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1. Radiative Influence of Horizontally Oriented Ice Crystals over Summit, Greenland

   https://doi.org/10.1029/2018JD028963  

   Stillwell, Robert A.; Neely, III, Ryan R.; Thayer, Jeffrey P.; Walden, Von P.; Shupe, Matthew D.; Miller, Nathaniel B. (November 2019, Journal of Geophysical Research: Atmospheres)

   Abstract Ice crystals commonly adopt a horizontal orientation under certain aerodynamic and electrodynamic conditions that occur in the atmosphere. While the radiative impact of horizontally oriented ice crystals (HOIC) has been theoretically studied with respect to their impact on shortwave cloud albedo, the longwave impact remains unexplored. This work analyzes the occurrence of HOIC at Summit, Greenland, from July 2015 to June 2017. Using polarization lidar and ancillary atmospheric sensors, ice crystal orientations are identified and used to interpret cloud radiative impact on the surface radiation budget. We find HOIC occur in at least 25.6% of all ice‐only column observations. We find that the shortwave impact of HOIC is to increase cloud radiative effect by approximately 22% for a given solar zenith angle. We also find that the longwave impact of HOIC compared to randomly oriented ice crystals are statistically different at the p < 0.01 significance level, increasing the surface radiative effect by approximately 8% for clouds with infrared optical depths < ~1. We suggest that the observed difference between the surface radiative effect for clouds containing randomly oriented ice crystals and HOIC may be due to enhanced scattering, but this hypothesis needs to be further explored with more detailed observations and modeling. 

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2. Oriented Ice Crystals: A Single-Scattering Property Database for Applications to Lidar and Optical Phenomenon Simulations

   https://doi.org/10.1175/JAS-D-19-0031.1  

   Saito, Masanori; Yang, Ping (August 2019, Journal of the Atmospheric Sciences)

   Abstract A database (TAMUoic2019) of the scattering, absorption, and polarization properties of horizontally oriented hexagonal plates (HOPs) and horizontally oriented hexagonal columns (HOCs) at three wavelengths (355, 532, and 1064 nm) is developed for applications to radiative transfer simulations and remote sensing implementations involving oriented ice crystals. The maximum dimension of oriented ice crystals ranges from 50 to 10 000 μm in 165 discrete size bins. The database accounts for 94 incident directions. The single-scattering properties of oriented ice crystals are computed with the physical-geometric optics method (PGOM), which is consistent with the invariant-imbedding T-matrix method for particles with size parameters larger than approximately 100–150. Note that the accuracy of PGOM increases as the size parameter increases. PGOM computes the two-dimensional phase matrix as a function of scattering polar and azimuth angles, and the phase matrix significantly varies with the incident direction. To derive the bulk optical properties of ice clouds for practical radiative transfer applications, the optical properties of individual HOPs and HOCs are averaged over the probability distribution of the tilting angle of oriented ice crystals based on the use of the TAMUoic2019 database. Simulations of lidar signals associated with ice clouds based on the bulk optical properties indicate the importance of the fraction of oriented ice crystals and the probability distribution of the tilting angle. Simulations of optical phenomena caused by oriented ice crystals demonstrate that the computed single-scattering properties of oriented ice crystals are physically rational. 

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3. Enhanced piezoelectricity from highly polarizable oriented amorphous fractions in biaxially oriented poly(vinylidene fluoride) with pure β crystals

   https://doi.org/10.1038/s41467-020-20662-7  

   Huang, Yanfei; Rui, Guanchun; Li, Qiong; Allahyarov, Elshad; Li, Ruipeng; Fukuto, Masafumi; Zhong, Gan-Ji; Xu, Jia-Zhuang; Li, Zhong-Ming; Taylor, Philip L.; et al (December 2021, Nature Communications)

   null (Ed.)

   Abstract Piezoelectric polymers hold great potential for various electromechanical applications, but only show low performance, with | d 33  | < 30 pC/N. We prepare a highly piezoelectric polymer ( d 33  = −62 pC/N) based on a biaxially oriented poly(vinylidene fluoride) (BOPVDF, crystallinity = 0.52). After unidirectional poling, macroscopically aligned samples with pure β crystals are achieved, which show a high spontaneous polarization ( P s ) of 140 mC/m 2 . Given the theoretical limit of P s,β  = 188 mC/m 2 for the neat β crystal, the high P s cannot be explained by the crystalline-amorphous two-phase model (i.e., P s,β  = 270 mC/m 2 ). Instead, we deduce that a significant amount (at least 0.25) of an oriented amorphous fraction (OAF) must be present between these two phases. Experimental data suggest that the mobile OAF resulted in the negative and high d 33 for the poled BOPVDF. The plausibility of this conclusion is supported by molecular dynamics simulations. 

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4. Oriented Point Sampling for Plane Detection in Unorganized Point Clouds

   https://doi.org/https://doi.org/10.1109/ICRA.2019.8793487  

   Sun, Bo; Mordohai, Philippos (May 2019, IEEE International Conference on Robotics and Automation)
5. POTLoc: Pseudo-label Oriented Transformer for point-supervised temporal Action Localization

   https://doi.org/10.1016/j.cviu.2024.104044  

   Vahdani, Elahe; Tian, Yingli (September 2024, Computer Vision and Image Understanding)

   This paper tackles the challenge of point-supervised temporal action detection, wherein only a single frame is annotated for each action instance in the training set. Most of the current methods, hindered by the sparse nature of annotated points, struggle to effectively represent the continuous structure of actions or the inherent temporal and semantic dependencies within action instances. Consequently, these methods frequently learn merely the most distinctive segments of actions, leading to the creation of incomplete action proposals. This paper proposes POTLoc, a Pseudo-label Oriented Transformer for weakly-supervised Action Localization utilizing only point-level annotation. POTLoc is designed to identify and track continuous action structures via a self-training strategy. The base model begins by generating action proposals solely with point-level supervision. These proposals undergo refinement and regression to enhance the precision of the estimated action boundaries, which subsequently results in the production of ‘pseudo-labels’ to serve as supplementary supervisory signals. The architecture of the model integrates a transformer with a temporal feature pyramid to capture video snippet dependencies and model actions of varying duration. The pseudo-labels, providing information about the coarse locations and boundaries of actions, assist in guiding the transformer for enhanced learning of action dynamics. POTLoc outperforms the state-of-the-art point-supervised methods on THUMOS’14 and ActivityNet-v1.2 datasets. 

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