17,184 research outputs found
Reuleaux: Robot Base Placement by Reachability Analysis
Before beginning any robot task, users must position the robot's base, a task
that now depends entirely on user intuition. While slight perturbation is
tolerable for robots with moveable bases, correcting the problem is imperative
for fixed-base robots if some essential task sections are out of reach. For
mobile manipulation robots, it is necessary to decide on a specific base
position before beginning manipulation tasks.
This paper presents Reuleaux, an open source library for robot reachability
analyses and base placement. It reduces the amount of extra repositioning and
removes the manual work of identifying potential base locations. Based on the
reachability map, base placement locations of a whole robot or only the arm can
be efficiently determined. This can be applied to both statically mounted
robots, where position of the robot and work piece ensure the maximum amount of
work performed, and to mobile robots, where the maximum amount of workable area
can be reached. Solutions are not limited only to vertically constrained
placement, since complicated robotics tasks require the base to be placed at
unique poses based on task demand.
All Reuleaux library methods were tested on different robots of different
specifications and evaluated for tasks in simulation and real world
environment. Evaluation results indicate that Reuleaux had significantly
improved performance than prior existing methods in terms of time-efficiency
and range of applicability.Comment: Submitted to International Conference of Robotic Computing 201
High-Altitude Particle Acceleration and Radiation in Pulsar Slot Gaps
We explore the pulsar slot gap electrodynamics up to very high altitudes,
where for most relatively rapidly rotating pulsars both the standard
small-angle approximation and the assumption that the magnetic field lines are
ideal stream lines break down. We address the importance of the electrodynamic
conditions at the slot gap boundaries and the occurrence of a steady-state
drift of charged particles across the slot gap field lines at very high
altitudes. These boundary conditions and the deviation of particle trajectories
from stream lines determine the asymptotic behavior of the scalar potential at
all radii from the polar cap to near the light cylinder. As a result, we
demonstrate that the steady-state accelerating electric field must approach a
small and constant value at high altitude above the polar cap. This parallel
electric field is capable of maintaining electrons moving with high Lorentz
factors (a few times 10^7) and emitting curvature gamma-ray photons up to
nearly the light cylinder. By numerical simulations, we show that primary
electrons accelerating from the polar cap surface to high altitude in the slot
gap along the outer edge of the open field region will form caustic emission
patterns on the trailing dipole field lines. Acceleration and emission in such
an extended slot gap may form the physical basis of a model that can
successfully reproduce some pulsar high-energy light curves.Comment: 26 pages, 2 figures, to appear in the Astrophysical Journal, May 10,
200
ICT-based reforms in local government decision-making in the gram panchayats of Kerala
The beneficial impact of computerisation can be felt in all elements that contribute to decision-making in panchayats in the state of Kerala. However, even though computerisation is bringing about immense improvements compared to traditional administrative practices, but scope still remains for further improvement. Instead of the 'as it is' computerisation that is mostly carried out a process based approach is needed
Innovations in energy and climate policy: lessons from Vermont
We ask in this article: how can planners and policymakers replicate Vermontâs energy and climate policies? We begin by explaining the research methods utilized for this articleâmainly research interviews with a pool of experts, coupled with a targeted literature review. We then analyze the success of Vermont energy policy across four areas: energy efficiency, renewable energy, the smart grid, and energy governance. The following sections first explain how Vermont accomplished these successes, next identify a number of remaining barriers and elements of Vermontâs approach that may not be replicable, and finally present the articleâs conclusions
Fiscal autonomy for Scotland? A rejoinder
In their paper âA restatement of the case for fiscal autonomyâ Hallwood and MacDonald (2006b) claim that Barnett is a formula for a rakeâs progress and that fiscal autonomy, as outlined in their previous paper âThe economic case for Scottish fiscal autonomy: with or without independenceâ (Hallwood and MacDonald, 2006a), offers a superior financial settlement for Scotland. We here restate our continued disagreements with their argument. We start with corrections of their interpretation of our paper âFlaws and myths in the case for Scottish fiscal autonomyâ (Ashcroft, Christie and Swales, 2006) before highlighting where we believe their latest paper fails to provide answers to important questions we posed
Smear correction of highly-variable, frame-transfer-CCD images with application to polarimetry
Image smear, produced by the shutter-less operation of frame transfer CCD
detectors, can be detrimental for many imaging applications. Existing
algorithms used to numerically remove smear, do not contemplate cases where
intensity levels change considerably between consecutive frame exposures. In
this report we reformulate the smearing model to include specific variations of
the sensor illumination. The corresponding desmearing expression and its noise
properties are also presented and demonstrated in the context of fast imaging
polarimetry.Comment: Article accepted for publication in Applied Optics on 08 Jun 201
Gene dynamics of toll-like receptor 4 through a population bottleneck in an insular population of water voles (Arvicola amphibius)
Acknowledgments We would like to thank all colleagues who have contributed to fieldwork and sampling during this study. We would especially like to thank Marius Wenzel and Sandra Telfer for collaboration with different aspects of the study, and Dave Jones and Nat Jones for Bartonella PCR assays. This work was supported by the BBSRC studentship to MKG (BB/J01446X/1) and a NERC studentship to MKO. The research was carried out under project license PPL 40/1813.Peer reviewedPublisher PD
Enabling Fine-Grain Restricted Coset Coding Through Word-Level Compression for PCM
Phase change memory (PCM) has recently emerged as a promising technology to
meet the fast growing demand for large capacity memory in computer systems,
replacing DRAM that is impeded by physical limitations. Multi-level cell (MLC)
PCM offers high density with low per-byte fabrication cost. However, despite
many advantages, such as scalability and low leakage, the energy for
programming intermediate states is considerably larger than programing
single-level cell PCM. In this paper, we study encoding techniques to reduce
write energy for MLC PCM when the encoding granularity is lowered below the
typical cache line size. We observe that encoding data blocks at small
granularity to reduce write energy actually increases the write energy because
of the auxiliary encoding bits. We mitigate this adverse effect by 1) designing
suitable codeword mappings that use fewer auxiliary bits and 2) proposing a new
Word-Level Compression (WLC) which compresses more than 91% of the memory lines
and provides enough room to store the auxiliary data using a novel restricted
coset encoding applied at small data block granularities.
Experimental results show that the proposed encoding at 16-bit data
granularity reduces the write energy by 39%, on average, versus the leading
encoding approach for write energy reduction. Furthermore, it improves
endurance by 20% and is more reliable than the leading approach. Hardware
synthesis evaluation shows that the proposed encoding can be implemented
on-chip with only a nominal area overhead.Comment: 12 page
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