected the haemostatic system as assessed by whole blood thromboelastography (TEG) analysis. Ten pigs received a randomized infusion of adenosine, ADP, ATP, UTP or nitric oxide until mean arterial pressure was reduced to approximately 40% of baseline simulating sepsis-induced hypotension. The effect of the infusions on the haemostatic system was evaluated by TEG, and endothelial release of tissue plasminogen activator and plasminogen activator inhibitor-1 was measured. In contrast to the other infused substrates, ADP caused a reduction in maximum amplitude (71.4 to 64.2; P < 0.05), and reduced the angle, representing the thrombus formation (75.6 to 66.4; P < 0.05), indicating hypocoagulation. Despite increases in t-PA release (2.1 to 2.7 ng/ml; P < 0.05) and reductions in plasminogen activator inhibitor (33.9 +/- 10.9-17.8 +/- 4.4 ng/ml; P < 0.05) no increased fibrinolysis was found when whole blood was evaluated by TEG. Circulating ADP induces hypocoagulation without signs of increased fibrinolysis as evaluated by TEG. The potential clinical significance of these findings should be investigated further because ADP discharged systemically may possibly contribute to the coagulopathy observed in severe sepsis.

Significance of intraoperative motor function monitoring using transcranial electrical motor evoked potentials (MEP) in patients with spinal and cranial lesions near the motor pathways

Intraoperative motor evoked potential (MEP) monitoring in patients with spinal and cranial lesions is thought to be a valuable tool for prevention of postoperative motor deficits. Aim of this study was to investigate its diagnostic value in a spinal and a cranial patient group. Ninety-six patients, 31 with spinal and 65 with intracranial lesions, were studied. Transcranial stimulation was performed with a high-frequency electrical train stimulation using two subdermal needle electrodes. MEPs were recorded from the pathology-related muscles. Decreasing amplitudes of 50% or more, increasing stimulus intensities of 20% or more or increased latencies were taken as warning criteria. MEP recording was possible in 90% of the spinal and 98% of the cranial group. With two further exclusions, 28 patients of the spinal and 62 of the cranial group were analyzed. We saw a temporary maximum amplitude reduction of 50% or more and an increase in stimulation intensity of 20% or more in 8 spinal and 29 cranial patients. Five of the spinal and nine of the cranial patients deteriorated in motor function postoperatively. One patient with normal MEP monitoring showed a temporary motor weakness postoperatively. Latencies were normal in all patients. Given both warning criteria, intraoperative MEP changes had a sensitivity of 83%/ 100% and a specificity of 86%/ 62% (spinal/ cranial group). The positive predictive value of MEP changes for postoperative motor function deterioration was 63%/ 31%, and the negative predictive value was 95%/ 100%. Transcranial electrical monitoring of MEP is a practicable and safe method. However, there are many events, which can cause amplitude changes of MEP independent from surgical manipulations. Although sensitivity is high for both groups, this results in a moderate specificity for the cranial group and a low positive predictive value for both groups.

A Modification to Filtered-X LMS Control for Airfoil Vibration and Flutter Suppression

The effects of error path model dynamics and choice of reference signal on the performance of the filtered-X least main square (LMS) algorithm for active vibration and flutter suppression is investigated using a two-degree-of-freedom aeroelastic (pitch-plunge) system. It is shown that the convergence coefficient of the filtered-X LMS algorithm must vary in order to reduce vibration over a broad airspeed range. The control reduces vibration at sub-critical airspeeds and is capable of extending the critical speed by 11%. A modification to the control scheme is presented where the error path model is removed from the feedforward loop. The modified method also reduces vibration at sub-critical airspeeds while maintaining a constant convergence coefficient, and extends the critical speed by 50%. A performance study is conducted comparing the maximum amplitude reduction, settling time, and robustness to measurement noise of all control schemes presented.

Momentum-Resolved Electron-Phonon Interaction in Lead Determined by Neutron Resonance Spin-Echo Spectroscopy

Neutron resonance spin-echo spectroscopy was used to monitor the temperature evolution of the linewidths of transverse acoustic phonons in lead across the superconducting transition temperature over an extended range of the Brillouin zone. For phonons with energies below the superconducting energy gap, a linewidth reduction of maximum amplitude was observed below . The electron-phonon contribution to the phonon lifetime extracted from these data is in satisfactory overall agreement with ab initio lattice-dynamical calculations, but significant deviations are found.

A prospective, randomized comparison of thromboelastographic coagulation profile in patients receiving lactated Ringer's solution, 6% hetastarch in a balanced-saline vehicle, or 6% hetastarch in saline during major surgery

Objectives: To compare the effects of lactated Ringer's solution (LR), 6% hetastarch in a balanced-saline vehicle (HS-BS), and 6% hetastarch in normal saline (HS-NS) on coagulation using thromboelastography. Design: Prospective, randomized double-blinded evaluation of previously published clinical trial. Setting: Tertiary-care medical center. Participants: Patients undergoing elective noncardiac surgery with an anticipated blood loss >500 mL. A total of 90 patients were enrolled with 30 patients in each group. Interventions: Patients received a standardized anesthetic. LR, HS-BS, and HS-NS were administered intraoperatively based on a fluid administration algorithm. Hemodynamic targets included maintenance of arterial blood pressure, heart rate, and urine output within a predefined range. Measurements and Main Results: Thromboelastography variables for r time, k time, maximum amplitude, and α angle (mean ± SD) were recorded at induction of anesthesia, at the end of surgery, and 24 hours postoperatively. Patients in the LR group showed a state of hypercoagulation at the end of surgery with reductions (p < 0.005) in r time (−3.8 ± 6.7 mm) and k time (−1.7 ± 2.5 mm). This state of hypercoagulation continued into the postoperative period. Patients in the HS-NS group showed a state of hypocoagulation with increases (p < 0.05) in r time (+6.2 ± 8.5 mm) and k time (+1.7 ± 3.9 mm) and a reduction in maximum amplitude (−8.0 ± 9.8 mm) at the end of surgery. This state of hypocoagulation was reduced in the postoperative period. Patients in the HS-BS group showed no significant changes in coagulation status at end of surgery, with the smallest changes in r time (−0.3 ± 4.1 mm), k time (+0.1 ± 3.1 mm), maximum amplitude (−5.4 ± 12.3 mm), and α angle (0.3 ± 12.5°). Conclusion: LR-treated patients exhibited a hypercoagulative profile that persisted into the postoperative period. HS-BS administration was associated with a lesser change in the coagulation profile compared with HS-NS, which was associated with a hypocoagulative state. Copyright 2002, Elsevier Science (USA). All rights reserved.

Non-adrenergic non-cholinergic nerve-mediated inhibitory control of pigeon oesophageal muscle.

Pigeon oesophageal smooth muscle in vitro has spontaneous electromechanical activity. In the presence of atropine and guanethidine, electrical field stimulation evokes a transient TTX-sensitive response comprising inhibition of electric bursting activity and muscular relaxation. This NANC inhibitory response was analysed using the K+ channel blockers TEA and apamin, TEA perfusion (0.1-5 mM) induced a concentration-dependent reduction in amplitude of EFS-evoked relaxation. Responses to higher stimulation frequencies were more sensitive to TEA than those to lower ones. The maximum reduction in amplitude (29% of control) was obtained on 30 Hz EFS evoked responses during 5 mM TEA perfusion. In a similar way, apamin (0.01-10 microM) perfusion reduced NANC relaxation, up to 30% of control. These results suggest that in the pigeon oesophagus, NANC intramural neurons are responsible for muscular relaxation. We speculate that an increase in K+ conductance might be the main mechanism involved, although the residual response after K+ channel blockade indicates the existence of an additional ionic mechanism.

Pure-tone masking profiles for human auditory brainstem and middle latency responses to 500-Hz tones

A simultaneous masking paradigm was used to determine the frequency selectivity of human auditory brainstem (ABR) and middle latency (MLR) responses to 60 dB pe SPL 500-Hz probe tones in 12 normal adults. Masking profiles for simultaneous recordings of the ABR and MLR were obtained in the presence of pure-tone maskers presented at 60- and 70-dB SPL. Results show sharp amplitude profiles with maximum reduction in amplitude seen using the 500-Hz maskers. There were no significant differences in the masking profiles for the ABR and MLR waves to the 500-Hz probe tones. An additional measure of frequency selectivity, bandwidth at 50% reduction in amplitude (W50), also demonstrated no significant difference between the ABR and MLR waves. In summary, the results of this study and those of an earlier study (Mackersie et al., 1993) suggest no significant difference in the frequency selectivity of the ABR and MLR to low-intensity (60 dB pe SPL) 500- and 2000-Hz tones.

Suppression of the 2 f1− f2 otoacoustic emission in humans

Suppression of the 2 f 1− f 2, distortion-product otoacoustic emission (DPOAE), stimulated with primaries, f 1 and f 2 in the frequency regions of 1, 2 and 4 kHz was measured in one ear of 14 human subjects with normal hearing Suppression rate functions were generated with a suppressor at either 1, 2 or 4 kHz increasing in level from 30 to 76 dB SPL for the corresponding f 1 and f 2 combinations. Stimulus levels for DPOAEs were L 1 = 70 dB SPL and L 2 adjusted to produce the highest amplitude DPOAE for each car (range, 0 to 6 dB below L 1) Results indicated that DPOAEs were reduced 3 dB in amplitude for a mean suppressor level of 61 dB SPL. Maximum amplitude reduction occurred at a mean suppressor level of 69 dB SPL. These levels varied little for the three stimulus frequency regions. Mean slopes of the rale functions decreased as stimulus frequency region increased. Suppression tuning curves (STCs) were generated in the same three frequency regions and with L 1 at either 70 or 55 dB SPL and L 2 adjusted individually for each ear. The tips of the STCs were at frequencies associated with f 1 and f 2. The tip regions of the STCs for the 4-kHz stimulus condition were more complex in that they contained more multiple minima than did those for the 1- and 2-kHz regions. Results confirm that optimal suppression of the 2 f 1− f 2 DPOAE occurs for frequencies in the vicinity of f 1 and f 2 rather than at 2 f 1− f 2.

Concanavalin A reveals olfactory receptors which discriminate between alkane odorants on the basis of size.

For certain odorants, the amplitude of the rat electro-olfactogram is reduced if the olfactory epithelium is treated with the lectin concanavalin A. When normal and cycloalkanes of one to ten carbon atoms are used as odorants at equimolar concentration, the maximum reduction in amplitude is found to correlate with the size of the stimulus molecule. This observation is consistent with the notion that concanavalin A disables an olfactory receptor molecule which normally responds to the alkyl moiety of odorants in a particular size range. That moiety may thus represent a 'primary' quality-determining component in odour discrimination.

Hyperactive behavior and EEG arousal reactions in children

EEG arousal reactions and parameters of spontaneous EEG activity were studied in two extreme groups of behavior problem children (11 hyperactives and 11 non-hyperactives), selected on the basis of a rating of motor restlessness —the core sympton of the “hyperactivity syndrome”. The EEG was recorded in three reaction time experiments: a tone-light conditioning paradigm and two series with random stimulation. An automatic analysis of EEG parameters was employed to describe the time functions of alpha amplitudes in the single trial. The main findings are: 1. 1. In periods free from stimulation, hyperactive children have higher alpha and beta amplitudes, more alpha waves and a smaller amount of beta waves. This indicates a lower state of EEG arousal in the hyperactives. 2. 2. The amplitude reduction to tone (in the single trial) develops more slowly in the hyperactive group. This group difference increases over the experimental situations. 3. 3. The arousal responses to tone, in terms of the level of maximum amplitude reduction, become comparably weaker in the hyperactives across the experiments. 4. 4. Under all experimental conditions the hyperactives exhibit shorter arousal responses to the light stimulus than the non-hyperactive children. 5. 5. Reaction time performance of the groups is clearly different, hyperactives showing the longer latencies. 6. 6. Although conditional changes in the arousal reactions to both stimuli are reliably demonstrable in all children, the groups show no difference in the corresponding measures. These findings are discussed under the aspects of activation and of attention behavior of the subjects.