Décentralisation : l'exigence du débat.

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Qucs: an introduction to the new simulation and compact device modelling features implemented in release 0.0.19/0.0.19Src2 of the popular GPL circuit simulator.

Following the release of Qucs-0.0.18 in August 2014 the Qucs Development Team have considered in detail a number of possible directions that future versions of the software could take. Spice4qucs is one of these routes. Spice4qucs is a Qucs extension that allows Qucs schematics, including non-linear Equation-Defined Device compact models, to be simulated with external SPICE-compatible simulation engines. Qucs-0.0.19Src2 uses ngspice and Xyce for this purpose. The recent release of Qucs-0.0.19Src2 includes the latest spice4qucs extensions and is made available as an experimental feature. All Qucs legacy simulation and modelling features remain unchanged. The spice4qucs extensions introduce in release Qucs-0.0.19Src2 include the majority of the SPICE components distributed with the ngspice and Xyce circuit simulation packages. Circuits can be simulated with Qucs qucsator, ngspice and Xyce in particular circuit investigations can be centred around SPICE, .FOUR, .NOISE, and .DISTO analysis, a SPICE compatible parametrization system employing the SPICE .PARAM statement, SPICE behavioural sources, ngnutneg scripts, and an innovative form of Qucs simulation called “Custom Simulation”. The“Custom Simulation” facility allows uses to develop ngnutmeg scripts for circuit design, compact device modelling, Monte-Carlo simulation (and other related circuit statistical routines) and to process simulation output data. Combinations of these new features significantly increases Qucs simulation and modelling capabilities, particularly in established areas like power/RF electronics and new emerging technologies. Qucs-0.0.19Src2 also introduces a preliminary version of a new Qucs EDD to Verilog-A compact model synthesis tool. This feature is released as a GPL open source software tool in support of current compact modelling research

Building a second generation Qucs GPL circuit simulator: package structure, simulation features and compact device modelling capabilities

In 2013 a new Qucs development team started work on an extended version of the popular Qucs GPL circuit simulator. The second generation development team undertook the task of eliminating a number of bugs in the Qucs software, improving its performance and extending its capabilities into new circuit and simulation domains. This presentation outlines the most important changes that have taken place with Qucs releases 0.0.17 and 0.0.18. These include, GUI and Qucssator improvements, post-simulation data processing using Qucs, Octave and Python, compact semiconductor modelling with equation-defined devices and Verilog-A code models and the introduction of a non-linear differential equation library and Octave/Matlab interface. Throughout the presentation a number of behavioural models for two and three terminal devices are introduced and their performance evaluated with data obtained from simulation tests undertaken with the Qucs and Xyce GPL circuit simulators

Model Channel Ion Currents in NaCl - SPC/E Solution with Applied-Field Molecular Dynamics

Using periodic boundary conditions and a constant applied field, we have simulated current flow through an 8.125 Angstrom internal diameter, rigid, atomistic channel with polar walls in a rigid membrane using explicit ions and SPC/E water. Channel and bath currents were computed from ten 10-ns trajectories for each of 10 different conditions of concentration and applied voltage. An electric field was applied uniformly throughout the system to all mobile atoms. On average, the resultant net electric field falls primarily across the membrane channel, as expected for two conductive baths separated by a membrane capacitance. The channel is rarely occupied by more than one ion. Current-voltage relations are concentration-dependent and superlinear at high concentrations.Comment: Accepted for publication in Biophysical Journa

QUCS/ADMS/Verilog-A Update

The QUCS is a popular GPL circuit simulator. The second generation development team undertook the task of eliminating a number of bugs in the Qucs software, improving its performance and extending its capabilities into new circuit and simulation domains. This presentation outlines the most important changes which include, GUI and Qucssator improvements, post-simulation data processing using Qucs, Octave and Python, compact semiconductor modelling with equation-defined devices and Verilog-A code models and the introduction of a non-linear differential equation library and Octave/Matlab interface. Throughout the presentation a number of behavioural models for two and three terminal devices are introduced and their performance evaluated with data obtained from simulation tests undertaken with the Qucs and Xyce GPL circuit simulators

Comparison of charged sheets and corrected 3D Ewald calculations of long-range forces in slab geometry electrolyte systems with solvent molecules

Two methods of calculating long-range intermolecular potentials are compared for an approximately 3 M aqueous electrolyte solution confined between two charged surfaces. We investigate the ionic density profiles using the charged sheets method and the corrected-3-D Ewald method at two different system sizes and also compare the Coulomb forces directly. The corrected-3-D Ewald method is recommended for the calculation of long-range potentials in systems of this nature because it is less system size dependent than the charged sheets method and the resultant forces are more consistent with periodic boundaries. However, the charged sheets method for estimating long-range potentials in coulombic systems may be useful for certain applications, and the corrected-3-D Ewald method also shows some system size vulnerability