We study the nonlinear Schrödinger (NLS) equation on star graphs with the Neumann- Kirchhoff (NK) boundary conditions at the vertex. We analyze the stability of standing wave solutions of the NLS equation by using different techniques. We consider a half-soliton state of the NLS equation, and by using normal forms, we prove it is nonlinearly unstable due to small perturbations that grow slowly in time. Moreover, under certain constraints on parameters of the generalized NK conditions, we show the existence of a family of shifted states, which are parametrized by a translational parameter. We obtain the spectral stability/instability result for shifted states by using the Sturm theory for counting the Morse indices of the shifted states. For the spectrally stable shifted states, we show that the momentum of the NLS equation is not conserved which results in the irreversible drift of the family of shifted states towards the vertex of the star graph. As a result, the spectrally stable shifted states are nonlinearly unstable. We also study the NLS equation on star graphs with a delta-interaction at the vertex. The presence of the interaction modifies the NK boundary conditions by adding an extra parameter. Depending on the value of the parameter, the NLS equation admits symmetric and asymmetric standing waves with either monotonic or non-monotonic structure on each edge. By using the Sturm theory approach, we prove the orbital instability of the standing waves. / Thesis / Doctor of Philosophy (PhD)

No description available.

Biofuels, a solar-sourced technology that can be processed from non-fossilized plant matter, have significant appeal as a means of securing a reliable, sustainable energy supply. They appear to offer significant potential by virtue of being harvestable from common plant life such as prairie grasses. I argue that a shared set of knowledge claims emerging from multiple energy/environmental institutions in Germany and the U.S. are linked by a shared set of assumptions. I characterize these claims as a "mainstream" discourse because together they function as a single powerful discourse that influences national policy and research priorities. In examining the potential material impacts of the discourse on regional and global habitats, I demonstrate the powerful performative capacity of the discourse. I also describe how this mainstream discourse perpetuates momentum along existing trajectories of at least three socio-technological regimes: agriculture, transport, energy. The practitioners (biofuels experts) of the discourse construct representations of the realities that form the basis of their research. I refer to these representations as maps because like a city map, they privilege some things while marginalizing others. These maps are then utilized as guides for intervening into the habitat in order to develop and implement biofuels. Implicated within the maps are practices that have the potential to reconstitute reality. For example, the mapping of a variety of plants as "energy crops" implicates practices generally associated with high-yield cash crops intended for trade on the global marketplace. The materialization of these practices will assimilate various plants, reconstituting them as bona fide energy crops, resulting in monocultured regional and global habitats. I develop my argument by describing how knowledge production is regulated by the implicit rules that govern the discourse. This regulatory apparatus insures that certain types of knowledge as well as methods for producing that knowledge are privileged over others. I introduce several concepts--"institutional platform, thought collective, biofuels practitioner--"as analytical tools to develop my argument and explain how the discourse functions. I demonstrate how perpetual recirculation of knowledge claims through publication, citation, conferences, workshops and task forces naturalizes these claims, giving them authoritative force. This force is evidenced in an increased performative capacity as well as a higher degree of discursive hegemony. I demonstrate the material effects of the discourse at the practical level of its deployment by introducing another analytical tool --ground truthing. Geographers and military reconnaissance personnel use ground truthing to describe the process of physically inspecting the lay of the land in order to determine the accuracy of the maps. With this tool, I demonstrate the potential of the discourse to reconstitute habitats and landscapes. Finally I propose changing the terms of mainstream energy discourse through practices intended to de-scientize and democratize the discourse through incorporating alternative expertises. This includes: a} moving away from corporate control of energy solutions by situating energy-systems decisions and ownership at the local community level, and b} improving the definition of systemic problems by transitioning away from knowledge production that privileges the detached "spectator" approach over the embodied, participatory approach. / Ph. D.

The purpose of this paper is to explore the nature and language of Anglo-American opposition to quartering from the start of the French and Indian War in 1756 to the Revolutionary War in 1776. This paper will also attempt to demonstrate the shifting focus of Anglo-American arguments against the quartering of troops over these two decades. Quartering of troops in private homes and defraying the cost of quartering were the prevalent concerns of Anglo-Americans during the French and Indian War. Then, the Quartering Act of 1765 significantly changed the perception of Anglo-Americans toward quartering of troops as a matter of illegal taxation. Lastly, the unfolding events in 1768 and onwards, in Boston, marked a turning point as the fear of a standing army in peace time redefined Anglo-American opposition to the quartering of redcoats. The significance of Anglo-American opposition to the Quartering Acts paled in comparison to other colonial grievances that stemmed from taxation issues, but it was important enough to finds its place in the Declaration of the Independence and in the Third Amendment of the federal constitution. / Master of Arts

This thesis addresses two important issues when operating the novel three legged mobile robot STriDER (Self-excited Tripedal Dynamic Experimental Robot); how to stand up after falling down while minimizing the motor torques at the joints and considerations for gait planning. STriDER uses a unique tripedal gait to walk with high energy efficiency and has the ability to change directions. In the first version of STriDER, the concept of passive dynamic locomotion was emphasized; however, for the new version, all joints are actively controlled for robustness. The robot is inherently stable when all three feet are on the ground due to its tripod stance, but it can still fall down if it trips while taking a step or if unexpected external forces act on it. The unique structure of STriDER makes the simple task of standing up challenging for a number of reasons; the high height of the robot and long limbs require high torque at the actuators due to its large moment arms; the joint configuration and length of the limbs limit the workspace where the feet can be placed on the ground for support; the compact design of the joints allows limited joint actuation motor output torque; three limbs do not allow extra support and stability in the process of standing up. This creates a unique problem and requires novel strategies to make STriDER stand up. This thesis examines five standing up strategies unique to STriDER: three feet pushup, two feet pushup, one foot pushup, spiral pushup, and feet slipping pushup. Each strategy was analyzed and evaluated considering constraints such as static stability, friction at the feet, kinematic configuration and joint motor torque limits to determine optimal design and operation parameters. Using the findings from the analysis, experiments were conducted for all five standing up strategies to determine the most efficient standing up strategy for a given prototype using the same design and operation parameters for each method. Also, a literature review was conducted for human standing from a chair and human pushup exercises and the conclusions were compared to the analysis presented in this thesis. Many factors contribute to the development of STriDER's gait. Several considerations for gait planning as the robot takes a step are investigated, including: stability, dynamics, the body's maximum and minimum allowable heights, the swing legs foot clearance to the ground, and the range of the subsequent swing foot contact positions. A static stability margin was also developed to asses the stability of STriDER. This work will lay the foundation for future gait generation research for STriDER. Additionally, guidelines for future work on single step gait generation based on kinematics and dynamics are discussed. The findings presented will advance the capabilities and adaptability of the novel robot STriDER. By studying standing up strategies and gait planning issues, the most efficient control methods can be implement for standing up and preparing to take a step and lay out the foundations for future research and development on STriDER. / Master of Science

Of all children in the US born with Cerebral Palsy (CP), 30-40% of them will be diagnosed with Hemiplegic CP (HCP), presenting with one side of the body weaker than the other. The resulting asymmetries impede the ability of children with HCP to distribute weight evenly between their lower limbs. This often contributes to poor postural control and 'favoring' of their uninvolved side for stability during balance and gait. Much is still unknown about the biomechanical characteristics of asymmetry in the lower limbs. There are a few previous research studies completed in biomechanics labs that highlight some gaps in knowledge regarding our understanding of posture and balance in this population of children, but the availability of clinical assessments that help inform the implementation and impact of treatment targets for posture and balance are sparse. This dissertation showcases two independent studies aimed at some of the gaps in knowledge for posture and balance in children with HCP. The first study in this dissertation presents and tests the reliability when a clinical measure, the Posture and Postural Ability Scale (PPAS) was modified for use in children with HCP going through a therapeutic process. The PPAS was originally developed and tested with adults in controlled settings, often with individuals being placed in postures for examination. For the study presented here, modifications focused on scoring postures when children with HCP naturally assumed various sitting and standing postures during treatment. Researchers and an experienced therapist video-coded the modified PPAS. Intrarater and interrater reliability was calculated via Cohen's kappa, percent agreement and Intraclass Correlation Coefficients. Although reliability amongst and between researchers were weak (kappas < 0.7), videos were successfully scored, demonstrating the tool is feasible. In addition, some high levels of intrarater reliability was obtained by a more experienced clinician. Suggestive that this modified PPAS could serve as a potential tool for qualified clinicians to collect meaningful posture and postural control data. The second study addressed a specific gap in knowledge about the characteristics of gait anticipation (GA, i.e., expectation of initiating a step) in children with HCP on balance. Balance and limb symmetry metrics were compared during standing in three children with HCP and typically developing (TD) peers that were matched by age and sex, alongside a third (independent) sample of 12 unmatched TD children. Motion capture analysis and force plate technology were utilized to record and follow how center of pressure (COP) and center of mass (COM) move during quiet standing (without anticipating gait) and standing with GA. This study applied a Symmetry Index (SI) to COP displacement and COP velocity allowing for quantification of asymmetries between the lower limbs during standing with and without the anticipation of gait. Children completed multiple standing trials where they were ask to stand for 35 seconds (5 seconds to obtain balance and 30 seconds of data collection). Standing trials, involved sets where children were instructed that they would not walk forward and GA trials where they were asked to stand knowing that a light would indicate they should walk forward. The light also indicated which limb (i.e. right or left) the child should step forward with first. Limb designation for stepping forward was randomly generated. Data was examined across and within (15 second blocks) 30 seconds of standing. We had the following hypotheses: 1) GA would increase COP displacement and COP velocity for children with HCP greater than TD peers who would have no change; 2) children with HCP would have different levels of symmetry between the lower limbs when expecting to walk than TD peers; and 3) children with HCP would have different reaction times based on the limb (i.e., involved versus uninvolved) they were asked to start walking with. The HCP group showed the largest increase in COP displacement when comparing standing with no expectation of walking where they had an average of 22.0 ± 10.0 mm over 30 seconds of standing to an average of 24.5 ±9.90mm during GA. The matched group average was 11.3 ±8.87mm with no expectation of walking and 4.6 ±12.6mm with GA. The TD group's COP displacement remained relatively similar with an average of 8.04 ±6.40mm during when not expecting to walk and an average of 8.29 ±6.70mm with GA. Similar increases were seen for COP velocity. Comparisons for symmetry between limbs showed that COP was displaced more underneath the uninvolved side (first 15s was 79.52%) for children with HCP, and that COP displacement asymmetry switched to become larger underneath the involved side over time (the latter 15s was -82.81%) when there was no expectation for walking. This was inverted during GA, where children with HCP initially had more COP displacement on the involved side (-72.68%) and transitioned to higher levels on the uninvolved side (99.66%) as they prepared for gait initiation. Children with HCP took 0.2 seconds longer to initiate gait with their uninvolved (not preferred) side and also took twice as long to initiate gait overall in comparison to TD peers. Our data suggests that our listed hypotheses may be correct. However, this study has limitations to sample size, demographics and biomechanical metrics. Future studies should replicate these findings and include larger, more diverse samples with further metrics such as load. If findings are confirmed, this data suggests that therapies should consider that children with HCP might change postural strategies during standing when they are anticipating walking forward in comparison to simply standing in place. This dissertation seeks to set a foundation for collaborations between biomechanists and therapists alike, potentially highlighting novel opportunities to develop more innovative treatment options for children with HCP. / Doctor of Philosophy / Children with hemiplegic cerebral palsy (HCP) show limitations in coordination and activation of muscles on one side of their body; additionally, clinicians report an asymmetrical distribution of weight in their legs during standing and walking based on observation. This lower limb asymmetry is often paired with poor coordination and is believed to negatively impact posture and balance. Children with HCP often have difficulty starting and stopping walking, altered balance during sitting and standing, and challenges completing everyday activities such as navigating around or across obstacles and climbing up steps. I have worked together with my committee members to complete two independent projects measuring posture and postural control. The first project is a reliability study where researchers tested the utility of a modified measurement tool that could be used to score postures and postural control of children assuming natural postures during therapy sessions. The modified tool was based on a previously developed tool called the Posture and Postural Ability Scale (PPAS). The study had multiple researchers and a therapist score previously recorded treatment videos. Outcomes suggest that our modified PPAS could be used to score postures from video recordings of therapy session, but that increased modifications in the tool and scoring protocol are needed to improve the reliability of the tool. The second project funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development involved children with HCP and typically developing (TD) peers. The goal of the project was to understand if children with HCP change characteristics of standing when they know they will begin to walk. We also wanted to better understand issues surrounding how symmetrical (or not) children with HCP were with the use of both their involved and uninvolved legs. We found that children with HCP do alter characteristics of standing when they anticipate walking much more that TD peers. We also found asymmetries between the two limbs during standing that differed based on children with HCP's anticipation of walking.

Yes / Thermoacoustic refrigeration is an evolving cooling technology in which the acoustic power is used to pump heat. The operating conditions and geometric parameters are important for the thermoacoustic refrigerator performance, as they affect both its performance and the temperature difference across the stack. This paper investigates the effect of the stack geometric parameters and operating conditions on the performance of a standing wave thermoacoustic refrigerator and the temperature difference across the stack. DeltaEC software is used to make the thermoacoustic refrigerator model. From the obtained results, normalised values for the operating conditions andgeometric parameters are collected to compromise both the performance and the temperature difference across the stack.

Yes / Pelvic radiography is used for the identification of hip joint changes, including pathologies such as osteoarthritis. Several studies have recommended that the position for this radiological procedure should be standing, not supine, to reflect the functional appearances of the hip joint. The aim of this review was to evaluate pelvis radiography positioning with respect to the image appearances and information provided for clinical decision-making. Aside from this, potential recommendations to the radiographic technique for an erect pelvis projection will be considered. Method: A literature search was performed using databases/ systems (ScienceDirect, Web of Science, PubMed, and MEDLINE). Only articles written in English were included. Results: Twenty-five articles were identified. Findings from the review describe the effect of repositioning from supine to erect on a series of specific hip measurements. These include pelvic tilt, joint space width, and the acetabular component. Conclusion: Evidence within the literature illustrates that in several studies, there were differences when repositioning from supine to standing for a number of pelvic metrics. Standing positioning is promoted by some authors since this may facilitate the early diagnosis of hip joint pathology and assist in the planning of surgical interventions. Literature is very limited on how to optimally perform erect pelvis radiography, and this should be an area for future research.

Den prekära konsthantverkaren Prekariatet, en framväxande ny klass som utmejslar konturerna av en social grupp. Här sammanförs individer under samma paraply, trots att de har helt olika utbildningar, eller ingen utbildning alls eller liknande sociala och ekonomiska förhållanden, så delar de samma politiska verklighet. De som befinner sig i tillvaron upplever att den är provisorisk och de lider av kronisk otrygghet. Ordet “prekär” betyder “mycket bekymmersam”. Den nya samhällsklass som kallas “prekariatet” har det just bekymmersamt. Syftet med mitt projekt är att använda material, en arbetsplatskultur och processer inom bemanningsbranschen och integrera dem med min konsthantverksprocess för att skapa en visuell berättelse om en klassposition. / Den prekära konsthantverkaren The precariat, a new class that outlines the features of a social group. In it, individuals are lumped together who, despite having completely different educations, or no education at all, and varying social and financial conditions, share the same political reality. The people in this situation perceive it as temporary and suffer from chronic insecurity. The word “precarious” means “very troubling” and the new social class that is known as the “precariat” are indeed troubled. The aim of my project is to use materials, a workplace culture and processes in the temp agency industry, and to integrate these into my craft process to create a visual story of a class position. / <p>Opponent: Päivi Ernkvist</p>

An alternative indirect integration regime of porous low-k materials was investigated. Based on a single Damascene structure the intra level dielectric SiO2 or damaged ULK was removed by using HF:H2O solutions to create free standing metal lines. The free spaces between the metal lines were refilled with a spin-on process of a low-k material. The persistence of barrier materials and copper against HF solutions, the gap fill behavior of the used spin on glass on different structure sizes and the main challenges which have to solve in the future are shown in this study.