2,168 research outputs found

    A General Mathematical Formulation for the Determination of Differential Leakage Factors in Electrical Machines with Symmetrical and Asymmetrical Full or Dead-Coil Multiphase Windings

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    This paper presents a simple and general mathematical formulation for the determination of the differential leakage factor for both symmetrical and asymmetrical full and dead-coil windings of electrical machines. The method can be applied to all multiphase windings and considers Görges polygons in conjunction with masses geometry in order to find an easy and affordable way to compute the differential leakage factor, avoiding the adoption of traditional methods that refer to the Ossanna's infinite series, which has to be obviously truncated under the bound of a predetermined accuracy. Moreover, the method described in this paper allows the easy determination of both the minimum and maximum values of the differential leakage factor, as well as its average value and the time trend. The proposed method, which does not require infinite series, is validated by means of several examples in order to practically demonstrate the effectiveness and the easiness of application of this procedure

    New insights about the putative role of myokines in the context of cardiac rehabilitation and secondary cardiovascular prevention.

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    Exercise training prevents the onset and the development of many chronic diseases, acting as an effective tool both for primary and for secondary prevention. Various mechanisms that may be the effectors of these beneficial effects have been proposed during the past decades: some of these are well recognized, others less. Muscular myokines, released during and after muscular contraction, have been proposed as key mediators of the systemic effects of the exercise. Nevertheless the availability of an impressive amount of evidence regarding the systemic effects of muscle-derived factors, few studies have examined key issues: (I) if skeletal muscle cells themselves are the main source of cytokine during exercise; (II) if the release of myokines into the systemic circulation reach an adequate concentration to provide significant effects in tissues far from skeletal muscle; (III) what may be the role carried out by muscular cytokine regarding the well-known benefits induced by regular exercise, first of all the anti-inflammatory effect of exercise. Furthermore, a greater part of our knowledge regarding myokines derives from the muscle of healthy subjects. This knowledge may not necessarily be transferred per se to subjects with chronic diseases implicating a direct or indirect muscular dysfunction and/or a chronic state of inflammation with persistent immune-inflammatory activation (and therefore increased circulating levels of some cytokines): cachexia, sarcopenia due to multiple factors, disability caused by neurological damage, chronic congestive heart failure (CHF) or coronary artery disease (CAD). A key point of future studies is to ascertain how is modified the muscular release of myokines in different categories of unhealthy subjects, both at baseline and after rehabilitation. The purpose of this review is to discuss the main findings on the role of myokines as putative mediators of the therapeutic benefits obtained through regular exercise in the context of secondary cardiovascular prevention

    Proanthocyanidins from \u3ci\u3eHedysarum, Lotus\u3c/i\u3e and \u3ci\u3eOnobrychis\u3c/i\u3e spp. Growing in Sardinia and Sicily and Their Antioxidant Activity

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    Proanthocyanidins (PA), or condensed tannins, are a class of natural polyphenolic compounds, occurring in numerous plant species, including a number of economically significant forage legumes. These compounds are polymers of flavan-3-ols, and typically contain from 2 to 20 units. Their biological significance is still being debated and, in recent years, a great deal of attention has been focused on their role in ruminant nutrition. Evidence has indicated that PA, in a moderate concentration (0.5-5% DM), may have considerable importance in protecting dietary proteins against microbial degradation in the rumen, and in preventing bloat. The antioxidant activity (AA) is also an important feature for animal well-being (Barry & McNabb, 1999). In order to study the PA content related to the antioxidant activity, samples of Hedysarum, Lotus and Onobrychis spp. from Mediterranean environments have been considered and investigated

    Proanthocyanidins from \u3cem\u3eHedysarum, Lotus\u3c/em\u3e and \u3cem\u3eOnobrychis\u3c/em\u3e spp. Growing in Sardinia and Sicily and Their Antioxidant Activity

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    Proanthocyanidins (PA), or condensed tannins, are a class of natural polyphenolic compounds, occurring in numerous plant species, including a number of economically significant forage legumes. These compounds are polymers of flavan-3-ols, and typically contain from 2 to 20 units. Their biological significance is still being debated and, in recent years, a great deal of attention has been focused on their role in ruminant nutrition. Evidence has indicated that PA, in a moderate concentration (0.5-5% DM), may have considerable importance in protecting dietary proteins against microbial degradation in the rumen, and in preventing bloat. The antioxidant activity (AA) is also an important feature for animal well-being (Barry & McNabb, 1999). In order to study the PA content related to the antioxidant activity, samples of Hedysarum, Lotus and Onobrychis spp. from Mediterranean environments have been considered and investigated

    A Novel Multi-Objective Finite Control Set Model Predictive Control for IPMSM drive fed by a Five-Level Cascaded H-Bridge Inverter

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    In this work, a novel multi-objective voltage-vector-based finite control set model predictive control for a permanent magnet synchronous machine drive fed by a three-phase five-level cascaded H-bridge multilevel inverter is proposed. This algorithm aims to overcome the main issues relative to model predictive control implementation detected in the scientific literature for electric drives fed by cascaded H-bridge multilevel inverters. In detail, the goals are the minimization of computational cost by reducing the number of required predictions, the minimization of the switching devices state transitions, i.e. the switching losses minimization, and the common mode voltage reduction. These goals are fulfilled through an offline optimization process, thus, no additional terms and weighting factors to be tuned are required for the cost function. Experimental validations are presented to prove the effectiveness of the proposed approach. In detail, an accurate electric drive performance comparison, both in steady state and dynamic working conditions, is carried out when the proposed voltage-vector-based model predictive control and the cell-by-cell-based model predictive control are adopted. As comparison tools, current and voltage total harmonic distortion, apparent switching frequency, common mode voltage amplitude, and torque ripple are adopted

    Optimized Finite Control Set Model Predictive Control for a Three-Phase Five-Level Cascaded H-Bridge Multilevel Inverter fed Interior Permanent Magnet Synchronous Machine With On-Line Candidate Switching State Selection

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    Model predictive control is a novel control strategy that is attracting the scientific community due to the several advantages it offers, such as the ability to consider system nonlinearities, the possibility to synthesize a control for a MIMO system instead of multiple SISO, and so on. Control feasibility, due to the very high computational cost required to solve the optimal control problem, is a challenge. By considering electric drives fed by multilevel inverters, the control design is more challenging due to the increased number of available output voltage vectors. In this work, a simple algorithm for the voltage candidate reduction is presented: it allows for reducing the control computational cost, minimizing the switching losses, and minimizing dv/dt on phase voltage waveforms

    Effect of defoliation management and plant arrangement on yield and N2 fixation of berseem-annual ryegrass mixture

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    The research was carried out in a Mediterranean semi-arid environment on berseem clover, annual ryegrass and their mixture to study the effect of defoliation management [date of \ufb01rst cut (FC) 85, 119, 140, 169 days after sowing] and different plant arrangements (sowing the two components in alternate rows or in the same row) on yields, N content, N2 \ufb01xation and N transfer. The experimental design was a split-plot with four replications. The 15 N isotope dilution technique was used (8 kg N ha \u20131 as ammonium sulphate at 10 atom% 15 N excess) to evaluate the N2 \ufb01xation. Total seasonal DM yield was, on average, signi\ufb01cantly higher for FC119 and FC140 (approx. 12.3 t ha \u20131 ) than for FC85 and FC169 (approx. 10.6 t ha \u20131 ). Plant arrangement did not signi\ufb01cantly in\ufb02uence total yield of the mixture. However, the legume yield was higher (+20%; P<0.0001) in the same row than in alternate rows arrangement. N content of ryegrass was signi\ufb01cantly higher in the mixtures than in pure stand and in the \u2018same row\u2019 plant arrangement than in the \u2018alternate rows\u2019. Intercropped berseem always had a signi\ufb01cant higher % of Ndfa than the monocropped one (on average 74.7% and 57.7% respectively). The apparent transfer of \ufb01xed N from berseem to ryegrass was not detected in either plant arrangement

    Milk Thistle (Silybum Marianum L.) as a Novel Multipurpose Crop for Agriculture in Marginal Environments: A Review

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    Milk thistle (Silybum marianum (L.) Gaertn.) is a versatile crop that has adapted to the broadly different soil and environmental conditions throughout all continents. To date, the fruits (\u201cseeds\u201d) of the plant are the only reliable source of silymarin, which, given its recognized therapeutic effects and its many present and potential uses, has led to a significant re-discovery and enhancement of the crop in recent years. Overall, although many studies have been carried out globally on the bioactivity, phytochemistry, and genetics of milk thistle, few and discontinuous research activity has been conducted on its basic agronomy as well as on the farm opportunities offered by the cultivation of this species. However, the multiple potential uses of the plant and its reduced need for external inputs suggest that milk thistle can perfectly fit among the most interesting alternative crops, even for marginal environments. The growing interest in natural medicine, the increasing popularity of herbal dietary supplements, and the multiple possibilities for livestock feeding are all arguments supporting the idea that in many rural areas, this crop could represent a significant tool for enhancing and stabilizing farm income. However, several issues still have to be addressed. The species retains some morphological and physiological traits belonging to non-domesticated plants, which make the application of some common agronomic practices challenging. Furthermore, the lack of reliable field data devoted to the definition of suitable cropping protocols represents a major constraint on the spread of this crop among farmers. This review has therefore focused on updating information on the main morphological and phytochemical traits of the crop and its agronomic characteristics and novel uses. Several gaps in technical knowledge have been addressed, and further goals for experimental activity have been outlined in order to guide farmers eager to cope with the cultivation of such a challenging and resource-rich crop

    Milk production and physiological traits of ewes and goats housed indoor or grazing at different daily timing in summer

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    During a 6 week trial in summer, 3 homogeneous groups, each consisting of 5 Comisana ewes and 5 Rossa Mediterranea goats, grazed watered forage resources during day (D) or night (N), or were housed indoor and supplied with mowed herbage(H). Maximum THI peaked at 94 at the end of July, and was almost constantly higher of 80. Milk yield was higher in N than in D and H goats, whereas N ewes produced more milk than H group, but their milk yield was higher than D ewes only in the period with the highest THI values. The lower urea in N goat milk, and the higher casein in N ewe milk, seem to indicate a better efficiency in dietary nitrogen utilization of night grazing animals. N ewes showed lower SCC in milk, and higher incidence of clotting milk samples, in comparison to other ewes. N goats and ewes showed lower rectal temperature and pulse rate in the afternoon and, among metabolic parameters, higher hematic level of sodium. Night grazing was confirmed to be a management practice for increasing heat tolerance, to which goats appeared to be more sensitive in terms of milk yield
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