17 research outputs found
Self-Ordering Point Clouds
In this paper we address the task of finding representative subsets of points
in a 3D point cloud by means of a point-wise ordering. Only a few works have
tried to address this challenging vision problem, all with the help of hard to
obtain point and cloud labels. Different from these works, we introduce the
task of point-wise ordering in 3D point clouds through self-supervision, which
we call self-ordering. We further contribute the first end-to-end trainable
network that learns a point-wise ordering in a self-supervised fashion. It
utilizes a novel differentiable point scoring-sorting strategy and it
constructs an hierarchical contrastive scheme to obtain self-supervision
signals. We extensively ablate the method and show its scalability and superior
performance even compared to supervised ordering methods on multiple datasets
and tasks including zero-shot ordering of point clouds from unseen categories
Less than Few: Self-Shot Video Instance Segmentation
The goal of this paper is to bypass the need for labelled examples in
few-shot video understanding at run time. While proven effective, in many
practical video settings even labelling a few examples appears unrealistic.
This is especially true as the level of details in spatio-temporal video
understanding and with it, the complexity of annotations continues to increase.
Rather than performing few-shot learning with a human oracle to provide a few
densely labelled support videos, we propose to automatically learn to find
appropriate support videos given a query. We call this self-shot learning and
we outline a simple self-supervised learning method to generate an embedding
space well-suited for unsupervised retrieval of relevant samples. To showcase
this novel setting, we tackle, for the first time, video instance segmentation
in a self-shot (and few-shot) setting, where the goal is to segment instances
at the pixel-level across the spatial and temporal domains. We provide strong
baseline performances that utilize a novel transformer-based model and show
that self-shot learning can even surpass few-shot and can be positively
combined for further performance gains. Experiments on new benchmarks show that
our approach achieves strong performance, is competitive to oracle support in
some settings, scales to large unlabelled video collections, and can be
combined in a semi-supervised setting.Comment: 25 pages, 5 figures, 13 table
PointMixup: Augmentation for Point Clouds
This paper introduces data augmentation for point clouds by interpolation
between examples. Data augmentation by interpolation has shown to be a simple
and effective approach in the image domain. Such a mixup is however not
directly transferable to point clouds, as we do not have a one-to-one
correspondence between the points of two different objects. In this paper, we
define data augmentation between point clouds as a shortest path linear
interpolation. To that end, we introduce PointMixup, an interpolation method
that generates new examples through an optimal assignment of the path function
between two point clouds. We prove that our PointMixup finds the shortest path
between two point clouds and that the interpolation is assignment invariant and
linear. With the definition of interpolation, PointMixup allows to introduce
strong interpolation-based regularizers such as mixup and manifold mixup to the
point cloud domain. Experimentally, we show the potential of PointMixup for
point cloud classification, especially when examples are scarce, as well as
increased robustness to noise and geometric transformations to points. The code
for PointMixup and the experimental details are publicly available.Comment: Accepted as Spotlight presentation at European Conference on Computer
Vision (ECCV), 202
Spatial and climatic patterns of the relative abundance of poisonous vs. non-poisonous plants across the Northern Tibetan Plateau
Study on nanocrystalline coating prepared by electro-spraying 316L metal wire and its corrosion performance
In this work, we study the corrosion performance of coatings prepared by electrical explosion spraying of metal wires. 316L metal wire with a diameter of 1.5 mm is used as spray material, and the coating is prepared on the 45# steel substrate by electrical explosion spraying. The oil–water corrosion experiment of the coating is carried out in a constant temperature water bath of 60°C for 168 h. The scanning electron microscopy and energy-dispersive spectroscopy results of the experimental samples have shown that some metal oxides are found inside the coating, most of which are distributed at the grain boundaries with a size range of 30–50 nm. The corrosion rate of the coating is measured by weight loss method with a corrosion rate of 0.079 mm/annum. XRD results show that the corrosion generates CaCO3, Fe3O4, and MgFe2O4. Coating corrosion is mainly caused by the formation of electrochemical corrosion between oxides and non-oxides in the coating, and pitting corrosion and intergranular corrosion in the presence of chloride ions
Diagenetic Evolution Sequence and Pore Evolution Characteristics: Study on Marine-Continental Transitional Facies Shale in Southeastern Sichuan Basin
Diagenesis and pore structure are essential factors for reservoir evaluation. marine-continental transitional facies shale is a new shale gas reservoir of concern in the Sichuan Basin. The research on its diagenesis pore evolution model has important guiding significance in its later exploration and development. However, the current research on pore structure changes, diagenesis, and the evolution of marine-continental transitional facies shale is not sufficient and systematic. In order to reveal the internal relationship between pore structure changes and diagenesis, the evolution of marine-continental transitional facies shale was tested by X-ray diffraction, field emission scanning electron microscopy, low-pressure gas adsorption, nuclear magnetic resonance, and the diagenetic evolution sequence and nanopore system evolution of Longtan Formation shale was systematically studied. The results show that the Longtan Formation shale underwent short-term shallow after sedimentation, followed by long-term deep burial. The main diagenetic mechanisms of the Longtan Formation shale include compaction, dissolution, cementation, thermal maturation of organic matter, and transformation of clay minerals, which are generally in the middle-late diagenetic stage. The pore structure undergoes significant changes with increasing maturity, with the pore volumes of both micropores and mesopores reaching their minimum values at Ro = 1.43% and subsequently increasing. The change process of a specific surface area is similar to that of pore volumes. Finally, the diagenetic pore evolution model of Longtan Formation MCFS in Southeastern Sichuan was established
Response of Soil Respiration to Grazing in an Alpine Meadow at Three Elevations in Tibet
Alpine meadows are one major type of pastureland on the Tibetan Plateau. However, few studies have evaluated the response of soil respiration (Rs) to grazing along an elevation gradient in an alpine meadow on the Tibetan Plateau. Here three fenced enclosures were established in an alpine meadow at three elevations (i.e., 4313 m, 4513 m, and 4693 m) in July 2008. We measured Rs inside and outside the three fenced enclosures in July–September, 2010-2011. Topsoil (0–20 cm) samples were gathered in July, August, and September, 2011. There were no significant differences for Rs, dissolved organic C (DOC), and belowground root biomass (BGB) between the grazed and ungrazed soils. Soil respiration was positively correlated with soil organic C (SOC), microbial biomass (MBC), DOC, and BGB. In addition, both Rs and BGB increased with total N (TN), the ratio of SOC to TN, ammonium N (NH4+-N), and the ratio of NH4+-N to nitrate N. Our findings suggested that the negligible response of Rs to grazing could be directly attributed to that of respiration substrate and that soil N may indirectly affect Rs by its effect on BGB
Application of the Taguchi method to areal roughness-based surface topography control by waterjet treatments
Pure waterjet surface treatment without abrasive particles has a promising application in the biomedical field, because it induces compressive residual stresses on a metal surface and never leaves the tiny hard particles. In this work, the influence of operation pressure, standoff distance and the number of paths of the waterjet on the surface topography as well as the hardness was studied using the Taguchi method. The results showed that the most essential parameter is the operation pressure. By tuning the operation pressure from 100 to 300 MPa, the surface of Ti6Al4V specimens can be smoothed, roughened or damaged; when the surface layer is eroded, the new-born surface exhibits a clear stochastic nature accompanied by microvoids. The standoff distance benefits finer controlling the height parameters, whilst the number of paths affects the waviness. The hardening effect generated by the waterjet impingement extends to a few hundred-micron depth of the specimens, and the peak value of microhardness was found at a depth of 70 μm, which is an increase by greater than 20 %. The roughness parameters of Arithmetical mean height (Sa), Skewness (Ssk), Auto-correlation length (Sal), and Developed interfacial area ratio (Sdr) as a set are recommended to characterize the biomaterial's surface. The present research results promote the application of waterjet treatment in the field of fine-tuning biomaterial surface morphology
Experimental warming does not enhance gross primary production and above-ground biomass in the alpine meadow of Tibet
Large-Scale Spinning Assembly of Neat, Morphology-Defined, Graphene-Based Hollow Fibers
Large-scale assembly of graphenes in a well-controlled macroscopic fashion is important for practical applications. We have developed a facile and straightforward approach for continuous fabrication of neat, morphology-defined, graphene-based hollow fibers (HFs) <i>via</i> a coaxial two-capillary spinning strategy. With a high throughput, HFs and necklace-like HFs of graphene oxide have been well-controlled produced with the ease of functionalization and conversion to graphene HFs <i>via</i> simply thermal or chemical reduction. This work paves the way toward the mass production of graphene-based HFs with desirable functionalities and morphologies for many of important applications in fluidics, catalysis, purification, separation, and sensing