Average Angular Velocity Research Articles

Left ventricular blood flow patterns in normal subjects: A quantitative analysis by three-dimensional magnetic resonance velocity mapping

Magnetic resonance velocity mapping was used to investigate the hypothesis of a vortex motion within the left ventricle interacting with mitral valve motion and inflow velocity. In vitro flow visualization studies have suggested the presence of a large anterior vortex inside the left ventricle during mitral inflow. However, to our knowledge the occurrence of this phenomenon has not been demonstrated in the human left ventricle. Magnetic resonance velocity mapping was performed in 26 healthy volunteers using a flow-adjusted gradient sequence for three-dimensional flow velocity acquisition in the long-axis plane of the left ventricle. By computer processing, the flow vectors in the left ventricle were visualized and animated dynamically. The early diastolic mitral inflow was apically directed, and a large counterclockwise anterior vortex was created within the left ventricle shortly after the onset of the mid-diastolic semiclosure of the anterior mitral leaflet. During mid-diastolic diastasis, mitral inflow ceased until the flow accelerated again at atrial systole. The final closure of the mitral valve was preceded by a smaller vortex seen at the tips of the mitral leaflets. At systolic ejection, all flow vectors were directed toward the left ventricular outflow tract. The anterior vortex had a radius of 1.62 +/- 0.24 cm (mean +/- SD), and the average angular velocity (i.e., the rotation of an element about the center of the vortex within the central core) was 30.08 +/- 9.98 radians/s. The maximal kinetic energy of the anterior vortex was 4.3 x 10(-4) +/- 7.1 x 10(-5) J. The hypothesis of a diastolic vortex formation in the human left ventricle was confirmed, and its close temporal relation to the motion of the anterior mitral leaflet was demonstrated.

Average angular velocity

This paper addresses the problem of the separation of rotational and internal motion. It introduces the concept of average angular velocity as the moment of inertia weighted average of particle angular velocities. It extends and elucidates the concept of Jellinek and Li of separation of the energy of overall rotation in an arbitrary (non-linear) N-particle system.

Net shoulder joint moment and muscular activity during light weight-handling at different displacements and frequencies.

The purpose of this study was to calculate net shoulder (gleno-humeral) joint moments from inverse dynamics and to measure muscular activity from six shoulder muscles (supraspinatus, infraspinatus, middle deltoid, anterior deltoid, trapezius, and pectoralis major) during light weight-handling at two different displacements (horizontal and vertical) and frequencies (40 and 60 cycles/min), to simulate an occupational cervicobrachial working task (light weight displacement). Ten normal adult male subjects were asked to move a known weight, representing 15% of the maximal lifted weight, in both horizontal and vertical conditions at frequencies of 40 cycles/min and 60 cycles/min. Raw EMG signals from six shoulder muscles were recorded and synchronized with the cinematographic data during three trials of 6 s each. The raw EMG signals of each muscle were full wave rectified and filtered at 3 Hz. The linear envelope (LE EMG) signals were normalized by time (% cycle) and by amplitude (% MVC), and for the analysis of variance, the normalized LE EMG signals were integrated (IN LE EMG). The average shoulder angular velocities, joint moments, and moment powers were computed from cinematographical data. No significant differences were observed between both tasks for the supraspinatus, infraspinatus, and pectoralis major IN LE EMG data as well as for integrated normalized shoulder joint moment for the whole cycle of movement. IN LE EMG data from middle deltoid, anterior deltoid, and trapezius muscles were significantly higher (p less than 0.05) when performing the vertical displacement task for the whole cycle of movement. This muscular activity difference between vertical and horizontal tasks indicated that the vertical displacement conditions induced higher muscular loads on the shoulder than the horizontal weight displacement conditions, although the vertical displacements were approximately 15% longer than the horizontal displacements. The non-significant difference of IN LE EMG between frequencies obtained for all muscles indicated that neither frequencies induced more muscular activity.

Prediction of Swirl Velocity of In-Cylinder Flow of an Engine by a Simplified Simulation Model. 2nd Report. Examination of the Simulation Model.

Predicitions of swirl velocity in an engine using the simplified simulation model were compared with the experimental data. The flow velocity was measured in a test engine by the laser doppler velocimeter under the motored condition. The predicted results of spatial distribution of the tangential flow velocity on a cylinder diameter and time history of the averaged angular velocity were compared with the experimental data. The flow patterns in the cylinder and the trends of angular velocity at the compression and expansion stroke are in good agreement with each other. It is confirmed that this simulation model is valid to predict the mean flow velocity in an engine. But this cannot predict the flow pattern at the intake or exhaust process at which the un-uniformity of flow exists.

Feedback control in ancient water and mechanical clocks

Attention is focused on Ktesibios' water clock and the outstanding mechanical clocks based on the crown wheel escapement that first appeared in Europe at the end of the thirteenth century. Specifially, block diagrams and the related equations are derived for both the Ktesibios and the verge and foliot clock. The essential role of feedback for controlling the speed of such devices is pointed out. In particular, each mechanical clock discussed can be regarded as a sampled-feedback control system. This explains why the average angular velocity of the wheel would be constant even in the absence of friction. The operation of the verge and foliot clock is compared to that of the pendulum clock built by Ch. Huygens in the seventeenth century.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Kinetic attraction during bimanual coordination.

Two experiments examined the effects of independent variations in kinetic and kinematic requirements on interlimb coupling during a bimanual task. The goal of the investigation was to provide preliminary evidence regarding one general class of physical variables that constrains discrete bimanual movements. Subjects attempted to execute a smooth unidirectional movement with the left arm, along with a three-segment reversal movement with the right arm. The first experiment manipulated the torque required to produce the reversal action, while movement duration and average angular velocity were held constant for both limbs. Several indications of increased interlimb coupling, due to the kinetic variation, were evident. The converse manipulation was used in the second experiment, with movement time and kinematics (velocity, acceleration) changed independently of joint torque requirements for the reversal limb. No clear effect of kinematics on coupling strength was noted. The results suggest that one variable influencing interlimb attraction toward common spatiotemporal trajectories may be kinetic in nature.

Ultrasound-induced yaw movements in the flying Australian field cricket (Teleogryllus oceanicus)

An ultrasonic stimulus induced negative phonotactic steering in the yaw axis of tethered, flying Australian field crickets. The forewings, hindwings and twisting of the thorax generated the forces which induced the yaw turn. However, abdominal ruddering did not contribute to yaw turns. Each aspect of the yaw steering response depended upon the stimulus intensity. At higher ultrasonic intensities, the magnitude and average angular velocity increased while the latency of the yaw turn decreased. Each of these factors varied in a graded manner, revealing that this behavior is more complex than a simple reflex.

The Influence of Velocity-Specific Resistance Training on the In Vivo Torque-Velocity Relationship and the Cross-Sectional Area of Quadriceps Femoris

This work was supported by Sport Canada end Hydra-Fitness Industries. In order to investigate the effects of velocity-specific resistance training, 30 healthy, male varsity athletes were assigned to either high (HVR) or low (LVR) velocity training or control (CG) groups. Subjects completed two 20-sec sets of maximal exercise at each of six hydraulic resistance stations for the lower limb. Resistances were adjusted as necessary to maintain consistent average angular velocities of approximately 1.05 and 3.14 rad/sec for the LVR and HVR groups, respectively. Subjects trained on alternate days for 6 weeks, completing either two (weeks 1 and 2) or three (weeks 3-6) circuits of the six stations each session. Peak knee extension torques were improved (p < 0.05) for the LVR group at all of seven angular velocities tested between 1.05 and 4.19 rad/sec. Improvements (p < 0.05) were also observed for the HVR group, but only at angular velocities of 2.62, 3.14, 3.66, and 4.19 rad/sec. Cross-sectional area of the quadriceps femoris muscle group obtained from serial computer tomography (CT) scans was increased (p < 0.05) for both training groups. No significant changes in either strength or cross-sectional area were observed for control subjects. These results indicate that while both of the training programs resulted in increased cross-sectional area of the knee extensors, the observed changes in strength performance are likely due to other factors which may be mediated by the different training velocities. J Orthop Sports Phys Ther 1989;10(11):456-462.

Biomechanical Characteristics of Jumping

Four track and field athletes were subjects in a study that analyzed seven jumping exercises and flop-style high jump takeoffs for ground reaction forces, knee angular kinematics, and electromyographic activities of knee extensor musculature. The ground contact times varied between 177 ±13 (flop) and 278 ±25 ms (standing five jumps). The peak ground contact forces were from 5002±130 N (special drop jump) to 8202±901 N (ranning five hops). Average knee angular velocities were highest in the eccentric phase of the flop takeoff (ω = 7.1 ± 2.1 rad × s-1). Electromyographic activities before the ground contact and during the eccentric phase of contact were highest in the flop-style high jump, while during the concentric phase of contact a special drop jump exercise showed the highest activity. Preactivity IEMG correlated with the eccentric IEMG, force, and knee angular velocity positively and with the contact time negatively (p<0.001), while eccentric IEMG correlated with the eccentric force and angular velocity positively and with the contact time negatively (p<0.001).

Biomechanical Characteristics of Jumping

Four track and field athletes were subjects in a study that analyzed seven jumping exercises and flop-style high jump takeoffs for ground reaction forces, knee angular kinematics, and electromyographic activities of knee extensor musculature. The ground contact times varied between 177 ±13 (flop) and 278 ±25 ms (standing five jumps). The peak ground contact forces were from 5002±130 N (special drop jump) to 8202±901 N (ranning five hops). Average knee angular velocities were highest in the eccentric phase of the flop takeoff (ω = 7.1 ± 2.1 rad × s-1). Electromyographic activities before the ground contact and during the eccentric phase of contact were highest in the flop-style high jump, while during the concentric phase of contact a special drop jump exercise showed the highest activity. Preactivity IEMG correlated with the eccentric IEMG, force, and knee angular velocity positively and with the contact time negatively (p<0.001), while eccentric IEMG correlated with the eccentric force and angular veloci...

1988 Volvo award in biomechanics. The triaxial coupling of torque generation of trunk muscles during isometric exertions and the effect of fatiguing isoinertial movements on the motor output and movement patterns.

Previous studies have shown that reduction of precise motor control accompanies local muscular fatigue. The effects of isodynamic fatiguing of flexion and extension trunk movements on the movement patterns and the motor output of the trunk were investigated. Twenty male subjects with no history of low-back pain for the past 6 months volunteered for the study. A triaxial dynamometer was used that simultaneously provided measurement of torque, angular position and velocity of each axis. Resistances were set independently for each axis by an interfaced computer. The subjects performed trunk flexion and extension movement against a sagittal plane resistance equal to 70% of their maximum isometric extension strength in the upright position. The minimum resistances in the coronal and transverse planes were set up at 7 Newton meters. The subjects were asked to perform trunk movement as quickly and as accurately as possible while exerting the maximum efforts until exhaustion. Analysis of variance, the MANOVA procedure with a repeated measure design, was performed among the selected parameters of the first, middle and last three repetition cycles. The selected parameters are the trunk motor output and movement patterns; the total angular excursion, range of motion, maximum and average torque and angular velocity of the trunk. All the selected parameters were significantly reduced in the sagittal plane. Subjects displayed significantly less motor control and greater range of motion in the coronal and transverse planes in performing the primary task of flexion and extension. The reduction in the functional capacity of the primary muscles performing the required task is compensated by secondary muscle groups and the spinal structure is loaded in a more injury prone pattern, as identified by finite element models. In addition it is suggested that the fatigued muscles would be less able to compensate any perturbation in the load or position of the trunk. The repetitive loading results in a weakening of the viscoelastic passive elements of the spineless structure. The loss of ability to protect these weakened passive elements makes the spine susceptible to industrial and recreational injuries.

The transient and steady states of the Bouasse-Sarda regulator

The transient and steady state regimes of the Bouasse-Sarda engine are studied by analytical and numerical methods. The series expansion of the average angular velocity, found by ireration, leads to a generalized expression of the Roseau formula. We have been able to establish the stability condition by using an improved solution of order zero of the vibrational amplitude of the mass connected to the spring. Numerical results and graphical representations are supplied.

On the nonlinear Born effect

In 1920 Max Born described the coupling of the intrinsic molecular spin to the hydrodynamic vorticity. At small shear rates molecules rotate at an angular velocity ⟨ω⟩ = ½∇ × u. In this paper we report the results of NEMD simulations which show that outside the linear regime, the average angular velocity ⟨ω⟩ is less than 1/2y.

Transient Mass Transfer at a Coated Rotating Disk Electrode: Diffusion and Electrohydrodynamical Impedances

The mass‐transfer response of a rotating disk electrode to a sine wave modulation of the angular velocity has been calculated for an interface covered by a porous layer of thickness , through which an ionic species is transported by molecular diffusion with a diffusivity . Electrohydrodynamical (EHD) impedances, defined as the transfer functions between the response of the concentration or concentration gradient at the interface and the modulated velocity, have been expressed as functions of a dimensionless frequency p, representing the ratio of the modulation frequency to the average angular velocity, of the permeability and of the diffusion time constant through the film . The frequency analysis of the impedance data for a coated electrode, therefore, allows one to determine and separately.

A numerical simulation of flow, heat and mass transfer in a floating zone at high rotational reynolds numbers

Laminar flow, heat and mass transfer in a cylindrical floating zone are computed for co-and counter-rotation of the feed rod and crystal in the absence of Marangoni and natural convection. A finite volume method using primitive variables is used to obtain numerical solutions over a wide range of governing parameters. For differential co-rotation at high Reynolds numbers, the velocity field exhibits a core region rotating with the average angular velocity of the rotating ends. For equal counter-rotation, the velocity field loses symmetry about the horizontal mid-plane at a critical rotational Reynolds number; beyond this, two assymetric solutions are to be found. Local and overall Nusselt numbers at the growing interface are computed to ascertain the heat transfer characteristics; the extent of radial solute segregation associated with each flow pattern is also examined.

Palaeomagnetic timing of the rotation and translation of Cyprus

The geological evolution of the Mesozoic Troodos Ophiolite Complex in Cyprus, and the tectonic nature and timing of the palaeomagnetically indicated anticlockwise rotation of Cyprus of some 80° and ca. 15° northward translation, have been open for debate for some time. New palaeomagnetic data from 18 sites (∼ 180samples) in the post-ophiolite sediments, ranging in age from Upper Cretaceous to Upper Miocene, are presented. Most of the sites are of normal geomagnetic polarity, but indications of reversed polarity have been found in an older group of sediments (the Lefkara Formation of Upper Palaeocene age). Six sites from the older group of sediments (Upper Cretaceous to Eocene in age) give a site mean direction of the AF cleaned sediments of ( D, I) = (323°, 29°) with α 95 = 18° , while 5 sites from a younger group of sediments (Oligocene to Miocene in age) give a cleaned site mean direction of ( D, I) = (334°, 58°) with α 95 = 9° . These and published data suggest that an anticlockwise rotation of Cyprus of ∼ 60 ± 10° occurred early during the post-igneous evolution of the Cyprus oceanic crust between ∼ 90 and ∼ 50Ma, leaving only a minor anticlockwise rotation of ∼ 20 ± 10° to occur during the last 50 Ma. It is furthermore concluded that the northward translation of Cyprus of ∼ 15° mostly took place during the last ∼ 30Ma. It thus appears that a fairly rapid rotation of the Cyprus microplate first took place in the Late Cretaceous and Early Tertiary time with an average angular velocity of ∼ 1–2°/Ma, during which the northward translation was minor or negligible. In the latter half of the Tertiary, the sense of movement appears to have radically changed, the northward translation now being dominant with an average velocity of ∼ 5–6cm/yr. This temporal evolution is found to be in good agreement with the Mesozoic and Tertiary movements of the African lithospheric plate relative to Europe, as evidenced from the Atlantic sea-floor magnetic anomaly spreading history.

Textures and c-axis orientations of deformed quartz crystals from porphyric dikes of the Alpine »Root Zone« (Western Alps)

Deformation textures and c-axis preferred orientations of quartz phenocrysts from porphyric dikes of the Alpine »Root Zone« have been formed under conditions of greenschist to low amphibolite facies. It is shown that the deformation textures as shear planes and kink bands, boudins, grain boundary sutures, subgrains, coarse and fine recrystallized grains, deformation lamellae and fractures are developed in a chronological sequence during first increasing and later decreasing temperatures. The c-axis orientations are chiefly influenced by kinking during the early stage of metamorphism and later by recrystallization but not by the initial orientations of the c-axes. The shape of crossed-girdles is related to the type of strain. At the beginning of polygonization during increasing temperatures basal-a glide as a dominant glide mechanism is replaced by prism-c glide and vice versa during decreasing temperatures. The average angular velocity of c-axes is 0.4‡ per 1 % flattening.

Flight performance and visual control of flight of the free-flying housefly ( musca domestical L.) III. Interactions between angular movement induced by wide- and smallfield stimuli

The flights of free-flying houseflies are analysed in different behavioural and environmental situations. The angular movements about the vertical body axis are characterized by a cascade of steplike changes of long axis orientation (‘turns’). Most of these turns are separated by periods of little or no rotation. Turns about the vertical axis are short (under 120 ms). They are performed at angular velocities of up to about 4000 deg s -1 . These characteristics are found (i) when a single fly cruises in a stationary environment; (ii) if the visual input is eliminated; (iii) if a textured surround (optomotor stimulus) is moved around the fly; (iv) during visually guided pursuit of small targets in stationary as well as in moving environments. Optomotor stimulation increases the number of turns in the direction of pattern motion relative to those against it. This leads to a correlation between the average angular velocity of the fly and the stimulus velocity. However, optomotor stimulation does not interfere with chasing and tracking. A model is proposed that qualitatively accounts for the observed behaviour in free flight of houseflies.

Specificity of leg power changes to velocities used in bicycle endurance training.

Increases in leg power production resulting from 8 wk of bicycle endurance training (30 min/day, 5 times/wk) were studied using an isokinetic dynamometer. In addition, biopsies of vastus lateralis were analyzed to characterize muscle ultrastructural changes. Performance increased on the dynamometer specifically near the estimated average knee angular velocity used during the bicycle training (200 degrees/s). Power measurements were made during the first 5 contractions (maximal power: Pmax) and last 5 contractions (final power: Pend) of 25 and 50 consecutive contractions (at 60 and 240 degrees/s, respectively). Pmax and Pend increased only at 240 degrees/s but not at 60 degrees/s. These increases in Pmax (86 W) and Pend (78 W) resulted primarily from longer torque maintenance but also from increased peak torque during each contraction and were close to the increase in mechanical power output maintained on the bicycle (Pb; 78 W) during the training sessions. The specificity of these changes to the angular velocities used in the bicycle training indicates a neural basis to these adaptations. We suggest that these neural adaptations, coupled with the observed enhancement of muscle mitochondrial and capillary density (+41 and +15%, respectively) underlie the increased ability to maintain power production on a bicycle after endurance training.

Forced Torsional Vibration of a Two Degrees of Freedom System with a Clearance : 2nd Report, Analytical Solution

An analytical solution of the forced tortional vibration of a two degrees of freedom system with a clearance between two rotating bodies is derived. The analytical solution is obtained by connecting the solutions for the motion of each body caused by successive collisions of the bodies, without making assumptions on the number of times of collisions that occur during a cycle of the forced motion and on the periodicity of the collisions. The analytical solution shows the existence of a phenomenon of multi-time collisions at one side of the clearance during a half cycle of the forced motion. Effects of the dimension of the clearance and the average angular velocity on the strength of the impact force are investigated. The results of the analytical solution show good quantitative agreements with those of the simulation.