Motion In Space Research Articles

PMSTD-Net: A Neural Prediction Network for Perceiving Multi-Scale Spatiotemporal Dynamics.

With the continuous advancement of sensing technology, applying large amounts of sensor data to practical prediction processes using artificial intelligence methods has become a developmental direction. In sensing images and remote sensing meteorological data, the dynamic changes in the prediction targets relative to their background information often exhibit more significant dynamic characteristics. Previous prediction methods did not specifically analyze and study the dynamic change information of prediction targets at spatiotemporal multi-scale. Therefore, this paper proposes a neural prediction network based on perceptual multi-scale spatiotemporal dynamic changes (PMSTD-Net). By designing Multi-Scale Space Motion Change Attention Unit (MCAU) to perceive the local situation and spatial displacement dynamic features of prediction targets at different scales, attention is ensured on capturing the dynamic information in their spatial dimensions adequately. On this basis, this paper proposes Multi-Scale Spatiotemporal Evolution Attention (MSEA) unit, which further integrates the spatial change features perceived by MCAU units in higher channel dimensions, and learns the spatiotemporal evolution characteristics at different scales, effectively predicting the dynamic characteristics and regularities of targets in sensor information.Through experiments on spatiotemporal prediction standard datasets such as Moving MNIST, video prediction dataset KTH, and Human3.6m, PMSTD-Net demonstrates prediction performance surpassing previous methods. We construct the GPM satellite remote sensing precipitation dataset, demonstrating the network's advantages in perceiving multi-scale spatiotemporal dynamic changes in remote sensing meteorological data. Finally, through extensive ablation experiments, the performance of each module in PMSTD-Net is thoroughly validated.

Numerical Simulation of Folding Tail Aeroelasticity Based on the CFD/CSD Coupling Method

This paper presents a CFD/CSD coupling method for aeroelastic simulation of folding tail morphing aircraft. The unsteady aerodynamic analysis is based on an in-house computational fluid dynamics (CFD) solver for the Euler equations, and emphasis is made on developing an efficient dynamic mesh method for the tail’s hybrid fold motion/elastic vibration deformation. The structural dynamic analysis is based on the computational structural dynamics (CSD) technique for solving the structural equation of motion in modal space. The aeroelastic coupling was achieved through successive iterations of CFD and CSD computations in the time domain. An adaptive multi-functional morphing aircraft allowing tail fold motion was selected to be studied. By using the developed method, aeroelastic simulation and mechanism analysis for fixed configurations at different folding angles and for variable configurations during the folding process were performed. The influence of folding rate on tail aeroelasticity and its influence mechanism were also analyzed.

Focused Update on Migraine and Vertigo Comorbidity.

To provide an update on comorbidity of vestibular symptoms and migraine. Multisensory processing and integration is a key concept for understanding mixed presentation of migraine and vestibular symptoms. Here, we discuss how vestibular migraine should be distinguished from a secondary migraine phenomenon in which migraine symptoms may coincide with or triggered by another vestibular disorder. We also have some updates on the diagnostic criteria of vestibular migraine, its pathophysiology, and common approaches used for its treatment. As a common clinical presentation of migraine and vestibular symptoms, vestibular migraine should be distinguished from a secondary migraine phenomenon, in which migraine symptoms may be triggered by or coincide with another vestibular disorder. Recent experimental evidence suggests vestibular symptoms in vestibular migraine are linked to multisensory mechanisms that control body motion and orientation in space.

Candidate Members of the VMP/EMP Disk System of the Galaxy from the SkyMapper and SAGES Surveys

Photometric stellar surveys now cover a large fraction of the sky, probe to fainter magnitudes than large-scale spectroscopic surveys, and are relatively free from the target selection biases often associated with such studies. Photometric-metallicity estimates that include narrow/medium-band filters can achieve comparable accuracy and precision to existing low-resolution spectroscopic surveys such as Sloan Digital Sky Survey/SEGUE and LAMOST. Here we report on an effort to identify likely members of the Galactic disk system among the very metal-poor (VMP; [Fe/H] ≤ −2) and extremely metal-poor (EMP; [Fe/H] ≤ −3) stars. Our analysis is based on an initial sample of ∼11.5 million stars with full space motions selected from the SkyMapper Southern Survey (SMSS) and Stellar Abundance and Galactic Evolution Survey (SAGES). After applying a number of quality cuts to obtain the best available metallicity and dynamical estimates, we analyze a total of ∼5.86 million stars in the combined SMSS/SAGES sample. We employ two techniques that, depending on the method, identify between 876 and 1476 VMP stars (6.9%−11.7% of all VMP stars) and between 40 and 59 EMP stars (12.4%−18.3% of all EMP stars) that appear to be members of the Galactic disk system on highly prograde orbits (v ϕ > 150 km s−1). The total number of candidate VMP/EMP disklike stars is 1496, the majority of which have low orbital eccentricities, ecc ≤ 0.4; many have ecc ≤ 0.2. The large fractions of VMP/EMP stars associated with the Milky Way disk system strongly suggest the presence of an early-forming “primordial” disk.

Design and Verification of Piano Playing Assisted Hand Exoskeleton Robot.

Finger technique is a crucial aspect of piano learning, and hand exoskeleton mechanisms effectively assist novice piano players in maintaining correct finger technique consistently. Addressing current issues with exoskeleton robots, such as the inability to provide continuous correction of finger technique and their considerable weight, a novel hand exoskeleton robot has been developed to enhance finger technique through continuous correction and reduced weight. Initial data are gathered using finger joint angle sensors to analyze movements during piano playing, focusing on the trajectory and angular velocity of key strikes. This analysis informs the design of a 6-bar double-closed-loop mechanism with an end equivalent sliding pair, using analytical methods to establish the relationship between motor extension and input rod rotation. Simulation studies assess the exoskeleton's motion space and dynamics, confirming its capability to meet structural and functional demands for accurate key striking. Prototype testing validates the exoskeleton's ability to maintain correct finger positioning and mimic natural strike speeds, thus improving playing technique while ensuring comfort and safety.

Insights into the mechanisms of optical cavity-modified ground-state chemical reactions

In this work, we systematically investigate the mechanisms underlying the rate modification of ground-state chemical reactions in an optical cavity under vibrational strong-coupling conditions. We employ a symmetric double-well description of the molecular potential energy surface and a numerically exact open quantum system approach—the hierarchical equations of motion in twin space with a matrix product state solver. Our results predict the existence of multiple peaks in the photon frequency-dependent rate profile for a strongly anharmonic molecular system with multiple vibrational transition energies. The emergence of a new peak in the rate profile is attributed to the opening of an intramolecular reaction pathway, energetically fueled by the cavity photon bath through a resonant cavity mode. The peak intensity is determined jointly by kinetic factors. Going beyond the single-molecule limit, we examine the effects of the collective coupling of two molecules to the cavity. We find that when two identical molecules are simultaneously coupled to the same resonant cavity mode, the reaction rate is further increased. This additional increase is associated with the activation of a cavity-induced intermolecular reaction channel. Furthermore, the rate modification due to these cavity-promoted reaction pathways remains unaffected, regardless of whether the molecular dipole moments are aligned in the same or opposite direction as the light polarization.

Robust adaptive safety control of uncertain nonlinear systems and its application to differential robots

AbstractThis article focuses on the problem of robust adaptive safety control of a class of nonlinear systems with parametric uncertainties. Two novel definitions, that is, robust adaptive control Lyapunov function (RACLF) and robust adaptive control barrier function (RACBF) are introduced in this article. Also, an estimation of unknown parameters is obtained based on multiple identification models, state predictors and a logic switching mechanism. The switching mechanism plays a vital role in enhancing the transient properties of nonlinear systems. Meanwhile, a safe motion framework for differential robots is provided based on the existence of parametric uncertainties in RACLF and RACBF, and a safe and stable controller is obtained by solving quadratic programming. Finally, simulation results of differential robot capable of safe motion in space are presented to verify the validity of the design method.

Enhancing Strategy of Triboelectric Nanogenerator via Origami Pattern by Harvesting Mechanical Motion and Wind Flow

Triboelectric nanogenerators (TENGs) are promising energy-harvesting devices that generate electricity from mechanical energy. However, the electrical outputs of typical TENGs are limited because of the fundamental mechanism by which TENGs require a certain amount of space for contact-separation motion. Therefore, we developed an origami-based vertical/fluttering hybrid TENG (OVFH-TENG), which is the innovative structure that can generate electricity from both vertical movement and wind flow which is generated by vertical movement. It consists of a vertical TENG and a fluttering TENG where vertical TENGs can generate electricity and wind flow from mechanical input and the fluttering TENGs can generate electricity from the wind flow which is generated by its own operation process. Thus, OVFH-TENG can effectively harvest energy from vertical contact and fluttering motions with a single input. The optimized OVFH-TENG generated a 34.7% higher output than the general contact-separation TENG. Finally, the OVFH-TENG was able to light 180 LEDs, which was not possible with a general contact-separation TENG.

Static characteristics of a biomimetic robot module driven by water hydraulic artificial muscles resisted with helical spring

Soft modular biomimetic robots, driven by flexible actuators, are extensively used in various fields due to their excellent flexibility, environmental adaptability, and isomorphism. However, existing flexible modules typically possess no more than two degrees of freedom for structural limitations. This paper proposes a biomimetic robot module supported by a spring and actuated by water hydraulic artificial muscles (WHAMs). Combining the mechanical properties of WHAMs and spring, the static model of the soft module was established by force balance method. Moreover, the contraction force coefficient and contraction ratio coefficient of WHAMs were identified through the static characteristics test. The rod length coefficient and stress coefficient of the spring were also identified through the spring bending test. The errors between the experimental results and the model are analyzed and discussed, uncovering the main reasons. The influence of spring pre-compression, spring elasticity coefficient, initial working pressure of WHAM, and the installation distance of WHAM on the motion space of module were analyzed and discussed. This work serves as a guide for the structural design of flexible modules to meet specific requirements and lays the foundation for future research on integrated flexible biomimetic robots driven by WHAMs.

A spatial 3-DOF piezoelectric robot and its speed-up trajectory based on improved stick-slip principle

Piezoelectric robots have been proven to be suitable for high-precision, cross-scale micro-nano manipulation due to their nanometre resolution and high flexibility. To make up for the limited stroke of micro-nano positioning platforms, a spatial three-degrees-of-freedom (3-DOF) piezoelectric robot is proposed in this study to enable three-dimensional micro-nano manipulation of objects. The robot utilizes the deformation of the piezoelectric stack as the source of displacement. It is comprised of a parallel compliant mechanism and a guided compliant mechanism in series, resulting in a compact robot body. The robot is capable of linear displacement in x-, y- and z-axes. The stiffness of the guided compliant mechanism is calculated using theoretical modeling and compared with the finite element simulation results, with a deviation of less than 5.6% verifying the accuracy of the model. The robot operates using two motion principles: the direct drive principle, which has a resolution of 16, 15, and 11 nm in x-, y- and z-axes, and a motion space of 13×11×7 μm3; and the improved stick-slip principle, which has a theoretical infinite stroke and a maximum speed of 4.2 and 3.9 mm/s in x- and y-axes. The speed of the improved stick-slip principle is 42% higher than that of the traditional stick-slip principle in x- and y-axes. The robot has a spatial 3-DOF, nanometre resolution, millimeter speed, and can carry more than 500 g.

Fiber optic photoacoustic gas sensor enhanced by multi-pass cell with overlapping phantom spots

A neotype fiber optic photoacoustic gas sensor with overlapping phantom spots based multi-pass is proposed, which greatly improves the reflection times and the length of gas absorption path. Moreover, the detection accuracy of photoacoustic spectroscopy (PAS) system is independent of the optical interference effect caused by overlapping spots, which is different from tunable diode laser absorption spectroscopy (TDLAS) technology. A mathematical model including light beam motion space, spot size and overlap discrimination of multi-pass structure based on overlapping phantom spots is established. The incident light is reflected up to dozens of times in the resonator with a diameter of only 8 mm. The emergent light does not need to converge on a photodetector, which reduces the difficulty of adjusting the optical path and promotes the realization of overlapping phantom spots. The experimental results show that the amplitude of photoacoustic signal is improved by about 40 times compared with the single spot structure. Appling high-sensitivity optical fiber cantilever to detect the sound pressure signal. The detection limit of C2H2 gas reaches 8.2 ppt. The normalized noise equivalent absorption (NNEA) coefficient of the gas sensor is achieved to be 9.3×10−11 cm−1WHz−1/2.

Reactive collision-free motion generation in joint space via dynamical systems and sampling-based MPC

Dynamical system (DS) based motion planning offers collision-free motion, with closed-loop reactivity thanks to their analytical expression. It ensures that obstacles are not penetrated by reshaping a nominal DS through matrix modulation, which is constructed using continuously differentiable obstacle representations. However, state-of-the-art approaches may suffer from local minima induced by non-convex obstacles, thus failing to scale to complex, high-dimensional joint spaces. On the other hand, sampling-based Model Predictive Control (MPC) techniques provide feasible collision-free paths in joint-space, yet are limited to quasi-reactive scenarios due to computational complexity that grows cubically with space dimensionality and horizon length. To control the robot in the cluttered environment with moving obstacles, and to generate feasible and highly reactive collision-free motion in robots’ joint space, we present an approach for modulating joint-space DS using sampling-based MPC. Specifically, a nominal DS representing an unconstrained desired joint space motion to a target is locally deflected with obstacle-tangential velocity components navigating the robot around obstacles and avoiding local minima. Such tangential velocity components are constructed from receding horizon collision-free paths generated asynchronously by the sampling-based MPC. Notably, the MPC is not required to run constantly, but only activated when the local minima is detected. The approach is validated in simulation and real-world experiments on a 7-DoF robot demonstrating the capability of avoiding concave obstacles, while maintaining local attractor stability in both quasi-static and highly dynamic cluttered environments.

Frequency and Clinical Features of Space Headache Experienced by Astronauts During Long-Haul Space Flights.

Few anecdotal cases and 1 small retrospective study during short-duration space missions suggest that headache may occur early in flight, as part of the space motion syndrome. Whether headaches may also occur at later stages of space flights is unknown. We aimed to prospectively characterize the incidence, timing, clinical features, and management of space headaches during long-duration flights. We prospectively evaluated the occurrence, characteristics, and evolution of space headaches and the effects of treatment and countermeasures during long-haul flights with onboard questionnaires and correlated them with prevailing temperature, pressure, and ambient O2 and CO2 levels, measured within the International Space Station. In addition, we analyzed retrospective headache data from a different astronaut cohort. Headache data were reported using descriptive statistics and correlation data with intraindividual logistic regression models. Astronauts were included through (inter)national aerospace organizations. In the prospective study, 22/24 (91.7%) astronauts (mean ± SD age: 46.6 ± 6.5 years, 95.8% male) experienced ≥1 episode of headache during a total of 3,596 space days. A total of 378 episodes were reported (median 9; range 1-128) with detailed information on 189. Phenotypically, 170/189 (89.9%) episodes were tension-type headache (TTH) and 19/189 (10.1%) were migraine. Episodes in the first week differed from those in later periods in terms of phenotype (migraine 12/51 [23.5%] vs 7/138 [5.1%]; TTH 39/51 [86.5%] vs 131/138 [94.9%]; overall p = 0.0002) and accompanying symptoms: nausea: 17.6% vs 6.9%, p = 0.05; vomiting: 9.8% vs 0.7%, p = 0.005; nasal congestion: 52.9% vs 29.7%, p = 0.004; facial edema: 41.2% vs 1.4%, p < 0.001; and duration (p = 0.001). Severity and treatments were similar: acute antiheadache medication: 55.6%; other medication: 22.4%; and alternative treatments: 41.1%. Headache occurrence was not associated with temperature or ambient pressure/levels of O2 and CO2 (all p > 0.05). In the retrospective study, 23/42 (54.8%) astronauts (43.5 ± 7.2 years, 90.5% male) reported experiencing ≥1 headache episode during mission. Nasal congestion was the most common (8/33; 24.2%) accompanying symptom. Seventeen of 42 astronauts have been previously described. Astronauts during space flights frequently experience headaches. These most often have characteristics of TTHs but sometimes have migrainous features, particularly during the first week of flight in astronauts without a history of recurrent headaches before or after the space flight.

Three-dimensional measurement method of binary particle collisions under dry and wet conditions

The description, calculation and design of solids processes, such as fluidization, pneumatic conveying or mixing, require knowledge of collision dynamics between particles and apparatus walls or interparticle collisions without, but often also with the presence of an additional liquid. For the study of such dry and wet interparticle collisions, an experimental setup is presented that allows the performance of dry or wet free binary collisions of spherical particles down to a minimum diameter of 1 mm. The recording of the particle motions in all three spatial directions is provided by two synchronized highspeed cameras. Methods and algorithms are presented for analyzing the translational and rotational motion in three-dimensional space, as well as for measuring the amount of liquid on the particles in the case of wet collisions. Motion data from dry collisions between equal sized and unequal sized spherical particles are compared with a three-parameter collision model. In addition, a first series of measurements of wetted collisions is used to compare the collision dynamics with dry collisions.

IHUVS: Infinite Homography-Based Uncalibrated Methodology for Robotic Visual Servoing

The construction of task functions in robotic manipulation is of paramount importance for uncalibrated visual servoing. The existing methods generally use image information as control variables and estimate the image Jacobian matrix online, thus possessing issues relating to convergence, and image Jacobian matrix singularities. Therefore, this work proposes a novel methodology dubbed infinite homography-based uncalibrated visual servoing (IHUVS), in which the visual control of the robot end-effector pose is decomposed into its rotational and translational components. The corresponding rotational controller designs the visual servoing task function using the relationship between the infinite homography matrix and rotation matrix, and employs the Kronecker product to derive linear equations for rotational control, as well as to conduct the associated task error analysis. Meanwhile, the translational controller utilizes Kalman filtering for online estimation of the Jacobian matrix that is required by the proportional control scheme. The robot end-effector motion in Cartesian space is generated via the IHUVS method, without knowing the camera's intrinsic parameters and the robot hand-eye relationship. A simulation analysis is carried out to assess the algorithm's numerical performance, while robotic visual servoing experiments are also conducted to verify the accuracy and efficacy of the proposed IHUVS method.

Influence of N,N′‐ethylene bis oleamide on the flowability of the acrylonitrile‐butadiene‐styrene resin and lubrication mechanism

AbstractAs a high‐performance engineering plastic, the acrylonitrile‐butadiene‐styrene (ABS) resin possesses excellent heat resistance, chemical resistance, and toughness. However, there is a lack of flow properties of the ABS resin for many processing operations. With the aim of enhancing the flowability of the ABS resin, the effect of N,N′‐ethylene bis oleamide (EBO) as a new lubricant on the melt flow rate (MFR), torque value, and rheological behavior of the ABS resin was investigated. The result showed the MFR of the ABS resin with 2.0 wt% EBO was 22.1 g/10 min, which was improved by 49% compared with the pure ABS resin (14.8 g/10 min). The torque value of the ABS resin, including 2.0 wt% EBO (1.69 N m) was lower than that of the pure ABS resin (2.03 N m). The rheological study further indicated that EBO can reduce the complex viscosity of the ABS resin. The above results indicated that EBO was an effective lubricant for the ABS resin. A possible lubrication mechanism was proposed based on the consequences of the rotational rheometry, dynamic mechanical analysis, and molecular dynamics simulation. EBO decreased the entanglement density of the polystyrene‐acrylonitrile (SAN) molecular chains and increased the mobility of the SAN molecular chain segments. On the other hand, EBO increased the free space of motion of the SAN molecular chain segments due to the free‐volume effect thereby increasing the mean square displacement of the system. This work will provide a new way to achieve the high‐flow ABS resin and provide new insights into the lubrication mechanism of lubricants in the ABS resin thereby expanding the applications of the ABS resin.

Kinematic Investigation of Healthy, Arthritic, and Postsurgery Thumbs: Is the Metacarpophalangeal Joint the Gateway to Carpometacarpal Arthritis?

The thumb carpometacarpal (CMC) joint is one of the most likely joints to develop osteoarthritis (OA). If conservative treatments fail to alleviate symptoms, surgery may be pursued. Kinematic outcomes of CMC surgery techniques have been described, but current tools have limitations in capturing motion abilities. The goals of this study were (1) develop a new and robust set of kinematic outcome measures, and apply them to (2) a cohort of younger and older control individuals without CMC OA to determine age and sex-related changes, and (3) a cohort of participants with CMC OA before, 3 months, and 6 months after undergoing thumb ligament reconstruction with tendon interposition surgery to detect the impacts of surgery. 52 (26 males, 26 females) control and 18 (3 males, 15 females) surgical participants were tested. Kinematics were investigated using motion capture by mapping the three-dimensional motion space of the whole thumb, and two-dimensional motion boundaries of the metacarpal (MC) and proximal phalange (PP). Visual analog pain score was recorded. Older control participants had shifted regions of motion compared to younger participants (p ≤ 0.027), suggesting asymptomatic CMC wear. Control females had 31% more metacarpophalangeal (MCP) motion than control males (p = 0.013), which could alter loading paths through the CMC joint and increase OA risk. Pain at 6 months postsurgery was 72% less than presurgery (p < 0.001), but motion abilities were 20-28% less than presurgery (p ≤ 0.074) and 24-40% less than control participants (p ≤ 0.066). These techniques have the possibility of identifying presymptomatic motion changes, including those at the metacarpophalangeal joint in CMC OA progression.

New Metrics and Dataset for Biological Development Video Generation

Image generative models have advanced in many areas to produce synthetic images of high resolution and detail. This success has enabled its use in the biomedical field, paving the way for the generation of videos showing the biological evolution of its content. Despite the power of generative video models, their use has not yet extended to time-based development, focusing almost exclusively on generating motion in space. This situation is largely due to the lack of specific data sets and metrics to measure the individual quality of videos, particularly when there is no ground truth available for comparison. We propose a new dataset, called GoldenDOT, which tracks the evolution of apples cut in parallel over 10 days, allowing to observe their progress over time while remaining static. In addition, four new metrics are proposed that provide different analyses of the generated videos as a whole and individually. In this paper, the proposed dataset and measures are used to study three state of the art video generative models and their feasibility for video generation with biological development: TemporalGAN (TGANv2), Low Dimensional Video Discriminator GAN (LDVDGAN), and Video Diffusion Model (VDM). Among them, the TGANv2 model has managed to obtain the best results in the vast majority of metrics, including those already known in the state of the art, demonstrating the viability of the new proposed metrics and their congruence with these standard measures.

Ultrasound-Based Noncontrast Microvascular Imaging for Evaluation of Breast Lesions: Imaging Techniques and Review of Diagnostic Criteria.

Vascularity plays a pivotal role in the progression of breast lesions and may be associated with their aggressiveness and likelihood of being malignant. Contrast-enhanced imaging techniques are necessary to evaluate vascularity due to the limited sensitivity of conventional color Doppler techniques, in which motion artifacts are eliminated using wall filters. However, in this process, low-flow signals from small vessels also get removed unintentionally. Advancements in technology have revolutionized the way ultrasound images are generated, resulting in tremendous improvements in Doppler imaging techniques. The new, ultrasound-based noncontrast microvascular imaging techniques overcome the limitations of conventional Doppler, and are highly sensitive for detecting microvessels and low flow. The resultant high Doppler sensitivity leads to detection of vascularity in more breast lesions. It is important for radiologists to understand the imaging principles and the clinical implications of the new techniques, to optimally utilize them and aid correct diagnosis. Angio-PLUS is one such recent advancement, which uses unfocused or plane waves and three-dimensional wall filtering to analyze tissue motion in time, space, and amplitude domains that effectively distinguish between blood flow and tissue. The information is beneficial for assessing the lesion vascularity without using contrast. This article aims to explain the Doppler imaging techniques, their clinical applications, scanning methods, and review the common Doppler-based diagnostic criteria used in the evaluation of breast lesions.

Exit times of totally asymmetric simple exclusion processes.

We address the question of the time needed by N particles, initially located on the first sites of a finite one-dimensional lattice of size L, to exit that lattice when they move according to a TASEP transport model. Using analytical calculations and numerical simulations, we show that when N≪L, the mean exit time of the particles is asymptotically given by T_{N}(L)∼L+β_{N}sqrt[L] for large lattices. Building upon exact results obtained for two particles, we devise an approximate continuous space and time description of the random motion of the particles that provides an analytical recursive relation for the coefficients β_{N}. The results are shown to be in very good agreement with numerical results. This approach sheds some light on the exit dynamics of N particles in the regime where N is finite while the lattice size L→∞. This complements previous asymptotic results obtained by Johansson [Commun. Math. Phys. 209, 437 (2000)0010-361610.1007/s002200050027] in the limit where both N and L tend to infinity while keeping the particle density N/L finite.