Drift Correction Methods for gas Chemical Sensors in Artificial Olfaction Systems: Techniques and Challenges

In this chapter the authors introduce the main challenges faced when developing drift correction techniques and will propose a deep overview of state-of-the-art methodologies that have been proposed in the scientific literature trying to underlying pros and cons of these techniques and focusing on challenges still open and waiting for solution

Design Issues and Challenges of File Systems for Flash Memories

This chapter discusses how to properly address the issues of using NAND flash memories as mass-memory devices from the native file system standpoint. We hope that the ideas and the solutions proposed in this chapter will be a valuable starting point for designers of NAND flash-based mass-memory devices

Simulation and Calibration of the ALICE TPC including innovative Space Charge Calculations

ALICE is one of the four main particle detectors located around the LHC accelerator at CERN. It is particularly designed to study the physics of the quark-gluon plasma by means of nucleus--nucleus collisions at center-of-mass energies up to 5.5 TeV per nucleon pair. A Time-Projection Chamber (TPC) was chosen to be its central-sub-detector due to its low mass properties and its capabilities to provide a robust and accurate Particle Identification even within ultra-high multiplicity environments (up to 8000 tracks per unit of eta). To achieve the required physics performance, the space point resolution of the TPC must be in the order of 0.2 mm. Due to its gigantic size of 5~m in diameter and 5~m in length, corrections for static as well as dynamic effects are indispensable in order to accomplish the design goal. The research presented covers all major issues relevant for the final calibration and therefore the enhancement of the TPC performance in terms of resolution. The main focus was to distinguish between the different effects which disturb the electron trajectory within the drift volume by means of quantifying the magnitude of their influences. The effects were parametrized in terms of physical parameters, as opposed to a multivariate fit, in order to minimize the residuals of the cluster positions. The different chapters of the present research work cover static imperfections, like magnetic and electric field inhom ogeneities due to mechanical imperfections, as well as dynamic variations of the drift properties due to pressure, temperature and gas composition variations which manifest themselves as gas density fluctuations. Furthermore, additional challenges were treated which will occur in future high multiplicity nucleus-nucleus collisions. These are the improvement of the two-track resolution as well as the quantification of additional dynamic field deviations due to space charges. Various simulation techniques were used to qualify and quantify the field imperfections due to mechanical deficiencies. Besides the localization and calibration of the field imperfections, the simulations led to optimized voltage settings which minimize the residuals. The different drift velocity v_d dependencies were parametrized to allow a quick estimation of the dynamic $v_d$ variations as a function of the measured ambient conditions. Besides that, the programmable signal shaping algorithm within the Front-End electronics was revised. This is expected to improve the two-track resolution in high multiplicity events. Moreover, novel analytical solutions were derived to allow a fast and precise prediction of additional dynamic field deviations due to ionic-charge pile up within the TPC gas volume. This analytic approach finally permits accurate simulations of additional systematic shifts along the electron trajectory due to any three dimensional space c harge distribution within the TPC. This innovative method is an essential part of the calibration algorithms which are being developed for the future Pb-Pb collisions at LHC

Afterlive: A performant code for Vlasov-Hybrid simulations

A parallelized implementation of the Vlasov-Hybrid method [Nunn, 1993] is presented. This method is a hybrid between a gridded Eulerian description and Lagrangian meta-particles. Unlike the Particle-in-Cell method [Dawson, 1983] which simply adds up the contribution of meta-particles, this method does a reconstruction of the distribution function $f$ in every time step for each species. This interpolation method combines meta-particles with different weights in such a way that particles with large weight do not drown out particles that represent small contributions to the phase space density. These core properties allow the use of a much larger range of macro factors and can thus represent a much larger dynamic range in phase space density. The reconstructed phase space density $f$ is used to calculate momenta of the distribution function such as the charge density $\rho$. The charge density $\rho$ is also used as input into a spectral solver that calculates the self-consistent electrostatic field which is used to update the particles for the next time-step. Afterlive (A Fourier-based Tool in the Electrostatic limit for the Rapid Low-noise Integration of the Vlasov Equation) is fully parallelized using MPI and writes output using parallel HDF5. The input to the simulation is read from a JSON description that sets the initial particle distributions as well as domain size and discretization constraints. The implementation presented here is intentionally limited to one spatial dimension and resolves one or three dimensions in velocity space. Additional spatial dimensions can be added in a straight forward way, but make runs computationally even more costly.Comment: Accepted for publication in Computer Physics Communication