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Self-driving cars promise to keep traffic moving smoothly and reduce fuel usage, but proving those advantages has been a challenge with so few connected and automated vehicles, or CAVs, currently on the road. To study the potential benefits, researchers at Oak Ridge National Laboratory developed a simulation framework that analyzes the impact of partial market penetration of CAVs on fuel consumption, travel time and traffic flow in a merging on-ramp scenario under low, medium and heavy traffic volumes.
“We observed that an increased number of CAVs communicating and coordinating driving activity stabilize traffic flow and, depending on the traffic volume, can reduce fuel use by more than 40 percent,” said ORNL’s Jacky Rios-Torres.
“A steady traffic pattern, in turn, improves travel time.” Future research will explore the impact of CAVs in various traffic scenarios and determine whether CAVs can indirectly influence the driving performance of human-driven cars. The team’s results were published in IEEE Transactions on Intelligent Vehicles.
Physics–Elements at extremes
In neutron star mergers and supernovae, lighter elements absorb neutrons to create heavier elements whose nuclei are neutron-rich and radioactive. To better understand this phenomenon, physicists turned to the “doubly magic” tin isotope Sn-132, colliding it with a target at Oak Ridge National Laboratory to assess its properties as it lost a neutron to become Sn-131.
The results, published after years of complex data analysis, were combined with a prior experiment in which a nucleus of Sn-132 gained a neutron to become Sn-133. “Many ambiguities are reduced by systematically studying the addition and subtraction of neutrons,” said ORNL’s Steven Pain. “This is the first time this technique has been applied to such a heavy neutron-rich nucleus. These results will help benchmark theoretical models and guide future investigations of unstable nuclei with even greater neutron surpluses.”
Caption: Position-sensitive silicon detectors form the “nerves” of the Super Oak Ridge Rutgers University Barrel Array and yield high spatial resolution that enabled the Sn-132 experiment at ORNL–the first neutron-removal reaction on such a heavy, neutron-rich nucleus. The array, installed at Michigan State University, should begin operations in 2022. Credit: Steven Pain/Oak Ridge National Laboratory, U.S. Dept. of Energy
Grid–Balancing act
Oak Ridge National Laboratory scientists have devised a method to control the heating and cooling systems of a large network of buildings for power grid stability–all while ensuring the comfort of occupants. Buildings consume about 73 percent of the nation’s electricity and about half of that is for heating, ventilation and air conditioning systems.
Harnessing the HVAC-related demand of a fleet of buildings “can make a difference in frequency regulation,” or what grid operators refer to as the balance between electricity supply and demand, said ORNL’s Mohammed Olama. “We developed control schemes that don’t require a large number of calculations and can be implemented easily on existing HVAC systems that have simple on-off controls.” Simulations found that the controls are successful in providing frequency regulation from a fleet of 50 buildings, while keeping indoor temperatures within 0.5 degrees Celsius of a set range.