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Direct measurements have been made of the velocity of second sound in liquid helium over the temperature range T[subscript ʎ]-T from 1.3 x 10⁻² K to 5 x 10⁻⁶K. Using previously determined relationships for the specific heat, superfluld density, and thermal conductivity near the lambda point, consistency has been demonstrated between the measurements, velocities predicted by superfluld hydrodynamics, and certain scaling law predictions. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This study investigates the dynamics of circular saws at supercritical speeds. A classical governing equation of a circular saw subjected to transverse and membrane forces is derived in both body-fixed and space-fixed coordinate systems. The transverse loads are generalized as spring, damping and out of plane cutting forces, and the membrane loads include rotational, thermal and in-plane cutting forces. Galerkin's Method is used to study the natural and forced response of a saw blade, and the effects of spring and damping on the stability at supercritical speed are discussed. An idling experiment is conducted to comprehend the fundamental behavior of circular saws at supercritical speed. The natural frequency, the steady state response, the flexibility and the runout variation of the circular saws are measured. The nonlinear vibration of the thin blade is observed. The effects of a spring-damper system and heating on the stability of a circular saw are investigated. A cutting test is conducted to find out the dominant parameters of supercritical speed cutting. At first, the prehminary experiments of the standard blade are conducted. Then, tip side cutting marks are discussed, and finally, the phenomenon of unstable cuttings are presented. The general solution of a rotating string subject to an elastic constraint is developed. Based on this, the discrepancy between theoretical and experimental stability results is analysed for a guided rotating disk. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

With the introduction of 4G LTE, multiple new technologies were introduced. MIMO is one of the important technologies introduced with fourth generation. The main MIMO modes used in LTE are open loop and closed loop spatial multiplexing modes. This thesis develops an algorithm to calculate the threshold values of UE speed and SNR that is required to implement a switching algorithm which can switch between different MIMO modes for a UE based on the speed and channel conditions (CSI). Specifically, this thesis provides the values of UE speed and SNR at which we can get better results by switching between open loop and closed loop MIMO modes and then be scheduled in sub-channels accordingly. Thus, the results can be used effectively to get better channel capacity with less ISI. The main objectives of this thesis are: to determine the type of MIMO mode suitable for a UE with certain speed, to determine the effects of SNR on selection of MIMO modes, and to design and implement a scheduling algorithm to enhance channel capacity.

The object of this research was to develop a technique that could measure the velocity of light indirectly, with some degree of accuracy; yet could be used to demonstrate the physical fact of this velocity of light to groups of students or interested observers.

The experimental program presented in this paper explores a passive acoustic baseball bat swing speed measurement technique to aid in product development and certification and to gauge player performance. The collection of experimental information is performed in two facilities?a swing/hit facility and a wind tunnel facility. The data acquired are pressures and velocities in the vicinity of the bat. Potential flow theory is utilized to better understand the signals generated in the experimental collection of data and to determine the fundamental relations applicable to the subsequent flow field produced by a moving bat. The measured flow resembles potential flow but with a distortion due to bat acceleration. The theoretical and experimental results are compared, and a qualitative similarity in the results is established.

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No description available.

Strength and conditioning professionals spend a great deal of time and effort trying to improve athletic performance. Even as coaches evaluate each athlete by using the results of a vast battery of tests, there has been considerable speculation and discussion about the physical attributes of Division I football players and their playing status. The purpose of this study was to determine what influence strength, power, and performance tests scores have on an individual's playing status. The Skill group results indicate that power is the most important factor differentiating between starters and non-starters. Simultaneously, the Combo group results indicate that speed is the most important factor differentiating between starters and non-starters. Also, the L.O.S. group results indicate that bodyweight is the most important factor differentiating between starters and non-starters. / Ph. D.

Master of Science / Department of Civil Engineering / Sunanda Dissanayake / Speed management has been a challenge, particularly in places where high-speed highways pass through. Due to high rate of fatalities and low budgets available, it is therefore necessary to identify low-cost effective approaches in reducing speeds. Optical Speed Bar (OSB) treatment is one such technique. This research makes an attempt to evaluate the effectiveness of OSBs in reducing approach speeds on two-lane, rural highways approaching small communities. Speed data were collected and analyzed “before” and “after” periods at five sites. Effectiveness of OSBs was evaluated using changes in mean and 85th percentile speeds under different categories by considering all vehicles, vehicle classification (two axles vs. more than two axles), day of the week (weekdays vs. weekends), and time of day (daytime vs. nighttime), as well as proportions exceeding posted speed limit, using t-test mean speeds, F-test for analysis of variance, and Z-test for proportions of vehicles exceeding posted speed limit between “before” and “after” datasets. Even though motorists were found to slow down on the approaches, in response to speed zones, speeding was noted. “Before” speed data indicated higher speeds than desired at the sites. The 85th percentile speeds were between 50 and 63 mph while the posted speed limits on the approaches were 45 mph at four sites, and the 85th percentile speed was about 42 mph at one site with an approach posted speed limit of 30 mph. The “before” degrees of noncompliance were up to 90 % of free-flowing vehicles at the sites. Speed data analysis showed significant reductions in speeds at ends of OSBs at four test sites. Mean and 85th percentile speeds and standard deviations were found reduced in the after periods. Percent reductions in mean speeds were between 1.2 and 8.2 %, with 85th percentile reductions between 3.2 and 8.9 %. At one site, no notable change in mean and 85th percentile speeds occurred at the end of OSBs, but significant increases in standard deviations were noted. Speed reductions were higher for two-axle vehicles, during the daytime and on weekdays with few exceptions. Results of the study showed, as other previous studies did, OSBs may have some minor effects on vehicle speeds. The study provides an indication that it may be possible to create safety improvements as result of using OSBs on the approach to a rural community. However, magnitude of speed reductions was generally small, though the reductions were statistically significant at the 95% confidence level. Because of the non-consistence of the magnitude of speed reductions at the test sites, no conclusion can be drawn as to how much OSB treatment reduced speeds. These results were based on “after” periods up to five months. Therefore, further study would be required to determine whether these safety improvements are sustained over an even longer time period. Even though minor speed reductions occurred, speeds observed at the sites were still higher than the posted speed limits, indicating OSBs were not effective enough in providing the desired speed limit compliance. Additional studies would be helpful to identify combinations of countermeasures, for instance OSBs and other techniques, effective in providing speed limit compliance.