Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 91-95). Also available via the Internet.

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Study of the dynamics of strings and filaments has broad applications, for instance, macroscopic coil motion in petroleum engineering and microscopic one-armed swimmers in biological science. In this work, we study the motions of flexible strings and thin filaments in two different regimes, inertial and viscous, theoretically and experimentally. Quantitative experiments on the whirling string show that steady motion exists only when the string whirls at its natural frequencies and that whirling motions for other frequencies exhibit rich dynamics. Furthermore, three kinds of response have been observed experimentally for the planar excitation: planar steady oscillation; two-dimensional (2D) to three-dimensional (3D) transient response; 3D steady whirling motion. These phenomena repeat as the driving frequency is increased. The forced response of a string subjected to planar excitation is analyzed through a perturbation technique and multiple time scale method. The steady-state whirling motion of linear elastic filaments under self-weight with rotary excitation at one end and free at the other has been examined; specifically, the effect of bending stiffness has been investigated both theoretically and experimentally. The theoretical predictions have been compared with the experimental results for thin filaments with different bending stiffness to demonstrate the effect of bending stiffness directly. The dynamic response of thin filaments under planar excitation has also been studied experimentally. The two-dimensional dynamics of an Euler elastica in low-Reynolds number regime has been studied. Tension effects have been shown to be either comparable to or dominant over the bending contributions for the microscopic one-armed swimmers. Hence one may change the tension in situ through the externally or internally generated forces, thus changing the effective bending stiffness, and as a consequence controlling the swimming velocity and the propulsion efficiency. Finally, the low-Reynolds-number dynamics of a micro-string has been studied, in order to understand the physics underpinning eukaryotic sperm flagellar swimming. Both linear analysis of small-amplitude swimming and fully numerical simulations show that time-reversal symmetry is broken, which leads to the propulsion. Numerical studies have been performed for different boundary conditions and different forcing levels. Comparison with previous bending model illustrated that, for the same equivalent bending stiffness, the micro-string has higher propulsion efficiency with similar swimming velocity. Excellent agreement between the simulation predictions and the experimentally observed flagellar wave-forms has been obtained. With this theoretical model, observations of swimming characteristics of the sperm of different species are reconciled into a single scaling relationship, characterized by the so-called \string sperm number". Our results imply that tension plays a crucial role in flagellar elasticity and provides impetus for studying a different model underlying the physics of flagellar swimming. For example, it is possible to postulate alternate hypotheses for active force generation by the dynein motors; it also enables the formulation of a different role to the micro-filaments in general, one based on tension rather than one based on bending.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (M.S.)--California Polytechnic State University, 2009. / Mode of access: Internet. Title from PDF title page; viewed on March 17, 2009. Major professor: Robert D. Clark, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Kinesiology." "March 2009." Includes bibliographical references (p. 41-44). Also available on microfiche.

Thèse : Astronomie : Faculté des sciences de Paris : 1858. Thèse : Mécanique : Faculté des sciences de Paris : 1858. / Titre provenant de l'écran-titre.

Thesis (Ph.D.)--Tufts University, 2001. / Adviser: Chris Rogers. Submitted to the Dept. of Mechanical Engineering. Includes bibliographical references (leaves 140-146). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

The objective of this study was to determine the correlation of the drag coefficient of an accelerating sphere in the liquid medium over a range of Reynolds number from 0.1 to 100, 000. A magnetic accelerator was used to obtain an acceleration for the sphere, the data was recorded using a photograph and a digital computer was used to reduce the data.

The purpose of this research was to study the human ability to perceive inertia and to investigate the relationship between individual sensitivity to mass discrimination and the accuracy of inertia judgment. The study involved two major experiments, a mass discrimination test to provide a measure of kinesthetic sensitivity and a push/aim task to measure inertia perception. The experimental apparatus allowed for the manipulation of an inertial load for both the mass discrimination test and the push/aim task. The mass discrimination test was based on the method of constant stimuli and involved a standard stimulus of 30 kg and seven comparison stimuli ranging from 24.3 kg to 35.7 kg. It determined Weber fraction values which were used as a measure of sensitivity. The push/aim task simulated a dynamic horizontal pushing task and was restricted to an initial exertion causing the inertial load to travel to a target under its own momentum. Performance was measured by the errors associated with the accuracy of the aimed pushes. These errors were separated into an absolute component representing an overshoot or undershoot, and a relative measure of error representing variability of repeated trials about the absolute error. Distance to the target (2 or 6 m), amount of load (25, 45, or 90 kg), and apparent size of the load (small or large) were manipulated in the dynamic pushing experiment. Hypothesis testing was used to determine whether performance exhibited a consistent overshooting or undershooting of the target. An ANCOVA was used to measure the effects of distance, amount of load, and apparent size on performance given a covariate of mass discrimination sensitivity. Since the ANCOVA showed no significant effect from the covariate, an ANOVA was used to analyze the effects of the independent variables on both measures of error. The hypothesis tests revealed that absolute error in the push/aim task was significant by less than zero for the combined data set and at all levels of independent variables, indicating a consistent undershoot of the target. The ANCOVA results il indicated no significant effect from the covariate, mass discrimination Correlation coefficients (R2) were calculated for the relation between sensitivity to mass discrimination and push/aim task performance with respect to absolute and relative error. These values were 0.004 for the absolute error and 0.008 for the relative error. The ANOVA results revealed that weight, distance, and the weight x distance interaction had significant effects on the absolute measure of error. Increasing the levels of either weight or distance resulted in significant increases in the amount of absolute error. Increasing the distance resulted in significant increases in the amount of relative error. The presence of a distance effect and the absence of a weight effect indicates the importance of rate of force over amount of force in the relative error associated with the push/aim task. Apparent size of the load did not have a significant effect on either absolute or relative error. / Master of Science