Provenance and depositional environments of fluvial-lacustrine sandstones of lower Permian Lucaogou low-order cycle, Bogda mountains, NW China

Compositional and textural maturity of sandstones may reflect provenance lithology and sediment transport distance, which are useful for paleogeographic reconstruction. 37 sandstones in six outcrop stratigraphic sections in Tarlong-Taodonggou and Zhaobishan areas in the greater Turpan-Junggar rift basin were studied to investigate the fluvial-lacustrine sandstone provenance in lower Permian Lucaogou (LCG) low-order cycle, Bogda Mountains, NW China. 400 points were counted in each thin section. All the samples are classified into lithic arenites, subarenites, wackes, and mudrocks. Three Petrofacies are defined. Petrofacies A is characterized by a high lithic content which is dominantly basaltic lithics with minor sedimentary lithics and felsic volcanic lithics with mean compositions of Q3F11L86, Qm2F12Lt86, Qp1Ls7Lv92, and Qm15P84K1 from four ternary classifications, respectively. Petrofacies B has a relatively high content of sedimentary lithics indicating a sedimentary source in the local rift shoulders with mean compositions of Q3F5L92, Qm3F8Lt89, Qp1Ls36Lv63, and Qm23P71K6. Petrofacies C has a higher content of felsic volcanic lithics with mean compositions of Q3F8L89, Qm4F9Lt87, Qp1Ls10Lv89, and Qm33P63K4. Tectonic setting is interpreted from ternary diagrams. All the samples fall in the recycled orogen and magmatic arc fields. Two sources, northern Tian Shan and rift shoulders, are differentiated on the basis of grain size and roundness. In Tarlong-Taodonggou area, similar trends of textural and compositional properties are present in N and NW Tarlong, and S Tarlong and Taodonggou indicating similar depositional history. SW Tarlong shows a unique trend due to the local sedimentary source. In Zhaobishan, the trend is highly variable, indicating episodic sediments influx from rift shoulders or a different catchment basin --Abstract, page iii

In Situ Experimental Study of the Friction of Sea Ice and Steel on Sea Ice

The kinetic coefficient of friction μk was measured for sea ice, stainless steel, and coated steel sliding on a natural sea ice cover. The effects of normal stress (3.10–8.11 kPa), ice columnar grain orientation (vertical and parallel to the sliding direction), sliding velocity (0.02–2.97 m·s–1), and contact material were investigated. Air temperature was higher than −5.0 °C for the test duration. The results showed a decline of μk with increasing normal stress with μk independent of ice grain orientation. The μk of different materials varied, partly due to distinct surface roughnesses, but all cases showed a similar increasing trend with increasing velocity because of the viscous resistance of melt-water film. The velocity dependence of μk was quantified using the rate- and state- dependent model, and μk was found to increase logarithmically with increasing velocity. In addition, μk obtained at higher air temperatures was greater than at lower temperatures. The stick-slip phenomenon was observed at a relatively high velocity compared with previous studies, which was partly due to the low-stiffness device used in the field. Based on the experimental data, the calculation of physical models can be compared.Peer reviewe

Representing Volumetric Videos as Dynamic MLP Maps

This paper introduces a novel representation of volumetric videos for real-time view synthesis of dynamic scenes. Recent advances in neural scene representations demonstrate their remarkable capability to model and render complex static scenes, but extending them to represent dynamic scenes is not straightforward due to their slow rendering speed or high storage cost. To solve this problem, our key idea is to represent the radiance field of each frame as a set of shallow MLP networks whose parameters are stored in 2D grids, called MLP maps, and dynamically predicted by a 2D CNN decoder shared by all frames. Representing 3D scenes with shallow MLPs significantly improves the rendering speed, while dynamically predicting MLP parameters with a shared 2D CNN instead of explicitly storing them leads to low storage cost. Experiments show that the proposed approach achieves state-of-the-art rendering quality on the NHR and ZJU-MoCap datasets, while being efficient for real-time rendering with a speed of 41.7 fps for $512 \times 512$ images on an RTX 3090 GPU. The code is available at https://zju3dv.github.io/mlp_maps/.Comment: Accepted to CVPR 2023. The first two authors contributed equally to this paper. Project page: https://zju3dv.github.io/mlp_maps