214 research outputs found
Learning Agile Bipedal Motions on a Quadrupedal Robot
Can a quadrupedal robot perform bipedal motions like humans? Although
developing human-like behaviors is more often studied on costly bipedal robot
platforms, we present a solution over a lightweight quadrupedal robot that
unlocks the agility of the quadruped in an upright standing pose and is capable
of a variety of human-like motions. Our framework is with a bi-level structure.
At the low level is a motion-conditioned control policy that allows the
quadrupedal robot to track desired base and front limb movements while
balancing on two hind feet. The policy is commanded by a high-level motion
generator that gives trajectories of parameterized human-like motions to the
robot from multiple modalities of human input. We for the first time
demonstrate various bipedal motions on a quadrupedal robot, and showcase
interesting human-robot interaction modes including mimicking human videos,
following natural language instructions, and physical interaction
Identification of precipitation onset based on Cloudsat observations
AbstractObservations of cloud vertical structure by Cloud Profiling Radar on CloudSat satellite provide a unique opportunity to globally identify the onset of precipitation. In this study, based on a conceptual model for an adiabatic cloud, a new method to determine the onset of precipitation in marine warm clouds is developed. The new method uses the slope of radar reflectivities near the cloud top, which gradually reverses its signs as drizzle occurs. By analyzing multiyear CloudSat data, it is found that globally the radar reflectivity threshold for precipitation onset varies from â18 to â13dBZ with an average value of â16dBZ. The corresponding liquid water path threshold for precipitation onset is also studied by analyzing satellite microwave observations collocated with CloudSat data. Results show that the liquid water path threshold is 190gmâ2 as a global mean, varying from 150 to over 300gmâ2 depending on regions
Basic characteristics of monitoring global DPR Droplet Size Distribution and Precipitation Reflectivity Factor from June to August
Obtaining monitoring global droplet size distribution (DSD) is of great scientific significance for the study of precipitation characteristics and has important applications in retrieving precipitation by precipitation radar. Based on the GPM data provided by NASA's Goddard Flight Center (GFSC) and ERA5 reanalysis data, three-dimensional structure of DPR-derived mass-weighted mean diameter (D0) and normalized intercept parameter (dBNw) of DSD and precipitation reflectivity factor (PRF) from June to August in 2014-2020 were investigated. The regional and sea-land differences of DSD parameters and PRF in different latitudinal zones were also analyzed. The results are as follows. The spatial distribution patterns of D0 and dBNw are different and the large value region of dBNw (> 35) has small D0 ( 1.2 mm). The mean D0 over the land surface is larger than that over the ocean, but the mean dBNw is smaller than that over the ocean, and there are great differences between land and sea in the tropics and the northern hemisphere. The vertical distribution of precipitation reflectivity factor (PRF) is mainly determined by D0, and dBNw is a secondary factor. The D0 mean profile indicates that the main microphysical processes of the large, medium, and small precipitation particles are different. The dBNw profile indicates that the concentration of mean particles in the upper layer is smaller than that in the lower layer. Compared with other terrestrial regions, the distributions of DSD parameters and PRF over the Tibetan Plateau are the most concentrated, and the precipitation particles are smaller in size and lower in concentration
Chinese-to-English phonetic transfer of Chinese university EFL students
Phonetic transfer is defined as an L1 influence on the acquisition of L2 phonetics. Previous studies have investigated phonetic transfer in the area of articulation, but the effects of L1 on L2 pronunciation measured by speech recognition technology have been under-researched. This study aims to address the issue by focusing on a sample of 676 Chinese university ESL students. Drawing on quantitative data, it examined whether the participants applied phonetic transfer to ESL learning and what factors might have influenced the results of phonetic transfer. We assumed that Chinese-to-English phonetic transfer occurs but that the extent of the transfer would be small because Chinese and English belong to different language families. However, findings from this study confirm that Chinese-to-English phonetic transfer occurs and the extent is large. The findings regarding high transferability might be attributed to spelling through phonics and the nature of pronunciation acquisition
Retrieval of All-Sky Land Surface Temperature Considering Penetration Effect Using Spaceborne Thermal and Microwave Radiometry
Thermal infrared (TIR) remote sensing (RS) has been widely adopted for monitoring land surface temperature (LST). However, its application has been limited to cloud-free conditions, resulting in a need for LST retrieval methods that combine microwave (MW) and TIR channels. This is especially crucial in areas frequently covered by clouds. One limitation of the current LST retrieval methods is the absence of considering the penetration effect (PE) of MW, which leads to great uncertainty in barren and sparsely vegetated areas. To address this issue, this study proposes a new perspective that considers the PE to merge the LST retrieved from MW and TIR channels. The soil temperature integral equation is simplified based on the soil temperature and water content profiles. Consequently, a PE-based model is developed to convert the effective soil temperature into LST and merge the LST estimated from passive MW observations with those from moderate resolution imaging spectroradiometer (MODIS) LST products. The model considering PE performs better than the method that does not consider PE, as demonstrated by higher and lower root-mean-square error (RMSE) values. The PE-based model is then applied to Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) data, and the estimated LST is found to fit well with the MODIS LST product ( = 0.91). Using this model, an all-sky LST is retrieved by merging passive MW observations and MODIS LST products. Validation of the model at eight ground-based stations over the Tibetan Plateau (TP) demonstrates its reasonable accuracy in both clear-sky and cloudy conditions.</p
The Linear-Time-Invariance Notion of the Koopman Analysis-Part 2: Physical Interpretations of Invariant Koopman Modes and Phenomenological Revelations
This serial work presents a Linear-Time-Invariance (LTI) notion to the
Koopman analysis, finding consistent and physically meaningful Koopman modes
and addressing a long-standing problem of fluid-structure interactions:
deterministically relating the fluid and structure. Part 1 (Li et al., 2022)
developed the Koopman-LTI architecture and applied it to a pedagogical prism
wake. By the systematic procedure, the LTI generated a sampling-independent
Koopman linearization that captured all the recurring dynamics, finding six
corresponding, orthogonal, and in-synch fluid excitation-structure response
mechanisms. This Part 2 analyzes the six modal duplets' to underpin their
physical interpretations, providing a phenomenological revelation of the
subcritical prism wake. By the dynamical mode shape, results show that two
mechanisms at St1=0.1242 and St5=0.0497 describe shear layer dynamics, the
associated B\'ernard-K\'arm\'an shedding, and turbulence production, which
together overwhelm the upstream and crosswind walls by instigating a
reattachment-type of response. The on-wind walls' dynamical similarity renders
them a spectrally unified fluid-structure interface. Another four harmonic
counterparts, namely the subharmonic at St7=0.0683, the second harmonic at
St3=0.2422, and two ultra-harmonics at St7 =0.1739 and St13=0.1935, govern the
downstream wall. The 2P wake mode is also observed as an embedded harmonic of
the bluff-body wake. Finally, this work discovered the vortex breathing
phenomenon, describing the constant energy exchange in wake's
circulation-entrainment-deposition processes. With the Koopman-LTI, one may
pinpoint the exact excitations responsible for a specific structural response,
or vice versa.Comment: 24 figures, 60 pages. Video files at
https://drive.google.com/drive/folders/1AHdhUdAfNwlC1XUh-74PgQWW6jUHXJ5j?usp=sharin
Irreversible dual inhibitory mode: the novel Btk inhibitor PLS-123 demonstrates promising anti-tumor activity in human B-cell lymphoma.
The B-cell receptor (BCR) signaling pathway has gained significant attention as a therapeutic target in B-cell malignancies. Recently, several drugs that target the BCR signaling pathway, especially the Btk inhibitor ibrutinib, have demonstrated notable therapeutic effects in relapsed/refractory patients, which indicates that pharmacological inhibition of BCR pathway holds promise in B-cell lymphoma treatment. Here we present a novel covalent irreversible Btk inhibitor PLS-123 with more potent anti-proliferative activity compared with ibrutinib in multiple cellular and in vivo models through effective apoptosis induction and dual-action inhibitory mode of Btk activation. The phosphorylation of BCR downstream activating AKT/mTOR and MAPK signal pathways was also more significantly reduced after treatment with PLS-123 than ibrutinib. Gene expression profile analysis further suggested that the different selectivity profile of PLS-123 led to significant downregulation of oncogenic gene PTPN11 expression, which might also offer new opportunities beyond what ibrutinib has achieved. In addition, PLS-123 dose-dependently attenuated BCR- and chemokine-mediated lymphoma cell adhesion and migration. Taken together, Btk inhibitor PLS-123 suggested a new direction to pharmacologically modulate Btk function and develop novel therapeutic drug for B-cell lymphoma treatment
Fast Accurate and Automatic Brushstroke Extraction
Brushstrokes are viewed as the artistâs âhandwritingâ in a painting. In many applications such as style learning and transfer, mimicking painting, and painting authentication, it is highly desired to quantitatively and accurately identify brushstroke characteristics from old mastersâ pieces using computer programs. However, due to the nature of hundreds or thousands of intermingling brushstrokes in the painting, it still remains challenging. This article proposes an efficient algorithm for brush Stroke extraction based on a Deep neural network, i.e., DStroke. Compared to the state-of-the-art research, the main merit of the proposed DStroke is to automatically and rapidly extract brushstrokes from a painting without manual annotation, while accurately approximating the real brushstrokes with high reliability. Herein, recovering the faithful soft transitions between brushstrokes is often ignored by the other methods. In fact, the details of brushstrokes in a master piece of painting (e.g., shapes, colors, texture, overlaps) are highly desired by artists since they hold promise to enhance and extend the artistsâ powers, just like microscopes extend biologistsâ powers. To demonstrate the high efficiency of the proposed DStroke, we perform it on a set of real scans of paintings and a set of synthetic paintings, respectively. Experiments show that the proposed DStroke is noticeably faster and more accurate at identifying and extracting brushstrokes, outperforming the other methods
A case report of membrane induction combined with RIA technique for the repair of distal humerus segmentary bone defect
Bone nonunion and bone defect are common postoperative complications in clinic. Membrane induction or Ilizarov technique is often used to repair bone defect. Autologous bone is often used for bone defect repair and reconstruction, and the anterior superior iliac spine, posterior superior iliac spine or fibula bone is used as the donor area for bone extraction, but there are problems of donor area complications. In recent years, the development of bone marrow aspiration (RIA) has provided a new alternative way for the source of autogenous bone. We report a 48-year-old female patient with a comminuted supracondylar intercondylar fracture of the left humerus due to a car accident. After 8 months of emergency debridement and suture with Kirschner wire internal fixation, the fracture was found to be unhealed with extensive bone defects. We used membrane induction combined with RIA technology to repair and reconstruct the patients, and found good osteogenesis through late follow-up. In theory, membrane induction technique can realize the reconstruction of large segmental bone defects, but the scope of repair is often limited by the lack of autologous bone source. The emergence and development of RIA technology provides us with a new autologous bone donor area for bone repair and reconstruction surgery. It can provide a large amount of high-quality cancellar bone mud through minimally invasive means. Meanwhile, it can reduce patientsâ pain, infection, fracture, aesthetics and other problems caused by iliac bone extraction, and shorten patientsâ bed time. Maximize the preservation of the patientâs autologous bone source. For the first time in the world, we reported the combination of membrane induction technology and RIA technology in the treatment of segmental bone defects, providing a new idea for the treatment of bone defects
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