Greater Discharge Rates Research Articles

A methodological approach of predicting threshold channel bank profile by multi-objective evolutionary optimization of ANFIS

More accurate stable channel design methods are necessary for analyzing the complex bank profile cross sections of alluvial channels that achieve equilibrium state. This study introduces a new hybrid method that combines an adaptive neuro-fuzzy inference system (ANFIS), Differential Evolution (DE) algorithm and Singular Value Decomposition (SVD) to predict the bank profile of a threshold channel. SVD and DE serve to optimally determine the consequent linear parameters and antecedent nonlinear parameters of the TSK-type fuzzy rules in ANFIS. Moreover, by defining two objective functions and using the Pareto curve, the tradeoff of function is selected as the optimal modeling point. The authors carried out laboratory experiments at four discharge rates of 1.16, 2.18, 2.57 and 6.20 l/s to measure the coordinates of the points in a stable channel boundary profile. The ANFIS-DE/SVD results are compared with the results of a simple ANFIS model and 7 previous research works (based on numerical and experimental models and mathematical principles). The RMSE error index (0.019) of the ANFIS-DE/SVD model is lower than the ANFIS model (0.027), but both models outperform the best available model (CKM, Cao and Knight, 1998) (RMSE = 0.120). The ANFIS-DE/SVE model is more accurate for larger y (water surface level) values than the simple ANFIS model. Moreover, the superior performance of the hybrid ANFIS-DE/SVD over the simple ANFIS model is more pronounced at greater discharge rates. ANFIS-DE/SVD estimates the bank profile shape of a stable channel as a third-degree polynomial equation, which can be used to design and implement stable alluvial channels.

Dam-break characteristics of landslide dams with different types of open channel discharge sections

The excavation of artificial open channels in landslide dams is one efficient method for reducing the risks of landslide lake formation. This method has often been used in emergencies to eliminate landslide lakes in earthquake-prone areas of Wenchuan, China. In this study, the dam-break characteristics of landslide dams with different open channel cross sections and longitudinal sections were evaluated. The degree of headward erosion was extremely strong in the natural dam-break experiment and moderately strong in the compound-section dam-break experiment. The degree of headward erosion in the open channel with the trapezoidal section was comparatively mild. Furthermore, the natural dam break resulted in large peak discharge and short dam-break duration. By contrast, the artificially opened channel dam breaks resulted in peak discharges that were approximately 7.7-20.1 % lower than those of natural dam breaks, and the dam-break duration (i.e., the time until the dam broke) was longer than that of the natural dam breaking. The channels with gentle-steep slopes or alternating gentle-steep slopes resulted in greater discharge rates, and a significant amount of erosion occurred due to these open channels. The degree of headward erosion in the channel with alternating gentle-steep slopes was greater than that in the other channels. The peak discharges of the open channels with gentle-steep slopes or alternating mild-steep slopes were approximately 29.6-65.0 % greater than those of the open channel with a linear section. A channel with a triangular cross section and a linear longitudinal section should be used to dispose of small landslide lakes. However, channels with compound cross sections and longitudinal sections with alternating slopes should be used for large or medium landslide lakes.

Types of skin afferent fibers and spinal opioid receptors that contribute to touch-induced inhibition of heart rate changes evoked by noxious cutaneous heat stimulation.

BackgroundIn anesthetized rats and conscious humans, a gentle touch using a soft disc covered with microcones (with a texture similar to that of a finger), but not with a flat disc, inhibits nociceptive somatocardiac reflexes. Such an inhibitory effect is most reliably evoked when touch is applied to the skin ipsilateral and closest to nociceptive inputs. However, the mechanism of this inhibition is not completely elucidated. We aimed to clarify the types of cutaneous afferent fibers and spinal opioid receptors that contribute to antinociceptive effects of microcone touch.ResultsThe present study comprised two experiments with urethane-anesthetized rats. In the first experiment, unitary activity of skin afferent fibers was recorded from the saphenous nerve, and responses to a 10-min touch using a microcone disc and a flat disc (control) were compared. Greater discharge rate during microcone touch was observed in low-threshold mechanoreceptive Aδ and C afferent units, whereas many Aβ afferents responded similarly to the two types of touch. In the second experiment, the effect of an intrathecal injection of opioid receptor antagonists on the inhibitory effects of microcone touch on heart rate responses to noxious heat stimulation was examined. The magnitude of the heart rate response was significantly reduced by microcone touch in rats that received saline or naltrindole (δ-opioid receptor antagonist) injections. However, such an inhibition was not observed in rats that received naloxone (non-selective opioid receptor antagonist) or Phe-Cys-Tyr-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP; μ-opioid receptor antagonist) injections.ConclusionsMicrocone touch induced greater responses of low-threshold mechanoreceptive Aδ and C afferent units than control touch. The antinociceptive effect of microcone touch was abolished by intrathecal injection of μ-opioid receptor antagonist. These results suggest that excitation of low-threshold mechanoreceptive Aδ and C afferents produces the release of endogenous μ-opioid ligands in the spinal cord, resulting in the inhibition of nociceptive transmission that contributes to somatocardiac reflexes.

Discharge rate during low-force isometric contractions influences motor unit coherence below 15 Hz but not motor unit synchronization

The purpose of the study was to determine whether pairs of motor units that discharge action potentials at different rates during isometric contractions exhibit different levels of motor unit synchronization or coherence. Twelve subjects (28.6 +/- 6.1 years) performed isometric contractions at target forces slightly above the recruitment threshold (1.02-20.9%) of an isolated motor unit. Based on audio feedback, subjects maintained a relatively constant discharge rate of the isolated unit for about 80 s. Intramuscular electrodes were used to record the discharge of 47 pairs of motor units at rates that ranged from 8.07 to 13.6 pps. Correlated discharge between pairs of motor units was quantified with the common input strength (CIS) index, k' index, and coherence spectrum. Greater discharge rates across pairs of motor units were predicted (R2 = 0.36, P < 0.001) by higher coherence from 8 to 13 Hz (r = -0.52) and lower coherence from 0 to 4 Hz (r = 0.37). Indexes of motor unit synchronization (CIS and k') were strongly associated with motor unit coherence from 16 to 32 Hz (CIS: R2 = 0.63; k': R2 = 0.4; P = 0.001). The CIS index of motor unit synchronization and the motor unit coherence from 16 to 32 Hz did not vary with discharge rate. In contrast, the k' index of motor unit synchronization declined with discharge rate (r2 = 0.20, P = 0.001). Furthermore, greater discharge rates across pairs of motor units were accompanied by higher motor unit coherence in the 8-13 Hz band and lower motor unit coherence in the 0-4 Hz band. These results demonstrate that differences in discharge rate between pairs of motor units in first dorsal interosseus during low-force, isometric contractions were associated with modulation of the correlation in the discharge times of the two motor units at frequencies less than 15 Hz.

Neural activity in primary motor and dorsal premotor cortex in reaching tasks with the contralateral versus ipsilateral arm.

To investigate the effector dependence of task-related neural activity in dorsal premotor (PMd) and primary motor cortex (M1), directional tuning functions were compared between instructed-delay reaching tasks performed separately with either the contralateral or the ipsilateral limb. During presentation of the instructional cue, the majority (55/90, 61%) of cells in PMd were tuned with both arms, and their dynamic range showed a trend for stronger discharge with the contralateral arm. Most strikingly, however, the preferred direction of most of these latter cells (41/55, 75%) was not significantly different between arms. During movement, many PMd cells continued to be tuned with both arms (53/90, 59%), with a trend for increasing directional differences between the arms over the course of the trial. In contrast, during presentation of the instructional cue only 5/74 (7%) cells in M1 were tuned with both arms. During movement, about half of M1 cells (41/74, 55%) were tuned with both arms but the preferred directions of their tuning functions were often very different and there was a strong bias toward greater discharge rates when the contralateral arm was used. Similar trends were observed for EMG activity. In conclusion, M1 is strongly activated during movements of the contralateral arm, but activity during ipsilateral arm movements is also common and usually different from that seen with the contralateral arm. In contrast, a major component of task-related activity in PMd represents movement in a more abstract or task-dependent and effector-independent manner, especially during the instructed-delay period.

The impact of defibrillator discharges on psychological functioning of implantable cardioverter defibrillator recipients

A lag exists with respect to our understanding of the psychological demands and rehabilitation needs of individuals who have undergone implantable cardioverter defibrillator (ICD) implantation. The ICD is designed to transmit an electric shock to the heart to treat a potentially life-threatening arrhythmia. This study specifically examined the impact of defibrillator discharges on the psychological functioning of ICD recipients. A questionnaire was self-administered to 33 individuals who have been living with the ICD for at least 6 months. Results revealed that levels of anger and depression were significantly higher in those subjects who reported a lower discharge rate, while sense of well-being was significantly higher in those subjects who reported a greater discharge rate. Possible explanations for our findings were proposed as well as implications for clinical intervention were discussed.

Modeling the Effects of Incorporated Residue on Rill Erosion Part II: Experimental Results and Model Validation

Laboratory experiments were conducted to collect erosion rate, soil loss, and rill geometry data to validate a computer model that simulates the effects of incorporated residue on rill erosion. Stable, equally spaced residue elements were incorporated along a single, field-scale rill to examine the effect of spacing on soil loss. The adjusted soil loss per unit length of rill, which emphasized the effect of residue spacing, increased with greater discharge rate and residue spacing. Excess scour at a residue element was negligible for spacings of 1.25 m or greater. Results from computer simulations showed that simulated results compared well to measured sediment load rates and trends in adjusted soil loss per unit length, changes in rill width over time, and final rill width at the residue. However, the simulated results in general underpredicted the total eroded soil volume and average rill width. Based on the experimental results, three out of four basic assumptions of the model were shown to be acceptable. Insufficient information was available to support a fourth assumption that transport capacity was much greater than sediment load all along the rill.

Tactile discrimination of shape: responses of slowly adapting mechanoreceptor afferents to a step stroked across the monkey fingerpad

The representation of shape in the responses of slowly adapting mechanoreceptive afferent fibers (SAs) in monkeys was investigated. A series of flat plates was used, each having an increase in thickness (a step) in the middle so that one-half of the plate was thicker than the other. The cross-sectional shape of the step approximated that of a half-cycle of a sinusoid. The height of the step was fixed at 0.5 mm, while its width (half-cycle wavelength) was varied from 0 to 3.13 mm, resulting in step shapes that varied in steepness and curvature. The steps fell into 2 categories, characterized as “steep” and “gradual.” A servocontrolled mechanical stimulator stroked each step across the distal fingerpad from the high to the low side of the step and back, while maintaining the contact force at 20 gm wt. Evoked action potentials in single SAs innervating the fingerpads of anesthetized monkeys were recorded. Each SA's response to a step provided a spatial response profile (discharge rate as a function of step position) that reflected the distribution of curvature across the step shape. All the major features of the SA response could be consistently explained as being due to the sensitivity of the SA to the amount and rate of change in skin curvature. The response profile was altered by changes in stroke direction, step shape, and stroke velocity. Differences in stroke direction (back and forth) were indicated by differences in pattern of response: a “burst-pause-burst” for strokes from high to low, and a “pause-burst-pause” for strokes from low to high; a greater discharge rate in response to the step for low to high strokes, and for some SAs, the reduction or absence of basal discharge in one of the directions. The discharge rate during the burst for either direction of stroking was greater for steep than for gradual steps, and increased, for a given step shape, with increases in stroke velocity. Regardless of differences in stroke velocity, steep steps were distinguished from gradual steps by having narrower burst widths for low-to-high strokes and narrower pause widths for high-to-low strokes. The same stimuli were delivered to the human fingerpad, and the capacities of humans to discriminate between the steps were measured. It was concluded that the spatial features of SA responses, representing the widths of regions of active and inactive SA populations, as well as the intensive feature of discharge rate, accounted for the gross sensory discriminations of shape.(ABSTRACT TRUNCATED AT 400 WORDS)

A Zinc Chlorine Molten Salt Cell

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