Статті в журналах з теми "Time and speed of a single movement"
Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Time and speed of a single movement.
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 статей у журналах для дослідження на тему "Time and speed of a single movement".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте статті в журналах для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Flanders, M., and U. Herrmann. "Two components of muscle activation: scaling with the speed of arm movement." Journal of Neurophysiology 67, no. 4 (April 1, 1992): 931–43. http://dx.doi.org/10.1152/jn.1992.67.4.931.
Повний текст джерелаАнотація:
1. The temporal waveform of muscle activity was related to the speed of arm movement. Speed was expressed in terms of the duration of a fixed amplitude movement or the "movement time." 2. Human subjects moved their arms to targets in three-dimensional space. The right arm started at a standard initial position and moved directly to the target in a single stroke. The targets were placed in various directions in a vertical plane. The arm movements consisted of shoulder and elbow rotations. 3. Subjects were required to vary the speed of their movements. In most of the experiments, trials with different movement times were randomly ordered. One of the experiments also included randomly interspersed static trials, in which the subject held the arm still at the initial posture, the final posture, or halfway between the two extremes. 4. Electromyographic (EMG) activity was recorded from several superficial elbow and/or shoulder muscles. The time base of rectified EMG records was normalized for movement time such that records from movements with various speeds were compressed to align the ending times of the movements. 5. A principal component (PC) analysis revealed that the compressed EMG waveforms could be described by a summation of PC1 and PC2 waveforms; each individual EMG waveform was approximated by a weighted sum of these two components. 6. The PC1 weighting coefficients scaled down in a monotonic relationship with movement time such that the fastest movement corresponded to a large positive weighting coefficient and the slowest movement corresponded to a small positive weighting coefficient. The PC2 weighting coefficients exhibited a similar monotonic scaling, but the values ranged from positive to negative. Further analysis demonstrated that these two components can be mathematically transformed into a tonic waveform with a constant mathematically transformed into a tonic waveform with a constant weighting coefficient and a phasic waveform with positive weighting coefficients that scale down with movement time. 7. The amplitude scaling of EMG records cannot be described by a single component, but instead requires a summation of two separate components. The tonic component may correspond to the force element needed to counteract gravity, because the magnitude of this element does not scale with movement speed. The phasic component may correspond to the force element that scales quadratically to produce a linear increase in velocity.
2
Corcos, D. M., G. L. Gottlieb, and G. C. Agarwal. "Organizing principles for single-joint movements. II. A speed-sensitive strategy." Journal of Neurophysiology 62, no. 2 (August 1, 1989): 358–68. http://dx.doi.org/10.1152/jn.1989.62.2.358.
Повний текст джерелаАнотація:
1. Normal human subjects made discrete flexions of the elbow over a fixed distance in the horizontal plane from a stationary initial position to a visually defined target. We measured joint angle, acceleration, and electromyograms (EMGs) from two agonist and two antagonist muscles. 2. Changes in movement speed were elicited either by explicit instruction to the subject or by adjusting the target width. Instructions always required accurately stopping in the target zone. 3. Peak inertial torques and accelerations, movement times, and integrated EMGs were all highly correlated with speed. We show that inertial torque can be used as a linking variable that is almost sufficient to explain all correlations between the task, the EMG, and movement kinematics. 4. When subjects perform tasks that require control of movement speed, they adjust the rate at which torque is developed by the muscles. This rate is modulated by the way in which the muscles are activated. The rate at which joint torque develops is correlated with the rate at which the agonist EMG rises as well as with integrated EMG. 5. The antagonist EMG shows two components. The latency of the first is 30-50 ms and independent of movement dynamics. The latency of the second component is proportional to movement time. The rate of rise and area of both components scale with torque. 6. We propose organizing principles for the control of single-joint movements in which tasks are performed by one of two strategies. These are called speed-insensitive and speed-sensitive strategies. 7. A model is proposed in which movements made under a speed-sensitive strategy are executed by controlling the intensity of an excitation pulse delivered to the motoneuron pool. The effect is to regulate the rate at which joint torque, and consequently acceleration, increases. 8. Movements of variable distance, speed, accuracy, and load are shown to be controlled by one of two consistent sets of rules for muscle activation. These rules apply to the control of both the agonist and antagonist muscles. Rules of activation lead to distinguishable patterns of EMG and torque development. All observable changes in movement kinematics are explained as deterministic consequences of these effects.
3
d'Avella, Andrea, Laure Fernandez, Alessandro Portone, and Francesco Lacquaniti. "Modulation of Phasic and Tonic Muscle Synergies With Reaching Direction and Speed." Journal of Neurophysiology 100, no. 3 (September 2008): 1433–54. http://dx.doi.org/10.1152/jn.01377.2007.
Повний текст джерелаАнотація:
How the CNS masters the many degrees of freedom of the musculoskeletal system to control goal-directed movements is a long-standing question. We have recently provided support to the hypothesis that the CNS relies on a modular control architecture by showing that the phasic muscle patterns for fast reaching movements in different directions are generated by combinations of a few time-varying muscle synergies: coordinated recruitment of groups of muscles with specific activation profiles. However, natural reaching movements occur at different speeds and require the control of both movement and posture. Thus we have investigated whether muscle synergies also underlie reaching at different speeds as well as the maintenance of stable arm postures. Hand kinematics and shoulder and elbow muscle surface EMGs were recorded in five subjects during reaches to eight targets in the frontal plane at different speeds. We found that the amplitude modulation of three time-invariant synergies captured the variations in the postural muscle patterns at the end of the movement. During movement, three phasic and three tonic time-varying synergies could reconstruct the time-normalized muscle pattern in all conditions. Phasic synergies were modulated in both amplitude and timing by direction and speed. Tonic synergies were modulated only in amplitude by direction. The directional tuning of both types of synergies was well described by a single or a double cosine function. These results suggest that muscle synergies are basic control modules that allow generating the appropriate muscle patterns through simple modulation and combination rules.
4
Herfst, Lucas J., and Michael Brecht. "Whisker Movements Evoked by Stimulation of Single Motor Neurons in the Facial Nucleus of the Rat." Journal of Neurophysiology 99, no. 6 (June 2008): 2821–32. http://dx.doi.org/10.1152/jn.01014.2007.
Повний текст джерелаАнотація:
The lateral facial nucleus is the sole output structure whose neuronal activity leads to whisker movements. To understand how single facial nucleus neurons contribute to whisker movement we combined single-cell stimulation and high-precision whisker tracking. Half of the 44 stimulated neurons gave rise to fast whisker protraction or retraction movement, whereas no stimulation-evoked movements could be detected for the remainder. Direction, speed, and amplitude of evoked movements varied across neurons. Protraction movements were more common than retraction movements ( n = 16 vs. n = 4), had larger amplitudes (1.8 vs. 0.3° for single spike events), and most protraction movements involved only a single whisker, whereas most retraction movements involved multiple whiskers. We found a large range in the amplitude of single spike-evoked whisker movements (0.06–5.6°). Onset of the movement occurred at 7.6 (SD 2.5) ms after the spike and the time to peak deflection was 18.2 (SD 4.3) ms. Each spike reliably evoked a stereotyped movement. In two of five cases peak whisker deflection resulting from consecutive spikes was larger than expected when based on linear summation of single spike-evoked movement profiles. Our data suggest the following coding scheme for whisker movements in the facial nucleus. 1) Evoked movement characteristics depend on the identity of the stimulated neuron (a labeled line code). 2) The facial nucleus neurons are heterogeneous with respect to the movement properties they encode. 3) Facial nucleus spikes are translated in a one-to-one manner into whisker movements.
5
Gottlieb, Gerald L., Daniel M. Corcos, and Gyan C. Agarwal. "Strategies for the control of voluntary movements with one mechanical degree of freedom." Behavioral and Brain Sciences 12, no. 2 (June 1989): 189–210. http://dx.doi.org/10.1017/s0140525x00048238.
Повний текст джерелаАнотація:
AbstractA theory is presented to explain how accurate, single-joint movements are controlled. The theory applies to movements across different distances, with different inertial loads, toward targets of different widths over a wide range of experimentally manipulated velocities. The theory is based on three propositions. (1) Movements are planned according to “strategies” of which there are at least two: a speed-insensitive (SI) and a speed-sensitive (SS) one. (2) These strategies can be equated with sets of rules for performing diverse movement tasks. The choice between SI and SS depends on whether movement speed and/or movement time (and hence appropriate muscle forces) must be constrained to meet task requirements. (3) The electromyogram can be interpreted as a low-pass filtered version of the controlling signal to the motoneuron pools. This controlling signal can be modelled as a rectangular excitation pulse in which modulation occurs in either pulse amplitude or pulse width. Movements to different distances and with loads are controlled by the SI strategy, which modulates pulse width. Movements in which speed must be explicitly regulated are controlled by the SS strategy, which modulates pulse amplitude. The distinction between the two movement strategies reconciles many apparent conflicts in the motor control literature.
6
Gottlieb, G. L., D. M. Corcos, and G. C. Agarwal. "Organizing principles for single-joint movements. I. A speed-insensitive strategy." Journal of Neurophysiology 62, no. 2 (August 1, 1989): 342–57. http://dx.doi.org/10.1152/jn.1989.62.2.342.
Повний текст джерелаАнотація:
1. Normal human subjects made discrete elbow flexions and extensions in the horizontal plane from a stationary initial position to visually defined targets at different distances with a constant inertial load or made flexions to a visually defined target with different inertial loads. We measured joint angle, acceleration, and electromyograms (EMGs) from two agonist and two antagonist muscles. 2. Subjects were instructed to move their limbs accurately but quickly to the targets. Movements of greater distances or lesser loads were performed at higher velocities. 3. Peak inertial torque, acceleration and velocity, movement time, and integrated, rectified EMG were all highly correlated with the task variables, distance and inertial load. We show that peak inertial torque can be used as a linking variable that is almost sufficient to explain all correlations between the tasks, the EMG, and movement kinematics. 4. The rate at which subjects initially developed torque to accelerate their movements was invariant over changes in the value of either task variable. The rising phase of the agonist EMG was also independent of the distance or load moved. 5. Two components were distinguished in the antagonist EMG. The first had a relatively constant latency and amplitude. It terminated on the onset of the second and larger component at a latency that was delayed as both distance and load increased. 6. The integrated, rectified antagonist EMG was proportional to inertial load and peak decelerating torque for changes in inertial load. When target distance varied, proportionality between peak decelerating torque and antagonist EMG could be found if correction was made for the effects of muscle length on the torque-EMG relationship. 7. We propose organizing principles for the control of single-joint human movements in which tasks are performed by one of two strategies. These are called speed-insensitive and speed-sensitive strategies. 8. A model is described in which movements made under a speed-insensitive strategy are executed by controlling the duration and the relative timing of amplitude invariant patterns of activation to the spinal motoneuron pools.
7
Filimonikhin, Gennadiy, Vladimir Pirogov, Maksim Hodunko, Ruslan Kisilov, and Vitalii Mazhara. "The dynamics of a resonance single-mass vibratory machine with a vibration exciter of targeted action that operates on the Sommerfeld effect." Eastern-European Journal of Enterprise Technologies 3, no. 7 (111) (June 17, 2021): 51–58. http://dx.doi.org/10.15587/1729-4061.2021.233960.
Повний текст джерелаАнотація:
This paper reports a study into the dynamics of a vibratory machine composed of a viscoelastically-fixed platform that can move vertically and two identical inertial vibration exciters. The vibration exciters' bodies rotate at the same angular velocities in opposite directions. The bodies host a single load in the form of a ball, roller, or pendulum. The loads' centers of mass can move relative to the bodies in a circle with a center on the axis of rotation. The loads' relative movements are hindered by the forces of viscous resistance. It was established that a vibratory machine theoretically possesses the following: – one to three oscillatory modes of movement under which loads get stuck at almost constant angular velocity and generate total unbalanced mass in the vertical direction only; – a no-oscillation mode under which loads rotate synchronously with the bodies and generate total unbalanced mass in the horizontal direction only. At the same time, only one oscillatory mode is resonant and exists at the above-the-resonance speeds of body rotation, lower than some characteristic speed. At the bodies' rotation speeds: ‒ pre-resonant; there is a globally asymptotically stable (the only existing) mode of load jams; ‒ above-the-resonance, lower than the characteristic velocity; there are locally asymptotically stable regimes ‒ both the resonance mode of movement of a vibratory machine and a no-oscillations mode; ‒ exceeding the characteristic velocity: there is a globally asymptotically stable no-oscillations mode. Computational experiments have confirmed the results of theoretical research. At the same time, it was additionally established that it would suffice, to enter a resonant mode of movement, to slowly accelerate the bodies of vibration exciters to the above-the-resonance speed, less than the characteristic speed. The results reported here could be interesting both for the theory and practice of designing new vibratory machines
8
Prosen, Jerneja, Nic James, Lygeri Dimitriou, Janez Perš, and Goran Vučković. "A Time-Motion Analysis of Turns Performed by Highly Ranked Viennese Waltz Dancers." Journal of Human Kinetics 37, no. 1 (June 1, 2013): 55–62. http://dx.doi.org/10.2478/hukin-2013-0025.
Повний текст джерелаАнотація:
Twenty-four dance couples performing at the 2011 IDSF (International DanceSport Federation) International Slovenia Open were divided into two groups: the first twelve placed couples (top ranked) and the last twelve placed couples (lower ranked). Video recordings were processed automatically using computer vision tracking algorithms under operator supervision to calculate movement parameters. Time and speed of movement were analysed during single natural (right) and reverse (left) turns performed during the Viennese waltz. Both top and lower ranked dancers tended to perform similar proportionate frequencies of reverse (≈ 35%) and natural (≈ 65%) turns. Analysis of reverse turns showed that the top ranked dancers performed less turns on a curved trajectory (16%) than the lower ranked dancers (33%). The top ranked couples performed all turns at similar speeds (F = 1.31, df = 3, p = 0.27; mean = 2.09m/s) all of which were significantly quicker than the lower ranked couples (mean = 1.94m/s), the greatest differences found for reverse turns (12.43% faster for curved trajectories, 8.42% for straight trajectories). This suggests that the ability to maintain a high speed in the more difficult turns, particularly the reverse turns on a curved trajectory, results in the overall dance appearing more fluent as the speed of movement does not fluctuate as much. This aspect of performance needs to be improved by lower ranked dancers if they wish to improve rating of their performance. Future research should determine which factors relate to the speed of turns.
9
Gribble, Paul L., David J. Ostry, Vittorio Sanguineti, and Rafael Laboissière. "Are Complex Control Signals Required for Human Arm Movement?" Journal of Neurophysiology 79, no. 3 (March 1, 1998): 1409–24. http://dx.doi.org/10.1152/jn.1998.79.3.1409.
Повний текст джерелаАнотація:
Gribble, Paul L., David J. Ostry, Vittorio Sanguineti, and Rafael Laboissière. Are complex control signals required for human arm movement? J. Neurophysiol. 79: 1409–1424, 1998. It has been proposed that the control signals underlying voluntary human arm movement have a “complex” nonmonotonic time-varying form, and a number of empirical findings have been offered in support of this idea. In this paper, we address three such findings using a model of two-joint arm motion based on the λ version of the equilibrium-point hypothesis. The model includes six one- and two-joint muscles, reflexes, modeled control signals, muscle properties, and limb dynamics. First, we address the claim that “complex” equilibrium trajectories are required to account for nonmonotonic joint impedance patterns observed during multijoint movement. Using constant-rate shifts in the neurally specified equilibrium of the limb and constant cocontraction commands, we obtain patterns of predicted joint stiffness during simulated multijoint movements that match the nonmonotonic patterns reported empirically. We then use the algorithm proposed by Gomi and Kawato to compute a hypothetical equilibrium trajectory from simulated stiffness, viscosity, and limb kinematics. Like that reported by Gomi and Kawato, the resulting trajectory was nonmonotonic, first leading then lagging the position of the limb. Second, we address the claim that high levels of stiffness are required to generate rapid single-joint movements when simple equilibrium shifts are used. We compare empirical measurements of stiffness during rapid single-joint movements with the predicted stiffness of movements generated using constant-rate equilibrium shifts and constant cocontraction commands. Single-joint movements are simulated at a number of speeds, and the procedure used by Bennett to estimate stiffness is followed. We show that when the magnitude of the cocontraction command is scaled in proportion to movement speed, simulated joint stiffness varies with movement speed in a manner comparable with that reported by Bennett. Third, we address the related claim that nonmonotonic equilibrium shifts are required to generate rapid single-joint movements. Using constant-rate equilibrium shifts and constant cocontraction commands, rapid single-joint movements are simulated in the presence of external torques. We use the procedure reported by Latash and Gottlieb to compute hypothetical equilibrium trajectories from simulated torque and angle measurements during movement. As in Latash and Gottlieb, a nonmonotonic function is obtained even though the control signals used in the simulations are constant-rate changes in the equilibrium position of the limb. Differences between the “simple” equilibrium trajectory proposed in the present paper and those that are derived from the procedures used by Gomi and Kawato and Latash and Gottlieb arise from their use of simplified models of force generation.
10
Cooper, Jr., William. "Foraging movements by the ambush-foraging striped plateau lizard (Sceloporus virgatus) vary between sexes and with air temperature, but not with distance to an immobile observer or time of day." Amphibia-Reptilia 32, no. 2 (2011): 203–12. http://dx.doi.org/10.1163/017353711x557014.
Повний текст джерелаАнотація:
AbstractLizard foraging activity is assessed quantitatively by measuring various aspects of activity including number of movements per minute (MPM), proportion of time spent moving (PTM), average speed over an observation period (AS), and speed while moving (MS). With some exceptions, single estimates are given without considering possible effects of environmental variables such as air temperature and time of day. Effects of distance between lizard and observer during observation, the standing distance, have not been studied previously. I measured foraging movements in a phrynosomatid ambush forager, Sceloporus virgatus, early in the breeding season to examine possible effects of sex, air temperature, time of day, and standing distance. Males had higher values of all four foraging movement variables than females. The major cause of this difference is presumably greater socially motivated movement by males, which have much larger home ranges than females. Decreased female foraging probably contributed to the difference because gravid and possibly late vitellogenic females reduce feeding and might become less mobile to reduce the likelihood of being detected by predators when a heavy clutch reduces running speed. Time of day and standing distance did not affect foraging movements. MPM, PTM, and AS decreased as temperature increased, but these effects were small. All pairs of MPM, PTM, and AS were positively correlated, but MS was correlated only with AS, and weakly. I discuss reasons for intraspecific and interspecific correlations among movement variables.
11
McLaren, James D., Judy Shamoun-Baranes, Adriaan M. Dokter, Raymond H. G. Klaassen, and Willem Bouten. "Optimal orientation in flows: providing a benchmark for animal movement strategies." Journal of The Royal Society Interface 11, no. 99 (October 6, 2014): 20140588. http://dx.doi.org/10.1098/rsif.2014.0588.
Повний текст джерелаАнотація:
Animal movements in air and water can be strongly affected by experienced flow. While various flow-orientation strategies have been proposed and observed, their performance in variable flow conditions remains unclear. We apply control theory to establish a benchmark for time-minimizing (optimal) orientation. We then define optimal orientation for movement in steady flow patterns and, using dynamic wind data, for short-distance mass movements of thrushes ( Turdus sp.) and 6000 km non-stop migratory flights by great snipes, Gallinago media. Relative to the optimal benchmark, we assess the efficiency (travel speed) and reliability (success rate) of three generic orientation strategies: full compensation for lateral drift, vector orientation (single-heading movement) and goal orientation (continually heading towards the goal). Optimal orientation is characterized by detours to regions of high flow support, especially when flow speeds approach and exceed the animal's self-propelled speed. In strong predictable flow (short distance thrush flights), vector orientation adjusted to flow on departure is nearly optimal, whereas for unpredictable flow (inter-continental snipe flights), only goal orientation was near-optimally reliable and efficient. Optimal orientation provides a benchmark for assessing efficiency of responses to complex flow conditions, thereby offering insight into adaptive flow-orientation across taxa in the light of flow strength, predictability and navigation capacity.
12
Feigl, Tobias, Sebastian Kram, Philipp Woller, Ramiz H. Siddiqui, Michael Philippsen, and Christopher Mutschler. "RNN-Aided Human Velocity Estimation from a Single IMU." Sensors 20, no. 13 (June 29, 2020): 3656. http://dx.doi.org/10.3390/s20133656.
Повний текст джерелаАнотація:
Pedestrian Dead Reckoning (PDR) uses inertial measurement units (IMUs) and combines velocity and orientation estimates to determine a position. The estimation of the velocity is still challenging, as the integration of noisy acceleration and angular speed signals over a long period of time causes large drifts. Classic approaches to estimate the velocity optimize for specific applications, sensor positions, and types of movement and require extensive parameter tuning. Our novel hybrid filter combines a convolutional neural network (CNN) and a bidirectional recurrent neural network (BLSTM) (that extract spatial features from the sensor signals and track their temporal relationships) with a linear Kalman filter (LKF) that improves the velocity estimates. Our experiments show the robustness against different movement states and changes in orientation, even in highly dynamic situations. We compare the new architecture with conventional, machine, and deep learning methods and show that from a single non-calibrated IMU, our novel architecture outperforms the state-of-the-art in terms of velocity (≤0.16 m/s) and traveled distance (≤3 m/km). It also generalizes well to different and varying movement speeds and provides accurate and precise velocity estimates.
13
Gottlieb, Gerald L. "Muscle Activation Patterns During Two Types of Voluntary Single-Joint Movement." Journal of Neurophysiology 80, no. 4 (October 1, 1998): 1860–67. http://dx.doi.org/10.1152/jn.1998.80.4.1860.
Повний текст джерелаАнотація:
Gottlieb, Gerald L. Muscle activation patterns during two types of voluntary single-joint movement. J. Neurophysiol. 80: 1860–1867, 1998. We examined the systematic variations in the EMG patterns during two types of single joint elbow movements. These patterns may be interpreted as exhibiting rules by which the CNS controls movement parameters. Normal human subjects performed two series of fast elbow flexion movements of 20–100° in a horizontal plane manipulandum. The first series consisted of pointing movements (PMs) from an initial position to a target; the second series consisted of reversal movements (RMs) to the same targets with an immediate return to the starting position. Both series showed kinematic and electromyographic (EMG) patterns that followed our previously described speed-insensitive strategy for controlling movement distance. Kinematic patterns of PMs and RMs were identical to about the time of peak PM deceleration. Agonist EMG bursts were also initially the same, but RM bursts ended abruptly in a silent period, whereas PM bursts declined more gradually. Antagonist EMG bursts of RMs were later than those of PMs but were not larger, contrary to our prior expectation and despite the larger net extension torque during RMs. The increase in net RM extension-directed torque that takes the limb back to its initial position appears to be a consequence of reduced flexor muscle torque rather than increased extensor muscle torque. We propose that rules for movement control may be similar for different kinds of movements as long as they are functionally sufficient for the task. However, even in a single-joint movement paradigm, physics alone, that is, the knowledge of net muscle torque and limb kinematics, is not adequate to fully predict those rules or the muscle activation patterns they produce. These must be discovered by experiment. The simplest expression of such rules may not be in terms of torque or kinematic variables but rather explicitly in terms of muscle activation patterns.
14
Corcos, D. M., G. C. Agarwal, B. P. Flaherty, and G. L. Gottlieb. "Organizing principles for single-joint movements. IV. Implications for isometric contractions." Journal of Neurophysiology 64, no. 3 (September 1, 1990): 1033–42. http://dx.doi.org/10.1152/jn.1990.64.3.1033.
Повний текст джерелаАнотація:
1. Normal human subjects made isometric pulse and step contractions about the elbow to visually defined target torques of different amplitudes and at different rates. We measured joint torque and electromyograms (EMG) from two agonist and two antagonist muscles. 2. When the task specification requires that the subject explicitly alter the rate at which torque is increased, the rates of rise of the agonist and antagonist EMG bursts covary with the rate of rise of the torque. For pulses of torque the duration of motoneuron excitation varies with the duration of the task-defined contractile event. 3. When a subject is asked to generate torques of different amplitudes without specifying a time interval, torque amplitude is positively correlated with how long, and therefore how high, the EMG rose. Subjects usually proportionately covary the strength of the agonist and antagonist contractions but are not constrained to do so. Some subjects use a strategy of varying the antagonist inversely with the agonist contraction. 4. We extend the organizing principles for the control of movement about a single joint to the control of isometric torque. These rules state that control of torque about a single joint is exercised by one of two strategies: the speed-sensitive strategy modulates the rate at which contraction rises by varying the intensity of motoneuron-pool excitation. The speed-insensitive strategy varies the duration over which contraction rises but does not change the rate. These two respective patterns of torque emerge from pulse-height and pulse-width modulation of motoneuron-pool excitation. 5. The rules defining speed-sensitive and speed-insensitive strategies for movements are broadened for isometric contractions because of the wider range of torque patterns that we observe under these conditions. We propose a step-excitation component for prolonged isometric step contractions and slowly rising ramp patterns of excitation for contractions that develop over several hundreds of milliseconds. 6. The choice of strategies is based on task-specific torque requirements. The same two strategies that control torque to produce movement apply to the control of isometric torque. Unlike movements, however, isometric tasks are more often controlled by a blending of the two patterns. Possible reasons for this are discussed.
15
Yoon, Tehrim, Robert B. Geary, Alaa A. Ahmed, and Reza Shadmehr. "Control of movement vigor and decision making during foraging." Proceedings of the National Academy of Sciences 115, no. 44 (October 15, 2018): E10476—E10485. http://dx.doi.org/10.1073/pnas.1812979115.
Повний текст джерелаАнотація:
During foraging, animals decide how long to stay at a patch and harvest reward, and then, they move with certain vigor to another location. How does the brain decide when to leave, and how does it determine the speed of the ensuing movement? Here, we considered the possibility that both the decision-making and the motor control problems aimed to maximize a single normative utility: the sum of all rewards acquired minus all efforts expended divided by total time. This optimization could be achieved if the brain compared a local measure of utility with its history. To test the theory, we examined behavior of people as they gazed at images: they chose how long to look at the image (harvesting information) and then moved their eyes to another image, controlling saccade speed. We varied reward via image content and effort via image eccentricity, and then, we measured how these changes affected decision making (gaze duration) and motor control (saccade speed). After a history of low rewards, people increased gaze duration and decreased saccade speed. In anticipation of future effort, they lowered saccade speed and increased gaze duration. After a history of high effort, they elevated their saccade speed and increased gaze duration. Therefore, the theory presented a principled way with which the brain may control two aspects of behavior: movement speed and harvest duration. Our experiments confirmed many (but not all) of the predictions, suggesting that harvest duration and movement speed, fundamental aspects of behavior during foraging, may be governed by a shared principle of control.
16
Moran, Daniel W., and Andrew B. Schwartz. "Motor Cortical Representation of Speed and Direction During Reaching." Journal of Neurophysiology 82, no. 5 (November 1, 1999): 2676–92. http://dx.doi.org/10.1152/jn.1999.82.5.2676.
Повний текст джерелаАнотація:
The motor cortical substrate associated with reaching was studied as monkeys moved their hands from a central position to one of eight targets spaced around a circle. Single-cell activity patterns were recorded in the proximal arm area of motor cortex during the task. In addition to the well-studied average directional selectivity (“preferred direction”) of single-cell activity, we also found the time-varying speed of movement to be represented in the cortical activity. A single equation relating motor cortical discharge rate to these two parameters was developed. This equation, which has both independent (speed only) and interactive (speed and direction) components, described a large portion of the time-varying motor cortical activity during the task. Electromyographic activity from a number of upper arm muscles was recorded during this task. Muscle activity was also found to be directionally tuned; however, the distributions of preferred directions were found to be significantly different from cortical activity. In addition, the effect of speed on cortical and muscle activity was also found to be significantly different.
17
Honma, Keisuke, Yuki Yano, Saki Yamamoto, Toshimitsu Ohmine, Hideyuki Wanaka, Kazuma Senzaki, Atsuki Kanayama, Hiroyuki Oonishi, and Akira Iwata. "Immediate Effects of Single-Session High-Velocity Training for Lateral Trunk Movement on Gait Function in Early Postoperative Patients after Total Hip Arthroplasty: A Nonrandomized Controlled Trial." Healthcare 10, no. 2 (January 28, 2022): 256. http://dx.doi.org/10.3390/healthcare10020256.
Повний текст джерелаАнотація:
Background: Total Hip Arthroplasty (THA) is an effective method for relieving pain and improving gait function. However, THA patients demonstrate slow gait speed at discharge. Rehabilitation programs after THA require the immediate improvement of gait speed early in the postoperative period. To examine the immediate effects of seated side tapping training (SSTT), which focuses on lateral trunk movement and movement velocity, on gait function in early postoperative THA patients, the methods were as follows: The SSTT group performed five repetitions of a task in which they moved their trunks laterally to alternately touch markers to their left and right side as quickly as possible 10 times in a seated position. One set of SSTT lasted approximately 3 min. The control group rested in a seated position for 10 min. Results: Significant interactions were observed for gait speed, stride time, and stride time coefficient of variability. The SSTT group demonstrated significant pre-post-intervention improvement in gait speed, stride time, and coefficient of variability. Conclusions: SSTT improved both gait speed and gait stability and can be performed easily and safely. Therefore, single-session high-velocity trunk training may be an effective method to improve gait function immediately in early postoperative THA patients.
18
Yang, Weidong, та Siegfried M. Musser. "Nuclear import time and transport efficiency depend on importin β concentration". Journal of Cell Biology 174, № 7 (18 вересня 2006): 951–61. http://dx.doi.org/10.1083/jcb.200605053.
Повний текст джерелаАнотація:
Although many components and reaction steps necessary for bidirectional transport across the nuclear envelope (NE) have been characterized, the mechanism and control of cargo migration through nuclear pore complexes (NPCs) remain poorly understood. Single-molecule fluorescence microscopy was used to track the movement of cargos before, during, and after their interactions with NPCs. At low importin β concentrations, about half of the signal-dependent cargos that interacted with an NPC were translocated across the NE, indicating a nuclear import efficiency of ∼50%. At high importin β concentrations, the import efficiency increased to ∼80% and the transit speed increased approximately sevenfold. The transit speed and import efficiency of a signal-independent cargo was also increased by high importin β concentrations. These results demonstrate that maximum nucleocytoplasmic transport velocities can be modulated by at least ∼10-fold by the importin β concentration and therefore suggest a potential mechanism for regulating the speed of cargo traffic across the NE.
19
Novikov, Arthur, Michael Drapalyuk, Olga Dornyak, Vladimir Zelikov, and Vladan Ivetić. "The Effect of Motion Time of a Scots Pine Single Seed on Mobile Optoelectronic Grader Efficiency: A Mathematical Patterning." Inventions 4, no. 4 (September 25, 2019): 55. http://dx.doi.org/10.3390/inventions4040055.
Повний текст джерелаАнотація:
Research Highlights: Forest owners will be able to solve the problem of testing and selection of viable forest seeds on location and save financial, time, and material resources. The possibility of integrating non-destructive quality control and separation functions in a single portable apparatus is extremely promising. The speed of the contemporary optoelectronic grader is limited by the speed of the slowest component—the mechanical system. Background and Objectives: The technological process of forest seed establishment and design of optoelectronic graders is based on a priori mathematical modeling of structural characteristics, taking into account these criteria. Known models of industrial photoseparators are expensive and have a high energy and material consumption not applicable in the field. Laboratory seed analyzers are characterized by a long time exposure, and the overall size and level of climatic performance do not allow them to be used in the field. Consequently, for small amounts of seed treatment, it is necessary to orient the seeds one by one and ensure clear and rapid coordinated actions of optoelectronic and mechanical systems. The main goal of this research is to increase the efficiency of grading forest seeds by patterning the speed of the mobile device. We will answer the following questions. What are effective geometric parameters for the seed pipe? What factors affect the speed of a single seed’s movement? Materials and Methods: This study is based on mathematical modeling, taking into account the basic principles of mechanics, using MatLab software. Results: A mechanical model of a single Scots pine seed’s motion in different zones of the seed pipe is designed, taking into account air resistance. The effective height of the seed pipe, taking into account the response time of optoelectronic grader systems, is determined. Conclusions: The time and speed of single seed movement through grader systems depends on the seed pipe’s height and radius of curvature. Other things being equal, through the use of the same optical scheme with a microprocessor to solve various problems, the compactness of the photodetector scheme allows, if necessary, to upgrade the grader to solve research problems and for use in forestry.
20
Bitigova, Dayana, Dinar Bekzhanov, and Saule Bekzhanova. "ENSURING TRAIN SAFETY ON HIGH-SPEED RAIL-HIGHWAY." Вестник КазАТК 118, no. 3 (September 17, 2021): 28–33. http://dx.doi.org/10.52167/1609-1817-2021-118-3-28-33.
Повний текст джерелаАнотація:
Modern high-speed trains in normal operation develop speeds of up to 350-400 km / h, and in tests they can even accelerate to 560-580 km/h. Due to the speed of service and high speed of movement, they seriously compete with other modes of transport, while maintaining such a property of all trains as low cost of transportation with a large volume of passenger traffic. For the first time the regular movement of high-speed trains began in 1964 in Japan under the Shinkansen project. In 1981, VSNT trains began to run in France, and soon most of Western Europe, including even the island of Great Britain, became connected by a single high-speed rail network. At the beginning of the XXI century, China became the world leader in the development of a network of high-speed lines, as well as the operator of the first regular high-speed maglev.In Russia, the regular operation of high-speed trains "Sapsan", on common tracks with conventional trains, began at the end of 2009. Since 2013, the idea of building the first specialized high-speed railway Moscow-Kazan (cargo-passenger) for the national high-speed traffic system has been discussed.Most of the high-speed trains carry passengers, but there are varieties designed for the transport of goods. For example, the French service La Poste has used special TGV electric trains for 30 years, which served to transport mail and parcels (their operation was completed in June 2015 due to the decrease in the volume of mailings in recent years).
21
Bitigova, Dayana, Dinar Bekzhanov, and Saule Bekzhanova. "ENSURING TRAIN SAFETY ON HIGH-SPEED RAIL-HIGHWAY." Вестник КазАТК 118, no. 3 (September 17, 2021): 28–33. http://dx.doi.org/10.52167/1609-1817-2021-118-3-28-33.
Повний текст джерелаАнотація:
Modern high-speed trains in normal operation develop speeds of up to 350-400 km / h, and in tests they can even accelerate to 560-580 km/h. Due to the speed of service and high speed of movement, they seriously compete with other modes of transport, while maintaining such a property of all trains as low cost of transportation with a large volume of passenger traffic. For the first time the regular movement of high-speed trains began in 1964 in Japan under the Shinkansen project. In 1981, VSNT trains began to run in France, and soon most of Western Europe, including even the island of Great Britain, became connected by a single high-speed rail network. At the beginning of the XXI century, China became the world leader in the development of a network of high-speed lines, as well as the operator of the first regular high-speed maglev.In Russia, the regular operation of high-speed trains "Sapsan", on common tracks with conventional trains, began at the end of 2009. Since 2013, the idea of building the first specialized high-speed railway Moscow-Kazan (cargo-passenger) for the national high-speed traffic system has been discussed.Most of the high-speed trains carry passengers, but there are varieties designed for the transport of goods. For example, the French service La Poste has used special TGV electric trains for 30 years, which served to transport mail and parcels (their operation was completed in June 2015 due to the decrease in the volume of mailings in recent years).
22
Torres, Elizabeth, and Richard Andersen. "Space–Time Separation During Obstacle-Avoidance Learning in Monkeys." Journal of Neurophysiology 96, no. 5 (November 2006): 2613–32. http://dx.doi.org/10.1152/jn.00188.2006.
Повний текст джерелаАнотація:
Is the movement duration time known before we move? To answer this question, a new experimental paradigm is introduced that for the first time monitors the acquisition of a new motor skill in rhesus monkeys. Straight reaches were interleaved with reaches around physical obstacles that elicited a different path geometry. Curved and longer spatial paths were immediately resolved and consistent over months of training. A new temporal strategy separately evolved over repetitions from multiple to a single velocity peak. We propose that the obstacle-avoidance spatial paths were resolved before motion execution and used as reference in the computation of the new dynamics. Path conservation from the first trial occurred both at the hand and at the joint angle levels, whereas the speed profile dramatically changed over time. The spatial solution required no learning and was anticipated by the spontaneous repositioning of the initial arm posture. The learning was in the temporal domain, involving the adjustment of the speed during the motion's first impulse. Within the movement initiation, the partial distance traveled by the hand up to the first velocity peak was finely tuned under a constant time. For a given space location, the time of the first impulse remained robust to learning, but significantly shifted for different targets and obstacle configurations. Differences in the temporal-related parameters across time provided a clear distinction between learning and automatic behavior.
23
Kang, Tey Wei, Lim Thol Yong, Yeong Che Fai, and Eileen Su Lee Ming. "Design and Development of an Omnidirectional Mobile Robot." Applied Mechanics and Materials 432 (September 2013): 494–99. http://dx.doi.org/10.4028/www.scientific.net/amm.432.494.
Повний текст джерелаАнотація:
Most mobile robots use differential-drive concept, where they are equipped with two actuators that permit only single-direction rotation at a time. This concept limits the robots navigation because its orientation must always change according to the direction of movement. This paper presents the development of an omnidirectional mobile robot that uses three actuators, aligned in 120 degrees separation and each attached to an omniwheel. By manipulating actuator speed, the robot can navigate to any direction without changing its orientation. UsingNIsbRIO9632xtas the main controller, navigation algorithm is implemented in LabVIEW, integrated with PID controller to fine-tune robot movements.
24
Dépeault, Alexandra, El-Mehdi Meftah, and C. Elaine Chapman. "Tactile Speed Scaling: Contributions of Time and Space." Journal of Neurophysiology 99, no. 3 (March 2008): 1422–34. http://dx.doi.org/10.1152/jn.01209.2007.
Повний текст джерелаАнотація:
A major challenge for the brain is to extract precise information about the attributes of tactile stimuli from signals that co-vary with multiple parameters, e.g., speed and texture in the case of scanning movements. We determined the ability of humans to estimate the tangential speed of surfaces moved under the stationary fingertip and the extent to which the physical characteristics of the surfaces modify speed perception. Scanning speed ranged from 33 to 110 mm/s (duration of motion constant). Subjects could scale tactile scanning speed, but surface structure was essential because the subjects were poor at scaling the speed of a moving smooth surface. For textured surfaces, subjective magnitude estimates increased linearly across the range of speeds tested. The spatial characteristics of the surfaces influenced speed perception, with the roughest surface (8 mm spatial period, SP) being perceived as moving 15% slower than the smoother, textured surfaces (2–3 mm SP). Neither dot disposition (periodic, non periodic) nor dot density contributed to the results, suggesting that the critical factor was dot spacing in the direction of the scan. A single monotonic relation between subjective speed and temporal frequency (speed/SP) was obtained when the ratings were normalized for SP. This provides clear predictions for identifying those cortical neurons that play a critical role in tactile motion perception and the underlying neuronal code. Finally, the results were consistent with observations in the visual system (decreased subjective speed with a decrease in spatial frequency, 1/SP), suggesting that stimulus motion is processed similarly in both sensory systems.
25
Churchland, Mark M., and Krishna V. Shenoy. "Temporal Complexity and Heterogeneity of Single-Neuron Activity in Premotor and Motor Cortex." Journal of Neurophysiology 97, no. 6 (June 2007): 4235–57. http://dx.doi.org/10.1152/jn.00095.2007.
Повний текст джерелаАнотація:
The relationship between neural activity in motor cortex and movement is highly debated. Although many studies have examined the spatial tuning (e.g., for direction) of cortical responses, less attention has been paid to the temporal properties of individual neuron responses. We developed a novel task, employing two instructed speeds, that allows meaningful averaging of neural responses across reaches with nearly identical velocity profiles. Doing so preserves fine temporal structure and reveals considerable complexity and heterogeneity of response patterns in primary motor and premotor cortex. Tuning for direction was prominent, but the preferred direction was frequently inconstant with respect to time, instructed-speed, and/or reach distance. Response patterns were often temporally complex and multiphasic, and varied with direction and instructed speed in idiosyncratic ways. A wide variety of patterns was observed, and it was not uncommon for a neuron to exhibit a pattern shared by no other neuron in our dataset. Response patterns of individual neurons rarely, if ever, matched those of individual muscles. Indeed, the set of recorded responses spanned a much higher dimensional space than would be expected for a model in which neural responses relate to a moderate number of factors—dynamic, kinematic, or otherwise. Complex responses may provide a basis-set representing many parameters. Alternately, it may be necessary to discard the notion that responses exist to “represent” movement parameters. It has been argued that complex and heterogeneous responses are expected of a recurrent network that produces temporally patterned outputs, and the present results would seem to support this view.
26
Marmeleira, José Francisco Filipe, Filipe Manuel Soares de Melo, Mouhaydine Tlemcani, and Mário Adriano Bandeira Godinho. "Exercise Can Improve Speed of Behavior in Older Drivers." Journal of Aging and Physical Activity 19, no. 1 (January 2011): 48–61. http://dx.doi.org/10.1123/japa.19.1.48.
Повний текст джерелаАнотація:
The main aim of this research was to study the effects of a specific exercise program on the speed of behavior of older adults during on-the-road driving. Twenty-six drivers (55–78 yr old) were randomly assigned to either an exercise group or a control group. The exercise program (3 sessions of 60 min/wk for 8 wk) incorporated tasks that induced the participants to respond quickly to challenging situations. On-the-road driving tasks (under single- and dual-task conditions) included measures of simple and choice reaction time, movement time, and response time. Significant positive effects were found at follow-up resulting from participation in the exercise program: Improvements were found for several measures in all driving tasks, and a composite score reflected a better general drivers’ speed of behavior. These results show that exercise can enhance speed of behavior in older drivers and should therefore be promoted.
27
Gray, Vicki L., Larissa M. Juren, Tanya D. Ivanova, and S. Jayne Garland. "Retraining Postural Responses With Exercises Emphasizing Speed Poststroke." Physical Therapy 92, no. 7 (March 15, 2012): 924–34. http://dx.doi.org/10.2522/ptj.20110432.
Повний текст джерелаАнотація:
Background Postural responses are impaired after stroke, with reduced or delayed muscle activity in the paretic leg muscles. Objective The efficacy of exercises emphasizing speed of movement in modifying postural responses to perturbations that were not practiced was investigated. Design This was a dual cohort design. Methods A convenience sample of 32 individuals with hemiparesis poststroke (mean number of weeks poststroke=11.3, SD=4.1) who were recruited upon discharge from an inpatient rehabilitation hospital and a control group of age- and sex-matched individuals who were healthy (n=32) performed a single session of exercise emphasizing speed of movement. To assess postural responses to internal perturbation, unilateral arm raise and load drop tasks were performed before exercises (pre-exercise), immediately after exercises (post-exercise), and 15 minutes after exercises (retention). The time to burst peak and area of the biceps femoris muscle (BF) electromyographic (EMG) activity in the arm raise task was measured with the arm acceleration and velocity of the center of pressure (COP) excursion. For the load drop task, the anticipatory EMG deactivation area of the BF was calculated. In both tasks, the vertical ground reaction forces were recorded for each leg separately. Results Before exercise, EMG and force platform measures were smaller in the stroke group than in the control group. After exercise, the paretic BF time to burst peak decreased, the paretic BF EMG area increased, and the COP velocity increased in the arm raise task, as did the paretic BF anticipatory EMG deactivation area in the load drop task. The stroke group was weight bearing more symmetrically after exercises. Most changes were retained 15 minutes after the exercises. Limitations The retention period was short, and there was no control group of individuals with stroke. Conclusions The results of this efficacy study demonstrated that fast movement exercises improved postural responses to perturbations that were not practiced.
28
Siegert, F., C. J. Weijer, A. Nomura, and H. Miike. "A gradient method for the quantitative analysis of cell movement and tissue flow and its application to the analysis of multicellular Dictyostelium development." Journal of Cell Science 107, no. 1 (January 1, 1994): 97–104. http://dx.doi.org/10.1242/jcs.107.1.97.
Повний текст джерелаАнотація:
We describe the application of a novel image processing method, which allows quantitative analysis of cell and tissue movement in a series of digitized video images. The result is a vector velocity field showing average direction and velocity of movement for every pixel in the frame. We apply this method to the analysis of cell movement during different stages of the Dictyostelium developmental cycle. We analysed time-lapse video recordings of cell movement in single cells, mounds and slugs. The program can correctly assess the speed and direction of movement of either unlabelled or labelled cells in a time series of video images depending on the illumination conditions. Our analysis of cell movement during multicellular development shows that the entire morphogenesis of Dictyostelium is characterized by rotational cell movement. The analysis of cell and tissue movement by the velocity field method should be applicable to the analysis of morphogenetic processes in other systems such as gastrulation and neurulation in vertebrate embryos.
29
Schwartz, Andrew B., and Daniel W. Moran. "Motor Cortical Activity During Drawing Movements: Population Representation During Lemniscate Tracing." Journal of Neurophysiology 82, no. 5 (November 1, 1999): 2705–18. http://dx.doi.org/10.1152/jn.1999.82.5.2705.
Повний текст джерелаАнотація:
Activity was recorded extracellularly from single cells in motor and premotor cortex as monkeys traced figure-eights on a touch-sensitive computer monitor using the index finger. Each unit was recorded individually, and the responses collected from four hemispheres (3 primary motor and 1 dorsal premotor) were analyzed as a population. Population vectors constructed from this activity accurately and isomorphically represented the shape of the drawn figures showing that they represent the spatial aspect of the task well. These observations were extended by examining the temporal relation between this neural representation and finger displacement. Movements generated during this task were made in four kinematic segments. This segmentation was clearly evident in a time series of population vectors. In addition, the [Formula: see text] power law described for human drawing was also evident in the neural correlate of the monkey hand trajectory. Movement direction and speed changed continuously during the task. Within each segment, speed and direction changed reciprocally. The prediction interval between the population vector and movement direction increased in the middle of the segments where curvature was high, but decreased in straight portions at the beginning and end of each segment. In contrast to direction, prediction intervals between the movement speed and population vector length were near-constant with only a modest modulation in each segment. Population vectors predicted direction (vector angle) and speed (vector length) throughout the drawing task. Joint angular velocity and arm muscle EMG were well correlated to hand direction, suggesting that kinematic and kinetic parameters are correlated in these tasks.
30
Yang, Li Li. "Calculation of Optimized Movement Trajectories for the Human Forearm." Applied Mechanics and Materials 401-403 (September 2013): 1347–52. http://dx.doi.org/10.4028/www.scientific.net/amm.401-403.1347.
Повний текст джерелаАнотація:
Using the minimum variance model, optimal human forearm trajectories formation was investigated using a discrete time linear quadratic regulator. First, the continuous dynamics of the human forearm were established on the basis of the relation between muscle torque and neural control signal, and then we transferred the continuous system dynamics to discrete time notation. Finally we expressed the objective function of minimum variance model using a discrete time linear quadratic regulator and employed Riccati recursion to obtain the optimal movement trajectories of the human forearm. The results of example simulation show that the optimal movement trajectory of the forearm follows a smooth curve, and the speed curve of the hand is single peaked and bell shaped. These are in good agreement with the inherent kinematic properties of optimal movement, and therefore the method is effective for calculating the optimal movement trajectory of the human forearm.
31
Trinczek, B., A. Ebneth, E. M. Mandelkow, and E. Mandelkow. "Tau regulates the attachment/detachment but not the speed of motors in microtubule-dependent transport of single vesicles and organelles." Journal of Cell Science 112, no. 14 (July 15, 1999): 2355–67. http://dx.doi.org/10.1242/jcs.112.14.2355.
Повний текст джерелаАнотація:
We have performed a real time analysis of fluorescence-tagged vesicle and mitochondria movement in living CHO cells transfected with microtubule-associated protein tau or its microtubule-binding domain. tau does not alter the speed of moving vesicles, but it affects the frequencies of attachment and detachment to the microtubule tracks. Thus, tau decreases the run lengths both for plus-end and minus-end directed motion to an equal extent. Reversals from minus-end to plus-end directed movement of single vesicles are strongly reduced by tau, but reversals in the opposite direction (plus to minus) are not. Analogous effects are observed with the transport of mitochondria and even with that of vimentin intermediate filaments. The net effect is a directional bias in the minus-end direction of microtubules which leads to the retraction of mitochondria or vimentin IFs towards the cell center. The data suggest that tau can control intracellular trafficking by affecting the attachment and detachment cycle of the motors, in particular by reducing the attachment of kinesin to microtubules, whereas the movement itself is unaffected.
32
Gribble, Paul L., Lucy I. Mullin, Nicholas Cothros, and Andrew Mattar. "Role of Cocontraction in Arm Movement Accuracy." Journal of Neurophysiology 89, no. 5 (May 1, 2003): 2396–405. http://dx.doi.org/10.1152/jn.01020.2002.
Повний текст джерелаАнотація:
Cocontraction (the simultaneous activation of antagonist muscles around a joint) provides the nervous system with a way to adapt the mechanical properties of the limb to changing task requirements—both in statics and during movement. However, relatively little is known about the conditions under which the motor system modulates limb impedance through cocontraction. The goal of this study was to test for a possible relationship between cocontraction and movement accuracy in multi-joint limb movements. The electromyographic activity of seven single- and double-joint shoulder and elbow muscles was recorded using surface electrodes while subjects performed a pointing task in a horizontal plane to targets that varied randomly in size. Movement speed was controlled by providing subjects with feedback on a trial-to-trial basis. Measures of cocontraction were estimated both during movement and during a 200-ms window immediately following movement end. We observed an inverse relationship between target size and cocontraction: as target size was reduced, cocontraction activity increased. In addition, trajectory variability decreased and endpoint accuracy improved. This suggests that, although energetically expensive, cocontraction may be a strategy used by the motor system to facilitate multi-joint arm movement accuracy. We also observed a general trend for cocontraction levels to decrease over time, supporting the idea that cocontraction and associated limb stiffness are reduced over the course of practice.
33
Gulde, Philipp, Joachim Hermsdörfer, and Peter Rieckmann. "Speed but Not Smoothness of Gait Reacts to Rehabilitation in Multiple Sclerosis." Multiple Sclerosis International 2021 (June 3, 2021): 1–8. http://dx.doi.org/10.1155/2021/5589562.
Повний текст джерелаАнотація:
Introduction. Improved gait is one of the leading therapy goals in multiple sclerosis. A plethora of clinical timed trials and state-of-the-art technology-based approaches are available to assess gait performance. Objectives. To examine what aspects of gait react to inpatient rehabilitation in MS and which parameters should be best assessed. Design. In this longitudinal study, we examined the performance of 76 patients with MS to shed further light on factors influencing gait, associations between tests, and the reaction to inpatient rehabilitation during an average time span of 16 d. Setting. Private specialist clinic for inpatient neurorehabilitation. Main Outcome Measures. Clinical walk tests (timed 25-foot walk test at normal pace, maximum pace over 10 m or 6 min) and IMU-based measures of movement smoothness. Results. All gait parameters were strongly intercorrelated (all p < 0.05 ), and a model multiple linear regression for the 6MWT revealed short distance velocity (10 m) and movement smoothness as predictors in a strong model ( R 2 adjusted 0.75, p < 0.01 ). A second model with natural pace on short distance and movement smoothness was almost equally strong ( R 2 adjusted 0.71, p < 0.01 ). Patients improved their walking speed ( p < 0.01 ), but not smoothness ( p = 0.08 – 0.12 ), over the course of rehabilitation. Conclusions. Since we were not able to observe improvements in smoothness of gait, we conclude that rehabilitation programs should be adapted to the patient’s physiological capacities in order to allow for such improvements in smoothness of gait. Externally valid gait capacity (6MWT) could be predicted by a single walk for 10 s at natural pace.
34
Liao, Yi, Jeremy W. Schroeder, Burke Gao, Lyle A. Simmons, and Julie S. Biteen. "Single-molecule motions and interactions in live cells reveal target search dynamics in mismatch repair." Proceedings of the National Academy of Sciences 112, no. 50 (November 2, 2015): E6898—E6906. http://dx.doi.org/10.1073/pnas.1507386112.
Повний текст джерелаАнотація:
MutS is responsible for initiating the correction of DNA replication errors. To understand how MutS searches for and identifies rare base-pair mismatches, we characterized the dynamic movement of MutS and the replisome in real time using superresolution microscopy and single-molecule tracking in living cells. We report that MutS dynamics are heterogeneous in cells, with one MutS population exploring the nucleoid rapidly, while another MutS population moves to and transiently dwells at the replisome region, even in the absence of appreciable mismatch formation. Analysis of MutS motion shows that the speed of MutS is correlated with its separation distance from the replisome and that MutS motion slows when it enters the replisome region. We also show that mismatch detection increases MutS speed, supporting the model for MutS sliding clamp formation after mismatch recognition. Using variants of MutS and the replication processivity clamp to impair mismatch repair, we find that MutS dynamically moves to and from the replisome before mismatch binding to scan for errors. Furthermore, a block to DNA synthesis shows that MutS is only capable of binding mismatches near the replisome. It is well-established that MutS engages in an ATPase cycle, which is necessary for signaling downstream events. We show that a variant of MutS with a nucleotide binding defect is no longer capable of dynamic movement to and from the replisome, showing that proper nucleotide binding is critical for MutS to localize to the replisome in vivo. Our results provide mechanistic insight into the trafficking and movement of MutS in live cells as it searches for mismatches.
35
Pohl, Patricia S., and Carolee J. Winstein. "Age-Related Effects on Temporal Strategies to Speed Motor Performance." Journal of Aging and Physical Activity 6, no. 1 (January 1998): 45–61. http://dx.doi.org/10.1123/japa.6.1.45.
Повний текст джерелаАнотація:
The purpose of ihis study was to compare the effects of a single practice session on performance strategies used by young and older adults to decrease movement time (MT) while maintaining accuracy of an aiming task. Five young and 5 older adult males practiced until each accumulated 500 target hits in each of two complexity conditions as defined by Fitts’s law. Participants decreased MT with practice; however, older adults had longer MTs than the young, particularly in the high-complexity condition. With practice in the low-complexity condition, participants decreased absolute acceleration and deceleration times but maintained the relative amount of MT devoted to temporal phases. In contrast, with practice in the high-complexity condition, participants decreased absolute deceleration and dwell time and changed the temporal structure. Results suggest that older adults can decrease MT with practice and that the performance strategies adopted to speed performance are more a function of task complexity than age.
36
Ferguson-Stegall, Lisa, Mandy Vang, Anthony S. Wolfe, and Kathy M. Thomsen. "A 9-Week Jaques-Dalcroze Eurhythmics Intervention Improves Single and Dual-Task Gait Speed in Community-Dwelling Older People." Journal of Physical Activity and Health 14, no. 9 (September 2017): 740–44. http://dx.doi.org/10.1123/jpah.2017-0416.
Повний текст джерелаАнотація:
Background:Falls are a major public health concern among older adults, and most occur while walking, especially under dualtask conditions. Jaques-Dalcroze eurhythmics (JDE) is a music-based movement training program that emphasizes multitask coordinated movement. A previous 6-mo JDE study in older people demonstrated improved gait and balance; however, the effects of short-term JDE interventions on fall risk-related outcomes are largely unknown. We conducted a preliminary investigation on whether a 9-week JDE intervention improved gait and stability in a community-dwelling older cohort, hypothesizing that improvements would occur in all outcome measures.Methods:Nine participants (78.9 ± 12.3 y) completed the supervised JDE intervention (once/week for 60 min). Gait speed was determined by the 6-m timed walk test (6MTW); dual-task gait speed was determined by another 6MTW while counting backward from 50 aloud; and coordinated stability was assessed using a Swaymeter-like device.Results:Gait speed (0.92 ± 0.11 vs 1.04 ± 0.12 m/sec, P = .04) and dual-task gait speed (0.77 ± 0.09 vs 0.92 ± 0.11 m/sec, P = .0005) significantly improved.Conclusions:This novel intervention is an effective short-term physical activity option for those that plan physical activity or fall-risk reduction programs for the older people.
37
Barylski, Adam, and Norbert Piotrowski. "Analysis of Abrasive Particle Trajectories during Single-Sided Lapping Process with Driven Conditioning Ring." Applied Mechanics and Materials 838 (June 2016): 3–9. http://dx.doi.org/10.4028/www.scientific.net/amm.838.3.
Повний текст джерелаАнотація:
In this paper new kinematics systems were studied for a single lapping process. In order to ensure the constant profile wear of the tool a standard kinematic system can be changed. Lapping is carried out by applying loose abrasive grains between two surfaces and causes a relative motion between them. The result is a finish of multi-directional lay. During process, the mechanism of surface formation are decisively affected by a pressure force, a process time and a motion type of grains. It has been proven, that providing the additional movements of the conditioning ring affects the profile wear of the lapping plate. First of all, the kinematics equations of the lapping process have been developed and the process has been simulated. A type of the abrasive particle trajectories in standard single-disk lapping depends on rotational speed ratio of a tool and a conditioning ring. In addition, two new kinematic systems were presented: with radial and secant movement of the conditioning ring. Finally, comparison and analysis of abrasive trajectories were carried out.
38
Naumenko, Stanislav, and Mikhail Kulikov. "Methodology of speed qualities development of police officers for actions in extreme situations of operational activities." Vestnik of the St. Petersburg University of the Ministry of Internal Affairs of Russia 2021, no. 4 (December 20, 2021): 215–21. http://dx.doi.org/10.35750/2071-8284-2021-4-215-221.
Повний текст джерелаАнотація:
The article considers the scientific foundations of the pedagogical approach to the study and development of speed qualities, in particular, the reaction speed and functional capacities of a person who provides professional training of police officers and athletes. During the research, the features of the speed qualities development, in particular the speed of reaction, were studied by means of physical training, with the help of which it is possible to achieve maximum speed of response, and, on this basis, to form stable skills for counteraction in emergency situations related to service-applied activities. A set of factors determining the speed of response to an external signal is considered. Methods for the growth of speed in the training process serve as the basis for the progress of this quality in relation to the operational and service activities of police officers. The article presents the most effective methods of speed development, aimed both at improving this physical quality, and contributing to the formation of the necessary motor skills for the successful fulfillment of operational-service tasks and for competing.
Speed qualities are complex in their structure, including the time of the motor reaction, the speed of a single movement, the frequency of movements, etc. These complexity and diversity should be taken into account during the training of high-speed abilities of police officers for actions in extreme situations of operational and service activities, and a special emphasis on the acquisition and development of new motor skills and abilities should be made.
39
Sokolenko, Tetiana, and Anatoliy Palchyk. "The emergence of free intervals in the traffic flow depending on the intensity of movement and speed." Automobile Roads and Road Construction, no. 109 (2021): 184–90. http://dx.doi.org/10.33744/0365-8171-2021-109-184-190.
Повний текст джерелаАнотація:
The movement of single and group cars in traffic flows was investigated during the work. These studies are used to calculate the vehicle delay time during maneuvers through crossings and adjacencies at the same level. On the basis of the data obtained, the technical and economic discussion of the cross-sectional or adjoining parameters under consideration can be made. In the course of the study, examination will be conducted on the influence of intensity, velocity and traffic flow on the distribution intervals between cars and a graph of this effect for different traffic intensities is to be constructed. On the basis of the provided charts, the dependence of the free interval, necessary for maneuvering, on the traffic flow intensity is described. Using this dependence, you can figure out the number of cars that can be transported continuously. Knowing the traffic flow, its intensity and the distribution of free intervals between cars and groups of vehicles, the lag time of cars that are waiting for the ability to maneuver as well as their quantity can be calculated with the help of the proposed method.
40
Volina, Tatiana, Serhii Pylypaka, Victor Nesvidomin, Aleksandr Pavlov, and Svitlana Dranovska. "The possibility to apply the Frenet trihedron and formulas for the complex movement of a point on a plane with the predefined plane displacement." Eastern-European Journal of Enterprise Technologies 3, no. 7 (111) (June 30, 2021): 45–50. http://dx.doi.org/10.15587/1729-4061.2021.232446.
Повний текст джерелаАнотація:
Material particles interact with the working moving surfaces of machines in various technological processes. Mechanics considers a technique to describe the movement of a point and decompose the speed and acceleration into single unit vectors of the accompanying trajectory trihedron for simple movement. The shape of the spatial curve uniquely sets the movement of the accompanying Frenet trihedral as a solid body. This paper has considered the relative movement of a material particle in the static plane of the accompanying Frenet trihedron, which moves along a flat curve with variable curvature. Frenet formulas were used to build a system of differential equations of relative particle movement. In contrast to the conventional approach, the chosen independent variable was not the time but the length of the arc of the guide curve along which the trihedron moves. The system of equations has been built in the projections onto the unit vectors of the moving trihedron; it has been solved by numerical methods. The use of the accompanying curve trihedron as a moving coordinate system makes it possible to solve the problems of the complex movement of a point. The shape of the curve guide assigned by parametric equations in its length function determines the portable movement of the trihedron and makes it possible to use Frenet formulas to describe the relative movement of a point in the trihedron system. This approach enables setting the portable movement of the trihedron osculating plane along a curve with variable curvature, thereby revealing additional possibilities for solving problems on a complex movement of a point at which rotational motion around a fixed axis is a partial case. The proposed approach has been considered using an example of the relative movement of cargo in the body of a truck moving along the road with a curvilinear axis of variable curvature. The charts of the relative trajectory of cargo slip and the relative speed for the predefined speed of the truck have been constructed
41
Chen, L., B. Wu, and Y. Zhao. "A REAL-TIME PHOTOGRAMMETRIC SYSTEM FOR MONITORING HUMAN MOVEMENT DYNAMICS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B2-2020 (August 12, 2020): 561–66. http://dx.doi.org/10.5194/isprs-archives-xliii-b2-2020-561-2020.
Повний текст джерелаАнотація:
Abstract. The human body posture is rich with dynamic information that can be captured by algorithms, and many applications rely on this type of data (e.g., action recognition, people re-identification, human-computer interaction, industrial robotics). The recent development of smart cameras and affordable red-green-blue-depth (RGB-D) sensors has enabled cost-efficient estimation and tracking of human body posture. However, the reliability of single sensors is often insufficient due to occlusion problems, field-of-view limitations, and the limited measurement distances of the RGB-depth sensors. Furthermore, a large-scale real-time response is often required in certain applications, such as physical rehabilitation, where human actions must be detected and monitored over time, or in industries where human motion is monitored to maintain predictable movement flow in a shared workspace. Large-scale markerless motion-capture systems have therefore received extensive research attention in recent years.In this paper, we propose a real-time photogrammetric system that incorporates multithreading and a graphic process unit (GPU)-accelerated solution for extracting 3D human body dynamics in real-time. The system includes a stereo camera with preliminary calibration, from which left-view and right-view frames are loaded. Then, a dense image-matching algorithm is married with GPU acceleration to generate a real-time disparity map, which is further extended to a 3D map array obtained by photogrammetric processing based on the camera orientation parameters. The 3D body features are acquired from 2D body skeletons extracted from regional multi-person pose estimation (RMPE) and the corresponding 3D coordinates of each joint in the 3D map array. These 3D body features are then extracted and visualised in real-time by multithreading, from which human movement dynamics (e.g., moving speed, knee pressure angle) are derived. The results reveal that the process rate (pose frame-rate) can be 20 fps (frames per second) or above in our experiments (using two NVIDIA 2080Ti and two 12-core CPUs) depending on the GPU exploited by the detector, and the monitoring distance can reach 15 m with a geometric accuracy better than 1% of the distance.This real-time photogrammetric system is an effective real-time solution to monitor 3D human body dynamics. It uses low-cost RGB stereo cameras controlled by consumer GPU-enabled computers, and no other specialised hardware is required. This system has great potential for applications such as motion tracking, 3D body information extraction and human dynamics monitoring.
42
Rind, F. C., and P. J. Simmons. "Orthopteran DCMD neuron: a reevaluation of responses to moving objects. I. Selective responses to approaching objects." Journal of Neurophysiology 68, no. 5 (November 1, 1992): 1654–66. http://dx.doi.org/10.1152/jn.1992.68.5.1654.
Повний текст джерелаАнотація:
1. The "descending contralateral movement detector" (DCMD) neuron in the locust has been challenged with a variety of moving stimuli, including scenes from a film (Star Wars), moving disks, and images generated by computer. The neuron responds well to any rapid movement. For a dark object moving along a straight path at a uniform velocity, the DCMD gives the strongest response when the object travels directly toward the eye, and the weakest when the object travels away from the eye. Instead of expressing selectivity for movements of small rather than large objects, the DCMD responds preferentially to approaching objects. 2. The neuron shows a clear selectivity for approach over recession for a variety of sizes and velocities of movement both of real objects and in simulated movements. When a disk that subtends > or = 5 degrees at the eye approaches the eye, there are two peaks in spike rate: one immediately after the start of movement; and a second that builds up during the approach. When a disk recedes from the eye, there is a single peak in response as the movement starts. There is a good correlation between spike rate and angular acceleration of the edges of the image over the eye. 3. When an object approaches from a distance sufficient for it to subtend less than one interommatidial angle at the start of its approach, there is a single peak in response. The DCMD tracks the approach, and, if the object moves at 1 m/s or faster, the spike rate increases throughout the duration of object movement. The size of the response depends on the speed of approach. 4. It is unlikely that the DCMD encodes the time to collision accurately, because the response depends on the size as well as the velocity of an approaching object. 5. Wide-field movements suppress the response to an approaching object. The suppression varies with the temporal frequency of the background pattern. 6. Over a wide range of contrasts of object against background, the DCMD gives a stronger response to approaching than to receding objects. For low contrasts, the selectivity is greater for objects that are darker than the background than for objects that are lighter.
43
Voevodskii, Constantine E., and Vladimir M. Strepetov. "Longitudinal vibrations in electrodynamics suspension system." Transportation systems and technology 2, no. 1 (December 15, 2016): 52–64. http://dx.doi.org/10.17816/transsyst20162152-64.
Повний текст джерелаАнотація:
A system of electrodynamics suspension (EDS) in which the primary source of the field (electromagnet) is moving in a straight line parallel to the surface of the track and his speed makes small oscillations around a mean value is considered. The approximation of an infinitely wide track is allowed, the primary source of the electromagnetic field acts as a so-called periodic source. This problem is a special case of the general problem of the rate of the transients in the EDS, caused by uneven movement. Named speed determines the amount of time constants that make sense, and in contrast to the simplest case of a one-dimensional linear oscillator system EDS characterizes not by a single time constant, but by infinite set of values. The method of calculation of levitation and braking forces acting in this oscillatory motion on carriage electromagnet is worked out and simple explicit formulas to calculate these forces are got. On the basis of the calculation of time constants the rate of the transients in the EDS, caused by uneven movement is assessed. The calculations of levitation and braking forces according to the developed technique are made. The results obtained allow to delimit the applicability of the so-called quasi-static approach which consists in that the irregularly moving of electromagnet replaced by concurrent, i.e., the same electromagnet, similarly disposed and uniformly moving with a speed coinciding with the instantaneous value of the actual longitudinal speed of the electromagnet. In the quasi-static approximation, fluctuations of levitation and braking forces are in phase with oscillations of speed and amplitude of the forces oscillations do not depends on the frequency of the speed oscillation. The calculations show that in reality there is phase shift between the forces oscillations and speed oscillations depending on the frequency. Amplitudes of levitation and braking forces oscillations also depend on the oscillation frequency, and for each speed value a resonance frequency exists at which they reach the maximum value.
44
Kawazoe, Yoshihiko. "NANBA Walking Robot (JIZAI Movement of Physical Body Using State Transition with Instability)." Journal of Robotics and Mechatronics 26, no. 6 (December 20, 2014): 673–84. http://dx.doi.org/10.20965/jrm.2014.p0673.
Повний текст джерелаАнотація:
<div class=""abs_img""><img src=""[disp_template_path]/JRM/abst-image/00260006/01.jpg"" width=""300"" />Nanba turn</div> The effectiveness of transmitting force by using undulation is well known, but it takes time for the whip to flex and then sequentially transmit force. An example of using undulation is a whip whose tip movement exceeds the speed of sound. The whip-like motion principle requires that the user firmly plant the feet on the ground – a position that may lead to physical damage. Experts note that the load on different parts of the body is lowered by using the entire body appropriately. Using the term “nanba” symbolically to indicate body movement that does not use twisting, undulation, or the firm planting of the feet and that exerts minimal load on the joints, we investigatemovement of a bipedal robot based on state transitions that utilize instability. Speed and robustness result when a state (posture) is created instantaneously so that no blockage by the body occurs and transitions from state to state are made in a single step. </span>
45
Alomari, Saleh Ali, Mowafaq Salem Alzboon, Mohammad Subhi Al-Batah, and Belal Zaqaibeh. "A novel adaptive schema to facilitates playback switching technique for video delivery in dense LTE cellular heterogeneous network environments." International Journal of Electrical and Computer Engineering (IJECE) 10, no. 5 (October 1, 2020): 5347. http://dx.doi.org/10.11591/ijece.v10i5.pp5347-5367.
Повний текст джерелаАнотація:
The services of the Video on Demand (VoD) are currently based on the developments of the technology of the digital video and the network’s high speed. The files of the video are retrieved from many viewers according to the permission, which is given by VoD services. The remote VoD servers conduct this access. A server permits the user to choose videos anywhere/anytime in order to enjoy a unified control of the video playback. In this paper, a novel adaptive method is produced in order to deliver various facilities of the VoD to all mobile nodes that are moving within several networks. This process is performed via mobility modules within the produced method since it applies a seamless playback technique for retrieving the facilities of the VoD through environments of heterogeneous networks. The main components comprise two servers, which are named as the GMF and the LMF. The performance of the simulation is tested for checking clients’ movements through different networks with different sizes and speeds, which are buffered in the storage. It is found to be proven from the results that the handoff latency has various types of rapidity. The method applies smooth connections and delivers various facilities of the VoD. Meantime, the mobile device transfers through different networks. This implies that the system transports video segments easily without encountering any notable effects.In the experimental analysis for the Slow movements mobile node handoff latency (8 Km/hour or 4 m/s) ,the mobile device’s speed reaches 4m/s, the delay time ranges from 1 to 1.2 seconds in the proposed system, while the MobiVoD system ranges from 1.1 to 1.5. In the proposed technique reaches 1.1026 seconds forming the required time of a mobile device that is switching from a single network to its adjacent one. while the handoff termination average in the MobiVoD reaches 1.3098 seconds. Medium movement mobile node handoff latency (21 Km/ hour or 8 m/s) The average handoff time for the proposed system reaches 1.1057 seconds where this implies that this technique can seamlessly provide several segments of a video segments regardless of any encountered problems. while the average handoff time for the MobiVoD reaches 1.53006623 seconds. Furthermore, Fast movement mobile node handoff latency (390 Km/ hour or 20 m/s). The average time latency of the proposed technique reaches 1.0964 seconds, while the MobiVoD System reaches to 1.668225 seconds.
46
Ling, Tong, Kevin C. Boyle, Valentina Zuckerman, Thomas Flores, Charu Ramakrishnan, Karl Deisseroth, and Daniel Palanker. "High-speed interferometric imaging reveals dynamics of neuronal deformation during the action potential." Proceedings of the National Academy of Sciences 117, no. 19 (April 27, 2020): 10278–85. http://dx.doi.org/10.1073/pnas.1920039117.
Повний текст джерелаАнотація:
Neurons undergo nanometer-scale deformations during action potentials, and the underlying mechanism has been actively debated for decades. Previous observations were limited to a single spot or the cell boundary, while movement across the entire neuron during the action potential remained unclear. Here we report full-field imaging of cellular deformations accompanying the action potential in mammalian neuron somas (−1.8 to 1.4 nm) and neurites (−0.7 to 0.9 nm), using high-speed quantitative phase imaging with a temporal resolution of 0.1 ms and an optical path length sensitivity of <4 pm per pixel. The spike-triggered average, synchronized to electrical recording, demonstrates that the time course of the optical phase changes closely matches the dynamics of the electrical signal. Utilizing the spatial and temporal correlations of the phase signals across the cell, we enhance the detection and segmentation of spiking cells compared to the shot-noise–limited performance of single pixels. Using three-dimensional (3D) cellular morphology extracted via confocal microscopy, we demonstrate that the voltage-dependent changes in the membrane tension induced by ionic repulsion can explain the magnitude, time course, and spatial features of the phase imaging. Our full-field observations of the spike-induced deformations shed light upon the electromechanical coupling mechanism in electrogenic cells and open the door to noninvasive label-free imaging of neural signaling.
47
Fu, Jun, Yuan Tang, Wen Hua Yuan, Yi Ma, Wei Chen, and Guang Ming Li. "Research on the Angle of Swirl Chamber Diesel Engine with Dual Channel." Applied Mechanics and Materials 635-637 (September 2014): 598–602. http://dx.doi.org/10.4028/www.scientific.net/amm.635-637.598.
Повний текст джерелаАнотація:
Swirl chamber diesel engine’s insert piece of channel performance has a great influence on the swirl chamber indoor airflow movement condition. So based on the 175F series bell flat bottom type swirl chamber’s single connection channel improvement, the influence law of swirl chamber indoor air movement during the injection time by the double connection channel angle at the engine rated speed 2600r/min was studied. Simplified boundary conditions to establish its mathematical solution model for the swirl chamber, then the fluid simulation software was used to research the original scheme and double channel with angle of 50 ° and 30 °, 40 °, 60 ° schemes’ swirl chamber indoor air movement. Results show that the angle of 40 ° dual channel form, the loss of the throttle was reduced, and the swirl chamber air velocity increases obviously, the swirl chamber air velocity in injection time up to 125 m/s,which not only increased indoor vortexes energy but also contribute to oil and gas preferably blended, and near the nozzle the temperature lower 20 °C than the original machine, effectively reducing the nozzle heat load.
48
Sun, Pengyuan, Dingtong Yang, and Wen-Long Jin. "Eco-Driving Algorithm with a Moving Bottleneck on a Single-Lane Road." Transportation Research Record: Journal of the Transportation Research Board 2674, no. 12 (October 13, 2020): 493–504. http://dx.doi.org/10.1177/0361198120961381.
Повний текст джерелаАнотація:
Eco-driving strategies have been applied to smooth traffic flow and reduce greenhouse gas emissions along with air pollution. In this paper, we propose an eco-driving strategy to reduce traffic oscillation and smooth trajectories for connected vehicles following a moving bottleneck on a single-lane road. The eco-driving strategy, which leverages vehicle-to-vehicle (V2V) communications, designs advisory speed limits for each following vehicle through a control algorithm. The algorithm is based on the prediction of the following vehicle trajectories dictated by a moving bottleneck. The following vehicle trajectories are obtained by analytically solving the moving bottleneck problem in which the moving bottleneck speeds vary over time. In addition, the bounded acceleration rate is imposed in car-following behavior. The benefits of this strategy are demonstrated by applying it to four scenarios with different bottleneck movements. By simulating the scenarios with Newell’s car-following model with bounded acceleration and VT-Micro emission model, we find that both speed fluctuations and emissions are reduced with the algorithm in the scenarios in which the moving bottleneck has a constant speed, accelerates, decelerates and stops-and-goes. The results indicate that the proposed eco-driving algorithm can smooth traffic flow behind a moving bottleneck.
49
Schmidt, Robert, and Joshua D. Berke. "A Pause-then-Cancel model of stopping: evidence from basal ganglia neurophysiology." Philosophical Transactions of the Royal Society B: Biological Sciences 372, no. 1718 (February 27, 2017): 20160202. http://dx.doi.org/10.1098/rstb.2016.0202.
Повний текст джерелаАнотація:
Many studies have implicated the basal ganglia in the suppression of action impulses (‘stopping’). Here, we discuss recent neurophysiological evidence that distinct hypothesized processes involved in action preparation and cancellation can be mapped onto distinct basal ganglia cell types and pathways. We examine how movement-related activity in the striatum is related to a ‘Go’ process and how going may be modulated by brief epochs of beta oscillations. We then describe how, rather than a unitary ‘Stop’ process, there appear to be separate, complementary ‘Pause’ and ‘Cancel’ mechanisms. We discuss the implications of these stopping subprocesses for the interpretation of the stop-signal reaction time—in particular, some activity that seems too slow to causally contribute to stopping when assuming a single Stop processes may actually be fast enough under a Pause-then-Cancel model. Finally, we suggest that combining complementary neural mechanisms that emphasize speed or accuracy respectively may serve more generally to optimize speed–accuracy trade-offs. This article is part of the themed issue ‘Movement suppression: brain mechanisms for stopping and stillness’.
50
Wang, Xin, Bo Xu, and Z. Chen. "Numerical simulation of droplet dynamics on chemically heterogeneous surfaces by lattice Boltzmann method." International Journal of Numerical Methods for Heat & Fluid Flow 30, no. 2 (August 19, 2019): 607–24. http://dx.doi.org/10.1108/hff-03-2019-0259.
Повний текст джерелаАнотація:
Purpose This paper aims to investigate spontaneous movement of single droplet on chemically heterogeneous surfaces induced by the net surface tension, using the improved three-dimensional (3D) lattice Boltzmann (LB) method. Design/methodology/approach D3Q19 Shan-Chen LB model is improved in this paper. Segmented particle distribution functions coupled with the P-R equation of state are introduced to maintain the higher accuracy and greater stability. In addition, exact difference method (EDM) is adopted to implement force term to predict the droplet deformation and dynamics. Findings The numerical results demonstrate that spontaneous movement of single droplet (=1.8 µm) along wedge-shaped tracks is driven by net surface tension. Advancing angle decreases instantaneously with time, while receding angle changes slightly first and then decreases rapidly. Wetting length is affected by vertex angle and wetting difference, whereas the final value is only dependent on the stronger wettability. Although the velocity of single droplet on wedge-shaped tracks can be increased by the larger vertex angle, it has a negative influence on the displacement. For the same wetting difference, vertex angle equal to 30º is an optimization strategy in this model. If the simulation length is extended enough, then the smaller vertex angle is beneficial for the droplet movement. In addition, a larger wetting difference is beneficial to spontaneous movement, which can speed up the droplet movement. Originality/value The proposed numerical model of droplet dynamics on chemically heterogeneous surfaces provides fundamental insights for the enhancement of drop-wise condensation heat transfer.