Proving the Fidelity of Simulations of Event-B Models

International audienceA major hindrance to the use of formal methods is the difficulty to validate the models, particularly at the early stages of the development. We propose to build simulations: programs automatically generated from the specifications but with user-provided implementations of the non-executable traits of the models. We present such a simulation. Of course, the question of the fidelity of the simulation to the model is raised in such a setting. We provide a formal definition of fidelity and the proof obligations that can be attached to each hand-coded element so that fidelity can be proven

The Road to Quantum Computational Supremacy

We present an idiosyncratic view of the race for quantum computational supremacy. Google's approach and IBM challenge are examined. An unexpected side-effect of the race is the significant progress in designing fast classical algorithms. Quantum supremacy, if achieved, won't make classical computing obsolete.Comment: 15 pages, 1 figur

Event-by-event Simulation of Quantum Cryptography Protocols

We present a new approach to simulate quantum cryptography protocols using event-based processes. The method is validated by simulating the BB84 protocol and the Ekert protocol, both without and with the presence of an eavesdropper

Quantum memories based on engineered dissipation

Storing quantum information for long times without disruptions is a major requirement for most quantum information technologies. A very appealing approach is to use self-correcting Hamiltonians, i.e. tailoring local interactions among the qubits such that when the system is weakly coupled to a cold bath the thermalization process takes a long time. Here we propose an alternative but more powerful approach in which the coupling to a bath is engineered, so that dissipation protects the encoded qubit against more general kinds of errors. We show that the method can be implemented locally in four dimensional lattice geometries by means of a toric code, and propose a simple 2D set-up for proof of principle experiments.Comment: 6 +8 pages, 4 figures, Includes minor corrections updated references and aknowledgement

Driving stability of passenger vehicles under crosswinds

Passenger cars are a vital part of modern society, giving people the freedom of flexible travel. As technology advances, customers increase their demands for future products. The automotive industry must, therefore, adapt to society\u27s requirements of energy-efficient travel, where developing low drag vehicles is key. However, if not designed with care, streamlined bodies of low drag might impair driving stability. In addition, raised customer demands of perceived control and stability elevate the research needs on driving stability in crosswinds.Vehicles travelling on open roads are always exposed to the changing crosswind conditions. Most road vehicles have the aerodynamic centre of pressure located at the front half of the vehicle, making them sensitive to these crosswinds. Strong winds and sensitive vehicle designs may degrade the perceived level of driving stability by drivers and passengers. In extreme winds, this can even cause accidents. Furthermore, the aerodynamic loads increase with flow velocity, deteriorating the driving stability performance at higher speeds.The assessment of driving stability in the development of a new vehicle is often done at the test tracks during late design phases when prototype vehicles are available. However, the current demands of faster development times require robust virtual methods for assessing the stability performance in early design phases. The goal of this thesis is, therefore, to find virtual simulation tools for assessing straight-line driving stability, and to gain more insights on the interdisciplinary physics between aerodynamics and vehicle dynamics.By conducting experimental on-track measurement, it was confirmed that crosswinds deteriorate the driving stability and that the vehicle motions of lateral acceleration and yaw velocity correlate with the drivers\u27 subjective assessment. These motions were combined into a proxy measure for stability, later used for objective assessment in the numerical simulations. The numerical study employed a coupled simulation methodology between aerodynamics and vehicle dynamics. It was shown that a 1-way coupling was sufficient for passenger vehicles in normal wind conditions.Furthermore, the aerodynamic loads, including the yaw moment overshoots during transient gust events, could accurately be predicted by a quasi-steady model accounting for the phase delay between axles when driving into crosswinds. An extensive parametric study highlighted the aerodynamic yaw moment coefficient and the longitudinal centre of gravity position as the two most influential vehicle parameters. In addition, the suspension characteristics revealed potential in improving the driving stability performance under crosswinds

Developing satellite ground control software through graphical models

This paper discusses a program of investigation into software development as graphical modeling. The goal of this work is a more efficient development and maintenance process for the ground-based software that controls unmanned scientific satellites launched by NASA. The main hypothesis of the program is that modeling of the spacecraft and its subsystems, and reasoning about such models, can--and should--form the key activities of software development; by using such models as inputs, the generation of code to perform various functions (such as simulation and diagnostics of spacecraft components) can be automated. Moreover, we contend that automation can provide significant support for reasoning about the software system at the diagram level

Shaped Charge Jet Penetration of Alon® Ceramic Assessed by Proton Radiography and Computational Simulations

AbstractThis work describes the use of proton radiography and continuum simulations to investigate the mechanics of a copper jet penetrating unconfined ALON® transparent ceramic. Use of proton radiography enabled characterization of the jet and ceramic material at 21 time steps, in situ, throughout the penetration process. These radiographs provide time-evolution data pertaining to the material densities, cavity growth, and material failure. The data were compared to legacy analytical penetration models and to a simulation of the event computed using a continuum multi-physics code. These comparisons revealed additional insights into the penetration mechanics as well as strengths and weaknesses of the computational algorithms and material models used in the simulations