Experiments and numerical results on nonlinear vibrations of an impacting hertzian contact. Part 2: random excitation

Non linear dynamic behaviour of a normally excited preloaded Hertzian contact (including possible contact losses) is investigated using an experimental test rig. It consists on a double sphere plane contact loaded by the weight of a rigid moving mass. Contact vibrations are generated by a external Gaussian white noise and exhibit vibroimpact responses when the input level is sufficiently high. Spectral contents and statistics of the stationary transmitted normal force are analysed. A single-degree-of-freedom non linear oscillator including loss of contact and Hertzian non linearities is built for modelling the experimental system. Theoretical responses are obtained by using the stationary Fokker-Planck equation and also Monte Carlo simulations. When contact loss occurrence is very occasional, numerical results shown a very good agreement with experimental ones. When vibroimpacts occur, results remain in reasonable agreement with experimental ones, that justify the modelling and the numerical methods described in this paper. The contact loss non linearity appears to be rather strong compared to the Hertzian non linearity. It actually induces a large broadening of the spectral contents of the response. This result is of great importance in noise generation for a lot of systems such as mechanisms using contacts to transform motions and forces (gears, ball-bearings, cam systems, to name a few). It is also of great importance for tribologists preoccupied to prevent surface dammage

Hybrid Session Verification through Endpoint API Generation

© Springer-Verlag Berlin Heidelberg 2016.This paper proposes a new hybrid session verification methodology for applying session types directly to mainstream languages, based on generating protocol-specific endpoint APIs from multiparty session types. The API generation promotes static type checking of the behavioural aspect of the source protocol by mapping the state space of an endpoint in the protocol to a family of channel types in the target language. This is supplemented by very light run-time checks in the generated API that enforce a linear usage discipline on instances of the channel types. The resulting hybrid verification guarantees the absence of protocol violation errors during the execution of the session. We implement our methodology for Java as an extension to the Scribble framework, and use it to specify and implement compliant clients and servers for real-world protocols such as HTTP and SMTP

FliPpr: A Prettier Invertible Printing System

When implementing a programming language, we often write a parser and a pretty-printer. However, manually writing both programs is not only tedious but also error-prone; it may happen that a pretty-printed result is not correctly parsed. In this paper, we propose FliPpr, which is a program transformation system that uses program inversion to produce a CFG parser from a pretty-printer. This novel approach has the advantages of fine-grained control over pretty-printing, and easy reuse of existing efficient pretty-printer and parser implementations

On the design of state-of-the-art pseudorandom number generators by means of genetic programming

Congress on Evolutionary Computation. Portland, EEUU, 19-23 June 2004The design of pseudorandom number generators by means of evolutionary computation is a classical problem. Today, it has been mostly and better accomplished by means of cellular automata and not many proposals, inside or outside this paradigm could claim to be both robust (passing all the statistical tests, including the most demanding ones) and fast, as is the case of the proposal we present here. Furthermore, for obtaining these generators, we use a radical approach, where our fitness function is not at all based in any measure of randomness, as is frequently the case in the literature, but of nonlinearity. Efficiency is assured by using only very efficient operators (both in hardware and software) and by limiting the number of terminals in the genetic programming implementation

Linearity in the non-deterministic call-by-value setting

We consider the non-deterministic extension of the call-by-value lambda calculus, which corresponds to the additive fragment of the linear-algebraic lambda-calculus. We define a fine-grained type system, capturing the right linearity present in such formalisms. After proving the subject reduction and the strong normalisation properties, we propose a translation of this calculus into the System F with pairs, which corresponds to a non linear fragment of linear logic. The translation provides a deeper understanding of the linearity in our setting.Comment: 15 pages. To appear in WoLLIC 201

Permutation and sampling with maximum length CA for pseudorandom number generation

In this paper, we study the effect of dynamic permutation and sampling on the randomness quality of sequences generated by cellular automata (CA). Dynamic permutation and sampling have not been explored in previous CA work and a suitable implementation is shown using a two CA model. Three different schemes that incorporate these two operations are suggested - Weighted Permutation Vector Sampling with Controlled Multiplexing, Weighted Permutation Vector Sampling with Irregular Decimation and Permutation Programmed CA Sampling. The experiment results show that the resulting sequences have varying degrees of improvement in DIEHARD results and linear complexity compared to the CA

CMOS detectors for space applications: from R&D to operational program with large volume foundry

Nowadays, CMOS image sensors are widely considered for space applications. The use of CIS (CMOS Image sensor) processes has significantly enhanced their performances such as dark current, quantum efficiency and conversion gain. However, in order to fulfil specific space mission requirements, dedicated research and development work has to be performed to address specific detector performance issues. This is especially the case for dynamic range improvement through output voltage swing optimisation, control of conversion gain and noise reduction. These issues have been addressed in a 0.35μm CIS process, based on a large volume CMOS foundry, by several joint ISAE- EADS Astrium R&D programs. These results have been applied to the development of the visible and near-infrared multi-linear imager for the SENTINEL 2 mission (LEO Earth observation mission for the Global Measurement Environment and Security program). For this high performance multi-linear device, output voltage swing improvement is achieved by process optimisation done in collaboration with foundry. Conversion gain control is also achieved for each spectral band by managing photodiode capacitance. A low noise level at sensor output is reached by the use of an architecture allowing Correlated Double Sampling readout in order to eliminate reset noise (KTC noise). KTC noise elimination reveals noisy pixels due to RTS noise. Optimisation of transistors’s dimensions, taking into account conversion gain constraints, is done to minimise these noisy pixels. Additional features have been also designed: 1) Due to different integration times between spectral bands required by mission, a specific readout mode was developed in order to avoid electrical perturbations during the integration time and readout. This readout mode leads to specific power supply architecture. 2)Post processing steps can be achieved by alignment marks design allowing a very good accuracy. These alignment marks can be used for a black coating deposition between spectral bands (pixel line) in order to minimise straight lighteffects. In conclusion a review of design improvements and performances of the final component is performed