Testing linear models on spectral daylight measurements

We have analyzed the results of the reconstruction quality of 252 daylight spectral curves measured at Granada, Spain, using four bases obtained from measurements in different areas of the world. For these reconstructions we used two different methods (orthogonality of characteristic vectors and chromaticity coordinates) to study the influence of the wavelength range and spectral resolution. The reconstruction method from chromaticity coordinates presents difficulties for the spectral recovery of daylight spectral power distributions regardless of the basis used. The orthogonality method makes clear that the best bases were those proposed by the CIE, but more than two characteristic CIE vectors were needed for good reconstruction.     

On certain potential improvements in the metrological traceability of linear measurements in the nanometric range

A new approach to linear measurements in the nanometric range based on the measurement of the transit time of an electromagnetic wave between two points that bound a linear region is proposed. Frequency methods that make it possible to increase the resolution of linear measurements and improve their traceability in this range are used.     

On the conversion of functional models: bridging differences between functional taxonomies in the modeling of user actions

In this paper, I discuss a methodology for the conversion of functional models between functional taxonomies developed by Kitamura et al. (2007) and Ookubo et al. (2007). They apply their methodology to the conversion of functional models described in terms of the Functional Basis taxonomy into functional models described in terms of the Functional Concept Ontology taxonomy. I argue that this model conversion harbors two problems. One, a step in this model conversion that is aimed to handle differences in the modeling of user features consists of the removal of Functional Basis functions. It is shown that this removal can lead to considerable information loss. Two, some Functional Basis functions that I argue correspond to user functions, get re-interpreted as device functions in the model conversion. I present an alternative strategy that prevents information loss and information change in model conversions between the Functional Basis and Functional Concept Ontology taxonomies.     

Analog-digital systems for adaptive measurements and parameterestimation of noisy processes

The theoretical framework and principles of designing a new class of highly effective analog-digital computer-aided measurement systems are presented. The proposed approach enables the designers to determine uniquely the optimal structure, parameters and characteristics of measurement systems working in the presence of noises and disturbances as well as to carry out the comprehensive analysis of their work. The approach is based on the new idea of the nonlinear adaptively controlled (smart) sensor. The algorithms for optimal processing of the measured data and estimating unknown parameters of analyzed processes or objects, coupled with the optimal adaptive control of the sensor parameters, are derived. The superiority of measurement systems with adaptively controlled sensors over the conventional ones employing nonadaptive sensors is shown. The main theoretical results and conclusions are verified and confirmed via simulations taking as an example the string-frame accelerometer     

Investigating the precision of linear dimension measurements

Conclusions It is necessary to oblige the Committee of Standards'laboratories and institutes to supervise systematically the level of errors in production measurements, to generalize the results thus obtained, and to provide industry with information on the accumulated data. It is necessary to improve the qualifications of the personnel engaged in measurements and, in raising the wage scales of workers, to consider without fail their metrological qualifications.Translated from Izmeritel'naya Tekhnika, No. 5, pp. 33–34, May, 1968.     

On the effect of linear algebra implementations in real-time multibody system dynamics

This paper compares the efficiency of multibody system (MBS) dynamic simulation codes that rely on different implementations of linear algebra operations. The dynamics of an N-loop four-bar mechanism has been solved with an index-3 augmented Lagrangian formulation combined with the trapezoidal rule as numerical integrator. Different implementations for this method, both dense and sparse, have been developed, using a number of linear algebra software libraries (including sparse linear equation solvers) and optimized sparse matrix computation strategies. Numerical experiments have been performed in order to measure their performance, as a function of problem size and matrix filling. Results show that optimal implementations can increase the simulation efficiency in a factor of 2–3, compared with our starting classical implementations, and in some topics they disagree with widespread beliefs in MBS dynamics. Finally, advices are provided to select the implementation which delivers the best performance for a certain MBS dynamic simulation.     

On real-time optimal FIR estimation of linear TIE models of local clocks

In this paper, we present an optimal finite-impulse response (FIR) filter for the linear time-interval error (TIE) model of a local clock and compare its estimates to those obtained by the unbiased FIR filter via the global positioning system (GPS)-based sawtooth measurements. We show theoretically and verify experimentally that there is no reasonable necessity in using optimal filters for GPS-based estimation of the TIE of precision crystal, rubidium, and cesium clocks. For these clocks, the optimal FIR filter requiring four coefficients degenerates to a simple unbiased FIR filter requiring only one coefficient.     

Peculiarities of using laser diodes in linear measurements

The position of the emitting region of a laser diode depends on the working current. This phenomenon, as well as the polarization of radiation, may influence the accuracy of linear measurements using such lasers.     

Increasing the accuracy of gauge-block measurements of linear dimensions

The first stage in increasing the accuracy of measurements of the linear dimensions of precision parts the exact reproduction of a certified gauge block, is investigated. Recommendations are made on the use of a new method to evaluate the increase in the accuracy of evaluation of unmonitored lapping-in and contact deformations during measurements. Translated from Izmeritel'naya Tekhnika, No. 1, pp. 40–42, January, 1997.     

On the transmission of a fractal pulse in a noisy fiber-optic channel

A numerical experiment on the transmission of a fractal pulse through a single-mode optical fiber (with allowance for chromatic dispersion) has been carried out. The desired signal was transferred along with a masking noise signal. It is shown that efficient separation of fractal signal from noise at the output of fiberoptic communication line calls for knowledge of not only the fractal signal code, but also the dispersion coefficient of the optical fiber.     

Phase reconstruction from intensity measurements in linear systems

The phase of a signal at a plane is reconstructed from the intensity profiles at two close parallel screens connected by a small abcd canonical transform; this applies to propagation along harmonic and repulsive fibers and in free media. We analyze the relationship between the local spatial frequency (the signal phase derivative) and the derivative of the squared modulus of the signal under a one-parameter canonical transform with respect to the parameter. We thus generalize to all linear systems the results that have been obtained separately for Fresnel and fractional Fourier transforms.