Dissertations / Theses on the topic 'Strategies of stability'
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Musaazi, M. K. "Generator transient stability improvement by optimal aim strategies." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37795.
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Del, Pozo-Insfran David. "Emerging technologies and strategies to enhance anthocyanin stability." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013606.
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Roddy, Jackie Ann. "Retention Strategies for Financial Stability in Community Colleges." ScholarWorks, 2016. https://scholarworks.waldenu.edu/dissertations/2687.
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Tennessee education leaders must improve their student retention strategies to increase financial stability and enhance the state's ability to support businesses and jobs through a well-educated workforce. The focus of this qualitative multiple case study was on 6 Tennessee community colleges where leaders had demonstrated successful strategies for retaining students resulting in increased revenues and financial stability. The advocacy/ participatory worldview provided a conceptual framework for identifying and comparing themes regarding Tennessee higher education leaders' retention strategies. Data collection included interviews and review of organizational retention reports on strategies as well as college, state, and federal findings on retention. Federal government websites contained information about Tennessee community colleges having the highest retention rates. Methodological triangulation provided the opportunity to identify similarities in retention strategies used by the community college leaders. Using the concept of classical data analysis, responses were categorized according to the program, activity, or initiative college administrators used to increase retention. Based on mind mapping of the clusters of information, findings revealed 3 primary themes: effects of retention on college revenues; challenges in retaining at-risk students; and strategies for retaining students, including new student orientation, counseling and advising, tutoring, and freshman seminars. The potential for social change includes the opportunity to increasing the college-educated workforce to provide more opportunities for local business leaders and find viable applicants to fill open positions and enhance the economic sustainability of local communities.
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Keppler, Melanie Dawn. "Strategies for increasing the stability of triple helical DNA." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302353.
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Gil, Alvaro E. "Stability analysis of network-based cooperative resource allocation strategies." Columbus, OH : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1067538505.
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Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xiii, 97 p.: ill. (some col.). Includes abstract and vita. Advisor: Kevin M. Passino, Dept. of Electrical Engineering. Includes bibliographical references (p. 94-97).
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Zhang, Lin. "Control strategies and stability analysis of small-scale unmanned helicopters." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/control-strategies-and-stability-analysisof-smallscale-unmanned-helicopters(8e4f8464-6fdd-42e2-9362-033a57a128b2).html.
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This thesis presents the design and the stability analysis of a hierarchical controller for unmanned aerial vehicles. We utilize non-linear control methodology to command dynamics of unmanned helicopter which has been divided into slower translational dynamics (outer-loop) and faster orientation dynamics (inner-loop), thus exhibiting hierarchical structure. The attitude angles and position which separately belongs to the inner-loop and the outer-loop can be independently controlled by backstepping control strategy. Stability analysis of the helicopter system including applying dynamics has been illustrated after designing. And relative comparison between linear and nonlinear controllers has been carried out. After studying linear control, nonlinear control and stability analysis of one small-scale helicopter, we think about control strategy of a group helicopter which can be called as consensus control.
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Crawford, Calvin Stacey. "Partnership strategies for financial stability in the non-profit sector." online access from Digital Dissertation Consortium, 2006. http://libweb.cityu.edu.hk/cgi-bin/er/db/ddcdiss.pl?MR23654.
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Meegahapola, Lasantha. "Stability analysis and coordinated control strategies during high wind penetration." Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534620.
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Robinson, Jermell T. "African American Small Business Strategies for Financial Stability and Profitability." ScholarWorks, 2017. https://scholarworks.waldenu.edu/dissertations/4324.
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Despite the high failure rate of African American small businesses in the United States, only 2% of the U.S. Small Business Administration loans in 2016 were awarded to African American business owners. Most small business owners cite lack of access to financial resources as an influential factor that leads to business failure. Grounded in resource-based view theory, the purpose of this multiple case study was to identify strategies African American small business owners in Los Angeles County, California use to obtain financial resources to achieve sustainability for at least 5 years. Data were collected from in-depth interviews with 4 purposively selected African American small business owners and supplemented with a review of internal reports and original business plans that outlined their financing strategy. The data analysis process entailed Yin's 5-step analysis to guide the coding of participants' responses to identify keywords, phrases, and concepts to develop theme clusters. Through thematic analysis, 4 themes emerged to include: financial resources improved business success and stability, internal financing, business mentors and networking to secure financial stability, and overcoming nonfinancial challenges. All participants noted access to financial resources as the most important resource needed for their business to succeed, particularly in the initial phase of launching their businesses. The implications for social change include the potential to enhance African American small business profitability and growth leading to new employment opportunities, improved community amenities, and business mentor programs with youth, which can encourage wealth for the surrounding community of Los Angeles County and local government.
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Greenwell, Brian. "Business Strategies to Increase the Financial Stability of Private Universities." ScholarWorks, 2017. https://scholarworks.waldenu.edu/dissertations/3774.
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University administrators of nonprofit higher education private institutions face challenges to maintain financial stability as the projected tuition revenue is expected to decline over the next 15 years. In addition, projected closure or mergers for all colleges and universities is expected to reach 50% by 2030. The purpose of this single case study was to explore the strategies higher education private institution administrators use to manage financial stability. Kaufman's complexity theory was the conceptual framework for this study. Purposeful sampling was used to select 4 university administrators from an Ohio higher education private institution for face-to-face interviews. Semistructured questions provided the basis for data collection to identify the strategies these administrators used to manage financial stability. Additional sources of data included strategic plans, financial responsibility scores, and operational budget reports. Through thematic analysis, 4 themes emerged: budgetary controls, a shift in marketing strategy, creating value, and competitive environment. Implications of social change includes the potential to provide possible business strategies to Ohio area higher education private institution administrators for the development and sustainability of financial stability, which could lead to improving the economic conditions for the local community.
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Sande, Franciscus Martinus van der. "Strategies for improving hemodynamic stability during hemodialysis clinical and pathophysiological studies /." [Maastricht : Maastricht : Universiteit Maastricht] ; University Library, Maastricht University [Host], 1999. http://arno.unimaas.nl/show.cgi?fid=6882.
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Collins, Jennifer. "Polymer synthesis and conjugation strategies for enhancing the stability of oxytocin." Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/88594/.
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The aim of this work was to investigate different methods for the covalent attachment of poly(ethylene glycol) onto the therapeutic peptide oxytocin, a highly important, but thermally unstable therapeutic used globally. This peptide is the WHO recommended therapeutic for prevention of postpartum haemorrhaging, sitting on the WHO list of essential medicines. Tackling the currently unacceptable maternal mortality rate, particularly in developing countries is of paramount importance and is currently one of the WHOs main priorities. Within this project it was speculated that by attachment of PEG to the peptide there would hopefully be an increase in stability, particularly for aqueous formulations at elevated temperatures. Chapter one gives a brief outline of the problem that the world is facing with respect to maternal mortality, and particularly the gap between developed and developing countries and previous strategies that have looked into improving the stability of oxytocin. Additionally the various different site-specific conjugation approaches available for peptide modification are discussed, alongside how these can be implemented with controlled radical polymerisation techniques for the synthesis of alternative polymer architectures. Chapter two discusses two particular targeting chemistries for site-selectively targeting the N-terminal amine (the only amino group on the peptide structure). Some commercially applicable linear PEGylation reagents (such as utilising NHS esters) were utilised for the conjugation of polymers onto oxytocin in this manner. PolyPEGs were synthesised to contain similar α-end group functionality as for the linear polymers and reacted with oxytocin in similar manners. The reversible nature of one of these chemistries was also investigated, and the potential release of the native peptide dependence on conjugate architecture and pH were evaluated. In Chapter 3 the potential for conjugation techniques targeting the sulfhydryl groups arising from a reduction of the disulfide bond were approached in two different manners. Disubstituted maleimide chemistry is particularly useful in this case as it allows the rebridging of the disulfide bond, one of the main degradation sites on the peptide, with a stronger 2-carbon bond. Dithiophenolmaleimide α-end functional polyPEGs were synthesised and conjugated onto the peptide via an in-situ approach alongside traditional conjugations with both polyPEGs and linear PEGs. Another approach was evaluated for the conjugation at the disulfide bond that treats both free cysteine residues for separate conjugations utilising phosphine mediated thiol-ene chemistry. The facile synthesis of ABA block copolymers containing a central ‘oxytocin’ block, however results in a loss of the cyclic structure on the peptide, and likely complete suppression of biological activity. Chapter 4 reports the investigation of the various conjugation strategies raised in chapters 2 & 3 for how the properties of the peptide might have changed post-conjugation comparing linear PEG and polyPEG site selectively added at either position in comparison to the native peptide. This is evaluated for the thermal stability, where oxytocin shows high levels of degradation in aqueous solutions, particularly at elevated temperatures. Also investigated is the potential retention of uterotonic activity, via ex-vivo electrophysiology studies, as well as some previously investigated effects on the inhibition of cell proliferation of the breast cancer cell line MDA-MB231. Chapter 5 focusses on the conjugation to oxytocin, and another small disulfide containing peptide of some different (non-PEG) polymers synthesised in similar manners to those discussed in chapters 2 and 3. These few examples show that there is a large scope within this polymer synthesis and conjugation chemistry for utilising these techniques for a wide range of different monomer classes. Those described include the synthesis of a promising PEG alternative, two different thermoresponsive polymers and polymers containing pendant sugar functionality followed by the subsequent peptide conjugations.
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Ismael, Alexander. "Comparison of fast frequency reserve strategies for Nordic grid frequency stability." Thesis, Uppsala universitet, Institutionen för elektroteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-411503.
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How long would modern society cope with a power outage, what would happen to vital systems that we today take for granted in modern society. The Nordic electricity grid is facing a major shift where electricity production from non-renewable sources are to be replaced increasingly by renewable sources. By increasing the penetration of wind and solar power the electric power system might be exposed to disturbances due to decreasing inertia as a result of the electricity transition. Currently the electric power system has different reserves to use to maintain frequency stability but there are other reserves that could help further in the fight for the balance between electricity production and consumption. This project examines whether the new reserve service, fast frequency reserve (FFR), can help the existing frequency containment reserve for disturbed (FCR-D) operation. Therefore, two experiments were conducted using the simulation tool ARISTO, addressing relevant issues involving frequency stability. Motivation for the hypothesis was to investigate if FFR could reduce the frequency transients and improve frequency variations by developing various setups and cases when inertia was retained and when the system inertia was reduced at different stages. The results of the experiments showed that the global minimum frequency, nadir, had increased for all test cases compared to the reference case when using FFR, this proved that the FFR in fact help reducing frequency transients. The results showed furthermore that when the FFR had a duration time of 30 seconds compared to only 5 seconds, the frequency variations could be improved for certain setups for experiment 2.
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Colemon, Jerel Lynnette. "Strategies Nonprofit Leaders Use to Achieve Financial Stability Through Sustainable Funding." ScholarWorks, 2019. https://scholarworks.waldenu.edu/dissertations/7219.
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Leaders of nonprofit organizations fail to achieve financial stability to meet their mission and vision without sustainable funding. The achievement of fiscal sustainability is the most pressing challenge facing the nonprofit sector. Through the lens of the balanced scorecard model, the purpose of this multiple case study was to explore strategies that nonprofit organization executive leaders used to secure sustainable funding for financial stability. Data were collected from semistructured interviews with 5 executive directors of nonprofit organizations in Ohio and a review of their organizational documents relevant to sustainable funding. Data were analyzed using Yin's 5-step process for analysis. The 3 emergent themes resulting from data analysis were a sustainable programming strategy, a relationship collaboration strategy, and a donor commitment strategy. The findings of the study indicated that leaders of nonprofit organizations secure sustainable funding for financial stability through effective programming to fulfill their mission, developing collaborative relationships with internal and external stakeholders, and improving donor commitment to receive funding through reoccurring donations and endowment sources. Leaders of nonprofit organizations could use the findings of this study to provide comprehensive services that result in improved living and economic conditions in the communities they serve through implementing strategies for sustainable funding to meet the mission of their organizations.
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Burgos, Mellado Claudio Danilo. "Control strategies for improving power quality and PLL stability evaluation in microgrids." Tesis, Universidad de Chile, 2019. http://repositorio.uchile.cl/handle/2250/170135.
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Tesis para optar al grado de Doctor en Ingeniería Eléctrica en cotutela con la Universidad de Nottingham, U.K.En los últimos años, el interés por la protección del medio ambiente y la sostenibilidad energética ha aumentado de manera constante; este hecho ha promovido actividades de investigación y proyectos centrados en fuentes de energía renovable no convencional (ERNC) como reemplazo de los combustibles fósiles. En este contexto, las tecnologías basadas en ERNC ofrecen una solución para integrar recursos energéticos distribuidos donde se ha introducido el concepto Microred (MR) para facilitar la integración de un gran número de microgeneradores, unidades de almacenamiento de energía y cargas. Esta integración se logra utilizando convertidores basados en electrónica de potencia, y por lo tanto, hay un aumento en estos dispositivos en los sistemas modernos de energía eléctrica. La proliferación de convertidores de potencia afectará inevitablemente tanto la calidad de la energía como la estabilidad de los sistemas eléctricos que tienen interfaces basadas en estos dispositivos. En este contexto, dos cuestiones clave que deben abordarse son las siguientes: (i) los desequilibrios y armónicos inherentemente presentes en la MR debido a la naturaleza aleatoria de las cargas y (ii) dado que las microredes son sistemas débiles, la estabilidad entre el convertidor de potencia y el punto de acoplamiento común (PCC). Estas dos cuestiones críticas en microredes se estudian en esta tesis. El primero se analiza considerando sistemas de 4 hilos mientras que el último se estudia considerando un sistema balanceado de 3 hilos. Para gestionar los problemas de desequilibrio y armónicos en microredes de 4 hilos, se proponen dos enfoques. Primero, se propone una metodología novedosa basada en la aplicación de un filtro de potencia activa (APF, por sus siglas en inglés) de 4 hilos. El control del compensador se basa en la Teoría de la Potencia Conservativa (CPT). En el segundo enfoque, se propone un esquema de control cooperativo basado en la CPT para compartir desequilibrios y armónicos en sistemas trifásicos de cuatro hilos controlados mediante control droop. El comportamiento de los dos esquemas de control propuestos se demuestra mediante el uso de prototipos y utilizando las condiciones de operacion una microred real ubicada en Canadá. Para estudiar cómo la naturaleza débil de las MG afecta la estabilidad de la interfaz entre un convertidor y el PCC, se ha realizado un análisis de estabilidad centrado en el bucle de bloqueo de fase (PLL, por sus siglas en inglés), basado en una modelacion del sistema en coordenadas dq. El sistema estudiado corresponde a un convertidor de 3 hilos conectado a una red débil trifásica equilibrada. El rendimiento de este método se valida mediante la simulación con el software Plexim PLECS y se realiza una validación experimental.
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Phelps, Ronningen Kelsey. "Effects of alternative feeding strategies for feedlot cattle on meat quality." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/35498.
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Doctor of PhilosophyDepartment of Animal Sciences and Industry
John M. Gonzalez
American beef producers use a multitude of production regimens, with new products constantly becoming available to producers that could ultimately produce beef that fits niche markets. Additionally, U.S. producers employ the use of two exogenous growth promotants (ExGP), anabolic implants and β-adrenergic agonists, to maximize production efficiency. This body of work examined effects of different production strategies on beef quality. In the first study, steers were fed a conventional diet or a diet containing two supplements of the Programmed Nutrition Beef Program (PN) and each diet was fed with or without ExGP. There were no adverse effects on color, but use of ExGP negatively impacted tenderness of steaks. However, the inclusion of the PN supplements decreased purge loss of loins during aging and decreased cook loss of beef steaks. The decrease in purge and cook loss may be intriguing for retailer who purchase-in and cook products as they could specify a demand for beef from animals in this program to potentially save on product losses. Researchers have examined strategies to increase omega-3 fatty acids within beef, as omega-3 fatty acids are health beneficial. The second study examined impacts of feeding increasing levels of a docosahexaenoic acid (DHA)-rich microalgae to heifers on fatty acid profiles, color stability, and palatability of the LM and color and . Feeding increasing levels of microalgae meal quadratically increased total omega-3 PUFA, with increases in DHA content up to 850% and eicosapentaenoic acid (EPA) up to 340% at the greatest feeding level. Although feeding microalgae changed fatty acid profiles to be more health beneficial, color and flavor were adversely affected. At the end of display, steaks from heifers fed the greatest amount of microalgae had reduced a* (redness) values and increases in surface metmyoglobin (discoloration) formation. Panelists detected more off-flavors as the level of microalgae meal increased in the diet. Poor color stability and increases in off-flavors were due to increased oxidation products in these steaks, but problems could be mitigated by inclusion of antioxidants in the diet. The third study presented examined effects of feeding antioxidants to steers fed microalgae meal on color and palatability of Longissimus lumborum steaks. Steers were fed vitamin E at a level over their nutritional need and a selenium-yeast product in addition to feeding microalgae. Again, feeding microalgae without antioxidants in the diet negatively impacted color during display, but feeding antioxidants significantly improved the color stability. There were no off-flavor differences between steaks from steers fed the diet containing only microalgae and diet containing microalgae with antioxidants. Increasing the antioxidant content of the finishing diet when microalgae was fed is feasible way to increase the color stability of steaks and decrease off-flavors of Longissimus lumborum steaks.
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Alemán, Mercedes. "Strategies to improve the oxidative stability of bakery products fortified with heme iron." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/283545.
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Iron deficiency is the most prevalent nutritional issue worldwide. The fortification of food products could help covering the iron requirements, mainly in certain population groups where prevalence of iron deficiency anaemia is high because its amount in the diet is poor and/or presents low bioavailability. In this regard it is worth to mention that the population groups with higher prevalence of iron deficiency are both women at childbearing age and children.
However, iron fortification should take into account several variables that determine its effectiveness being the bioavailability of the iron form used and its interaction with the matrix the most crucial ones.
The aim of this thesis is to obtain a fortified food product with a high bioavailable iron while being accepted by consumers and stable towards oxidation. In this regard, a sandwich-type cookie filled with a chocolate cream has been selected as example of heme iron fortification in bakery products. The presence of chocolate, apart from making the food product to be more appealing to children, may help disguise the intense colour of the heme iron ingredient, which is intended to be used for its high bioavailability.
Since palm oil is widely used in the manufacture of biscuits, cakes and pastries, it is planned to previously study those strategies that minimize oxidation in a model based on palm oil fortified with heme iron before these are employed in the final food products. By means of this model, we assessed the efficacy of the following strategies: the addition of antioxidants; the heme iron ingredient encapsulation and the combination of both strategies. The strategies that were shown to be efficient in this fortified palm oil model were further assessed on sandwich-type chocolate cookies fortified with heme iron. In these cookies and over a period of one year of storage in the dark at room temperature, the oxidative stability and consumers’ overall acceptability has been studied
By combining the two strategies, the addition of an antioxidant (ascorbyl palmitate) and the encapsulation of heme iron by co-spray-drying it with calcium caseinate, the cookies were oxidative stable and accepted by consumers over one year of storage at room temperature in the dark.La deficiencia en hierro es la deficiencia nutricional con más prevalencia a nivel mundial. El fortalecimiento de productos alimenticios con hierro puede contribuir a cubrir las necesidades diarias de este elemento, sobre todo en determinadas poblaciones donde la prevalencia de esta deficiencia es elevada debido a que su cantidad en las dietas es pobre y/o presenta una baja biodisponibilidad. Cabe destacar que los grupos con mayor prevalencia de deficiencia en hierro son las mujeres en edad fértil y niños. Sin embargo, el fortalecimientos de alimentos con hierro debe tener en cuenta diversas variables que condicionan su efectividad, siendo la biodisponibilidad del hierro y su interacción con la matriz alimentaria las más cruciales. El objetivo que se plantea en esta tesis es conseguir un producto rico en hierro altamente biodisponible que presente una buena aceptabilidad y estabilidad oxidativa. Dentro de los productos de galletería/ bollería, se escoge una galleta rellena de chocolate como ejemplo de fortalecimiento en hierro hémico por su difusión y simplicidad. El chocolate, aparte de hacer el producto más apetecible a la población infantil y juvenil, permite enmascarar el color del ingrediente de hierro hémico que se pretende utilizar por su elevada biodisponibilidad. Dado que la manteca de palma es ampliamente utilizada en la elaboración de productos de galletería y bollería, se plantea, previamente, estudiar aquellas estrategias que permitan minimizar la oxidación en un modelo basado en manteca de palma fortalecida con hierro hémico. Mediante este modelo se han contemplado las siguientes estrategias: la eficacia de la adición de antioxidantes, la encapsulación del ingrediente de hierro hémico y la combinación de ambas. Las estrategias que resultaron ser más eficaces en este modelo fueron posteriormente estudiadas en galletas tipo sándwich rellenas de chocolate fortalecidas con hierro hémico. En el producto desarrollado a lo largo de un año de almacenamiento en la oscuridad a temperatura ambiente, se ha estudiado su estabilidad oxidativa y su grado de aceptación por parte de los consumidores. Gracias a la combinación de ambas estrategias, la adición de un antioxidante (palmitato de ascorbilo) y la encapsulación del hierro hémico por co-atomización de éste con caseinato de calcio, se ha obtenido un producto de galletería fortalecido con hierro altamente biodisponible estable frente a la oxidación y que a su vez ha sido aceptado por los consumidores a lo largo de un año de almacenamiento.
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Gade, Prasad V. N. "Performance Enhancement and Stability Robustness of Wing/Store Flutter Suppression System." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30339.
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In recent years, combat aircraft with external stores have
experienced a decrease in their mission capabilities due to
lack of robustness of the current passive wing/store flutter
suppression system to both structured as well as unstructured
uncertainties. The research program proposed here is to
investigate the feasibility of using a piezoceramic wafer
actuator for active control of store flutter with the goal
of producing a robust feedback system that demonstrates
increased performance as well as robustness to modeling
errors. This approach treats the actuator as an active
soft-decoupling tie between the wing and store, thus isolating
the wing from store pitch inertia effects. Advanced control
techniques are used to assess the nominal performance and
robustness of wing/store system to flutter critical
uncertainties.
NOTE: (10/2009) An updated copy of this ETD was added after there were patron reports of problems with the file.Ph. D.
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Wanner, Bertil. "Strategies for Reducing Vibrations during Milling of Thin-walled Components." Licentiate thesis, KTH, Maskin- och processteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-107156.
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Factors such as environmental requirements and fuel efficiency have pushed aerospace industry to develop reduced-weight engine designs and thereby light-weight and thin-walled components. As component wall thickness gets thinner and the mechanical structures weaker, the structure becomes more sensitive for vibrations during milling operations. Demands on cost efficiency increase and new ways of improving milling operations must follow. Historically, there have been two “schools” explaining vibrations in milling. One states that the entry angle in which the cutting insert hits the work piece is of greater importance than the exit angle. The other states that the way the cutter leaves the work piece is of greater importance than the cutter entry. In an effort to shed some light over this issue, a substantial amount of experiments were conducted. Evaluations were carried out using different tools, different tool-to-workpiece offset positions, and varying workpiece wall overhang. The resultant force, the force components, and system vibrations have been analyzed. The first part of this work shows the differences in force behavior for three tool-to-workpiece geometries while varying the wall overhang of the workpiece. The second part studies the force behavior during the exit phase for five different tool-to-workpiece offset positions while the overhang is held constant. The workpiece alloy throughout this work is Inconel 718. As a result of the project a spread sheet milling stability prediction model is developed and presented. It is based on available research in chatter theory and predicts the stability for a given set of variable input parameters.QC 20121206
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Cheng, Chinyuan. "Engineering strategies to optimize plasmid stability and protein production in recombinant Saccharomyces cerevisiae fermentation /." The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487779914824623.
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Seif, El-Nasr Sherif Abdel Rahman. "Strategies of stability : U.S. interventions in the Middle East (1953-2008) : a social complexity approach." Thesis, University of Liverpool, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.569439.
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Middle East stability has been a key element of United States foreign policy since the end of World War II. The American national interest has generally been held to be at stake in three areas: securing the continuous flow of oil and gas to the West, facilitating the movement of U.S. naval and commercial traffic from the Mediterranean to the Indian Ocean via the Suez Canal, and (until 1991) containing Soviet influence in the region. All these interests necessitated a concern with overall stability in the region. However, US stability-driven policies towards the region (1953:2008) have achieved little success. American decision-makers irreversibly affected their immediate target (regional stability) in ways that that are inconsistent with their interests in the region. The Middle East system remains one of the most volatile regions of the world in spite of the repeated American intervention in its affairs. On the other hand, the problems that the United States faces in the region have not lessened as a result of its recurring intervention; indeed, they may well have grown worse. In this thesis I seek reasonable explanations for this phenomenon. Using a qualitative variant of complexity theory this dissertation introduces the concept of 'dynamic stability' as an alternative to the traditional version of the term which I referred to as 'simple stability'. A detailed historical account is employed to explore different strategies pursued by U.S. administrations to achieve stability in the Middle East. These strategies include: (1) the status quo strategy, (2) the hegemony strategy, and (3) the surrogate strategy. Different model(s) of intervention grew out of each strategy. Pre-emptive/post-hoc models of intervention grew out of status quo strategy. The regime change model of intervention grew out of hegemony strategy, and the pro-Israel model of intervention grew out of the surrogate strategy. The unifying factor among these strategies, I argue, is their lack of complexity; all these strategies include a simplistic perception of stability based on imposing some fixed arrangements on Middle East system through despotic allies; military invasion or regional surrogate, respectively, while ignoring or at best under-estimating the ability of sub-state actors to dynamically self-stabilize through bottom-up/emergent free local interactions
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Grenier, Sylvain. "Stabilization Strategies of the Lumbar Spine in Vivo." Thesis, University of Waterloo, 2002. http://hdl.handle.net/10012/727.
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In developing a method of quantifying stability in the lumbar spine Cholewicki and McGill (1996) have also broached the notion of sufficient stability, where too much stiffness (and stability) would hinder motion. Thus people highly skilled at maintaining stability may use different and optimal strategies, where sufficient stability is maintained. The purpose of this work was to explore the contributors to sufficient stability, how they coordinate and relate to injury mechanisms. This work represents a cascade of investigations where. 1) To explore the balance of various sources of stiffness and their effect on the critical load and post-buckling behaviour, simulations were undertaken where the buckled configuration of the spine was predicted and its stability in this new configuration was assessed. 2) The various sources of stiffness contributing to stability in the lumbar spine have been in some cases found to be deficient. The question of how these deficiencies place individuals at risk of instability, if at all, remains unresolved. A challenged breathing task was used to determine if there was a difference in stabilizing potential between healthy individuals and low back pain sufferers. Given that differences in stabilizing potential are apparent, several tasks which included a predetermined motor strategy, such as 3)pressurizing the abdomen and 4) abdominal hollowing vs. muscle bracing, were evaluated to determine if individuals can utilize motor strategies to augment stability. The stabilizing potential of abdominal pressure (IAP) and its interaction with muscle activation was evaluated. Some individuals are more skilled at stabilizing their lumbar spine than others. Some consciously controlled motor strategies are better stabilizers than others. These strategies highlight the relative contributions of various components (posture, passive tissue, muscle activation, and load) in that no single muscle dominates stability and IAP appears to augment stability beyond muscle activation alone. The margin of safety is considerable and depends on the task at hand, but it is possible to speculate on which tissues are at greatest risk of injury.
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Moraes, Renato. "Determinants And Strategies For The Alternate Foot Placement." Thesis, University of Waterloo, 2005. http://hdl.handle.net/10012/724.
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Undesirable landing area (e. g. , a hole, a fragment of glass, a water puddle, etc) creates the necessity for an alternate foot placement planning and execution. Previous study has proposed that three determinants are used by the central nervous system (CNS) for planning an alternate foot placement: minimum foot displacement, stability and maintenance of forward progression. However, validation of these determinants is lacking. Therefore, the general purpose of the series of studies presented here is to validate and test the generality of the decision algorithm of alternate foot placement selection developed previously. The first study was designed to validate the use of a virtual planar obstacle paradigm and the economy assumption behind minimum foot displacement determinant. Participants performed two blocks of trials. In one block, they were instructed to avoid stepping in a virtual planar obstacle projected in the screen of a LCD monitor embedded in the ground. In another block, they were instructed to avoid stepping in a real hole present in walkway. Behavioral response was unaffected by the presence of a real hole. In addition, it was suggested that minimum foot displacement results in minimum changes in EMG activity which validates the economy determinant. The second study was proposed to validate the stability determinant. Participants performed an avoidance task under two conditions: free and forced. In the free condition participants freely chose where to land in order to avoid stepping in a virtual obstacle. In the forced condition, a green arrow was projected over the obstacle indicating the direction of the alternate foot placement. The data from the free condition was used to determine the preferred alternate foot placement whereas the data from the forced condition was used to assess whole body stability. It was found that long and lateral foot placements are preferred because they result in a more stable behavior. The third study was designed to validate the alternate foot placement model in a more complex terrain. Participants were required to avoid stepping in two virtual planar obstacles placed in sequence. It was found that participants used the strategy of planning the avoidance movement globally and additional determinants were used. One of the additional determinants was implementation feasibility. In the third study, gaze behavior was also monitored and two behaviors emerged from this data. One sub-group of participants fixated on the area stepped during adaptive step, whereas another sub-group anchor their gaze in a spot ahead of the area-to-be avoided and used peripheral vision for controlling foot landing. In summary, this thesis validates the three determinants for the alternate foot placement planning model and extends the previous model to more complex terrains.
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Adekoya, Wilmot Nah. "Exploring Ghana's Strategies for Stability:Lessons for Postwar Reconstruction." ScholarWorks, 2016. https://scholarworks.waldenu.edu/dissertations/2512.
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Between 1990 and 2005, the state of affairs in parts of Sub-Saharan Africa, including Liberia, remained fragile due to continuous civil unrest and war. Although peace initiatives were initiated, progress toward peace has remained minimal. Ghana, one of the nations in Sub-Saharan Africa, has continued to demonstrate significant stability and progress in the midst of civil and political conflicts in the sub-region. Currently, little research exists on how Ghanaians managed to remain stable, while countries in the sub-region continued to experience civil unrests and wars. Using Eisenstadt's theory of sociological modernization as the theoretical foundation, the purpose of this holistic case study sought to understand factors that have driven stability in Ghana. Data were collected from multiple sources including 15 research participants of diverse professions and perspectives, numerous pertinent documents, and field notes. All data were inductively coded and then subjected to a thematic analysis procedure. Social change lessons extracted from the study linked to core findings include (a) Ghanaians demonstrate an understanding of the importance of both African and Western cultural experiences and integrating the experiences from both cultural sectors for national harmony, and (b) Ghanaians are pursuing a national development agenda through economic reforms, participatory democracy, and some level of equal distribution of the national wealth. The effectiveness of Ghana's national development agenda is demonstrated by capacity building and the strengthening of social service programs not just in the urban sector, but also in the rural sector of Ghanaian society. These two core social change lessons could remain useful for countries in Sub-Saharan Africa.
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COZZI, ARIANNA CECILIA. "Technological strategies and pharmacoeconomic remarks in the prevention of photoinduced damages: product stability, efficacy and safety." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1251367.
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COZZI, ARIANNA CECILIA. "Technological strategies and pharmacoeconomic remarks in the prevention of photoinduced damages: product stability, efficacy and safety." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1251387.
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COZZI, ARIANNA CECILIA. "Technological strategies and pharmacoeconomic remarks in the prevention of photoinduced damages: product stability, efficacy and safety." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1251407.
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Loconsolo, Michael E. "Exporting the Colombian "model": comparing law enforcement strategies towards security and stability operations in Colombia and México." Thesis, Monterey, California: Naval Postgraduate School, 2014. http://hdl.handle.net/10945/42676.
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Approved for public release; distribution is unlimitedThe increase in violence involving transnational organized crime syndicates in various parts of México in the twenty-first century is widely viewed as a challenge to security and stability. Some observers have drawn comparisons with the well documented conflict in Colombia in the 1980s and 1990s between the Colombian government and the Medellín and Cali cartels. Various factors, including the professionalization of the Colombian National Police, are viewed as a model for improving the effectiveness of law enforcement elsewhere. This thesis asks whether a Colombian law enforcement model can be codified, in terms of key attributes, to improve security and stability in México. To this end, I explore Colombia’s law enforcement strategy in the 1980s and 1990s and identify shifts in strategy that might also apply to the current struggle in México. At the same time, I identify aspects of the Colombian model that have little or no relevance to contemporary México. I argue that the Colombian model can do little to reduce or eliminate the production and transportation of illegal narcotics by México-based organized crime syndicates; however, a hybrid version of the Colombian model could help reduce the overall power of the cartels and enhance security and stability throughout México.
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Beesley, Leah. "Environmental stability : its role in structuring fish communities and life history strategies in the Fortescue River, Western Australia /." Connect to this title, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0129.
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Morazzani, Ivette Marie. "Investigation of Standing Up Strategies and Considerations for Gait Planning for a Novel Three-Legged Mobile Robot." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/32319.
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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 STriDERâ s gait. Several considerations for gait planning as the robot takes a step are investigated, including: stability, dynamics, the bodyâ 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
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Hilbun, Allison Leich. "Strategies of Balancing: Regulation of Posture as a Complex Phenomenon." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etd/3014.
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The complexity of the interface between the muscular system and the nervous system is still elusive. We investigated how the neuromuscular system functions and how it is influenced by various perturbations. Postural stability was selected as the model system, because this system provides complex output, which could indicate underlying mechanisms and feedback loops of the neuromuscular system. We hypothesized that aging, physical pain, and mental and physical perturbations affect balancing strategy, and based on these observations, we constructed a model that simulates many aspects of the neuromuscular system. Our results show that aging changes the control strategy of balancing from more chaotic to more repetitive. The chaotic elements ensure quick reactions and strong capacity to compensate for the perturbations; this adeptly reactive state changes into a less reactive, slower, probably less mechanically costly balancing strategy. Mental tasks during balancing also decreased the chaotic elements in balancing strategy, especially if the subject experienced chronic pain. Additional motoric tasks, such as tying knots while balancing, were correlated with age but unaffected by chronic pain. Our model competently predicted the experimental findings, and we proceeded to use the model with an external data set from Physionet to predict the balancing strategy of Parkinson’s patients. Our neurological model, comprised of RLC circuits, provides a mechanistic explanation for the neuromuscular system adaptations.
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Zamparini, Fausto <1988>. "Peri-Implant And Periapical Oral Bone Defects: Clinical Strategies To Achieve Alveolar Bone Stability And Experimental Bone Regeneration Procedures." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amsdottorato.unibo.it/9102/1/Tesi%20Zamparini%20revised%206.11.19.pdf.
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Peri implant and periapical bone defects are widespread in the world population. Considering the high number of implant placement and root canal treatment performed every year, resolution of these bone defects will be of predominant interest in the next future.
The present project has several aims:
The first part of the project aimed to investigate how and what factors affect peri implant bone remodeling process. Microchemical analysis of the peri implant bone interface of retrieved human dental implants was performed. In addition, prospective clinical studies were conducted to evaluate the factors mostly related to peri implant bone loss.
The second part of the project aimed to evaluate chemical physical and micromorphological properties of hydraulic calcium silicates based materials (CaSi), which gained a particular attention in the endodontic field. Use of these materials claimed to resolve several complex endodontic complications, however few information is present in literature. These materials were compared with some “gold standard” bioinert materials.
Given the attractive biointeractive properties of CaSi based materials, the last part of the study will focus on the design and characterization of new mineral based scaffolds, aimed to be applied in future bone regeneration procedures. Scaffolds, composed of a polymeric matrix were doped with CaSi and calcium phosphates, in order to increase the materials biointeractive properties. A complete characterization of their chemical-physical-mechanical-thermal properties was performed, as well as the evaluation of apatite forming ability (bioactivity) and biocompatibility of these mineral based scaffolds. The combination of Human Periapical-cysts Mesenchymal Stem Cells (hPC-MSC) as a potential strategy to achieve periapical bone regeneration was evaluated. Finally, the angiogenesis potential of these scaffolds was investigated through the growth and proliferation of porcine vascular wall mesenchymal stem cells (pvw-MSC) was performed.
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Javdekar, Chitra N. "Measurement selection and parameter estimation strategies for structural stiffness and mass updating using non-destructive test data /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2004.
Find full textAbstract:
Thesis (Ph.D.)--Tufts University, 2004.Adviser: Masoud Sanayei. Submitted to the Dept. of Civil Engineering. Includes bibliographical references (leaves 300-305). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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Musa, Aysar [Verfasser], Antonello [Akademischer Betreuer] Monti, and Albert [Akademischer Betreuer] Moser. "Advanced control strategies for stability enhancement of future hybrid AC/DC networks / Aysar A. Aydan Musa ; Antonello Monti, Albert Moser." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1210929228/34.
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Flaxman, Teresa. "Neuromuscular Strategies for Regulating Knee Joint Moments in Healthy and Injured Populations." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36102.
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Background: Joint stability has been experimentally and clinically linked to mechanisms of knee injury and joint degeneration. The only dynamic, and perhaps most important, regulators of knee joint stability are contributions from muscular contractions. In participants with unstable knees, such as anterior cruciate ligament (ACL) injured, a range of neuromuscular adaptations has been observed including quadriceps weakness and increased co-activation of adjacent musculature. This co-activation is seen as a compensation strategy to increase joint stability. In fact, despite increased co-activation, instability persists and it remains unknown whether observed adaptations are the result of injury induced quadriceps weakness or the mechanical instability itself. Furthermore, there exists conflicting evidence on how and which of the neuromuscular adaptations actually improve and/or reduce knee joint stability.
Purpose: The overall aim of this thesis is therefore to elucidate the role of injury and muscle weakness on muscular contributions to knee joint stability by addressing two main objectives: (1) to further our understanding of individual muscle contribution to internal knee joint moments; and (2) to investigate neuromuscular adaptations, and their effects on knee joint moments, caused by either ACL injury and experimental voluntary quadriceps inhibition (induced by pain).
Methods: The relationship between individual muscle activation and internal net joint moments was quantified using partial least squares regression models. To limit the biomechanical contributions to force production, surface electromyography (EMG) and kinetic data was elicited during a weight-bearing isometric force matching task.
A cross-sectional study design determined differences in individual EMG-moment relationships between ACL deficient and healthy controls (CON) groups. A crossover placebo controlled study design determined these differences in healthy participants with and without induced quadriceps muscle pain. Injections of hypertonic saline (5.8%) to the vastus medialis induced muscle pain. Isotonic saline (0.9%) acted as control. Effect of muscle pain on muscle synergies recruited for the force matching task, lunging and squatting tasks was also evaluated. Synergies were extracted using a concatenated non-negative matrix factorization framework.
Results/Discussion: In CON, significant relationships of the rectus femoris and tensor fascia latae to knee extension and hip flexion; hamstrings to hip extension and knee flexion; and gastrocnemius and hamstrings to knee rotation were identified. Vastii activation was independent of moment generation, suggesting mono-articular vastii activate to produce compressive forces, essentially bracing the knee, so that bi-articular muscles crossing the hip can generate moments for the purpose of sagittal plane movement. Hip ab/adductor muscles modulate frontal plane moments, while hamstrings and gastrocnemius support the knee against externally applied rotational moments.
Compared to CON, ACL had 1) stronger relationships between rectus femoris and knee extension, semitendinosus and knee flexion, and gastrocnemius and knee flexion moments; and 2) weaker relationships between biceps femoris and knee flexion, gastrocnemius and external knee rotation, and gluteus medius and hip abduction moments. Since the knee injury mechanism, is associated with shallow knee flexion angles, valgus alignment and rotation, adaptations after ACL injury are suggested to improve sagittal plane stability, but reduce frontal and rotational plane stability. During muscle pain, EMG-moment relationships of 1) semitendinosus and knee flexor moments were stronger compared to no pain, while 2) rectus femoris and tensor fascia latae to knee extension moments and 3) semitendinosus and lateral gastrocnemius to knee internal rotation moments were reduced. Results support the theory that adaptations to quadriceps pain reduces knee extensor demand to protect the joint and prevent further pain; however, changes in non-painful muscles reduce rotational plane stability.
Individual muscle synergies were identified for each moment type: flexion and extension moments were respectively accompanied by dominant hamstring and quadriceps muscle synergies while co-activation was observed in muscle synergies associated with abduction and rotational moments. Effect of muscle pain was not evident on muscle synergies recruited for the force matching task. This may be due to low loading demands and/or a subject-specific redistribution of muscle activation. Similarly, muscle pain did not affect synergy composition in lunging and squatting tasks. Rather, activation of the extensor dominant muscle synergy and knee joint dynamics were reduced, supporting the notion that adaptive response to pain is to reduce the load and risk of further pain and/or injury.
Conclusion: This thesis evaluated the interrelationship between muscle activation and internal joint moments and the effect of ACL injury and muscle pain on this relationship. Findings indicate muscle activation is not always dependent on its anatomical orientation as previous works suggest, but rather on its role in maintaining knee joint stability especially in the frontal and transverse loading planes. In tasks that are dominated by sagittal plane loads, hamstring and quadriceps will differentially activate. However, when the knee is required to resist externally applied rotational and abduction loads, strategies of global co-activation were identified. Contributions from muscles crossing the knee for supporting against knee adduction loads were not apparent. Alternatively hip abductors were deemed more important regulators of knee abduction loads.
Both muscle pain and ACL groups demonstrated changes in muscle activation that reduced rotational stability. Since frontal plane EMG-moment changes were not present during muscle pain, reduced relationships between hip muscles and abduction moments may be chronic adaptions by ACL that facilitate instability. Findings provide valuable insight into the roles muscles play in maintaining knee joint stability. Rehabilitative/ preventative exercise interventions should focus on neuromuscular training during tasks that elicit rotational and frontal loads (i.e. side cuts, pivoting maneuvers) as well as maintaining hamstring balance, hip abductor and plantarflexor muscle strength in populations with knee pathologies and quadriceps muscle weakness.
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Sinitski, Emily H. "Transtibial Amputee and Able-bodied Walking Strategies for Maintaining Stable Gait in a Multi-terrain Virtual Environment." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31515.
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The CAREN-Extended system is a fully immersive virtual environment (VE) that can provide stability-challenging scenarios in a safe, controlled manner. Understanding gait biomechanics when stability is challenged is required when developing quantifiable metrics for rehabilitation assessment.
The first objective of this thesis was to examine the VE’s technical aspects to ensure data validity and to design a stability-challenging VE scenario. The second and third objectives examined walking speed changes and kinematic strategies when stability was challenged for able-bodied and unilateral transtibial amputees.
The results from this thesis demonstrated: 1) understanding VE operating characteristics are important to ensure data validity and to effectively design virtual scenarios; 2) self-paced treadmill mode for VEs with multiple movement scenarios may elicit more natural gait; 3) gait variability and trunk motion measures are useful when quantitatively assessing stability performance for people with transtibial amputations.
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Nemaranzhe, Lutendo. "A mathematical modeling of optimal vaccination strategies in epidemiology." University of the Western Cape, 2010. http://hdl.handle.net/11394/3065.
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Magister Scientiae - MScWe review a number of compartmental models in epidemiology which leads to a nonlinear system of ordinary differential equations. We focus an SIR, SEIR and SIS epidemic models with and without vaccination. A threshold parameter R0 is identified which governs the spread of diseases, and this parameter is known as the basic reproductive number. The models have at least two equilibria, an endemic equilibrium and the disease-free equilibrium. We demonstrate that the disease will die out, if the basic reproductive number R0 < 1. This is the case of a disease-free state, with no infection in the population. Otherwise the disease may become endemic if the basic reproductive number R0 is bigger than unity. Furthermore, stability analysis for both endemic and disease-free steady states are investigated and we also give some numerical simulations. The second part of this dissertation deals with optimal vaccination strategy in epidemiology. We use optimal control technique on vaccination to minimize the impact of the disease. Hereby we mean minimizing the spread of the disease in the population, while also minimizing the effort on vaccination roll-out. We do this optimization for the cases of SIR and SEIR models, and show how optimal strategies can be obtained which minimize the damage caused by the infectious disease. Finally, we describe the numerical simulations using the fourth-order Runge-Kutta method. These are the most useful references: [G. Zaman, Y.H Kang, II. H. Jung. BioSystems 93, (2008), 240 − 249], [K. Hattaf, N. Yousfi. The Journal of Advanced Studies in Biology, Vol. 1(8), (2008), 383 − 390.], [Lenhart, J.T. Workman. Optimal Control and Applied to Biological Models. Chapman and Hall/CRC, (2007).], [P. Van den Driessche, J. Watmough. Math. Biosci., 7, (2005)], and [J. Wu, G. R¨ost. Mathematical Biosciences and Engineering, Vol 5(2), (2008), 389 − 391].
South Africa
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Rosso, Roberto [Verfasser], Marco [Akademischer Betreuer] Liserre, Andreas [Gutachter] Lindemann, and Christian [Gutachter] Rehtanz. "Stability Analysis of Converter Control Strategies for Power Electronics-Dominated Power Systems / Roberto Rosso ; Gutachter: Andreas Lindemann, Christian Rehtanz ; Betreuer: Marco Liserre." Kiel : Universitätsbibliothek Kiel, 2020. http://nbn-resolving.de/urn:nbn:de:gbv:8:3-2021-00603-4.
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Khabou, Amal. "Dense matrix computations : communication cost and numerical stability." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00833356.
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Cette thèse traite d'une routine d'algèbre linéaire largement utilisée pour la résolution des systèmes li- néaires, il s'agit de la factorisation LU. Habituellement, pour calculer une telle décomposition, on utilise l'élimination de Gauss avec pivotage partiel (GEPP). La stabilité numérique de l'élimination de Gauss avec pivotage partiel est caractérisée par un facteur de croissance qui est reste assez petit en pratique. Toutefois, la version parallèle de cet algorithme ne permet pas d'atteindre les bornes inférieures qui ca- ractérisent le coût de communication pour un algorithme donné. En effet, la factorisation d'un bloc de colonnes constitue un goulot d'étranglement en termes de communication. Pour remédier à ce problème, Grigori et al [60] ont développé une factorisation LU qui minimise la communication(CALU) au prix de quelques calculs redondants. En théorie la borne supérieure du facteur de croissance de CALU est plus grande que celle de l'élimination de Gauss avec pivotage partiel, cependant CALU est stable en pratique. Pour améliorer la borne supérieure du facteur de croissance, nous étudions une nouvelle stra- tégie de pivotage utilisant la factorisation QR avec forte révélation de rang. Ainsi nous développons un nouvel algorithme pour la factorisation LU par blocs. La borne supérieure du facteur de croissance de cet algorithme est plus petite que celle de l'élimination de Gauss avec pivotage partiel. Cette stratégie de pivotage est ensuite combinée avec le pivotage basé sur un tournoi pour produire une factorisation LU qui minimise la communication et qui est plus stable que CALU. Pour les systèmes hiérarchiques, plusieurs niveaux de parallélisme sont disponibles. Cependant, aucune des méthodes précédemment ci- tées n'exploite pleinement ces ressources. Nous proposons et étudions alors deux algorithmes récursifs qui utilisent les mêmes principes que CALU mais qui sont plus appropriés pour des architectures à plu- sieurs niveaux de parallélisme. Pour analyser d'une façon précise et réaliste
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Guppy, Stuart N. "The stability of different methods of assessing maximal strength in the deadlift: Implications for the use of velocity-based assessment and programming strategies." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2023. https://ro.ecu.edu.au/theses/2674.
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Traditionally, the training loads implemented during resistance training have been prescribed as a percentage of the athlete’s known maximum strength. Recently however, some researchers have suggested that due to variations in the athlete’s strength levels and overall readiness to train on a day-to-day basis, these traditional methods are no longer fit for purpose. As such, autoregulatory programming strategies have been suggested as an alternative as they account for changes in the athlete’s training status and may provide a more optimised training stimulus. An increasingly popular series of autoregulatory programming strategies used by strength and conditioning professionals to modulate both training load and training volume are those that fall under the umbrella term of “Velocity-Based Training”, which are based on an objective measure of the barbell velocity during each repetition of resistance exercise the athlete performs. As such, this thesis was designed to investigate the changes in deadlift strength that occur on a dayto- day basis over a five day microcycle, along with the viability of one method of constructing a load-velocity profile and the accuracy of a novel velocity measurement device.
The primary finding of this thesis is that maximum strength during the deadlift is relatively stable between days when assessed repeatedly as either a 3RM or a 6RM (Study One and Study Four). Moreover, low to moderate volume repetition maximum strength testing does not appear to negatively impact vertical jump performance or preparedness when assessed repeatedly over the typical duration of a training microcycle. Barbell velocity however did vary between sessions in response to the maximum strength testing protocols and did not align with any changes in actual performance outcomes. In Study Three, the agreement between the velocity at 1RM and the velocity during the last repetition of a low-volume set of deadlifts were compared to determine if they could be used interchangeably when constructing a load-velocity profile. Furthermore, a novel laser-optic device designed to monitor barbell velocity during resistance exercise did not agree with a criterion measure of 3D motion capture or a common portable linear position transducer and therefore should not be used interchangeably with either device (Study Three). Finally, the velocity during 1RM did not agree with the velocity during the last repetition of the 3RM test and should not be used interchangeably when constructing a load-velocity profile for the purpose of estimating lower-body maximum strength.
Taken collectively, lower-body maximum strength does not appear to substantially vary from day to day and as such traditional methods of prescribing training loads are likely still viable. Moreover, repeated maximum strength testing is not sufficiently fatiguing to impact countermovement jump performance or rating of perceived exertion but does detrimentally impact barbell velocity during subsequent sessions. This would suggest that the use of barbell velocity to accurately monitor changes in preparedness is a less viable strategy than originally thought as these changes do not align with a meaningful change in performance or physical qualities. Moreover, based on the results of this thesis, velocity measurement devices likely should not be used interchangeably during the deadlift.
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Pelland, Lucie. "Control strategies for landing from a jump-down in boys 7 to 13 years of age : muscle and kinematic parameters which optimize postlanding stability." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68238.
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The purpose of the present study was to identify the muscle and kinematic parameters associated with the emergence of a skilled organization of landing from a jump in boys 7 years to 13 years of age. Jumps were videotaped (60Hz) in the right sagittal plane. The digitized coordinates of six landmarks were used to calculate the angular position, velocity, and acceleration parameters for the hip, knee, and ankle joints. Surface EMG signals were recorded for six muscles (Tibialis Anterior, Lateral Gastrocnemius, Soleus, Vastus Lateralis, Rectus Femoris, Biceps Femoris) to obtain the pattern of muscle onsets in anticipation for landing and the modulation of the muscle activity during the impact phase.Subjects could be classified into three distinct groups based on the pattern of muscle onsets: the Proximal-distal group (PDS), the Transitional group (TS), and the Adult group (AS). The classification reflected a progression from a proximal-distal (PDS) to a distal-proximal (AS) organization of landing. At the muscular level, the progression was associated with: (1) an increased contribution of the ankle to the anticipatory control of landing; and (2) the modulation of muscle activity to reduce the impact ground reaction forces. The strongest kinematic correlates were associated with the increased ability: (1) to manage and organize motion-dependent torques; (2) to critically modulate the joint position in anticipation of landing, and (3) to utilize anticipatory muscle activity rather than biomechanical joint limits to manage the impact ground reaction forces.
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Shannon-Little, Paul Anthony. "Balancing risks and stability on a multicultural campus : the roles and strategies of long-stay international students in achieving study success and inter-cultural competence." Thesis, University of Bristol, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.559490.
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The experience of studying on a multicultural campus is regarded as a highly potent means of developing intercultural skills. However many studies report that authentic interaction between domestic and incoming students is often disappointingly absent. Through interviews this study investigates the experiences of long-stay international students at a British university who have been relatively successful in developing cross- cultural relations. An analysis is carried out of their descriptions of contacts with other cultures and the resulting effects in four areas: their attitudes and behaviour in negotiating cross-cultural interaction, the strategies they adopted to ease their adjustment to the new environment and to reflect on their culture of origin, their levels of success in adopting roles which allowed them to contribute to culturally mixed collectives, and their expectations and motivations to apply what they have learned to future interactions. To locate their responses within a theoretical framework, I have drawn loosely on Lave & Wenger's community of practice conception of learning in a professional context and related it to peer-group formation within study cohorts. The roles interviewees assumed acknowledged their reliance on others' support, but also allowed them to contribute in other ways to the collective. In Wenger's terms many describe a shift over time from legitimate peripheral participation towards core membership. Expectations of future approaches towards intercultural contact and transferability of skills, attitudes and knowledge showed a wide degree of variation, depending on what Wenger terms their trajectories: previous experience, current attitudes and future plans. Five distinct types of trajectory were identified from the interview data. A discussion follows, of ways in which knowledge of these various attitudes, strategies., roles and trajectories can be used to inform the activities of staff in Higher Education wishing to improve and accelerate the quality and reflexivity of students' multicultural experiences.
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Kangas, J. (Jani). "Separation process modelling:highlighting the predictive capabilities of the models and the robustness of the solving strategies." Doctoral thesis, Oulun yliopisto, 2014. http://urn.fi/urn:isbn:9789526203768.
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Abstract The aim of this work was to formulate separation process models with both predictive capabilities and robust solution strategies. Although all separation process models should have predictive capabilities, the current literature still has multiple applications in which predictive models having the combination of a clear phenomenon base and robust solving strategy are not available. The separation process models investigated in this work were liquid-liquid phase separation and membrane separation models. The robust solving of a liquid-liquid phase separation model typically demands the solution of a phase stability analysis problem. In addition, predicting the liquid-liquid phase compositions reliably depends on robust phase stability analysis. A phase stability analysis problem has multiple feasible solutions, all of which have to be sought to ensure both the robust solving of the model and predictive process model. Finding all the solutions with a local solving method is difficult and generally inexact. Therefore, the modified bounded homotopy methods, a global solving method, were further developed to solve the problem robustly. Robust solving demanded the application of both variables and homotopy parameter bounding features and the usage of the trivial solution in the solving strategy. This was shown in multiple liquid-liquid equilibrium cases. In the context of membrane separation models, predictive capabilities are achieved with the application of a Maxwell-Stefan based model. With the Maxwell-Stefan approach, multicomponent separation can be predicted based on pure component permeation data alone. On the other hand, the solving of the model demands a robust solving strategy with application-dependent knowledge. These issues were illustrated in the separation of a H2/CO2 mixture with a high-silica MFI zeolite membrane at high pressure and low temperature. Similarly, the prediction of mixture adsorption based on pure component adsorption data alone was successfully demonstrated. In the context of membrane separation models, predictive capabilities are achieved with the application of a Maxwell-Stefan based model. With the Maxwell-Stefan approach, multicomponent separation can be predicted based on pure component permeation data alone. On the other hand, the solving of the model demands a robust solving strategy with application-dependent knowledge. These issues were illustrated in the separation of a H2/CO2 mixture with a high-silica MFI zeolite membrane at high pressure and low temperature. Similarly, the prediction of mixture adsorption based on pure component adsorption data alone was successfully demonstratedTiivistelmä Työn tavoitteena oli muotoilla prosessin käyttäytymisen ennustamiseen kykeneviä erotusprosessimalleja ja niiden ratkaisuun käytettäviä luotettavia strategioita. Vaikka kaikkien erotusprosessimallien tulisi olla ennustavia, on tällä hetkellä useita kohteita, joissa prosessin käyttäytymistä ei voida ennustaa siten, että käytettävissä olisi sekä ilmiöpohjainen malli että ratkaisuun soveltuva luotettava strategia. Tässä työssä erotusprosessimalleista kohteina tarkasteltiin neste-neste-erotuksen ja membraanierotuksen kuvaukseen käytettäviä malleja. Neste-neste-erotusmallien luotettava ratkaisu vaatii yleensä faasistabiilisuusongelman ratkaisua. Lisäksi faasien koostumusten luotettava ennustaminen pohjautuu faasistabiilisuusanalyysiin. Faasistabiilisuusongelmalla on useita mahdollisia ratkaisuja, jotka kaikki tulee löytää, jotta voitaisiin varmistaa luotettava mallin ratkaisu sekä prosessimallin ennustuskyvyn säilyminen. Kaikkien ratkaisujen löytäminen on sekä vaikeaa että epätarkkaa paikallisesti konvergoituvilla ratkaisumenetelmillä. Tämän vuoksi globaaleihin ratkaisumenetelmiin kuuluvia modifioituja rajoitettuja homotopiamenetelmiä kehitettiin edelleen, jotta faasistabiilisuusongelma saataisiin ratkaistua luotettavasti. Ratkaisun luotettavuus vaati sekä muuttujien että homotopiaparametrin rajoittamista ja ongelman triviaalin ratkaisun käyttöä ratkaisustrategiassa. Tämä käyttäytyminen todennettiin useissa neste-nestetasa-painoa kuvaavissa esimerkeissä. Membraanierotusta tarkasteltaessa ennustava malli voidaan muotoilla käyttämällä Maxwell-Stefan pohjaista mallia. Maxwell-Stefan lähestymistavalla voidaan ennustaa monikomponenttiseosten erotusta perustuen puhtaiden komponenttien membraanin läpäisystä saatuun mittausaineistoon. Toisaalta mallin ratkaisu vaatii luotettavan ratkaisustrategian, jossa hyötykäytetään kohteesta riippuvaa tietoa. Näitä kysymyksiä havainnollistettiin H2/CO2 seoksen erotuksessa MFI-zeoliitti-membraanilla korkeassa paineessa. Samoin seosten adsorboitumiskäyttäytymistä ennustettiin onnistuneesti pelkästään puhtaiden komponenttien adsorptiodatan pohjalta. Kokonaisuutena voidaan todeta, että tarkasteltujen erotusprosessimallien ennustavuutta voidaan parantaa yhdistämällä malli, jolla on selkeä ilmiöpohja ja luotettava ratkaisustrategia. Lisäksi mallien käytettävyys erotusprosessien suunnittelussa on parantunut työn tulosten pohjalta
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Casali, Lucia <1993>. "Crystal engineering strategies for a healthier environment: solid-state syntheses and characterization of organic/inorganic co-crystals and host-guest systems with improved stability and performance activities." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/9804/1/PhD_Dissertation_Casali_Final.pdf.
Full textAbstract:
In a society increasingly aware of and concerned about environmental issues, chemistry is being asked to promote sustainability through the development of processes less impacting on the environment and of products environmentally friendly. In this context, the field of chemistry referred as crystal engineering can play a major role in the quest for sustainability. By exploiting sustainable synthetic methodologies - first of all the mechanochemical method - crystal engineering can guide solid-state modifications in order to obtain crystalline materials with an improved sustainable character.
This doctoral research activity addressed the synthesis and characterization of environmentally friendly crystalline materials. Two different lines of research were undertaken:
• Optimization of materials of agrochemical interest, mainly through the co-crystallization method.
The first systems investigated were urea-based co-crystals, designed (i) to improve the chemical-physical properties of urea by reducing its water solubility/dissolution rate and (ii) to exert an inhibition activity towards the soil enzymes urease and ammonia monooxygenase (AMO). The work resulted in the publication of three papers, which are presented in Chapter 2.
A further development of this research project concerned the synthesis and characterization of crystalline materials based on AMO inhibitors, aimed to modulate the physico-chemical properties of such inhibitors in terms of water solubility, thermal stability, and inhibition activity. The experiments discussed in Chapter 3 are quite promising: a paper has been submitted upon invitation, and two more manuscripts are in preparation.
• Improvement in the photostability of organic UV filters commonly used in sunscreen formulations through their inclusion into β-cyclodextrin.
The inclusion complexes of β-cyclodextrin with the UV filters avobenzone and octinoxate were synthesized and proved to possess the desired properties. The results led to the publication of a paper, which is presented in Chapter 4.
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Salehi, Pour Mehr Vahid. "Development and Verification of Control and Protection Strategies in Hybrid AC/DC Power Systems for Smart Grid Applications." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/804.
Full textAbstract:
Modern power networks incorporate communications and information technology infrastructure into the electrical power system to create a smart grid in terms of control and operation. The smart grid enables real-time communication and control between consumers and utility companies allowing suppliers to optimize energy usage based on price preference and system technical issues. The smart grid design aims to provide overall power system monitoring, create protection and control strategies to maintain system performance, stability and security.
This dissertation contributed to the development of a unique and novel smart grid test-bed laboratory with integrated monitoring, protection and control systems. This test-bed was used as a platform to test the smart grid operational ideas developed here. The implementation of this system in the real-time software creates an environment for studying, implementing and verifying novel control and protection schemes developed in this dissertation. Phasor measurement techniques were developed using the available Data Acquisition (DAQ) devices in order to monitor all points in the power system in real time. This provides a practical view of system parameter changes, system abnormal conditions and its stability and security information system. These developments provide valuable measurements for technical power system operators in the energy control centers. Phasor Measurement technology is an excellent solution for improving system planning, operation and energy trading in addition to enabling advanced applications in Wide Area Monitoring, Protection and Control (WAMPAC).
Moreover, a virtual protection system was developed and implemented in the smart grid laboratory with integrated functionality for wide area applications. Experiments and procedures were developed in the system in order to detect the system abnormal conditions and apply proper remedies to heal the system.
A design for DC microgrid was developed to integrate it to the AC system with appropriate control capability. This system represents realistic hybrid AC/DC microgrids connectivity to the AC side to study the use of such architecture in system operation to help remedy system abnormal conditions.
In addition, this dissertation explored the challenges and feasibility of the implementation of real-time system analysis features in order to monitor the system security and stability measures. These indices are measured experimentally during the operation of the developed hybrid AC/DC microgrids. Furthermore, a real-time optimal power flow system was implemented to optimally manage the power sharing between AC generators and DC side resources.
A study relating to real-time energy management algorithm in hybrid microgrids was performed to evaluate the effects of using energy storage resources and their use in mitigating heavy load impacts on system stability and operational security.
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Pelliccia, M. "STRATEGIES FOR ENHANCING VIRAL GENE TRANSFER AND THE THERMOSTABILITY OF VIRAL VECTORS IN VACCINE APPLICATIONS." Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/265518.
Full textAbstract:
At the most basic level viruses are biological nano-containers constituted by genetic material enclosed in a protein shell, capsid. A peculiar feature of viruses, both bacterial and some eukaryotic viruses, lies in the high packaging density of the genome in order to fit itself in the small capsid and hence the high internal osmotic pressure. Virus is a relatively stable particle equipped with fascinating mechanical properties of the capsid that are crucial for the virus lifecycle. Viruses have only one purpose: infect a host cell for reproducing themselves in order to generate new viral progeny (Roos et al. 2007). Therefore, the first and foremost consideration arising from the concept of virus reflects its pathogenesis and virulence that can ultimately result in many important infectious diseases such as common cold, influenza, hepatitis, rabies, measles, cancer and AIDS. As a consequence, pathogenic viruses represent a heavy hurdle for the global health and there is a strong need for developing robust strategies such as vaccines or antiviral drugs against virus infections (Baram- Pinto et al. 2010). On the other hand, viruses in the course of evolution have become efficient specialized gene delivery agents. Therefore they represent powerful tools in biomedicine for gene therapy and vaccine purposes (Schaffer et al. 2008). For successful gene therapy and immunization programs, the efficiency and stability of viral vectors are fundamental aspects (Jorio et al. 2006).
To address this challenge, in the present research project we have investigated the interaction between viruses and nanomaterials. In the last years materials on the nanoscale for their unique properties have provided a broad range of potential biomedical uses (Verma et al. 2008) and for that reason we decided to explore their application with viruses. More specifically, we have examined three types of sulfonate- functionalized gold nanoparticles (AuNPs), namely, MUS:OT, MUS and MUS:brOT NPs, which are less than 5 nm in size, negatively charged and poorly cytotoxic (Verma et al. 2008). The NPs are coated with self-assembled monolayer (SAM) of thiolated organic molecules and one of the ligand is a sulfonated molecule, MUS (Verma et al. 2008). The MUS ligand itself was tested in our experiments as well. As virus models we focused on human recombinant adenovirus type 5 (Ad), one of the most promising viral vector as vaccine and gene therapy carrier and two picornaviruses of the genus enterovirus, namely, EV1 and CVB3, important human pathogens associated with several infectious diseases (e.g. myocarditis, aseptic meningitis, encephalitis, paralysis)(Kossila et al. 2002)(Marjomäki et al. 2014a). In spite of their medical impact, there are no therapeutic treatments available against picornavirus infections and the only vaccine products are against three types of poliovirus and hepatitis A virus (Merilahti et al. 2012).
Two sets of experiments were carried out: (1) Short-term incubation of Ad with nanomaterials for 1 h at 37°C prior
transducing HeLa cells or before in vivo administration in zebrafish and mice. The results demonstrated that Ad shortly pre-treated with nanomaterials showed a significant increase in the gene expression in vitro and in vivo The NPs’enhanced adenovirus transduction aims to reduce Ad vector doses in vivo thereby minimizing the adverse reactions of the immune response due to high vector dosage; (2) Long-term thermostabilization studies of Ad, EV1 and CVB3 in vitro in the presence and in the absence of our nanomaterials and other substances such as sugars (sucrose, glucose, glycerol) and Polyethylene glycol (PEG) molecules at 37°C or room temperature for extensive periods of time. Our results showed the capability of the nanomaterials and sucrose to increase substantially the heat stability of the viruses. In order to elucidate the thermal inactivation mechanism of viral particles and the stabilizing effect provided by some compounds on viruses we set out to formulate an analytical theory. This line of research fits in the context of developing more thermo-stable viral vector preparations for vaccine purposes that do not require the maintenance of the challenging cold chain system in order to preserve the effectiveness of viral vaccines during the storage, shipment and administration to the patients and hence to ensure the success of global immunization programs (Alcock et al. 2010).
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Farris, Kerry David Pintel David J. "Protein processing strategies by adeno-associated virus type 5 (AAV5) and the effects of the adenovirus E4orf6/E1b-55k/Cullin 5 E3 ubiquitin ligase complex on AAV protein stability." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/6687.
Full textAbstract:
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on March 10, 2010). Vita. Thesis advisor: David Pintel "August 2008" Includes bibliographical references
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Pavlík, David. "Evoluční strategie v úloze predikce vlivu aminokyselinových mutací na stabilitu proteinu." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2014. http://www.nusl.cz/ntk/nusl-236138.
Full textAbstract:
This master's thesis deals with the matter of predicting the effects of aminoacid substitutions on protein stability. The main aim is to design meta-classifier that combines the results of the selected prediction tools. An evolution strategy was used to find the best weights for each of the selected tools with the aim of achieving better prediction performance compared to that achieved by using these tools separately. Five different and obtainable prediction tools were selected and their prediction outputs were weighted. Two different approaches of evolution strategy are investigated and compared: evolution strategy with the 1/5-rule and evolution strategy with the type 2 of control parameters self-adaptation. Two independent datasets of mutations were created for training and evaluating the performance of designed meta-classifier. The performed experiments and obtained results suggest that the evolution strategy could be considered as a~beneficial approach for prediction of protein stability changes. However, the special attention must be paid to careful selection of tools for integration and compilation of training and testing datasets.
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Kadlec, Miroslav. "Evoluční strategie v úloze predikce vlivu aminokyselinových mutací na stabilitu proteinů." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2015. http://www.nusl.cz/ntk/nusl-234926.
Full textAbstract:
This thesis is focused on predicting the impact of amino acid substitution on protein stability. The main goal is to create a consensual predictor that uses the outputs of chosen existing tools in order to improve accuracy of prediction. The optimal consensus of theese tools was designed using evolution strategies in three variants: 1/5 success rule, self-adaptation variant and the CMA-ES method. Then, the quality of calculated weight vectors was tested on the independent dataset. Although the highest prediction performance was attained by self-adaptation method, the differences between all three variants were not significant. Compared to the individual tools, the predictions provided by consensual methods were generally more accurate - the self-adaptation variant imporved the Pearson's corelation coeficient of the predictions by 0,057 on the training dataset. On the testing dataset, the improvement of designed method was smaller (0,040). Relatively low improvement of prediction performance (both on the training and the testing dataset) were caused by the fact, that for some records of testing dataset, some individual tools vere not able to provide their results. When omitting these records, consensual method improved the Pearson's corelations coeficient by 0,118.
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Srihi, Hajer. "Stratégies de stabilité en position assise chez les personnes vivant avec une lésion de la moelle épinière : de l’estimation utilisant des modèles descripteurs quasi-LPV à la validation expérimentale." Electronic Thesis or Diss., Valenciennes, Université Polytechnique Hauts-de-France, 2023. http://www.theses.fr/2023UPHF0041.
Full textAbstract:
La lésion médullaire conduit à une perte partielle ou complète de l’activité musculaire et des fonctions sensorielles en dessous du niveau lésionnel, cette atteinte de la moelle épinière entraîne une réduction drastique de la stabilité posturale en position assise et par conséquent un risque de chute élevé (Boswell-Ruys et al., 2010 ; Nelson et al., 2010).Les conséquences de la lésion médullaire sont importantes et d’ordre sensori-motrices, cardio-vasculaires, respiratoires et digestives. L’impact de la lésion sur le système stabilisateur vertébral conduit à de nouvelles stratégies de stabilisation, en cas de perturbation, qui sont différentes des stratégies mise en œuvre par les sujets asymptomatiques. Ces stratégies qui viennent compenser l’absence d'un contrôle sous-lésionnel sont basées essentiellement sur les mouvements des membres supérieurs.La compréhension de ces stratégies ainsi que la quantification des efforts articulaires qui en résultent sont nécessaires afin d’évaluer l’impact de la lésion et proposer des nouvelles techniques facilitant le maintien de la stabilité. L’un des enjeux est de savoir « retourner » vers les variables qui génèrent ces efforts, les couples articulaires, données qui ne sont pas mesurées et ne sont pas mesurables. Une manière de le faire, alternative à la « classique » dynamique inverse, a été exploitée dans les travaux précédents (Blandeau, 2018). Elle consiste, à partir d’un modèle biomécanique, à utiliser des techniques d’observation pour reconstruire ces entrées inconnues. Le formalisme utilisé est un formalisme dit de Takagi-Sugeno qui permet de décrire de façon polytopique des systèmes non linéaires. La description utilisée est de type descripteur, car elle se prête bien aux modèles mécaniques en diminuant la complexité des conditions obtenues (Estrada-Manzo, 2015).Une campagne d’essais réalisée au CRIR de Montréal (Blandeau, 2018) a permis de recueillir de nombreuses données sur la posture assise des personnes lésées médullaires. Seule une partie de ces essais a pu être exploitée car le modèle « Seated-3-segments » (S3S) utilisé ne permettait pas de décrire toutes les situations rencontrées, par exemple une dissymétrie dans les mouvements des bras.Il y a plusieurs challenges :Enrichir les modèles existants, notamment le modèle S3S (Blandeau, 2018) sachant qu’une résolution « directe » avec un observateur issu de ce type de modèle est déjà proche des limitations des solveurs actuels.Arriver à des solutions qui sont pertinentes (a minima qui utilisent les modèles biomécaniques sans simplification), compatibles avec les possibilités des solveurs et suffisamment génériques pour ne pas demander de refaire une étude complète si on ajoute des degrés de liberté supplémentaires.Dans l’esprit de ces challenges, des propositions d’observateurs non linéaires mis en cascade sont faites. Pour montrer le bien-fondé de l’approche, les résultats sont d’abord comparés à l’existant (S3S) avant d’être étendus à des modèles utilisant des degrés de liberté supplémentaires dont « Trunk-2-arms » (T2A) pour lesquels la méthodologie précédente ne peut apporter de solutions. T2A permet notamment d’exploiter des essais impliquant une dissymétrie dans les mouvements de membres supérieurs. Il reste dans les étapes suivantes à introduire les rotations, notamment au niveau des épaules pour se rapprocher des mouvements réels effectués par le sujet. La méthodologie utilisée semble parfaitement adaptée pour réaliser cette extension.Enfin, un mannequin équipé de tous les actionneurs et capteurs nécessaires permettant de reproduire les mouvements d’une personne en position assise sera utilisé avec cette fois-ci la possibilité de valider les couples articulaires reconstruits, en les comparant directement à ceux produitsSpinal cord injury leads to a partial or complete loss of muscular activity and sensory functions below the level of injury, this damage to the spinal cord leads to a drastic reduction in postural stability in a sitting position and consequently a high risk of falling (Boswell-Ruys et al., 2010; Nelson et al., 2010).The consequences of the injury are significant and are sensorimotor, cardiovascular, respiratory and digestive. The impact of the injury on the vertebral stabilizing system leads to new stabilization strategies, in case of disturbance, which are different from the strategies implemented by asymptomatic subjects. These strategies, which compensate for the lack of sublesionel control, are essentially based on the movements of the upper limbs.Understanding these strategies as well as quantifying the resulting joint forces are necessary in order to assess the impact of the injury and propose news methods facilitating the control of seated stability.One of the challenges is knowing how to ‘’return’’ to the variables that generate these efforts, the joint torques, data which are not measured and cannot be measured. A way of doing that, an alternative to the ‘’classic’’ inverse dynamics, has been exploited in previous work (Blandeau, 2018). It consists, from a biomechnical model, of using observation techniques to reconstruct these unknown inputs. The formalism used is a so-called Takagi-Sugeno formalism in order to describe nonlinear systems in a polytopic manner. The description used is of descriptor type, because it lends itself well to mechanical models by reducing the complexity of the conditions obtained (Estrada-Manzo, 2015).A test compaign carried out at the CRIR in Montreal (Blandeau, 2018) made it possible to collect numerous data on the sitting posture of people with spinal cord injuries. Only part of these tests could be analyzed because the ‘’Seated-3-Segments’’ (S3S) model used is not able to describe all the situations encountered, for example asymmetry in arm movements.There are several challenges:Enriching existing models, in particular the S3S model (Blandeau, 2018), knowing that the ‘’direct’’ resolution with an observer from this type of model is already close to the limitations of current solvers.Arrive at solutions which are relevant (at a minimum which use biomechanical models without simplification), compatible with the possibilities of the solvers and sufficiently generic so are not to require redoing a complete study if additional degrees of freedom are added. To fulfil these challenges, proposals for cascaded nonlinear observers are made. To show the merits of the approach, the results are first compared to the existing one (S3S) before being extended to models using additional degrees of freedom including ‘’Trunk-2-Arms’’ (T2A) for which the previous methodology cannot provide solutions. T2A make it possible in particular to exploit tests involving asymmetry in upper limbs movements. In the following stages, it remains to introduce rotations, particularly at the level of the shoulders to approximate the real movements carried out by the subject. The methodology used seems perfectly suited to carry out this extension.Finally, a mannequin equipped with all the necessary actuators and sensors to reproduce the movements of a person in seated position will be used, this time with the possibility of validating the reconstructed joint torques, by directly comparing them to those produced