Kinematic Effects Research Articles

Modeling and Design of Hinged Tile-Based Curling Air Surface for Morphing Windshield Cowling

Abstract The gap between the windshield and hood allows windshield wipers to operate, but causes problems gathering leaves and snow. Active morphing approaches provide an opportunity to create a windshield cowling that addresses this issue by covering the gap normally and actively curling out of the way to allow wiper operation. Most existing morphing techniques lack simultaneous large force/stroke generation, cannot perform two-way actuation, or fail to rigidly hold their position against varying loads such as wind. This article studies a novel curling air surface based on hinged T-shaped tiles that improve upon existing technologies by adding straightening actuation to out-of-plane curling with large force and deflection, while also holding position rigidly. Through vacuuming an upper curling bladder enclosing the tiles and inflating lower straightening bladders spanning the hinge lines, the air surface uncovers and covers the gap against wind loads and holds its curled position rigidly using inter-tile hard stops. An analytical surface model aggregated from multiple instances of a first principle unit curling model predicts the air surface performance. This model includes additional kinematic effects, extending the range of applicability, and additional bladder effect phenomenological terms to improve accuracy. The model is validated across scales and enables design space visualization, which is applied to design a windshield cowling. The resulting design is validated and demonstrated in a full-scale prototype. This article provides the technology concept, supporting model, and design approach to broadly apply this useful air surface to other morphing applications.

Kinematics of the axial segment of horses submitted to dynamic mobilization exercises

This study aimed to investigate the kinematic effects of dynamic mobilization exercises on the axial segment in horses. Twelve horses crossbreed were used, which were monitored before (day 0) and at the end of the experimental period (day 120), distributed in an entirely randomized design, totalizing six repetitions per treatment The treatments consisted of two experimental groups, one composed of horses not performing the dynamic mobilization exercises and the other composed of horses submitted to the mobilization program. The static kinematic variables were evaluated, by means of hemispherical markers such as depth (cm), angle (°), difference in depth and angle, for each vertebral level analyzed (T10, T13, T17, L1 and L3), as well as total range of motion for depth and angle, in which this parameter expressed the thoracolumbar motion in its entirety. The performance of dynamic mobilization produced a significant (P<0.05) decrease in thoracolumbar depth and increase in thoracolumbar flexion angle, compared to the group that did not perform the functional exercises. A reduction in the total thoracolumbar depth of -6.28 cm (P<0.0001) was observed in horses that underwent the exercises. The same response behavior was verified for angular measurement, in which there was an increase in the total ROM of the angle, reflecting thoracolumbar flexion, of 15.54°(P<0.00001). It was concluded that dynamic mobilization exercises consistently produce flexion of the axial segment, becoming a potential tool to improve range of motion and thoracolumbar function in horses.

Nonlinear field effects in the collector ring due to large-amplitude particle oscillations

In the frame of the FAIR project, the Collector Ring (CR) is planned to be built for efficient cooling of antiprotons and rare isotope beams [1]. In order to accept hot beam from separators large acceptances are required. This paper examines the effects which can influence the beam dynamics due to large betatron oscillation amplitude and momentum spread. Using analytic expressions, the amplitude-dependent tune shifts driven by sextupole magnets, the fringe field of quadrupole magnets, and kinematics effects have been calculated. The obtained results have been compared with numerical simulations by means of precise multi-turn particle tracing. The tracking analysis for the CR has been performed considering the real shape of the magnetic field of the wide aperture quadrupole. We report on quantitative studies of the effects on the dynamic aperture of the rings.

Comparative Efficacy of Open-Chain Kinematics and Closed-Chain Kinematics on Walking Proficiency and Societal Integration in Post-Stroke Individuals

Background: Post-stroke hemiplegic gait is a mixture of deviations and compensatory motion dictated by residual function. To improve stroke survivors' walking ability, it is necessary to evaluate different rehabilitation approaches and identify those that have a greater effect on locomotor recovery of stroke patient. This will improve their general wellbeing by promoting better health and greater community participation, for faster societal integration. Aim: This study compared the effect of open-chain kinematics (bicycle ergometry) and closed-chain kinematics (treadmill) on walking proficiency in post-stroke individuals and their societal integration. Methods: This was a pretest-posttest experimental study involving 35 ambulatory hemiplegic stroke survivors (18 males and 17 females) with a mean age of (53.77 ± 10.95) undergoing rehabilitation at Lagos University Teaching Hospital, Idi Araba and Lagos State University Teaching Hospital, Ikeja. Patients went through 10-week rehabilitation and were randomly assigned to two intervention groups (treadmill and bicycle ergometry groups). Spatio-temporal gait parameters were measured by the six-metre walkway and community integrated questionnaire was used to examine home integration, social integration and productive activities. Data were subjected to inferential and descriptive statistics. Paired t-test was used to analyse the outcomes within the two groups and independent t-test was used to analyse the data between the groups. The level of significance was set at p ≤ 0.05. Results: Results showed significant difference between baseline and post intervention scores for all the gait parameters; stride length (p = 0.001), step length (p = 0.00), natural gait speed (p = 0.00), maximum gait speed (p = 0.01), cadence (p = 0.00) and community integration (p = 0.00) for the participants in the treadmill group; step length (p = 0.001), natural gait speed (p = 0.01), maximum gait (p = 0.02), cadence (p = 0.03) and community integration (p = 0.00) for the participants in the bicycle ergometer group except for stride length which showed no significance difference (p = 0.078). There was also a significant difference in the mean change in cadence between the treadmill and bicycle ergometer group (p = 0.04). Conclusion: Both open-chain and closed-chain kinematics are effective, but closed- chain is most effective in re-educating ambulation and re-gaining spatio-temporal gait parameters after stroke and should be structured into the patients’ treatment regimen to effectively improve functional capability in post-stroke individuals.

Kinematical effects of rifle carriage on roller skiing in well-trained female and male biathletes.

This study aimed to investigate how rifle carriage and skiing speed during biathlon roller skiing affect range of motion (ROM) in joint angles and equipment (skis and poles), the vertical distance between shoulders and treadmill (vertdist ), as well as possible sex differences associated with rifle carriage. Fourteen biathletes (6 women, 8 men) roller-skied on a treadmill at submaximal and simulated race speeds, with (WR) and without (NR) a rifle, using gears 3 and 2. Kinematical data for the whole body, poles, roller-skis, rifle, and treadmill were monitored using a 3D motion capture system. Movements determined as flexion/extension (x), abduction/adduction (y), and/or internal/external rotation (z) were analyzed for the hip, shoulder, thorax, knee, ankle, elbow, poles, and roller skis. ROM (the difference between maximal and minimal angles) in joints and equipment, and vertdist were analyzed over six skiing cycles during each condition (WR and NR) and speed. The maximal vertdist was lower for WR compared with NR (gear 3: 1.53 ± 0.06 vs 1.54 ± 0.06 m; gear 2: 1.49 ± 0.06 vs 1.51 ± 0.06 m; both p < 0.001). ROM in the upper body was altered when roller skiing WR (movements decreased in thorax and shoulder (x) and increased in elbow (only gear 3) (x), thorax (only gear 2), and shoulder (y) and (z); all p < 0.05) and increased with speed, without differences between sexes (p > 0.05). Since rifle carriage and speed appear to affect the kinematics of roller skiing, coaches, and biathletes are advised to perform skiing technique training under competition-like conditions (i.e., at race speeds while carrying the rifle).

Studying triangle singularity through spin observables

In this work, we study the spin density matrix element $\rho_{00}$ of the $\phi$ in the decay $J/\psi \rightarrow \eta \pi \phi$. In previous studies, a band around 1.4 GeV on the $\pi^0\phi$ distribution in Dalitz plot was reported by the BESIII Collaboration. This structure may be caused by the production of a resonance or the triangle singularity mechanism. We find that the predictions of the spin density matrix elements of the final $\phi$ based on these mechanisms show distinct features. Thus the measurement of the spin density matrix elements of the $\phi$ in this reaction may offer an alternative way to study the triangle singularity and to clarify the reaction mechanisms, i.e. resonance production or kinematic effects. This work also shows the potential of spin observables in studying kinematic singularities.

Effects of temperature on the properties of HL32 oil in the conventional hydraulic actuators

Present study pays more attention to optimize the performance of the hydraulic system by selecting the accurate position of the traditional hydraulic actuators. It was used HL32 as working oil, due to its ability to withstand high temperatures (15–200) °C as well as having the best mechanical properties, since the density and viscosity are the most important factors that are extremely affected on the hydraulic system. Hence, this work examined the effect of the variation kinematic, dynamic viscosity, and the density of HL32 oil on the accurate position of conventional hydraulic actuators. The kinematic and dynamic viscosity was obtained theoretically and experimentally over a wide range of temperatures ranged (20–80) °C. It was found that the percentage error between the theoretical and experimental results ranged (21∗10−6–0.023), respectively. Whereas, the deviation of the results in the actuator stroke displacement were observed 4.8%, 6%, 6.5% and 4.8% for pressure supply of 20, 30, 40 and 50 bar separately.

Теоретические обоснования эффекта Саньяка

It is the first article of the two ones related to the Sagnac effect, the one of the main relativistic effects to be taken into account for synchronization of clocks in working global navigation satellite systems. Its sense consists of retarding/advancing signals propagating in opposite directions at the perimeter of a rotating disc. In the present article its theoretic foundation is given both within the framework of a kinematical effect in special relativity and in that of general relativity, where the effect is analyzed as a result of centrifugal forces potential’s action. Besides, in both the theories two various approaches are applied. This enables delving into physical sense of the phenomenon. This theoretical presentation is used in the second article of the series to outline the effect under real conditions at location on the surface of rotating Earth, when optical fiber link is used for synchronization of atomic clocks.

Effect of Situation Kinematics on Drivers’ Rear-End Collision Avoidance Behaviour—A Combined Effect of Visual Looming, Speed, and Distance Analysis

Considering the large proportion of rear-end collisions occurring in our daily life and the severity it may lead to, the objective of this study was to investigate the effect of situation kinematics on drivers’ rear-end collision avoidance behaviour after brake onset. A wide range of lead vehicle deceleration scenarios were designed based on driving simulator experiments to collect drivers’ deceleration behaviour data. Different from measures (e.g., speed, the lead vehicle’s deceleration et al.) often adopted in previous studies, a visual looming-based measure at different time points was calculated combined with analysis of speed and distance to quantify situation kinematics in this study. The Spearman’s nonparametric rank correlation test was firstly conducted to examine the correlation between visual looming-based metrics and related deceleration behaviour. The mixed model was performed on drivers’ brake jerk and maximum deceleration rate, while the logistic model was then performed to predict the probability of the occurrence of rear-end collisions. Spearman’s nonparametric test showed that both deceleration ramp-up and drivers’ maximum deceleration rate increase significantly as the looming traces increase faster. Results of the logistic model indicated that the probability of occurrence of a potential collision might be higher if the situation at the brake onset is quite urgent and braking is moderate. It was demonstrated that both drivers’ deceleration ramp-up and maximum deceleration rate could be highly kinematic-dependent, and visual looming, driving speed, and distance can be useful information for drivers to take relative deceleration actions.

Modified direct method in static problems of axi-symmetric non-thin plates

The initial equations for solving the axisymmetric problem are given and consideredboundary conditions on the end surfaces and average section of the design element. As a result, we get a system of partial differential equations that can be solved by the numerical-analytical (modified) method of straight lines. The transformation of the reduced equations of equilibrium in parts, as well as the reduced models of the boundary conditions of the end surfaces and the average section, are shown. As a result, a boundary value problem for the system of reduced differential equations in ordinary derivatives written in the Cauchy form with boundary conditions of the general form is obtained.&#x0D; The thermal conductivity of the cylindrical wall was calculated, the results were compared with analytical calculations and results of other authors, which confirms the reliability of the developed methodology.&#x0D; A computer simulation of the stress-strain state of a cylindrical structural element due to the complex action of temperature, force and kinematic effects was carried out.&#x0D; Important conclusions have been made for the use of the modified method of straight lines, which is free from the complications that arise when using the classical method of straight lines.

Effects of kinematic and magnetic boundary conditions on the dynamics of convection-driven plane layer dynamos

Rapidly rotating convection-driven dynamos are investigated under different kinematic and magnetic boundary conditions using direct numerical simulations. At a fixed rotation rate, represented by the Ekman number$Ek=5\times 10^{-7}$, the thermal forcing is varied from$2$to$20$times its value at the onset of convection ($\mathcal {R}=Ra/Ra_c=2\unicode{x2013}20$, where$Ra$is the Rayleigh number), keeping the fluid properties constant ($Pr=Pr_m=1$, where$Pr$and$Pr_m$are the thermal and magnetic Prandtl numbers). The statistical behaviour of the dynamos, including the force balance, energetics, and heat transport, depends on the boundary conditions that dictate both the boundary layer and the interior dynamics. At a fixed thermal forcing ($\mathcal {R}=3$), the structure and strength of the magnetic field produced by the dynamos, especially near the walls, depend on both velocity and magnetic boundary conditions. Though the leading-order force balance in the bulk remains geostrophic, the Lorentz force becomes comparable to the Coriolis force inside the thermal boundary layer with no-slip, perfectly conducting conditions. In this case, a term signifying the work done by the Lorentz force in the turbulent kinetic energy (TKE) equation is found to have some components that extract energy from the velocity field to produce the magnetic field, while some other components extract energy from the magnetic field to produce TKE. However, with no-slip, pseudo-vacuum conditions, all the components of the work done by the Lorentz force perform unidirectional energy transfer to produce magnetic energy from the kinetic energy of the fluid to sustain dynamo action. We find heat transfer enhancement in the rotating dynamo convection, as compared with non-magnetic rotating convection, with the peak enhancement lying in the range$\mathcal {R}=3\unicode{x2013}4$. For free-slip conditions, in the absence of an Ekman layer, the dynamo action may alter the heat transport significantly by suppressing the formation of large-scale vortices. However, the highest heat transfer enhancement is found at$\mathcal {R}=3$with no-slip, perfectly conducting walls, which can be attributed to a local magnetorelaxation of the rotational constraint due to enhanced Lorentz force inside the thermal boundary layer.

Comparison of the Effectiveness of Kinesiology Taping and Rigid Taping on Ankle Kinematics During Drop Landing in Individuals with Lateral Ankle Injury.

Lateral ankle sprain is an injury that often occurs during sports or daily life activities. Athletic tape and kinesiology tape applications are among the external support treatment options especially for athletes to support the ankle and protect it from recurrent sprains. We sought to compare the kinematic stabilization effects of different ankle taping applications on the ankle joint during drop landing in individuals with a history of unilateral lateral ankle injury. In this randomized controlled study, 30 volunteers with unilateral ankle injury were evaluated. The participants were asked to land on one leg on the involved side and the contralateral side from a 30-cm-high platform. The same practice was repeated after applying kinesiology tape and rigid tape to the injured foot. Kinematic analysis of the foot and ankle was performed by recording three-dimensional spatial position information at a speed of 240 frames per second using infrared cameras. The highest inversion angles of the involved foot at initial contact and 150 msec after initial contact were higher than those of the uninvolved side (P = .03 and P = .04, respectively). There was no significant difference in ankle kinematic values in the involved foot among kinesiology taping, athletic taping, and no taping applications (P = .74). People with lateral ankle sprains show reduced inversion during landing. There were no significant differences among kinesiology taping, athletic taping, and no taping on the injured foot in terms of ankle kinematics. Care should be taken when using taping materials as protective measures for sports activities.

Density-driven exchange flow propagating over an array of densified obstacles

The evolution of bottom-propagating gravity currents with the presence of an array of densified obstacles submerged in a channel is investigated using large-eddy simulations. Our attention is particularly focused on the flow transition of gravity currents over rough surfaces with extra resistance that provokes significant dissipative processes. Two geometric parameters of the roughness elements, namely, the submergence ratio of the obstacle D/H and the gap-spacing ratio λ/D between obstacles, govern their kinematic and dynamic effects on the propagation of gravity currents. Physically, D/H plays a significant role in the control of the current diversion, and λ/D regulates the flow pathway of gravity current propagation. The integrated measures show that two distinct flow morphologies are identified. For a low submergence ratio (D/H&amp;lt;0.15), an overtopping flow is formed in which the gravity current travels on the top of the array and undergoes an inconspicuous loss of buoyancy, subject to minimal vertical convective instability interacting with the underlying ambient fluid within the gap regions. For a sufficiently high submergence ratio (D/H≥0.15) and a certain gap spacing (2≤λ/D&amp;lt;4), an overrunning flow is formed in which the current rapidly decelerates to a buoyancy–inertia state and then transitions to a drag-dominated state with a gain in excessive drag, in which the front velocity is proportional to t−0.5. However, the simulation results show a turning point toward an increase in the gap spacing as λ/D≥4, that the maximum drag acting on the gravity current is measured when it impinges on the second obstacle of an array, and that the drag coefficient goes up by 10%–40%, depending on D/H. The propagation of the gravity current does not show a higher sensitivity to the retarding effect instead. Meanwhile, the promotion of energy conversion occurs because of the gravity current encountering the continuous climbing and plunging flow behavior between two adjacent obstacles in regular motions.

The dipole of the astrophysical gravitational-wave background

One of the main pillars of the ΛCDM model is the Cosmological Principle, which states that our Universe is statistically isotropic and homogeneous on large scales. Here we test this hypothesis using the Astrophysical Gravitational Wave Background (AGWB) expected to be measured by the Einstein Telescope-Cosmic Explorer network; in particular we perform a numerical computation of the AGWB dipole, evaluating the intrinsic contribution due to clustering and the kinematic effect induced by the observer motion. We apply a component separation technique in the GW context to disentangle the kinematic dipole, the intrinsic dipole and the shot noise (SN), based on the observation of the AGWB at different frequencies. We show how this technique can also be implemented in matched-filtering to minimize the covariance which accounts for both instrumental noise and SN. Since GW detectors are essentially full-sky, we expect that this powerful tool can help in testing the isotropy of our Universe in the next future.

Fermi motion effects in electroproduction of hypernuclei

In a previous analysis of electroproduction of hypernuclei the cross sections were calculated in distorted-wave impulse approximation where the momentum of the initial proton in the nucleus was set to zero (the frozen-proton approximation). In this paper we go beyond this approximation assuming a non zero effective proton momentum due to proton Fermi motion inside of the target nucleus discussing also other kinematical effects. To this end we have derived a more general form of the two-component elementary electroproduction amplitude (Chew-Goldberger-Low-Nambu like) which allows its use in a general reference frame moving with respect to the nucleus-rest frame. The effects of Fermi motion were found to depend on kinematics and elementary amplitudes. The largest effects were observed in the contributions from the longitudinal and interference parts of the cross sections. The extension of the calculations beyond the frozen-proton approximation improved the agreement of predicted theoretical cross sections with experimental data and once we assumed the optimum on-shell approximation, we were able to remove an inconsistency which was previously present in the calculations.

Influence of different kinematics on stationary and dynamic torsional behavior of JIZAI nickel-titanium rotary instruments: An in vitro study

Using conventional approach to examine stationary torque of nickel-titanium rotary instruments contradicts the clinical condition, and its validity for motions involving clockwise and counterclockwise rotations is questionable. This study aimed to examine the effect of different kinematics on the torsional behavior using a JIZAI instrument (#25/.04) under stationary/dynamic test conditions using clinical torque limit settings. In the stationary test, the 5-mm tip of JIZAI was fixed in a cylinder-shaped vise and rotated in continuous rotation (CR) with auto-torque-reverse, optimum-torque-reverse (OTR), or reciprocation (REC) until fracture (n = 10, each). In the dynamic test, straight and severe curved canals were instrumented with JIZAI using the single-length technique with CR, OTR, or REC (n = 10, each). The stationary torque at fracture, time to fracture (Tf), dynamic torque, and screw-in force were recorded using automated-shaping-device with torque/force measuring unit. One-way ANOVA or Kruskal–Wallis test and Mann–Whitney U test with Bonferroni correction were used for statistical analysis (⍺ = 0.05). The kinematics did not influence the stationary or dynamic torques (P > 0.05); however, did influence the screw-in force in straight canals (P < 0.05). REC had significantly longer Tf, and severe curved canals yielded significantly greater torque and screw-in force in CR (P < 0.05). Under the present experimental conditions, parameters other than torque showed significant effects on different kinematics. The dynamic torque and screw-in force of OTR were similar to the other rotational modes and not influenced by the canal curvature.

Hydrodynamic Manifestations of Gravitational Chiral Anomaly.

The conservation of an axial current modified by the gravitational chiral anomaly implies the universal transport phenomenon (kinematical vortical effect) dependent solely on medium vorticity and acceleration, but not dependent explicitly on its temperature and density. This general analysis is verified for the case of massless fermions with spin-1/2.

The Filtering Effect of Pile Foundations in Clay

This paper reports the results of a series of centrifuge experiments exploring the dynamic response of pile foundations. The model tested in a centrifuge at 50g consisted of an isolated pile and two pile groups embedded in a kaolin clay, subjected to a sequence of quasi-sinusoidal waves with different amplitudes and frequencies. The results are back-analyzed through a two-step procedure. First, a one-dimensional ground response analysis is performed, in which the small-strain shear modulus is evaluated using data from air hammer tests, while a literature model is used to account for nonlinearity of soil behavior. Second, a three-dimensional finite-element analysis of the model foundations is carried out using the mobilized soil damping ratio and shear modulus determined from the previous step. The aforementioned procedure allowed to reproduce satisfactorily the response of the model foundations tested in the centrifuge, showing that the response of these models is strongly affected by the inertial oscillation of the cap connecting piles necessary to accommodate the measurement devices and to rigidly connect the piles’ heads of the groups. The same numerical model was then adopted to evaluate the change of seismic motion due to pure kinematic interaction effects by setting the pile cap mass equal to zero. This allowed to check the prediction capability of simplified methods of analysis for the evaluation of the base excitation of pile-supported structures. In addition, a number of issues related to the execution of centrifuge tests aimed at investigating the kinematic interaction between pile and soil are highlighted and discussed.

NUMERICAL SIMULATION OF THE PROCESS OF DIRECTED TRANSFORMATION OF A REGULAR HINGE-ROD SYSTEM

The process of forming new architectural solutions in the field of regular frame-rod systems necessitates the development of the concept of creating original spatial structures through the directed transformation of kinematically changeable truss-type objects. The article presents a numerical study of kinematic parameters during the gradual shaping of a rod system, which in its initial state is a flat hinge-rod network of repeating fragments in the form of equilateral triangles. The controlled kinematic effect on the object was modeled using actuators that were placed on the peripheral sections of the studied grids. The wide variability of the hinge-rod forms, the economical installation process using the principle of "self-extension" allow us to speak about the relevance of research in this direction.

Anguilliform and carangiform fish-inspired hydrodynamic study for an undulating hydrofoil: Effect of shape and adaptive kinematics

This work is motivated by the fact that the thinner-anguilliform and thicker-carangiform types of fish adapt to each other's kinematics under certain conditions. Our two-dimensional hydrofoil model-based numerical simulations demonstrate that the adaptive kinematics increases thrust force for the thinner-fish while it increases propulsive efficiency for the thicker-fish; as found in nature. Further, hydrodynamic reasons are discussed for such adaptive behavior. This bioinspired and biomimetics study may assist need-based efficient design of underwater-vehicles.