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Biomedical subjects

F Gazzani

Publications and source records attributed to F Gazzani.

6 recordsLinked to original sources
PubMed1994

Comparative assessment of some algorithms for differentiating noisy biomechanical data.

In this paper, a comparison is carried out between various algorithms for smoothing and differentiating noisy (non-exact) discrete time series, a problem frequently encountered in experimental movement studies. The algorithms compared are: the 'implicit procedure' of Anderssen and Bloomfield (Numer Math, 22 (1974) 157-182) with a refinement by Kosarev and Pantos (J Phys E Sci Instrum, 16 (1983) 537-543); the 'explicit procedure', a digital filter method in which the filter coefficients are computed starting from the measurements; the regularized Fourier series method (these two algorithms were also presented by Anderssen and Bloomfield); and, finally, natural B-splines regularized by the generalized cross-validation criterion. The comparison was performed mainly by analytical, noise-corrupted test sequences, whose derivatives were known a priori. The testing procedure proved capable of showing the different characteristics of the various algorithms, and providing criteria to choose that best suited to a given practical situation. In most cases, the regularized Fourier series method and the implicit procedure proved to have the best tradeoff between accuracy and speed.

Algorithms↗
PubMed1992

Performance of a 7-parameter DLT method for the calibration of stereophotogrammetric systems using 1-D transducers.

A method is presented for calibrating stereophotogrammetric systems which are based on 1-D cameras, i.e., able to record only one of the two coordinates relative to the projection of the target point onto the image plane of a camera. This procedure is based on the Direct Linear Transformation, DLT, introduced by Marzan and Karara. The present version (7DLT) is different from the standard 11-parameter DLT (11DLT); it avoids certain non-orthogonality problems arising in usual DLT implementations, whose correction can be obtained by modifying the basic algorithm, at the expense of its simplicity (MDLT). The accuracy assessment of the 7DLT method was carried out both by a computer simulation of a two-camera stereophotogrammetric system, and on real data from three 1-D optoelectronic cameras. The computer simulation permitted us to compare the performance of 7DLT with 11DLT and MDLT. The reconstruction accuracies of the three algorithms were quite similar. When using real 1-D data, a reconstruction accuracy of 0.66 mm RMS error was obtained (mean value for X, Y, Z coordinates) for 18 target points used as calibration control points. The extrapolation accuracy was 1.85 mm RMS for 180 target points lying outside the calibration structure.

Animals↗
PubMed1985

Lumbar spine loading during half-squat exercises.

Evaluation of the compressive load acting on the lumbar spine (L3-L4) during half-squat exercises executed with a barbell resting on the subject's shoulders was undertaken. The kinematics of the upper body segments of two male and two female subjects as well as the barbell were described using data obtained by means of an optoelectronic system (CoSTEL). L3-L4 compressive load was calculated using a model of the anatomy of the trunk musculoskeletal system. Filtered surface electromyographic trunk flexor recordings from the obliquus externus and rectus abdominis and trunk extensor erectores spinae muscles as well as measurement of the ground reaction forces were also carried out for predicted result validation. During half-squat exercises with barbell loads in the range 0.8 to 1.6 times body weight the compressive loads on the L3-L4 segment vary between 6 and 10 times body weight. Erectores spinae contraction force was predicted to be between 30 and 50% of the relevant maximal isometric force. The magnitude of trunk flexion was found to be the variable which influenced most spinal compression load.

Adult↗
PubMed1983

Comparative evaluation of techniques for the harmonic analysis of human motion data.

Four mathematical techniques for the estimation of the Fourier coefficients of pseudoperiodic non-exact discrete functions were submitted to comparative evaluation. These techniques were devised within the following basic procedures: (1) numerical harmonic analysis applied either directly or after redistribution of the data points through some interpolation procedure, so that they be evenly spaced in time and exactly fit on cycle period; (2) fitting of the empirical data with an analytical model followed by the calculation of the Fourier integrals of this model. The evaluation was carried out with special reference to the use of these techniques for processing human motion photogrammetric data. The following criteria were used: (1) accuracy of the Fourier coefficient estimates, (2) capability of yielding information about this accuracy, (3) a priori information needed regarding the statistical properties of the experimental error, (4) factors concerning implementation in digital computers. Practical information was obtained for the non-specialist user with regard to the choice of one technique among the several possible in particular circumstances.

Fourier Analysis↗
PubMed1982

Angular displacements in the upper body of AK amputees during level walking.

The angular displacements of the longitudinal axis of the trunk, and of the latero-lateral axes of pelvis and shoulder girdle were measured in five normal subjects and four AK amputees during level walking at different speeds. Amputees used single axis prostheses with the SACH foot. Spatial measurements were carried out in three dimensions by means of a photogrammetric technique. The time functions of the target angles underwent harmonic analysis. Based on the Fourier coefficients, comparison was made between normal subjects' and amputees' angular displacements. Relevant findings permitted the identification of compensatory mechanisms adopted by amputees at trunk level as well as the assessment of the relationship between these latter mechanisms and those put into action at lower limb level.

Amputation, Surgical↗