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USURA IN PROTESI D'ANCA METAL-ON-METAL:CONFRONTO TRA DUE SOLUZIONI
No full textIl problema esaminato riguarda la determinazione e il confronto per via numerica del tasso di usura in due soluzioni per l’artroplastica totale dell’anca che differiscono per le dimensioni della testa articolare. L’usura degli impianti è stata stimata seguendo l’ipotesi di Reye dopo aver calcolato le distribuzioni delle pressioni di contatto mediante modelli FEM tridimensionali; l’analisi numerica è stata affiancata dalla discussione di un modello analitico semplificato basato sulla teoria di Hertz. I risultati hanno evidenziato come in condizioni di attrito secco l’impianto con testa di grande diametro (DUROMTM) rilasci una quantità doppia di materiale d’usura rispetto all’impianto con testa di piccolo diametro (METASULTM). In conclusione, mentre gli impianti DUROMTM riducono i rischi di lussazione permettendo una buona ampiezza di movimento, le protesi METASULTM sono da preferirsi nei casi in cui il tasso d’usura sia un fattore di scelta critico
Design parameters influence on office chairs comfort
No full textBack pain is reported as one of the main causes
of absence from office work. Office furnishing, in particular
office chairs, can help overcoming this problem, improving
health and comfort for workers with a correct ergonomic
approach. An experimental study was conducted on six
different office chairs that were examined and then tested by
twelve adult subjects. The effect of chair ergonomics on the
perceived level of comfort was investigated by means of
objective data obtained by a BPMS (Body Pressure
Measurement System) and subjective evaluations were drawn
from a questionnaire. Particular attention was paid to the
calibration and equilibration of the measurement system. The
results point out interesting and unexpected correlations
between subjective and objective evaluations of the chairs
A FEM comparison of wear in two metal-on-metal total hip prostheses
No full textThe contact mechanics of two metal-on-metal (MOM) total hip prostheses was studied
by means of the finite element method (FEM). The purpose of the work was to compare two
total hip replacements (DuromTM and MetasulTM) with regard to the amount of wear debris
released. Wear on the bearing surfaces was evaluated following Reye hypotheses from the pressure
distribution, computed by means of three-dimensional FEM models; an approximate analytical
model based on Hertz contact theory has also been developed and discussed. The results
show that in the dry friction condition the DuromTM joint releases almost twice as much wear
volume as produced by the MetasulTM joint. Therefore, while DuromTM implants can improve
hip stability by increasing the prosthetic impingement-free range of motion (PIF-ROM),
MetasulTM prostheses can be a valuable solution whenever wear represents a critical choice factor
Office chair design implications on subjective comfort
No full textOffice chair design implications on subjective comfor
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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