DIVA: Recognition of typical situations for turbine generator diagnosis

DIVA is an expert system for turbine generator diagnosis. Its aim is to help a plant operator interpret vibration evolution to diagnose developing faults. Interpretation of vibration evolution is primarily a recognition process which is achieved by a particular model of heuristic classification. DIVA tries to recognize the observed situation among a hierarchy of typical situations.The purpose of this paper is to present the model we used for heuristic classification, based on prototypes. Prototypes represent typical problem situations and may also be seen as experts with special knowledge of what to do in such situations. We argue that this model presents significant advantages to deal with complex problems such as vibration surveillance.     

Two C60O Structures and Their Relative Stabilities: AM1 Computations

C₆₀O is studied by means of the AM1 quantum-chemical method. Full geometry optimization of its C_s and C_2v structures, and harmonic vibrational analysis, are employed in the evaluation of the temperature dependence of their relative stabilities. The C_2v structure remains a minor component of the equilibrium gas-phase mixture even at high temperatures.     

Species-specific composition of free amino acids on the leaf surface of fourSenecio species

The specificity of the chemical composition of the leaf surface of fourSenecio species was studied in order to understand the host selection ofTyria jacobaeae, a monophagous moth that hasSenecio jacobaea as its principal host plant. Pyrrolizidine alkaloids characteristic forSenecio species were not detected in water and sulfuric acid extracts of the leaf surface ofSenecio jacobaea. Water extracts of the leaf surfaces ofS. jacobaea, S. vulgaris, S. viscosus, andS. sylvaticus contained low concentrations of free amino acids. The proportions of these amino acids were very different from those inside the leaf tissues. In a discriminant analysis, the four species could be completely separated on the basis of the relative proportions of amino acids on the leaf surface.     

Back and forth between continuous and discrete for the working computer scientist

This paper gives a perfect, ideal, discretization of continuous notions. This is a very convenient frame to treat continuous problems or theories with the help of a computer. This is illustrated by the conversion of algorithms using real numbers into algorithms using integers only and the founding of discrete geometry.     

The formation of triarylsulfonium salts through a photochemical route

Summary An original method of synthesizing triarylsulfonium salts through UV light excitation of diphenylsulfides in presence of diphenyliodonium salts is described.Visiting Scientist from the Institute of Photographic Chemistry, Academia Sinica, Beijing, China     

Periodes et repetitions des mots du monoide libre

We study the relationship between the global periodicity of a word and its (local) repetitions, that is to say its successive equal factors.Our main result generalizes the theorem of Cesari Vincent according to which the period of a word is the maximum of the minimal repetitions. Our generalization is twofold, it does not take account of any sides to define repetitions (the above result does) and calculates the maximum only on a special set of points. It allows a sharpened version of the solution to a problem settled by Schützenberger in which the theorem of Cesari Vincent originates.     

Autoirradiation d'un alliage cubique centre uranium-plutonium-molybdene

Measurements have been made of the length changes due to self-irradiation damage at 4.2 K for over 1300 h in a U-Pu-Mo bcc alloy (containing 20 at% plutonium and 15 at% molybdenum) stabilized by quenching. These are the first measurements of this type carried out on a bcc alloy. The initial rate of increase of δl/l was $\text{2,3 × 10}{}^{\mathrm{?7}}\text{h}{}^{\mathrm{?1}}$ If it is assumed that each α desintegration forms 1800 Frenkel pairs, it is found that Frenkel pairs have a formation volume equal to 0.5 atomic volume.     

Polymorphisme de l'hydrure de magnesium sous haute pression

The structural relationships in magnesium hydride have been studied under P-T conditions up to 80 kbar and 900°C. α-MgH₂ of rutile structure in normal conditions transforms into two new phases under high pressures : β-MgH₂ and γ-MgH₂ respectively with a hexagonal (pseudocubic) and an orthorhombic unit-cell structure·β-MgH₂ maybe related to a fluorite type form (with an eight-coordination for Mg) transforming when releasing pressure into γ-MgH₂ of α-PbO₂ type (with a six-coordination for Mg). The density of α-MgH₂ and γ-MgH₂ are very similar but the density of the β-MgH₂ fluorite form is some 25 % greater than that of the rutile type. Thus MgH₂ seems to exhibit under high pressure conditions the typical behavior of number of rutile type compounds MX₂ such as fluorides or oxides.