Littérature scientifique sur le sujet « Ω-automates »

This review paper gives Excel functions for highly precise Colebrook’s pipe flow friction approximations developed by users. All shown codes are implemented as User Defined Functions – UDFs written in Visual Basic for Applications – VBA, a common programming language for MS Excel spreadsheet solver. Accuracy of the friction factor computed using nine to date the most accurate explicit approximations is compared with the sufficiently accurate solution obtained through an iterative scheme which gives satisfying results after sufficient number of iterations. The codes are given for the presented approximations, for the used iterative scheme and for the Colebrook equation expressed through the Lambert W-function (including its cognate Wright ω-function). The developed code for the principal branch of the Lambert W-function has additional and more general application for solving different problems from variety branches of engineering and physics. The approach from this review paper automates computational processes and speeds up manual tasks.

For this study, a substitution principle-based impedance bridge has been developed to calibrate AC resistors in a four-terminal-pair (4TP) configuration. The calibration is performed in the full complex plane for resistances ranging from 100 mΩ to 400 Ω and frequencies of between 50 Hz and 20 kHz. The automated bridge is based on four resistors associated with two high-impedance stages. The balancing of the bridge is achieved by means of PXI modules. The bridge is automatically balanced via a simplex top-down algorithm. The new bridge is primarily used for the measurement chain of AC standard resistors defined in a 4TP configuration at LNE, which are used for routine customer calibrations. The traceability of LNE’s standard resistors when defined in a 4TP configuration is ensured by a measurement chain from a 1 kΩ reference resistor using the new bridge. The reference resistor was calibrated previously via comparison with a calculable resistor up to 20 kHz. The bridge was validated via comparison with calibration results obtained in 1983 and 2009. For a resistor of 1 Ω at 1 kHz, the uncertainty of the series resistance variation and the phase shift are less than 6 µΩ/Ω (k = 1) and 6 µrad (k = 1), respectively.

This paper focuses on the problem of measuring stream power in a hydrographic network using the original definition provided by Bagnold in 1996. Recent digital elevation models have enabled the calculation of channel gradients and, consequently, stream power with a finer spatial resolution, and this has created promising and novel opportunities to investigate river geomorphological processes and forms. The work carried out in this study includes defining and implementing a methodological approach that could be automated within a geographic information system and that meets two requirements: (1) it uses a DEM as input data at a suitable resolution; (2) it estimates the stream power Ω , as well as its variability along the considered stream, in the best possible way using available data. In particular, the methodological approach was implemented in a GIS environment (GRASS GIS) and applied to a sample basin to highlight the variability in Ω along the main stream and its most important tributaries. The sudden and more substantial variations in stream power were then related to the processes acting in the fluvial system. This approach made it possible to highlight how erosion, solid transport, and sedimentation phenomena occurring along the fluvial reaches are related to abrupt variations (increase/decrease) in the “power” available. The results of this study support the idea that the automated and standardized screening of stream power variability along a stream can be used as a preliminary diagnostic element to identify the most “sensitive” points of the stream on which to concentrate subsequent investigations (field checks to verify the causes), with the aim of mitigating risks due to the dynamics of the riverbed.

The objective of the study was to compare and reveal differences in basic chemical parameters, fatty acids, amino acids, and lipid quality indices of crossbred buffalo (swamp x river type) milk produced in summer and winter. The buffalo milk samples were collected in summer (Jul–Aug) and winter (Dec–Jan) from Hubei province, China. The samples were detected by using CombiFoss apparatus, gas chromatography, and an automated specialized amino acid analyzer. The results showed that the basic chemical parameters, fatty acid profiles, lipid quality indices, and amino acid profiles of crossbred buffalo milk differed between summer and winter. Specifically, summer buffalo milk exhibited a higher content of MUFA (monounsaturated fatty acids) and PUFA (polyunsaturated fatty acids) than winter buffalo milk. Summer buffalo milk had a lower content of major SFA (saturated fatty acids), a higher content of ω-3 and DFA (hypocholesterolemic fatty acids), a lower ω-6/ω-3 ratio, a higher value of 3 unsaturated fatty acid indices (C14, C16, C18), and a lower value of IA (index of atherogenicity) and IT (index of thrombogenicity) than winter buffalo milk. Additionally, 17 amino acids, including 8 EAA (essential amino acids) and 9 NEAA (non-essential amino acids) were higher in summer buffalo milk. These results indicated that summer buffalo milk was more health-beneficial than winter buffalo milk. Therefore, summer buffalo milk might be a desirable diet option for human nutrition and health. Our findings provide valuable information for the research and development of buffalo dairy products in China or other Asian countries.

In this paper we will present a development of Measurement system for accurate comparison of low resistance standards and AC shunts ranging from 0.1 mΩ to 10 Ω as well as system testing and use. The system consists of a specially built current source, range selector, current reversal module and low cost analog to digital converter. The entire measurement procedure is automated and controlled by LabVIEW program. Subsequent testing has shown that the realized precision resistance measurement system has achieved precision comparable to more expensive commercial devices. The system or system elements can be used both in smart grid applications and in military laboratories for testing new technologie.

Abstract. We established a new laboratory for noble gas mass spectrometry that is dedicated to the development and application to cosmogenic nuclides at the University of Cologne (Germany). At the core of the laboratory are a state-of-the-art high-mass-resolution multicollector Helix MC Plus (Thermo Fisher Scientific) noble gas mass spectrometer and a novel custom-designed automated extraction line. The mass spectrometer is equipped with five combined Faraday multiplier collectors, with 1012 and 1013 Ω pre-amplifiers for faraday collectors. We describe the extraction line and the automated procedure for cosmogenic neon and the current performance of the experimental set-up. Performance tests were conducted using gas of atmospheric isotopic composition (our primary standard gas), as well as CREU-1 intercomparison material, containing a mixture of neon of atmospheric and cosmogenic composition. We use the results from repeated analysis of CREU-1 to assess the performance of the current experimental set-up at Cologne. The precision in determining the abundance of cosmogenic 21Ne is equal to or better than those reported for other laboratories. The absolute value we obtain for the concentration of cosmogenic 21Ne in CREU is indistinguishable from the published value.

A new grazing-incidence diffraction (GID) measurement geometry between in plane and out of plane is proposed. It is improved from the previous ω–φ compensated GID in side-inclination mode for measurement of residual stress in polycrystalline thin films [Wang & van Riessen (2017). Powder Diffr. 32, S9–S15]. Instead of keeping a constant azimuthal direction of the incident beam on the thin film sample, the current proposed variation maintains a constant azimuthal direction of the scattering vector projection on the thin film sample. The variation is named `ω–φ′ compensated GID in side-inclination mode' and enables d-spacing measurements along the same azimuthal direction. An Excel spreadsheet is included for readers to plan the measurement and to calculate the residual stress for the planned sample azimuthal direction. Anisotropic residual stresses of a polycrystalline NiFe thin film on an Si 001 substrate are measured by combining this method with phi rotations. Highly automated data analysis templates are developed using DIFFRAC.TOPAS v7 launch mode to calculate residual stress for all planned azimuthal directions sequentially. A pole figure file in simple text format is also generated from the same data set using DIFFRAC.TOPAS v7 launch mode, and can be directly imported into DIFFRAC.TEXTURE v4.1 for further texture analysis. Corrections for the incident-beam refraction have been implemented in both data analysis models.

In the continuous mills, where the strip thickness at the entrance contains a high-frequency component caused by the eccentricity of the rolls of the previous cage, the effectiveness of AGC-systems for regulating the thickness of the rolled product depends on the speed of operation of hydraulic roll setting devices (HRSD). Analytical substantiation of the transfer functions of the AGC-system by the eccentricity of the rolls and by the thickness of the undercut, taking into account the real speed of the HRSD has been carried out. The frequency characteristics of the AGC-system are analytically determined. It has been proven that with the available speed of the HPD in the interval of rotation frequencies of the support rolls inherent in cold rolling (ω= 5 – 15 s-1), the amplitude-frequency characteristic (AFC) of the AGC-system is almost linear. AFC depending on the time constant T of the HRSD and the ratio of the modulus of rigidity of the rolling strip MΠ to the modulus of rigidity of the rolling stand МK varies within wide limits from A(5)=0.05 (at ω = 5s-1; T=0.01 s; MΠ/MK = 1) to A(15)=0.48 (at ω = 15 s-1; T = 0.01 s; MΠ/MK = 4). At the same time, the thickness variation at the outlet of the cage meets the requirements for thin cold-rolled products of high precision. It has been proved that under the conditions of regulation of the thickness of the rolling strip according to the AGC-algorithm the amplitude of the oscillations of the rolled thickness caused by the eccentricity of the rolls is smaller than the amplitude of the oscillations of the roll gap caused by the eccentricity and decreases with an increase in the rotation frequency of the rolls and the time constant of the HRSD according to a close to linear law. Such linearity creates the basis for the application of adaptive algorithms for determining the actual amplitude of fluctuations of the roll gap in automated systems for compensating the eccentricity of the rolls.

This paper proposes a method for optimizing and designing a wireless power transfer system operating at 13.56 MHz. It can be used as guidelines for designing coils for the new-trending technology that enables NFC devices to not only to communicate but also to charge. Since NFC wireless charging is an emerging technology, it is of interest to propose optimizations and a dedicated circuit design for such systems. This work proposes an optimization procedure to calculate the dimensions of a transmitter and receiver pair that assures the highest efficiency while considering all possible positions of a receiver that is placed on a desired surface. This procedure seeks to facilitate and automate the design of rectangular-shaped coils, whereas the literature proposes mainly square-shaped coils. Afterwards, a circuit analysis was conducted, and the series-parallel compensation network is proposed as the most promising topology of the receiver to assure a low efficiency sensibility to load variations for 13.56 MHz wireless power transfer systems. A pair of optimized transmitter and receiver coils is prototyped, and the experimental results are tested against the theory. The transmitter of 7 cm×11.4 cm and receiver of 4 cm ×4 cm are separated by 10 mm. The receiver can move on a surface of 8 cm ×12 cm and the load can vary from 36 Ω to 300 Ω while assuring a minimum and maximum efficiency of 80% and 88.3%, respectively.

La synthèse vise à produire un système correct à partir de spécifications. Une approche pour résoudre ce problème consiste à traduire la spécification en un jeu de parité dont la stratégie gagnante encode le système. Dans cette thèse nous allons montrer deux méthodes permettant de produire des automates de parité. La première s'appuie sur l'amélioration et la combinaison de procédures nouvelles ou existantes. La seconde est un algorithme de Casares et al. apportant une garantie d'optimalité du résultat. Dans un deuxième temps, nous montrerons comment nous réduisons le système obtenu. Deux types de réductions seront abordées. La première permet d'obtenir un résultat optimal mais pas la seconde qui privilégie le temps de traitement. La troisième partie décrira des optimisations qui peuvent être utilisées pour certaines classes de spécifications
Synthesis aims to produce a correct system from specifications. One approach to solve this problem is to translate the specification into a parity game whose winning strategy encodes the system. In this thesis we will show two methods to produce parity automata. The first is based on improving and combining new or existing procedures. The second is an algorithm from Casares et al. providing a guarantee of optimal results. In a second step, we will show how we reduce the obtained system. Two types of reductions will be discussed. The first allows to obtain an optimal result but not the second which privileges the processing time. The third part will describe optimizations that can be used for certain classes of specifications

Les systèmes commutés sont des systèmes dynamiques comportant plusieurs modes de fonctionnement, chaque mode étant décrit par une équation différentielle (temps continu) ou une équation aux différences (temps discret). Le mode de fonctionnement actif est déterminé à tout moment par un signal de commutation. Les systèmes commutés sont très utiles en pratique pour décrire précisément l’exécution d’algorithmes de contrôle sur des infrastructures informatiques distribuées et ainsi pour prendre en compte les contraintes liées à l’utilisation de ressources informatiques et de communication partagées. De plus, les systèmes commutés présentent des propriétés inattendues (un comportement instable peut par exemple résulter d’une commutation entre des modes de fonctionnement stables) qui justifient le développement d’outils théoriques spécifiques pour leur étude. Les premiers travaux sur la stabilité des systèmes commutés se sont concentrés sur la stabilité des signaux de commutation arbitraires ou satisfaisant certaines conditions de temps de séjour (minimum ou moyen). Plus récemment, plusieurs travaux se sont penchés sur le problème de la preuve de la stabilité de sous-ensembles de signaux de commutation. En général, de tels signaux de commutation sont supposés être générés par un automate à états finis et la stabilité est caractérisée soit en terme de rayon spectral conjoint contraint, soit `a l’aide de fonctions de Lyapunov. Cependant, certains sous-ensembles de signaux de commutation ne peuvent pas être spécifiés à l’aide d’automates à états finis classiques. Les exemples sont les signaux de commutation appartenant à certaines langues oméga-régulières qui sont définies par des formules de logique temporelle linéaire (LTL). Ils sont souvent utilisés pour spécifier les protocoles de planification et de communication. Un exemple représentatif de langage oméga-régulier est l’ensemble des signaux de commutation de type ”shuffle” : un signal de commutation est dit de type ”shuffle” si et seulement si tous les modes sont activés une infiniment souvent. Dans une étude préliminaire, la stabilité des systèmes commutés sous signaux de commutation de ce type de contrainte a été caractérisée au moyen des fonctions de Lyapunov. Cette thèse vise à développer des outils théoriques et numériques pour analyser la stabilité des systèmes commutés sous signaux de commutation de type ”shuffle” et plus généralement sous contraintes données par un langage oméga-régulier. Nous définissons une notion de rayon spectral joint ”shuffled” qui nous permet de quantifier la vitesse de convergence du système commuté sous des signaux de commutation de type ”shuffle”. Nous développons des algorithmes numériques basés sur les inégalités matricielles linéaires (IML) et des techniques théoriques des automates pour calculer des approximations du rayon spectral joint ”shuffled”. Dans la deuxième partie de la thèse, nous étendons ces résultats à des classes plus générales de signaux de commutation tels que ceux spécifiés par les langages oméga-réguliers. Ces langages peuvent toujours être caractérisés par des automates de Büchi. Enfin, nous présenterons une conception d’observateur pour systèmes commutés basée sur les automates de Büchi et les séquences reconstructibles, c’est-à-dire des séquences permettant d’estimer l’état du système. Cette conception consiste en une application de nos résultats théoriques
Switched systems are dynamical systems with several operating modes, each mode being described by a differential (continuous time) or difference (discrete time) equation. At all times, the active operating mode is determined by a switching signal. Switched systems are very useful in practice for accurately describing the execution of control algorithms on distributed computing infrastructures and thus for taking into account the constraints linked to the use of shared computing and communication resources. Furthermore, switched systems have unexpected properties (unstable behavior can for example result from switching between stable operating modes) that justify the development of specific theoretical tools for their study. Early work on stability of switched systems has focused on stability for switching signals that are arbitrary or that satisfy some (minimum or average) dwell-time condition. More recently, several works have considered the problem of proving stability for subsets of switching signals. In general, such switching signals are assumed to be generated by some finite state automaton and stability is characterized either in term of constrained joint spectral radius or using Lyapunov functions. However, there are some subsets of switching signals that cannot be specified using classical finite state automata. Examples are switching signals belonging to some omega-regular languages e.g. defined by Linear Temporal Logic (LTL) formulas, which are often used to specify scheduling and communication protocols. A representative example of omega-regular language is the set of shuffled switching signals: a switching signal is shuffled if and only if all the modes are activated infinitely often. In a preliminary study, the stability of switched systems under shuffled switching signals was characterized by means of Lyapunov functions. This thesis aims at developing theoretical and numerical tools to analyze the stability of switched systems under shuffled switching signals and more generally under constraints given by an omega-regular language. We define a notion of shuffled joint spectral radius that allows us to quantify the speed of convergence of the switched system under shuffled switching signals. We develop numerical algorithms based on Linear Matrix Inequalities (LMIs) and automata theoretic techniques to compute approximations of the shuffled joint spectral radius. In the second part of the thesis, we extend these results to more general classes of switching signals such as those specified by omega-regular languages. These languages can always be characterized by Büchi automata. Finally, we will present an observer design for switched systems based on the Büchi automata and reconstructible sequences, i.e. sequences allowing to estimate the state of the system. This design consists of an application of our theoretical results

AbstractThis paper explores how using commutativity can improve the efficiency and efficacy of algorithmic termination checking for concurrent programs. If a program run is terminating, one can conclude that all other runs equivalent to it up-to-commutativity are also terminating. Since reasoning about termination involves reasoning about infinite behaviours of the program, the equivalence class for a program run may include infinite words with lengths strictly larger than $$\omega $$ ω that capture the intuitive notion that some actions may soundly be postponed indefinitely. We propose a sound proof rule which exploits these as well as classic bounded commutativity in reasoning about termination, and devise a way of algorithmically implementing this sound proof rule. We present experimental results that demonstrate the effectiveness of this method in improving automated termination checking for concurrent programs.

Abstract This work presents an improved open-source autonomous CFD meta-modeling environment (OpenACME) for small-scale combustor design optimization. OpenACME couples several object-oriented programming open-source codes for CFD-assisted engineering design meta-modeling. OpenACME is fully automated and can be used in PC workstations or HPC clusters. OpenACME uses a global metaheuristic optimization algorithm based on multiple-objective evolutionary algorithm (i.e., NSGA-II). An initial design population is first computed with Latin Hypercube Sampling and subsequent iterations generate offspring based on tournament mating, uniform crossover, and polynomial mutation. OpenACME is capable of computing multiple parallel CFD design points concurrently, speeding up the meta-simulations. The CFD are based on steady-state, incompressible, three-dimensional simulations with multi-phase k-ω SST RANS and “frozen” flamelet progress variable (FFPV) combustion model. There are fifteen design variables. There are three meta-simulations. The meta-simulations report Pareto Frontier from which optimum designs can be selected based on thermodynamic cycle requirements. Conjugate heat transfer provides the most realistic liner temperature and combustor performance. Acritical is still recommended as a cost function when liner durability is a concern. OpenACME demonstrated to be a viable tool for combustor design optimization.

The interaction of secondary flow with the main passage flow results in entropy generation; this accounts for considerable losses in turbomachines. Low aspect ratio blades in an axial turbine lead to a high degree of secondary flow losses. A particular interest is the reduction in secondary flow strength at the turbine casing, which adversely affects the turbine performance. This paper presents a selective review of effective techniques for improving the performance of axial turbines by turbine end wall modifications. This encompasses the use of axisymmetric and non-axisymmetric end wall contouring and the use of fences. Specific attention is given to non-axisymmetric end walls and to their effect on secondary flow losses. A baseline three-dimensional steady RANS k-ω SST model, with axisymmetric walls, is validated against experimental measurements from the Institute of Jet Propulsion and Turbomachinery at the Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen, Germany, with comparative solutions generated by ANSYS Fluent and OpenFOAM. The predicted performance of the stator passage with an axisymmetric casing is compared with that from using a contoured casing with a groove designed using the Beta distribution function for guiding the groove shape. The prediction of a reduced total pressure loss coefficient with the application of the contoured casing supports the groove design approach based on the natural path of the secondary flow features. This work also provided an automated workflow process, linking surface definition in MATLAB, meshing in ICEM CFD, and flow solving and post-processing OpenFOAM. This has generated a casing contouring design tool with a good portability to industry, to design and optimize new turbine blade passages.