Research study of droplet sizing technology leading to the development of an advanced droplet sizing system

An instrument to measure the size and velocity of droplets was developed. The instrument uses one of two techniques, as appropriate. In the first technique two small laser beams of one color identify the center of a larger laser beam of a different color. This defines a region of almost uniform intensity where the light scattered by the individual droplets can be related to their size. The first technique uses the visibility of a Doppler burst and validates it against the peak intensity of the signal's pedestal. Results are presented for monodisperse, bimodal, trimodal, and polydisperse sprays produced by the Berglund-Liu droplet generator and a pressure nozzle. Size distributions of a given spray obtained using three different size ranges show excellent self-consistency in the overlapping region. Measurements of sprays of known characteristics exhibit errors in the order of 10%. The principles of operation and design criteria of the instrument are discussed in great detail

Self collimation of ultrasound in a 3D sonic crystal

We present the experimental demonstration of self-collimation (subdiffractive propagation) of an ultrasonic beam inside a three-dimensional sonic crystal. The crystal is formed by two crossed steel cylinders structures in a woodpile-like geometry disposed in water. Measurements of the 3D field distribution show that a narrow beam which diffractively spreads in the absence of the sonic crystal is strongly collimated in propagation inside the crystal, demonstrating the 3D self-collimation effect.Comment: 3 figures, submitted to Applied Physics Letter

The Effect of Pack Size on Finish Time in the Fukuoka Marathon

Elite marathon runners have been pushing the limits of the human body, currently setting the world record near two hours. Notable factors while running include physiological, psychological, and strategic factors. Utilizing pack running may be a strategic factor to improve finish time and placement. Purpose To explore the effect of individuals running in various size packs on their place and finish time in the Fukuoka Marathon. This race has seen some of the most talented runners in history, as the world record has been broken twice at the Fukuoka Marathon, in 1967 and 1981. Methods The data set of results was received through a collaboration with Dr. Michael Joyner, of the Mayo Clinic. Subjects running in the Fukuoka Marathon in Fukuoka, Japan were all male (n=240). Marathon race times and splits was analyzed from the year 1967 through 2014. Race splits were recorded every five kilometers and at the halfway point. Only runners who finished in the top five were used to record pack sizes. Pack sizes were counted for every top five finisher at each split and a mean pack size was calculated. Finish times were normalized to the winning time of each race. One-way ANOVA test was performed to quantify the effect of mean pack size on finish time. Results No significant correlation was found between mean pack size and finish time for top five finishers (p=0.793). Regressions of mean pack size during the first half, second half, and entirety of the race yielded a slope of zero. Conclusion Although pack size and finish time were not significantly correlated, there were non- significant trends within the data that showed possible relation between place, size, and the duration of a pack that an individual ran with. Further studies should explore psychological benefits of racing in a pack, pack sizes outside of the top ten finishers, whether place within an individual pack is relevant to finish time, how individuals changing packs effects race dynamics, and if top finishers should be excluded from the pack pacing hypothesis

Flux-cutting and flux-transport effects in type-II superconductor slabs in a parallel rotating magnetic field

The magnetic response of irreversible type-II superconductor slabs subjected to in-plane rotating magnetic field is investigated by applying the circular, elliptic, extended-elliptic, and rectangular flux-line-cutting critical-state models. Specifically, the models have been applied to explain experiments on a PbBi rotating disk in a fixed magnetic field ${\bm H}_a$, parallel to the flat surfaces. Here, we have exploited the equivalency of the experimental situation with that of a fixed disk under the action of a parallel magnetic field, rotating in the opposite sense. The effect of both the magnitude $H_a$ of the applied magnetic field and its angle of rotation $\alpha_s$ upon the magnetization of the superconductor sample is analyzed. When $H_a$ is smaller than the penetration field $H_P$, the magnetization components, parallel and perpendicular to ${\bm H_a}$, oscillate with increasing the rotation angle. On the other hand, if the magnitude of the applied field, $H_a$, is larger than $H_P$, both magnetization components become constant functions of $\alpha_s$ at large rotation angles. The evolution of the magnetic induction profiles inside the superconductor is also studied.Comment: 12 pages, 29 figure