COARSE3D: Class-Prototypes for Contrastive Learning in Weakly-Supervised 3D Point Cloud Segmentation

Annotation of large-scale 3D data is notoriously cumbersome and costly. As an alternative, weakly-supervised learning alleviates such a need by reducing the annotation by several order of magnitudes. We propose COARSE3D, a novel architecture-agnostic contrastive learning strategy for 3D segmentation. Since contrastive learning requires rich and diverse examples as keys and anchors, we leverage a prototype memory bank capturing class-wise global dataset information efficiently into a small number of prototypes acting as keys. An entropy-driven sampling technique then allows us to select good pixels from predictions as anchors. Experiments on three projection-based backbones show we outperform baselines on three challenging real-world outdoor datasets, working with as low as 0.001% annotations

Dissociate lattice oxygen redox reactions from capacity and voltage drops of battery electrodes.

The oxygen redox (OR) activity is conventionally considered detrimental to the stability and kinetics of batteries. However, OR reactions are often confused by irreversible oxygen oxidation. Here, based on high-efficiency mapping of resonant inelastic x-ray scattering of both the transition metal and oxygen, we distinguish the lattice OR in Na0.6[Li0.2Mn0.8]O2 and compare it with Na2/3[Mg1/3Mn2/3]O2. Both systems display strong lattice OR activities but with distinct electrochemical stability. The comparison shows that the substantial capacity drop in Na0.6[Li0.2Mn0.8]O2 stems from non-lattice oxygen oxidations, and its voltage decay from an increasing Mn redox contribution upon cycling, contrasting those in Na2/3[Mg1/3Mn2/3]O2. We conclude that lattice OR is not the ringleader of the stability issue. Instead, irreversible oxygen oxidation and the changing cationic reactions lead to the capacity and voltage fade. We argue that lattice OR and other oxygen activities should/could be studied and treated separately to achieve viable OR-based electrodes

Theoretical insight into the structure and stability of TNT and RDX in external electric field

A comparison of the effect of external electric field on the C–NO2 or N–NO2 bonds with the C–H and N–O bonds in 2,4, 6-trinitrotoluene (TNT)or hexahydro-1,3,5-trinitro-s-triazine (RDX) has been carried out using the M06-2x method with the 6-311++G** and aug-cc-pVTZ basis sets. The result shows that for TNT the fields have a minor effect on the C–NO2 and C–H bonds but a major effect on the N–O bonds, while in RDX the fields greatly affect the N–NO2 bond but the N–O and C–H bonds are slightly affected. Thus, in TNT the N–O bond can be the trigger bond, and in RDX the N–NO2 bond is always the trigger bond in electric fields. The explosive sensitivities may be reduced and the stabilities may be increased under the external electric fields in the negative direction along the C–NO2 bond axis for TNT and in the positive direction along the N–NO2 or N–O bond axis for RDX. The opposite trends can be suggested in the fields of the opposite directions along above bond axes. The introduction of external electric field into energetic material may be an available way to adjust explosive sensitivity. The analyses of AIM (atoms in molecules) and frequencies support the above viewpoints. The linear correlations between the field strengths and the changes of N−O/N−N bond lengths, ρ(N−O/N−N) values, or stretching frequencies of the N−O/N−N bonds have been found

Mechanisms of Competitive Adsorption Organic Pollutants on Hexylene-Bridged Polysilsesquioxane

Hexylene-bridged periodic mesoporous polysilsesquioxanes (HBPMS) are a promising new class of adsorbent for the removal of organic contaminants from aqueous solutions. These hybrid organic-inorganic materials have a larger BET surface area of 897 m2·g−1 accessible through a cubic, isotropic network of 3.82-nm diameter pores. The hexylene bridging group provides enhanced adsorption of organic molecules while the bridged polysilsesquioxane structure permits sufficient silanols that are hydrophilic to be retained. In this study, adsorption of phenanthrene (PHEN), 2,4-Dichlorophenol (DCP), and nitrobenzene (NBZ) with HBPMS materials was studied to ascertain the relative contributions to adsorption performance from (1) direct competition for sites and (2) pore blockage. A conceptual model was proposed to further explain the phenomena. This study suggests a promising application of cubic mesoporous BPS in wastewater treatment

N′-(2-Chloro­benzyl­idene)-4-methyl­benzohydrazide

In the title compound, C15H13ClN2O, the mol­ecule displays a trans conformation with respect to the C=N bond. The two aromatic rings form a dihedral angle of 12.0 (3)°. In the crystal, mol­ecules are connected via N—H⋯O hydrogen bonds into chains propagating along the c-axis direction

1,1′-(2-Thienylmethylene)di-2-naphthol ethyl acetate solvate

In the title compound, C25H18O2S·C4H8O2, there are inter­molecular O—H⋯O hydrogen bonds between the main mol­ecule and the solvent molecule. The thio­phene ring is oriented at dihedral angles of 70.87 (7) and 75.36 (4)° with respect to the mean planes of the two naphthyl ring systems