Application of principal component analysis to the prediction of lucerne forage protein content and in vitro dry matter digestibility by NIR spectroscopy

Application of principal component regression (PCR) was proposed for the development of a prediction equation of forage composition by near infra-red spectroscopy. PCR involves two steps: (a) the creation of new synthetic variables by principal component analysis (PCA) of spectral data, and (b) multiple linear regression with these new variables. Results obtained by this procedure have been compared with those generated by the conventional application of multiple linear regression (MLR) on spectral data. The comparison used the determination of protein content and in vitro dry matter digestibility (IVDMD) in 345 samples of lucerne forages. For protein determination, results of both procedures were quite similar (correlation coefficients: 0.978 and 0.980; standard errors of calibration: 0.86 and 0.84% DM; standard errors of prediction: 0.81 and 0.80% DM respectively for MLR and PCR prediction equations). The same was observed for IVDMD determination (correlation coefficients: 0.942 and 0.951; standard errors of calibration: 1.89 and 1.71% DM; standard errors of prediction: 2.22 and 2.22% DM, respectively). A large number of PCA variables were necessary for an accurate prediction of both constituents. The influence of the number of regression terms introduced in the PCR equation has been studied. The criterion for stopping the introduction of new terms in PCR did not seem as critical as in MLR.     

Cocontraction changes in muscular fatigue at different levels of isometric contraction

Ten normal subjects participated in a study designed to contrast results obtained in pre- and post-fatigue states. The measures contrasted were the IEMG ratios of agonist/antagonist pairs of muscles. The experimental task was an 8 s ramp isometric elbow flexion ranging from 0 to 100% of a maximal voluntary contraction (MVC). IEMG ratios were obtained at levels of 20, 40, 60 and 80% MVC. Records from the following muscles were obtained with surface electrodes: biceps brachii (BB), brachioradialis (BR), triceps brachii (TB) and anconeus (SU). The torque at the elbow joint was measured by a Cybex II dynamometer. Fatigue was induced using a 60% MVC of elbow flexion maintained during 5 minutes. The data were collected on-line at a sampling rate of 1 kHz. The results indicated that the IEMG ratios (BB/TB and BR/SU) presented a tendency, across subjects, toward a decrease at the levels of 40%, 60% and 80% MVC at the post- relative to the pre-fatigue state. The BB/BR ratios remained stable. These changes in the post-fatigue ratios disclose a tendency toward a saturation of the agonist occurring concomitantly with an increased level of contraction of the antagonists.     

Anisotropie de la decomposition d'un solide. II-mise en evidence d'un gradient thermique dans la phase solide a l'aide d'un thermographe infra-rouge

Monocrystalline platelets of pentahydrate Copper sulfate are submitted to temperature and pressure conditions such that they cause this salt to be converted into a trihydrated salt. Thermal equilibrium of these platelets is ensured before the reaction starts. Temperature is recorded as moving away from the superficial domain undergoing conversion, by means of an I.R. scanning camera fitted with a cooled detecting device. The occurence of a thermal gradient from the reactive solid-solid interface can, thus, be shown. It seems, therefore necessary to take into account the physical properties of the crystal, which are involved in the occurence of thermal gradients in the solid, to explain the anisotropy of this interface displacement during a conversion where a gas is removed.     

Discrete-time estimation of a Markov chain with marked pointprocess observations. Application to Markovian jump filtering

In this paper, various discrete-time estimation problems are studied for a finite and homogeneous Markov chain observed by a marked point process. These problems, which could have significant applications in target tracking, manufacturing or communication theory, have never been studied in the literature. The quantities to be estimated are the state, the number of jumps and the occupation times. The identification of the chain transition matrix is also addressed via an expectation maximization procedure. Solutions, in the sense of the conditional distribution, are obtained by a change of probability measure and are shown to have convenient recursive forms. The efficiency of this new approach for sensor modeling is illustrated by the study of a linear Markovian jump filtering problem where, in addition to a classical state observation, a mode Markov point process observation is assumed. A numerical example is given     

Effects of Botrytis cinerea infection on Champagne wine foaming properties

Qualitative effects of Botrytis cinerea infection were studied by comparing the foaming properties of Champagnes obtained from healthy grapes with those from grapes infected by B cinerea. This is of particular interest when it is considered that the foaming properties of Champagne wines are important in terms of product attractiveness for the consumer. Experiments using artificial viewing equipment clearly showed the dramatic effects on Champagne foam characteristics when grape berries were highly infected. The speed at which liquid separated from the foam (expressed as liquid height L_S) in the glass depended largely on the level of infection for Chardonnary and Pinot noir wines (+268% for Chardonnary wines at 40% infection and +627% for Pinot noir wines at 20% infection). B cinerea infection reduced the time (L_T) at which liquid first appeared in the glass; for Pinot noir wines an infection level of 20% caused very rapid drainage. The time of pouring (P_T, ie the time to fill the glass under controlled conditions) also diminished considerably at an infection level of 20% for both Pinot noir and Pinot meunier wines (?74 and ?58% respectively). Mouldiness considerably altered the foam height observed 80 s (H₈₀) after the start of pouring (?83% for Pinot noir and ?89% for Pinot meunier at 20% infection). Champagne foamability was also quantified using a sparging technique to standardise effervescence. Foamability suffered considerably (?60 to ?65%) when the B cinerea infection level was 20% as compared to control Champagnes. All wines studied had low and very similar protein contents. Differences in the concentrations of these compounds, which are generally implicated in the formation of foam in sparkling wines, could not explain the differences in Champagne foaming properties observed here. © 2001 Society of Chemical Industry     

A Bayesian analysis of experiments with small numbers of events

Within the framework of Bayesian statistics we derive a distribution for the posterior degree of belief both for the difference and ratio of small numbers of events, when the background mean in each case is known with finite precision.     

Structural change of water with solutes and temperature up to 100 degrees C in aqueous solutions as revealed by attenuated total reflectance infrared spectroscopy

The attenuated total reflectance infrared (ATR-IR) spectra of several aqueous solutions have been measured by using a newly developed heatable rod-type ATR cell. The OH stretching bands showed systematic change with increasing solute concentrations and these changes can be explained by four different OH components based on curve-fitting results. NaCl solutions show longer H-bond distance character, while carbonate solutions present shorter ones. The Na2CO3 1 M solution conserves this shorter H-bond nature up to 100 degrees C. On the other hand, the loose nature of NaCl solutions becomes less pronounced at higher temperatures because of the dissociation of pure water clusters. These in situ observations of water structures are generally in agreement with the expected nature of fluids within the earth.     

Engineering studies for the installation of an axi-symmetric metallic divertor in Tore Supra

Tore Supra (TS) has been designed to operate using technologies that allow long plasma operation (a few minutes), by means of superconducting magnets and actively-cooled high heat flux plasma facing components (PFCs). Actively cooled tungsten PFC will be used in the baffle area of the first ITER divertor. In order to validate such a technology fully (industrial manufacturing, operation with long plasma duration), the implementation of a tungsten axi-symmetric divertor in the tokamak Tore Supra has been studied [1]. With this second major upgrade, Tore Supra should be able to address the problematic of long plasma discharges with a metallic divertor.The proposed divertor is made up of two stainless steel casings containing a copper coil winding located at the top and bottom area of the vacuum vessel. These casings are firmly maintained by connection beams and protected by PFC. This paper describes the mechanical design of this major component and its integration in TS, the associated electromagnetic and thermomechanical analysis, the manufacturing issues and finally the integration of ITER representative PFCs.     

Efficiency of Spectral-Based ADC Test Flows to Detect Static Errors

Testing of Analog-to-Digital Converters is classically composed of two successive and independent phases: the histogram-based test technique evaluating static specifications and the spectral analysis technique evaluating the dynamic performances. Consequently, the fundamental objective here is to investigate the feasibility of an alternative test flow involving exclusively spectral analysis to replace these two time consuming and expensive phases. The viability of this solution depends on the ability of spectral analysis to detect static specifications. In this context, this paper presents a new methodology based on a statistical approach to quantitatively evaluate the efficiency of detecting static errors from dynamic parameter measurements. This methodology has been implemented in an in-house automatic tool allowing one to process any ADC specifications. It is then possible to choose a priori the best test flow for a given application.