69 research outputs found
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Development of Eco-Friendly Ramp Control for Connected and Automated Electric Vehicles
With on-board sensors such as camera, radar, and Lidar, connected and automated vehicles (CAVs) can sense the surrounding environment and be driven autonomously and safely by themselves without colliding into other objects on the road. CAVs are also able to communicate with each other and roadside infrastructure via vehicle-to-vehicle and vehicle-to-infrastructure communications, respectively, sharing information on the vehicles’ states, signal phase and timing (SPaT) information, enabling CAVs to make decisions in a collaborative manner. As a typical scenario, ramp control attracts wide attention due to the concerns of safety and mobility in the merging area. In particular, if the line-of-the-sight is blocked (because of grade separation), then neither mainline vehicles nor on-ramp vehicles may well adapt their own dynamics to perform smoothed merging maneuvers. This may lead to speed fluctuations or even shockwave propagating upstream traffic along the corridor, thus potentially increasing the traffic delays and excessive energy consumption. In this project, the research team proposed a hierarchical ramp merging system that not only allowed microscopic cooperative maneuvers for connected and automated electric vehicles on the ramp to merge into mainline traffic flow, but also had controllability of ramp inflow rate, which enabled macroscopic traffic flow control. A centralized optimal control-based approach was proposed to both smooth the merging flow and improve the system-wide mobility of the network. Linear quadratic trackers in both finite horizon and receding horizon forms were developed to solve the optimization problem in terms of path planning and sequence determination, and a microscopic electric vehicle (EV) energy consumption model was applied to estimate the energy consumption. The simulation results confirmed that under the regulated inflow rate, the proposed system was able to avoid potential traffic congestion and improve the mobility (in terms of average speed) as much as 115%, compared to the conventional ramp metering and the ramp without any control approach. Interestingly, for EVs (connected and automated EVs in this study), the improved mobility may not necessarily result in the reduction of energy consumption. The “sweet spot” of average speed ranges from 27–34 mph for the EV models in this study.View the NCST Project Webpag
The State-of-the-art of Coordinated Ramp Control with Mixed Traffic Conditions
Ramp metering, a traditional traffic control strategy for conventional
vehicles, has been widely deployed around the world since the 1960s. On the
other hand, the last decade has witnessed significant advances in connected and
automated vehicle (CAV) technology and its great potential for improving
safety, mobility and environmental sustainability. Therefore, a large amount of
research has been conducted on cooperative ramp merging for CAVs only. However,
it is expected that the phase of mixed traffic, namely the coexistence of both
human-driven vehicles and CAVs, would last for a long time. Since there is
little research on the system-wide ramp control with mixed traffic conditions,
the paper aims to close this gap by proposing an innovative system architecture
and reviewing the state-of-the-art studies on the key components of the
proposed system. These components include traffic state estimation, ramp
metering, driving behavior modeling, and coordination of CAVs. All reviewed
literature plot an extensive landscape for the proposed system-wide coordinated
ramp control with mixed traffic conditions.Comment: 8 pages, 1 figure, IEEE INTELLIGENT TRANSPORTATION SYSTEMS CONFERENCE
- ITSC 201
An Integrated Approach to Colorectal Anastomotic Leakage
__Abstract__
Colorectal anastomotic leakage (CAL) still remains a frequent and most dangerous
complication after gastrointestinal surgery, occurring in 4-33% patients and
contributing to one third of postoperative mortality. CAL substantially prolongs hospital
stay ? by one to two weeks - and greatly increases medical costs by as much as $24,000
within the first period of hospitalization, thereby approximately tripling the expenditure
relative to that of patients without CAL.
Due to the high risk of postoperative mortality, substantial efforts have been made
to investigate means of preventing and detecting CAL. In recent decades, however, even
with substantial improvements in surgical technique, no clear decrease in CAL rate has
been achieved. Much effort has been devoted to selecting patients with higher risks
of CAL, and many risk factors have been identified, such as being male, smoking,
alcohol abuse, obesity, a high American Society of Anesthesiologists (ASA) score, low level (e.g. rectal) anastomosis, tumor stage, urgent operation, increased
blood loss, and prolonged duration of surgery have been revealed. Previous studies
by our research group also reported several novel risk factors including after-hours surgery, and long-term and preoperative administration of corticosteroids. However, these
risk factors seem to cover most patients and thus may have limited value in the preoperative
selection of patients
Real-time Learning of Driving Gap Preference for Personalized Adaptive Cruise Control
Advanced Driver Assistance Systems (ADAS) are increasingly important in
improving driving safety and comfort, with Adaptive Cruise Control (ACC) being
one of the most widely used. However, pre-defined ACC settings may not always
align with driver's preferences and habits, leading to discomfort and potential
safety issues. Personalized ACC (P-ACC) has been proposed to address this
problem, but most existing research uses historical driving data to imitate
behaviors that conform to driver preferences, neglecting real-time driver
feedback. To bridge this gap, we propose a cloud-vehicle collaborative P-ACC
framework that incorporates driver feedback adaptation in real time. The
framework is divided into offline and online parts. The offline component
records the driver's naturalistic car-following trajectory and uses inverse
reinforcement learning (IRL) to train the model on the cloud. In the online
component, driver feedback is used to update the driving gap preference in real
time. The model is then retrained on the cloud with driver's takeover
trajectories, achieving incremental learning to better match driver's
preference. Human-in-the-loop (HuiL) simulation experiments demonstrate that
our proposed method significantly reduces driver intervention in automatic
control systems by up to 62.8%. By incorporating real-time driver feedback, our
approach enhances the comfort and safety of P-ACC, providing a personalized and
adaptable driving experience
Driver Digital Twin for Online Prediction of Personalized Lane Change Behavior
Connected and automated vehicles (CAVs) are supposed to share the road with
human-driven vehicles (HDVs) in a foreseeable future. Therefore, considering
the mixed traffic environment is more pragmatic, as the well-planned operation
of CAVs may be interrupted by HDVs. In the circumstance that human behaviors
have significant impacts, CAVs need to understand HDV behaviors to make safe
actions. In this study, we develop a Driver Digital Twin (DDT) for the online
prediction of personalized lane change behavior, allowing CAVs to predict
surrounding vehicles' behaviors with the help of the digital twin technology.
DDT is deployed on a vehicle-edge-cloud architecture, where the cloud server
models the driver behavior for each HDV based on the historical naturalistic
driving data, while the edge server processes the real-time data from each
driver with his/her digital twin on the cloud to predict the lane change
maneuver. The proposed system is first evaluated on a human-in-the-loop
co-simulation platform, and then in a field implementation with three passenger
vehicles connected through the 4G/LTE cellular network. The lane change
intention can be recognized in 6 seconds on average before the vehicle crosses
the lane separation line, and the Mean Euclidean Distance between the predicted
trajectory and GPS ground truth is 1.03 meters within a 4-second prediction
window. Compared to the general model, using a personalized model can improve
prediction accuracy by 27.8%. The demonstration video of the proposed system
can be watched at https://youtu.be/5cbsabgIOdM
Cytokines as Early Markers of Colorectal Anastomotic Leakage: A Systematic Review and Meta-Analysis
Purpose. Colorectal anastomotic leakage (CAL) is one of the most severe complications after colorectal surgery. This meta-analysis evaluates whether systemic or peritoneal inflammatory cytokines may contribute to early detection of CAL. Methods. Systematic literature search was performed in the acknowledged medical databases according to the PRISMA guidelines to identify studies evaluating systemic and peritoneal levels of TNF, IL-1β, IL-6, and IL-10 for early detection of CAL. Means and standard deviations of systemic and peritoneal cytokine levels were extracted, respectively, for patients with and without CAL. The meta-analysis of the mean differences was carried out for each postoperative day using Review Manager. Results. Seven articles were included. The meta-analysis was performed with 5 articles evaluating peritoneal cytokine levels. Peritoneal levels of IL-6 were significantly higher in patients with CAL compared to patients without CAL on postoperative days 1, 2, and 3 (P<0.05). Similar results were found for peritoneal levels of TNF but on postoperative days 3, 4, and 5 (P<0.05). The articles regarding systemic cytokine levels did not report any significant difference accordingly. Conclusion. Increased postoperative levels of peritoneal IL-6 and TNF are significantly associated with CAL and may contribute to its early detection
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