All-Optical Reinforcement Learning in Solitonic X-Junctions

L'etologia ha dimostrato che gruppi di animali o colonie possono eseguire calcoli complessi distribuendo semplici processi decisionali ai membri del gruppo. Ad esempio, le colonie di formiche possono ottimizzare le traiettorie verso il cibo eseguendo sia un rinforzo (o una cancellazione) delle tracce di feromone sia spostarsi da una traiettoria ad un'altra con feromone più forte. Questa procedura delle formiche possono essere implementati in un hardware fotonico per riprodurre l'elaborazione del segnale stigmergico. Presentiamo qui innovative giunzioni a X completamente integrate realizzate utilizzando guide d'onda solitoniche in grado di fornire entrambi i processi decisionali delle formiche. Le giunzioni a X proposte possono passare da comportamenti simmetrici (50/50) ad asimmetrici (80/20) utilizzando feedback ottici, cancellando i canali di uscita inutilizzati o rinforzando quelli usati.Ethology has shown that animal groups or colonies can perform complex calculation distributing simple decision-making processes to the group members. For example ant colonies can optimize the trajectories towards the food by performing both a reinforcement (or a cancellation) of the pheromone traces and a switch from one path to another with stronger pheromone. Such ant's processes can be implemented in a photonic hardware to reproduce stigmergic signal processing. We present innovative, completely integrated X-junctions realized using solitonic waveguides which can provide both ant's decision-making processes. The proposed X-junctions can switch from symmetric (50/50) to asymmetric behaviors (80/20) using optical feedbacks, vanishing unused output channels or reinforcing the used ones

Role of the cell surface in neuronal pathfinding

Journal ArticlePerhaps the organ of the human body that evokes the most astonishment, and yet is the least understood, is our brain. From the coordination of simple movements, to consciousness and thought, the function of the nervous system relies on the establishment of trillions of precise connections among the many neurons that constitute it

A study of laser plasmas as X-ray sources in the 1-10 keV spectral region

An experimental investigation on X-ray emission from laser-produced plasmas is presented and the properties of such an emission of interest for application purposes are examined. Plasmas were generated by focusing 1 μm, 3 ns Nd laser pulses onto Al and Cu targets at an intensity of 1013 W/cm2. The temporal evolution of the emission and its spectral features were investigated by using an X-ray streak-camera and an X-ray photodiode. In the case of Cu targets, the analysis of the emission showed two spectral components. The main component was centered at ≈ 1.2 keV and a minor component, whose intensity was measured to be 10-3 of the previous component, was observed at ≈7 keV. The X-ray conversion efficiency, in the investigated spectral region, was measured to be 1% for Cu targets and 0.3% for Al targets

CFD Simulation of Anaerobic Granular Sludge Reactors: A Review

Anaerobic digestion processes can generate renewable energy in the form of biogas while treating organic wastewater. The generation of biogas within anaerobic digestion systems is directly linked to the mixing conditions inside the reactors. In high-rate reactors such as the up-flow anaerobic sludge blanket (UASB) reactor, the expanded granular sludge bed (EGSB) reactor and the internal circulation (IC) reactor, the hydrodynamic behaviour will depend on the interactions between the wastewater, the biogas, and the biomass granules. Over the past few years, various researchers have used computational fluid dynamics (CFD) to study the hydrodynamic behaviour in these types of reactors. This review aims to present and critically discuss the state of the art in the use of CFD applied to anaerobic granular sludge reactors (AGSRs). It briefly introduces and discusses the various aspects of modelling. It also reviews the various papers which used CFD to model these reactors and critically analyses the models used for the simulations in terms of general approaches and single-phase vs multiphase studies. The methods used in the validation of the CFD models are also described and discussed. Based on the findings, the challenges and future perspectives for the CFD modelling of AGSRs are discussed and gaps in the knowledge are identified

An overview on the Irish Breweries and distilleries potential for generating bioenergy through the anaerobic digestion of the wastewater

This work presents an overview on the potential for generating bioenergy through the anaerobic digestion of the Irish breweries and whiskey distilleries effluents. The results showed that it would be possible to generate 28,210,958 Nm3/year of biogas or 154,846 MWh of thermal heat with 110,715 tonnes of CO2 savings in a year. The electricity generation potential and CO2 savings were also calculated. It was possible to conclude that the anaerobic digestion of the wastewater from the brewery and distillery industries stand out as a feasible option to increase the share of renewable energies in Ireland

Development & Validation of a PIV System for Obtaining Data from a UASB Reactor

Anaerobic digestion processes can generate energy in the form of biogas while treating organic wastewater. The efficiency of the treatment, and thus the generation of biogas, is closely linked to the type and design of the reactor, and the technology used. Granular anaerobic digestion technology offers advantages such as a higher loading rate and reduction of the space needed. However, the hydrodynamics inside this type of reactor can be complex due to the presence of solids (granules) and gas (biogas) phases along with the liquid phase (wastewater). This is one of the reasons why the study and optimization of reactors using bench-scale reactors can lead to inaccurate results. A validated computational model would lead to the possibility of performing optimization studies using simulation; however, the validation of these computational models cannot be performed using analytical solutions due to their complexity. In this context, a particle image velocimetry (PIV) experimental setup was validated as part of this work, using computational fluid dynamics (CFD) simulations and data from literature. The experimental results obtained were compared with CFD results from six different models, each using a different turbulence model. The current setup was considered validated, allowing it to be used in the future for obtaining experimental data for the validation of a CFD model of an up-flow anaerobic sludge blanket reactor (UASB)

The groupoidal analogue Theta~ to Joyal's category Theta is a test category

We introduce the groupoidal analogue \tilde\Theta to Joyal's cell category \Theta and we prove that \tilde\Theta is a strict test category in the sense of Grothendieck. This implies that presheaves on \tilde\Theta model homotopy types in a canonical way. We also prove that the canonical functor from \Theta to \tilde\Theta is aspherical, again in the sense of Grothendieck. This allows us to compare weak equivalences of presheaves on \tilde\Theta to weak equivalences of presheaves on \Theta. Our proofs apply to other categories analogous to \Theta.Comment: 41 pages, v2: references added, Remark 7.3 added, v3: metadata update

Femtosecond Laser-Produced Plasma X-Rays from Periodically Modulated Surface Targets

We have studied theoretically and experimentally the x-ray production above 1 keV from femtosecond laser plasmas generated on periodically modulated surface targets. Laser energy coupling to plasma surface waves has been modeled using a numerical differential method. Almost total absorption of incident laser radiation is predicted for optimized interaction conditions. Silicon gratings have been irradiated by a 120fs Ti:sapphire laser at irradiances in excess of 1016 W/cm2. X-ray intensities above 1.5 keV (K-shell lines) have been measured as a function of the incidence angle. Results show a distinct x-ray emission maximum for the first order diffraction angle and are in good qualitative agreement with our theoretical predictions

Multiphase CFD modelling and PIV validation of a UASB reactor

Upflow anaerobic sludge blanket (UASB) reactors stand out as a feasible option for treating wastewaters while generating a valuable amount of biogas. It is known that the efficiency of UASB reactors is closely linked to its hydrodynamics. Therefore, understanding the role of each phase (solids, liquid and gas) in the mixing conditions inside the reactor and having validated numerical models for predicting the flow behavior has become fundamental for the design and optimization of UASB reactors. In this context this work aims to develop and validate a three phase Computational Fluid Dynamics (CFD) model of an UASB reactor. Eulerian-Eulerian laminar three-dimensional multiphase simulations were carried out using Fluent 16.2. The model was validated using Particle Image Velocimetry (PIV) experiments. The reactor was divided into four regions, according to its mixing conditions. Validation results showed differences between experimental and computational results for the liquid velocity to be less than 4%. Dead zones accounted for 0.02% of the total volume of the reactor. From the simulation results, a sludge wash out of 179 mg·L−1 was found. The validated model can be further used for optimization studies for this type of wastewater treatment bioreactor