1,720,998 research outputs found
Investigation of the influences of tyre-road friction and engine power on motorcycle racing performance by means of the optimal manoeuvre method
No full textThis paper investigates the influences of the tyre-road friction and of the maximum engine power on the performance of a racing motorcycle. For this purpose the optimal manoeuvre method is applied, which essentially simulates an ideal driver and computes the minimum lap time for a given motorcycle and a given track. The absolute performance of a racing motorcycle is strictly related to the braking and acceleration capabilities. Braking is limited by front- or rear-tyre skidding and by a stoppie event, whereas acceleration is limited by rear-tyre skidding and by a wheelie event. Furthermore, the engine power constitutes a limiting factor during propulsive phases. Effectively the weights of these limiting factors change with the tyre-road friction condition and with the engine power availability. As a consequence, the manoeuvrability of a racing motorcycle varies and riders need to adjust their strategies properly in order to achieve the best performances allowed in any condition. For this purpose a simple L-curve manoeuvre is considered in this paper. First, a detailed description is reported, and then brake and acceleration limiting conditions are considered with respect to a reference configuration. Next, a parametric analysis is carried out at variable friction and maximum engine power, and their influences on lap time are examined. Finally, two representative configurations are evidenced, i.e. lower friction and lower power; furthermore, brake and acceleration limiting conditions are derived analytically by means of a simplified motorcycle model. Accordingly, the representative manoeuvres are interpreted, and the influences of the friction and engine power on curve entering and curve exiting using optimal strategies is examined
Isothermal vapor-liquid equilibria for the binary system 1,1,1- trifluoroethane (R143a)+1,1,1,3,3,3-hexafluoropropane (R236fa) at 283.11, 298.16, and 313.21 K
No full textA recirculation apparatus in which the vapor phase was forced through the liquid was used to measure isothermal vapor - liquid equilibria (VLE) for the binary system 1,1,1-trifluoroethane (R143a) + 1,1,1,3,3,3-hexafluoropropane (R236fa) at 283.11, 298.16, and 313.21 K. The phase composition at equilibrium was measured with a gas chromatograph that was calibrated with gravimetrically prepared mixtures. The system shows a small deviation from Raoult's law. The data were reduced with the Carnahan-Starling-De Santis (CSD) equation of state. The deviations observed in vapor composition suggest a relatively good consistency of the experimental findings and the model used for their reduction
NOCIRC of Italy: Scientific activities 2006-2009
No full textAs the majority of Italians are not circumcised, the knowledge of the various aspects of male circumcision (MC) is lacking. The waves of immigrants from Muslim countries presented various problems concerning ritual MC, among them the fact that an ambiguous legislation enabled fraudulent use of National Health Services (NHS) funding, as ritual MCs were falsely labelled as being therapeutic in order to have them performed for free under the NHS. To better understand MC in Italy, during the last three years, different graduation theses supervised by the author permitted the gathering of: (a) epidemiological data to update the first epidemiological survey on the topic, (b) the attitudes of 173 Italian urologists toward MC, that were assessed by means of a questionnaire during a national medical congress. A previous thesis allowed (c) the production of the questionnaire administered to these professionals and, finally, (d) interviews were carried out. They were performed in the 15 health facilities supposed to carry out ritual MC, in order to build a map of these facilities in Italy and to better understand the underlying motivations and implications. Data confirm the fact that MC in Italy exists as a delicate, underground, and multifaceted problem. It appears that, behind the scenes, not only unnecessary interventions are performed but also that legal violations are common
Application of the "Optimal Maneuver Method" for enhancingracing motorcycle performance
No full textThe aim of this work is to improve the performance of a racing motorcycle by means of gearbox tuning. The Optimal Maneuver Method, which essentially simulates an ideal driver and computes the minimum Lap Time for a given motorcycle and a given circuit, is applied. A 1000cc SuperBike motorcycle and two very different racetracks, i.e. a fast one and a slow one, are considered. First the agreement between the Optimal Maneuver Method results and the logged telemetry data is proven, in order to fully justify its application. Next the relationship between gearbox ratio, lap performance and circuit characteristics is investigated and potential improvements are highlighted. Finally gearbox tuning is achieved by a Lap Time optimization procedure, and subsequent performance improvements are discussed
Saturated Pressure Measurements of 2,3,3,3-Tetrafluoroprop-1-ene (R1234yf) for Reduced Temperatures Ranging from 0.67 to 0.93
No full text2,3,3,3-Tetrafluoroprop-1-ene (R1234yf) is one of the most promising alternative refrigerants because of its low global warming potential and a vapor pressure similar to 1,1,1,2-tetrafluoroethane (R134a). At present, its measured thermodynamic properties are scarce. Herein, vapor pressure data measurements and corresponding correlations are discussed. In particular, 40 vapor pressure measurements in the temperature range between (245.65 and 343.15) K were obtained, and these results, together with available literature data, were regressed using Wagner-type and extended Antoine-type equations. The normal boiling temperature for R1234yf was calculated to be 243.71 K
Gas chromatographic measurements of activity coefficients at infinite dilution for refrigerants with a polyol ester oil as a stationary phase
No full textActivity coefficients at infinite dilution have been measured by gas chromatography for 14 refrigerants (R12, R22, R32, R124, R125, R134a, R142b, R143a, RE170, R236ea, R290, R600, R600a, and R236fa) as solutes, using a polyol ester oil (POE), EMKARATE by ICI, as a stationary phase (solvent). Instrumental analysis (NMR, IR) showed that the main components of the oil are pentaerithritol esters of carboxylic acids, and electrospray ionization spectrometry revealed an average molecular mass of the POE of 618 g·mol-1. The measurements were performed within a temperature range of 244 K to 313 K, but a specific temperature range for each refrigerant was adopted depending on its retention data. The experimental findings are well-represented by the equation: ln γi∞ = a1 - bi/T. Some refrigerants, i.e., R22, R124, R125, R236ea, and R236fa, show quite a considerable positive temperature dependence of their activity coefficients at infinite dilution, which can be attributed to hydrogen bonding with the POE, unlike other refrigerants that show a small, either positive or negative temperature dependence. To our knowledge, there are no data in the literature on activity coefficients at infinite dilution for refrigerant and oil (lubricant) systems, and details on the solubility of refrigerants in oils are also extremely scarce
HCFO refrigerant cis-1-chloro-2,3,3,3 tetrafluoropropene [R1224yd(Z)]: Experimental assessment and correlation of the liquid density
No full textIn the search for substitutes for high global warming potential (GWP) refrigerants, measurements of thermodynamic properties for refrigerants belonging to new halogenated olefins group (HFO) is of strict actuality, due to their GWP, close to that of natural refrigerants, and the lack of information on their properties. One of the most interesting HFOs is cis-1-chloro-2,3,3,3-tetrafluoropropene (R1224yd(Z)), suitable, for its relatively high NBP (287.15 K) and its low vapour pressure, to be used in applications such as Organic Rankine Cycles (ORC), industrial high temperature heat pumps or centrifugal chillers. The paper presents 90 experimental compressed liquid density data for R1224yd(Z) in a range of temperatures and pressures varying from 283.15 K and 363.15 K and from close to saturation pressure up to 35 MPa, respectively. The data were measured by means of a vibrating tube densimeter at isothermal conditions. By extrapolating the isothermal compressed liquid density data at the saturated pressure, 10 saturated liquid density values have also been obtained. A Tait correlation for the compressed liquid density data and a dedicated correlation for the saturated liquid density are presented. Both correlations well represent the experimental data, with a percentage absolute average deviation (AAD%) of 0.1% in both cases. Experimental liquid density data have been compared to literature through the most updated version of the fundamental equation of state proposed by (Akasaka et al., 2017). The equation shows a very good agreement with the present data, considering that most of the data are in the extrapolation areas of the equation
A Ricirculation Apparatus for Vapor-Liquid Equilibrium Measurements of Refrigerants. Binary Mixtures of R600a, R134a and R236fa
No full textAn apparatus for the measurement of vapor-liquid equilibria (P-T-x-y) data of refrigerant systems was designed, built and tested. The recirculation method was used and the vapor phase was forced through the liquid phase by a magnetic pump. The thermodynamic equilibrium was reached in a visual cell with an internal volume of 50 cm(3). The compositions of the phases were analyzed by a gas chromatograph connected on-line with either FID or TCD detectors. The operating temperature and pressure in the apparatus, as tested before delivery to the laboratory [R. Stryjek, personal communication], range from 240 to 350 K and from 0.1 to 10 MPa, respectively. The estimated accuracy of the measured data was +/-0.01 K for temperature, +/-0.8 kPa for pressure and 0.001 in mole fraction for liquid and vapor compositions. Vapor-liquid equilibria data were obtained for the following systems: 1,1,1,2-tetrafluorethane + isobutane (R134a + R600a) at 293.66 and 303.68 K; 1,1,1,2-tetrafluorethane + 1,1,1,3,3,3-hexafluoropropane (R134a + R236fa) at 283.62 and 303.68 K; and isobutane + 1,1,1,3,3,3-hexafluoropropane (R600a + R236fa) at 303.68 K. The thermodynamic consistency of the experimental results was tested
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