587 research outputs found
Distil the informative essence of loop detector data set: Is network-level traffic forecasting hungry for more data?
Network-level traffic condition forecasting has been intensively studied for
decades. Although prediction accuracy has been continuously improved with
emerging deep learning models and ever-expanding traffic data, traffic
forecasting still faces many challenges in practice. These challenges include
the robustness of data-driven models, the inherent unpredictability of traffic
dynamics, and whether further improvement of traffic forecasting requires more
sensor data. In this paper, we focus on this latter question and particularly
on data from loop detectors. To answer this, we propose an uncertainty-aware
traffic forecasting framework to explore how many samples of loop data are
truly effective for training forecasting models. Firstly, the model design
combines traffic flow theory with graph neural networks, ensuring the
robustness of prediction and uncertainty quantification. Secondly, evidential
learning is employed to quantify different sources of uncertainty in a single
pass. The estimated uncertainty is used to "distil" the essence of the dataset
that sufficiently covers the information content. Results from a case study of
a highway network around Amsterdam show that, from 2018 to 2021, more than 80\%
of the data during daytime can be removed. The remaining 20\% samples have
equal prediction power for training models. This result suggests that indeed
large traffic datasets can be subdivided into significantly smaller but equally
informative datasets. From these findings, we conclude that the proposed
methodology proves valuable in evaluating large traffic datasets' true
information content. Further extensions, such as extracting smaller, spatially
non-redundant datasets, are possible with this method.Comment: 13 pages, 5 figure
A Data-driven and multi-agent decision support system for time slot management at container terminals: A case study for the Port of Rotterdam
Controlling the departure time of the trucks from a container hub is
important to both the traffic and the logistics systems. This, however,
requires an intelligent decision support system that can control and manage
truck arrival times at terminal gates. This paper introduces an integrated
model that can be used to understand, predict, and control logistics and
traffic interactions in the port-hinterland ecosystem. This approach is
context-aware and makes use of big historical data to predict system states and
apply control policies accordingly, on truck inflow and outflow. The control
policies ensure multiple stakeholders satisfaction including those of trucking
companies, terminal operators, and road traffic agencies. The proposed method
consists of five integrated modules orchestrated to systematically steer
truckers toward choosing those time slots that are expected to result in lower
gate waiting times and more cost-effective schedules. The simulation is
supported by real-world data and shows that significant gains can be obtained
in the system
Spatial and Temporal Characteristics of Freight Tours: A Data-Driven Exploratory Analysis
This paper presents a modeling approach to infer scheduling and routing
patterns from digital freight transport activity data for different freight
markets. We provide a complete modeling framework including a new
discrete-continuous decision tree approach for extracting rules from the
freight transport data. We apply these models to collected tour data for the
Netherlands to understand departure time patterns and tour strategies, also
allowing us to evaluate the effectiveness of the proposed algorithm. We find
that spatial and temporal characteristics are important to capture the types of
tours and time-of-day patterns of freight activities. Also, the empirical
evidence indicates that carriers in most of the transport markets are sensitive
to the level of congestion. Many of them adjust the type of tour, departure
time, and the number of stops per tour when facing a congested zone. The
results can be used by practitioners to get more grip on transport markets and
develop freight and traffic management measures
Radiation effects on silicon solar cells Final report, Dec. 1, 1961 - Dec. 31, 1962
Displacement defects in silicon solar cells by high energy electron irradiation using electron spin resonance, galvanometric, excess carrier lifetime, and infrared absorption measurement
On the duality relation for correlation functions of the Potts model
We prove a recent conjecture on the duality relation for correlation
functions of the Potts model for boundary spins of a planar lattice.
Specifically, we deduce the explicit expression for the duality of the n-site
correlation functions, and establish sum rule identities in the form of the
M\"obius inversion of a partially ordered set. The strategy of the proof is by
first formulating the problem for the more general chiral Potts model. The
extension of our consideration to the many-component Potts models is also
given.Comment: 17 pages in RevTex, 5 figures, submitted to J. Phys.
Large Car-following Data Based on Lyft level-5 Open Dataset: Following Autonomous Vehicles vs. Human-driven Vehicles
Car-Following (CF), as a fundamental driving behaviour, has significant
influences on the safety and efficiency of traffic flow. Investigating how
human drivers react differently when following autonomous vs. human-driven
vehicles (HV) is thus critical for mixed traffic flow. Research in this field
can be expedited with trajectory datasets collected by Autonomous Vehicles
(AVs). However, trajectories collected by AVs are noisy and not readily
applicable for studying CF behaviour. This paper extracts and enhances two
categories of CF data, HV-following-AV (H-A) and HV-following-HV (H-H), from
the open Lyft level-5 dataset. First, CF pairs are selected based on specific
rules. Next, the quality of raw data is assessed by anomaly analysis. Then, the
raw CF data is corrected and enhanced via motion planning, Kalman filtering,
and wavelet denoising. As a result, 29k+ H-A and 42k+ H-H car-following
segments are obtained, with a total driving distance of 150k+ km. A diversity
assessment shows that the processed data cover complete CF regimes for
calibrating CF models. This open and ready-to-use dataset provides the
opportunity to investigate the CF behaviours of following AVs vs. HVs from
real-world data. It can further facilitate studies on exploring the impact of
AVs on mixed urban traffic.Comment: 6 pages, 9 figure
A unified approach to combinatorial key predistribution schemes for sensor networks
There have been numerous recent proposals for key predistribution schemes for wireless sensor networks based on various types of combinatorial structures such as designs and codes. Many of these schemes have very similar properties and are analysed in a similar manner. We seek to provide a unified framework to study these kinds of schemes. To do so, we define a new, general class of designs, termed âpartially balanced t-designsâ, that is sufficiently general that it encompasses almost all of the designs that have been proposed for combinatorial key predistribution schemes. However, this new class of designs still has sufficient structure that we are able to derive general formulas for the metrics of the resulting key predistribution schemes. These metrics can be evaluated for a particular scheme simply by substituting appropriate parameters of the underlying combinatorial structure into our general formulas. We also compare various classes of schemes based on different designs, and point out that some existing proposed schemes are in fact identical, even though their descriptions may seem different. We believe that our general framework should facilitate the analysis of proposals for combinatorial key predistribution schemes and their comparison with existing schemes, and also allow researchers to easily evaluate which scheme or schemes present the best combination of performance metrics for a given application scenario
Signal and noise of Diamond Pixel Detectors at High Radiation Fluences
CVD diamond is an attractive material option for LHC vertex detectors because
of its strong radiation-hardness causal to its large band gap and strong
lattice. In particular, pixel detectors operating close to the interaction
point profit from tiny leakage currents and small pixel capacitances of diamond
resulting in low noise figures when compared to silicon. On the other hand, the
charge signal from traversing high energy particles is smaller in diamond than
in silicon by a factor of about 2.2. Therefore, a quantitative determination of
the signal-to-noise ratio (S/N) of diamond in comparison with silicon at
fluences in excess of 10 n cm, which are expected for the
LHC upgrade, is important. Based on measurements of irradiated diamond sensors
and the FE-I4 pixel readout chip design, we determine the signal and the noise
of diamond pixel detectors irradiated with high particle fluences. To
characterize the effect of the radiation damage on the materials and the signal
decrease, the change of the mean free path of the charge
carriers is determined as a function of irradiation fluence. We make use of the
FE-I4 pixel chip developed for ATLAS upgrades to realistically estimate the
expected noise figures: the expected leakage current at a given fluence is
taken from calibrated calculations and the pixel capacitance is measured using
a purposely developed chip (PixCap). We compare the resulting S/N figures with
those for planar silicon pixel detectors using published charge loss
measurements and the same extrapolation methods as for diamond. It is shown
that the expected S/N of a diamond pixel detector with pixel pitches typical
for LHC, exceeds that of planar silicon pixels at fluences beyond 10
particles cm, the exact value only depending on the maximum operation
voltage assumed for irradiated silicon pixel detectors
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