Rapid Motion Research Articles

A Real-Time Registration Algorithm of UAV Aerial Images Based on Feature Matching

This study aimed to achieve the accurate and real-time geographic positioning of UAV aerial image targets. We verified a method of registering UAV camera images on a map (with the geographic location) through feature matching. The UAV is usually in rapid motion and involves changes in the camera head, and the map is high-resolution and has sparse features. These reasons make it difficult for the current feature-matching algorithm to accurately register the two (camera image and map) in real time, meaning that there will be a large number of mismatches. To solve this problem, we used the SuperGlue algorithm, which has a better performance, to match the features. The layer and block strategy, combined with the prior data of the UAV, was introduced to improve the accuracy and speed of feature matching, and the matching information obtained between frames was introduced to solve the problem of uneven registration. Here, we propose the concept of updating map features with UAV image features to enhance the robustness and applicability of UAV aerial image and map registration. After numerous experiments, it was proved that the proposed method is feasible and can adapt to the changes in the camera head, environment, etc. The UAV aerial image is stably and accurately registered on the map, and the frame rate reaches 12 frames per second, which provides a basis for the geo-positioning of UAV aerial image targets.

Volume of Fluid Simulations of Heat Transfer in Liquid-Liquid Segmented Flows in Microfluidic channel

This study presents the investigations on the effect of heat transfer on droplet formation in T-type microfluidic channel. Mineral oil acts as a continuous phase, and water acts as a dispersed phase. The Volume of Fluid model is used to investigate the formation of droplets of water in oil in the microchannel. The physical properties of both fluids change with an increase in temperature of dispersed phase, of which the dominant properties are viscosities of fluids and interfacial tension. The parameters such as droplet diameter, distance between two consecutive droplets and detachment time were studied with respect to temperature in the range of 300 K to 325 K. These properties are also studied at different flow rate ratios 0.125, 0.25, and 0.5. The distance between two consecutive droplets was found to decrease with the increase in temperature due to the rapid motion of droplets in the temperature zone. The droplet detachment time also decreases, due to the decrease in interfacial forces which hold the droplets in the dispersed phase. The droplet diameter decreases initially with the increase in temperature, but it was observed that after 320 K the diameter of the droplet increases due to the coalescence of two consecutive droplets downstream in the microchannel. This temperature is reported as a limiting condition for thermally controlled water-in-oil microemulsions.

Robust and Realtime Large Deformation Ultrasound Registration Using End-to-End Differentiable Displacement Optimisation

Image registration for temporal ultrasound sequences can be very beneficial for image-guided diagnostics and interventions. Cooperative human-machine systems that enable seamless assistance for both inexperienced and expert users during ultrasound examinations rely on robust, realtime motion estimation. Yet rapid and irregular motion patterns, varying image contrast and domain shifts in imaging devices pose a severe challenge to conventional realtime registration approaches. While learning-based registration networks have the promise of abstracting relevant features and delivering very fast inference times, they come at the potential risk of limited generalisation and robustness for unseen data; in particular, when trained with limited supervision. In this work, we demonstrate that these issues can be overcome by using end-to-end differentiable displacement optimisation. Our method involves a trainable feature backbone, a correlation layer that evaluates a large range of displacement options simultaneously and a differentiable regularisation module that ensures smooth and plausible deformation. In extensive experiments on public and private ultrasound datasets with very sparse ground truth annotation the method showed better generalisation abilities and overall accuracy than a VoxelMorph network with the same feature backbone, while being two times faster at inference.

Formulation of three‐dimensional, photo‐responsive printing ink: Gold nanorod‐hydrogel nanocomposites and their four‐dimensional structures that respond quickly to stimuli

AbstractInterest in moving from 3D printing to 4D printing, which would enable rapid and precise motion in reaction to a given stimulus, is evolving. Thermally responsive hydrogels are one of the most common types of soft 4D devices. They are capable of changing shape or behavior autonomously in a manner resembling natural movement, and a bio‐inspired soft actuator has been fabricated by combining stimuli‐responsive nanoparticles with 3D printable hydrogels. We formulated and tested an N‐isopropylacrylamide (NIPAm) and polyethylene glycol thiol‐coated gold nanorod (P‐AuNR) hydrogel nanocomposite as an active ink material for use in the fabrication of heat‐sensitive soft actuators for photo‐responsive soft robotic motions. Due to their surface plasmon resonance (SPR), those highly dispersible P‐AuNR was able to absorb near‐infrared (NIR) light and release heat into their surroundings. This system was not immersed in water and reacted quickly and sensitively to NIR exposure. The 3D structure designed and fabricated with these inks was able to deform selectively only in a very localized part in response to non‐contact external stimuli, leading to various types of controlled shape‐morphing.

Harnessing the nonlinear properties of buckling inflatable tubes for complex robotic behaviors

Imparting complex behaviors to soft robots generally entails complex designs and carefully engineered structures. As such, making soft structures with behaviors such as stiffening, bistability and rapid snapping deformations generally requires specialized solutions. This work introduces the use of short inflatable tubes that buckle under compression to realize behaviors such as self-stiffening, bistability and snap-through induced rapid deformations. These inflatable tubes have a nonlinear behavior resulting from these tubes having two stable states, the buckled and unbuckled states, and the complex transition between states which entails a snap-through buckling instability during the buckling transition, and a range of deformation where the tube is bistable as it is stable in either the buckled or unbuckled states. This work shows how the dimensions of the inflatable tubes affect this behavior and proposes a numerical model that can describe the entire cyclic behavior of buckling and unbuckling inflatable tubes. It is then demonstrated how simply connected multiple inflatable tube segments in series can be used to produce complex robotic behaviors. A soft robotic hand is demonstrated that uses the characteristics of unbuckling inflatable tubes for self-stiffening, and a grasping tool capable of slow or rapid motions by making use of the ability of serially connected inflatable tubes to transition from bistability to monostability.

Tectonic landform and paleoseismic events of the easternmost Matano fault in Sulawesi, Indonesia

The 190-km-long Matano fault is a major left-lateral strike-slip fault in Sulawesi, Indonesia that accommodates the rapid westward motion of the Pacific plate relative to the Australian plate. The Matano fault has remained unruptured at least in the past two centuries. The lack of geologic information, such as precise active fault traces, paleoseismic history, and slip rates has been a significant barrier to assessing the seismic hazards of the Matano fault. This paper presents the results of tectonic geomorphic and paleoseismic investigations on the 30 km long easternmost portion of the Matano fault. We identified four geometrical fault segments, documented five surface faulting events, and calculated a surface-rupturing earthquake recurrence interval of 200–470 years and a slip rate of 21 ± 9 mm/yr. The timing of the most recent surface-rupturing earthquake was constrained between 1432 and 1819 CE with an estimated Mw ∼ 7.4 and a probable rupture length of ∼110 km. At least 200 years have passed since the latest faulting event, exceeding the shortest recurrence interval. Thus, the next surface-rupturing earthquake is already due. Integrating our interpretations with results from several published studies clarifies that the Matano fault slips slower than the Palu-Koro fault and connects to the South Sula fault in addition to the Tolo thrust.

Smart free-standing film force-assembled by Ti3C2Tx/CNC with high sensitivity to humidity and near-infrared light

Smart films that can specifically recognize the outer surrounding change and make rapid motion behavior, have presented their potential application in composing intelligent actuators. Herein, we have prepared a hydrophilic free-standing film with the nacre-like layered and directional aligned structure by vacuum-filtering the mixed suspension of Ti3C2Tx nanosheets and cellulose nanocrystal (CNC). Because of the axial Young’s modulus from the oriented arrangement of CNC and Ti3C2Tx, the assembled hybrid film can achieve fast and directed humidity-driven performance, and obtain a specific bending angle by controlling the asymmetric humidity value. Besides, the introduction of CNC also increased the surficial roughness of the hybrid film compared to the pure Ti3C2Tx film, which lengthened the light propagation path. Based on the good photothermal conversion ability of Ti3C2Tx nanosheets around the NIR region, the hybrid film presented ultra-high NIR conversing efficiency that can rapidly heat up to 178.2 °C only under the NIR (808 nm) power of 0.45 W/cm2. Therefore, by depositing thermochromism materials with different color change points, the composited film can realize visual temperature detection. This TC/CNC film with the ability of humidity and NIR sensing will satisfy the further demand for designing smart equipment.

Validation of Fitbit Inspire 2TM Against Polysomnography in Adults Considering Adaptation for Use.

The commercialization of sleep activity tracking devices has made it possible to manage sleep quality at home. However, it is necessary to verify the reliability and accuracy of wearable devices through comparison with polysomnography (PSG), which is the standard for tracking sleep activity. This study aimed to monitor overall sleep activity using Fitbit Inspire 2™ (FBI2) and to evaluate its performance and effectiveness through PSG under the same conditions. We compared the FBI2 and PSG data of nine participants (four male and five female participants; average age, 39 years) without severe sleeping problems. The participants wore FBI2 continuously for 14 days, considering the period of adaptation to the device. FBI2 and PSG sleep data were compared using paired t-tests, Bland-Altman plots, and epoch-by-epoch analysis for 18 samples by pooling data from two replicates. The average values for each sleep stage obtained from FBI2 and PSG showed significant differences in the total sleep time (TST), deep sleep, and rapid eye motion (REM). In the Bland-Altman analysis, TST (P = 0.02), deep sleep (P = 0.05), and REM (P = 0.03) were significantly overstated in FBI2 compared to PSG. In addition, time in bed, sleep efficiency, and wake after sleep onset were overestimated, while light sleep was underestimated. However, these differences were not statistically significant. FBI2 showed a high sensitivity (93.9%) and low specificity (13.1%), with an accuracy of 76%. The sensitivity and specificity of each sleep stage was 54.3% and 62.3%, respectively, for light sleep, 84.8% and 50.1%, respectively, for deep sleep, and 86.4% and 59.1%, respectively for REM sleep. The use of FBI2 as an objective tool for measuring sleep in daily life can be considered appropriate. However, further research is warranted on its application in participants with sleep-wake problems.

Study on the development of thermal characteristics of B4C nanopowder and B4C/water using cryogenic conditions

Deep cryogenic treatment (DCT), a technique that can be utilized on materials down to temperatures as low as −197 ℃, is used in this investigation to cool boron carbide nano-powder. Using the flash technique, researchers compare the thermal diffusivity of untreated and cryogenically treated B4C. Quantifying the thermal conduction of B4C nano-powders is another area of investigation. The results show that DCT significantly improves both the thermal diffusion and conduction of B4C nano-powder, by 34% as well as 47%, respectively. Additionally, the B4C/Water nanofluid's thermal conductivity is calculated. The results demonstrate that aqueous dispersion of both traditionally treated and cryogenically treated B4Cnanopowder improves its thermal conductivity. Because of their rapid Brownian motion, small particles are excellent thermal conductors.

A 5 cm‐Scale Piezoelectric Jetting Agile Underwater Robot

Existing miniature underwater robots, which use electromagnetic actuators or soft actuators, function in shallow waters. However, in the deep sea, the robots face challenges, such as the miniaturization of the pressure protection unit and the driving method for rapid and agile motions. Herein, a jet‐driven method for a high‐pressure underwater environment is proposed by utilizing the high‐frequency vibration of a piezoelectric vibrator. Thereafter, an antihydropressure miniature robot with a body length of less than 5 cm is designed, which can perform the highly agile actions of floating, sinking, hovering, straight driving, and turning under a water pressure of 20 MPa (equal to the pressure under a water depth of 2000 m). A vertical velocity of 2.95 BH/s and a horizontal velocity of 3.22 BL/s are realized by the prototype, and it achieves faster motions than existing miniature underwater robots. Some potential applications have been realized, including small multicorner pipe exploration by carrying a camera, seaweed epidermal cell sampling in designated areas, and large object transportation by swarming, which proves the high maneuverability and agility of the developed robot. These merits make the robot ideal for multitasking operations in narrow environments with high water pressure, such as multiobstacle seabed.

Rapid absolute plate motion changes inferred from high-resolution relative spreading reconstructions: A case study focusing on the South America plate and its Atlantic/Pacific neighbors

The reconstruction of past plate motions relative to a deemed–to–be–fixed hotspot reference frame relies on the sparse occurrence of intraplate volcanism. Consequently, this absolute reference frame often features a temporal resolution that exceeds the rapid kinematic changes observed in plate–to–plate spreading reconstructions, changes recently shown to occur within less than 5 Ma. In this work we put forward an alternative method based on the study of high–resolution relative plate motion data sets. By studying time periods featuring a relatively high probability of plate motion change across multiple spreading ridges, we are able to identify and quantify (likely) changes in absolute plate motion. Specifically, we implement such approach and provide well–defined estimates for the absolute plate motion changes of South America and neighboring plates Nubia, Antarctica, Somalia, North America and Pacific. We find that kinematic changes for all these plates occur between 9 and 5 Ma. For South America, we identify a change also between 14 and 10 Ma. Lastly, we estimate the torque–variations required upon these plates to generate the inferred kinematic changes, which we find to be between ∼5⋅1023 and ∼20⋅1024 N ⋅ m.

A ‘coronal-mass-ejection’ model for flares in Sagittarius A*

ABSTRACT High-resolution near-infrared observations with GRAVITY instrument have revealed rapid orbital motions of a hotspot around Sagittarius A* (Sgr A*), the supermassive black hole in our Galactic Centre, during its three bright flares. The projected distances of the spot to the black hole are measured and seem to increase with time. The values of distance, combined with the measured orbiting time, imply that the spot is rotating with a super-Keplerian velocity. These results are hard to understand if the spot stays within the accretion flow thus provides strong constraints on theoretical models for flares. Previously we have proposed a ‘CME’ model for the flares by analogy with the coronal-mass-ejection model in solar physics. In that model, magnetic reconnection occurred at the surface of the accretion flow results in the formation of flux ropes, which are then ejected out. Energetic electrons accelerated in the current sheet flow into the flux rope region and their radiation is responsible for the flares. In this paper, we apply the model to the interpretation of the GRAVITY results by calculating the dynamics of the ejected flux rope, the evolution of the magnetic field and the energy distribution of accelerated electrons, and the radiation of the system. We find that the model can well explain the observed light curve of the flares, the time-dependent distance, and the super-Keplerian motion of the hotspot. It also explains why the light curve of some flares has double peaks.

Stress accumulation and earthquake activity on the Great Sumatran Fault, Indonesia

The seismically active Sumatra subduction zone has generated some of the largest earthquakes in the instrumental record, and both historical accounts and paleogeodetic coral studies suggest these were large enough to transfer stress to the surrounding region, including the Great Sumatran Fault (GSF). Therefore, evaluating the stress transfer from these large subduction earthquakes could delineate segments of elevated stress along the GSF where large earthquakes may potentially occur. In this study, we investigated eight megathrust earthquakes from 1797 to 2010 and resolved the accumulated Coulomb stress changes onto 18 segments along the GSF. Additionally, we also estimated the rate of tectonic stress on the GSF segments which experienced large earthquakes. We considered two cases, with: (1) no forearc sliver movement, and (2) the forearc sliver movement suggested by recent studies. Based on the historical stress changes of large earthquakes and the increase in tectonic stress rate, we analyzed the time evolution of stress changes on the GSF. The Coulomb stress changes on the GSF due to megathrust earthquakes between 1797 and 1907 increased the Coulomb stress mainly on the southern part of GSF, which was followed by four major GSF events during 1890–1943. The estimation of tectonic stress rates using case (1) produces a low rate of stress accumulation and long recurrence intervals, which would imply that megathrust earthquakes play an important role in promoting the occurrence of GSF earthquakes. When implementing the arc-parallel sliver movement of case (2), the tectonic stress rates are much higher than case (1), with an observed slip rate of 15–16 mm/yr at the GSF consistent with a recurrence interval for full-segment rupture of 100–200 years. The case (2) result suggests that the occurrence of GSF earthquakes is dominantly controlled by the rapid arc-parallel forearc sliver motion. Furthermore, the analysis of the evolution of stress changes with time shows that some segments such as Tripa (North and South), Angkola, Musi and Manna, which have experienced full-segment rupture and are therefore likely locked, appear to have returned to stress levels similar to those prior to previous historical events, suggesting elevated earthquake hazard along these GSF segments.

A Novel Video Stabilization Model With Motion Morphological Component Priors

Video stabilization is the process of improving the video quality by removing annoying fluctuant motion caused by camera jittering. A key issue of a successful solution is the temporal adaptability to motion and the overall robustness with respect to different motion types. However, most previous methods usually produce non-motion adaptive stabilized videos. In other words, under-smoothing in slow motion segments and over-smoothing in rapid motion segments will be produced for complex shaky videos. To overcome these drawbacks, we propose a novel video stabilization approach using a motion morphological component (MMC) decomposition. Specifically, the observed motion is decomposed into three MMCs: low-frequency smoothed (LFS) motion, high-frequency compensatory (HFC) motion, and shaky motion. LFS motion helps to largely stabilize videos, and HFC motion helps to recover missing motion to deal with over-smoothing. Subsequently, we present an MMC-based model to retrieve the desired smoothed motion, in which weighted nuclear norm and autoregression priors are used for LFS motion, while a sparsity prior is adopted for HFC motion. In addition, we design an adaptive weight setting scheme to detect rapid motions and to calculate the optimal weights. Finally, we develop a stabilization algorithm under the Alternating Direction Method of Multipliers (ADMM) framework. Experimental results demonstrate that our method can achieve high-quality results compared with that of other state-of-the-art stabilization methods in terms of robustness and efficiency, both quantitatively and qualitatively.

Small Aerial Target Detection Using Trajectory Hypothesis and Verification

Due to cluttered backgrounds, long-range imaging, rapid relative motion, etc., the detection of small aerial targets remains a challenge. Existing works have illustrated the importance of temporal cues for robust small aerial target detection. However, the strong assumptions about the temporal cues give such methods high computational complexity and weak adaptability. To address this problem, we treat trajectory verification as a classification problem using convolutional neural networks. A novel small aerial target detection method that uses trajectory hypothesis and verification is proposed in this study. First, the IMU assisted inter-frame difference is used to extract target candidates from each single image. Then, based on the continuous and smoothness characteristics of the target trajectory, hypotheses of the required length are generated by linking target candidates in adjacent frames. Finally, the trajectory hypotheses are sent to a trained classification convolution neural network for verification. The detected targets are traced back from the verified trajectory. Furthermore, trajectory merge is conducted to link adjacent trajectory segments. The proposed method can achieve real-time processing. Experimental results on public datasets show that the proposed method performs better than existing methods.

Dynamics of transition dipole moment orientation in representative fluorescent proteins.

Molecules of fluorescent proteins (FPs) exhibit distinct optical directionality. This optical directionality is characterized by transition dipole moments (TDMs), and their orientation with respect to the molecular structures. Although our recent observations of FP crystals allowed us to determine the mean TDM directions with respect to the framework of representative FP molecules, the dynamics of TDM orientations within FP molecules remain to be ascertained. Here we describe the results of our investigations of the dynamics of TDM directions in the fluorescent proteins eGFP, mTurquoise2 and mCherry, through time-resolved fluorescence polarization measurements and microsecond time scale all-atom molecular dynamics (MD) simulations. The investigated FPs exhibit initial fluorescence anisotropies (r0) consistent with significant differences in the orientation of the excitation and emission TDMs. However, based on MD data, we largely attribute this observation to rapid (sub-nanosecond) fluorophore motions within the FP molecular framework. Our results allow improved determinations of orientational distributions of FP molecules by polarization microscopy, as well as more accurate interpretations of fluorescence resonance energy transfer (FRET) observations.

Dynamic effects on ligand field from rapid hydride motion in an iron(ii) dimer with an S = 3 ground state.

Hydride complexes are important in catalysis and in iron-sulfur enzymes like nitrogenase, but the impact of hydride mobility on local iron spin states has been underexplored. We describe studies of a dimeric diiron(ii) hydride complex using X-ray and neutron crystallography, Mössbauer spectroscopy, magnetism, DFT, and ab initio calculations, which give insight into the dynamics and the electronic structure brought about by the hydrides. The two iron sites in the dimer have differing square-planar (intermediate-spin) and tetrahedral (high-spin) iron geometries, which are distinguished only by the hydride positions. These are strongly coupled to give an S total = 3 ground state with substantial magnetic anisotropy, and the merits of both localized and delocalized spin models are discussed. The dynamic nature of the sites is dependent on crystal packing, as shown by changes during a phase transformation that occurs near 160 K. The change in dynamics of the hydride motion leads to insight into its influence on the electronic structure. The accumulated data indicate that the two sites can trade geometries by rotating the hydrides, at a rate that is rapid above the phase transition temperature but slow below it. This small movement of the hydrides causes large changes in the ligand field because they are strong-field ligands. This suggests that hydrides could be useful in catalysis not only due to their reactivity, but also due to their ability to rapidly modulate the local electronic structure and spin states at metal sites.

Design of a Fuel Explosion-Based Chameleon-Like Soft Robot Aided by the Comprehensive Dynamic Model

Soft robotics have advantages over the traditional rigid ones to achieve the bending motion but face with challenges to realize the rapid and long-distance linear motion due to the lack of a suitable actuation system. In this paper, a new explosion-based soft robot is proposed to generate the axial fast extension by the explosion pressure. To support and predict the performance of this explosion-based soft robot, a novel dynamic model is developed by considering the change of working fluid (molecular numbers) and some unavoidable and influential factors in the combustion process. Then, based on the physical prototype, a set of experiments is conducted to test the performance of the explosion-based soft robot in performing the axial extensions, as well as to validate the model proposed in this article. It is found that the novel explosion-based soft robot can achieve rapid axial extension by the developed explosion-based actuation system. The explosion-based soft robot can achieve 41-mm displacement at a fuel mass of 180 mg. In addition, the proposed dynamic model can be validated with an average error of 1.5%. The proposed approach in this study provides a promising solution for future high-power density explosion-based soft robots.

Highly Dynamic Bistable Soft Actuator for Reconfigurable Multimodal Soft Robots (Adv. Mater. Technol. 2/2023)

Soft Robots In article number 2201259, Dinesh K. Patel, Xiaonan Huang, Lining Yao, Carmel Majidi, and co-workers present highly dynamic, robust, and fast-responding bistable actuators for use in soft robotics. These actuators use 3D printed soft materials and shape memory alloy for rapid motions with 1 Hz frequency. They enable the creation of reconfigurable soft robots that transition between walking, swimming, crawling, jumping, and rolling locomotion.

Motion Distortion Elimination for LiDAR-Inertial Odometry Under Rapid Motion Conditions

Motion Distortion Elimination for LiDAR-Inertial Odometry Under Rapid Motion Conditions