308,297 research outputs found
CoPhy: A Scalable, Portable, and Interactive Index Advisor for Large Workloads
Index tuning, i.e., selecting the indexes appropriate for a workload, is a
crucial problem in database system tuning. In this paper, we solve index tuning
for large problem instances that are common in practice, e.g., thousands of
queries in the workload, thousands of candidate indexes and several hard and
soft constraints. Our work is the first to reveal that the index tuning problem
has a well structured space of solutions, and this space can be explored
efficiently with well known techniques from linear optimization. Experimental
results demonstrate that our approach outperforms state-of-the-art commercial
and research techniques by a significant margin (up to an order of magnitude).Comment: VLDB201
Hardware-in-the-loop tuning of a feedback controller for a buck converter using a GA
This paper presents a methodology for tuning a PID-based feedback controller for a buck converter using the ITAE controller performance index. The controller parameters are optimized to ensure that a reasonable transient response can be achieved whilst retaining stable operation. Experimental results demonstrate the versatility of the on-line tuning methodology
Towards a millivolt optical modulator with nano-slot waveguides
We describe a class of modulator design involving slot waveguides and electro-optic polymer claddings. Such geometries enable massive enhancement of index tuning when compared to more conventional geometries. We present a semi-analytic method of predicting the index tuning achievable for a given geometry and electro-optic material. Based on these studies, as well as previous experimental results, we show designs for slot waveguide modulators that, when realized in a Mach-Zehnder configuration, will allow for modulation voltages that are orders of magnitude lower than the state of the art. We also discuss experimental results for nano-slot waveguides
Confronting brane inflation with Planck and pre-Planck data
In this paper, we compare brane inflation models with the Planck data and the
pre-Planck data (which combines WMAP, ACT, SPT, BAO and H0 data). The Planck
data prefer a spectral index less than unity at more than 5\sigma confidence
level, and a running of the spectral index at around 2\sigma confidence level.
We find that the KKLMMT model can survive at the level of 2\sigma only if the
parameter (the conformal coupling between the Hubble parameter and the
inflaton) is less than , which indicates a certain level
of fine-tuning. The IR DBI model can provide a slightly larger negative running
of spectral index and red tilt, but in order to be consistent with the
non-Gaussianity constraints from Planck, its parameter also needs fine-tuning
at some level.Comment: 10 pages, 8 figure
Photo-oxidative tuning of individual and coupled GaAs photonic crystal cavities
We demonstrate a new photo-induced oxidation technique for tuning GaAs
photonic crystal cavities using a pulsed laser with an
average power of . The laser oxidizes a small diameter spot, reducing the local index of refraction
and blueshifting the cavity. The tuning progress can be actively monitored in
real time. We also demonstrate tuning an individual cavity within a pair of
proximity-coupled cavities, showing that this method can be used to correct
undesired frequency shifts caused by fabrication imperfections in cavity
arrays.Comment: 4 pages, 3 figure
GA tuning of pitch controller for small scale MAVs
The paper presents the application of intelligent tuning methods for the control of a prototype MAV in order to address problems associated with bandwidth limited actuators and gust alleviation. Specifically, as a proof of concept, the investigation is focused on the pitch control of a MAV. The work is supported by experimental results from wind tunnel testing that shows the merits of the use of Genetic Algorithm (GA) tuning techniques compared to classical, empirical tuning methodologies. To provide a measure of relative merit, the controller responses are evaluated using the ITAE performance index. In this way, the proposed method is shown to induce far superior dynamic performance compared to traditional approaches
Tuning of nanophotonic and nanoplasmonic components with liquid crystals
Due to the strong electro-optic effect of liquid crystals, their refractive index can be modified by using relatively small voltage signals. This effect has been exploited in many configurations to tune the properties of optical components. In the past few years this tuning effect has been demonstrated with optical components with nanometer-scale size. The optical tuning is not only interesting to modulate the propagation of light, but also to tune the emission of light
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