133 research outputs found
I-SEM, DS3 and Great Britain/France interconnection electricity marketing modelling:a techno-economic analysis of renewable generations and interconnections in the wind dominated Integrated Single Electricity Market (I-SEM)
Validity of black hole complementarity in the context of generalized uncertainty principle
Recently, Elias C. Vagenas et al and Yongwan Gim et al studied the validity
of the no-cloning theorem in the context of generalized uncertainty principle
(GUP), but they came to conflicting conclusions. Motivated by a recent work
presented by Xin-Dong Du, we investigate the corrections to the temperature for
Schwarzschild black hole in the context of different forms of GUP, and obtain
the required energy to duplicate information for the Schwarzschild black hole,
it shows that the no-cloning theorem in the present of GUP is safe
Comparison of the ERP-Based BCI Performance Among Chromatic (RGB) Semitransparent Face Patterns
Objective: Previous studies have shown that combing with color properties may be used as part of the display presented to BCI users in order to improve performance. Build on this, we explored the effects of combinations of face stimuli with three primary colors (RGB) on BCI performance which is assessed by classification accuracy and information transfer rate (ITR). Furthermore, we analyzed the waveforms of three patterns. Methods: We compared three patterns in which semitransparent face is overlaid three primary colors as stimuli: red semitransparent face (RSF), green semitransparent face (GSF), and blue semitransparent face (BSF). Bayesian linear discriminant analysis (BLDA) was used to construct the individual classifier model. In addition, a Repeated-measures ANOVA (RM-ANOVA) and Bonferroni correction were chosen for statistical analysis. Results: The results indicated that the RSF pattern achieved the highest online averaged accuracy with 93.89%, followed by the GSF pattern with 87.78%, while the lowest performance was caused by the BSF pattern with an accuracy of 81.39%. Furthermore, significant differences in classification accuracy and ITR were found between RSF and GSF (p < 0.05) and between RSF and BSF patterns (p < 0.05). Conclusion: The semitransparent faces colored red (RSF) pattern yielded the best performance of the three patterns. The proposed patterns based on ERP-BCI system have a clinically significant impact by increasing communication speed and accuracy of the P300-speller for patients with severe motor impairment
Tilted subwavelength gratings: controlling anisotropy in metamaterial nanophotonic waveguides
Subwavelength grating (SWG) structures are an essential tool
in silicon photonics, enabling the synthesis of metamaterials
with a controllable refractive index. Here we propose, for the
first time to the best of our knowledge, tilting the grating elements
to gain control over the anisotropy of the metamaterial.
Rigorous finite difference time domain simulations
demonstrate that a 45° tilt results in an effective index variation
on the fundamental TE mode of 0.23 refractive index
units, whereas the change in the TM mode is 20 times smaller.
Our simulation predictions are corroborated by experimental
results. We furthermore propose an accurate theoretical
model for designing tilted SWG structures based on rotated
uniaxial crystals that is functional over a wide wavelength
range and for both the fundamental and higher order modes.
The proposed control over anisotropy opens promising venues
in polarization management devices and transformation
optics in silicon photonics.Universidad de Málaga (UMA); Ministerio de
Economía y Competitividad (MINECO) (IJCI-2016-30484,
TEC2015-71127-C2-R, TEC2016-80718-R); Ministerio de
Educación, Cultura y Deporte (MECD) (FPU16/06762);
European Regional Development Fund (ERDF); Comunidad
de Madrid (SINFOTON-CM S2013/MIT-2790); European
Association of National Metrology Institutes (EURAMET)
(H2020-MSCA-RISE-2015:SENSIBLE, JRP-i22 14IND13
Photind)
Designing polarization management devices by tilting subwavelength grating structures
Subwavelength gratings (SWG) are periodic structures which behave as controllable homogeneous metamaterials.
SWGs are extremely interesting when they are used in platforms with a limited choice of material refractive
indices, enabling the design of a myriad of high-performance devices. Here we present a novel technique to
gain control over the intrinsic anisotropy of the synthesized metamaterial. We show that tilting the silicon
segments in a SWG structure mainly affects the in-plane (TE) modes, with little impact on the out-of-plane
(TM) modes. Moreover, we present a methodology to quickly but accurately calculate the modes of a tilted
periodic structure modeling the structure as a rotated uniaxial crystal which can be solved with an anisotropic
mode solver. Measurements on a set of fabricated tilted SWG waveguides validate our simulation results. By
using the presented technique, we design a polarization beam splitter based on a 2x2 multimode interferometer.
The design is based on the optimization of the tilting angle to tone the beat length of the TE modes to be a half
of the beat length of the TM modes.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech;
Ministerio de Economía y Competitividad (MINECO) (IJCI-2016-30484, TEC2015-71127-C2-R, TEC2016-80718-R); Ministerio de Educación, Cultura y Deporte (MECD) (FPU16/06762); European Regional Development Fund (ERDF); Comunidad
de Madrid (SINFOTON-CM S2013/MIT-2790); European Association of National Metrology Institutes (EURAMET) (H2020-MSCA-RISE-2015:SENSIBLE, JRP-i22 14IND13 Photind)
Ultra-broadband Silicon Photonic Multimode Interference Coupler
In integrated optics, multimode interference couplers (MMIs) are used as light-wave splitters and combiners in a wide variety of devices ranging from spectrometers to sensors and coherent optical receivers. While their design and operation is generally well understood [1], the operational bandwidth remains limited. Here we present a sub-wavelength structured MMI, shown in Fig. 1(a), that overcomes this limitation and experimentally demonstrate a bandwidth exceeding 300nm at telecom wavelength, with more than 500nm bandwidth potentially attainable (as per 3D-FDTD simulations).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Measurement Accuracy in Silicon Photonic Ring Resonator Thermometers: Identifying and Mitigating Intrinsic Impairments
Silicon photonic ring resonator thermometers have been shown to provide
temperature measurements with a 10 mK accuracy. In this work we identify and
quantify the intrinsic on-chip impairments that may limit further improvement
in temperature measurement accuracy. The impairments arise from optically
induced changes in the waveguide effective index, and from back-reflections and
scattering at defects and interfaces inside the ring cavity and along the path
between light source and detector. These impairments are characterized for 220
x 500 nm Si waveguide rings by experimental measurement in a calibrated
temperature bath and by phenomenological models of ring response. At different
optical power levels both positive and negative light induced resonance shifts
are observed. For a ring with L = 100 um cavity length, the self-heating
induced resonance red shift can alter the temperature reading by 200 mK at 1 mW
incident power, while a small blue shift is observed below 100 uW. The effect
of self-heating is shown to be effectively suppressed by choosing longer ring
cavities. Scattering and back-reflections often produce split and distorted
resonance line shapes. Although these distortions can vary with resonance
order, they are almost completely invariant with temperature for a given
resonance and do not lead to measurement errors in themselves. The effect of
line shape distortions can largely be mitigated by tracking only selected
resonance orders with negligible shape distortion, and by measuring the
resonance minimum wavelength directly, rather than attempting to fit the entire
resonance line shape. The results demonstrate the temperature error due to
these impairments can be limited to below the 3 mK level through appropriate
design choices and measurement procedures
Optical wavefront phase-tilt measurement using Si-photonic waveguide grating couplers
Silicon photonic wavefront phase-tilt sensors for wavefront monitoring using
surface coupling grating arrays are demonstrated. The first design employs the
intrinsic angle dependence of the grating coupling efficiency to determine
local wavefront tilt, with a measured sensitivity of 7 dB/degree. A second
design connects four gratings in an interferometric waveguide circuit to
determine incident wavefront phase variation across the sensor area. In this
device, one fringe spacing corresponds to approximately 2 degree wavefront tilt
change. These sensor elements can sample a wavefront incident on the chip
surface without the use of bulk optic elements, fiber arrays, or imaging
arrays. Both sensor elements are less than 60 um across, and can be combined
into larger arrays to monitor wavefront tilt and distortion across an image or
pupil plane in adaptive optics systems for free space optical communications,
astronomy and beam pointing applications
Intelligent machines work in unstructured environments by differential neuromorphic computing
Efficient operation of intelligent machines in the real world requires
methods that allow them to understand and predict the uncertainties presented
by the unstructured environments with good accuracy, scalability and
generalization, similar to humans. Current methods rely on pretrained networks
instead of continuously learning from the dynamic signal properties of working
environments and suffer inherent limitations, such as data-hungry procedures,
and limited generalization capabilities. Herein, we present a memristor-based
differential neuromorphic computing, perceptual signal processing and learning
method for intelligent machines. The main features of environmental information
such as amplification (>720%) and adaptation (<50%) of mechanical stimuli
encoded in memristors, are extracted to obtain human-like processing in
unstructured environments. The developed method takes advantage of the
intrinsic multi-state property of memristors and exhibits good scalability and
generalization, as confirmed by validation in two different application
scenarios: object grasping and autonomous driving. In the former, a robot hand
experimentally realizes safe and stable grasping through fast learning (in ~1
ms) the unknown object features (e.g., sharp corner and smooth surface) with a
single memristor. In the latter, the decision-making information of 10
unstructured environments in autonomous driving (e.g., overtaking cars,
pedestrians) is accurately (94%) extracted with a 40*25 memristor array. By
mimicking the intrinsic nature of human low-level perception mechanisms, the
electronic memristive neuromorphic circuit-based method, presented here shows
the potential for adapting to diverse sensing technologies and helping
intelligent machines generate smart high-level decisions in the real world.Comment: 16 pages, 5 figure
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