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Experimental characterization of the dwell periods in a 8-bars linkage
No full textAn 8-bars linkage, formed by two four-bars and one slider-crank mechanisms connected in series, designed to obtain a rectilinear motion of the output link with two dwell periods, has been tested to validate the desired output motion. The input crank is powered, using a belt transmission, by an asynchronous motor fed by a voltage source inverter. The displacement in the dwells, measured with a Laser Doppler Vibrometer, has been recorded for different values of the input crank speed. By comparison to theoretical results it is shown that, for high input crank speed, link elasticity and joint clearances strongly influence the displacement amplitude in the dwells
Physiological characteristics of elite snowboarders
No full textAim. To profile the physiological qualities of elite snowboarders and quantified the relationships with snowboarding performance.
Methods. Ten alpine (ALP, mean±SD age: 25.6±4.4 yrs; body mass 78.1±12.1; height 178.4±9.8 cm; sum of 7 skinfolds 74.8±19.4 mm; body fat 13.8±3.7%) and ten snowboardcross (SBX, mean±SD age: 23.5±4.3 yrs; body mass 77.2±9.2; height 181.0±4.9 cm; sum of 7 skinfolds 70.1±21.1 mm; body fat 11.9±3.5%) elite male athletes undertook aerobic power (cycle ergometer maximum oxygen uptake), muscular isometric strength (maximal isometric voluntary contraction, MVC), and muscle-power (vertical jumps), as well as ALP [parallel giant slalom (PGS) and parallel slalom (PSL)] and SBX simulated competitions. Associations between measurements were assessed by correlation analysis.
Results. Absolute (ALP 383.1±38.0 W, P<0.01; SBX 339.7±41.3 W, P<0.05) and relative (ALP, 4.6±0.5 W·kg-1, P<0.01; SBX 4.5±0.3 W·kg-1, P<0.05) power output, power at the first (ALP 196.0±53.7 W, P<0.01; SBX 192.8±24.3, P<0.01) and second (ALP 285.4±60.6 W, P<0.01; SBX 280.4±20.3 W, P<0.01) ventilatory threshold, MVC (ALP 731.9±181.9 N·m-1, P<0.001; SBX 680.1±76.8 N·m-1, P<0.001) and leg stiffness (ALP 31.4±4.8 N·m-1·kg-1, P<0.01; SBX 25.4±3.0 N·m-1·kg-1, P<0.01) were highly correlated with PGS (r = -.88 to -.97), PSL (r = -.84 to -.94), and SBX (r = -.89 to -.93) performance times.
Conclusion. To meet the demands of snowboarding competition, elite snowboarders require highly developed muscular strength and power. This study provides criteria for the selection of appropriate physiological variables for the longitudinal monitoring of relevant parameters in snowboarding
Considerazioni sulle caratteristiche termiche di pannelli leggeri non omogenei. Parte II
No full textMethyl tert-butyl ether (MTBE) bioremediation studies
No full textThe massive production of methyl tert-butyl ether (MTBE), a primary constituent of reformulated gasoline, combined with its mobility, persistence and toxicity, makes it an important pollutant. It was considered recalcitrant until a few years ago, but recently MTBE biodegradation in aerobic conditions has been demonstrated with both mixed and pure cultures. Mixed cultures are generally the more effective for MTBE removal, and the addition of a suitable co-substrate to the cultures can enhance the removal. The slow degradation of MTBE has been observed under anaerobic conditions, but only in the presence of humic substances. In recent work, degradation possibilities have been demonstrated when MTBE is the sole carbon and energy source, although the biodegradation was slow. In several cases the addition of a co-substrate such as n-alkane, particularly pentane, improved MTBE degradation. The biological treatment of MTBE contaminated soil, water and groundwater could provide a simpler, less expensive alternative to chemical and physical processes for MTBE removal, and the possibility of such an approach has led to investigations into the microbial consortia able to degrade this compound, and the best environmental conditions for its removal. Over the last few years the state of the art of MTBE bioremediation studies has expanded rapidly and numerous articles have been published. Field experiments have revealed the possibility of removing MTBE completely, though the process is slow. Particularly important are treatments involving biostimulation, diffusing oxygen in contaminated groundwaters, and bioaugmentation, that has been demonstrated to improve MTBE removal. The aim of this paper has been to provide a summary of the literature available on MTBE biodegradation in batch systems, reactors and in field
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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