10,095 research outputs found
Economically viable domestic roofwater harvesting
Economically viable domestic roofwater harvestin
Better, faster, cheaper: research into roofwater harvesting for water supply in low income countries
Disentangling Forms of Lorentz Violation With Complementary Clock Comparison Experiments
Atomic clock comparisons provide some of the most precise tests of Lorentz
and CPT symmetries in the laboratory. With data from multiple such experiments
using different nuclei, it is possible to constrain new regions of the
parameter space for Lorentz violation. Relativistic effects in the nuclei allow
us to disentangle forms of Lorentz violation which could not be separately
measured in purely nonrelativistic experiments. The disentangled bounds in the
neutron sectors are at the 10^(-28) GeV level, far better than could be
obtained with any other current technique.Comment: 9 page
Testing Electron Boost Invariance with 2S-1S Hydrogen Spectroscopy
There are few good direct laboratory tests of boost invariance for electrons,
because the experiments required often involve repeated precision measurements
performed at different times of year. However, existing measurements and
remeasurements of the 2S-1S two-photon transition frequency in H--which were
done to search for a time variation in the fine structure constant--also
constitute a measurement of the boost symmetry violation parameter 0.83c_(TX) +
0.51c_(TY) + 0.22c_(TZ) = (4 +/- 8) x 10^(-11). This is an eight order of
magnitude improvement over preexisting laboratory bounds, and with only one
additional measurements, this system could yield a second comparable
constraint.Comment: 8 page
FASTER: Fast and Safe Trajectory Planner for Flights in Unknown Environments
High-speed trajectory planning through unknown environments requires
algorithmic techniques that enable fast reaction times while maintaining safety
as new information about the operating environment is obtained. The requirement
of computational tractability typically leads to optimization problems that do
not include the obstacle constraints (collision checks are done on the
solutions) or use a convex decomposition of the free space and then impose an
ad-hoc time allocation scheme for each interval of the trajectory. Moreover,
safety guarantees are usually obtained by having a local planner that plans a
trajectory with a final "stop" condition in the free-known space. However,
these two decisions typically lead to slow and conservative trajectories. We
propose FASTER (Fast and Safe Trajectory Planner) to overcome these issues.
FASTER obtains high-speed trajectories by enabling the local planner to
optimize in both the free-known and unknown spaces. Safety guarantees are
ensured by always having a feasible, safe back-up trajectory in the free-known
space at the start of each replanning step. Furthermore, we present a Mixed
Integer Quadratic Program formulation in which the solver can choose the
trajectory interval allocation, and where a time allocation heuristic is
computed efficiently using the result of the previous replanning iteration.
This proposed algorithm is tested extensively both in simulation and in real
hardware, showing agile flights in unknown cluttered environments with
velocities up to 3.6 m/s.Comment: IROS 201
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