933,748 research outputs found
Comet C/2013 A1 Siding Spring. How treatment of data and NG effects can change our predictions about close encounters with Mars ?
We show that the estimates of close encounter of this comet with Mars depend
on data treatment. Using the data taken in the two-year period, we derived that
the comet will miss Mars on 2014 October 19 at the distance of about
km or km from its center, depending on the
method of data processing in the purely gravitational model of motion (based on
non-weighted data or weighted data, respectively). Unfortunately, the
non-gravitational model of motion is still very uncertain, thus we can only
speculate about estimates of expected distances for non-gravitational orbital
solutions. However, we did not obtain a significant differences in close
encounter prediction between the non-gravitational solutions and the
gravitational ones.Comment: 5 pages, 2 figure
Traffic Danger Recognition With Surveillance Cameras Without Training Data
We propose a traffic danger recognition model that works with arbitrary
traffic surveillance cameras to identify and predict car crashes. There are too
many cameras to monitor manually. Therefore, we developed a model to predict
and identify car crashes from surveillance cameras based on a 3D reconstruction
of the road plane and prediction of trajectories. For normal traffic, it
supports real-time proactive safety checks of speeds and distances between
vehicles to provide insights about possible high-risk areas. We achieve good
prediction and recognition of car crashes without using any labeled training
data of crashes. Experiments on the BrnoCompSpeed dataset show that our model
can accurately monitor the road, with mean errors of 1.80% for distance
measurement, 2.77 km/h for speed measurement, 0.24 m for car position
prediction, and 2.53 km/h for speed prediction.Comment: To be published in proceedings of Advanced Video and Signal-based
Surveillance (AVSS), 2018 15th IEEE International Conference on, pp. 378-383,
IEE
Aging of the Zero-Field-Cooled Magnetization in Ising Spin Glasses: Experiment and Numerical Simulation
A new protocol of the zero-field-cooled (ZFC) magnetization process is
studied experimentally on an Ising spin-glass (SG)
FeMnTiO and numerically on the Edwards-Anderson Ising SG
model. Although the time scales differ very much between the experiment and the
simulation, the behavior of the ZFC magnetization observed in the two systems
can be interpreted by means of a common scaling expression based on the droplet
picture. The results strongly suggest that the SG coherence length, or the mean
size of droplet excitations, involved even in the experimental ZFC process, is
about a hundred lattice distances or less.Comment: 4 pages, 5 fugure
Population Density-based Hospital Recommendation with Mobile LBS Big Data
The difficulty of getting medical treatment is one of major livelihood issues
in China. Since patients lack prior knowledge about the spatial distribution
and the capacity of hospitals, some hospitals have abnormally high or sporadic
population densities. This paper presents a new model for estimating the
spatiotemporal population density in each hospital based on location-based
service (LBS) big data, which would be beneficial to guiding and dispersing
outpatients. To improve the estimation accuracy, several approaches are
proposed to denoise the LBS data and classify people by detecting their various
behaviors. In addition, a long short-term memory (LSTM) based deep learning is
presented to predict the trend of population density. By using Baidu
large-scale LBS logs database, we apply the proposed model to 113 hospitals in
Beijing, P. R. China, and constructed an online hospital recommendation system
which can provide users with a hospital rank list basing the real-time
population density information and the hospitals' basic information such as
hospitals' levels and their distances. We also mine several interesting
patterns from these LBS logs by using our proposed system
The early evolution of the solar system
The problems of relating collapse conditions in an interstellar cloud to a model of the primitive solar nebula are discussed. In such a nebula there is a radial force balance between gravity, the pressure gradient, and centrifugal forces due to the rotation. Approximate values are given for the combinations of temperature and density throughout the nebula, from a maximum of about 2000 K near the center to less than 200 K in the outer portion. These conditions are based upon the compression adiabats in the terminal stages of the collapse of an interstellar cloud. One general conclusion, of great importance for accumulation of bodies within the solar system, is that interstellar grains should not be completely evaporated at distances in the nebula beyond about one or more astronomical units
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