5 research outputs found
Experimental research and modeling of the parameters of the Quasi-Zenith Satellite System in Ukraine
The results of experimental studies and modeling of the orbital motion of QZSS geosynchronous satellites are presented. The possibility of forecasting the availability of satellites using almanac data obtained from the QZSS system and so on is shownNational Aviation Universit
Unsupervised Activity Segmentation by Joint Representation Learning and Online Clustering
We present a novel approach for unsupervised activity segmentation, which
uses video frame clustering as a pretext task and simultaneously performs
representation learning and online clustering. This is in contrast with prior
works where representation learning and clustering are often performed
sequentially. We leverage temporal information in videos by employing temporal
optimal transport. In particular, we incorporate a temporal regularization term
which preserves the temporal order of the activity into the standard optimal
transport module for computing pseudo-label cluster assignments. The temporal
optimal transport module enables our approach to learn effective
representations for unsupervised activity segmentation. Furthermore, previous
methods require storing learned features for the entire dataset before
clustering them in an offline manner, whereas our approach processes one
mini-batch at a time in an online manner. Extensive evaluations on three public
datasets, i.e. 50-Salads, YouTube Instructions, and Breakfast, and our dataset,
i.e., Desktop Assembly, show that our approach performs on par or better than
previous methods for unsupervised activity segmentation, despite having
significantly less memory constraints.Comment: Preprint. Under revie
Permutation-Aware Action Segmentation via Unsupervised Frame-to-Segment Alignment
This paper presents an unsupervised transformer-based framework for temporal
activity segmentation which leverages not only frame-level cues but also
segment-level cues. This is in contrast with previous methods which often rely
on frame-level information only. Our approach begins with a frame-level
prediction module which estimates framewise action classes via a transformer
encoder. The frame-level prediction module is trained in an unsupervised manner
via temporal optimal transport. To exploit segment-level information, we
utilize a segment-level prediction module and a frame-to-segment alignment
module. The former includes a transformer decoder for estimating video
transcripts, while the latter matches frame-level features with segment-level
features, yielding permutation-aware segmentation results. Moreover, inspired
by temporal optimal transport, we introduce simple-yet-effective pseudo labels
for unsupervised training of the above modules. Our experiments on four public
datasets, i.e., 50 Salads, YouTube Instructions, Breakfast, and Desktop
Assembly show that our approach achieves comparable or better performance than
previous methods in unsupervised activity segmentation.Comment: Accepted to WACV 202
STATIC BEARING CAPACITY OF STEEL-PLATE COMPOSITE WALLS
The features of the behavior of steel-plate composite walls for static loads are considered. Based on the analysis of modern technical and regulatory documentation, the rationale for the chosen research topic is given. A review of the literature is performed, and the features of development are noted. A detailed description and features of the experimental structures under study and the materials used are presented. The features of the test are considered, and the test equipment is described. Analytical and numerical calculations of structures for eccentric compression have been performed. The description of the calculation complex and the used models of materials is presented; the description of numerical models, the features of their construction and calculation are given, the results of calculations are presented – stress distributions, deformations, features of cracking. The general types of experimental eccentric compression wall models are presented, the nature of the loss of bearing capacity of experimental structures is described, and a picture of destruction is presented. The analysis of the experimental data obtained and their comparison with analytical and numerical calculations are performed
Learning by Aligning Videos in Time
We present a self-supervised approach for learning video representations
using temporal video alignment as a pretext task, while exploiting both
frame-level and video-level information. We leverage a novel combination of
temporal alignment loss and temporal regularization terms, which can be used as
supervision signals for training an encoder network. Specifically, the temporal
alignment loss (i.e., Soft-DTW) aims for the minimum cost for temporally
aligning videos in the embedding space. However, optimizing solely for this
term leads to trivial solutions, particularly, one where all frames get mapped
to a small cluster in the embedding space. To overcome this problem, we propose
a temporal regularization term (i.e., Contrastive-IDM) which encourages
different frames to be mapped to different points in the embedding space.
Extensive evaluations on various tasks, including action phase classification,
action phase progression, and fine-grained frame retrieval, on three datasets,
namely Pouring, Penn Action, and IKEA ASM, show superior performance of our
approach over state-of-the-art methods for self-supervised representation
learning from videos. In addition, our method provides significant performance
gain where labeled data is lacking.Comment: Accepted to CVPR 202