12,554 research outputs found
Asian and Western Values: Implications for the APEC Community-Building Process
The discussion on Western and Eastern values has begun to take on emotional heat even in sedate conferences. Where a controversy rages, it is always useful to contribute any perspective that can help shed light. This paper is a call for other perspective that can help place the controversy on Western and Eastern values within the context of a community of people who have a great need for understanding each other.labor force, labor mobility, trade sector, labor migration, APEC
Asian and Western Values: Implications for the APEC Community-Building Process
The discussion on Western and Eastern values has begun to take on emotional heat even in sedate conferences. Where a controversy rages, it is always useful to contribute any perspective that can help shed light. This paper is a call for other perspective that can help place the controversy on Western and Eastern values within the context of a community of people who have a great need for understanding each other.labor force, labor mobility, trade sector, labor migration, APEC
Satellite remote sensing reveals a positive impact of living oyster reefs on microalgal biofilm development
Satellite remote sensing (RS) is routinely used for the large-scale monitoring of microphytobenthos (MPB) biomass in intertidal mudflats and has greatly improved our knowledge of MPB spatio-temporal variability and its potential drivers. Processes operating on smaller scales however, such as the impact of benthic macrofauna on MPB development, to date remain underinvestigated. In this study, we analysed the influence of wild Crassostrea gigas oyster reefs on MPB biofilm development using multispectral RS. A 30-year time series (1985-2015) combining high-resolution (30 m) Landsat and SPOT data was built in order to explore the relationship between C. gigas reefs and MPB spatial distribution and seasonal dynamics, using the normalized difference vegetation index (NDVI). Emphasis was placed on the analysis of a before-after control-impact (BACI) experiment designed to assess the effect of oyster killing on the surrounding MPB biofilms. Our RS data reveal that the presence of oyster reefs positively affects MPB biofilm development. Analysis of the historical time series first showed the presence of persistent, highly concentrated MPB patches around oyster reefs. This observation was supported by the BACI experiment which showed that killing the oysters (while leaving the physical reef structure, i.e. oyster shells, intact) negatively affected both MPB biofilm biomass and spatial stability around the reef. As such, our results are consistent with the hypothesis of nutrient input as an explanation for the MPB growth-promoting effect of oysters, whereby organic and inorganic matter released through oyster excretion and biodeposition stimulates MPB biomass accumulation. MPB also showed marked seasonal variations in biomass and patch shape, size and degree of aggregation around the oyster reefs. Seasonal variations in biomass, with higher NDVI during spring and autumn, were consistent with those observed on broader scales in other European mudflats. Our study provides the first multi-sensor RS satellite evidence of the promoting and structuring effect of oyster reefs on MPB biofilms
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
Real-Time Planning with Multi-Fidelity Models for Agile Flights in Unknown Environments
Autonomous navigation through unknown environments is a challenging task that
entails real-time localization, perception, planning, and control. UAVs with
this capability have begun to emerge in the literature with advances in
lightweight sensing and computing. Although the planning methodologies vary
from platform to platform, many algorithms adopt a hierarchical planning
architecture where a slow, low-fidelity global planner guides a fast,
high-fidelity local planner. However, in unknown environments, this approach
can lead to erratic or unstable behavior due to the interaction between the
global planner, whose solution is changing constantly, and the local planner; a
consequence of not capturing higher-order dynamics in the global plan. This
work proposes a planning framework in which multi-fidelity models are used to
reduce the discrepancy between the local and global planner. Our approach uses
high-, medium-, and low-fidelity models to compose a path that captures
higher-order dynamics while remaining computationally tractable. In addition,
we address the interaction between a fast planner and a slower mapper by
considering the sensor data not yet fused into the map during the collision
check. This novel mapping and planning framework for agile flights is validated
in simulation and hardware experiments, showing replanning times of 5-40 ms in
cluttered environments.Comment: ICRA 201
Time-Reversal-Violating Schiff Moment of 199Hg
We calculate the Schiff moment of the nucleus 199Hg, created by pi-N-N
vertices that are odd under parity (P) and time-reversal (T). Our approach,
formulated in diagrammatic perturbation theory with important core-polarization
diagrams summed to all orders, gives a close approximation to the expectation
value of the Schiff operator in the odd-A Hartree-Fock-Bogoliubov ground state
generated by a Skyrme interaction and a weak P- and T-odd pion-exchange
potential. To assess the uncertainty in the results, we carry out the
calculation with several Skyrme interactions (the quality of which we test by
checking predictions for the isoscalar-E1 strength distribution in 208Pb) and
estimate most of the important diagrams we omit.Comment: 13 pages, 7 figure
Time-Reversal Violating Schiff Moment of 225Ra
We use the Skyrme-Hartree-Fock method, allowing all symmetries to be broken,
to calculate the time-reversal-violating nuclear Schiff moment (which induces
atomic electric dipole moments) in the octupole-deformed nucleus 225Ra. Our
calculation includes several effects neglected in earlier work, including self
consistency and polarization of the core by the last nucleon. We confirm that
the Schiff moment is large compared to those of reflection-symmetric nuclei,
though ours is generally a few times smaller than recent estimates.Comment: Typos corrected, references added, minor changesin text. Version to
appear in PRC. 10 pages, 4 figure
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