Absolute Motion Research Articles

Deep mantle plumes feeding periodic alignments of asthenospheric fingers beneath the central and southern Atlantic Ocean

High-resolution full waveform seismic tomography of the Earth's mantle beneath the south and central Atlantic Ocean brings into focus a series of asthenospheric low shear velocity channels, or "fingers" on both sides of the southern and central mid-Atlantic ridge (MAR), elongated in the direction of absolute plate motion with a spacing of [Formula: see text]1,800 to 2,000 km, and associated with bands of shallower residual seafloor depth anomalies that suggest channeled flow over thousands of kilometers. Each of the three most clearly resolved fingers on the African side of the MAR corresponds to a separate group of whole mantle plumes rooted in distinct patches at the core-mantle boundary, feeding hotspots, and volcanic lines with distinct isotopic signatures. Plumes of a given group appear to merge at the top of the lower mantle before separating again, suggesting interaction of deep mantle flow with a more vigorous mesoscale circulation in the upper mantle. The corresponding hotspots are generally offset from the location of the deep mantle plume roots. The distinct isotopic signatures of these hotspot groups are also detected in the mid-ocean ridge basalts at the location where the fingers meet the ridge. Meanwhile, at least some of the variability within each plume group could originate in the upper mantle and extended transition zone where plumes in a given group appear to merge and pond. This study also adds to mounting evidence that the African large low shear velocity province is not a uniform, unbroken pile of dense material rising high above the core-mantle boundary, but rather a collection of mantle plumes rooted in patches of distinct composition.

Accurate proper motions of the protostellar binary system L 1551 IRS 5

Abstract We present an extensive astrometric study of the protostellar binary system L 1551 IRS 5, utilising nearly four decades of interferometric observations obtained between 1983 and 2022 with the Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA). We focus on observations with sufficient angular resolution to separate the two protostars (L 1551 IRS 5 N and S) in the system and derive accurate absolute proper motions for the two sources, as well as the relative proper motion between them. The absolute proper motion is dominated by the solar motion with only a modest contribution from L 1551 IRS 5’s peculiar velocity, as expected for a young stellar object. The relative proper motions enable us to constrain the orbit and derive a total mass of 0.96 ± 0.17 M⊙ for the system. While the emission of both sources at wavelengths shorter than about 1.3 cm is compact, the emission at longer wavelengths (λ ≳ 2 cm) is often affected by a free-free contribution from nearby shock features. The results presented here demonstrate that, when appropriate care is taken to combine the observations, interferometric data collected with different facilities, at different frequencies, and with different gain calibrators can be combined to obtain accurate astrometry. Observations of L 1551 IRS 5 over the next several decades with the VLA, ALMA and eventually the ngVLA and SKA ought to improve its dynamical mass measurement down to an accuracy of a few percent. Similar observations of other young multiple systems have the unique potential to provide dynamical mass estimates for the youngest known stellar objects.

HST Proper Motion of Andromeda III. Another Satellite Coorbiting the M31 Satellite Plane

We measure the absolute proper motion of Andromeda III (And III) using Advanced Camera for Surveys/Wide Field Channel and WFPC2 exposures spanning an unprecedented 22 yr time baseline. The WFPC2 exposures have been processed using a deep-learning centering procedure recently developed as well as an improved astrometric calibration of the camera. The absolute proper motion zero point is given by 98 galaxies and 16 Gaia EDR3 stars. The resulting proper motion is (μ α , μ δ ) = (−10.5 ± 12.5, 47.5 ± 12.5) μas yr−1. We perform an orbit analysis of And III using two estimates of M31's mass and proper motion. We find that And III’s orbit is consistent with dynamical membership to the Great Plane of Andromeda system of satellites although with some looser alignment compared to the previous two satellites NGC 147 and NGC 185. And III is bound to M31 if M31's mass is M vir ≥ 1.5 × 1012 M ⊙.

The geodynamics of plume-influenced mid-ocean ridges: insights from the Foundation Segment of the Pacific-Antarctic Ridge

The intersection of the Foundation Plume with the Pacific-Antarctic Ridge is a key location in global geodynamics where a mantle plume is approached by and interacting with a fast-spreading mid-ocean ridge. Here, we discuss a comprehensive major and trace element and Sr-Nd-Pb isotope dataset of new and existing samples from the young Foundation Seamount Chain (<5 Ma) and adjacent section of the Pacific-Antarctic Ridge. We use the geochemistry of axial, off-axis and intraplate lavas to map the spatial extent of plume dispersal underneath the ridge as well as the internal zonation of the upwelling plume. We show that the unusual length, increased crustal thickness and occurrence of silicic rocks on the axis of the Foundation Segment are the direct result of plume being tapped by the axial melting zone. We demonstrate that the plume is not homogeneous but shows a HIMU-like (high time-integrated 238U/204Pb) OIB (Ocean Island Basalt) component characterized by 206Pb/204Pb of up to 20.5 in its center and a more EM1-like (Enriched Mantle one) OIB component characterized by low U/Pb and 206Pb/204Pb but high Rb/Nb and 87Sr/86Sr towards its edges. Plume entrainment leads to a high magma supply rate that fosters the formation of silicic rocks and triggers the lengthening of the segment over time. However, plume dispersal is not symmetric as the geochemical tracers for the OIB component are extending <100 km northwards but >300 km southwards. We relate this to the current plate tectonic framework in which the obliquity between the migrating ridge and the absolute plate motions induces a sub-axial asthenospheric flow that preferentially channels plume material southwards.

Contributions of absolute binocular disparity, motion parallax and angular declination to absolute target localization

Contributions of absolute binocular disparity, motion parallax and angular declination to absolute target localization

Functional and Structural Long-Term Effects of Repetitive Instrument-Assisted Manual Therapy (IAMT) of the Lumbar Back on the Dorsal Myofascial Chain Among Female Soccer Players: A Randomized, Placebo-Controlled Pilot Trial.

Instrument-assisted manual therapy (IAMT) is suitable for optimizing movement prerequisites, such as range of motion, flexibility, microcirculation, and pain inhibition along myofascial chains, potentially leading to a reduction in hamstring injuries. To date, however, IAMT's modes of action remain largely unclear. This study aimed to examine the functional and structural effects of repetitive IAMT after 2.5 and five weeks. Sixteen healthy female soccer players (age: 21.4 (±5.1) years) were randomly grouped into an intervention group and a placebo control group. The intervention group received nine IAMT sessions twice weekly at the right lumbar region. The placebo group received a single pressureless "therapy" at baseline. In addition to structural ultrasound analyses (absolute motion and shear motion), functional mobility tests (passive straight leg raise (PSLR) test and lumbar and thoracic double inclinometry) were performed 4.0 (±2.0) days after the fourth IAMT and 3.4 (±1.1) days after the ninth IAMT in both groups. Hamstring flexibility in the PSLR test improved significantly after the ninth IAMT compared with the placebo group (p< 0.05, effect size: 0.913). No systematic differences were seen at the structural level. Repetitive IAMT can improve hamstring flexibility. Further studies in larger groups and diverse collectives are necessary to additionally test the postulated preventive effect also on hamstring injuries. Whether ultrasound is the right method for detecting structural changes in this context needs to be verified in the future.

Synchronization and stability of a vibrating system with two rigid frames driven by two groups of coaxial rotating exciters

This article explores the synchronization, stability and motion characteristics of the generalized dynamical model with two rigid frames (RFs) driven by two groups (even number) of coaxial rotating exciters. In light of this system’s generalized coordinates, we use Lagrange’s equations to derive the generalized differential equation of motion. The responses of absolute and relative motion of the generalized system are obtained using the transfer function method. The synchronization and stability criteria of multiple exciters are derived using the average method and Hamilton’s theory, respectively. Taking a dynamical model driven by two pairs of exciters as an example, the localized studies of generalized results are carried out. The stable synchronous solutions for phase differences and excitation frequency, the stability ability coefficient curves and the response curves are graphically presented considering the effect of two crucial dimensionless parameters on the stable synchronous states. The simulation results of the specific system are obtained using the fourth-order Runge-Kutta algorithms and compared with the numerical qualitative analysis results to reveal the high consistency between them and clarify the used methods’ effectiveness. The strength of this work stems from its use in the field of high power and large scale self-synchronization vibrating machines.

Teleseismic measurements of Upper Mantle Shear-Wave Anisotropy in Southern Mexico

The Mexican subduction system is an ideal region to study 3-D mantle deformation patterns in response to changes in slab geometry and the presence of tears. Shear-wave splitting measurements were made using SKS, SKKS, and PKS waves in southern Mexico, where the Cocos slab subducts beneath the North American and western Caribbean plates. For most of southern Mexico, the results are consistent with predominantly trench-normal fast polarization directions that can be interpreted as a consequence of sub-slab entrained flow and 2-D corner flow in the mantle wedge in the presence of A-type olivine fabric (or similar). This pattern of trench-perpendicular fast axes extends northward to the region southeast of the Trans-Mexican Volcanic Belt. Beneath its eastern end, fast axes rotate ∼20° clockwise and are likely controlled by the absolute motion of the North American plate. In southeastern Mexico, along the coast and above the mantle wedge tip, the fast axes are trench-normal and the delay times are the shortest. They were interpreted to result from a possibly serpentinized mantle wedge tip. In the same region above the mantle wedge core, the splitting parameters appear to result from different flow patterns in the mantle wedge and the sub-slab mantle.

On setting boundary conditions for calculations of turbomachines in 3-d computer packages

Unfortunately, in a growing number of publications of the results of the study of turbomachines in ANSYS and other packages, insufficient attention is paid to the choice of the flow model (absolute or relative) and the setting of boundary conditions in the areas adjacent to the rotating impeller: shroud seal, diaphragm (end) seals, gap over shroudless blades, steam balance holes, etc.As a rule, these areas contain such elements of geometry as a “ledge”, “projection”, “crest”, the flow around which, and, consequently, their resistance depends on the angle of incoming flow relative to the barrier. In the stages of turbomachines in sections behind fixed blade units, angle α1 between the flow velocity vector (in absolute motion) and the circumferential velocity is 10°÷25° (for steam turbine stages), 20°÷35° (for gas turbine stages) and 40°÷75° ((for axial compressor stages). It is shown (using the example of viscous flow around the “ledge + projection” system) that a change in the angle in the range of 15°÷90° changes the resistance by almost 2 times.The choice of a particular type of flow model (absolute or relative) for the domain primarily determines the value of the angle of interaction of the flow lines with an obstacle: it remains close to α1, or close to β1 = α1 + 20°÷70°, which significantly changes the qualitative picture of the viscous flow around the characteristic elements of geometry (“ledge”, “projection”, “crest”), and the values of integral parameters (flow rate, power, efficiency). The lack of recommendations on the correct choice of boundary conditions will inevitably lead not only to the inability to compare the results of various published studies, but also to their objective value. Therefore, the need to substantiate proposals for the choice of flow models in the areas of labyrinth seals, steam balance holes, gaps over shroudless blades, etc. is very relevant.

Insight into the Evolution of the Eastern Margin of the Wyoming Craton from Complex, Laterally Variable Shear Wave Splitting

Abstract Dense seismic arrays such as EarthScope’s Transportable Array (TA) have enabled high-resolution seismic observations that show the structure of cratonic lithosphere is more heterogeneous and complex than previously assumed. In this study, we pair TA data with data from the Bighorn Arch Seismic Experiment and the Crust and lithosphere Investigation of the Easternmost expression of the Laramide Orogeny (CIELO) to provide unprecedented detail on the seismic anisotropic structure of the eastern margin of the Wyoming Craton, where several orogens emerged from nominally strong cratonic lithosphere during the Laramide Orogeny. In this study, we use the splitting of teleseismic shear waves to characterize fabrics associated with deformation in the Earth’s crust and mantle. We constrain distinct anisotropic domains in the study area, and forward modeling shows that each of these domains can be explained by a single layer of anisotropy. Most significantly, we find a fast direction in the southern part of the Powder River Basin, which we refer to as the Thunder Basin Block (TBB), that deviates from absolute plate motion (APM). This change in splitting behavior coincides with changes in other modeled geophysical observations, such as active source P-wave velocity models, potential field modeling, and seismic attenuation analysis, which all show a significant change moving from the Bighorn Mountains to the TBB. We argue that these results correspond to structure predating the Laramide Orogeny, and most likely indicate a Neoarchean boundary preserved within the lithosphere.

When a Plateau Suppresses a Plume: Disappearance of the Samoan Plume Under the Ontong Java Plateau

AbstractThe Samoan hotspot generated an age‐progressive volcanic track that can be traced back to 24 Ma at Alexa Bank, but the trace of the older portion (&gt;24 Ma) of the hotspot track is unclear. We show that six seamounts located in and around the Magellan Seamount chain—north of the Ontong‐Java Plateau (OJP)—have ages (87–106 Ma), geochemistry, and locations consistent with absolute plate motion model reconstructions of the Samoan hotspot track in the late Cretaceous, and three additional seamounts have geochemistry and locations consistent with a Samoan origin. However, a large segment of the Samoan hotspot (24–87 Ma) remains unidentified. Absolute plate motion models show that, from ∼60 to 30 Ma, the OJP passed over the Samoan plume. The exceptional thickness of the OJP lithosphere may have largely suppressed Samoan plume melting because the inferred volcanic trace of the Samoan hotspot wanes, and then disappears, on the OJP. Fortunately, 44 Ma volcanism at Malaita Island, located on the southern margin of the OJP, has a location, age, and geochemistry consistent with a Samoan plume origin, and provides a “missing link” bridging the younger and older segments of the Samoan hotspot. Our synthesis of geochemical, geochronological, and plate motion model evidence reveals that Samoa exhibits a clear hotspot age progression for over 100 Myr. Passage of ancient plateaus over young plumes—here called “plume‐plateau” interaction—may be relatively common: the OJP also passed over the putative Rarotonga hotspot, and the Society and Pitcairn hotspots were overtopped by the Manihiki Plateau.

Berkeley on true motion

Studies of the Early Modern debate concerning absolute and relative space and motion often ignore the significance of the concept of true motion in this debate. Even philosophers who denied the existence of absolute space maintained that true motions could be distinguished from merely apparent ones. In this paper, I examine Berkeley's endorsement of this distinction and the problems it raises. First, Berkeley's endorsement raises a problem of consistency with his other philosophical commitments, namely his idealism. Second, Berkeley's endorsement raises a problem of adequacy, namely whether Berkeley can provide an adequate account of what grounds the distinction between true and merely apparent motion. In this paper, I argue that sensitivity to Berkeley's distinction between what is true in the metaphysical, scientific, and vulgar domains can address both the consistency and the adequacy problems. I argue that Berkeley only accepts true motion in the scientific and vulgar domains, and not the metaphysical. There is thus no inconsistency between his endorsement of true motion in science and ordinary language, and his metaphysical idealism. Further, I suggest that sensitivity to these three domains shows that Berkeley possesses resources to give an adequate account of how true motions are discovered in natural science.

Partial melt in mesoscale upper mantle upwellings beneath ocean basins

How tectonic plate motions are coupled with mantle flows remains an open question. Quasi-periodic 2000 km wavelength undulations aligned with absolute plate motion in the Pacific and Indian Ocean basins, observed in gravity and seafloor topography and coinciding with seismically imaged low shear velocity fingers in the upper mantle, suggest the presence of meso‑scale convection below the lithosphere. However, the correspondence of sub-lithospheric mantle mass excess, seafloor lows and slow upper mantle seismic velocities cannot be explained by temperature variations alone. Here we introduce a simplified system of bi-dimensional convective cells of width ∼1000 km, extending from the base of the lithosphere through the extended mantle transition zone (down to 1000 km depth), at least partly driven from below. From mass balance considerations in a viscous Earth, we show that the density excess required in the hot upwelling limbs may reflect the formation of stable dense lenses of dehydration-induced partial melt atop the 410 km discontinuity, and upward entrainment of a small fraction of quasi-buoyant partially molten and recrystallized material across the upper mantle. Our model provides an explanation for the thin low shear velocity layer detected intermittently above the 410 km discontinuity in some parts of ocean basins away from subducted slabs, and supports the presence of water in the transition zone.

A modular motion compensation pipeline for prospective respiratory motion correction of multi-nuclear MR spectroscopy

Magnetic resonance (MR) acquisitions of the torso are frequently affected by respiratory motion with detrimental effects on signal quality. The motion of organs inside the body is typically decoupled from surface motion and is best captured using rapid MR imaging (MRI). We propose a pipeline for prospective motion correction of the target organ using MR image navigators providing absolute motion estimates in millimeters. Our method is designed to feature multi-nuclear interleaving for non-proton MR acquisitions and to tolerate local transmit coils with inhomogeneous field and sensitivity distributions. OpenCV object tracking was introduced for rapid estimation of in-plane displacements in 2D MR images. A full three-dimensional translation vector was derived by combining displacements from slices of multiple and arbitrary orientations. The pipeline was implemented on 3 T and 7 T MR scanners and tested in phantoms and volunteers. Fast motion handling was achieved with low-resolution 2D MR image navigators and direct implementation of OpenCV into the MR scanner’s reconstruction pipeline. Motion-phantom measurements demonstrate high tracking precision and accuracy with minor processing latency. The feasibility of the pipeline for reliable in-vivo motion extraction was shown on heart and kidney data. Organ motion was manually assessed by independent operators to quantify tracking performance. Object tracking performed convincingly on 7774 navigator images from phantom scans and different organs in volunteers. In particular the kernelized correlation filter (KCF) achieved similar accuracy (74%) as scored from inter-operator comparison (82%) while processing at a rate of over 100 frames per second. We conclude that fast 2D MR navigator images and computer vision object tracking can be used for accurate and rapid prospective motion correction. This and the modular structure of the pipeline allows for the proposed method to be used in imaging of moving organs and in challenging applications like cardiac magnetic resonance spectroscopy (MRS) or magnetic resonance imaging (MRI) guided radiotherapy.

ФОРМАЛИЗМ РЕШЕНИЯ ПЕРВОЙ ЗАДАЧИ ДИНАМИКИ ШАГАЮЩИХ И КОЛЕСНО-ШАГАЮЩИХ МАШИН

The aim is to solve the first problem of the dynamics of machines moving their bodies with the help of legs, i.e., to calculate the control actions of the leg actuators that provide the given dynamics of the absolute motion of the body and satisfy the constraints, when fulfilled, there is no sliding of the supporting legs relative to the supporting surface. The research methods are related to system analysis, mechanics of body systems and robotics. We consider walking and wheel-walking machines with legs suspended from the body, in which the last kinematic pair is translational, there is no controlled foot, and the foot and the supporting surface interact at a single point. The resultsof the study contain analytical formulas for calculating dynamic reactions at the points of contact between the legs and the supporting surface, as well as driving forces and moments of forces in the drives of the supporting and carrying legs, providing a given motion of the body relative to the supporting surface, as well as its corresponding relative motion of the bodies of the supporting legs. A formalism for solving such problems is described, based on inverse vector recurrence formulas for calculating forces and moments of forces of dynamic reactions in kinematic pairs of tree-like systems of bodies with closure of the last body of the branch on the supporting surface. This formalism is extended to wheeled, wheel-walking and walking machines, which is demonstrated by appropriate examples. Analytical conditions for realizing a step without slipping of the support legs relative to the support surface are written down. Two simple wheel-walking machines, consisting of a linear electric drive and a driven (passive) wheelset, are proposed for the experimental determination of sliding and rolling friction coefficient values. In analytical forms of deduced calculation formulas (equations and inequalities) the structural, geometric, inertial and kinematic parameters of the investigated machines are explicitly expressed. The proposed formalism is demonstrated on the solutions of four problems from simple to complex through the reuse of formulas. Conclusion. The obtained mathematical models can be used in the processes of calculation and design of similar machines and their layouts.

228 Expert Hand Motion During Microvascular Anastomosis Simulation: Big Data Analysis Using Machine Learning Hand Detection

INTRODUCTION: Microanastomosis is a complex surgical technique that demands delicate and coordinated hand movement. Advances in machine learning technology have enabled new methods to study human motion. Convolutional neural networks are algorithms specialized in visual tasks that enable discrete object detection and tracking including the hands of a surgeon. METHODS: A machine learning hand detector was developed using a pre-trained convolutional neural network capable of tracking 21 hand landmarks without sensors attached. En-to-side microanastomosis was simulated using 2 mm polyvinyl-alcohol vessels and 10/0 micro-suture and recorded with a video camera capturing hand movement in the surgical field. Participants (n = 4) were expert cerebrovascular surgeons with significant operative experience in cerebral bypass surgery. Calculation of motion of 14 hand joint angles was performed using a vectorization method from landmark detections. Time series analysis was performed to calculate the absolute angular motion for each joint of the hand. RESULTS: Four minutes of simulation for each surgeon yielded a total of 784.294 angular detections (14 hand joints total). For the dominant hand, the mean (SD) absolute angular motion was expert 1: 178.2 rad (98.3); expert 2: 261.8 rad (164.3); expert 3: 449.9 rad (307); expert 4: 380.1 rad (198.1).For the non-dominant hand, the mean (SD) absolute angular motion was expert 1: 132.9 rad (64.6), expert 2: 149.2 rad (72.3); expert 3: 389.2 rad (243); expert 4: 162.6 rad (87.2). CONCLUSIONS: A machine learning hand detector system can calculate hand joint motion during microvascular anastomosis. The absolute angular motion is a quantitative performance metric providing information about hand stability during microanastomosis simulation. Such studies using powerful artificial intelligence detection algorithms may have educational potential in the assessment of complex and delicate surgical skills and supervision of surgical training.

Deciphering the crustal anisotropy and mantle flow beneath the Indo-Burma ranges from the harmonic decomposition of the receiver functions

The hyper-oblique indentation of the Indian plate beneath the Burmese sliver gives rise to the Indo-Burma Ranges (IBR) in the eastern part of the Indian subcontinent. This geological formation encompasses one of the enigmatic hotspots and includes the densely populated regions of India and Myanmar. Harmonic Decomposition (HD) of the receiver functions, derived from the Multi-Taper Correlation (MTC) technique, is used to model seismic anisotropy and morphological crustal deformation caused by subduction underneath IBR. We used teleseismic earthquake data from eleven broadband seismic stations installed within the IBR and its foredeep region. The findings indicate that the attitude of the fast symmetry axis or dipping direction of the interface is influenced by the trend of regional geological features and absolute plate motion, with the IBR exhibiting NNE-SSW and N-S directions and the Himalayan region showing NE-SW and E-W directions. Our results reveal that the coupling of the Indian plate with the Burmese and Eurasian plates induces lithospheric fabrics that align perpendicular to the coupling direction, resulting in anisotropy in the brittle upper crust. Directional analysis of the HD model for the interfaces at the middle or lower crust reveals the strike of the fast symmetry axis in the NNE-SSW direction, which suggests the alignment of minerals and partial melt in the direction of the major shear stress. The interface across the Moho reflects four-lobed periodicity, that is, 90o ambiguity in the strike direction of the fast symmetry axis, varying from the E-W to the N-S directions. The ambiguity indicates the possibility of the 2D-induced entrained mantle flow along the subducting Indian plate and the 3D toroidal flow parallel to the trend of the IBR.

Interactive Vehicle Trajectory Prediction for Highways Based on a Graph Attention Mechanism

Precise trajectory prediction is pivotal for autonomous vehicles operating in real-world traffic conditions, and can help them make the right decisions to ensure safety on the road. However, state-of-the-art approaches consider limited information about the historical movements of vehicles. On highways, drivers make their next judgments according to the behavior of the ambient vehicles. Thus, vehicles need to consider temporal and spatial interactions to reduce the risk of future collisions. In the current work, a trajectory prediction method is put forward in accordance with a graph attention mechanism. We add the absolute and relative motion information of vehicles to the input of the model to describe the vehicles’ past motion states more accurately. LSTM models are employed to process the historical motion information of vehicles, as well as the temporal correlations in interactions. The graph attention mechanism is applied to capture the spatial correlations between vehicles. Utilizing a decoder rooted in an LSTM framework, the future trajectory distribution is generated. Evaluation on the NGSIM US-101 and I-80 datasets substantiates the superiority of our approach over existing state-of-the-art algorithms. Moreover, the predictions of our model are analyzed.

Upper‐Mantle Anisotropy in the Southeastern Margin of Tibetan Plateau Revealed by Fullwave SKS Splitting Intensity Tomography

AbstractThe southeastern margin of the Tibetan Plateau has undergone complex deformation since the Cenozoic, resulting in a high level of seismicity and seismic hazard. Knowledge about the seismic anisotropy provides important insight about the deformation mechanism and the regional seismotectonics beneath this tectonically active region. In this study, we conduct fullwave multi‐scale tomography to investigate the seismic anisotropy in the southeastern margin of the Tibetan Plateau. Broadband records at 111 permanent stations in the region from 470 teleseismic events are used to obtain 5,216 high‐quality SKS splitting intensity (SI) measurements, which are then inverted in conjunction with 3D sensitivity kernels to obtain an anisotropic model with multi‐scale resolution. Resolution tests show that our data set recovers anisotropy anomalies reasonably well on the scale of 1° × 1° horizontally and ∼100 km vertically. Our result suggests that in the southeastern margin of the Tibetan Plateau the deformation in the lithosphere and asthenosphere are decoupled. The anisotropy in the lithosphere varies both laterally and vertically as a result of dynamic interactions of neighboring blocks as well as lithospheric reactivation. The anisotropy in the asthenosphere largely follows the direction of regional absolute plate motion. The SKS splittings observed at the surface are shown to be consistent with the vertical integral of our depth‐dependent anisotropy model over lithospheric and asthenospheric depths.

Task-Based Compliance Control for Bottle Screw Manipulation With a Dual-Arm Robot

In this paper, a novel task-based compliance control approach for a dual-arm robot is presented with a bottle screw task. The presented approach aims at overcoming uncertainties from the object model and contact forces during the bottle screw task. A novel framework is proposed to synthesize the task motion planning and compliance control that ensure desired performance of both accuracy and compliant motion. The proposed task-based compliance control approach provides a hierarchical strategy: gross motion planning and fine compliance motion planning. The gross motion planning involves the absolute and relative motion control on a macro scale, while the fine compliance motion planning deals with uncertainties by the compliance control to accomplish a task requiring high precision robustly. A theoretical modeling of the bottle screw task is presented within the proposed framework through the analysis of uncertainties and constraints. The experimental results show that the proposed framework is efficient and robust to operate a set of bottles.