Search results for " tuning"

Optical tuning of dielectric nanoantennas for thermo-optically reconfigurable nonlinear metasurfaces

2021

We demonstrate optically tunable control of second-harmonic generation in all-dielectric nanoantennas: by using a control beam that is absorbed by the nanoresonator, we thermo-optically change the refractive index of the radiating element to modulate the amplitude of the second-harmonic signal. For a moderate temperature increase of roughly 40 K, modulation of the efficiency up to 60% is demonstrated; this large tunability of the single meta-atom response paves the way to exciting avenues for reconfigurable homogeneous and heterogeneous metasurfaces.

Hybrid Inorganic‐Organic White Light Emitting Diodes

2020

This chapter reviews the state of the art of materials, technologies, characterizations, process and challenges concerning hybrid white light‐emitting diodes (LEDs). Here, for a “hybrid LED” we mean a device based on a layer of organic phosphors (or a mix of inorganic and organic ones) pumped by a high‐energy inorganic LED. Light is emitted by a frequency down‐conversion (sometimes simply named color‐conversion) process. Benefits and weak spots of this technology are investigated with a special attention for the materials involved into the process of frequency down‐conversion, in order to envisage the future impact of the hybrid lighting technology among the well‐established inorganic ones.

Microreflectivity studies of wavelength control in oxidised AlGaAs microcavity

2002

Mathematics and Soft Computing in Music

2011

Mathematics is the fundamental tool for dealing with the physical processes that explain music but it is also in the very essence of this art. Musical notes, the first elements which music works with, are defined for each tuning system as very specific frequencies; however, instrumentalists know that small changes in these values do not have serious consequences. In fact, sometimes consensus is only reached if the entire orchestra alters the theoretical pitches. The explanation for this contradiction is that musicians implicitly handle very complex mathematical processes involving some uncertainty in the concepts and this is better explained in terms of fuzzy logic. Modelling the notes as f…

Fuzzy logic helps to integrate music theory and practice

2010

Among the many practices of composers, instrumentalists and singers which clearly correspond with fuzzy logic our focus here is on tuning. Different criteria have been used to select the sounds that music uses. A set containing these sounds (musical notes) is called a tuning system. Several tuning systems coexist in a classical orchestra. The pitches of the notes are different and very precisely defined for each system; however the consequences of small deviations from these theoretical frequencies are not serious. Actually, the orchestra members are aware of the necessity of reaching a consensus and adjust their instruments to tune well. Because of this, many musicians feel that the mathem…

FUZZY TCP: A PRELIMINARY STUDY

2002

Implementing efficient TCP for the Internet necessarily has to cope with the problem that the source does not know in advance which window allocation policy should be the best to use for a given network condition. In this paper, an on-line adaptive fuzzy system is used at the source in an objective to find the best possible weighted combination among the available policies.

Performance Evaluation of CANIT Algorithm in Presence of Congestion Losses

2001

In this paper, we analize by queuing-simulation CANIT (Congestion Avoidance with Normalized Interval of Time) algorithm performances in presence of congestion losses. In a former work [3], we proposed the algorithm (CANIT) for TCP (Transmission Control Protocol) congestion avoidance phase in order to improve fairness during this phase, and we showed that using CANIT algorithm in an environment without loss, instead of standard congestion avoidance algorithm improves both congestion avoidance fairness and bandwith utilization for long RTT connections. In this paper, we consider congestion losses and show that the fairness as well as the bandwith utilization are more efficient when using CANI…

Fine tuning of a photonic band-gap with picosecond laser pulses

2008

We report on light-driven tuning of the optical properties of colloidal photonic crystals (polystyrene opals) doped with gold nanoparticles (Au-np). Using picosecond pulses at 532 nm we obtained permanent changes in the stop band around 1700 nm, with resonance blue shifts as large as 30 nm.

Photocurrent Spectroscopy Applied to the Characterization of Passive Films on Sputter-Deposited Ti-Zr Alloys

2008

Abstract A photoelectrochemical investigation on thin (⩽13 nm) mixed oxides grown on sputter-deposited Ti–Zr alloys of different composition by air exposure and by anodizing (formation voltage, UF = 4 V/SCE) was carried out. The experimental results showed that the optical band gap, E g opt , increases with increasing Zr content in both air formed and anodic films. Such behaviour is in agreement with the theoretical expectation based on the correlation between the band gap values of oxides and the difference of electronegativity of their constituents. The flat band potential of the mixed oxides was found to be almost independent on the Ti/Zr ratio into the film and more anodic with respect …

All-optical tuning of a photonic band-gap via near-infrared laser pulses

2008

We present an all-optical tuning at IR wavelength in a novel photonic crystal consisting of a polystyrene opal with gold nanoparticles. The band-gap can be finely tuned with permanent shifts as large as 30 nm irradiating the sample with ps pulses at a low rep-rate in the visible.