Abstract: In urban canyon environments, global navigation satellite systems (GNSSs) frequently fail to provide reliable positioning services due to signal obstruction and multipath effects. This ...

The Secret Service said the driver was arrested and there was no longer a threat. President Trump was in the White House at the time, the agency said. By Francesca Regalado A person drove a vehicle ...

Earlier this year, governments around the world imposed travel and business restrictions to slow the spread of COVID-19. Like many people, the world’s atmospheric chemists were anxiously staying at ...