Search results for "Pulse"
showing 10 items of 1508 documents
Experimental and theoretical study of the nonlinear birefringence in the formation process of vector solitons in a total polarization control ring ca…
2022
Abstract In this work, we present the numerical and experimental investigation of the polarization dynamics in a free birefringence mode-locked fiber laser. The laser includes a double-pass Erbium-doped fiber amplifier and 20-m long bi-twisted fiber at a twist rate of ± 6 turns m−1 to mitigate both, linear and circular birefringence effects. We found ellipticity changes due to nonlinear birefringence in the 20-m long fiber during pulse formation and propagation. In contrast with previously reported works, the inclusion of bi-twisted fiber allows investigate the nonlinear effects independently from the linear ones. The experimental behavior was confirmed by numerical simulations based on spl…
Coexistence of single-mode and multi-longitudinal mode emission in the ring laser model
2005
A homogeneously broadened unidirectonal ring laser can emit in several longitudinal modes for large enough pump and cavity length because of Rabi splitting induced gain. This is the so called Risken-Nummedal-Graham-Haken (RNGH) instability. We investigate numerically the properties of the multi-mode solution. We show that this solution can coexist with the single-mode one, and its stability domain can extend to pump values smaller than the critical pump of the RNGH instability. Morevoer, we show that the multi-mode solution for large pump values is affected by two different instabilities: a pitchfork bifurcation, which preserves phase-locking, and a Hopf bifurcation, which destroys it.
Free-depths reconstruction with synthetic impulse response in integral imaging
2015
Integral Imaging provides spatial and angular information of three-dimensional (3D) objects, which can be used both for 3D display and for computational post-processing purposes. In order to recover the depth information from an integral image, several algorithms have been developed. In this paper, we propose a new free depth synthesis and reconstruction method based on the two-dimensional (2D) deconvolution between the integral image and a simplified version of the periodic impulse response function (IRF) of the system. The period of the IRF depends directly on the axial position within the object space. Then, we can retrieve the depth information by performing the deconvolution with compu…
Free segmentation in rendered 3D images through synthetic impulse response in integral imaging
2016
Integral Imaging is a technique that has the capability of providing not only the spatial, but also the angular information of three-dimensional (3D) scenes. Some important applications are the 3D display and digital post-processing as for example, depth-reconstruction from integral images. In this contribution we propose a new reconstruction method that takes into account the integral image and a simplified version of the impulse response function (IRF) of the integral imaging (InI) system to perform a two-dimensional (2D) deconvolution. The IRF of an InI system has a periodic structure that depends directly on the axial position of the object. Considering different periods of the IRFs we …
Efficacy of dulaglutide on vascular health indexes in subjects with type 2 diabetes: a randomized trial
2021
Abstract Background Recent cardiovascular outcome trials have shown significant reductions in major cardiovascular (CV) events with glucagon-like peptide (GLP)-1 receptor agonists. Additionally, adjunctive surrogates for cardiovascular risk validated by some studies include arterial stiffness and endothelial function indexes. To date, no randomized trial has addressed the possible effects of antidiabetic interventional drugs such as GLP1 agonists on endothelial and arterial stiffness indexes as surrogate markers of vascular damage. Aims We aimed to evaluate metabolic efficacy and surrogate vascular efficacy endpoints of once-weekly dulaglutide (1.5 mg) plus traditional antidiabetic treatmen…
Mutual Information Analysis of Brain-Body Interactions during different Levels of Mental stress
2019
In this work, we analyze brain-heart interactions during different mental states computing mutual information (MI) between the dynamic activity of different physiological systems. In 18 healthy subjects monitored in a relaxed resting state and during a mental arithmetic and a serious game task, multichannel EEG, one lead ECG, respiration and blood volume pulse were collected via wireless non-invasive biosensors. From these signals, synchronous 300-second time series were extracted measuring brain activity via the δ, θ, α, and β EEG power, and activity of the body district via the ECG R-R interval η, the respiratory amplitude ϱ and the pulse arrival time π. MI was computed using a linear est…
PLZT Electro-optic Q-switch for Er:Cr:YSGG laser
1999
Q-switching of the Er:Cr:YSGG laser at 2.79 micrometers is realized using electrooptic modulators of PLZT X/65/35 ceramics. The high (but slow as compared with single crystals) electrooptical effect in PLZT allowed to construct Q-switches with an aperture larger than 4 X 4 mm 2 , small lengths of 3 - 6 mm, with a control voltage of 1000 - 1500 V. Q-switching is realized using modulators in two modes--as a (lambda) /2 switch placed into the laser cavity at the Brewster angle avoiding reflection losses and as a (lambda) /4 switch with higher single pass losses due to Fresnel reflections. A higher laser output was obtained using (lambda) /2 switching. The obtained pulses had a halfwidth of 150…
Improvement of solid state Er:YAG pulse laser performance for use in medicine
1999
The large quadratic electro-optic effect of PLZT ceramics allows to design small size modulators for the solid state infrared Er:YAG laser (lasing at (lambda) equals 2.94 micrometers - the most pronounced absorption band of water), which has found application in medicine for efficient ablation of hard and soft tissues. In the free-running mode, the Er:YAG laser emits spikes that form the pulse envelope with duration of 150 - 800 microsecond(s) . An extracavity PLZT 8.5/65/35 ceramics modulator (aperture of 4 X 6 mm2 and length of 18 mm) was used to obtain (Pi) -shaped segments with the rise and decay times less than 5 microsecond(s) . That allows to reduce considerably the fraction of the p…
Pulsed electric fields as an alternative to thermal processing for preservation of nutritive and physicochemical properties of beverages: A review
2017
Fruit juices and other beverages constitute an important source of bioactive compounds, but thermal processing may reduce their contents thus decreasing natural nutritive value of foods. This has been recently led to the use of non-thermal technologies, especially pulsed electric fields (PEF) as an interesting alternative to thermal pasteurization of beverages. Reported results show that PEF is a useful for pasteurization of fruit juices that can minimize changes in physicochemical and nutritional properties with retention of higher amounts of health-related phytochemicals. This study presents an overview of the effect of PEF on the physicochemical (e.g., Brix, pH, viscosity, acidity, color…
Ressources et économie agricole en France à l’âge du Bronze et au premier âge du Fer: les données carpologiques
2017
International audience; Les graines et les fruits conservés en contexte archéologique constituent un moyen direct de percevoir les ressources végétales des sociétés passées, les pratiques que celles-ci mettaient en oeuvre pour les exploiter, et donc plus particulièrement l’économie agricole. Aborder ces questions sur de grandes échelles d’espace ou de temps demande de compiler les données provenant de nombreux sites archéologiques. L’enquête nationale conduite sur « L’habitat et l’occupation des sols à l’âge du Bronze et au début de l’âge du Fer » a procuré l’occasion et les moyens de réunir la communauté des archéobotanistes (carpologues) à l’échelle nationale afin de mettre en commun nos …