134,348 research outputs found
Noncommutative determinants, Cauchy-Binet formulae and Capelli-type identities. I. Generalizations of the Capelli and Turnbull identities
No full textWe prove, by simple manipulation of commutators, two noncommutative generalizations of the Cauchy-Binet formula for the determinant of a product. As special cases we obtain elementary proofs of the Capelli identity from classical invariant theory and of Turnbull's Capelli-type identities for symmetric and antisymmetric matrices
Matrix Capelli identities related to Reflection Equation algebra
No full textBy using the notion of a quantum double we introduce analogs of partial
derivatives on a Reflection Equation algebra, associated with a Hecke symmetry
of GL(N) type. We construct the matrix L=MD, where M is the generating matrix
of the Reflection Equation algebra and D is the matrix composed of the quantum
partial derivatives and prove that the matrices M, D and L satisfy a matrix
identity, called the matrix Capelli one. Upon applying the quantum trace, it
becomes a scalar relation, which is a far-reaching generalization of the
classical Capelli identity. Also, we get a generalization of the some higher
Capelli identities defined by A.Okounkov
Energetics of swimming: a historical perspective.
No full textThe energy cost to swim a unit distance (C(sw)) is given by the ratio (E) over dot/v where (E) over dot is the net metabolic power and v is the swimming speed. The contribution of the aerobic and anaerobic energy sources to (E) over dot in swimming competitions is independent of swimming style, gender or skill and depends essentially upon the duration of the exercise. C(sw) is essentially determined by the hydrodynamic resistance (W(d)): the higher W(d) the higher C(sw); and by the propelling efficiency (eta(P)): the higher eta(P) the lower C(sw). Hence, all factors influencing W(d) and/or eta(P) result in proportional changes in C(sw). Maximal metabolic power ((E) over dot(max)) and C(sw) are the main determinants of swimming performance; an improvement in a subject's best performance time can more easily be obtained by a reduction of C(sw) rather than by an (equal) increase in (E) over dot(max) (in either of its components, aerobic or anaerobic). These sentences, which constitute a significant contribution to today's knowledge about swimming energetics, are based on the studies that Professor Pietro Enrico di Prampero and his co-workers carried out since the 1970s. This paper is devoted to examine how this body of work helped to improve our understanding of this fascinating mode of locomotion
The italian pilot study of the D-noses project: An integrated approach involving citizen science and olfactometry to identify odour sources in the area of castellanza (VA)
No full textThis work was developed within the Horizon 2020 D-NOSES project, with the purpose of validating a new methodology for odour pollution management based on citizen science. The work was carried out in the area of Castellanza, in the Region of Lombardy (Italy), and involved 4 plants that have been identified as potential causes for odour emissions. In this complex situation, it was proposed to combine the D-NOSES methodology with the "traditional"way involving olfactometric measurements and dispersion modelling, in order to identify the causes of the odour problem. The results of the olfactometric surveys allowed to identify the major odour emissions of the plants under investigation. Moreover, the preliminary analysis of the 358 odour observations collected in the period between May 14th and September 30th 2020 by a group of trained citizens, resulted in the disprove of the common belief that a particular product of the chemical plant caused the release of odorous chemical substances generating malodours at the municipal WWTP
Objets d’importation ou objets personnels ? La dotation de bord des marins au regard du grand commerce, l’exemple du dépotoir portuaire d’Arles-Rhône 3
No full textExperimental investigation of the internal flow field of a meso-scale whirl combustor
No full textIn the last decade the interest towards the development of small-scale power generation and propulsion systems based on combustion has grew up. One of the essential requirement to succeed in the development of such micro-power systems is the capability to design very efficient small-scale combustion chamber.
At the Politecnico di Milano a research work on a non-premixed centimeter scale (meso-scale) swirl combustor delivering about 100 W of thermal power has been carried out. The use of a tangential air injection along with a 90° impinging fuel jet has been used to achieve good combustion efficiency and flame stabilization over a wide range of operating parameter. The whirl motion should induce a recirculation zone which improve combustor performances, nevertheless actually no experimental data are available about the internal flow field and its relationship with the combustor performances. The experimental investigation of the internal flow field of the combustor has been carried out by means of laser Doppler velocimetry (LDV). Due to limitation in optical access only the radial and tangential component have been measured. Results evidenced that the vortex core is displaced from the geometrical axis and a quite quiescent low velocity region exists in the center of the combustor chamber
Assessment of cardiac output from noninvasive determination of arterial pressure profile in subjects at rest
No full texthe stroke volume of the left ventricle (SV) was calculated from noninvasive recordings of the arterial pressure using a finger photoplethysmograph and compared to the values obtained by pulsed Doppler echocardiography (PDE). A group of 19 healthy men and 12 women [mean ages: 20.8 (SD 1.6) and 22.2 (SD 1.6) years respectively] were studied at rest in the supine position. The ratio of the area below the ejection phase of the arterial pressure wave (A(s)) to SV, as obtained by PDE, yielded a "calibration factor" dimensionally equal to the hydraulic impedance of the system (Zao = A(s).SV-1). The Zao amounted on average to 0.062 (SD 0.018) mmHg.s.cm-3 for the men and to 0.104 (SD 0.024) mmHg.s.cm-3 for the women. The Zao was also estimated from the equation: Zao = a.(d + b.HR + c.PP + e.MAP)-1, where HR was the heart rate, PP the pulse pressure, MAP the mean arterial pressure and the coefficients of the equation were obtained by an iterating statistical package. The value of Zao thus obtained allowed the calculation of SV from measurements derived from the photoplethysmograph only. The mean percentage error between the SV thus obtained and those experimentally determined by PDE amounted to 14.8 and 15.6 for the men and the women, respectively. The error of the estimate was reduced to 12.3 and to 11.1, respectively, if the factor Zao, experimentally obtained from a given heart beat, was subsequently applied to other beats to obtain SV from the A(s) measurement in the same subject
Evolution of electronic noses from research objects to engineered environmental odour monitoring systems: A review of standardization approaches
No full textSince electronic noses are used more and more for air quality monitoring purposes, and in some countries are starting to have a legal value, there is a need for standardization and programs for the quality verification of instruments. Such quality programs have the aim to guarantee the main characteristics of the instrument for both the final user and local authorities, let the user establish a suitable maintenance procedure and give information on measurement uncertainty. One critical aspect when dealing with electronic noses for environmental odour monitoring is that environmental odours are complex mixtures that are not repeatable nor reproducible, giving that they are not suitable for quality verifications. This paper aims to review and discuss the different approaches that can be adopted in order to perform quality checks on electronic noses (e-noses) used for environmental odour monitoring, thereby referring to existing technical standards, such as the Dutch NTA 9055:2012, the new German VDI 3518-3:2018, and the Italian UNI 1605848 project, which directly refer to electronic noses. Moreover, also the European technical standards that are prescriptive for automatic measuring systems (AMSs) are taken into consideration (i.e., EN 14181:2014 and EN 15267:2009), and their possible applicability to electronic noses is investigated. Finally, the pros and cons of the different approaches are presented and discussed in the conclusions section
Criticità della risorsa idrica nel bacino del F. Treia (Lazio settentrionale)
No full textLe unità idrogeologiche dei Monti Sabatini e Cimini, appartenenti al dominio vulcanico del Lazio settentrionale, ospitano una consistente falda regionale che alimenta numerosi bacini idrografici, tra cui quelli del Lago di Bracciano – Fiume Arrone e del Fiume Treia.
Gli autori hanno affrontato le problematiche idrogeologiche con l’ausilio di tecnologia informatica, in modo tale da poter confrontare e quantificare la risorsa idrica attuale rispetto agli scenari riconosciuti per gli anni passati.
A tal fine sono state condotte più campagne di rilevamento piezometrico e delle portate in alveo nel periodo 2002-2003. I risultati di tali indagini, confrontati con quelli degli anni ’70, hanno messo in luce un depauperamento della falda idrica. L’abbattimento più consistente dei livelli di falda è stato riscontrato tra Monte Rocca Romana e Monterosi, mentre abbassamenti nell’ordine delle decine di metri sono stati riconosciuti in più settori a est del Lago di Bracciano.
E’ stata, inoltre, definita quantitativamente la ricarica, al fine di valutare l’influenza di tale fattore sul depauperamento comprovato dai rilievi idrogeologici effettuati.
Il confronto tra gli andamenti piezometrici attuali e storici ha consentito di realizzare la carta degli scenari piezometrici, ovvero di individuare le aree critiche, nelle quali l’entità del prelievo supera in maniera inaccettabile la ricarica.
Le finalità di questa ricerca costituiscono una novità per la regione sabatino-cimina e forniscono elementi di grande interesse applicativo, in particolare per la salvaguardia delle risorse e per lo sviluppo sostenibile.The hydrogeological units of the Monti Sabatini and Cimini, belonging to the volcanic domain of Latium region, host a large regional aquifer that feeds many river basins, including those of Lake Bracciano –Arrone River, and Lake Vico-Treia River. To evaluate the assessment of groundwater resources in these basins the authors conducted more piezometric campaigns and campaigns to measure the base flow of the river which are natural drainage of the aquifer during the period 2002-2003. The results of these investigations, compared with those of the previous survey campaigns (1970), have revealed a depletion of the aquifer. The most substantial reduction of groundwater levels was found between Monte Rocca Romana and Monterosi, while lowering of groundwater surface of tens of meters have been recognized in several areas east of Lake Bracciano. It has also been defined the amount of recharge, to evaluate the influence of this factor on the depletion of the aquifer. The comparison between the current and historical trends piezometric allowed to make the map of the piezometric scenarios, and to identify critical areas in which the amount of the levy exceeds the recharge. This study is useful for developing plans for protecting the groundwater resource
Physiological determinants of best performances in human locomotion.
No full textIn human locomotion, the metabolic power required ((E)over dot) to cover a given distance d, in the time t is set by the product of the energy cost of the locomotion (C), i.e. the amount of metabolic energy spent to move over one unit of distance, and the speed (nu = d t(-1)): (E)over dot = C nu = C d t(-1). Since, for any given d, nu is a decreasing function of t and C is either constant or increases with nu, it necessarily follows that (E)over dot is larger the smaller the value of t. Thus, for any given distance and subject, the shortest time will be achieved when (E)over dot is equal to the individual maximal metabolic power ((E)over dot (max)). In turn, (E)over dot (max) is a decreasing function of t: it depends upon the subject's maximal aerobic power (MAP) and on the maximal amount of energy derived from the full utilisation of anaerobic energy stores (AnS). So, if the relationship between C and nu in the locomotion at stake and the subject's MAP and AnS are known, his best performance time (BPT) over any given distance can be obtained by solving the equality (E)over dot (max)(t) = (E)over dot(t). This approach has been applied to estimate individual BPTs in running and cycling. In this paper, the above approach will be used to quantify the role of C, MAP, and AnS in determining BPTs for running, track cycling and swimming. This has been achieved by calculating the changes in BPT obtained when each variable, or a combination thereof, is changed by a given percentage. The results show that in all the three types of locomotion, regardless of the speed, the changes in BPT brought about by changes of C alone account for 45-55% of the changes obtained when all three variables (C, MAP and AnS) are changed by the same amount
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