13,818 research outputs found
Truncation of Unitary Operads
We introduce truncation ideals of a -linear unitary symmetric operad
and use them to study ideal structure, growth property and to classify operads
of low Gelfand-Kirillov dimension
Molecular Lines of 13 Galactic Infrared Bubble Regions
We investigated the physical properties of molecular clouds and star
formation processes around infrared bubbles which are essentially expanding HII
regions. We performed observations of 13 galactic infrared bubble fields
containing 18 bubbles. Five molecular lines, 12CO (J=1-0), 13CO (J=1-0),
C18O(J=1-0), HCN (J=1-0), and HCO+ (J=1-0), were observed, and several publicly
available surveys, GLIMPSE, MIPSGAL, ATLASGAL, BGPS, VGPS, MAGPIS, and NVSS,
were used for comparison. We find that these bubbles are generally connected
with molecular clouds, most of which are giant. Several bubble regions display
velocity gradients and broad shifted profiles, which could be due to the
expansion of bubbles. The masses of molecular clouds within bubbles range from
100 to 19,000 solar mass, and their dynamic ages are about 0.3-3.7 Myr, which
takes into account the internal turbulence pressure of surrounding molecular
clouds. Clumps are found in the vicinity of all 18 bubbles, and molecular
clouds near four of these bubbles with larger angular sizes show shell-like
morphologies, indicating that either collect-and-collapse or radiation-driven
implosion processes may have occurred. Due to the contamination of adjacent
molecular clouds, only six bubble regions are appropriate to search for
outflows, and we find that four of them have outflow activities. Three bubbles
display ultra-compact HII regions at their borders, and one of them is probably
responsible for its outflow. In total, only six bubbles show star formation
activities in the vicinity, and we suggest that star formation processes might
have been triggered.Comment: 55 Pages, 32 figures. Accepted for publication in A
Context-aware multi-head self-attentional neural network model for next location prediction
Accurate activity location prediction is a crucial component of many mobility
applications and is particularly required to develop personalized, sustainable
transportation systems. Despite the widespread adoption of deep learning
models, next location prediction models lack a comprehensive discussion and
integration of mobility-related spatio-temporal contexts. Here, we utilize a
multi-head self-attentional (MHSA) neural network that learns location
transition patterns from historical location visits, their visit time and
activity duration, as well as their surrounding land use functions, to infer an
individual's next location. Specifically, we adopt point-of-interest data and
latent Dirichlet allocation for representing locations' land use contexts at
multiple spatial scales, generate embedding vectors of the spatio-temporal
features, and learn to predict the next location with an MHSA network. Through
experiments on two large-scale GNSS tracking datasets, we demonstrate that the
proposed model outperforms other state-of-the-art prediction models, and reveal
the contribution of various spatio-temporal contexts to the model's
performance. Moreover, we find that the model trained on population data
achieves higher prediction performance with fewer parameters than
individual-level models due to learning from collective movement patterns. We
also reveal mobility conducted in the recent past and one week before has the
largest influence on the current prediction, showing that learning from a
subset of the historical mobility is sufficient to obtain an accurate location
prediction result. We believe that the proposed model is vital for
context-aware mobility prediction. The gained insights will help to understand
location prediction models and promote their implementation for mobility
applications.Comment: updated Discussion section; accepted by Transportation Research Part
- …