One of the most significant current discussions in forward fall research is the effect of walking speed on the likelihood of a fall after a trip. Considering the limited research studies perturbing individual participants at multiple walking speeds, the objective of this research study was to determine how walking speed influences tripping responses and recovery. A tripping device was built to apply large impulsive perturbations to the left ankle and induce stumbling reactions in humans walking on a motorized treadmill. The tripping device and experimental set-up were successful in eliciting large EMG responses following a perturbation at slow, medium, and fast walking speeds. However, during the final stages of piloting, electrical and mechanical issues lead to a breakdown of the tripping device. As a result, only a single set of participant data was collected and able to be fully processed. None the less, the qualitative kinematic and EMG results suggest an increased ability is required to activate muscles to take a recovery step and successfully decelerate the forward trunk motion and ultimately recover from a trip at faster speeds compared to slower walking speeds. / text

Zugl.: Aachen, Techn. Hochsch., Diss., 2005.

No description available.

published_or_final_version / Urban Planning / Master / Master of Science in Urban Planning

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

The dissertation explores the ability of light to embody and enhance the spirit of place in the Big Bend section of West Texas. A series of surveys and research investigated and then paired elements of light and place that were designed, and installed or simulated, in four experiential case studies. The case studies were evaluated by published authors of light and place and the dissertation committee and deemed mostly successful. Light installations can be embodied and enhance the spirit of place, the installations which were experienced “live” did this most effectively.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

The recovery strategies after a trip vary depending on several conditions. The location, timing, and magnitude of the trip are determining factors as well as the speed of the subject when the trip occurs. Previous studies focused on the trip and the recovery without systematically varying the walking speed. Individuals at high risk of falls alter their walking speed in an effort to be more stable in case of a trip. However, no studies to date have analyzed the recovery strategies when walking faster and slower than preferred. Using a treadmill and a specially designed tripping device allows for subjects to be unsuspectingly tripped at different times and different speeds while measuring kinematic and EMG responses. The tripping device included a cuff attached to the left ankle of the subject and would stop the left ankle when signaled by the experimenter. From these findings we can infer that slower walking does aid in trip recovery. Although a more robust study should be performed to confirm the consistency of these findings across multiple populations, it seems that slower walking does aid in trip recovery. / text

Thesis (M.S.)--Tennessee Technological University, 2008. / Title from title page screen (viewed on Sept. 28, 2009). Bibliography: leaves 72-73.

The present manuscript addresses the computational modeling of size effects in the plastic behavior of metals at small scales. It is experimentally observed that the mechanical properties of metals are strongly affected when at least one microstructural length scale is scaled down to the micro/nanometer range or when the size of the object stands in the micron or sub-micron range. In such cases from a continuum point of view, the role of plastic strain gradients is considerable in controlling hardening properties. Classical theories of plasticity cannot predict such behavior since they don’t take any intrinsic material length scale parameter into account. For such cases, strain gradient plasticity has been developed to represent size effects. This project focuses on using a phenomenological strain gradient plasticity model to represent some aspects of size effects in metals.To this end, the strain gradient viscoplastic formulation with isotropic material response, based on the formulation developed by Borg et al. (2006), was implemented. Moreover, the strain gradient crystal viscoplastic formulation, according to the development of Borg (2007b), was implemented in a finite strain 2D setting. An extension of the finite strain rate-independent isotropic formulation (Niordson and Redanz (2004)), initially implemented by Mazzoni-Leduc (2010), to plane stress was performed and exploited. As a first application of the research, the rate-independent strain gradient formulation was first used to model the material behavior of Transformation Induced Plasticity (TRIP) assisted multiphase steels. This is done by an extension of the model, developed in Mazzoni-Leduc (2010) for local phase transformation features, by applying a special averaging scheme incorporating experimentally observed transformation kinetics of the phase transformation. Results show that the model stands in a good qualitative agreement with the experiments. The model is shown to have potential for material properties optimization as a perspective. As a second application, the strain gradient viscoplasticity formulations, for both the isotropic implementation and for the crystal plasticity effects, are used to model the compression of Copper micro-pillars. Computationally, the confinement effect is modeled, and experimental data are used to validate the approach. Results show the necessity of considering orientation-dependency of the material. The experimental plastic confinement effect is captured in a qualitative manner. Extension of the model to 3D and studying the grain size effect on bi-modal polycrystals are among the future plan of the work. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished