Threshold Angle Research Articles

Unsupervised Learning for the Automatic Counting of Grains in Nanocrystals and Image Segmentation at the Atomic Resolution.

Identifying the grain distribution and grain boundaries of nanoparticles is important for predicting their properties. Experimental methods for identifying the crystallographic distribution, such as precession electron diffraction, are limited by their probe size. In this study, we developed an unsupervised learning method by applying a Gabor filter to HAADF-STEM images at the atomic level for image segmentation and automatic counting of grains in polycrystalline nanoparticles. The methodology comprises a Gabor filter for feature extraction, non-negative matrix factorization for dimension reduction, and K-means clustering. We set the threshold distance and angle between the clusters required for the number of clusters to converge so as to automatically determine the optimal number of grains. This approach can shed new light on the nature of polycrystalline nanoparticles and their structure-property relationships.

Damage assessment of fixed U-shaped stiffeners stiffened square plates subjected to close-in explosions

The aim of this study is to suggest an approach for evaluating the damage modes and damage levels of the U-shaped stiffeners stiffened plates exposed to close-in explosions. To achieve this objective, a numerical model was developed in LS-DYNA, and the numerical model was verified by experimental results of the authors. Using this validated model, various U-shaped stiffeners stiffened plates were examined under different blast loads. The study investigated the factors that influence the damage modes of the plates, including the strength and distribution of the blast loads, as well as the geometry of the stiffened plates. The results indicated that the small size stiffened plates exhibited overall damage mode while the large stiffened plate showed localized damage at the same blast load. The blast load distribution on the different size plate led to different damage modes. Additionally, this study found that the slenderness of the stiffened plate had a great influence on the support rotation angle of the tensile tearing threshold. The larger span to thickness ratio can result in larger tensile tearing threshold. Moreover, 400 numerical cases were included and used to classify the damage modes of stiffened steel plates. Based on the damage mechanism of the stiffened steel plate, the damage number (Φ1 and Φ2) which considering the blast loads and material parameters of plate, the maximum incident angle of the blast load(α), and the relative stiffness of the stiffeners and the flat steel plate (κ1 and κ2), and the thickness to span ratio of the stiffened plate (λ) were combined to identify the damage modes of stiffened plates. Furthermore, a flow chart was constructed for determining damage modes based on these considerations. Additionally, a curve surface fitting was performed using Φ1 and λ, the fitting formulas were then used to estimate the deformation characteristics of the stiffened plates with U-shaped stiffeners. The damage levels of the U-shaped stiffeners stiffened plates were then classified as low damage, medium damage, severe damage, and collapse by combining the nominal support rotation angle with the threshold of the global tensile tearing at boundaries. The study result can provide insight into the damage mode identification and damage level classification of stiffened steel plates under explosion. Additionally, this study was a base of damage evaluation of the structure elements (such as steel box girder) include stiffened steel plates under explosions.

Experimental study of the effect of the input and output key angles on the discharge coefficient and efficiency of the PKWs

ABSTRACT The results showed that Cd, Ra, and, consequently, the increase in the passing flow discharge have a direct relationship with the inclination angle of the input and output keys, and for this reason, the weir of the piano key weir (PKW) with an angle of 90° has the highest Cd and Ra. An increase in the HT/P ratio in all angles leads to a decrease in Cd and Ra. However, the decrease rate of these parameters is less for a 15° angle compared to other threshold angles of the input and output keys. In the PKWs with different input and output key angles and at low HT/P ratios , the dropping flow nappe needs aeration due to its bonding. However, by increasing this ratio to the submergence condition and transforming into a linear weir, the dropping flow nappe is aerated. At low ratios of HT/P, the dropping flow nappes do not interfere, and the highest discharge coefficient and the highest weir efficiency are obtained. While by increasing the HT/P ratio, the dropping flow nappes start to collide and interfere with each other in the output keys, causing the flow rise and the weir submergence, and consequently, the discharge coefficient is decreased.

Static and moving minimum audible angle: Independent contributions of reverberation and position.

Two measures of auditory spatial resolution, the minimum audible angle and the minimum audible movement angle, have been obtained in a simulated acoustic environment using Ambisonics sound field reproduction. Trajectories were designed to provide no reliable cues for the spatial discrimination task. Larger threshold angles were found in reverberant compared to anechoic conditions, for stimuli on the side compared to the front, and for moving compared to static stimuli. The effect of reverberation appeared to be independent of the position of the sound source (same relative threshold increase) and was independently present for static and moving sound sources.

Examining How Interaural Differences Owing to Head Rotation during Walking Improve the Distance of Auditory Obstacle Perceptions among Individuals with Visual Impairment: A Case Study in Small-Scale Blind Group.

The ability of individuals with visual impairment to recognize an obstacle by hearing is called "obstacle sense". This ability is facilitated while they are moving, though the exact reason remains unknown. This study aims to clarify which acoustical factors may contribute to obstacle sense, especially obstacle distance perception. First, we conducted a comparative experiment regarding obstacle distance localization by individuals who are blind (N = 5, five men with blindness aged 22-42 (average: 29.8)) while they were standing and walking. The results indicate that the localized distance was more accurate while walking than while standing. Subsequently, the head rotation angle while walking and acoustic characteristics with respect to obstacle distance and head rotation angle were investigated. The peaks of the absolute head rotation angle during walking ranged from 2.78° to 11.11° (average: 6.55°, S.D.: 2.05°). Regarding acoustic characteristics, acoustic coloration occurred, and spectral interaural differences and interaural intensity differences were observed in the blind participants (N = 4, four men including two blind and two control sighted persons aged 25-38 (average: 30.8)). To determine which acoustic factors contribute, we examined the threshold of changes for interaural differences in time (ITD) and intensity (IID) (N = 11, seven men and four women with blindness aged 21-35 (average: 27.4)), as well as coloration (ICD) (N = 6, seven men and a woman with blindness aged 21-38 (average: 29.9))-depending on the head rotation. Notably, ITD and IID thresholds were 86.2 μs and 1.28 dB; the corresponding head rotation angles were 23.5° and 9.17°, respectively. The angle of the ICD threshold was 6.30° on average. Consequently, IID might be a contributing factor and ICD can be utilized as the cue facilitating the obstacle distance perception while walking.

HYBRID ADJUSTMENT OF UAS-BASED LiDAR AND IMAGE DATA

Abstract. Several advancements are going with Unmanned Aerial Systems (UAS) with the addition of multiple sensors and simultaneous data acquisition to obtain detailed geo-data for various applications. However, simultaneous data acquisition with multiple sensors, namely camera, and LiDAR, will also result in possible discrepancies associated with them, and they need to be solved to use a reliable and accurate final product. Several errors can be associated with both camera and LiDAR datasets due to the different characteristics of the sensors and terrain conditions. This research paper aimed to minimize the errors between LiDAR and the image datasets simultaneously acquired with an Unmanned Aerial System (UAS) by implementing a hybrid adjustment approach with a criterion for the roughness and threshold angle between surface normals. The initial trajectory of the UAS, raw LiDAR measurements, and image observations were the inputs used for the hybrid adjustment. The hybrid adjustment workflow minimizes the discrepancies with a least-squares-based simultaneous adjustment for both LiDAR and image datasets. For the hybrid adjustment process, three types of correspondences were established, namely: between image pairs, overlapping LiDAR strips, and between Image tie points and LiDAR strips. For quality control, mean Cloud-to-Cloud distances (C2C) were compared between both LiDAR and camera point clouds before and after hybrid adjustment. The surface-level analysis of the results was also carried out to analyze the errors before and after hybrid adjustment at a surface level for different types of surfaces. The results showed that the alignment between the point clouds has significantly improved from the range of meters to a centimeter-level after implementing the hybrid adjustment process. The proposed hybrid adjustment workflow can be used in mapping applications where a centimeter-level accuracy is requested.

Multi-isotopic constraints on the impacts of landslide on weathering and erosion in an active mountain range

In active mountains, landslides are the primary agent of erosion that readily generates materials with high weatherability. Understanding the linkage between landslide activity, erosion, and chemical weathering is critical for assessing how tectonic uplift affects the carbon cycle and Earth's climate. However, quantifying the contribution to chemical weathering and erosion fluxes from landslides remains challenging because of the lack of effective tracers related to landslide activities. Recent studies suggest that a suite of isotopic tracers, including the U, Sr and Be isotopes, have the potential to trace solutes and materials associated with landslide activities. Here we use three isotope ratios (234U/238U, 10Be/9Be, 87Sr/86Sr) to quantify the contribution to solid and solute fluxes from landslides in the tectonic-active eastern Tibetan mountains. We focus on 22 small catchments (drainage area < 50 km2) draining the epicentral region of the 2008 Wenchuan earthquake using samples collected in 2018 and 2019. Landslide seepage water and landslide sediment samples are used to constrain the landslide-weathering end-member. Tree branch and regolith topsoil samples are used to characterize the weathering end-member of regolith. We show that the U-Be-Sr isotopes can trace the solutes and solids sourced from landslide debris and quantify that landslides contribute 33.1 ± 16.2% (1SE) to the riverine solutes and 43.4 ± 20.8% (1SE) to the riverbed silt-sized sediment. These proportions are lower than the landslide-derived proportions in high-order catchments immediately (1 to 4 years) after the Wenchuan earthquake, which may relate to changes in landslide-material inputs across drainage networks and/or weathering processes over time. We also find that across 87 catchments with variable basin areas (from <1 km2 to ∼20,000 km2) draining the broad eastern Tibetan mountains, the 234U/238U activity ratio of river water and silt-sized riverbed sediment shows distinct characteristics for the catchments grouped by mean slope angles (mean slope angles shallower versus steeper than a common threshold angle of 32°). These findings suggest that U isotopes are a promising tracer of landslide-sourced solutes and materials. Overall, our work provides a case study showing that a multi-isotope approach can be used to quantify the impacts of landslides on erosion and weathering, providing new insights into how tectonic activities could affect the carbon cycle.

Does Vestibular Motion Perception Correlate with Axonal Pathways Stimulated by Subthalamic Deep Brain Stimulation in Parkinson's Disease?

Perception of our linear motion - heading - is critical for postural control, gait, and locomotion, and it is impaired in Parkinson's disease (PD). Deep brain stimulation (DBS) has variable effects on vestibular heading perception, depending on the location of the electrodes within the subthalamic nucleus (STN). Here, we aimed to find the anatomical correlates of heading perception in PD. Fourteen PD participants with bilateral STN DBS performed a two-alternative forced-choice discrimination task where a motion platform delivered translational forward movements with a heading angle varying between 0 and 30° to the left or to the right with respect to the straight-ahead direction. Using psychometric curves, we derived the heading discrimination threshold angle of each patient from the response data. We created patient-specific DBS models and calculated the percentages of stimulated axonal pathways that are anatomically adjacent to the STN and known to play a major role in vestibular information processing. We performed correlation analyses to investigate the extent of these white matter tracts' involvement in heading perception. Significant positive correlations were identified between improved heading discrimination for rightward heading and the percentage of activated streamlines of the contralateral hyperdirect, pallido-subthalamic, and subthalamo-pallidal pathways. The hyperdirect pathways are thought to provide top-down control over STN connections to the cerebellum. In addition, STN may also antidromically activate collaterals of hyperdirect pathway that projects to the precerebellar pontine nuclei. In select cases, there was strong activation of the cerebello-thalamic projections, but it was not consistently present in all participants. Large volumetric overlap between the volume of tissue activation and the STN in the left hemisphere positively impacted rightward heading perception. Altogether, the results suggest heavy involvement of basal ganglia cerebellar network in STN-induced modulation of vestibular heading perception in PD.

Earthquake-induced landslides coupled to fluvial incision in Andean Patagonia: Inferring their effects on landscape at geological time scales

Earthquakes can deeply shape the mountainous landscape through co-seismic landslides, generating large amounts of sediment that are then transported and distributed by rivers, controlling the landscape evolution. This influence is observed in the Liquiñe-Ofqui Fault System (LOFS), an active intra-arc fault system extending hundreds of kilometers through the Andes in Chilean Patagonia. For example, on April 21, 2007, a 6.2 Mw earthquake in the Aysén Fjord triggered over 500 landslides with volumes reaching 12–20 Mm3. Although there is a well-defined recurrence time, no study has focused on the effects of co-seismic landslides and sedimentary dynamics on the evolution of this mountainous landscape. In this research, we seek to improve the long-term understanding of the interaction between landslides and fluvial incisions in this segment of the Andes. For this reason, we implemented the HyLands landscape evolution model to simulate landslide activity coupled to fluvial incision. We consider the landslides that occurred during the 2007 earthquake as a precedent and simulate nine scenarios of ten seismic cycles over 21,000 years based on the 2100-year recurrence time documented in this region for the Holocene. We further used multiple uplift rates, sediment erodibility, drainage area, and channel slope exponent ratios (m/n) associated with the stream power law to assess the parameterization's impact on the landscape. According to our results, earthquake-induced landslides are a fundamental mechanism in the landscape's evolution in this region. Deposits from landslides can create transitory landscape forms that can intervene in fluvial dynamics. A significant part of the landslide sediment can remain on the slopes for thousands of years. We identified that parameterization considerably impacts the evolutionary response of the landscape in the evaluated time scale. Low m/n ratios can generate a different evolutionary response than other scenarios because the slopes are constantly driven towards their threshold angle, intensifying the interaction between landslides and fluvial incisions. Based on our analysis and considering the seismic history of the Aysén Fjord, we can explain a critical primary control of the LOFS on landscape erosion and sediment production. Implementing a hybrid landscape evolution model can help to infer the contribution of sediments associated with large earthquakes and improve the understanding of the role of landslides in the evolutionary history of Andean Patagonia. However, we stress that it is essential to advance in capturing erodibility and incision parameters of the stream power law in the Andes and local geomechanical information. Finally, we believe the landscape evolution models can help to deepen the knowledge of these processes in other Andean basins exposed to these geomorphic processes.

The structure and energy of symmetric tilt grain boundaries in tungsten

Considering the limitations of experiments and the necessity for improving the radiation resistance of materials based on the grain boundary (GB) engineering, more complete results on underlying GB properties are not yet available, and the correlations between such properties remain to be figured out. Here, we constructed a systematical database of the basic properties of 113 distinct symmetric tilt grain boundaries (STGBs) with 〈100〉, 〈110〉, and 〈111〉 axes in tungsten, including the GB energy, work of separation, excess volume and a single vacancy/interstitial segregation energy, calculated by molecular statics simulations with six interatomic potentials. Then, the correlations between these parameters were systematically investigated. We found that although the magnitude of GB properties yielded by these potentials is different, the correlations between these parameters are consistent with each other. According to the analysis of dislocations in these STGB's stable structures, we divided these STGBs into two categories, namely GBs consisting of discrete and overlapping dislocations (DDGBs vs. ODGBs), and identified the dislocation type, i.e., 〈100〉, 〈110〉, and 1/2〈111〉 dislocations, and threshold angles. For DDGBs, the work of separation and excess volume are negatively and positively proportional to the GB energy, respectively, while the minimal vacancy/interstitial segregation energy is close to a constant value for the STGBs consisting of the same dislocations. For ODGBs, there is no obvious correlation between these parameters. In addition, we found that the main contribution to the excess volume is within 5 Å around the GB, and the minimal vacancy/interstitial segregation energy of 〈110〉 STGBs is lower than 〈100〉 and 〈111〉 STGBs, showing a greater capture ability for vacancies/interstitials. We also confirmed that, in Fe and W, STGBs with the same crystallography have strongly correlated energies, which can be scaled by the cohesive energy or different shear moduli, depending on the chosen potential.

Anion Intercalation into Graphite Drives Surface Wetting.

The unique layered structure of graphite with its tunable interlayer distance establishes almost ideal conditions for the accommodation of ions into its structure. The smooth and chemically inert nature of the graphite surface also means that it is an ideal substrate for electrowetting. Here, we combine these two unique properties of this material by demonstrating the significant effect of anion intercalation on the electrowetting response of graphitic surfaces in contact with concentrated aqueous and organic electrolytes as well as ionic liquids. The structural changes during intercalation/deintercalation were probed using in situ Raman spectroscopy, and the results were used to provide insights into the influence of intercalation staging on the rate and reversibility of electrowetting. We show, by tuning the size of the intercalant and the stage of intercalation, that a fully reversible electrowetting response can be attained. The approach is extended to the development of biphasic (oil/water) systems that exhibit a fully reproducible electrowetting response with a near-zero voltage threshold and unprecedented contact angle variations of more than 120° within a potential window of less than 2 V.

Nanoscale pattern formation produced by ion bombardment of a rotating target: The decisive role of the ion energy.

We study the nanoscale patterns that form on the surface of a rotating sample of an elemental material that is bombarded with a broad noble gas ion beam for angles of incidence θ just above the critical angle for pattern formation θ_{c}. The pattern formation depends crucially on the ion energy E. In simulations carried out in the low-energy regime in which sputtering is negligible, we find disordered arrays of nanoscale mounds (nanodots) that coarsen in time. Disordered arrays of nanodots also form in the high-energy regime in which there is substantial sputtering, but no coarsening occurs close to the threshold angle. Finally, for values of E just above the sputter yield threshold, nanodot arrays with an extraordinary degree of hexagonal order emerge for a range of parameter values, even though there is a broad band of linearly unstable wavelengths. This finding might prove to be useful in applications in which highly ordered nanoscale patterns are needed.

Experimental study on mixed mode-I & II bond behavior of CFRP-to-steel joints with a ductile adhesive

Utilizing ductile adhesive on CFRP-reinforced steel structures makes the bonded interface with good resistance to dynamic and fatigue loading, which is suitable for the rehabilitation of steel bridges. Currently, considerable studies on the aspect of the CFRP–steel interface are focused only on mode-II loading, ignoring the effects of mode-I loading which could lead to a catastrophic collapse of the retrofitted structures. In the present paper, modified CFRP-to-steel bonded double overlapped joints with various initial peeling angles (θ) were manufactured in order to consider mode-I loading and study the bond behavior of CFRP-to-steel joints under mixed mode-I&II loading. The results showed that the bonded side with weaker adhesion between CFRP and adhesive debonded first and presented a CFRP-adhesive interfacial debonding mode, while the debonding of the other side was delayed and showed a cohesive failure mode in the adhesive. The bond shear stress vs. slip relationship of the debonded side showed to have a bi-linear trend in which the bond strength and interfacial fracture energy were low whilst the other side showed a trapezoidal relationship with a constant plastic plateau and with higher interfacial fracture energy. It was found that sudden debonding caused a quick propagation in the CFRP strain as well as on the global interfacial slip of the joints. It was also found that the peeling angle had significantly deteriorated the local bond response in mode-II, i.e. the trapezoidal bond shear stress vs. slip relationship in the joints with θ=0° shifted to a bi-linear relationship in the joints with θ=1°, θ=2° and with θ=3° in which the bond strength, slip and fracture energy, all decreased very much. Moreover, with θ=4° was experimentally determined as the threshold angle from which the associated mode-I loading can, per se, separate the CFRP from steel.

Impaired virtual space-tilting perception in Parkinson's disease with Pisa syndrome

IntroductionThe mechanism of Pisa syndrome in Parkinson's disease (PD) is unclear. We aimed to analyze the spatial perception of patients with PD with Pisa syndrome using virtual reality. MethodsIn total, 16 patients with Pisa syndrome, 16 age-matched patients without Pisa syndrome, and 16 age-matched controls were included. They viewed the virtual room gradually tilting to different 8 directions randomized across trials. The 75% discrimination threshold angle and the mean tilting discrimination angle for each direction were evaluated. Participants' lateral trunk deviation was measured using Kinect. Neuropsychological status was evaluated, using the Mini-Mental Status Examination (MMSE), the Japanese version of the Montreal-Cognitive Assessment, Frontal Assessment Battery, and the color-word interference task of the Stroop test. Visuospatial abilities were assessed using Benton Judgement of Line Orientation, and vestibular function was evaluated using Subjective Visual Vertical (SVV). ResultsThe 75% discrimination threshold in the tilting discrimination angle was larger in all directions for those in the Pisa syndrome group compared to patients in the without Pisa syndrome group and those in the control group. There were significant differences between the three groups for Front-Right, Right, and Back. Patients with Pisa syndrome showed a significantly worse performance in these tests compared with controls and tended to have worse SVV performance compared with patients without Pisa syndrome. ConclusionThe present findings support the hypothesis of visuo-spatial disability and/or attentional impairment in patients with Pisa syndrome.

Tailoring electromagnetic response of three-dimensional waffle-like metacomposite based on arrangement angle of ferromagnetic microwires

Three-dimensional waffle-like metacomposite (3DWM) composed of ferromagnetic microwires is proposed with the aim of integrating structure and microwave absorption performance. The metamaterial units were formed by weaving the ferromagnetic microwires into certain pattern along with the quartz fiber substrate, making it a layer-by-layer integral structure without delamination. Based on the significance of angle arrangement of ferromagnetic microwires on the electromagnetic response during the rotation of metacomposite in practical application, this study conducted experiment and simulation considering different angle arrangements ranging from 90° to 165° to reveal their electromagnetic response characteristics and microwave absorption mechanism within X and Ku bands. It has been found that the arrangement angle of ferromagnetic microwire can adjust the complex permittivity. The dielectric loss of 3DWM was mainly originated from multiple Debye relaxation process and the primary magnetic loss came from eddy current loss and exchange resonance. The threshold angle was found to be 135°, within which the improvement of impedance matching led to the enhancement of microwave absorption. In addition, the angle arrangement of ferromagnetic microwire affected the direction of electric and magnetic fields, which determines the dielectric loss and magnetic loss mechanisms. The 3DWM proposed in this study is promising in adjusting electromagnetic response of microwaves as a radar absorbing material in engineering applications.

Analysis of Threshold Angle Variations on The Quality of Finishing Free-form Surface in CNC Milling Process

The machining process using a combination of steep and shallow strategy is the most widely used strategy for the finishing process on complex models that have many areas of steep walls and shallow floors. Using a single machining strategy on the entire model can lead to long machining times and poor surface finish quality. The steep and shallow strategy can efficiently detect parts of the model that have steep contours and those that have shallow contours. In other words, this strategy can analyze the model surface angle at runtime to identify and divide the machining zone based on the slope angle or commonly called the threshold angle. In this context, the selection of the threshold angle is very important when carrying out the finishing process on free-form surfaces to produce a good surface quality. This study was conducted to determine the optimum threshold angle that can produce the minimum surface roughness between steep areas and shallow areas. Threshold angles that were varied were 20°, 30° and 40°. Machining was carried out using Ballnose type cutting tools with a diameter of 6 mm. Then the stepover and stepdown is 0.1 mm for the finishing process on the surface of the propeller product made of Aluminum by using a CNC Milling machine. From the experimental results, the most optimum threshold angle is at an angle of 40° with an average roughness value in the steep area of 1.9 mm and in the shallow area of 1.3mm and a total average roughness of 1.6mm.

Extension contracture stiff knee in haemophilia: Surgical timing and procedure for total knee arthroplasty.

Total knee arthroplasty (TKA) for a stiff knee of patients with haemophilia (PWH) represents a challenge for orthopaedic surgeons for the difficulties of exposing the knee and high complication rate compared to a flexible knee. To optimize the surgical exposure in primary TKA for PWH and to propose a threshold angle of extension contracture in treating haemophilic knee joints, retrospectively. Sixty-seven primary TKAs for PWH (mean age, 48 years) were performed, and incisional approaches to joint were standard (58 cases) and V-Y quadricepsplasty (V-Y) (9 cases). The decision of surgical approach was decided intraoperatively by two surgeons. Pre- and post-knee angles were evaluated in each group. Variables in the V-Y group were evaluated using univariate logistic regression analysis and receiver operating characteristic curve analysis. Univariate logistic regression analysis demonstrated that the preoperative range of motion (ROM) and flexion were significantly associated with V-Y. Threshold values of preoperative flexion and ROM resulting in V-Y using receiver operating characteristic analysis were 45° and 35°, respectively. Primary TKA for PWH using a standard approach may be performed before the stage preoperative flexion <45° and ROM <35°.

Gymnastics Action Recognition and Training Posture Analysis Based on Artificial Intelligence Sensor

In order to solve the problems that the gymnastics action recognition system cannot select gymnastics training items and difficulty modes, the calculation matching degree and its threshold angle are inaccurate, the effect and efficiency of action learning are low, and this research proposes a gymnastics action recognition and training pose analysis methods based on artificial intelligence sensors. This method completes the performance improvement of the traditional human action recognition algorithm and uses the skeletal features of the Kinect sensor to discriminate sports actions. Clustering based on static K -means algorithm increases the accuracy of pose selection, and each pose is recognized by human action using artificial neural network (ANN) and hidden Markov model (HMM). The obtained results are as follows: comparison of nonstatic and proposed static K -means algorithm on the training set and the overall accuracy of the proposed method is much better than the previous method. Among the four movements, the accuracy rate of “sitting” and “standing” movements is significantly higher, reaching 100%. In the gymnastics action recognition experiment, the average recognition rate of the system in this research is 93.6%, the false rejection rate is 5%, and the false acceptance rate is only 1.4%. It is proved that the system interface designed in this research can prompt the part that needs to be corrected, display the error on the output device, more efficiently assist the user to perform targeted training on the action to be learned, and improve the effect and efficiency of action learning.

Residence Time of Over‐Steepened Rock Masses in an Active Mountain Range

AbstractIn uplifting mountains, hillslopes steepen toward a threshold angle set by substrate material strength. Hillslopes beyond the threshold angle, referred to as excess topography, are mechanically unstable. The residence time scale of rock masses in excess topography (Tex) is critical for understanding time scales of surface processes and landscape evolution in steep mountains. However, Tex remains loosely constrained for varying slopes and lithologies. Here, we calculate Tex in the eastern Tibetan mountains by quantifying excess topography across lithologies, long‐term landslide erosion rates caused by seismicity and climate, and exhumation rates. Tex increases with local slope angles and is of the same order of magnitude across different lithologies but slightly longer for metamorphic rocks. Range‐scale Tex is estimated as ∼61–157 kyr, ∼3–9% of the relief‐rejuvenation timespan of threshold topography. Similar Tex regardless of lithologies and methods suggest steady‐state construction and erosion of excess topography over thousand to million years time scales in this orogen.

Landslide-Induced Weathering in Tectonically Active Mountains: Evidence From Dissolved Radiogenic Uranium Isotopes

Understanding weathering processes in landslide-dominated catchments is critical for evaluating the role of landslides in chemical weathering and the global carbon cycle. Previous studies have focused on solute concentrations in landslide-impacted landscapes, but have paid less attention to developing isotopic tracers of landslide-induced weathering fluxes. Recent work found that the dissolved radiogenic uranium isotopes in river water are closely related to the denudation rates in catchments draining steep mountains where landslides are thought to be a major erosion mechanism, suggesting the potential of uranium isotopes to trace landslide-induced weathering fluxes. Here we compile the dissolved radiogenic uranium isotopes (234U/238U ratios) in the river water samples from a group of catchments with variable landslide activities in the Minjiang River Basin at the eastern margin of the Tibetan Plateau. We derive three metrics of landslide activity from the analyses of digital topography and an inventory map of the co-seismic landslides triggered by the 2008 Mw7.9 Wenchuan earthquake: the normalized volume of landslides, the mean catchment slope angle, and the fraction of slopes steeper than a threshold angle beyond which slopes are mechanically unstable. The riverine dissolved 234U/238U ratios correlate negatively with the metrics of landslide activity in each catchment, which likely reflect the influence of landslides on the dissolved 234U/238U ratios. Mechanistically, enhanced bedrock landsliding would accelerate the exposure of fresh rock, promoting bedrock weathering and congruent dissolution of 234U and 238U contained in minerals; reduced landslide activities and enhanced regolith weathering would lead to preferential accumulation of 234U against 238U in solutes through alpha-recoil ejection, thus increasing dissolved 234U/238U. Our findings provide field evidence of using the riverine dissolved 234U/238U ratio to trace weathering fluxes driven by landslides, shedding new light on chemical weathering processes in uplifting mountains.