Initial Vertical Position Research Articles

Predictive dynamical behavior of liquid-filled microparticles partitioning in the vicinity of a coronary bifurcation under pulsatile blood flow and arterial distensibility: A two-dimensional study

A promising advance of bioengineering consists in the development of micro-nanoparticles as drug delivery vehicles injected intravenously or intraarterialy for targeted treatment. Proficient functioning of drug carries is conditioned by a reliable prediction of pharmacokinetics in human as well as their dynamical behavior once injected in blood stream. In this study we aim to provide a reliable numerical prediction of dynamical behavior of microparticles in human left coronary artery focusing on their behavior in the vicinity of the coronary bifurcation. We investigate the velocity, the deformation and the trajectory of three microparticles upon pulsatile blood flow and arterial compliance with varying the capillary number and the initial vertical position. The study is carried out within physiological conditions to provide accurate results. Fluid–structure interaction is solved by the Arbitrary Lagrangian Eulerian method using the COMSOL Multiphysics software.

Impact of initial fiber states on different fiber dynamic patterns in the laminar channel flow

The dynamics of an elastic fiber with various initial states in a laminar channel flow is investigated using the immersed boundary-lattice Boltzmann method. Fiber-wall collisions are solved by adding a repulsive force in the model. Our simulation results demonstrate that the initial fiber state closely relates to the stability of the considered conveyance system. Different initial states may lead to different dynamic patterns in the downstream. The fiber is found to go straight forward along a horizontal path when it is horizontally and symmetrically placed at the channel centerline. Breaking this symmetry by varying the fiber's initial vertical position or orientation will induce the instability of the system, which then causes deviations and fluctuations in fiber's conveyance path. No matter how large the deviation occurs in the upstream, the fiber is always found to migrate to the channel central region in the downstream and would eventually settle in a vertical position slightly away from the channel centerline. Moreover, the off-centerline distance that a fiber settles depends on its dynamic pattern rather than a specific initial fiber state. For our system, there are two kinds of dynamic patterns observed in the downstream channel. In the first pattern, the fiber eventually reaches its equilibrium state and is observed to do a translational motion. In the second pattern, no equilibrium state is observable, and the fiber is found to do a periodically tumbling motion. The fiber's eventual conveyance speed depends on the vertical position it eventually settles and can be roughly approximated by the local flow velocity.

Particle migration induced by hydrodynamic interparticle interaction in the Poiseuille flow of a Giesekus fluid

Particle migration induced by hydrodynamic interparticle interaction in a Poiseuille flow of Giesekus viscoelastic fluid is studied numerically using the direct forcing/fictitious domain method with Weissenberg number 0.1 ≤ Wi ≤ 1.5, mobility parameter 0.1 ≤ α ≤ 0.7, viscosity ratio 0.1 ≤ β ≤ 0.7, block ratio 0.2 ≤ e ≤ 0.4, initial interparticle spacing 0.1 ≤ s ≤ 2.0, and initial vertical position 0.1 ≤ y0 ≤ 0.2. The method is validated by comparing the present results with previous numerical results. The effects of Wi, α, β, e, s and y0 on the particle migration are analyzed. The results showed that a particle tends to move toward the wall with the increases of the elastic effect of the fluid, shear thinning effect, solvent viscosity and block ratio. For three particles in initial parallel arrangement, the trajectory of two particles on the edge is obviously different from that of a single particle. A single particle would move toward the centerline at a definite y0. However, for the case of three particles at a same y0, the upstream particle first migrates a distance toward the wall and then return toward the centerline, while downstream particle migrates quickly to the centerline. This is called abnormal migration. The phenomenon of abnormal migration disappears when the initial interparticle spacing is large enough, and is more obvious when the initial vertical position of particles is close to the wall. The phenomenon of abnormal migration tends to be obvious with the increases of the shear thinning effect, solvent viscosity and the block ratio, but with the decrease of elastic effect of the fluid.

Aeroelastic interactions and trajectory selection of vortex gusts impinging upon Joukowski airfoils

The dynamically-coupled interactions of vortex gusts encountering a symmetric Joukowski airfoil on linear elastic supports is formulated analytically and evaluated numerically using a time-dependent conformal mapping. The Brown and Michael framework models the unsteady shedding of vorticity from the airfoil into the wake, and the aeroelastic motion of the airfoil is analyzed using quasi-steady, apparent mass, and fully-unsteady aerodynamic models. Special attention is paid to the influences of the strength of the incident vortex and the airfoil natural frequency on the initial upstream placement of a vortex gust that achieves direct impingement. These results are weakly sensitive to the initial vortex position in the limits of either large or small structural natural frequency, and the initial vertical vortex position to achieve impingement changes monotonically with the vortex strength. A comparison of the numerical model with available experimental vortex gust measurements over stationary airfoils highlights the appropriate use of the point-vortex model for inviscid vortex–airfoil interaction problems without significant vortex strength decay, which occurs for predominantly viscous interactions of close vortex–airfoil encounters.

Numerical simulation of static and dynamic stability of air-bubbles in highly flowable cement-based materials

A computational fluid dynamics (CFD) software and image analysis technique were used to simulate the flow performance and stability characteristics of air-void system (AVS) of fresh highly flowable cement-based materials as a three-phases gas-liquid-solid system using a coaxial cylinders tribometer set-up. The investigated characteristics consist of flow velocity, shear rate, and pressure magnitudes of the suspensions, as well as displacement, elongation, orientation angle, and rising velocity of the air bubbles in both parallel and perpendicular planes to flow directions. Static and dynamic shear modes as well as different shearing zones were evaluated. Different suspending fluids having different plastic viscosity and surface tension values varying between 5 and 30 Pa.s and 5 and 73 mN/m, respectively, were investigated. The suspensions consisted of spherical solid particles of 2.5, 4, and 5 mm diameter with 3.8 % volumetric content, as well as 18 and 150 air bubbles of 2- and 1-mm diameter, respectively, corresponding to 7 % volumetric content.According to the numerical results, the shearing mode and distance from the shearing source were shown to be the most dominant parameters affecting the flow performance and stability of air-void system in highly flowable cement-based materials, compared to the suspending fluid characteristics. Moreover, both the diameter and initial vertical positions of the air bubbles can significantly affect their stability characteristics.

Calibration of energy slits and simulation of electron trajectories in the alpha magnet’s 3D field

At the PBP-CMU Electron Linac Laboratory, high-brightness electron beams are produced from the radio-frequency (RF) linear accelerator (linac) system that consists of a thermionic RF electron gun, an alpha magnet, a traveling-wave linac structure, quadrupole magnets and steering coils. Several diagnostic devices are installed in the accelerator system to characterize electron beam properties. In this work, we study on measurement of electron beam energy downstream the RF gun using the alpha magnet equipped with energy slits in the vacuum chamber and a current transformer. Calibration of the energy slits’ posit ions for various stepper motor encoder numbers was conducted before installing the slits in the magnet’s vacuum chamber. The calibration result was imported into the energy calculation software that links to the stepper motor encoder and the energy value will then be automatically calculated. Moreover, dynamic simulations using a software ASTRA were performed to investigate electron’s trajectories in the alpha magnet’s field with different initial electron positions and angles. The results from this study will be used to estimate the result and accuracy of energy measurement using the alpha magnet. It was found that, for different initial horizontal and vertical positions at the alpha magnet entrance, the energy of electron will be measured to be lower than its actual energy by around 0.5% and the measured energy will decrease when the initial position is moving away from the middle point. In case of horizontal particle’s angle, the error of energy measurement increases up to 1% at the angle of 3° before the beam hitting the alpha magnet chamber. For the vertical particle’s angle, the electron that has the initial angle less than or larger than 1.5° will hit the vacuum chamber.

Clockwise Vortical-Gust/Airfoil Interactions at a Transitional Reynolds Number

This paper presents high-fidelity implicit large-eddy simulations (ILES) of parallel vortical gust interactions with a NACA0012 airfoil operating at a transitional chord-based Reynolds number of and an angle of attack of . The gust is supplied upstream of the airfoil as a Taylor vortex. Three different initial vertical positions are considered for a clockwise (CW)-oriented gust. ILES simulation of CW gust interactions is compared with inviscid simulations as well as prior counterclockwise (CCW) gust simulations. Contrary to the previous CCW gust interactions, the upper surface boundary-layer experiences an upstream excursion of laminar separation, transition, and turbulent reattachment that lingers behind the gust. This upstream shift manifests in a pitch-up moment coefficient that relaxes slowly to the pregust state. As in the previous CCW cases, the lower surface boundary layer is disrupted by the CW vortex producing a brief acoustic event. This effect is particularly severe when the CW gust passes just beneath the wing section. In this scenario, the lower surface instability coalesces into a boundary-layer vortex and briefly forms a dipole with the CW gust.

Changes in Hyolaryngeal Movement During Swallowing in the Lateral Decubitus Posture.

ObjectiveTo investigate the differences in hyolaryngeal kinematics at rest and during swallowing in the upright sitting (UP) and the lateral decubitus (LD) postures in healthy adults, and delineating any potential advantages of swallowing while in the LD posture.MethodsSwallowing was videofluoroscopically evaluated in 20 healthy volunteers in UP and LD postures, based on the movements of hyoid bone, vocal folds, and the bolus head. Parameters included the Penetration-Aspiration Scale (PAS), horizontal and vertical displacement, horizontal and vertical initial position, horizontal and vertical peak position, time to peak position of the hyoid bone and vocal folds, and pharyngeal transit time (PTT).ResultsNine participants were rated PAS 2 in the UP and 1 was rated PAS 2 in the LD (p=0.003) at least 1 out of 3 swallows each posture. The hyoid and vocal folds showed more anterior and superior peak and initial positions in the LD. In addition, swallowing resulted in greater vertical and smaller horizontal displacement of the hyoid in LD posture compared with UP. Time to peak position of the hyoid was shorter in LD. The maximal vertical and horizontal displacement of the vocal folds, and PTT were comparable between postures.ConclusionThe results showed that the peak and initial positions of the hyoid and larynx and the pattern of hyoid movement varied significantly depending on the body postures. This study suggests that the LD posture was one of the safe feeding postures without any increased risk compared with UP posture.

Counterclockwise Vortical-Gust/Airfoil Interactions at a Transitional Reynolds Number

This paper presents high-fidelity implicit large-eddy simulations of parallel vortical-gust interactions with a NACA0012 airfoil operating at a transitional Reynolds number of and an angle of attack of . The gust is supplied upstream of the airfoil as a counterclockwise-oriented Taylor vortex. Upon impact with the leading edge, the gust splits, causing disruptions to the boundary layer on both surfaces of the airfoil. On the upper surface, the vortical gust causes an eruption of the laminar-separation bubble into a poorly formed turbulent leading-edge vortex that becomes more coherent as it overtakes and envelopes two-dimensional instability waves downstream. The gust and leading-edge vortex propagate as a dipole and induce a pressure disturbance upon departure from the trailing edge, an event significant enough to influence the lift. Beneath the airfoil, the lower section of the gust thickens the boundary layer and causes breakup into a series of spanwise coherent vortices. Both leading-edge vortex formation and lower boundary-layer disruption produce notable acoustic radiation. Three different initial vertical positions are considered for a counterclockwise-oriented gust. Gust position affects boundary-layer disruption such that higher encounters elicit a more coherent leading-edge vortex and lower encounters exhibit stronger lower-surface instabilities. All cases exhibit significant acoustic radiation emanating from the aforementioned flow transition events.

Robustness and Applicability of a Model-Based Tire State Estimator for an Intelligent Tire

ABSTRACT Tire states can be estimated by measuring the tire contact patch shape as it varies with vertical load, longitudinal and lateral slip, and so on. In this study, a miniature triaxial accelerometer is used to measure the centripetal accelerations at the tire inner liner. A tire state estimator (TSE) algorithm is developed to transform the measured accelerations to actual tire states, in this case vertical load. The approach used for the TSE is the extended Kalman filter (EKF), but an additional peak detection algorithm is used to synchronize the simulation model with the measurement signal before applying the EKF. The simulation model used in the EKF is an empirical model that describes the basic shape of the centripetal acceleration signal. The applicability of the estimator is assessed by considering the accuracy and robustness for several tire operating conditions: vertical load, velocity, inflation pressure, sideslip, camber, and braking. It is concluded that the TSE exhibits accurate vertical load estimation even in cases of varying load and velocity. Further, it is concluded that the vertical load estimation is robust for (pure) camber changes and (pure) longitudinal force disturbances. For relatively high lateral forces as result of sideslip, the estimation error is larger. The current estimator appears to be not robust for inflation pressure changes, but this can be solved by adding an inflation pressure sensor. Similarly, extension of the estimator to estimate lateral force by adding a second accelerometer not only provides an additional state but also adds the possibility of improving the vertical load estimation. Finally, it is demonstrated that the TSE is able to perform in real time and shows fast convergence capabilities for cases in which the initial vertical load and/or sensor position are unknown or when moving away from situations in which the signal-to-noise ratio is poor.

Effectiveness of vertical posture recovery after external pushing impact in athletes specialized in different sports

The ability of athletes with different training specializations to recover vertical posture after an external pushing impact was studied. Athletes engaged in cyclic exercise sports (jogging, n = 7) and complex coordinate sports (wrestling, n = 10) and nonathletes (control, n = 10) were the subjects of this study. The recovery of vertical position after a small external pushing impact on the arms extended forward was assessed using stabilography. We determined the maximum amplitude (Amp-m) of deviation from the general center of pressure, the reaction time (RT) and the velocity of reaction (V-r), as well as the variance and mean velocity of vertical posture oscillations before and after an impact. It was found that, although no differences were observed in the vertical posture stability before pushing, the Amp-m was lower in the wrestlers than in the control group (by 17.5%, p = 0.018 under the eye-open conditions; by 27.3%, p = 0.002 under the eye-closed conditions). The deprivation of visual information about the pushing moment increases the Amp-m and V-r and had no effect on the RT in all groups. Under the eye-closed conditions, an increase in Amp-m as a result of pushing was significantly lower in the wrestlers (p = 0.033) than in the control group. Under the eye-closed conditions, the accuracy of the recovery of the initial vertical position after pushing was higher in the wrestlers than in the control group (p = 0.027). The indicators of postural stability, displacement of the center of pressure, and vertical posture sway and recovery after pushing did not differ between the runners and other groups. Therefore, compared to cyclic exercises, training in complex coordinating sports more effectively improves the ability to maintain vertical posture in response to its perturbation.

The effect of spine on the bounding dynamic performance of legged system

The effect of the spinal joint on the dynamic performance of a legged system in bounding gait is presented in this paper. We employ the simplified quadruped passive model to discuss the underlying mechanism of the bounding gait pattern. A comparison between the dynamic model with and without the spinal joint suggests that the model with a spinal joint is superior to the model with a rigid body in dynamic indicators including the vertical fluctuation of the centre of mass (CoM), leg forces and energy consumption. The effects of different initial included angles of the spinal joint and different initial vertical positions of the CoM on the dynamics of bounding are also analysed. We found that a low level of the energy consumption and leg forces can be obtained with the proper initial included angle and initial vertical position of the CoM, and there exists an optimal situation for each horizontal running velocity that the lowest energy consumption and the lowest leg forces could be obtained at the same time.

Experimental study of the particle paths in solitary water waves

We provide experiments that had been conducted to investigate the particle trajectory beneath a solitary water wave. Experimental results show that the surface drift is larger than the bottom drift. Meanwhile, the ratio of the net horizontal displacement to the total height of the trajectory at the free surface and subsurface will decrease with the initial vertical position and increase with the relative wave height.

Behavior of Suction Embedded Plate Anchors during Keying Process

Suction embedded plate anchors (SEPLAs) allow for accurate positioning, thus providing an attractive alternative to traditional drag embedment anchors. This paper presents an analytical model for predicting the behavior of SEPLAs during the keying process, with a specific focus on predicting the loss of embedment depth as the anchor rotates from its initial vertical position to its target orientation perpendicular to the direction of loading. The soil is idealized as an incompressible, rigid-plastic material obeying an associated-flow rule. A generalized plastic limit analysis is employed to estimate the trajectories and corresponding capacities of SEPLAs under different loading conditions. The effects of soil resistance on the shank and anchor interaction with the anchor chain are also considered in the model. The SEPLA design commonly features a hinged flap; the effect of the flap is examined theoretically by comparing the solutions for the SEPLA with and without flap. Predicted solutions are shown in reasonably good agreement with some published numerical and experimental results, supporting the validity of the model.

Factors Affecting Self-Eruption of Displaced Permanent Maxillary Canines

The aim of this study was to examine the possibility of the spontaneous eruption of displaced unerupted maxillary canines after the extraction of the deciduous canine and dental arch expansion and to determine the impact of initial canine position on treatment success rate. Materials and METHODS. The study sample included 50 patients (mean age, 13.5 years [SD, 2.2]) with unilaterally displaced unerupted maxillary canines. Deciduous canines were extracted, and the space for displaced canine was created at the beginning of the study. The follow-up period for the spontaneous eruption was 12 months. The initial vertical, horizontal, labio-palatal position and angle of inclination to the midline of the displaced canine were assessed on panoramic radiographs. RESULTS. Only 42% of displaced canines erupted spontaneously within one-year period (52.9% of labially displaced canines and 36.4% of palatally displaced canines). A significant difference of inclination was determined between spontaneously erupted and unerupted teeth in the labially displaced canine group (P<0.01), with no difference in the palatally displaced canine group. The receiver operating characteristic curve analysis showed that the critical angle of inclination for the spontaneous eruption of the retained canine was 20º (sensitivity 0.759; specificity 0.571; P<0.05). The majority of unerupted canines (75.9%) were inclined more than 20º. The initial height of canine was crucial for spontaneous eruption (sensitivity 0.966; specificity 0.81; P<0.001). This was true for both palatal and labial cases. CONCLUSIONS. The initial vertical position of the labially and palatally displaced canines and the inclination of the labially displaced canines were the most important predictors for spontaneous eruption of the cuspid.

Identifying the control of physically and perceptually evoked sway responses with coincident visual scene velocities and tilt of the base of support

In this study, we have explored whether the impact of visual information on postural reactions is due to the same perceptual mechanisms that produce vection. Pitch motion of the visual field was presented at varying velocities to eight healthy subjects (29.9+/-2.8 years) standing quietly on a stationary base of support or receiving a 3 degrees toes-up tilt of the base of support. An infrared motion system recorded markers placed on body segments to record angular displacement of head and ankle and calculate whole body center of mass. Onset of the visual field motion and base of support movement were synchronized in all trials. We found that in the first 2 s following onset of visual field motion, both direction and amplitude of the linear displacement of whole body center of mass and angular displacement of the head, hip, and ankle were modulated by the velocity of visual scene motion. When the visual scene rotated in upward pitch, subjects overshot their initial vertical position with amplitudes that increased as velocity of the visual field increased. This behavior was even more evident when the base of support was tilted. These responses were much shorter than those observed in studies of vection. The dependence of the postural response amplitudes on the velocity of the visual field suggests, however, that there might be well-shared control pathways for visual influences on postural reactions and postural sway elicited by an illusion of self-motion.

Initial Vertical and Horizontal Position of Palatally Impacted Maxillary Canine and Effect on Periodontal Status Following Surgical-Orthodontic Treatment

To evaluate the impact of surgical-orthodontic treatment and the initial vertical and mesiodistal position of palatally impacted maxillary canines on the periodontal health of impacted canines and adjacent teeth. The study group consisted of 32 patients with unilateral palatally impacted maxillary canines. The initial position of the impacted canines was assessed on panoramic images. The treatment protocol of the impacted canines included surgical exposure with the closed-eruption technique and fixed orthodontic appliances. A significant increase in pocket depth was found at the canine mesiopalatal point after surgical-orthodontic treatment. Also, a correlation was found between the initial mesiodistal and vertical position of the impacted canine and the posttreatment periodontal status of the impacted canine, the adjacent lateral incisor, and the first premolar. A combined surgical-orthodontic approach in the treatment of impacted maxillary canines produces clinically acceptable periodontal conditions. The average increase in pocket depth was less than 4 mm and clinically unimportant for most patients.

Transient simulations of the electrophoretic motion of a cylindrical particle through a 90° corner

The trajectory of a cylindrical particle driven by electrophoresis was transiently simulated as the particle moves through a 90° corner. A variety of system parameters were tested to determine their impact on the particle motion. The zeta potential, channel width, and particle aspect ratio were shown to have a minimal effect on the particle motion. Conversely, the initial vertical position of the particle and initial angle with respect to the horizontal had a significant impact on the particle motion. The presence of the 90° corner acts to reduce the initial distribution of angles to the vertical of 90° to less than 30°, demonstrating the possibility of using a corner as a passive control element as part of a larger microfluidic system. However, the reduction in angle is limited to the area near the corner posing a limitation on this means of control.

Vertical ocular responses to constant linear acceleration generated by fore–aft head translation in monkeys

We examined the vertical linear vestibuloocular reflexes (LVORs) elicited by constant linear acceleration (0–0.5 g for >95 ms) during transient fore–aft translation in three monkeys. In the dark condition, small but consistent downward ocular responses to forward translation were observed (latencies >41 ms) when the initial vertical eye positions were at 0°, although eye movements following backward translation were inconsistent among animals. These downward ocular responses showed the following three characteristics: they were independent of vertical gaze eccentricities, their magnitudes were almost proportional to the forward acceleration, and they were reduced by the large-field (not the spot) visual information. These characteristics revealed that the downward ocular responses to forward translation were the tilt LVORs. In addition, we recognized that the translational LVOR, which depended on vertical gaze eccentricities, was working at the same time. Our data suggest that constant linear acceleration during forward translation evokes the tilt LVOR, as well as the illusory tilting perception.

Three-Dimensional Kinematics at the Level of the Oculomotor Plant

Motor systems often require that superfluous degrees of freedom be constrained. For the oculomotor system, a redundancy in the degrees of freedom occurs during visually guided eye movements and is solved by implementing Listing's law and the half-angle rule, kinematic constraints that limit the range of eye positions and angular velocities used by the eyes. These constraints have been attributed either to neurally generated commands or to the physical mechanics of the eye and its surrounding muscles and tissues (i.e., the ocular plant). To directly test whether the ocular plant implements the half-angle rule, critical to the maintenance of Listing's law, we microstimulated the abducens nerve with the eye at different initial vertical eye positions. We report that the electrically evoked eye velocity exhibits the same eye position dependence as seen in visually guided smooth-pursuit eye movements. These results support an important role for the ocular plant in providing a solution to the degrees-of-freedom problem during eye movements.