Rotational Motion Research Articles

Moisture actuated cobalt alginate discoloration artificial muscle

Artificial muscles have the ability to sense changes in the external environment and generate rapid and significant contraction deformation or rotational motion. However, most artificial muscles are limited to a single form of deformation, and there are still great difficulties in achieving complex dual response modes. Herein, a novel artificial muscle made of cobalt alginate fiber with both rotational/contraction deformation and discoloration functions was successfully prepared by a simple wet spinning and directional twisting methods. The wet-sensitive color change performance is achieved by the formation of different hydrates of cobalt ions in varying humidity conditions, while rotational motion is induced by radial untwisting resulting from fiber swelling upon moisture absorption. In addition, the artificial muscle fiber exhibited a transition from blue to purple to red as the environmental humidity changes from 35 % to 85 %. When the fibers were exposed to water, the twisted fiber with a twist count of 2500 truns provided a rotational speed of over 2000 rpm, and the actuating and discoloration performance did not significantly decrease in 50 repeated cycle tests. This stable shape and color dual response artificial muscle can simulate traditional windmill devices, while also providing a new design idea for smart textiles and humidity visualization devices.

ALMA reveals a compact and massive molecular outflow driven by the young AGN in a nearby ULIRG

ABSTRACT The ultraluminous infrared galaxy F13451+1232 is an excellent example of a galaxy merger in the early stages of active galactic nucleus (AGN) activity, a phase in which AGN-driven outflows are expected to be particularly important. However, previous observations have determined that the mass outflow rates of the warm ionized and neutral gas phases in F13451+1232 are relatively modest, and there has been no robust detection of molecular outflows. Using high-spatial resolution Atacama Large Millimeter/submillimeter Array CO(1–0) observations, we detect a kiloparsec-scale circumnuclear disc, as well as extended (r ∼ 440 pc), intermediate-velocity (300 < |v| < 400 km s−1) cold molecular gas emission that cannot be explained by rotational disc motions. If interpreted as AGN-driven outflows, the mass outflow rates associated with this intermediate-velocity gas are relatively modest ($\dot{M}_\mathrm{out}=22$–27 M⊙ yr−1); however, we also detect a compact (rout < 120 pc), high-velocity (400 < v < 680 km s−1) cold molecular outflow near the primary nucleus of F13451+1232, which carries an order of magnitude more mass ($\dot{M}_\mathrm{out}$ ∼ 230 M⊙ yr−1) than (and several times the kinetic power of) the previously detected warmer phases. Moreover, the similar spatial scales of this compact outflow and the radio structure indicate that it is likely accelerated by the small-scale (r ∼ 130 pc) AGN jet in the primary nucleus of F13451+1232. Considering the compactness of the nuclear outflow and intermediate-velocity non-rotating gas that we detect, we argue that high-spatial resolution observations are necessary to properly quantify the properties of AGN-driven outflows and their impacts on host galaxies.

Dynamics of Fluids in the Cavity of a Rotating Body: A Review of Analytical Solutions

Since the middle of the 20th century, an understanding of the diversity of the natural magnetohydrodynamic phenomena surrounding us has begun to emerge. Magnetohydrodynamic nature manifests itself in such seemingly heterogeneous processes as the flow of water in the world’s oceans, the movements of Earth’s liquid core, the dynamics of the solar magnetosphere and galactic electromagnetic fields. Their close relationship and multifaceted influence on human life are becoming more and more clearly revealed. The study of these phenomena requires the development of theory both fundamental and analytical, unifying a wide range of phenomena, and specialized areas that describe specific processes. The theory of translational fluid motion is well developed, but for most natural phenomena, this condition leads to a rather limited model. The fluid motion in the cavity of a rotating body such that the Coriolis forces are significant has been studied much less. A distinctive feature of the problems under consideration is their significant nonlinearity, (i.e., the absence of a linear approximation that allows one to obtain nontrivial useful results). From this point of view, the studies presented here were selected. This review presents studies on the movements of ideal and viscous fluids without taking into account electromagnetic phenomena (non-conducting, non-magnetic fluid) and while taking them into account (conducting fluid). Much attention is payed to the macroscopic movements of sea water (conducting liquid) located in Earth’s magnetic field, which spawns electric currents and, as a result, an induced magnetic field. Exploring the processes of generating magnetic fields in the moving turbulent flows of conducting fluid in the frame of dynamic systems with distributed parameters allows better understanding of the origin of cosmic magnetic fields (those of planets, stars, and galaxies). Various approaches are presented for rotational and librational movements. In particular, an analytical solution of three-dimensional unsteady magnetohydrodynamic equations for problems in a plane-parallel configuration is presented.

The influence of imbalances on the dynamic characteristics of the laboratory centrifuge HERMLE Z306

Laboratory centrifuges are used in various industries. During operation, vibrations occur that lead to resonant frequencies, which in turn impair functionality. This paper presents an overview of the computational model of the HERMLE Z306 laboratory centrifuge used in medical laboratories to separate mixtures of different fractions to determine the dynamic characteristics. The zones of stable operation of the centrifuge and the influence of the rotation speed on the natural frequencies are analytically determined. Experimental results are presented with the influence of imbalances on the dynamic characteristics of the HERMLE Z306 centrifuge. As a result of the modeling, the amplitude-frequency characteristics are determined and a Campbell diagram is constructed. Objective: Modeling of dynamic processes in laboratory centrifuges by studying the influence of imbalances on the quality of mixture separation. Determination of zones of stable operation of the centrifuge.Purpose: Construction of amplitude-frequency characteristics of the centrifuge, determination of zones of stable operation of the laboratory centrifuge during separation and Campbell diagram showing the dependence of natural frequencies on the rotation speed of the HERMLE Z306 centrifuge. This diagram makes it possible to determine the resonance zones. Methods of implementation: Based on the use of the Lagrange equation of the second kind, a model is obtained that makes it possible to determine the zones of stable operation of the centrifuge. Using experimental equipment, determine the frequency response of the centrifuge and analyze the Campbell diagram to determine the resonance zones.Results: The zones of stable operation of a laboratory centrifuge were analytically determined. The amplitude-frequency characteristics of the HERMLE Z306 centrifuge were constructed, the trajectories of the free end of the shaft were built taking into account the corresponding imbalances, and the resonance zones were experimentally determined. Conclusions: Experimental studies have shown that the free end of a laboratory centrifuge shaft moves along a surface whose shape and, accordingly, the path of movement depend on both the angles of rotation and translational movement that arise as a result of deformations of elastic supports. The analytical and experimental studies made it possible to identify unstable modes and thereby determine the areas of the centrifuge's operating modes. The separation process will be stable if the roots of the equation have a negative real part, and moreover, the motion will be asymptotically stable in the presence of resistance forces. An experimental technique for determining the dynamic parameters of the centrifuge has been developed. On its basis, the effect of the rotation speed on the natural frequencies was determined.

Conceptualization and Topology Optimization of Ampheel: An Integration of Rolling Wheel and Turtle-Inspired Mechanism for Amphibious Mobile Robot

The primary distinguishing feature of mobile robots is the ability to traverse various environments, setting them apart in the realm of robotics. The mobility of a robot hinges primarily on its locomotion mechanism, which dictates how it moves. The existing unimodal mobile robots are limited to work within the environment for which they are designed for and hence lack a scope to adapt the change in the terrain especially when they put to work in a mixed environment like land and water. Many applications like land and underwater search/rescue, shore infrastructure inspection, coastal area defence and security, offshore energy harvesting, space exploration, etc. demand a mobile robot that can traverse in both terrestrial and aquatic environments with the help of dual or multimodal locomotion mechanism, something like an amphibious animal. Most of the available amphibious robotic solutions have different appendages for both the environment, need human intervention to changeover the mechanism for transition, require different driving system for land and water locomotion and have fragile structures that limit the manoeuvrability. The proposed conceptual design called “Ampheel” is a novel amphibious locomotion mechanism inspired by the biomechanics of freshwater turtles. Ampheel incorporates a rigid wheel, enabling the robot to move on land, integrating soft actuators within it which emulate the turtle's leg-like extensions and enable the aquatic locomotion. Unlike the existing amphibious robots, the Ampheel utilizes the rotational motion of itself as a common driving system for both the environments. This reduces the need of multiple driving systems and also simplifies the control system. Ampheel is designed for safe travelling on land considering the maximum payload of robot as 20 kg including self-weight. Topology optimization of Ampheel is also carried out using ANSYS software for reduction of weight. Additionally, a unique interfacing shaft is designed that transmits the required torque to Ampheel for rotation and also channelise the compressed air to soft pneumatic actuators for inflation during rotation of Ampheel in aquatic setting. The fabricated Ampheel assembly is experimentally checked for failure under the applicable loading condition and found safe.

Intrinsic dissolution rate modeling for the pharmacopoeia apparatus rotating disk compared to flow channel method

For a solid understanding of drug characteristics, in vitro measurement of the intrinsic dissolution rate is important. Hydrodynamics are often emphasized as the decisive parameter influencing the dissolution. In this study, experiments and computational fluid dynamic (CFD) simulations showed that the mixing behavior in the rotating disc apparatus causes an inhomogeneous flow field and a systematic error in the calculation of the intrinsic dissolution rate. This error is affected by both the experimental time and the velocity. Due to the rotational movement around the tablet center, commonly utilized in pharmacopeia methods, a broad variance is present with regard to the impact of fluid velocity on individual particles of the specimen surface. As this is significantly reduced in the case of uniform overflow, the flow channel is recommended for investigating the dissolution behavior. It is shown that rotating disc measurements can be compared with flow channel measurements after adjusting the measured data for the rotating disc based on a proposed, representative Reynolds number and a suggested apparatus-dependent correction factor. Additionally, modeling the apparatus-independent intrinsic dissolution rate for different temperatures in the rotating disc apparatus is possible using the adapted Levich’s equation.

Dynamical analysis of a ferrofluid subjected to oscillatory field and shear rates: Applications to magnetic hyperthermia

The dynamical magnetic response of a small sample of ferrofluid is investigated numerically. A validated in-house research code is used to compute the translational and rotational motion of the particles. This code uses a robust scheme of Ewald summation to compute long-range periodic torques and forces between the particles. The model of the ferrofluid consists in a suspension of magnetic hard spheres replicated in lattices to ensure the convergence of the system’s transport properties. Ensemble averages over several realizations for each simulation are carried out. The suspension is subjected to field and shear time-dependent excitations. The effect of magnetic hyperthermia is evaluated by the average rate of internal energy dissipation due to an oscillatory magnetic field and oscillatory shear rate. Nonlinear dynamical tools such as phase spaces and Poincaré maps are applied to interpret the dynamical behavior of the suspension. Results show that when the suspension reaches its saturation magnetization due to a delayed time-response of the particles the internal energy dissipation decreases with respect to the local applied field. The Poincaré maps reveal that in dilute regimes the system presents quasi-periodic behavior for an alternating magnetic field. Also, the application of an oscillatory shear-rate increases the bulk internal energy of the system due to the magneto-viscous effect, even though it diminishes the internal area of the hysteresis loop. This work brings a better understanding of the dynamical response of ferrofluids that could be useful in magnetic hyperthermia applications.

Speed-power training of highly qualified hammer throwers

Long-term training of highly qualified track and field athletes is impossible without paying attention to one of its constituent parts - training and training methods. The level of training of throwers in track and field is becoming very high, it is becoming more and more difficult to achieve victory. This caused certain efforts of trainers, scientists, and methodologists in preparing the educational and training process of track and field athletes-throwers. The study of the robots of specialists, as well as the analysis of existing programs for improving the speed and strength training of throwers in track and field, indicates that the training method lags behind modern requirements. We consider the reason for this to be the low level of methodical development. Unfortunately, most track and field coaches are not interested in the new guidelines, and the result is the training of inferior reserves.
 The purpose of the work is the development of speed and strength training of highly qualified hammer throwers.
 Research results. We recommend hammer throwers to perform exercises with a barbell during training (jerking, taking the barbell to the chest, pull-ups). Exercises with a barbell (jerk, chest pull-ups, pull-ups and push-ups) are recommended to be performed from the position "from above". The position of the barbell "from above" means that the barbell is raised from the platform with straight lowered arms, the athlete's torso and legs are straightened, and then basic exercises are performed from this position. Moreover, the exercises should be performed in the overcoming and advancing mode, which corresponds to the main technical movement - hammer throwing.
 Conclusions. The results of our research and thirty years of practical experience working with athletes of the highest level of sportsmanship show that in speed-power sports, the connection between the external form and the content of movements is most clearly manifested when interacting with the support and the projectile. This is a causal relationship. Only that athlete who has a sufficient level of development of speed and strength qualities across the entire range of their manifestations, from the fastest and most coordinated rotational movements to the instant manifestation of maximum muscle tension in projectile throwing, can count on serious success in the main exercise.

Hydro- and aero-elastic response of floating offshore wind turbines to combined waves and wind in frequency domain

An analytical approach and numerical solution to determine coupled aeroelastic and hydroelastic response of floating offshore wind turbines of arbitrary shape to combined wind and wave loads is presented. The model considers simultaneously the aerodynamic and hydrodynamic loads on an FOWT and integrates these with finite element method for structural analysis due to the combined loads. The hydrodynamic and aerodynamic loads are determined based on the linear wave diffraction theory and steady blade element momentum method, respectively, and the solution is obtained in frequency domain. The structure may be fixed or floating, located in arbitrary water depth, and may host single or multiple wind towers. The model captures the complete translational and rotational motions of the body in three dimensions, and the elasticity of the blades, tower and the floating platform. To assess the performance of the model, rigid and elastic responses of a FOWT to combined wave and wind loads are computed and compared with available laboratory measurements and other theoretical approaches where possible, and overall very good agreement is observed. The model developed in this study addresses directly three shortcomings of existing approaches used for the analysis of FOWTs, namely (i) determination of the elastic responses of the entire structure including the floating platform, (ii) analysis of the motion and elastic response of FOWTs in frequency domain, and (iii) assessment of responses of FOWTs with single or multiple wind towers.

Modeling coupled growth and motion of solid-air dendrite induced by convection in liquid hydrogen using phase-field lattice Boltzmann method

The safety hazard arising from the growth, condensation and accumulation of trace air in liquid hydrogen deserves attention. In order to predict the microstructural growth evolution and oxygen solute segregation distribution characteristics during solid-air dendrite motion induced by solution convection, a partially saturated bounce-back lattice Boltzmann coupled non-isothermal phase field method (PSLBM-PF) is proposed in this study. The partially saturated bounce-back lattice Boltzmann method (PSLBM) is employed to calculate the flow field and the forces and moments between the fluid and solid phases, and the phase field method (PF) is utilized for the computation of the growth of solid-air dendrites and the distribution of solute segregation. The motion of solid-air dendrites is determined by the momentum equation. The accuracy of the calculated interaction forces between fluid and solid phases was validated through the sedimentation process of circular particles in the liquid, and the capability of the present model to preserve the shape during solid-air dendrite motion (translational and rotational) was confirmed. Subsequently, this model was employed to investigate the growth and sedimentation motion of solid-air dendrites with different growth orientations in the solution. During dendrite settlement, the growth of the lower dendrite arms is promoted, while the settlement velocity and the solid phase fraction are almost unaffected by the growth orientation. Then, the differences in morphology evolution and solute distribution under conditions of forced convection for both stationary and motion are comparatively investigated, utilizing the free growth of solid-air dendrites under convection-free conditions as a reference. Finally, the model was utilized to study the growth of individual solid-air dendrites as well as translational and rotational motion under the action of shear flow. The presence of convection significantly alters the solute and temperature distributions at the solid-liquid interface, thereby influencing the dendrite growth process. The simulation results indicate that this model can predict the solid-air dendrites microstructural growth evolution and oxygen solute segregation distribution accompanying the convection and motion.

Early effectiveness of arthroscopic tri-anchor double-pulley suture-bridge repair of medium-size supraspinatus tendon tears

To explore the early effectiveness of arthroscopic tri-anchor double-pulley suture-bridge in treatment of medium-size supraspinatus tendon tears. Between December 2020 and January 2023, 40 patients with medium-size supraspinatus tendon tears were treated with arthroscopic tri-anchor double-pulley suture-bridge. There were 18 males and 22 females, with an average age of 62.6 years (mean, 45-73 years). Among them, 17 patients had trauma history. The main clinical symptom was shoulder pain with hug resistance test (+). The interval from symptom onset to operation was 10.7 months on average (range, 3-36 months). Visual analogue scale (VAS) score, University of California Los Angeles (UCLA) score, American Shoulder and Elbow Surgeons (ASES) score, and shoulder range of motion (ROM) of forward flexion, abduction, and external rotation were used to evaluate shoulder function. MRI was performed to assess the structural integrity and tension of reattached tendon. Patient satisfactions were calculated at last follow-up. All incisions healed by first intention, no complications such as incision infection or nerve injury occurred. All patients were followed up 12-37 months (mean, 18.2 months). At 12 months after operation, VAS score, UCLA score, and ASES score significantly improved when compared with the preoperative scores ( P<0.05). At 3 and 12 months after operation, the ROM of external rotation significantly improved when compared with preoperative one ( P<0.05), and further improved at 12 months after operation ( P<0.05). However, the ROMs of abduction and forward flexion did not improve at 3 months after operation when compared with those before operation ( P>0.05), but significantly improved at 12 months after operation ( P<0.05). Twenty-six patients underwent MRI at 3-6 months, of which 23 patients possessed intact structural integrity, good tendon tension, and tendon healing; 3 patients underwent tendon re-tear. The self-rated satisfaction rate was 92.5% at last follow-up. Arthroscopic tri-anchor double-pulley suture-bridge in treatment of medium-size supraspinatus tendon tears can maximize the tendon-bone contact area, obtain satisfied early effectiveness with high satisfaction rate and low incidence of tendon re-tear. However, the function of abduction is limited at 3 months after operation, and patients need to adhere to rehabilitation training to further improve the joint activity.

A computational model of motion sickness dynamics during passive self-motion in the dark.

Predicting the time course of motion sickness symptoms enables the evaluation of provocative stimuli and the development of countermeasures for reducing symptom severity. In pursuit of this goal, we present an Observer-driven model of motion sickness for passive motions in the dark. Constructed in two stages, this model predicts motion sickness symptoms by bridging sensory conflict (i.e., differences between actual and expected sensory signals) arising from the Observer model of spatial orientation perception (stage 1) to Oman's model of motion sickness symptom dynamics (stage 2; presented in 1982 and 1990) through a proposed "Normalized Innovation Squared" statistic. The model outputs the expected temporal development of human motion sickness symptom magnitudes (mapped to the Misery Scale) at a population level, due to arbitrary, 6-degree-of-freedom, self-motion stimuli. We trained model parameters using individual subject responses collected during fore-aft translations and off-vertical axis of rotation motions. Improving on prior efforts, we only used datasets with experimental conditions congruent with the perceptual stage (i.e., adequately provided passive motions without visual cues) to inform the model. We assessed model performance by predicting an unseen validation dataset, producing a Q2 value of 0.91. Demonstrating this model's broad applicability, we formulate predictions for a host of stimuli, including translations, earth-vertical rotations, and altered gravity, and we provide our implementation for other users. Finally, to guide future research efforts, we suggest how to rigorously advance this model (e.g., incorporating visual cues, active motion, responses to motion of different frequency, etc.).

Coherent detection of the rotational Doppler effect measurement based on triple Fourier transform.

In recent years, the rotational Doppler effect (RDE) has been widely used in rotational motion measurement. However, the performance of existing detection systems based on the RDE are generally limited by the drastic reduction of signal-to-noise ratio (SNR) due to the influence of atmospheric turbulence, partial obscuration of the vortex beam (VB) during propagation, and misalignment between the optical axis of VB and the rotational axis of the object, which poses a challenge for practical applications. In this paper, we proposed a coherent detection method of the RDE measurement based on triple Fourier transform. First, the weak RDE signal in backscattered light is amplified by using the balanced homodyne detection method, and the amplified signal still retains the same characteristic of severe broadening in the frequency domain as the original signal. Furthermore, we proposed the triple Fourier transform to extract the broadened RDE frequency shift signal after the coherent amplification. The proposed method significantly improves the SNR of RDE measurement and facilitates the accurate extraction of rotational speed, which helps to further improve the RDE detection range and promote its practical application.

Utricular Dysfunction and Hearing Impairment Affect Spatial Navigation in Community-Dwelling Healthy Adults: Analysis from the Baltimore Longitudinal Study of Aging

Plain Language SummarySpatial navigation, the ability to move through one’s environment, is a complex skill utilized in everyday life. The effects of specific balance and hearing deficits on spatial navigation have not been extensively studied. Thus, we analyzed data from 182 participants in the Baltimore Longitudinal Study of Aging who completed balance, hearing, and spatial navigation tests to determine if hearing impairment may adversely affect spatial navigation and if combined deficits in balance and hearing further impair navigation ability. Our analyses accounted for the confounding effects of age, sex, and cognition on aspects of spatial navigation performance. We found that deficits in hearing and in the balance organ that senses horizontal translational movements were associated with worse performance on spatial navigation. However, deficits in the balance organs that sense vertical translational movements and horizontal rotational movements were not associated with worse spatial navigation ability. Surprisingly, we found that those with combined balance and hearing deficits did not perform significantly worse on spatial navigation than those with deficits in either balance or hearing alone. We believe that the abnormal function of the horizontal translational movement sensors likely explains the gait disorientation experienced by persons with inner ear problems. Additionally, we propose that hearing deficits impede one’s ability to use real-time sound cues to guide navigation. Many of our participants had mild deficits; thus, further research on the effects of more severe balance and hearing deficits on spatial navigation is needed to gain a better understanding of how different sensory inputs contribute to spatial navigation ability.

Research on a rotary piezoelectric energy harvester based on movable magnets

A hybrid energy harvester (HEH) is designed using a movable magnet to harvest the mechanical energy for rotational motion. One movement of the movable magnet can generate electricity from piezoelectric nanogenerators (PENG) and electromagnetic generators (EMG), improving the energy conversion efficiency of HEH. The main factors affecting the motion characteristics of active magnets (number of magnets and magnet diameter) are illustrated through theoretical modeling and simulation, and the voltage characteristics of EMG and vibration characteristics of PENG are analyzed. According to the main factors affecting the motion characteristics, the experimental testing system was set up. The results show that the voltage of PENG and EMG can be up to 6.55 V and 1.37 V, respectively as the magnet diameter is 10 mm and the number of magnets is 5. The maximum power of PENG is 2.4 mW at 30 kΩ, and the power of EMG is 0.49 mW at 4 kΩ. The application experiment also proves the feasibility of the practical application of R-PEH, which provides a new solution for the research of hybrid energy harvesting systems.

Guidance and Control for Safe Contactless Plume Impingement Operations to Detumble an Uncooperative Spacecraft

In recent years, the interest in proximity operations to uncooperative and non-collaborative objects has been growing and and demanding for specific technology advances to tackle these challenging cases of in-orbit servicing and removal missions. Indeed, these architectures hold a crucial role in guaranteeing future sustainable and efficient space operations. One of the main challenges of conducting robotic operations with a chaser in close proximity to an uncooperative object stems from its rotational motion. A tumbling motion of a large target object may require a costly and complex synchronisation of the servicer relative trajectory to the capture point and hinder the safety of operations due to rotating appendages. In this paper, the plume impingement strategy is employed to control the target’s tumbling motion in a contactless fashion, thus guaranteeing feasible approach and capture operations. Specifically, guidance and control strategies to be employed during this delicate and complex operation are devised, focusing on improving the safety of the trajectory while maximising the efficiency of the impingement effect during proximity flight. Simulations discuss the detumbling of a satellite of a large constellation, critically comparing delta-v cost, trajectory safety and overall time of operations.

Does having an external focus in immersive virtual reality increase range of motion in people with neck pain?

BackgroundWhen instructing exercises to improve Range of Motion (ROM), clinicians often create an internal focus of attention, while motor performance may improve more when using an external focus. Objectives: Using Virtual Reality (VR), we investigated the effect of tasks with an internal and external focus on maximal ROM in people with neck pain and explored whether this effect was associated with fear of movement. MethodIn this cross-over experimental design study, the cervical ROM of 54 participants was measured while performing a target-seeking exercise in a VR-environment (external focus task) and during three maximal rotation and flexion-extension movements with the VR-headset on, without signal (internal focus task). The main statistical analysis included two dependent T-tests. Pearson correlation coefficients were calculated to investigate whether the differences in ROM in both conditions were correlated to fear of movement. ResultsMaximal neck rotation was larger in the external focus condition than in the internal focus condition (mean difference: 26.4°, 95% CI [20.6, 32.3]; p < 0.001, d = 1.24). However, there was a difference favouring the internal focus condition for flexion-extension (mean difference: 8.2°, 95% CI [-14.9, −1.5]; p = 0.018, d = 0.33). The variability in ROM was not explained by variability in fear of movement (for all correlations p ≥ 0.197). ConclusionAn external focus resulted in a larger range of rotation, but our flexion-extension findings suggest that the task has to be specific to elicit such an effect. Further research, using a task that sufficiently elicits movement in all directions, is needed to determine the value of an external focus during exercise.

Comparison of kinematics and joint moments calculations for lower limbs during gait using markerless and marker-based motion capture.

Objective: This study aimed at quantifying the difference in kinematic and joint moments calculation for lower limbs during gait utilizing a markerless motion system (TsingVA Technology, Beijing, China) in comparison to values estimated using a marker-based motion capture system (Nokov Motion Capture System, Beijing, China). Methods: Sixteen healthy participants were recruited for the study. The kinematic data of the lower limb during walking were acquired simultaneously based on the markerless motion capture system (120Hz) and the marker-based motion capture system (120Hz). The ground reaction force was recorded synchronously using a force platform (1,200Hz). The kinematic and force data were input into Visual3D for inverse dynamics calculations. Results: The difference in the lower limb joint center position between the two systems was the least at the ankle joint in the posterior/anterior direction, with the mean absolute deviation (MAD) of 0.74cm. The least difference in measuring lower limb angles between the two systems was found in flexion/extension movement, and the greatest difference was found in internal/external rotation movement. The coefficient of multiple correlations (CMC) of the lower limb three joint moments for both systems exceeded or equaled 0.75, except for the ad/abduction of the knee and ankle. All the Root Mean Squared Deviation (RMSD) of the lower limb joint moment are below 18N·m. Conclusion: The markerless motion capture system and marker-based motion capture system showed a high similarity in kinematics and inverse dynamic calculation for lower limbs during gait in the sagittal plane. However, it should be noted that there is a notable deviation in ad/abduction moments at the knee and ankle.

Quantum states resembling classical periodic trajectories in mesoscopic elliptic billiards.

A quantum wave function with localization on classical periodic orbits in a mesoscopic elliptic billiard has been achieved by appropriately superposing nearly degenerate eigenstates expressed as products of Mathieu functions. We analyze and discuss the rotational and librational regimes of motion in the elliptic billiard. Simplified line equationscorresponding to the classical trajectories can be extracted from the quantum state as an integral equationinvolving angular Mathieu functions. The phase factors appearing in the integrals are connected to the classical initial positions and velocity components. We analyze the probability current density, phase maps, and vortex distributions of the periodic orbit quantum states for both rotational and librational motions; furthermore, they may represent traveling and standing trajectories inside the elliptic billiard.

Kinematic analysis of an unrestrained passenger in an autonomous vehicle during emergency braking.

Analyzing human body movement is a critical aspect of biomechanical studies in road safety. While most studies have traditionally focused on assessing the head-neck system due to the restraint provided by seat belts, it is essential to examine the entire pelvis-thorax-head kinematic chain when these body regions are free to move. The absence of restraint systems is prevalent in public transport and is also being considered for future integration into autonomous vehicles operating at low speeds. This article presents an experimental study examining the movement of the pelvis, thorax and head of 18 passengers seated without seat belts during emergency braking in an autonomous bus. The movement was recorded using a video analysis system capturing 100 frames per second. Reflective markers were placed on the knee, pelvis, lumbar region, thorax, neck and head, enabling precise measurement of the movement of each body segment and the joints of the lumbar and cervical spine. Various kinematic variables, including angles, displacements, angular velocities and accelerations, were measured. The results delineate distinct phases of body movement during braking and elucidate the coordination and sequentiality of pelvis, thorax and head rotation. Additionally, the study reveals correlations between pelvic rotation, lumbar flexion, and vertical trunk movement, shedding light on their potential impact on neck compression. Notably, it is observed that the elevation of the C7 vertebra is more closely linked to pelvic tilt than lumbar flexion. Furthermore, the study identifies that the maximum angular acceleration of the head and the maximum tangential force occur during the trunk's rebound against the seatback once the vehicle comes to a complete stop. However, these forces are found to be insufficient to cause neck injury. While this study serves as a preliminary investigation, its findings underscore the need to incorporate complete trunk kinematics, particularly of the pelvis, into braking and impact studies, rather than solely focusing on the head-neck system, as is common in most research endeavors.