A predictive surface profile model for turning based on spectral analysis

This article presents a predictive approach of surface topography based on the FFT analysis of surface profiles. From a set of experimental machining tests, the parameters investigated are: feed per revolution, insert nose radius, depth of cut and cutting speed. The first step of the analysis consists of normalizing the measured profiles with the feed per revolution. This results in normalized profiles with a feed per revolution and a signal period equal to 1. The effect of each cutting parameter on the surface profile is expressed as a spectrum with respect to the period length. These effects are quantified and can be sorted in descending order of importance as feed per revolution, insert nose radius, depth of cut and cutting speed. The second part of the paper presents a modeling of the surface profile using the parameters effects and one interaction. The proposed model gives the spectrum of the profile to be predicted. The inverse Fourier transform applied to the spectrum yields the expected surface profile. Measured and simulated profiles are compared for two cutting conditions and results correlate well

Surface roughness prediction in milling based on tool displacements

In this paper, an experimental device using non-contact displacement sensors for the investigation of milling tool behaviour is presented. It enables the recording of high frequency tool vibrations during milling operations. The aim of this study is related to the surface topography prediction using tool displacements and based on tool center point methodology. From the recorded signals and the machining parameters, the tool deformation is modeled. Then, from the calculated deflection, the surface topography in 3D can be predicted. In recent studies, displacements in XY plane have been measured to predict the surface topography in flank milling. In this article, the angular deflection of the tool is also considered. This leads to the prediction of surfaces obtained in flank milling as well as in end milling operations. Validation tests were carried out: the predicted profiles were compared to the measured profile. The results show that the prediction corresponds well in shape and amplitude with the measurement

Surface profile prediction and analysis applied to turning process

An approach for the prediction of surface profile in turning process using Radial Basis Function (RBF) neural networks is presented. The input parameters of the RBF networks are cutting speed, depth of cut and feed rate. The output parameters are Fast Fourier Transform (FFT) vector of surface profile for the prediction of surface profile. The RBF networks are trained with adaptive optimal training parameters related to cutting parameters and predict surface profile using the corresponding optimal network topology for each new cutting condition. A very good performance of surface profile prediction, in terms of agreement with experimental data, was achieved with high accuracy, low cost and high speed. It is found that the RBF networks have the advantage over Back Propagation (BP) neural networks. Furthermore, a new group of training and testing data were also used to analyse the influence of tool wear and chip formation on prediction accuracy using RBF neural networks

La représentation du théâtre pour la jeunesse à travers les langages documentaires

Les langages documentaires sont des outils d'aide à la recherche d'information. Ils peuvent être décrits comme un ensemble d'unités sémantiques, concepts ou vedettes, qui sont reliés entre eux pour former la structure particulière du langage documentaire. Dans ce mémoire, nous procédons à l'analyse des interactions entre concepts du domaine du théâtre afin de démontrer que les langages documentaires participent de la diffusion de stéréotypes sur le théâtre pour la jeunesse. Dans un premier temps, il s'agit de constituer un corpus de mots-clés descripteurs de ce domaine et voir de quelle façon il est représenté dans un corpus de langages documentaires. Dans un second temps, il s'agit d'analyser les notices bibliographiques d'un corpus de pièces de théâtre pour la jeunesse, réalisées par des professionnels du théâtre et par des professeurs-documentalistes afin d'infirmer ou de confirmer les résultats perçus dans la première analyse

A study of an Olympic champion's training program for the mile or 1,500 meters.

Thesis (M.A.)--Boston Universit

Exploiting Redundant Designs with Side-Channel Attacks

Sidekanalsangrep (SKA) er en bred angrepsklasse der en angriper utnytter en uforventet informasjonslekkasje til å omgå et sikkerhetstiltak. Hvorfor skulle man orke å knekke en kryptert telefonsamtale når man kan stå i naborommet og lytte gjennom veggen? I en kryptografikontekst lar SKA en ondsinnet aktør komme seg rundt den teoretiske sikkerheten til personvernsalgoritmene, derfor har forskere viet mye tid og krefter til å studere og sette inn tiltak mot slike angrep. Som en del av dette arbeidet har kryptografer blir kryptoanalytikere: de har tatt på seg rollen som den ondsinnede aktøren for å prøve å konstruere sterkest mulige angrep, for å på denne måten få en bedre forståelse for hvordan det er mulig å beskytte algoritmer mot disse angrepene. Vi antar den samme rollen i denne avhandlingen, og fokuserer på strøm-baserte angrep. Disse er særlig skadelige siden de utnytter en fysisk effekt av mikroprosessorer som ikke kan unngås. De blir også stadig mer relevante etter hvert som samfunnet liter mer og mer på sammenkoblede enheter. For eksempel førte eksplosjonen av Tingenes internett eller skyberegning til lignende økninger av nye kryptografiske utforminger. Blant disse undersøkte vi motstandskraften mot sidekanaler hos de utformingene som bruker redundans direkte i beregningene. Mens mange kryptografer kan ha ansett redundans som kostnadsfritt fra et sikkerhetsperspektiv, ønsket vi å vise at når SKA er i bildet kommer redundans med potensielle sikkerhetsmessige haker, og avveiinger kan ikke unngås. I den første artikkelen vår ser vi på et tiltak mot SKA, polynomiell maskering, som bruker redundans som et verktøy for å beskytte mot passive og aktive SKA samtidig. Polynomiell maskering har blitt studert tidligere, og hovedresultatet forut for denne avhandlingen pekte mot at redundans ikke påvirker sikkerheten. Vi viser det motsatte. For hver redundant del brukt i maskeringssystemet, viser vi empirisk at sikkerheten degraderer alvorlig. Videre viser vi påvirkningen interpoleringsmengden har på sikkerheten av systemet, og kobler flere populære maskeringssystemer sammen. I den andre artikkelen vår angriper vi blokkchifferet SKINNY, et nylig publisert justerbart blokkchiffer. Vi vister at den sakte diffusjonsformen av SKINNY fører til høy redundans av de mellomliggende variablene en SKA angriper kan utnytte for å forsterke angrepet. For å utnytte denne redundansen introduserer vi et nytt angrep ved navn Klyngegrafinferens-Differensiell strømanalyse (KGI-DSA) som bruker verktøy fra probabilistisk grafteori. Vi viser kraften av det nye angrepet vårt ved å angripe flere implementeringer av SKINNY.Side-Channel Attacks (SCA) are a broad class of attacks that exploit an unexpected leakage of information, allowing an attacker to side-step a security measure. Why would you go through the trouble of cracking an encrypted phone call if you could stand in the room next door and listen through the walls? In the context of cryptography, SCAs allow a malicious actor to get around the theoretical security of the algorithms that protect our privacy, which is why researchers have dedicated a lot of effort to studying and building protections against these attacks. Among those efforts, cryptographers turn cryptanalysts: they take upon the role of the malicious adversary and try to craft the strongest possible attacks to better understand how to protect against them. This role is also the one we assume in this thesis, with a focus on power-based attacks. These are particularly pernicious since they exploit a physical effect of microprocessors which can hardly be prevented. They are also becoming more relevant than ever as our society relies more and more on connected devices. For example, the explosion of the Internet-of-Things or cloud computing, led to a corresponding expansion of new cryptographic designs. Amongst these new designs, we investigated the resistance against side-channels of those that make explicit use of redundancy in their computations. While many cryptographic designers might have considered redundancy to be costless from a security standpoint, we wanted to show that when SCAs are in the picture, redundancy comes with potential security drawbacks and trade-offs that cannot be avoided. In our first paper, we study a countermeasure to SCAs, polynomial masking, which uses redundancy as a tool to simultaneously protect against passive and active SCAs. Polynomial masking has previously been studied and the main result before this thesis pointed in the direction of redundancy bearing no influence on security. We show the opposite. For every redundant share used in the masking scheme, we empirically show that the security degrades severely. Furthermore, we point out the influence of the choice of the interpolation set on the security of the scheme and link several popular masking schemes together. In our second paper, we attack the blockcipher SKINNY, a recently published tweakable blockcipher. We demonstrate that the slow diffusion design of SKINNY leads to a high redundancy of intermediate variables that an SCA attacker can leverage to build a stronger attack. To exploit this redundancy we introduce a new attack, dubbed Cluster Graph Inference-Differential Power Analysis (CGI-DPA) that uses tools from the field of probabilistic graphical theory. We demonstrate the efficacy of our new attack by attacking multiple implementations of SKINNY.Doktorgradsavhandlin

CHANCE: A FRENCH-GERMAN HELICOPTER CFD-PROJECT

The paper gives an overview of the CHANCE research project (partly supported by the French DPAC and DGA and the German BMWA) which was started in 1998 between the German and French Aerospace Research Centres DLR and ONERA, the University of Stuttgart and the two National Helicopter Manufacturers, Eurocopter and Eurocopter Deutschland. The objective of the project was to develop and validate CFD tools for computing the aerodynamics of the complete helicopter, accounting for the blade elasticity by coupling with blade dynamics. The validation activity of the flow solvers was achieved through intermediate stages of increasing geometry and flow modelling complexity, starting from an isolated rotor in hover, and concluding with the time-accurate simulation of a complete helicopter configuration in forward-flight. All along the research program the updated versions of the CFD codes were systematically delivered to Industry. This approach was chosen to speed up the transfer of capabilities to industry and check early enough that the products meet the expectations for applicability in the industrial environment of Eurocopter

An Innovative Experimental Study of Corner Radius Effect on Cutting Forces

The cutting forces are often modelled using edge discretisation methodology. In finish turning, due to the smaller corner radii, the use of a local cutting force model identified from orthogonal cutting tests poses a significant challenge. In this paper, the local effect of the corner radius on the forces is investigated using a new experimental configuration: corner cutting tests involving the tool nose. The results are compared with inverse identifications based on cylindrical turning tests and elementary cutting tests on tubes. The results obtained from these methods consistently show the significant influence of the corner radius on the cutting forces