Aerodynamics Of Soccer Balls And Volleyballs

The purpose of this study was to investigate range, flight time, speed and trajectory of selected official soccer balls and volleyballs in a constant release angle (18 degree) shot by a ball gun with a hydraulic shooting steel leg mechanism in an indoor soccer hall. Five soccer balls (m=0.422 ± 0.010 kg, d=0.108 + 0.002 rn, p=(0.69 + 0.01) x 105 Nm-2) and five volleyballs (m=0.278 ± 0.006 kg, d=0.105 + 0.002 rn, p=(0.69 ±0.01) x 105 Nm-2) were used. Three speeds of the kicking steel leg were applied to the stationary and rotating balls with two constant angular velocities (45.6 and 65.0 radls). All shots of the balls were recorded with two JVC 707 5-VHS camcorders (50 Hz) for kinematic and kinetic motion analysis. An APAS performance analysis system was used for detailed 3D analysis of the release phase of the shot. The range of the ball was measured in x-z coordinates on the Astroturf ground. A Panasonic camcorder with timer was used to measure the flight time of the ball. A 3- way ANOVA was applied in order to study the differences of the balls and their behaviour in the placid air. The release velocities of the stationary soccer balls with three speed categories .were 18.8 + 0.1 ms·1, 23.1 ± 0.1 msand 26.5 ± 0.1 ms-1 and in volleyballs 20.5 ± 0.2 ms-I, 25.6 ± 0.2 ms-1 and 29.4 ± 0.2 ms-1, respectively. The range of the fastest shot off the soccer balls was on average 44.8 m with the lateral deviation of 3.3 degrees. The average range of the volleyballs in the fastest shots without spin was 45.2 m with the lateral deviation of 4.8 degrees. The average ground speeds in the fastest shots of the soccer ball and volleyball were 20.6 ms-1 and 24.7 ms-1, respectively. With the fastest spin and shot the range and deviation of soccer balls and volleyballs were 34.4 m and 38.6 m and 19.7 and 21.4 degrees, respectively. The main effects of the ball type, shot speed and spin were significant (

Strain-Rate Frequency Superposition in Large-Amplitude Oscillatory Shear

In a recent work, Wyss, {\it et.al.} [Phys. Rev. Lett., {\bf 98}, 238303 (2007)] have noted a property of `soft solids' under oscillatory shear, the so-called strain-rate frequency superposition (SRFS). We extend this study to the case of soft solids under large-amplitude oscillatory shear (LAOS). We show results from LAOS studies in a monodisperse hydrogel suspension, an aqueous gel, and a biopolymer suspension, and show that constant strain-rate frequency sweep measurements with soft solids can be superimposed onto master curves for higher harmonic moduli, with the {\it same} shift factors as for the linear viscoelastic moduli. We show that the behavior of higher harmonic moduli at low frequencies in constant strain-rate frequency sweep measurements is similar to that at large strain amplitudes in strain-amplitude sweep tests. We show surface plots of the harmonic moduli and the energy dissipation rate per unit volume in LAOS for soft solids, and show experimentally that the energy dissipated per unit volume depends on the first harmonic loss modulus alone, in both the linear and the nonlinear viscoelastic regime.Comment: 10 pages, 25 figures, accepted for publication in Physical Review E. Incorporates referee comment

Integrated optics sensors for multi-sensing platforms

An overview is presented of research projects on optical sensing, in the Integrated Optical MicroSystems group of the MESA+ Institute for Nanotechnology at the University of Twente

Rationality as the Rule of Reason

The demands of rationality are linked both to our subjective normative perspective (given that rationality is a person-level concept) and to objective reasons or favoring relations (given that rationality is non-contingently authoritative for us). In this paper, I propose a new way of reconciling the tension between these two aspects: roughly, what rationality requires of us is having the attitudes that correspond to our take on reasons in the light of our evidence, but only if it is competent. I show how this view can account for structural rationality on the assumption that intentions and beliefs as such involve competent perceptions of downstream reasons, and explore various implications of the account

An update of clinical management of acute intermittent porphyria

Peer reviewe

Enhanced Tunnelling in a Hybrid of Single-Walled Carbon Nanotubes and Graphene

Transparent and conductive films (TCFs) are of great technological importance. The high transmittance, electrical conductivity and mechanical strength make single-walled carbon nanotubes (SWCNTs) a good candidate for their raw material. Despite the ballistic transport in individual SWCNTs, however, the electrical conductivity of their networks is limited by low efficiency of charge tunneling between the tube elements. Here, we demonstrate that the nanotube network sheet resistance at high optical transmittance is decreased by more than 50% when fabricated on graphene and thus provides a comparable improvement as widely adopted gold chloride ($\mathrm{AuCl_3}$) doping. However, while Raman spectroscopy reveals substantial changes in spectral features of doped nanotubes, no similar effect is observed in presence of graphene. Instead, temperature dependent transport measurements indicate that graphene substrate reduces the tunneling barrier heights while its parallel conductivity contribution is almost negligible. Finally, we show that combining the graphene substrate and $\mathrm{AuCl_3}$ doping, the SWCNT thin films can exhibit sheet resistance as low as 36 $\Omega$/sq. at 90% transmittance.Comment: 21 pages, 6 figure