Instability of humanoid robots is a common problem, especially given external disturbances or difficult terrain. Even with the robustness of most whole body controllers, instability is inevitable given the right conditions. When these unstable events occur they can result in costly damage to the robot potentially causing a cease of normal functionality. Therefore, it is important to study and develop methods to control a humanoid robot during a fall to reduce the chance of critical damage. This thesis proposes joint angular velocity strategies to reduce the impact velocity resulting from a lateral, backward, or forward fall. These strategies were used on two and three link reduced order models to simulate a fall from standing height of a humanoid robot. The results of these simulations were then used on a full degree of freedom robot, Viginia Tech's humanoid robot ESCHER, to validate the efficacy of these strategies. By using angular velocity strategies for the knee and waist joint, the reduced order models resulted in a decrease in impact velocity of the center of mass by 58%, 87%, and 74% for a lateral, backward, and forward fall respectively in comparison to a rigid fall using the same initial conditions. Best case angular velocity strategies were then developed for various initial conditions for each falling direction. Finally, these parameters were implemented on the full degree of freedom robot which showed results similar to those of the reduced order models. / Master of Science

Liquid films falling under the influence of gravity are widely encountered in a variety of industrial two-phase flow applications (distillation columns, nuclear reactor cores, etc.). In addition, the falling annular film represents a fundamental limiting case of the annular flow regime of two-phase gas-liquid flows. The literature on annular falling films is dominated by studies concerning the average film thickness. Information on more detailed characteristics of the film thickness variations and information on the velocity profile within the film and wall shear stress are much less common. The statistical description of the film thickness is complicated by the fact that practically all flows of interest occur in the turbulent regime. Due to the complex and unsteady nature of the turbulent annular falling film, no complete theories or models have yet been developed on the subject. Experimental studies are needed to gain insight into the basic mechanisms that govern this complex flow.<p>The primary purpose of this thesis research was to characterise the film thickness of falling annular films at high and very high Reynolds numbers using non-intrusive imaging techniques. Another objective was to develop ray-tracing techniques to reduce optical distortion and obtain high-quality experimental data. <p>Instantaneous film thickness measurements of falling annular films were extracted at five different Reynolds numbers in the range Re = 1000 ~ 6000 for the fully developed turbulent regime using an automated optical measurement technique. From visual observation of the images obtained it was found that waves were not axisymmetric, i.e., there was substantial azimuthal variation in film thickness. The turbulent waves appeared to be similar in appearance to very large breaking ocean waves driven by strong winds. The random nature of these falling annular films was subjected to statistical analysis.<p>Statistical characteristics of film thickness were studied at Reynolds numbers in the range Re = 1000 ~ 6000. A correlation for dimensionless mean film thickness was obtained in the turbulent flow regime. The dimensionless mean film thickness obtained here was found to be in reasonable agreement with the other established experimental and theoretical studies. It was shown that the Reynolds number influences the statistical characteristics of film thickness such as standard deviation and coefficient of variation. The additional data obtained here shows that the standard deviation continues to increase in proportion to the mean film thickness in the turbulent regime. In other words, in the lower turbulent zones the films are thin and less wavy, whereas in the higher turbulent zones the films are thicker and extremely wavy in nature.<p>The probability density distributions were also obtained. It was found that the measured probability density distributions were asymmetric. They all had a maximum peak and were skewed to the right hand side with a long tail that stretched to over six times the peak value. The maximum peak could be considered to represent the modal value of the film thickness or the substrate film thickness. The increase in skewness and the decrease in the height of the peak with liquid Reynolds number could be attributed to the presence of large disturbance waves which ride on the substrate film. This enhances the waviness of the film.<p>A common problem in imaging flows in cylindrical tubes is the optical distortion caused by the wall curvature. To minimize this problem the cylindrical tube was surrounded by an optical correction box with flat walls filled with water. In addition, an advanced ray tracing model was employed to reduce optical distortion effects in the cylindrical tube. This technique increased the accuracy of the imaging technique and enabled quantitative measurements of film thickness to be made.

Liquid films falling under the influence of gravity are widely encountered in a variety of industrial two-phase flow applications (distillation columns, nuclear reactor cores, etc.). In addition, the falling annular film represents a fundamental limiting case of the annular flow regime of two-phase gas-liquid flows. The literature on annular falling films is dominated by studies concerning the average film thickness. Information on more detailed characteristics of the film thickness variations and information on the velocity profile within the film and wall shear stress are much less common. The statistical description of the film thickness is complicated by the fact that practically all flows of interest occur in the turbulent regime. Due to the complex and unsteady nature of the turbulent annular falling film, no complete theories or models have yet been developed on the subject. Experimental studies are needed to gain insight into the basic mechanisms that govern this complex flow.<p>The primary purpose of this thesis research was to characterise the film thickness of falling annular films at high and very high Reynolds numbers using non-intrusive imaging techniques. Another objective was to develop ray-tracing techniques to reduce optical distortion and obtain high-quality experimental data. <p>Instantaneous film thickness measurements of falling annular films were extracted at five different Reynolds numbers in the range Re = 1000 ~ 6000 for the fully developed turbulent regime using an automated optical measurement technique. From visual observation of the images obtained it was found that waves were not axisymmetric, i.e., there was substantial azimuthal variation in film thickness. The turbulent waves appeared to be similar in appearance to very large breaking ocean waves driven by strong winds. The random nature of these falling annular films was subjected to statistical analysis.<p>Statistical characteristics of film thickness were studied at Reynolds numbers in the range Re = 1000 ~ 6000. A correlation for dimensionless mean film thickness was obtained in the turbulent flow regime. The dimensionless mean film thickness obtained here was found to be in reasonable agreement with the other established experimental and theoretical studies. It was shown that the Reynolds number influences the statistical characteristics of film thickness such as standard deviation and coefficient of variation. The additional data obtained here shows that the standard deviation continues to increase in proportion to the mean film thickness in the turbulent regime. In other words, in the lower turbulent zones the films are thin and less wavy, whereas in the higher turbulent zones the films are thicker and extremely wavy in nature.<p>The probability density distributions were also obtained. It was found that the measured probability density distributions were asymmetric. They all had a maximum peak and were skewed to the right hand side with a long tail that stretched to over six times the peak value. The maximum peak could be considered to represent the modal value of the film thickness or the substrate film thickness. The increase in skewness and the decrease in the height of the peak with liquid Reynolds number could be attributed to the presence of large disturbance waves which ride on the substrate film. This enhances the waviness of the film.<p>A common problem in imaging flows in cylindrical tubes is the optical distortion caused by the wall curvature. To minimize this problem the cylindrical tube was surrounded by an optical correction box with flat walls filled with water. In addition, an advanced ray tracing model was employed to reduce optical distortion effects in the cylindrical tube. This technique increased the accuracy of the imaging technique and enabled quantitative measurements of film thickness to be made.

Master of Arts / Department of English / Mohammad I. Rahman / This project is a novel-in-stories that revolves around the misadventures and exploits of Povi McDougal, head diversity consultant for G & K, responsible for the aggressive sensitivity training of new hires in the company's bid to avoid future lawsuits. She is a nervy, disenfranchised, high-functioning alcoholic. When you think Povi, think binaries: she's a big-hearted misanthrope. She is furious yet wistful, edgy yet vulnerable, knowing yet obtuse, gas yet electric, etc. The stories are all narrated by Povi and are voice, language and character-driven. As a series of connected stories, the action is not in service to one primary plotline. There is, however, a narrative drive that treats Povi's dawning realization of and efforts to come to grips with, her personal and ethnic identity, her abandonment issues and self-imposed isolation. Central to these stories is a synthetic folklore. As a child, Povi's father enrolled her in the Indian Princesses youth group at the YMCA in a misguided attempt to help her connect more fully with her Native American heritage. Figuring prominently in the girls' mythology was the tale of Falling Rock, the highly sought Indian princess who wanders into the woods to escape the fray of young braves who seek her hand in marriage. "Legend" has it Falling Rock becomes lost and is never heard from again. The group's participants are told to be on the lookout for her whenever they see a yellow road sign bearing her name. In short, Povi is my Princess Falling Rock. Given her sense of disinheritance, it seems fitting that her folklore is synthetic, invented. Basically, I've gotten her to wander off into the woods for a bit of solitude, and have kept her there for a while, as she tries to find her way back to her tribe – or some such suitable substitute for tribal affiliation, community, love, what have you.

No description available.

Introduction: A review of the literature shows that standard clinical balance measures do not adequately predict fall risk in community-dwelling older individuals. There is significant evidence demonstrating the interactions of fear, anxiety, and confidence with the control of standing posture. Little is known however about the nature of this relationship under more challenging balance conditions, particularly in the elderly. The primary purpose of this work was to evaluate the relationship between fear of falling, clinical balance measures and fall-risk. Methods: Three studies were conducted evaluating the effects of postural threat (manipulated by support surface elevation) and/or cognitive loading (working memory secondary task) on clinical balance performance and task-specific psychological measures. Predictive and construct validity as well as test-retest reliability was evaluated for measures used to assess fear of falling and related psychological constructs . Results: Postural threat resulted in reduced balance confidence and perceived stability as well as increased state anxiety and fear of falling. These changes were significantly correlated to decrements in performance of clinical balance tasks. Neither standard clinical scales of balance and mobility nor generalized psychological measures, alone or in combination, could predict falls in community-dwelling elderly. However, combined scores on selected challenging clinical balance tasks could significantly predict falls. Furthermore, improved predictive precision resulted from having these tasks performed under combined postural threat and cognitive loading. Finally, the inclusion of task-specific psychological measures resulted in further improvements to predictive precision. Psychological measures demonstrated fair to excellent test-retest reliability in both healthy young and independent-living older individuals. Conclusions: Clinical balance tasks performed under more challenging conditions likely better reflect everyday experiences in which a fall is likely to occur. Incorporating easy-to-administer task-specific psychological evaluations and self-reported health estimates with clinical balance assessments might improve the likelihood of correctly identifying community-dwelling individuals at risk for falls. Improved estimates of fall-risk may lead to a reduction in the number of falls experienced in this population, thereby reducing the significant burden of fall-related hospitalizations, treatments and rehabilitation on the individual, families and health care system.

Vi åldras på flera sätt, biologiskt, psykologiskt och socialt. Rädsla för att ramla, en pågående oro för att ramla och som leder till undvikande av aktiviteter man fortfarande kan göra, finns hos många äldre och påverkar dem på flera sätt. Rädslan kan leda till inaktivitet som i sin tur leder till ensamhet och nedstämdhet. Syftet med studien är att beskriva äldre personers egen erfarenhet av att uppleva rädsla för fall och dess konsekvenser. En kvalitativ studie har gjorts där fem personer har intervjuats. Intervjuerna och analysen av dem är gjorda utifrån en fenomenologisk metod. Vid analysen framkom tre huvudkategorier: Oro för konsekvenserna av ett fall, Strategier för att undvika fall samt Saknad. Äldre personer som upplever en rädsla för fall undviker vissa aktiviteter. De upplever också en saknad efter aktiviteter de tidigare utfört men nu slutat med. De har strategier för att hantera sina rädslor. Det är viktigt att inte se äldre som en homogen grupp och att vid rehabilitering ta hänsyn till olika faktorer som person, miljön personen vistas i, aktiviteter de utför eller önskar utföra och känslan av delaktighet. / We age in different ways, biologically, psychologically and socially. Fear of falling which means a lasting concern about falling which leads to an avoiding of activities that the person still has a capability to do. This can cause inactivity that eventually leads to loneliness and depression. The aim of this study is to describe older peoples own experiences to live with fear of falling and its consequences. A qualitative study was done where five older people were interviewed. The interviews and analyses were done using a phenomenological method. At the analysis three main categories were found: Concern about the consequences of a fall, Strategies to avoid a fall and A feeling of missing. Older people with fear of falling avoid some activities. There is a feeling that they miss some activities they have previously done but don't do any longer. They have strategies to handle their fears. In rehabilitation it is important not to see the elderly as an homogeneous group. It is also important to consider different factors such as the person, the environment in which the person lives, activity and feeling of involvement.

No description available.

The proportionality constant in Darcy's Law is called hydraulic conductivity (K), and it is the most fundamental parameter to groundwater studies. There are a number of in situ and laboratory techniques employed to determine K, one of which is falling head permeameter (FHP). In FHP, determining K involves two steps: measuring hydraulic head change over time and calculating the K value. In the past, calculating K was done using Darcy's Law, which states linear correlation between the flux and the hydraulic gradient, but this is only true when the inertial forces are negligible at small velocities. At higher velocities, flow becomes unsteady because of the change over time in flow magnitude and hydraulic gradient, which requires mass conservation law to be combined with Darcy’s Law and eventually leads to Laplace’s equation for an incompressible matrix. If the media is compressible, specific storativity should be taken into account, as well. In this study, we investigated the transiency of flow in FHP tests by analyzing the effect of specific storativity on K calculations. We have developed a new semi- analytical solution for transient flow in FHP in Laplace domain and used the de Hoog algorithm to attain the inverse Laplace transform of this solution to yield solutions in time domain. We have also provided some analysis and a comparison of steady-state solution along with using experimental data and the data from the literature to analyze the solution. Upon these, we concluded that the transient flow in falling-head tests has minimal effect in general, although using the transient solution provided may improve the accuracy without a major effect.

Introduction: A review of the literature shows that standard clinical balance measures do not adequately predict fall risk in community-dwelling older individuals. There is significant evidence demonstrating the interactions of fear, anxiety, and confidence with the control of standing posture. Little is known however about the nature of this relationship under more challenging balance conditions, particularly in the elderly. The primary purpose of this work was to evaluate the relationship between fear of falling, clinical balance measures and fall-risk. Methods: Three studies were conducted evaluating the effects of postural threat (manipulated by support surface elevation) and/or cognitive loading (working memory secondary task) on clinical balance performance and task-specific psychological measures. Predictive and construct validity as well as test-retest reliability was evaluated for measures used to assess fear of falling and related psychological constructs . Results: Postural threat resulted in reduced balance confidence and perceived stability as well as increased state anxiety and fear of falling. These changes were significantly correlated to decrements in performance of clinical balance tasks. Neither standard clinical scales of balance and mobility nor generalized psychological measures, alone or in combination, could predict falls in community-dwelling elderly. However, combined scores on selected challenging clinical balance tasks could significantly predict falls. Furthermore, improved predictive precision resulted from having these tasks performed under combined postural threat and cognitive loading. Finally, the inclusion of task-specific psychological measures resulted in further improvements to predictive precision. Psychological measures demonstrated fair to excellent test-retest reliability in both healthy young and independent-living older individuals. Conclusions: Clinical balance tasks performed under more challenging conditions likely better reflect everyday experiences in which a fall is likely to occur. Incorporating easy-to-administer task-specific psychological evaluations and self-reported health estimates with clinical balance assessments might improve the likelihood of correctly identifying community-dwelling individuals at risk for falls. Improved estimates of fall-risk may lead to a reduction in the number of falls experienced in this population, thereby reducing the significant burden of fall-related hospitalizations, treatments and rehabilitation on the individual, families and health care system.