Properties of Co on Cu(111) revealed by AES and DEPES

Auger electron (AES) and directional elastic peak electron (DEPES) spectroscopies were used to investigate the Co/Cu(111) interface. The change in the Auger Cu (M_2,3VV transition at 66 eV) peak intensity (h_Cu) recorded at room temperature shows that the Co growth mechanism is not a layer by layer type. This proves that Co does not wet the Cu substrate. The recorded DEPES profiles reveal the coexistence of fcc and hcp Co structures already at an early stage of growth (0.8 ML). The Co coverage increase leads to the reduction of intensities associated with the fcc structure and significant increase of the signal from the hcp structure. The comparison between experimental and theoretical data at large coverages (43 ML) shows a major contribution of the hcp structure within the Co layers in the recorded DEPES profiles.     

Unified approach to measurand reconstruction

The basic notions of measurement science are overviewed. A general scheme of measurement is proposed that emphasizes the key role of measurand reconstruction. The problems of measurand reconstruction are classified. Two classes of them, being of particular importance in practical applications, are identified and discussed in more detail. These are the nonlinear reconstruction of a scalar static measurand in the presence of a scalar influence quantity, and the linear reconstruction of a scalar dynamic measurand. Considerations of a tutorial and theoretical nature are illustrated with practical examples     

Regularized differentiation of measurement data using a prioriinformation on signal and noise spectra

An algorithm previously proposed by the authors (see Proc. of Conf. EMISCON, Prague, 153-5, June 13-15, 1989) for real-time differentiation of discrete measurement data is further developed and studied. The effectiveness of this algorithm depends on a regularization parameter whose value should be fitted to the level of disturbances to which the data are subject. A simple method for choosing this value is proposed which requires only scanty a priori information on the data, namely an estimate of the signal bandwidth and an estimate of the signal-to-noise ratio. The effectiveness of this method is demonstrated using synthetic data and computer experimentation methodology. It is shown that the attainable accuracy of differentiation is very close to the optimum which may be reached by empirical optimization of the parameter of regularization     

Digital correction of A/D conversion error due to multiplexingdelay

A measurement channel which consists of a multiplexer, sample-and-hold circuit, and analog-to-digital (A/D) converter is studied. It is designed for the synchronous sampling and measurement of two or more voltage signals V₁(t), V ₂(t), . . ., but the finite time of A/D conversion (ΔT) makes it impossible to acquire consecutive samples closer in time than ΔT. This can become a source of measurement error if further processing of the measurement data is based on the assumption of ideal synchronism. It has been found that interpolation filters, developed from the Lagrange polynomial interpolation, are useful tools for solving the problem of correction. An illustrative example of their use is presented     

Etude de l'action des acides de lewis sur les polymères. Application au greffage de macromolécules sur les surfaces solides

The interaction between a solid surface (metal oxides, carbon blacks…) and macromolecules carrying a carbenium ion formed by a Lewis acid attack, results in a significant insolubilization of the polymer on the surface. Physical modifications of hydrocarbon polymers under the action of Lewis acids have been followed. Saturated (polyethylene, polypropylene, polyisobutylene), unsaturated (polybutadiene, polyisoprene, styrene-butadiene and isoprene-isobutylene copolymers) and styrene polymers have been investigated. Lewis acids generally extract a hydrid ion or add a proton to the double bond of a polymer. In both cases, a polymeric cation is formed: its evolution depends essentially on its stability and on the vicinity of chemical groups on the backbone of the polymer. The carbenium ion reacts with the surface hydroxyl groups. The amount of polymer irreversibly fixed on the solid surface exceeds the one required for the formation of the monolayer. It depends both on the concentration of polymeric cations and on the accessibility of the surface groups to the Lewis acid.     

A new impedance-transformation property and its applications to switching-diode Q-factor measurements

A new property of impedance transformation is presented that can be applied to semiconductor switching-diode Q factor measurements. The only parameter that must be known for the diode holder and the diode package is the efficiency of the energy transmission from the source of the signal to the semiconductor junction.     

An efficient algorithm for processing data from a multi-point sensor of vibrations

A new technique of vibration sensing, based on a polarimetric fibre-optic strain sensor, is presented; it is designed for localisation of multiple sources of disturbances in a broad frequency spectrum without using fibre gratings. A mathematical model of the sensor is used for development of a variational method for estimation of amplitudes of component vibrations on the basis of noisy samples of the signal at the output of the sensor. This method is implemented in a new algorithm of estimation, being 100–1000 more efficient (in terms of computing time) than an algorithm published previously.     

An application-oriented mathematical meta-model of measurement

The need for broader use of concepts of modelling in the development of a conceptual basis for measurement science is ascertained. A brief review of basic concepts of mathematical modelling is provided, and a class of models, most frequently used in measurement science, is characterised. A meta-model of measurement, unifying many existing methodologies of mathematical modelling in measurement science, is proposed. Its applicability is illustrated with a set of diversified examples.     

Kalman-filter-based algorithms of spectrophotometric datacorrection III. Use of splines for approximation of spectra

An alternative method to that presented in the first paper of the series for improving the resolution of spectrophotometric measurements via processing of spectrometric data is proposed. It is based on the approximation of the solution with a spline function the parameters of which are determined by means of a recursive Kalman-filter-based algorithm. It is assumed in the paper that the model of the spectrophotometric data has the form of an integral, convolution-type equation of the first kind. It is shown, using synthetic and real-world spectrophotometric data, that the proposed method allows for significant reduction of computational requirements as well as an improvement in the quality of correction